Stimuli responsive ion gels based on polysaccharides and other polymers prepared using ionic liquids and deep eutectic solvents.

PubMed

Prasad, Kamalesh; Mondal, Dibyendu; Sharma, Mukesh; Freire, Mara G; Mukesh, Chandrakant; Bhatt, Jitkumar

2018-01-15

Ion gels and self-healing gels prepared using ionic liquids (ILs) and deep eutectic solvents (DESs) have been largely investigated in the past years due to their remarkable applications in different research areas. Herewith we provide an overview on the ILs and DESs used for the preparation of ion gels, highlight the preparation and physicochemical characteristics of stimuli responsive gel materials based on co-polymers and biopolymers, with special emphasis on polysaccharides and discuss their applications. Overall, this review summarizes the fundamentals and advances in ion gels with switchable properties prepared using ILs or DESs, as well as their potential applications in electrochemistry, in sensing devices and as drug delivery vehicles. Copyright © 2017 Elsevier Ltd. All rights reserved.

The influence of polymer molecular weight in lamellar gels based on PEG-lipids.

PubMed Central

Warriner, H E; Keller, S L; Idziak, S H; Slack, N L; Davidson, P; Zasadzinski, J A; Safinya, C R

1998-01-01

We report x-ray scattering, rheological, and freeze-fracture and polarizing microscopy studies of a liquid crystalline hydrogel called Lalpha,g. The hydrogel, found in DMPC, pentanol, water, and PEG-DMPE mixtures, differs from traditional hydrogels, which require high MW polymer, are disordered, and gel only at polymer concentrations exceeding an "overlap" concentration. In contrast, the Lalpha,g uses very low-molecular-weight polymer-lipids (1212, 2689, and 5817 g/mole), shows lamellar order, and requires a lower PEG-DMPE concentration to gel as water concentration increases. Significantly, the Lalpha,g contains fluid membranes, unlike Lbeta' gels, which gel via chain ordering. A recent model of gelation in Lalpha phases predicts that polymer-lipids both promote and stabilize defects; these defects, resisting shear in all directions, then produce elasticity. We compare our observations to this model, with particular attention to the dependence of gelation on the PEG MW used. We also use x-ray lineshape analysis of scattering from samples spanning the fluid-gel transition to obtain the elasticity coefficients kappa and B; this analysis demonstrates that although B in particular depends strongly on PEG-DMPE concentration, gelation is uncorrelated to changes in membrane elasticity. PMID:9649387

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetatexanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan gum gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar. Performance and produced polymer evaluation of four alkaline-surfactant-polymer projects concluded that only one of the projects could have benefited from combining the alkaline-surfactant-polymer and gelation technologies. Cambridge, the 1993 Daqing, Mellott Ranch, and the Wardlaw alkaline-surfacant-polymer floods were studied. An initial gel treatment followed by an alkaline-surfactant-polymer flood in the Wardlaw field would have been a benefit due to reduction of fracture flow.« less

Dual phase polymer gel electrolyte based on non-woven poly(vinylidenefluoride-co-hexafluoropropylene)–layered clay nanocomposite fibrous membranes for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shubha, Nageswaran; Prasanth, Raghavan; Energy Research Institute - NTU

2013-02-15

Graphical abstract: Display Omitted Highlights: ► P(VdF-co-HFP)–clay nanocomposite based electrospun membranes are prepared. ► The membranes are used as polymer gel electrolyte (PGE) in lithium ion batteries. ► The composite PGE shows ionic conductivity of 5.5 mS cm{sup −1} at room temperature. ► Li/PGE/LiFePO{sub 4} cell delivers initial discharge capacity of 160 mAh g{sup −1}. ► The use of prepared electrolyte significantly improved the cell performance. -- Abstract: A new approach for fabricating polymer gel electrolytes (PGEs) based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) incorporated with layered nanoclay has been employed to enhance the ionic conductivity and electrochemical properties of P(VdF-co-HFP) withoutmore » compromising its mechanical strength. The effect of layered nanoclay on properties of membranes has been evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Surface morphology of the membranes has been studied using field-emission scanning electron microscopy (FE-SEM). Polymer gel electrolytes are prepared by soaking the fibrous membrane into 1 M LiPF{sub 6} in EC/DEC. The electrochemical studies show that incorporation of layered nanoclay into the polymer matrix greatly enhanced the ionic conductivity and compatibility with lithium electrodes. The charge–discharge properties and cycling performance of Li/LiFePO{sub 4} cells comprising nanocomposite polymer gel electrolytes have been evaluated at room temperature.« less

Coupling the Alkaline-Surfactant-Polymer Technology and the Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding froin swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan guin gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar.« less

Quantitative evaluation of polymer concentration profile during swelling of hydrophilic matrix tablets using 1H NMR and MRI methods.

PubMed

Baumgartner, Sasa; Lahajnar, Gojmir; Sepe, Ana; Kristl, Julijana

2005-02-01

Many pharmaceutical tablets are based on hydrophilic polymers, which, after exposure to water, form a gel layer around the tablet that limits the dissolution and diffusion of the drug and provides a mechanism for controlled drug release. Our aim was to determine the thickness of the swollen gel layer of matrix tablets and to develop a method for calculating the polymer concentration profile across the gel layer. MR imaging has been used to investigate the in situ swelling behaviour of cellulose ether matrix tablets and NMR spectroscopy experiments were performed on homogeneous hydrogels with known polymer concentration. The MRI results show that the thickest gel layer was observed for hydroxyethylcellulose tablets, followed by definitely thinner but almost equal gel layer for hydroxypropylcellulose and hydroxypropylmethylcellulose of both molecular weights. The water proton NMR relaxation parameters were combined with the MRI data to obtain a quantitative description of the swelling process on the basis of the concentrations and mobilities of water and polymer as functions of time and distance. The different concentration profiles observed after the same swelling time are the consequence of the different polymer characteristics. The procedure developed here could be used as a general method for calculating polymer concentration profiles on other similar polymeric systems.

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-10-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or more efficient areal sweep efficiency for those with high permeability contrast ''thief zones''. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or those with thief zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. A priormore » fluid-fluid report discussed interaction of different gel chemical compositions and alkaline-surfactant-polymer solutions. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses. Aluminum-polyacrylamide, flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9. Chromium acetate-polyacrylamide flowing and rigid flowing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid flowing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid flowing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid flowing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. None of the gels tested appeared to alter alkaline-surfactant-polymer solution oil recovery. Total waterflood plus chemical flood oil recovery sequence recoveries were all similar. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate gels that were stable to injection of alkaline-surfactant-polymer solutions at 72 F were stable to injection of alkaline-surfactant-polymer solutions at 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Xanthan gum-chromium acetate gels maintained gel integrity in linear corefloods after injection of an alkaline-surfactant-polymer solution at 125 F. At 175 F, Xanthan gum-chromium acetate gels were not stable either with or without subsequent alkaline-surfactant-polymer solution injection. Numerical simulation demonstrated that reducing the permeability of a high permeability zone of a reservoir with gel improved both waterflood and alkaline-surfactant-polymer flood oil recovery. A Minnelusa reservoir with both A and B sand production was simulated. A and B sands are separated by a shale layer. A sand and B sand waterflood oil recovery was improved by 196,000 bbls when a gel was placed in the B sand. A sand and B sand alkaline-surfactant-polymer flood oil recovery was improved by 596,000 bbls when a gel was placed in the B sand. Alkaline-surfactant-polymer flood oil recovery improvement over a waterflood was 392,000 bbls. Placing a gel into the B sand prior to an alkaline-surfactant-polymer flood resulted in 989,000 bbl more oil than only water injection.« less

Selection of new Kynar-based electrolytes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Christie, Alasdair M.; Christie, Lynn; Vincent, Colin A.

New electrolyte solution compositions have been identified for use in lithium-ion batteries after gelling with an appropriate quantity of Kynar polymer. Since the Li + conducting medium is largely the liquid electrolyte component, the assessment of these solutions as suitable lithium-ion cell candidates were investigated before adding the polymer. Selected electrolyte solutions were then used in the preparation of polymer gels. The specific conductivities of Kynar-based gels were determined as a function of salt concentration and polymer concentration. Optimised self-supporting polymer films, based on mixtures of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and lithium hexafluorophosphate (LiPF 6) or lithium tetrafluoroborate (LiBF 4), showed good high current density cycling performance when used as separators in coke and Li 1- xMn 2O 4 (spinel) half-cells.

Gadolinium-loaded gel scintillators for neutron and antineutrino detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riddle, Catherine Lynn; Akers, Douglas William; Demmer, Ricky Lynn

A gadolinium (Gd) loaded scintillation gel (Gd-ScintGel) compound allows for neutron and gamma-ray detection. The unique gel scintillator encompasses some of the best features of both liquid and solid scintillators, yet without many of the disadvantages associated therewith. Preferably, the gel scintillator is a water soluble Gd-DTPA compound and water soluble fluorophores such as: CdSe/ZnS (or ZnS) quantum dot (Q-dot) nanoparticles, coumarin derivatives 7-hydroxy-4-methylcoumarin, 7-hydroxy-4-methylcoumarin-3-acetic acid, 7-hydroxycoumarin-3-carboxylic acid, and Alexa Fluor 350 as well as a carbostyril compound, carbostyril 124 in a stable water-based gel, such as methylcellulose or polyacrylamide polymers. The Gd-loaded ScintGel allows for a homogenious distribution ofmore » the Gd-DTPA and the fluorophores, and yields clean fluorescent emission peaks. A moderator, such as deuterium or a water-based clear polymer, can be incorporated in the Gd-ScintGel. The gel scintillators can be used in compact detectors, including neutron and antineutrino detectors.« less

Effect of conductive additives to gel electrolytes on activated carbon-based supercapacitors

NASA Astrophysics Data System (ADS)

Barzegar, Farshad; Dangbegnon, Julien K.; Bello, Abdulhakeem; Momodu, Damilola Y.; Johnson, A. T. Charlie; Manyala, Ncholu

2015-09-01

This article is focused on polymer based gel electrolyte due to the fact that polymers are cheap and can be used to achieve extended potential window for improved energy density of the supercapacitor devices when compared to aqueous electrolytes. Electrochemical characterization of a symmetric supercapacitor devices based on activated carbon in different polyvinyl alcohol (PVA) based gel electrolytes was carried out. The device exhibited a maximum energy density of 24 Wh kg-1 when carbon black was added to the gel electrolyte as conductive additive. The good energy density was correlated with the improved conductivity of the electrolyte medium which is favorable for fast ion transport in this relatively viscous environment. Most importantly, the device remained stable with no capacitance lost after 10,000 cycles.

Tunable emission in lanthanide coordination polymer gels based on a rationally designed blue emissive gelator.

PubMed

Sutar, Papri; Suresh, Venkata M; Maji, Tapas Kumar

2015-06-18

Rational design and synthesis of a new low molecular weight gelator (LMWG) having 9,10-diphenylanthracene core and terminal terpyridine is reported. Tb(III) and Eu(III) ion coordination to a LMWG results in green and pink emissive coordination polymer gels, respectively, with coiled nanofiber morphology. Further, control over stoichiometry of LMWG:Tb(III):Eu(III) leads to yellow and white light emitting bimetallic gels.

A Newly Designed Composite Gel Polymer Electrolyte Based on Poly(Vinylidene Fluoride-Hexafluoropropylene) (PVDF-HFP) for Enhanced Solid-State Lithium-Sulfur Batteries.

PubMed

Xia, Yan; Wang, Xiuli; Xia, Xinhui; Xu, Ruochen; Zhang, Shengzhao; Wu, Jianbo; Liang, Yanfei; Gu, Changdong; Tu, Jiangping

2017-10-26

Developing high-performance solid-state electrolytes is crucial for the innovation of next-generation lithium-sulfur batteries. Herein, a facile method for preparation of a novel gel polymer electrolyte (GPE) based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) is reported. Furthermore, Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 (LATP) nanoparticles as the active fillers are uniformly embedded into the GPE to form the final PVDF-HFP/LATP composite gel polymer electrolyte (CPE). Impressively, the obtained CPE demonstrates a high lithium ion transference number of 0.51 and improved electrochemical stability as compared to commercial liquid electrolyte. In addition, the assembled solid-sate Li-S battery with the composite gel polymer electrolyte membrane presents a high initial capacity of 918 mAh g -1 at 0.05 C, and better cycle performance than the counterparts with liquid electrolyte. Our designed PVDF-HFP/LATP composite can be a promising electrolyte for next-generation solid-state batteries with high cycling stability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of a collagen/polymer hybrid gel designed for tissue membranes. Part I: controlling the polymer-collagen cross-linking process using an ethanol/water co-solvent.

PubMed

Nam, Kwangwoo; Kimura, Tsuyoshi; Funamoto, Seiichi; Kishida, Akio

2010-02-01

The drawback with collagen/2-methacryloyloxyethyl phosphorylcholine (MPC) polymer hybrid gels (collagen/phospholipid polymer hybrid gels) prepared in alkaline morpholinoethane sulfonic acid (MES) aqueous solution is that the cross-linking rate between the polymer and the collagen is low. To solve this problem, ethanol has been adopted as the reaction solvent, to prevent 1-ethyl-3-(3-dimethylaminopropyl)-1-carbodiimide hydrochloride (EDC) hydrolysis. Alterations in the ethanol mole concentration changed the cross-linking rate between the MPC polymer and the collagen gel. Prevention of EDC hydrolysis is clearly observed; protonation of carboxyl groups implies that the ratio of ethanol to water should be controlled. The polymer shows signs of penetration into the collagen gel layer, thus forming a totally homogeneous phase gel. This affects the mechanical strength of the collagen gel, making the gel much stiffer and brittle with an increase in the swelling ratio, as compared with that prepared in MES buffer. However, it is possible to obtain a collagen/phospholipid polymer hybrid gel with a high polymer portion and the cross-linking rate can be successfully controlled.

Gel polymer electrolyte for lithium-ion batteries comprising cyclic carbonate moieties

NASA Astrophysics Data System (ADS)

Tillmann, S. D.; Isken, P.; Lex-Balducci, A.

2014-12-01

A polymer system based on oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and cyclic carbonate methacrylate (CCMA) was chosen as matrix to realize high-performance gel polymer electrolytes due to the fact that both monomers are able to interact with the liquid electrolyte, thus, retaining it inside the matrix. Additionally, OEGMA enables high flexibility, while CCMA provides mechanical stability. The polymer displays a high thermal stability up to 200 °C and a glass transition temperature below room temperature (5 °C) allowing an easy handling of the obtained films. By immobilizing the liquid electrolyte 1 M LiPF6 in EC:DMC 1:1 w:w in the polymer host a gel polymer electrolyte with a high conductivity of 2.3 mS cm-1 at 25 °C and a stable cycling behavior with high capacities and efficiencies in Li(Ni1/3Co1/3Mn1/3)O2 (NCM)/graphite full cells is obtained. The investigated gel polymer electrolyte is identified as promising electrolyte for lithium-ion batteries, because it combines good electrochemical properties comparable to that of liquid electrolytes with the safety advantage that no leakage of the flammable electrolyte solvents can occur.

The impact of the oxygen scavenger on the dose-rate dependence and dose sensitivity of MAGIC type polymer gels

NASA Astrophysics Data System (ADS)

Khan, Muzafar; Heilemann, Gerd; Kuess, Peter; Georg, Dietmar; Berg, Andreas

2018-03-01

Recent developments in radiation therapy aimed at more precise dose delivery along with higher dose gradients (dose painting) and more efficient dose delivery with higher dose rates e.g. flattening filter free (FFF) irradiation. Magnetic-resonance-imaging based polymer gel dosimetry offers 3D information for precise dose delivery techniques. Many of the proposed polymer gels have been reported to exhibit a dose response, measured as relaxation rate ΔR2(D), which is dose rate dependent. A lack of or a reduced dose-rate sensitivity is very important for dosimetric accuracy, especially with regard to the increasing clinical use of FFF irradiation protocols with LINACs at high dose rates. Some commonly used polymer gels are based on Methacrylic-Acid-Gel-Initiated-by-Copper (MAGIC). Here, we report on the dose sensitivity (ΔR2/ΔD) of MAGIC-type gels with different oxygen scavenger concentration for their specific dependence on the applied dose rate in order to improve the dosimetric performance, especially for high dose rates. A preclinical x-ray machine (‘Yxlon’, E  =  200 kV) was used for irradiation to cover a range of dose rates from low \\dot{D} min  =  0.6 Gy min-1 to high \\dot{D} max  =  18 Gy min-1. The dose response was evaluated using R2-imaging of the gel on a human high-field (7T) MR-scanner. The results indicate that all of the investigated dose rates had an impact on the dose response in polymer gel dosimeters, being strongest in the high dose region and less effective for low dose levels. The absolute dose rate dependence \\frac{(Δ R2/Δ D)}{Δ \\dot{D}} of the dose response in MAGIC-type gel is significantly reduced using higher concentrations of oxygen scavenger at the expense of reduced dose sensitivity. For quantitative dose evaluations the relative dose rate dependence of a polymer gel, normalized to its sensitivity is important. Based on this normalized sensitivity the dose rate sensitivity was reduced distinctly using an increased oxygen scavenger concentration with reference to standard MAGIC-type gel formulation at high dose rate levels. The proposed gel composition with high oxygen scavenger concentration exhibits a larger linear active dose response and might be used especially in FFF-radiation applications and preclinical dosimetry at high dose rates. We propose in general to use high dose rates for calibration and evaluation as the change in relative dose sensitivity is reduced at higher dose rates in all of the investigated gel types.

Characterization of a Bio-Based, Biodegradable Class of Copolymers, Poly[(R)-3-Hydroxybutyrate-Co-(R)-3- Hydroxyhexanoate], and Application Development

NASA Astrophysics Data System (ADS)

Sobieski, Brian

As modern society begins to focus on sustainability and renewable resources there is a growing need for the polymer industry to develop more environmentally friendly materials and practices. Part of this movement can be seen in the use of recycled materials in new products and in the development of bio-based, biodegradable polymers. Bio-based, biodegradable polymers are produced from renewable carbon sources, such as vegetable oils, typically polymerized using fermentation reactions via bacteria, and are able to be consumed by bacteria in landfills to completely convert the polymers to water and CO2. One class of such polymers are poly(hydroxyalkanoate)'s (PHAs), which are chiral, aliphatic polyesters. Within this class of polyesters are poly(hydroxybutyrate) (PHB) and the copolymer poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] (PHBHx), which have received extensive study due to their material properties as thermoplastics. Although the properties of PHB have been widely explored, much still remains to be understood about these promising biodegradable polymers. Specifically, PHB and its copolymers exhibit physical gelation in most solvents, yet the origin and mechanism of gelation and the properties of the resulting gel state are unknown. This research effort was primarily focused on investigating the physical gel state of PHBHx. Five goals were laid out and completed: determining the origin of gelation, the mechanism of gelation, the structure of the gel state, the properties of the gel state, and the effects of gelation on electrospun fibers of PHBHx. These goals were achieved through material characterization of the gel state utilizing infrared spectroscopy/two-dimensional correlation spectroscopy, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and many other analysis methods. Crystallization of the polymer in solution was found to cause gelation in PHBHx solutions, where the polymer crystals act as tie points forming an interconnected network. The process of crystallization in solution was determined to follow the same method as crystallization in the bulk, neat polymer as it is cooled from a molten state. Morphological studies revealed that the polymer forms sub-micron fibrils and ribbons in xxviii the gel system forming an interconnected polymer network. The utility of this morphology combined with the bio-compatibility of PHBHx were demonstrated through growth of stem cells on the gel samples. Surprisingly, the stem cells did not differentiate and thrived on the freeze-dried PHBHx gels. These results indicate that the gel state of PHBHx could be used as a tissue engineering scaffold whose material properties can be tuned to the desired application without the concern of the stem cells differentiating into an unwanted cell type. Combined with the ease of generation of the PHBHx gels, these results show promising potential for industrial production of excellent three-dimensional culturing scaffolds. It was also found that the gels do not show signs of aging after gelation is complete and that the polymer exists in the amorphous and primary alpha crystal phases when gelled. Electrospun fibers of the polymer in solution with a solvent that promotes gelation displayed a new morphology. Rather than the typical cylindrical fiber morphology, these fibers formed coiled fiber mats. It is proposed that the formation of crystals before the fibers are formed causes the fibers to collapse thus forming the coils. Additional research was conducted on the neat polymer itself to further explore its material properties. PHB and PHBHx tend to have multiple melting transitions when heated to the amorphous phase. This multiple melting behavior was caused by the same, primary crystal form recrystallizing and having a bimodal size distribution, rather than arising from two different crystal phases. Thermal degradation of the copolymers was also studied and the reaction pathway suggested, beginning with the formation of a six-member ring precursor leading to chain scission of the polymer. It was also found that the formation of this precursor may cause the higher 3HHx content copolymers to be slightly more stable at high temperatures due to steric hindrance. Strain-induced crystallization of the beta crystal of PHBHx was performed in the 13 mol % 3HHx PHBHx by stretching films of the copolymer. All the research conducted during this project were performed to generate additional applications and further the utility of this class of bio-based, biodegradable polyesters.

Physical Properties of Substituted Imidazolium Based Ionic Liquids Gel Electrolytes

NASA Astrophysics Data System (ADS)

Sutto, Thomas E.; De Long, Hugh C.; Trulove, Paul C.

2002-11-01

The physical properties of solid gel electrolytes of either polyvinylidene diflurohexafluoropropylene or a combination of polyvinylidene hexafluoropropylene and polyacrylic acid, and the molten salts 1-ethyl-3-methylimidazolium tetrafluoroborate, 1,2-dimethyl-3-n-propylimidazolium tetrafluoroborate, and the new molten salts 1,2-dimethyl-3-n-butylimidazolium tetrafluoroborate, and 1,2-dimethyl-3-n-butylimidazolium hexafluorophosphate were characterized by temperature dependent ionic conductivity measurements for both the pure molten salt and of the molten salt with 0.5 M Li+ present. Ionic conductivity data indicate that for each of the molten salts, the highest concentration of molten salt allowable in a single component polymer gel was 85%, while gels composed of 90%molten salt were possible when using both polyvinylidene hexafluorophosphate and polyacrylic acid. For polymer gel composites prepared using lithium containing ionic liquids, the optimum polymer gel composite consisted of 85% of the 0.5 M Li+/ionic liquid, 12.75% polyvinylidene hexafluoropropylene, and 2.25% poly (1-carboxyethylene). The highest ionic conductivity observed was for the gel containing 90%1-ethyl-3-methyl-imidazolium tetrafluoroborate, 9.08 mS/cm. For the lithium containing ionic liquid gels, their ionic conductivity ranged from 1.45 to 0.05 mS/cm, which is comparable to the value of 0.91 mS/cm, observed for polymer composite gels containing 0.5 M LiBF4 in propylene carbonate.

Amoeba-like self-oscillating polymeric fluids with autonomous sol-gel transition

PubMed Central

Onoda, Michika; Ueki, Takeshi; Tamate, Ryota; Shibayama, Mitsuhiro; Yoshida, Ryo

2017-01-01

In the field of polymer science, many kinds of polymeric material systems that show a sol-gel transition have been created. However, most systems are unidirectional stimuli-responsive systems that require physical signals such as a change in temperature. Here, we report on the design of a block copolymer solution that undergoes autonomous and periodic sol-gel transition under constant conditions without any on–off switching through external stimuli. The amplitude of this self-oscillation of the viscosity is about 2,000 mPa s. We also demonstrate an intermittent forward motion of a droplet of the polymer solution synchronized with the autonomous sol-gel transition. This polymer solution bears the potential to become the base for a type of slime-like soft robot that can transform its shape kaleidoscopically and move autonomously, which is associated with the living amoeba that moves forward by a repeated sol-gel transition. PMID:28703123

Amoeba-like self-oscillating polymeric fluids with autonomous sol-gel transition

NASA Astrophysics Data System (ADS)

Onoda, Michika; Ueki, Takeshi; Tamate, Ryota; Shibayama, Mitsuhiro; Yoshida, Ryo

2017-07-01

In the field of polymer science, many kinds of polymeric material systems that show a sol-gel transition have been created. However, most systems are unidirectional stimuli-responsive systems that require physical signals such as a change in temperature. Here, we report on the design of a block copolymer solution that undergoes autonomous and periodic sol-gel transition under constant conditions without any on-off switching through external stimuli. The amplitude of this self-oscillation of the viscosity is about 2,000 mPa s. We also demonstrate an intermittent forward motion of a droplet of the polymer solution synchronized with the autonomous sol-gel transition. This polymer solution bears the potential to become the base for a type of slime-like soft robot that can transform its shape kaleidoscopically and move autonomously, which is associated with the living amoeba that moves forward by a repeated sol-gel transition.

Buckling of paramagnetic chains in soft gels

NASA Astrophysics Data System (ADS)

Huang, Shilin; Pessot, Giorgio; Cremer, Peet; Weeber, Rudolf; Holm, Christian; Nowak, Johannes; Odenbach, Stefan; Menzel, Andreas M.; Auernhammer, Günter K.

We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under oblique magnetic fields, in particular a pronounced buckling deformation. The details of the resulting morphological shapes depend on the length of the chain, the strength of the external magnetic field, and the modulus of the gel. Based on the observation that the magnetic chains are strongly coupled to the surrounding polymer network, a simplified model is developed to describe their buckling behavior. A coarse-grained molecular dynamics simulation model featuring an increased matrix stiffness on the surfaces of the particles leads to morphologies in agreement with the experimentally observed buckling effects.

SU-E-T-243: MonteCarlo Simulation Study of Polymer and Radiochromic Gel for Three-Dimensional Proton Dose Distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, M; Jung, H; Kim, G

2014-06-01

Purpose: To estimate the three dimensional dose distributions in a polymer gel and a radiochromic gel by comparing with the virtual water phantom exposed to proton beams by applying Monte Carlo simulation. Methods: The polymer gel dosimeter is the compositeness material of gelatin, methacrylic acid, hydroquinone, tetrakis, and distilled water. The radiochromic gel is PRESAGE product. The densities of polymer and radiochromic gel were 1.040 and 1.0005 g/cm3, respectively. The shape of water phantom was a hexahedron with the size of 13 × 13 × 15 cm3. The proton beam energies of 72 and 116 MeV were used in themore » simulation. Proton beam was directed to the top of the phantom with Z-axis and the shape of beam was quadrangle with 10 × 10 cm2 dimension. The Percent depth dose and the dose distribution were evaluated for estimating the dose distribution of proton particle in two gel dosimeters, and compared with the virtual water phantom. Results: The Bragg-peak for proton particles in two gel dosimeters was similar to the virtual water phantom. Bragg-peak regions of polymer gel, radiochromic gel, and virtual water phantom were represented in the identical region (4.3 cm) for 72 MeV proton beam. For 116 MeV proton beam, the Bragg-peak regions of polymer gel, radiochromic gel, and virtual water phantom were represented in 9.9, 9.9 and 9.7 cm, respectively. The dose distribution of proton particles in polymer gel, radiochromic gel, and virtual water phantom was approximately identical in the case of 72 and 116 MeV energies. The errors for the simulation were under 10%. Conclusion: This work indicates the evaluation of three dimensional dose distributions by exposing proton particles to polymer and radiochromic gel dosimeter by comparing with the water phantom. The polymer gel and the radiochromic gel dosimeter show similar dose distributions for the proton beams.« less

Deformation and fracture of cross-linked polymer gels

NASA Astrophysics Data System (ADS)

Lin, Wei-Chun

Because soft materials, particularly polymer gels, are playing a greater role in industrial and biotechnological applications today, the exploration of their mechanical behavior over a range of deformations is becoming more relevant in our daily lives. Understanding these properties is therefore necessary as a means to predict their response for specific applications. To address these concerns, this dissertation presents a set of analytic tools based on flat punch probe indentation tests to predict the response of polymer gels from a mechanical perspective over a large range of stresses and at failure. At small strains, a novel technique is developed to determine the transport properties of gels based on their measured mechanical behavior. Assuming that a polymer gel behaves in a similar manner as a porous structure, the differentiation of solvent flow from viscoelasticity of a gel network is shown to be possible utilizing a flat, circular punch and a flat, rectangular punch under oscillatory conditions. Use of the technique is demonstrated with a poly(N-isopropyl acrylamide) (pNIPAM) hydrogel. Our results indicate that solvent flow is inhibited at temperatures above the critical solution temperature of 35°C. At high stresses and fracture, the flat probe punch indentation geometry is used to understand how the structure and geometry of silicone based gels affect their mechanical properties. A delayed failure response of the gels is observed and the modes of failure are found to be dependent on the geometry of the system. The addition of a sol fraction in these gels was found to toughen the network and play an important role at these large deformations. Potential mechanisms of fracture resistance are discussed, as is the effect of geometric confinement as it relates to large scale deformation and fracture. These results lay the groundwork for understanding the mechanical response of other highly, deformable material systems utilizing this particular geometry.

Dosimetry study of diagnostic X-ray using doped iodide normoxic polymer gels

NASA Astrophysics Data System (ADS)

Huang, Y. R.; Chang, Y. J.; Hsieh, L. L.; Liu, M. H.; Liu, J. S.; Chu, C. H.; Hsieh, B. T.

2014-11-01

In radiotherapy, polymer gel dosimeters are used for three-dimensional (3D) dose distribution. However, the doses are within the Gy range. In this study, we attempted to develop a low-dose 3D dosimeter within the mGy range for diagnostic radiology. The effect of the iodinated compound was used as a dose enhancement sensitizer to enhance the dose sensitivity of normoxic polymer gel dosimeters. This study aims to use N-isopropylacrylamide(NIPAM)-based and methacrylic acid (MAGAT)-based gels to evaluate the potential dose enhancement sensitizer, as well as to compare two gels that may be suitable for measuring diagnostic radiation doses. The suitable formulation of NIPAM gel [5% (w/w) gelatin, 5% (w/w) NIPAM, 3% (w/w) N,N‧-methylenebisacrylamide (BIS), 5 mM tetrakis (hydroxymethyl) phosphonium chloride (THPC), and 87% (w/w) deionized distilled water] and MAGAT gel (4% MAA, 9% gelatin, 87% deionized water, and 10 mM THPC) were used and loaded with clinical iodinated contrast medium agent (Iobitridol, Xenetix® 350). Irradiation was conducted using X-ray computed tomography. The irradiation doses ranged from 0 mGy to 80 mGy. Optical computed tomography was the employed gel measurement system. The results indicate that the iodinated contrast agent yields a quantifiable dose enhancement ratio. The dose enhancement ratios of NIPAM and MAGAT gels are 3.35±0.6 and 1.36±0.3, respectively. The developed NIPAM gel in this study could be suitable for measuring diagnostic radiation doses.

COUPLING THE ALKALINE-SURFACTANT-POLYMER TECHNOLOGY AND THE GELATION TECHNOLOGY TO MAXIMIZE OIL PRODUCTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-04-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or more efficient areal sweep efficiency for those with high permeability contrast ''thief zones''. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or those with thief zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. A priormore » fluid-fluid report discussed interaction of different gel chemical compositions and alkaline-surfactant-polymer solutions. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses. Aluminum-polyacrylamide, flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9. Chromium acetate-polyacrylamide flowing and rigid flowing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid flowing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid flowing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid flowing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. None of the gels tested appeared to alter alkaline-surfactant-polymer solution oil recovery. Total waterflood plus chemical flood oil recovery sequence recoveries were all similar.« less

Multi-Stimuli-Responsive Polymer Materials: Particles, Films, and Bulk Gels.

PubMed

Cao, Zi-Quan; Wang, Guo-Jie

2016-06-01

Stimuli-responsive polymers have received tremendous attention from scientists and engineers for several decades due to the wide applications of these smart materials in biotechnology and nanotechnology. Driven by the complex functions of living systems, multi-stimuli-responsive polymer materials have been designed and developed in recent years. Compared with conventional single- or dual-stimuli-based polymer materials, multi-stimuli-responsive polymer materials would be more intriguing since more functions and finer modulations can be achieved through more parameters. This critical review highlights the recent advances in this area and focuses on three types of multi-stimuli-responsive polymer materials, namely, multi-stimuli-responsive particles (micelles, micro/nanogels, vesicles, and hybrid particles), multi-stimuli-responsive films (polymer brushes, layer-by-layer polymer films, and porous membranes), and multi-stimuli-responsive bulk gels (hydrogels, organogels, and metallogels) from recent publications. Various stimuli, such as light, temperature, pH, reduction/oxidation, enzymes, ions, glucose, ultrasound, magnetic fields, mechanical stress, solvent, voltage, and electrochemistry, have been combined to switch the functions of polymers. The polymer design, preparation, and function of multi-stimuli-responsive particles, films, and bulk gels are comprehensively discussed here. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gel polymer electrolytes for batteries

DOEpatents

Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William

2014-11-18

Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at 25.degree. C.

Molecular weight dependency of polyrotaxane-cross-linked polymer gel extensibility.

PubMed

Ohmori, Kana; Abu Bin, Imran; Seki, Takahiro; Liu, Chang; Mayumi, Koichi; Ito, Kohzo; Takeoka, Yukikazu

2016-12-11

This work investigates the influence of the molecular weight of polyrotaxane (PR) cross-linkers on the extensibility of polymer gels. The polymer gels, which were prepared using PR cross-linkers of three different molecular weights but the same number of cross-linking points per unit volume of gel, have almost the same Young's modulus. By contrast, the extensibility and rupture strength of the polymer gels are substantially increased with increasing molecular weight of the PR cross-linker.

In situ immobilization on the silica gel surface and adsorption capacity of polymer-based azobenzene on toxic metal ions

NASA Astrophysics Data System (ADS)

Savchenko, Irina; Yanovska, Elina; Sternik, Dariusz; Kychkyruk, Olga; Ol'khovik, Lidiya; Polonska, Yana

2018-03-01

In situ immobilization of poly[(4-methacryloyloxy-(4'-carboxy)azobenzene] on silica gel surface has been performed by radical polymerization of monomer. The fact of polymer immobilization is confirmed by IR spectroscopy. TG and DSC-MS analysis showed that the mass of the immobilized polymer was 10.61%. The SEM-microphotograph-synthesized composite analysis showed that the immobilized polymer on the silica gel surface is placed in the form of fibers. It has been found that the synthesized composite exhibits the sorption ability in terms of microquantities of Cu(II), Cd(II), Pb(II), Mn(II) and Fe(III) ions in a neutral aqueous medium. The quantitative sorption of microquantities of Pb(II) and Fe(III) ions has been recorded. It has been found that immobilization of the silica gel surface leads to an increase in its sorption capacitance for Fe(III), Cu(II) and Pb(II) ions by half.

Method of improving heterogeneous oil reservoir polymer flooding effect by positively-charged gel profile control

NASA Astrophysics Data System (ADS)

Zhao, Ling; Xia, Huifen

2018-01-01

The project of polymer flooding has achieved great success in Daqing oilfield, and the main oil reservoir recovery can be improved by more than 15%. But, for some strong oil reservoir heterogeneity carrying out polymer flooding, polymer solution will be inefficient and invalid loop problem in the high permeability layer, then cause the larger polymer volume, and a significant reduction in the polymer flooding efficiency. Aiming at this problem, it is studied the method that improves heterogeneous oil reservoir polymer flooding effect by positively-charged gel profile control. The research results show that the polymer physical and chemical reaction of positively-charged gel with the residual polymer in high permeability layer can generate three-dimensional network of polymer, plugging high permeable layer, and increase injection pressure gradient, then improve the effect of polymer flooding development. Under the condition of the same dosage, positively-charged gel profile control can improve the polymer flooding recovery factor by 2.3∼3.8 percentage points. Under the condition of the same polymer flooding recovery factor increase value, after positively-charged gel profile control, it can reduce the polymer volume by 50 %. Applying mechanism of positively-charged gel profile control technology is feasible, cost savings, simple construction, and no environmental pollution, therefore has good application prospect.

SU-E-T-105: Development of 3D Dose Verification System for Volumetric Modulated Arc Therapy Using Improved Polyacrylamide-Based Gel Dosimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, K; Fujimoto, S; Akagi, Y

2014-06-01

Purpose: The aim of this dosimetric study was to develop 3D dose verification system for volumetric modulated arc therapy (VMAT) using polyacrylamide-based gel (PAGAT) dosimeter improved the sensitivity by magnesium chloride (MgCl{sub 2}). Methods: PAGAT gel containing MgCl{sub 2} as a sensitizer was prepared in this study. Methacrylic-acid-based gel (MAGAT) was also prepared to compare the dosimetric characteristics with PAGAT gel. The cylindrical glass vials (4 cm diameter, 12 cm length) filled with each polymer gel were irradiated with 6 MV photon beam using Novalis Tx linear accelerator (Varian/BrainLAB). The irradiated polymer gel dosimeters were scanned with Signa 1.5 Tmore » MRI system (GE), and dose calibration curves were obtained using T{sub 2} relaxation rate (R{sub 2} = 1/T{sub 2}). Dose rate (100-600 MU min{sup −1}) and fractionation (1-8 fractions) were varied. In addition, a cubic acrylic phantom (10 × 10 × 10 cm{sup 3}) filled with improved PAGAT gel inserted into the IMRT phantom (IBA) was irradiated with VMAT (RapidArc). C-shape structure was used for the VMAT planning by the Varian Eclipse treatment planning system (TPS). The dose comparison of TPS and measurements with the polymer gel dosimeter was accomplished by the gamma index analysis, overlaying the dose profiles for a set of data on selected planes using in-house developed software. Results: Dose rate and fractionation dependence of improved PAGAT gel were smaller than MAGAT gel. A high similarity was found by overlaying the dose profiles measured with improved PAGAT gel dosimeter and the TPS dose, and the mean pass rate of the gamma index analysis using 3%/3 mm criteria was achieved 90% on orthogonal planes for VMAT using improved PAGAT gel dosimeter. Conclusion: In-house developed 3D dose verification system using improved polyacrylamide-based gel dosimeter had a potential as an effective tool for VMAT QA.« less

Correlation between ion diffusional motion and ionic conductivity for different electrolytes based on ionic liquid.

PubMed

Kaur, Dilraj Preet; Yamada, K; Park, Jin-Soo; Sekhon, S S

2009-04-23

Room temperature ionic liquid 2,3-dimethyl-1-hexylimidazolium bis(trifluoromethane sulfonyl)imide (DMHxImTFSI) has been synthesized and used in the preparation of polymer gel electrolytes containing polymethylmethacrylate and propylene carbonate (PC). The onset of ion diffusional motion has been studied by (1)H and (19)F NMR spectroscopy and the results obtained for ionic liquid, liquid electrolytes, and polymer gel electrolytes have been correlated with the ionic conductivity results for these electrolytes in the 100-400 K temperature range. The temperature at which (1)H and (19)F NMR lines show motional narrowing and hence ion diffusional motion starts has been found to be closely related to the temperature at which a large increase in ionic conductivity has been observed for these electrolytes. Polymer gel electrolytes have high ionic conductivity over a wide range of temperatures. Thermogravimetric analysis/differential scanning calorimetry studies show that the ionic liquid (DMHxImTFSI) used in the present study is thermally stable up to 400 degrees C, whereas the addition of PC lowers the thermal stability of polymer gel electrolytes containing the ionic liquid. Different electrolytes have been observed to show high ionic conductivity in different range of temperatures, which can be helpful in the design of polymer gel electrolytes for specific applications.

Performance of a commercial optical CT scanner and polymer gel dosimeters for 3-D dose verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Y.; Wuu, C.-S.; Maryanski, Marek J.

2004-11-01

Performance analysis of a commercial three-dimensional (3-D) dose mapping system based on optical CT scanning of polymer gels is presented. The system consists of BANG{sup reg}3 polymer gels (MGS Research, Inc., Madison, CT), OCTOPUS{sup TM} laser CT scanner (MGS Research, Inc., Madison, CT), and an in-house developed software for optical CT image reconstruction and 3-D dose distribution comparison between the gel, film measurements and the radiation therapy treatment plans. Various sources of image noise (digitization, electronic, optical, and mechanical) generated by the scanner as well as optical uniformity of the polymer gel are analyzed. The performance of the scanner ismore » further evaluated in terms of the reproducibility of the data acquisition process, the uncertainties at different levels of reconstructed optical density per unit length and the effects of scanning parameters. It is demonstrated that for BANG{sup registered}3 gel phantoms held in cylindrical plastic containers, the relative dose distribution can be reproduced by the scanner with an overall uncertainty of about 3% within approximately 75% of the radius of the container. In regions located closer to the container wall, however, the scanner generates erroneous optical density values that arise from the reflection and refraction of the laser rays at the interface between the gel and the container. The analysis of the accuracy of the polymer gel dosimeter is exemplified by the comparison of the gel/OCT-derived dose distributions with those from film measurements and a commercial treatment planning system (Cadplan, Varian Corporation, Palo Alto, CA) for a 6 cmx6 cm single field of 6 MV x rays and a 3-D conformal radiotherapy (3DCRT) plan. The gel measurements agree with the treatment plans and the film measurements within the '3%-or-2 mm' criterion throughout the usable, artifact-free central region of the gel volume. Discrepancies among the three data sets are analyzed.« less

Classical Challenges in the Physical Chemistry of Polymer Networks and the Design of New Materials.

PubMed

Wang, Rui; Sing, Michelle K; Avery, Reginald K; Souza, Bruno S; Kim, Minkyu; Olsen, Bradley D

2016-12-20

Polymer networks are widely used from commodity to biomedical materials. The space-spanning, net-like structure gives polymer networks their advantageous mechanical and dynamic properties, the most essential factor that governs their responses to external electrical, thermal, and chemical stimuli. Despite the ubiquity of applications and a century of active research on these materials, the way that chemistry and processing interact to yield the final structure and the material properties of polymer networks is not fully understood, which leads to a number of classical challenges in the physical chemistry of gels. Fundamentally, it is not yet possible to quantitatively predict the mechanical response of a polymer network based on its chemical design, limiting our ability to understand and characterize the nanostructure of gels and rationally design new materials. In this Account, we summarize our recent theoretical and experimental approaches to study the physical chemistry of polymer networks. First, our understanding of the impact of molecular defects on topology and elasticity of polymer networks is discussed. By systematically incorporating the effects of different orders of loop structure, we develop a kinetic graph theory and real elastic network theory that bridge the chemical design, the network topology, and the mechanical properties of the gel. These theories show good agreement with the recent experimental data without any fitting parameters. Next, associative polymer gel dynamics is discussed, focusing on our evolving understanding of the effect of transient bonds on the mechanical response. Using forced Rayleigh scattering (FRS), we are able to probe diffusivity across a wide range of length and time scales in gels. A superdiffusive region is observed in different associative network systems, which can be captured by a two-state kinetic model. Further, the effects of the architecture and chemistry of polymer chains on gel nanostructure are studied. By incorporating shear-thinning coiled-coil protein motifs into the midblock of a micelle-forming block copolymer, we are able to responsively adjust the gel toughness through controlling the nanostructure. Finally, we review the development of novel application-oriented materials that emerge from our enhanced understanding of gel physical chemistry, including injectable gel hemostats designed to treat internal wounds and engineered nucleoporin-like polypeptide (NLP) hydrogels that act as biologically selective filters. We believe that the fundamental physical chemistry questions articulated in this Account will provide inspiration to fully understand the design of polymer networks, a group of mysterious yet critically important materials.

Incorporating allylated lignin-derivatives in thiol-ene gel-polymer electrolytes.

PubMed

Baroncini, Elyse A; Stanzione, Joseph F

2018-07-01

Growing environmental and economic concerns as well as the uncertainty that accompanies finite petrochemical resources contributes to the increase in research and development of bio-based, renewable polymers. Concurrently, industrial and consumer demand for smaller, safer, and more flexible technologies motivates a global research effort to improve electrolytic polymer separators in lithium-ion batteries. To incorporate the aromatic structural advantages of lignin, a highly abundant and renewable resource, into gel-polymer electrolytes, lignin-derived molecules, vanillyl alcohol and gastrodigenin are functionalized and UV-polymerized with multi-functional thiol monomers. The resulting thin, flexible, polymer films possess glass transition temperatures ranging from -42.1°C to 0.3°C and storage moduli at 25°C ranging from 1.90MPa to 10.08MPa. The crosslinked polymer films swollen with electrolyte solution impart conductivities in the range of 7.04×10 -7 to 102.73×10 -7 Scm -1 . Thiol molecular weight has the most impact on the thermo-mechanical properties of the resulting films while polymer crosslink density has the largest effect on conductivity. The conducting abilities of the bio-based gel-polymer electrolytes in this study prove the viability of lignin-derived feedstock for use in lithium-ion battery applications and reveal structurally and thermally desirable traits for future work. Copyright © 2018 Elsevier B.V. All rights reserved.

Quaternized Q-PEIPAAm-Based Antimicrobial Reverse Thermal Gel: A Potential for Surgical Incision Drapes.

PubMed

Bortot, Maria; Laughter, Melissa Ronni; Stein, Madia; Rocker, Adam; Patel, Vikas; Park, Daewon

2018-05-16

A quaternized reverse thermal gel (RTG) aimed at replacing current surgical incision drapes (SIDs) was designed and characterized. The antimicrobial efficacy of the quaternized RTG was analyzed using both in vitro and in vivo models and was compared to standard SIDs. Polymer characterization was completed using both nuclear magnetic resonance ( 1 H NMR) and lower critical solution temperature (LCST) analysis. Biocompatibility was assessed using a standard cell viability assay. The in vitro antimicrobial efficacy of the polymer was analyzed against four common bacteria species using a time-kill test. The in vivo antimicrobial efficacy of the polymer and standard SIDs were compared using a murine model aimed at mimicking surgical conditions. NMR confirmed the polymer structure and presence of quaternized groups and alkyl chains. The polymer displayed a LCST of 34 °C and a rapid rate of gelation, allowing stable gel formation when applied to skin. Once quaternized, the polymer displayed an increase in kill-rate of bacteria compared to unquaternized polymer. In experiments aimed at mimicking surgical conditions, the quaternized polymer showed statistically comparable bacteria-killing capacity to the standard SID and even surpassed the SID for killing capacity at various time points. A novel approach to replacing current SIDs was developed using an antimicrobial polymer system with RTG properties. The RTG properties of this polymer maintain a liquid state at low temperatures and a gel upon heating, allowing this polymer to form a tight coating when applied to skin. Furthermore, this polymer achieved excellent antimicrobial properties in both in vitro and in vivo models. With further optimization, this polymer system has the potential to replace and streamline presurgical patient preparations through its easy application and beneficial antimicrobial properties.

Electroactive polymer gels based on epoxy resin

NASA Astrophysics Data System (ADS)

Samui, A. B.; Jayakumar, S.; Jayalakshmi, C. G.; Pandey, K.; Sivaraman, P.

2007-04-01

Five types of epoxy gels have been synthesized from common epoxy resins and hardeners. Fumed silica and nanoclay, respectively, were used as fillers and butyl methacrylate/acrylamide were used as monomer(s) for making interpenetrating polymer networks (IPNs) in three compositions. Swelling study, tensile property evaluation, dynamic mechanical thermal analysis, thermo-gravimetric analysis, scanning electron microscopy and electroactive property evaluation were done. The gels have sufficient mechanical strength and the time taken for bending to 20° was found to be 22 min for forward bias whereas it was just 12 min for reverse bias.

Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification

NASA Astrophysics Data System (ADS)

Vandecasteele, Jan; De Deene, Yves

2013-09-01

A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which proves the need for adequate compensation strategies.

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randall S. Seright

2007-09-30

This final technical progress report describes work performed from October 1, 2004, through May 16, 2007, for the project, 'Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling'. We explored the potential of pore-filling gels for reducing excess water production from both fractured and unfractured production wells. Several gel formulations were identified that met the requirements--i.e., providing water residual resistance factors greater than 2,000 and ultimate oil residual resistance factors (F{sub rro}) of 2 or less. Significant oil throughput was required to achieve low F{sub rro} values, suggesting that gelant penetration into porous rock must be small (a few feet or less) formore » existing pore-filling gels to provide effective disproportionate permeability reduction. Compared with adsorbed polymers and weak gels, strong pore-filling gels can provide greater reliability and behavior that is insensitive to the initial rock permeability. Guidance is provided on where relative-permeability-modification/disproportionate-permeability-reduction treatments can be successfully applied for use in either oil or gas production wells. When properly designed and executed, these treatments can be successfully applied to a limited range of oilfield excessive-water-production problems. We examined whether gel rheology can explain behavior during extrusion through fractures. The rheology behavior of the gels tested showed a strong parallel to the results obtained from previous gel extrusion experiments. However, for a given aperture (fracture width or plate-plate separation), the pressure gradients measured during the gel extrusion experiments were much higher than anticipated from rheology measurements. Extensive experiments established that wall slip and first normal stress difference were not responsible for the pressure gradient discrepancy. To explain the discrepancy, we noted that the aperture for gel flow (for mobile gel wormholing through concentrated immobile gel within the fracture) was much narrower than the width of the fracture. The potential of various approaches were investigated for improving sweep in parts of the Daqing Oil Field that have been EOR targets. Possibilities included (1) gel treatments that are directed at channeling through fractures, (2) colloidal dispersion gels, (3) reduced polymer degradation, (4) more viscous polymer solutions, and (5) foams and other methods. Fractures were present in a number of Daqing wells (both injectors and producers). Because the fractures were narrow far from the wellbore, severe channeling did not occur. On the contrary, fractures near the wellbore aided reservoir sweep. In the February 2006 issue of the Journal of Petroleum Technology, a 'Distinguished-Author-Series' paper claimed that a process using aqueous colloidal dispersion gels (CDG gels) performed superior to polymer flooding. Unfortunately, this claim is misleading and generally incorrect. Colloidal dispersion gels, in their present state of technological development, should not be advocated as an improvement to, or substitute for, polymer flooding.« less

SU-F-T-159: Monte Carlo Simulation Studies of Three-Dimensional Dose Distribution for Polymer Gel Dosimeter and Radiochromic Gel Dosimeter in a Proton Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, M; Kim, G; Jung, H

Purpose: The purpose of this simulation study is to evaluate the proton detectability of gel dosimeters, and estimate the three-dimensional dose distribution of protons in the radiochromic gel and polymer gel dosimeter compared with the dose distribution in water. Methods: The commercial composition ratios of normoxic polymer gel and LCV micelle radiochromic gel were included in this simulation study. The densities of polymer and radiochromic gel were 1.024 and 1.005 g/cm3, respectively. The 50, 80 and 140 MeV proton beam energies were selected. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiationmore » transport code (MCNPX 2.7.0, Los Alamos Laboratory). The water equivalent depth profiles and the dose distributions of two gel dosimeters were compared for the water. Results: In case of irradiating 50, 80 and 140 MeV proton beam to water phantom, the reference Bragg-peak depths are represented at 2.22, 5.18 and 13.98 cm, respectively. The difference in the water equivalent depth is represented to about 0.17 and 0.37 cm in the radiochromic gel and polymer gel dosimeter, respectively. The proton absorbed doses in the radiochromic gel dosimeter are calculated to 2.41, 3.92 and 6.90 Gy with increment of incident proton energies. In the polymer gel dosimeter, the absorbed doses are calculated to 2.37, 3.85 and 6.78 Gy with increment of incident proton energies. The relative absorbed dose in radiochromic gel (about 0.47 %) is similar to that of water than the relative absorbed dose of polymer gel (about 2.26 %). In evaluating the proton dose distribution, we found that the dose distribution of both gel dosimeters matched that of water in most cases. Conclusion: As the dosimetry device, the radiochromic gel dosimeter has the potential particle detectability and is feasible to use for quality assurance of proton beam therapy beam.« less

Efficient and Stable Photovoltaic Characteristics of Quasi-Solid State DSSC using Polymer Gel Electrolyte Based on Ionic Liquid in Organosiloxane Polymer Gels

NASA Astrophysics Data System (ADS)

Pujiarti, H.; Arsyad, W. S.; Shobih; Muliani, L.; Hidayat, R.

2018-04-01

Dye-Sensitized Solar Cell (DSSC) is still one of the promising solar cell types among the third generation of solar cells because of easiness of fabrication and variety of available materials. In this type of solar cell, the electrolyte is one of the important components for regenerating excited dyes and transporting electric charge carriers to the counter electrode. Indeed, the power conversion efficiency of DSSC can be then significantly affected by the chemical and physical properties of the electrolyte. The simplest electrolyte system of an I-/I3 - redox couple in an organic solvent, however, has some drawbacks due to corrosive properties, volatile and leakage problem. Use of solid phase or gel phase electrolyte may overcome those problems, but it is often considered to suppress the efficiency due to low ion diffusion. Here, we report the photovoltaic characteristics of DSSC using polymer gel electrolyte (PGE), which is composed of ionic liquid and an organosiloxane polymer gel. The better cell performance with power conversion efficiency of about 6% has been obtained by optimizing the mesoporous size of the TiO2 layer and the PGE viscosity.

Polymers in life sciences: Pharmaceutical and biomedical applications

NASA Astrophysics Data System (ADS)

Barba, Anna Angela; Dalmoro, Annalisa; d'Amore, Matteo; Lamberti, Gaetano; Cascone, Sara; Titomanlio, Giuseppe

2015-12-01

This paper deals with the work done by prof. Titomanlio and his group in the fields of pharmaceutical and biomedical applications of polymers. In particular, the main topics covered are: i) controlled drug release from pharmaceuticals based on hydrogel for oral delivery of drugs; ii) production and characterization of micro and nanoparticles based on stimuli-responsive polymers; iii) use of polymers for coronary stent gel-paving; iv) design and realization of novel methods (in-vitro and in-silico) to test polymer-based pharmaceuticals.

Electrical and dielectric properties of PVdF-HFP - PMMA - (PC + DEC)- LiClO4 based gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Gohel, Khushbu; Kanchan, D. K.; Maheshwaran, C.

2018-04-01

In the present paper, AC impedance studies have been measured to evaluate ion conduction behavior of (PVdF-HFP - PMMA) + (PC-DEC) + LiClO4 gel polymer electrolyte system prepared by solution casting method. Structural characterization and morphology has been carried out using XRD and SEM respectively. The AC conductivity and dielectric permittivity, electric modulus and relaxation mechanism have been studied. The variation of ac conductivity with frequency obeys Jonscher power law. Maximum value of dielectric constant ɛ' in the lower frequency region has been observed for the gel polymer electrolyte containing 7.5 wt% LiClO4. The highest conducting sample shows the shortest relaxation time.

Radiological characteristics of MRI-based VIP polymer gel under carbon beam irradiation

NASA Astrophysics Data System (ADS)

Maeyama, T.; Fukunishi, N.; Ishikawa, K. L.; Furuta, T.; Fukasaku, K.; Takagi, S.; Noda, S.; Himeno, R.; Fukuda, S.

2015-02-01

We study the radiological characteristics of VIP polymer gel dosimeters under carbon beam irradiation with energy of 135 and 290 AMeV. To evaluate dose response of VIP polymer gels, the transverse (or spin-spin) relaxation rate R2 of the dosimeters measured by magnetic resonance imaging (MRI) as a function of linear energy transfer (LET), rather than penetration depth, as is usually done in previous reports. LET is evaluated by use of the particle transport simulation code PHITS. Our results reveal that the dose response decreases with increasing dose-averaged LET and that the dose response-LET relation also varies with incident carbon beam energy. The latter can be explained by taking into account the contribution from fragmentation products.

Carbon Redox-Polymer-Gel Hybrid Supercapacitors.

PubMed

Vlad, A; Singh, N; Melinte, S; Gohy, J-F; Ajayan, P M

2016-02-26

Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances.

Soft, comfortable polymer dry electrodes for high quality ECG and EEG recording.

PubMed

Chen, Yun-Hsuan; Op de Beeck, Maaike; Vanderheyden, Luc; Carrette, Evelien; Mihajlović, Vojkan; Vanstreels, Kris; Grundlehner, Bernard; Gadeyne, Stefanie; Boon, Paul; Van Hoof, Chris

2014-12-10

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes offering high user comfort, since they are fabricated from EPDM rubber containing various additives for optimum conductivity, flexibility and ease of fabrication. The electrode impedance is measured on phantoms and human skin. After optimization of the polymer composition, the skin-electrode impedance is only ~10 times larger than that of gel electrodes. Therefore, these electrodes are directly capable of recording strong biopotential signals such as ECG while for low-amplitude signals such as EEG, the electrodes need to be coupled with an active circuit. EEG recordings using active polymer electrodes connected to a clinical EEG system show very promising results: alpha waves can be clearly observed when subjects close their eyes, and correlation and coherence analyses reveal high similarity between dry and gel electrode signals. Moreover, all subjects reported that our polymer electrodes did not cause discomfort. Hence, the polymer-based dry electrodes are promising alternatives to either rigid dry electrodes or conventional gel electrodes.

A study on the reproducibility and spatial uniformity of N-isopropylacrylamide polymer gel dosimetry using a commercial 10X fast optical-computed tomography scanner

NASA Astrophysics Data System (ADS)

Chang, Y. J.; Lin, J. Q.; Hsieh, B. T.; Chen, C. H.

2013-06-01

This study investigated the reproducibility and spatial uniformity of N-isopropylacrylamide (NIPAM) polymer gel as well as the reproducibility of a NIPAM polymer gel dosimeter. A commercial 10X fast optical computed tomography scanner (OCTOPUS-10X, MGS Research, Inc., Madison, CT, USA) was used as the readout tool of the NIPAM polymer gel dosimeter. A cylindrical NIPAM gel phantom measuring 10 cm (diameter) by 10 cm (height) by 3 mm (thickness) was irradiated by the four-field box treatment with a field size of 3 cm × 3 cm. The dose profiles were found to be consistent at the depths of 2.0 cm to 5.0 cm for two independent gel phantom batches, and the average uncertainty was less than 2%. The gamma pass rates were calculated to be between 94% and 95% at depths of 40 mm for two independent gel phantom batches using 4% dose difference and 4 mm distance-to-agreement criterion. The NIPAM polymer gel dosimeter was highly reproducible and spatially uniform. The results highlighted the potential of the NIPAM polymer gel dosimeter in radiotherapy.

NOTE: Investigating the potential of polymer gel dosimetry for interventional radiology: first results

NASA Astrophysics Data System (ADS)

Antoniou, P. E.; Bousbouras, P.; Sandaltzopoulos, R.; Kaldoudi, E.

2008-04-01

Complex interventional radiology (IR) procedures contribute an increasing percentage of the overall medical radiation exposure of the population making accurate dosimetry a challenge. Magnetic resonance (MR) based polymer gel dosimetry has been widely employed in complex dosimetric problems in radiotherapy. The aim of this note is to investigate the feasibility of normoxic gel dosimetry in IR. Dose response, energy dependence and dose rate dependence were investigated in irradiation set-ups relevant to IR for a particular normoxic gel, based on methacrylic acid (MAA) as the monomer and including tetrakis-hydroxy-methyl-phosphonium chloride (THPC) as antioxidant. The gel presents a linear dose response beyond a 25 cGy threshold. No significant energy dependence was observed in the useful range of interventional radiology (80-110 kVp). A linear correlation between the gel response and dose rate was observed in the range of dose rates relevant to IR (5-8 cGy min-1). These results demonstrate a reduction of gel sensitivity at very low dose rate levels. A possible explanation of this effect is suggested.

Poly(vinylidene fluoride-hexafluoropropylene) polymer electrolyte for paper-based and flexible battery applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aliahmad, Nojan; Shrestha, Sudhir; Varahramyan, Kody

2016-06-15

Paper-based batteries represent a new frontier in battery technology. However, low-flexibility and poor ionic conductivity of solid electrolytes have been major impediments in achieving practical mechanically flexible batteries. This work discuss new highly ionic conductive polymer gel electrolytes for paper-based battery applications. In this paper, we present a poly(vinylidene fluoride-hexafluoropropylene) (PVDH-HFP) porous membrane electrolyte enhanced with lithium bis(trifluoromethane sulphone)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP), with an ionic conductivity of 2.1 × 10{sup −3} S cm{sup −1}. Combining ceramic (LATP) with the gel structure of PVDF-HFP and LiTFSI ionic liquid harnesses benefits of ceramic and gel electrolytes in providingmore » flexible electrolytes with a high ionic conductivity. In a flexibility test experiment, bending the polymer electrolyte at 90° for 20 times resulted in 14% decrease in ionic conductivity. Efforts to further improving the flexibility of the presented electrolyte are ongoing. Using this electrolyte, full-cell batteries with lithium titanium oxide (LTO) and lithium cobalt oxide (LCO) electrodes and (i) standard metallic current collectors and (ii) paper-based current collectors were fabricated and tested. The achieved specific capacities were (i) 123 mAh g{sup −1} for standard metallic current collectors and (ii) 99.5 mAh g{sup −1} for paper-based current collectors. Thus, the presented electrolyte has potential to become a viable candidate in paper-based and flexible battery applications. Fabrication methods, experimental procedures, and test results for the polymer gel electrolyte and batteries are presented and discussed.« less

Poly(vinylidene fluoride-hexafluoropropylene) polymer electrolyte for paper-based and flexible battery applications

NASA Astrophysics Data System (ADS)

Aliahmad, Nojan; Shrestha, Sudhir; Varahramyan, Kody; Agarwal, Mangilal

2016-06-01

Paper-based batteries represent a new frontier in battery technology. However, low-flexibility and poor ionic conductivity of solid electrolytes have been major impediments in achieving practical mechanically flexible batteries. This work discuss new highly ionic conductive polymer gel electrolytes for paper-based battery applications. In this paper, we present a poly(vinylidene fluoride-hexafluoropropylene) (PVDH-HFP) porous membrane electrolyte enhanced with lithium bis(trifluoromethane sulphone)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP), with an ionic conductivity of 2.1 × 10-3 S cm-1. Combining ceramic (LATP) with the gel structure of PVDF-HFP and LiTFSI ionic liquid harnesses benefits of ceramic and gel electrolytes in providing flexible electrolytes with a high ionic conductivity. In a flexibility test experiment, bending the polymer electrolyte at 90° for 20 times resulted in 14% decrease in ionic conductivity. Efforts to further improving the flexibility of the presented electrolyte are ongoing. Using this electrolyte, full-cell batteries with lithium titanium oxide (LTO) and lithium cobalt oxide (LCO) electrodes and (i) standard metallic current collectors and (ii) paper-based current collectors were fabricated and tested. The achieved specific capacities were (i) 123 mAh g-1 for standard metallic current collectors and (ii) 99.5 mAh g-1 for paper-based current collectors. Thus, the presented electrolyte has potential to become a viable candidate in paper-based and flexible battery applications. Fabrication methods, experimental procedures, and test results for the polymer gel electrolyte and batteries are presented and discussed.

High power, gel polymer lithium-ion cells with improved low temperature performance for NASA and DoD applications

NASA Technical Reports Server (NTRS)

Smart, M. C.; Ratnakumar, B. V.; Whitcanack, L. D.; Chin, K. B.; Surampudi, S.; Narayanan, S. R.; Alamgir, Mohamed; Yu, Ji-Sang; Plichta, Edward P.

2004-01-01

Both NASA and the U.S. Army have interest in developing secondary energy storage devices that are capable of meeting the demanding performance requirements of aerospace and man-portable applications. In order to meet these demanding requirements, gel-polymer electrolyte-based lithium-ion cells are being actively considered, due to their promise of providing high specific energy and enhanced safety aspects.

Electrochemical impedimetric sensor based on molecularly imprinted polymers/sol-gel chemistry for methidathion organophosphorous insecticide recognition.

PubMed

Bakas, Idriss; Hayat, Akhtar; Piletsky, Sergey; Piletska, Elena; Chehimi, Mohamed M; Noguer, Thierry; Rouillon, Régis

2014-12-01

We report here a novel method to detect methidathion organophosphorous insecticides. The sensing platform was architected by the combination of molecularly imprinted polymers and sol-gel technique on inexpensive, portable and disposable screen printed carbon electrodes. Electrochemical impedimetric detection technique was employed to perform the label free detection of the target analyte on the designed MIP/sol-gel integrated platform. The selection of the target specific monomer by electrochemical impedimetric methods was consistent with the results obtained by the computational modelling method. The prepared electrochemical MIP/sol-gel based sensor exhibited a high recognition capability toward methidathion, as well as a broad linear range and a low detection limit under the optimized conditions. Satisfactory results were also obtained for the methidathion determination in waste water samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Electric double-layer capacitors with tea waste derived activated carbon electrodes and plastic crystal based flexible gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Suleman, M.; Deraman, M.; Othman, M. A. R.; Omar, R.; Hashim, M. A.; Basri, N. H.; Nor, N. S. M.; Dolah, B. N. M.; Hanappi, M. F. Y. M.; Hamdan, E.; Sazali, N. E. S.; Tajuddin, N. S. M.; Jasni, M. R. M.

2016-08-01

We report a novel configuration of symmetrical electric double-layer capacitors (EDLCs) comprising a plastic crystalline succinonitrile (SN) based flexible polymer gel electrolyte, incorporated with sodium trifluoromethane sulfonate (NaTf) immobilised in a host polymer poly (vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP). The cost-effective activated carbon powder possessing a specific surface area (SSA) of ~ 1700 m2g-1 containing a large proportion of meso-porosity has been derived from tea waste to use as supercapacitor electrodes. The high ionic conductivity (~3.6×10-3 S cm-1 at room temperature) and good electrochemical stability render the gel polymer electrolyte film a suitable candidate for the fabrication of EDLCs. The performance of the EDLCs has been tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge studies. The performance of the EDLC cell is found to be promising in terms of high values of specific capacitance (~270 F g-1), specific energy (~ 36 Wh kg-1), and power density (~ 33 kW kg-1).

Radiological properties of normoxic polymer gel dosimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venning, A.J.; Nitschke, K.N.; Keall, P.J.

2005-04-01

The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m{sup -3}) up to 3.8% highermore » than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels.« less

Investigation of vacuum pumping on the dose response of the MAGAS normoxic polymer gel dosimeter.

PubMed

Venning, A J; Mather, M L; Baldock, C

2005-06-01

The effect of vacuum pumping on the dose response of the MAGAS polymer gel dosimeter has been investigated. A delay of several days post-manufacture before irradiation was previously necessary due to the slow oxygen scavenging of ascorbic acid. The MAGAS polymer gel dosimeter was vacuum pumped before gelation to remove dissolved oxygen. The MAGAS polymer gel dosimeter was poured into glass screw-top vials, which were irradiated at various times, post-manufacture to a range of doses. Magnetic resonance imaging techniques were used to determine the R2-dose response and R2-dose sensitivity of the MAGAS polymer gel. The results were compared with a control batch of MAGAS polymer gel that was not vacuum pumped. It was shown that vacuum pumping on the MAGAS polymer gel solution immediately prior to sealing in glass screw-top vials initially increases the R2-dose response and R2-dose sensitivity of the dosimeter. An increase in the R2-dose response and R2-dose sensitivity was observed with increasing time between manufacture and irradiation. Over the range of post-manufacture irradiation times investigated, the greatest R2-dose response and R2-dose sensitivity occurred at 96 hours.

Thiourea incorporated poly(ethylene oxide) as transparent gel polymer electrolyte for dye sensitized solar cell applications

NASA Astrophysics Data System (ADS)

Pavithra, Nagaraj; Velayutham, David; Sorrentino, Andrea; Anandan, Sambandam

2017-06-01

A new series of transparent gel polymer electrolytes are prepared by adding various weight percent of thiourea coupled with poly(ethylene oxide) for the application of dye-sensitized solar cells. Coupling of thiourea in the presence of iodine undergoes dimerization reaction to produce formamidine disulfide. Fourier Transform Infrared spectroscopy shows that the interactions of thiourea and formamidine disulfide with electronegative ether linkage of poly(ethylene oxide) results in conformational changes of gel polymer electrolytes. Electrochemical impedance spectroscopy and linear sweep voltammetry experiments reveal an increment in ionic conductivity and tri-iodide diffusion coefficient, for thiourea modified gel polymer electrolytes. Finally, the prepared electrolytes are used as a redox mediator in dye-sensitized solar cells and the photovoltaic properties were studied. Apart from transparency, the gel polymer electrolytes with thiorurea show higher photovoltaic properties compared to bare gel polymer electrolyte and a maximum photocurrent efficiency of 7.17% is achieved for gel polymer electrolyte containing 1 wt% of thiourea with a short circuit current of 11.79 mA cm-2 and open circuit voltage of 834 mV. Finally, under rear illumination, almost 90% efficiency is retained upon compared to front illumination.

Designing Solvent Exchange-Induced In Situ Forming Gel from Aqueous Insoluble Polymers as Matrix Base for Periodontitis Treatment.

PubMed

Srichan, Tharatree; Phaechamud, Thawatchai

2017-01-01

An in situ forming gel is a dosage form which is promised for site-specific therapy such as periodontal pocket of periodontitis treatment. Ethylcellulose, bleached shellac, and Eudragit RS were applied in this study as a polymeric matrix for in situ forming gel employing N-methyl pyrrolidone (NMP) as solvent. Solutions comprising ethylcellulose, bleached shellac, and Eudragit RS in NMP were evaluated for viscosity, rheology, and rate of water penetration. Ease of administration by injection was determined as the force required to expel polymeric solutions through a needle using texture analyzer. In vitro gel formation and in vitro gel degradation were conducted after injection into phosphate buffer solution pH 6.8. Ethylcellulose, bleached shellac, and Eudragit RS could form the in situ gel, in vitro. Gel viscosity and pH value depended on percentage amount of the polymer, whereas the water diffusion at early period likely relied on types of polymer. Furthermore, the solutions containing higher polymer concentration exhibited the lower degree of degradation. All the preparations were acceptable as injectable dosage forms because the applied force was lower than 50 N. All of them inhibited Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyrommonas gingivalis growth owing to antimicrobial activity of NMP which exhibited a potential use for periodontitis treatment. Moreover, the developed systems presented as the solvent exchange induced in situ forming gel and showed capability to be incorporated with the suitable antimicrobial active compounds for periodontitis treatment which should be further studied.

Topical Review: Polymer gel dosimetry

PubMed Central

Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

2010-01-01

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

Technical considerations for implementation of x-ray CT polymer gel dosimetry.

PubMed

Hilts, M; Jirasek, A; Duzenli, C

2005-04-21

Gel dosimetry is the most promising 3D dosimetry technique in current radiation therapy practice. X-ray CT has been shown to be a feasible method of reading out polymer gel dosimeters and, with the high accessibility of CT scanners to cancer hospitals, presents an exciting possibility for clinical implementation of gel dosimetry. In this study we report on technical considerations for implementation of x-ray CT polymer gel dosimetry. Specifically phantom design, CT imaging methods, imaging time requirements and gel dose response are investigated. Where possible, recommendations are made for optimizing parameters to enhance system performance. The dose resolution achievable with an optimized system is calculated given voxel size and imaging time constraints. Results are compared with MRI and optical CT polymer gel dosimetry results available in the literature.

[Polymer Gel Dosimeter].

PubMed

Hayashi, Shin-Ichiro

2017-01-01

With rapid advances being made in radiotherapy treatment, three-dimensional (3D) dose measurement techniques of great precision are required more than ever before. It is expected that 3D polymer gel dosimeters will satisfy clinical needs for an effective detector that can measure the complex 3D dose distributions. Polymer gel dosimeters are devices that utilize the radiation-induced polymerization reactions of vinyl monomers in a gel to store information about radiation dose. The 3D absorbed dose distribution can be deduced from the resulting polymer distribution using several imaging modalities, such as MRI, X-ray and optical CTs. In this article, the fundamental characteristics of polymer gel dosimeter are reviewed and some challenging keys are also suggested for the widely spread in clinical use.

Carbon Redox-Polymer-Gel Hybrid Supercapacitors

PubMed Central

Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P.M.

2016-01-01

Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances. PMID:26917470

Spatiotemporal control of synergistic gel disintegration consisting of boroxole- and glyco-based polymers via photoinduced proton transfer.

PubMed

Kotsuchibashi, Yohei; Ebara, Mitsuhiro; Sato, Takeshi; Wang, Yinan; Rajender, Rajender; Hall, Dennis G; Narain, Ravin; Aoyagi, Takao

2015-02-12

We demonstrate here a local- and remote-control of gel disintegration by using photoinduced proton transfer chemistry of photoacid generator (PAG). The gels were prepared by simply mixing two polymers, poly(N-isopropylacrylamide-co-5-methacrylamido-1,2-benzoxaborole) (P(NIPAAm-co-MAAmBO)) and poly(3-gluconamidopropyl methacrylamide) (PGAPMA) via the synergistic interaction of benzoxaborole and diol groups. The o-nitrobenzaldehyde (o-NBA) was then loaded into the gel as a PAG. The benzoxaborole-diol interaction was successfully disintegrated upon UV irradiation due to the local pH decrease inside the gel. When the gel was irradiated to a specific gel region, the synergistic interactions were disintegrated only at the exposed region. Of special interest is that the whole material eventually transitioned from gel to sol state, as the generated protons diffused gradually toward the nonilluminated region. The ability of the proposed gel-sol transition system via photoinduced proton diffusion may be beneficial for not only prompt pH changes within the gel but also the design of predictive and programmable devices for drug delivery.

Analysis of charge transport in gels containing polyoxometallates using methods of different sensitivity to migration.

PubMed

Caban, Karolina; Lewera, Adam; Zukowska, Grazyna Z; Kulesza, Pawel J; Stojek, Zbigniew; Jeffrey, Kenneth R

2006-08-04

Two methods have been used for examination of transport of charge in gels soaked with DMF and containing dissolved polyoxometallates. The first method is based on the analysis of both Cottrellian and steady-state currents and therefore is capable of giving the concentration of the electroactive redox centres and their transport (diffusion-type) coefficient. The second method provides the real diffusion coefficients, i.e. transport coefficients free of migrational influence, for both the substrate and the product of the electrode reaction. Several gels based on poly(methyl methacrylate), with charged (addition of 1-acrylamido-2-methyl-2-propanesulphonic acid to the polymerization mixture) and uncharged chains, have been used in the investigation. The ratio obtained for the diffusion coefficient (second method) and transport coefficient (first method) was smaller for the gels containing charged polymer chains than for the gels with uncharged chains. In part these changes could be explained by the contribution of migration to the transport of polyoxomatallates in the gels. However, the impact of the changes in the polymer-channel capacity at the electrode surface while the electrode process proceeds was also considered. These structural changes should affect differently the methods based on different time domains.

High resolution MR based polymer dosimetry versus film densitometry: a systematic study based on the modulation transfer function approach.

PubMed

Berg, A; Pernkopf, M; Waldhäusl, C; Schmidt, W; Moser, E

2004-09-07

Precise methods of modem radiation therapy such as intensity modulated radiotherapy (IMRT), brachytherapy (BT) and high LET irradiation allow for high dose localization in volumes of a few mm3. However, most dosimetry methods-ionization chambers, TLD arrangements or silicon detectors, for example-are not capable of detecting sub-mm dose variations or do not allow for simple dose imaging. Magnetic resonance based polymer dosimetry (MRPD) appears to be well suited to three-dimensional high resolution relative dosimetry but the spatial resolution based on a systematic modulation transfer function (MTF) approach has not yet been investigated. We offer a theoretical construct for addressing the spatial resolution in different dose imaging systems, i.e. the dose modulation transfer function (DMTF) approach, an experimental realization of this concept with a phantom and quantitative comparisons between two dosimetric systems: polymer gel and film dosimetry. Polymer gel samples were irradiated by Co-60 photons through an absorber grid which is characterized by periodic structures of different spatial period (a), the smallest one at width of a/2 = 280 microm. The modulation in dose under the grid is visualized via calibrated, high resolution, parameter-selective (T2) and dose images based on multi-echo MR imaging. The DMTF is obtained from the modulation depth of the spin-spin relaxation time (T2) after calibration. Voxel sizes below 0.04 mm3 could be achieved, which are significantly smaller than those reported in MR based dose imaging on polymer gels elsewhere, using a powerful gradient system and a highly sensitive small birdcage resonator on a whole-body 3T MR scanner. Dose modulations at 22% of maximum dose amplitude could be observed at about 2 line pairs per mm. The polymer DMTF results are compared to those of a typical clinical film-scanner system. This study demonstrates that MR based gel dosimetry at 200 microm pixel resolution might even be superior, with reference to relative spatial resolution, to the results of a standard film-scanner system offering a nominal scan resolution of 200 microm.

Structure and Properties of Polysaccharide Based BioPolymer Gels

NASA Astrophysics Data System (ADS)

Prud'Homme, Robert K.

2000-03-01

Nature uses the pyranose ring as the basic building unit for a wideclass of biopolymers. Because of their biological origin these biopolymers naturally find application as food additives, rheology modifiers. These polymers range from being rigid skeletal material, such as cellulose that resist dissolution in water, to water soluble polymers, such as guar or carrageenan. The flexibility of the basic pyranose ring structure to provide materials with such a wide range of properties comes from the specific interactions that can be engineered by nature into the structure. We will present several examples of specific interactions for these systems: hydrogen bonding, hydrophobic interactions, and specific ion interactions. The relationship between molecular interations and rheology will be emphasized. Hydrogen bonding mediated by steric interference is used to control of solubility of starch and the rheology of guar gels. A more interesting example is the hydrogen bonding induced by chemical modification in konjac glucomannan that results in a gel that melts upon cooling. Hydrogen bonding interactions in xanthan lead to gel formation at very low polymer concentrations which is a result of the fine tuning of the polymer persistence length and total contour length. Given the function of xanthan in nature its molecular architecture has been optimized. Hydrophobic interactions in methylcellulose show a reverse temperature dependence arising from solution entropy. Carrageenan gelation upon the addition of specific cations will be addressed to show the interplay of polymer secondary structure on chemical reactivity. And finally the cis-hydroxyls on galactomannans permit crosslinking by a variety of metal ions some of which lead to "living gels" and some of which lead to permanently crosslinked networks.

Polymeric electrolytes based on hydrosilyation reactions

DOEpatents

Kerr, John Borland [Oakland, CA; Wang, Shanger [Fairfield, CA; Hou, Jun [Painted Post, NY; Sloop, Steven Edward [Berkeley, CA; Han, Yong Bong [Berkeley, CA; Liu, Gao [Oakland, CA

2006-09-05

New polymer electrolytes were prepared by in situ cross-linking of allyl functional polymers based on hydrosilation reaction using a multifunctional silane cross-linker and an organoplatinum catalyst. The new cross-linked electrolytes are insoluble in organic solvent and show much better mechanical strength. In addition, the processability of the polymer electrolyte is maintained since the casting is finished well before the gel formation.

"JCE" Classroom Activity Connections: NaCl or CaCl[subscript 2], Smart Polymer Gel Tells More

ERIC Educational Resources Information Center

Chen, Yueh-Huey; Lin, Jia-Ying; Wang, Yu-Chen; Yaung, Jing-Fun

2010-01-01

This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl[subscript 2] (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl[subscript 2] both collapse the swollen polymer gels. The gel contracted by NaCl reswells…

Performance improvement of gel- and solid-state dye-sensitized solar cells by utilization the blending effect of poly (vinylidene fluoride-co-hexafluropropylene) and poly (acrylonitrile-co-vinyl acetate) co-polymers

NASA Astrophysics Data System (ADS)

Venkatesan, Shanmugam; Obadja, Nesia; Chang, Ting-Wei; Chen, Li-Tung; Lee, Yuh-Lang

2014-12-01

Poly (vinylidene fluoride-co-hexafluropropylene) (PVDF-HFP) and poly (acrylonitrile-co-vinyl acetate) (PAN-VA) are used as gelator to prepare gel- and solid-state polymer electrolytes for dye sensitized solar cells (DSSCs) applications. The electrolytes prepared using PVDF-HFP have higher conductivities than those prepared using PAN-VA. In blended polymers, the conductivities of the electrolytes increase with increasing composition of PVDF-HFP; at 75% PVDF-HFP, conductivity of the blended polymer surpassed that of pure polymers. It is also found that the viscosity of the electrolyte prepared by PAN-VA (1.2 kPaS) is much lower than that by PVDF-HFP (11 kPaS). Therefore, increasing PAN-VA composition can decrease the viscosity of the electrolyte, improving the penetration of electrolytes in the TiO2 matrix. By controlling the ratio of PVDF-HFP/PAN-VA, the conductivity and viscosity of the electrolyte can be regulated and an optimal ratio based on the conversion efficiency of the gel- and solid state DSSCs is obtained at the ratio of 3/1. The highest efficiency achieved by the gel- and solid-state cells using the blending polymers are 6.3% and 4.88%, respectively, which are higher than those prepared using pure polymers (5.53% and 4.56%, respectively). The introduction of TiO2 fillers to the solid electrolyte can further increase the cell efficiency to 5.34%.

Synthesis, characterisation and phase transition behaviour of temperature-responsive physically crosslinked poly (N-vinylcaprolactam) based polymers for biomedical applications.

PubMed

Halligan, Shane C; Dalton, Maurice B; Murray, Kieran A; Dong, Yixiao; Wang, Wenxin; Lyons, John G; Geever, Luke M

2017-10-01

Poly (N-vinylcaprolactam) (PNVCL) is a polymer which offers superior characteristics for various potential medical device applications. In particular it offers unique thermoresponsive capabilities, which fulfils the material technology constraints required in targeted drug delivery applications. PNVCL phase transitions can be tailored in order to suit the requirements of current and next generation devices, by modifying the contents with regard to the material composition and aqueous polymer concentration. In this study, physically crosslinked Poly (N-vinylcaprolactam)-Vinyl acetate (PNVCL-VAc) copolymers were prepared by photopolymerisation. The structure of the polymers was established by Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography. The polymers were further characterised using differential scanning calorimetry and swelling studies. Determination of the LCST of the polymers in aqueous solution was achieved by employing four techniques; cloud point, UV-spectrometry, differential scanning calorimetry and rheometry. Sol-gel transition was established using tube inversion method and rheological analysis. This study was conducted to determine the characteristics of PNVCL with the addition of VAc, and to establish the effects on the phase transition. The PNVCL based polymers exhibited a decrease in the LCST as the composition of VAc increased. Sol-gel transition could be controlled by altering the monomeric feed ratio and polymer concentration in aqueous milieu. Importantly all copolymers (10wt% in solution) underwent gelation between 33.6 and 35.9°C, and based on this and the other materials properties recorded in this study, these novel copolymers have potential for use as injectable in situ forming drug delivery systems for targeted drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

Availability of a containerless polymer gel detector and a gelatin container

NASA Astrophysics Data System (ADS)

Tominaga, Takahiro; Yoshioka, Munenori; Hayashi, Shin-ichiro; Usui, Shuji; Tada, Mitsutoshi

2015-01-01

We considered an availability of the polymer gel detector without container but with a plastic wrap under assumption of the low oxygen transmissivity of a sheet of plastic wrap. And a gelatin container was also examined for a gel detector. These samples can be made easily and this containerless polymer gel detector well works without any artifacts by means of wrapping with a thin plastic sheet. Nevertheless, there is still room for improvement on preventing oxygen contamination. Combination with a gelatin container and a polymer gel detector and/or Gafchromic films has a various potential for extension of 3D dosimetry.

Polymer architecture of magnetic gels: a review

NASA Astrophysics Data System (ADS)

Weeber, Rudolf; Hermes, Melissa; Schmidt, Annette M.; Holm, Christian

2018-02-01

In this review article, we provide an introduction to ferrogels, i.e. polymeric gels with embedded magnetic particles. Due to the interplay between magnetic and elastic properties of these materials, they are promising candidates for engineering and biomedical applications such as actuation and controlled drug release. Particular emphasis will be put on the polymer architecture of magnetic gels since it controls the degrees of freedom of the magnetic particles in the gel, and it is important for the particle-polymer coupling determining the mechanisms available for the gel deformation in magnetic fields. We report on the different polymer architectures that have been realized so far, and provide an overview of synthesis strategies and experimental techniques for the characterization of these materials. We further focus on theoretical and simulational studies carried out on magnetic gels, and highlight their contributions towards understanding the influence of the gels’ polymer architecture.

Assessment of the effects of CT dose in averaged x-ray CT images of a dose-sensitive polymer gel

NASA Astrophysics Data System (ADS)

Kairn, T.; Kakakhel, M. B.; Johnston, H.; Jirasek, A.; Trapp, J. V.

2015-01-01

The signal-to-noise ratio achievable in x-ray computed tomography (CT) images of polymer gels can be increased by averaging over multiple scans of each sample. However, repeated scanning delivers a small additional dose to the gel which may compromise the accuracy of the dose measurement. In this study, a NIPAM-based polymer gel was irradiated and then CT scanned 25 times, with the resulting data used to derive an averaged image and a "zero-scan" image of the gel. Comparison between these two results and the first scan of the gel showed that the averaged and zero-scan images provided better contrast, higher contrast-to- noise and higher signal-to-noise than the initial scan. The pixel values (Hounsfield units, HU) in the averaged image were not noticeably elevated, compared to the zero-scan result and the gradients used in the linear extrapolation of the zero-scan images were small and symmetrically distributed around zero. These results indicate that the averaged image was not artificially lightened by the small, additional dose delivered during CT scanning. This work demonstrates the broader usefulness of the zero-scan method as a means to verify the dosimetric accuracy of gel images derived from averaged x-ray CT data.

Polymer Electrolytes for Lithium/Sulfur Batteries

PubMed Central

Zhao, Yan; Zhang, Yongguang; Gosselink, Denise; Doan, The Nam Long; Sadhu, Mikhail; Cheang, Ho-Jae; Chen, Pu

2012-01-01

This review evaluates the characteristics and advantages of employing polymer electrolytes in lithium/sulfur (Li/S) batteries. The main highlights of this study constitute detailed information on the advanced developments for solid polymer electrolytes and gel polymer electrolytes, used in the lithium/sulfur battery. This includes an in-depth analysis conducted on the preparation and electrochemical characteristics of the Li/S batteries based on these polymer electrolytes. PMID:24958296

Soft, Comfortable Polymer Dry Electrodes for High Quality ECG and EEG Recording

PubMed Central

Chen, Yun-Hsuan; de Beeck, Maaike Op; Vanderheyden, Luc; Carrette, Evelien; Mihajlović, Vojkan; Vanstreels, Kris; Grundlehner, Bernard; Gadeyne, Stefanie; Boon, Paul; Van Hoof, Chris

2014-01-01

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes offering high user comfort, since they are fabricated from EPDM rubber containing various additives for optimum conductivity, flexibility and ease of fabrication. The electrode impedance is measured on phantoms and human skin. After optimization of the polymer composition, the skin-electrode impedance is only ∼10 times larger than that of gel electrodes. Therefore, these electrodes are directly capable of recording strong biopotential signals such as ECG while for low-amplitude signals such as EEG, the electrodes need to be coupled with an active circuit. EEG recordings using active polymer electrodes connected to a clinical EEG system show very promising results: alpha waves can be clearly observed when subjects close their eyes, and correlation and coherence analyses reveal high similarity between dry and gel electrode signals. Moreover, all subjects reported that our polymer electrodes did not cause discomfort. Hence, the polymer-based dry electrodes are promising alternatives to either rigid dry electrodes or conventional gel electrodes. PMID:25513825

Superabsorbing gel for actinide, lanthanide, and fission product decontamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaminski, Michael D.; Mertz, Carol J.

The present invention provides an aqueous gel composition for removing actinide ions, lanthanide ions, fission product ions, or a combination thereof from a porous surface contaminated therewith. The composition comprises a polymer mixture comprising a gel forming cross-linked polymer and a linear polymer. The linear polymer is present at a concentration that is less than the concentration of the cross-linked polymer. The polymer mixture is at least about 95% hydrated with an aqueous solution comprising about 0.1 to about 3 percent by weight (wt %) of a multi-dentate organic acid chelating agent, and about 0.02 to about 0.6 molar (M)more » carbonate salt, to form a gel. When applied to a porous surface contaminated with actinide ions, lanthanide ions, and/or other fission product ions, the aqueous gel absorbs contaminating ions from the surface.« less

Selective and Responsive Nanopore-Filled Membranes

DTIC Science & Technology

2011-03-14

Materials Science and Engineering Poster Competition 15. Chen, H.; Elabd, Y.A. Ionic Liquid Polymers: Electrospinning and Solution Properties. Fall...hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project include (1) synthesizing stimuli...on polymer-polymer nanocomposites of hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project

Chemomechanical synchronization in heterogeneous self-oscillating gels

NASA Astrophysics Data System (ADS)

Yashin, Victor V.; Balazs, Anna C.

2008-04-01

Using computational modeling, we introduce patches of self-oscillating gels undergoing the Belousov-Zhabotinsky (BZ) reaction into a nonreactive polymer network and thereby demonstrate how these BZ gels can be harnessed to impart remarkable functionality to the entire system. By first focusing on two adjacent patches of BZ gels, we show that the patches’ oscillations can become synchronized in phase or out of phase, with the oscillation frequency depending on the synchronization mode and the spatial separation between these domains. We then apply these results to an array of five adjacent BZ patches and by varying the distance between these pieces, we dramatically alter the dynamical behavior of the patterned gel. For example, the sample can be made to exhibit a unidirectional traveling wave or display a concerted expansion and contraction, properties that are valuable for creating gel-based devices, such as micropumps and microactuators. The findings point to a “modular” design approach, which can impart different functionality simply by arranging identical pieces of BZ gels into distinct spatial arrangements within a polymer matrix.

Recognition-Mediated Hydrogel Swelling Controlled by Interaction with a Negative Thermoresponsive LCST Polymer.

PubMed

Belal, Khaled; Stoffelbach, François; Lyskawa, Joël; Fumagalli, Matthieu; Hourdet, Dominique; Marcellan, Alba; Smet, Lieselot De; de la Rosa, Victor R; Cooke, Graeme; Hoogenboom, Richard; Woisel, Patrice

2016-11-02

Most polymeric thermoresponsive hydrogels contract upon heating beyond the lower critical solution temperature (LCST) of the polymers used. Herein, we report a supramolecular hydrogel system that shows the opposite temperature dependence. When the non-thermosesponsive hydrogel NaphtGel, containing dialkoxynaphthalene guest molecules, becomes complexed with the tetra cationic macrocyclic host CBPQT 4+ , swelling occurred as a result of host-guest complex formation leading to charge repulsion between the host units, as well as an osmotic contribution of chloride counter-ions embedded in the network. The immersion of NaphtGel in a solution of poly(N-isopropylacrylamide) with tetrathiafulvalene (TTF) end groups complexed with CBPQT 4+ induced positive thermoresponsive behaviour. The LCST-induced dethreading of the polymer-based pseudorotaxane upon heating led to transfer of the CBPQT 4+ host and a concomitant swelling of NaphtGel. Subsequent cooling led to reformation of the TTF-based host-guest complexes in solution and contraction of the hydrogel. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Sol-Gel Entrapped Levonorgestrel Antibodies: Activity and Structural Changes as a Function of Different Polymer Formats

PubMed Central

Shalev, Moran; Miriam, Altstein

2011-01-01

The paper describes development of a sol-gel based immunoaffinity method for the steroid hormone levonorgestrel (LNG) and the effects of changes in the sol-gel matrix format on the activity of the entrapped antibodies (Abs) and on matrix structure. The best sol-gel format for Ab entrapment was found to be a tetramethoxysilane (TMOS) based matrix at a TMOS:water ratio of 1:8, containing 10% polyethylene glycol (PEG) of MW 0.4 kDa. Addition of higher percentages of PEG or a higher MW PEG did not improve activity. No activity was obtained with a TMOS:water ratio of 1:12, most likely because of the very dense polymer that resulted from these polymerization conditions. Only minor differences in the non-specific binding were obtained with the various formats. TMOS was found to be more effective than tetrakis (2-hydroxyethyl)orthosilicate (THEOS) for entrapment of anti-levonorgestrel (LNG) Abs. However, aging the THEOS-based sol-gel for a few weeks at 4 °C stabilized the entrapped Abs and increased its binding capacity. Confocal fluorescent microscopy with fluorescein isothiocyanate (FITC) labeled immunoglobulines (IgGs) entrapped in the sol-gel matrix showed that the entrapped Abs were distributed homogenously within the gel. Scanning electron microscopy (SEM) images have shown the diverse structures of the various sol-gel formats and precursors. PMID:28880001

Effect of hydrophobic inclusions on polymer swelling kinetics studied by magnetic resonance imaging.

PubMed

Gajdošová, Michaela; Pěček, Daniel; Sarvašová, Nina; Grof, Zdeněk; Štěpánek, František

2016-03-16

The rate of drug release from polymer matrix-based sustained release formulations is often controlled by the thickness of a gel layer that forms upon contact with dissolution medium. The effect of formulation parameters on the kinetics of elementary rate processes that contribute to gel layer formation, such as water ingress, polymer swelling and erosion, is therefore of interest. In the present work, gel layer formation has been investigated by magnetic resonance imaging (MRI), which is a non-destructive method allowing direct visualization of effective water concentration inside the tablet and its surrounding. Using formulations with Levetiracetam as the active ingredient, HPMC as a hydrophilic matrix former and carnauba wax (CW) as a hydrophobic component in the matrix system, the effect of different ratios of these two ingredients on the kinetics of gel formation (MRI) and drug release (USP 4 like dissolution test) has been investigated and interpreted using a mathematical model. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydroxyapatite scaffolds processed using a TBA-based freeze-gel casting/polymer sponge technique.

PubMed

Yang, Tae Young; Lee, Jung Min; Yoon, Seog Young; Park, Hong Chae

2010-05-01

A novel freeze-gel casting/polymer sponge technique has been introduced to fabricate porous hydroxyapatite scaffolds with controlled "designer" pore structures and improved compressive strength for bone tissue engineering applications. Tertiary-butyl alcohol (TBA) was used as a solvent in this work. The merits of each production process, freeze casting, gel casting, and polymer sponge route were characterized by the sintered microstructure and mechanical strength. A reticulated structure with large pore size of 180-360 microm, which formed on burn-out of polyurethane foam, consisted of the strut with highly interconnected, unidirectional, long pore channels (approximately 4.5 microm in dia.) by evaporation of frozen TBA produced in freeze casting together with the dense inner walls with a few, isolated fine pores (<2 microm) by gel casting. The sintered porosity and pore size generally behaved in an opposite manner to the solid loading, i.e., a high solid loading gave low porosity and small pore size, and a thickening of the strut cross section, thus leading to higher compressive strengths.

Optimizing photovoltaic performance in CuInS 2 and CdS quantum dot-sensitized solar cells by using an agar-based gel polymer electrolyte

DOE PAGES

Raphael, E.; Jara, D. H.; Schiavon, M. A.

2017-01-19

Quantum dot-sensitized solar cells (QDSSCs) offer new opportunities to address the clean energy challenge, being one of the top candidates for third generation photovoltaics. Like dye-sensitized solar cells (DSSCs), QDSSCs normally use liquid electrolytes that suffer from issues such as evaporation or leakage. In this study a gel polysulfide electrolyte was prepared containing a natural polymer, agar, and was used as a quasi-solid-state electrolyte in solar cells to replace the conventional liquid electrolytes. This gel electrolyte shows almost the same conductivity as the liquid one. The solar cells were fabricated using CuInS 2 quantum dots (QDs), previously synthesized, deposited onmore » TiO 2 photoanodes by electrophoretic deposition (EPD). CdS was deposited on TiO 2 by successive ionic layer adsorption and reaction (SILAR). Reduced graphene oxide (RGO)–Cu 2S, brass, and thin film CuxS were used as counter electrodes. Compared to a liquid polysulfide water based electrolyte, solar cells based on CuInS 2 and CdS using gel polymer electrolyte (GPE) exhibit greater incident photon to current conversion efficiency (IPCE = 51.7% at 520 nm and 72.7% at 440 nm), photocurrent density (J sc = 10.75 and 13.51 mA cm -2), and power conversion efficiency (η = 2.97 and 2.98%) while exhibiting significantly enhanced stability. The solar cells employing the agar-based gel polymeric electrolyte are about a factor of 0.20 more stable than using a liquid electrolyte. The higher photovoltaic performance is due to the good conductivity and high wettability as well as the superior permeation capability of the gel electrolyte into the mesoporous matrix of a TiO 2 film« less

Optimizing photovoltaic performance in CuInS 2 and CdS quantum dot-sensitized solar cells by using an agar-based gel polymer electrolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raphael, E.; Jara, D. H.; Schiavon, M. A.

Quantum dot-sensitized solar cells (QDSSCs) offer new opportunities to address the clean energy challenge, being one of the top candidates for third generation photovoltaics. Like dye-sensitized solar cells (DSSCs), QDSSCs normally use liquid electrolytes that suffer from issues such as evaporation or leakage. In this study a gel polysulfide electrolyte was prepared containing a natural polymer, agar, and was used as a quasi-solid-state electrolyte in solar cells to replace the conventional liquid electrolytes. This gel electrolyte shows almost the same conductivity as the liquid one. The solar cells were fabricated using CuInS 2 quantum dots (QDs), previously synthesized, deposited onmore » TiO 2 photoanodes by electrophoretic deposition (EPD). CdS was deposited on TiO 2 by successive ionic layer adsorption and reaction (SILAR). Reduced graphene oxide (RGO)–Cu 2S, brass, and thin film CuxS were used as counter electrodes. Compared to a liquid polysulfide water based electrolyte, solar cells based on CuInS 2 and CdS using gel polymer electrolyte (GPE) exhibit greater incident photon to current conversion efficiency (IPCE = 51.7% at 520 nm and 72.7% at 440 nm), photocurrent density (J sc = 10.75 and 13.51 mA cm -2), and power conversion efficiency (η = 2.97 and 2.98%) while exhibiting significantly enhanced stability. The solar cells employing the agar-based gel polymeric electrolyte are about a factor of 0.20 more stable than using a liquid electrolyte. The higher photovoltaic performance is due to the good conductivity and high wettability as well as the superior permeation capability of the gel electrolyte into the mesoporous matrix of a TiO 2 film« less

New composite thixotropic hydrogel composed of a polymer hydrogelator and a nanosheet

NASA Astrophysics Data System (ADS)

Ohsedo, Yutaka; Oono, Masashi; Saruhashi, Kowichiro; Watanabe, Hisayuki; Miyamoto, Nobuyoshi

2017-12-01

A composite gel composed of a water-soluble aromatic polyamide hydrogelator and the nanosheet Laponite®, a synthetic layered silicate, was produced and found to exhibit thixotropic behaviour. Whereas the composite gel contains the gelator at the same concentration as the molecular gel made by the gelator only, the composite gel becomes a softer thixotropic gel compared to the molecular gel made by the gelator only. The reason for this could be that bundles of polymer gelator may be loosened and the density of the polymer network increased in the presence of Laponite.

New composite thixotropic hydrogel composed of a polymer hydrogelator and a nanosheet

PubMed Central

Oono, Masashi; Saruhashi, Kowichiro; Watanabe, Hisayuki; Miyamoto, Nobuyoshi

2017-01-01

A composite gel composed of a water-soluble aromatic polyamide hydrogelator and the nanosheet Laponite®, a synthetic layered silicate, was produced and found to exhibit thixotropic behaviour. Whereas the composite gel contains the gelator at the same concentration as the molecular gel made by the gelator only, the composite gel becomes a softer thixotropic gel compared to the molecular gel made by the gelator only. The reason for this could be that bundles of polymer gelator may be loosened and the density of the polymer network increased in the presence of Laponite. PMID:29308249

Dosimetric characteristics of PASSAG as a new polymer gel dosimeter with negligible toxicity

NASA Astrophysics Data System (ADS)

Farhood, Bagher; Abtahi, Seyed Mohammad Mahdi; Geraily, Ghazale; Ghorbani, Mehdi; Mahdavi, Seied Rabi; Zahmatkesh, Mohammad Hasan

2018-06-01

Despite many advantages of polymer gel dosimeters, their clinical use is only not realized now. Toxicity of polymer gel dosimeters can be considered as one of their main limitations for use in routine clinical applications. In the current study, a new polymer gel dosimeter is introduced with negligible toxicity. For this purpose, 2-Acrylamido-2-Methy-1-PropaneSulfonic acid (AMPS) sodium salt monomer was replaced instead of acrylamide monomer used in PAGAT gel dosimeter by using %6 T and %50 C to the gel formula and the new formulation is called PASSAG (Poly AMPS Sodium Salt and Gelatin) polymer gel dosimeter. The irradiation of gel dosimeters was carried out using a Co-60 therapy machine. MRI technique was used to quantify the dose responses of the PASSAG gel dosimeter. Then, the MRI responses (R2) of the gel dosimeter was analyzed at different dose values, post-irradiation times, and scanning temperatures. The results showed that the new gel formulation has a negligible toxicity and it is also eco-friendly. In addition, carcinogenicity and genetic toxicity tests are negative for the monomer used in PASSAG. The radiological properties of PASSAG gel dosimeter showed that this substance can be considered as a soft tissue/water equivalent material. Furthermore, dosimetric evaluation of the new polymer gel dosimeter revealed an excellent linear R2-dose response in the evaluated dose range (0-15 Gy). The R2-dose sensitivity and dose resolution of PASSAG gel dosimeter were 0.081 s-1Gy-1 (in 0-15 Gy dose range) and 1 Gy (in 0-10 Gy dose range), respectively. Moreover, it was shown that the R2-dose sensitivity and dose resolution of the new gel dosimeter improves over time after irradiation. It was also found that the R2 response of the PASSAG gel dosimeter has less dependency to the 18, 20, and 24 °C scanning temperature in comparison to that of room temperature (22 °C).

Thermosensitive and mucoadhesive in situ gel based on poloxamer as new carrier for rectal administration of nimesulide.

PubMed

Yuan, Yuan; Cui, Ying; Zhang, Li; Zhu, Hui-Ping; Guo, Yi-Sha; Zhong, Bo; Hu, Xia; Zhang, Ling; Wang, Xiao-Hui; Chen, Li

2012-07-01

Poloxamer 407 has excellent thermo-sensitive gelling properties. Nevertheless, these gels possess inadequate poor bioadhesiveness and high permeability to water, which limited its' application as a thermoresponsive matrix. The main aim of the present investigation was to develop thermosensitive and mucoadhesive rectal in situ gel of nimesulide (NM) by using mucoadhesive polymers such as sodium alginate (Alg-Na) and HPMC. These gels were prepared by addition of mucoadhesive polymers (0.5%) to the formulations of thermosensitive gelling solution containing poloxamer 407 (18%) and nimesulide (2.0%). Polyethylene glycol (PEG) was used to modify gelation temperature and drug release properties. The gelation temperature and drug release rate of the prepared in situ gels were evaluated. Gelation temperature was significantly increased with incorporation of nimesulide (2.0%) in the poloxamer solution, while the addition of the mucoadhesive polymers played a reverse role on gelation temperature. The addition of PEG polymers increased the gelation temperature and the drug release rate. Among the formulations examined, the poloxamer 407/nimesulide/sodium alginate/PEG 4000 (18/2.0/0.5/1.2%) exhibited the appropriate gelation temperature, acceptable drug release rate and rectal retention at the administration site. Furthermore, the micrographic results showed that in situ gel, given at the dose of 20mg/kg, was safe for no mucosa irritation. In addition, it resulted in significantly higher initial serum concentrations, C(max) and AUC of NM compared to the solid suppository. Copyright © 2012 Elsevier B.V. All rights reserved.

PEO based polymer composite with added acetamide, NaI/I2 as gel polymer electrolyte for dye sensitized solar cell applications

NASA Astrophysics Data System (ADS)

Narasimha Rao, B.; Padma suvarna, R.; Giribabu, L.; Raghavender, M.; kumar, V. Ramesh

2018-02-01

Poly (ethylene oxide) (PEO) based gel polymer electrolytes (GPEs) with added acetamide, NaI/I2 have been prepared for dye-sensitized solar cells application (DSSC). The Dye-sensitized solar cell investigated the performance of the optimized gel polymer electrolyte. GPEs synthesized by adding up of acetamide with different wt% in poly (ethylene oxide) (PEO) and poly (ethylene glycol) dimethyl ether (PEGDME) with NaI/I2. A maximum power conversion efficiency of 5.92% is achieved for PEO/PEGDME with 10 wt% acetamide in the photovoltaic performance under 100 mW/cm2 illumination and it exhibits maximum ionic conductivity (σ = 2.81×10-3 S/cm) among all electrolytes, compared to PEO without acetamide (η = 4.35%). The gain in open circuit voltage (Voc) was observed for GPEs due to the decrease in the recombination effect and electron lifetime increases by the addition of acetamide on the PEO. The fill factor (FF) is increased due to the growth in the ionic conductivity and amorphous nature of the GPE increases by the addition of acetamide on the PEO.

A study of normoxic polymer gel using monomer 2-hydroxyethyl methacrylate (HEMA)

NASA Astrophysics Data System (ADS)

Ishak, Siti Atiqah; Mustafa, Iskandar Shahrim; Rahman, Azhar Abdul; Moktar, Mohd; Min, Ung Ngie

2015-04-01

The aim of this study is to determine the sensitivity of HEMA-polymer gel mixture consist of monomer 2-hydroxyethyl methacrylate (HEMA) with different types of composition. Several composition of HEMA-polymer gel were fabricated and the gels were irradiated with radiation dose between 10 cGy to 100cGy by using x-ray machine and 100 cGy to 1400 cGy by using 6 MV photon beam energy of linear accelerator. The degree of polymerization was evaluated by using magnetic resonance imaging (MRI) with dependence of R2-dose response. Polymer gel consists of cross-linker, anti-oxidant Tetrakis(Hydroxymethyl)phosphonium chloride solution (THPC) and oxygen scavenger hydroquinone shows a stable sensitivity with highest dose dependency. Besides, the results shows the stage polymerization consist of induction, propagation, termination, and chain transfer were dependence with type of chemical mixture and radiation dose. Thus, normoxic HEMA-polymer gel with the different gel formulations can have a better dose resolution and an appropriate recipe must be selected to increase of the sensitivity required and the stability of the dosimeter.

A study of normoxic polymer gel using monomer 2-hydroxyethyl methacrylate (HEMA)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishak, Siti Atiqah; Mustafa, Iskandar Shahrim; Rahman, Azhar Abdul

2015-04-24

The aim of this study is to determine the sensitivity of HEMA-polymer gel mixture consist of monomer 2-hydroxyethyl methacrylate (HEMA) with different types of composition. Several composition of HEMA-polymer gel were fabricated and the gels were irradiated with radiation dose between 10 cGy to 100cGy by using x-ray machine and 100 cGy to 1400 cGy by using 6 MV photon beam energy of linear accelerator. The degree of polymerization was evaluated by using magnetic resonance imaging (MRI) with dependence of R2-dose response. Polymer gel consists of cross-linker, anti-oxidant Tetrakis(Hydroxymethyl)phosphonium chloride solution (THPC) and oxygen scavenger hydroquinone shows a stable sensitivitymore » with highest dose dependency. Besides, the results shows the stage polymerization consist of induction, propagation, termination, and chain transfer were dependence with type of chemical mixture and radiation dose. Thus, normoxic HEMA-polymer gel with the different gel formulations can have a better dose resolution and an appropriate recipe must be selected to increase of the sensitivity required and the stability of the dosimeter.« less

Chemotaxis of active, self-oscillating polymer gels in solution

NASA Astrophysics Data System (ADS)

Dayal, Pratyush; Bhattacharya, Amitabh; Kuksenok, Olga; Balazs, Anna C.

2012-02-01

Fighting, fleeing and feeding are hallmarks of all living things; all these activities require some degree of mobility. Herein, we undertake the first computational study of self-oscillating polymer gels and show that this system can ``communicate'' to undergo a biomimetic, collective response to small-scale chemical changes. In this study we harness unique properties of polymer gels that undergo oscillatory Belousov-Zhabotinsky (BZ) reaction. The activator for the reaction is generated within these BZ cilia and diffuses between the neighboring gels. In order to simulate the dynamics of the BZ gels in surrounding fluid we have developed a nonlinear hybrid 3D model which captures the elasto-dynamics of polymer gel and diffusive exchange of BZ reagents between the gel and the fluid. We illustrate that multiple BZ gels in solution exhibit a distinct form of chemotaxis, moving towards the highest activator concentration in the solution. Similar ability to sense and move in response to chemical gradients constitutes a vital function in simple organisms, enabling them to find food and flee from poisons.

SU-E-T-753: Three-Dimensional Dose Distributions of Incident Proton Particle in the Polymer Gel Dosimeter and the Radiochromic Gel Dosimeter: A Simulation Study with MCNP Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, M; Kim, G; Ji, Y

Purpose: The purpose of this study is to estimate the three-dimensional dose distributions in the polymer and the radiochromic gel dosimeter, and to identify the detectability of both gel dosimeters by comparing with the water phantom in case of irradiating the proton particles. Methods: The normoxic polymer gel and the LCV micelle radiochromic gel were used in this study. The densities of polymer and the radiochromic gel dosimeter were 1.024 and 1.005 g/cm{sup 3}, respectively. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX, Los Alamos National Laboratory). Themore » shape of phantom irradiated by proton particles was a hexahedron with the dimension of 12.4 × 12.4 × 15.0 cm{sup 3}. The energies of proton beam were 50, 80, and 140 MeV energies were directed to top of the surface of phantom. The cross-sectional view of proton dose distribution in both gel dosimeters was estimated with the water phantom and evaluated by the gamma evaluation method. In addition, the absorbed dose(Gy) was also calculated for evaluating the proton detectability. Results: The evaluation results show that dose distributions in both gel dosimeters at intermediated section and Bragg-peak region are similar with that of the water phantom. At entrance section, however, inconsistencies of dose distribution are represented, compared with water. The relative absorbed doses in radiochromic and polymer gel dosimeter were represented to be 0.47 % and 2.26 % difference, respectively. These results show that the radiochromic gel dosimeter was better matched than the water phantom in the absorbed dose evaluation. Conclusion: The polymer and the radiochromic gel dosimeter show similar characteristics in dose distributions for the proton beams at intermediate section and Bragg-peak region. Moreover the calculated absorbed dose in both gel dosimeters represents similar tendency by comparing with that in water phantom.« less

Novel chronotherapeutic rectal aminophylline delivery system for therapy of asthma.

PubMed

Shiohira, Hideo; Fujii, Makiko; Koizumi, Naoya; Kondoh, Masuo; Watanabe, Yoshiteru

2009-09-08

The aim of this study was to develop a new chronotherapeutic pharmaceutical preparation as a sustained-release suppository for prevention and therapeutic use against bronchial asthma in the early morning. Sustained-release hollow-type (SR-HT) suppositories using sodium alginate (Alg-Na), sodium polyacrylate (PANa) or polyacrylate-PANa co-polymer (PA-PANa) as gelling polymers (gel agent) were prepared and pharmaceutical characteristics of these suppositories were investigated. Type A SR-HT suppositories comprised a suppository shell prepared with oleaginous base and containing aminophylline only or aminophylline with Alg-Na or PANa in the cavity (hollow space). Type B SR-HT suppositories comprised a suppository shell prepared with oleaginous base and gel agent (30%), with aminophylline in the hollow space. In drug-release studies, the acrylate polymer-containing suppositories showed linearity of delayed release rate, providing significantly decreased the highest concentration of theophylline in plasma (C(max)) and delayed the time required to reach C(max) (t(max)) and the mean residence time (MRT) after rectal administrated in rabbits. In particular, suppositories containing PA-PANa maintained significantly higher theophylline concentrations than control suppositories at 12h after rectal administration. Furthermore, histopathological examination indicated that these suppositories using acrylate polymers did not result in rectal lesions. The SR-HT suppository, particularly using PA-PANa as a gel agent, may thus be useful against nocturnal symptoms of asthma. In this study, we confirmed new formulation of sustained-release suppository for chronotherapy of theophylline using oily base material in combination with polymer such as PA-PANa. The hollow-type suppository containing oleaginous base and hydrophilic polymer in the shell could be useful device for rectal administration of various drugs with prolongation of plasma concentration.

Honeycomb-like porous gel polymer electrolyte membrane for lithium ion batteries with enhanced safety.

PubMed

Zhang, Jinqiang; Sun, Bing; Huang, Xiaodan; Chen, Shuangqiang; Wang, Guoxiu

2014-08-29

Lithium ion batteries have shown great potential in applications as power sources for electric vehicles and large-scale energy storage. However, the direct uses of flammable organic liquid electrolyte with commercial separator induce serious safety problems including the risk of fire and explosion. Herein, we report the development of poly(vinylidene difluoride-co-hexafluoropropylene) polymer membranes with multi-sized honeycomb-like porous architectures. The as-prepared polymer electrolyte membranes contain porosity as high as 78%, which leads to the high electrolyte uptake of 86.2 wt%. The PVDF-HFP gel polymer electrolyte membranes exhibited a high ionic conductivity of 1.03 mS cm(-1) at room temperature, which is much higher than that of commercial polymer membranes. Moreover, the as-obtained gel polymer membranes are also thermally stable up to 350 °C and non-combustible in fire (fire-proof). When applied in lithium ion batteries with LiFePO4 as cathode materials, the gel polymer electrolyte demonstrated excellent electrochemical performances. This investigation indicates that PVDF-HFP gel polymer membranes could be potentially applicable for high power lithium ion batteries with the features of high safety, low cost and good performance.

Honeycomb-like porous gel polymer electrolyte membrane for lithium ion batteries with enhanced safety

NASA Astrophysics Data System (ADS)

Zhang, Jinqiang; Sun, Bing; Huang, Xiaodan; Chen, Shuangqiang; Wang, Guoxiu

2014-08-01

Lithium ion batteries have shown great potential in applications as power sources for electric vehicles and large-scale energy storage. However, the direct uses of flammable organic liquid electrolyte with commercial separator induce serious safety problems including the risk of fire and explosion. Herein, we report the development of poly(vinylidene difluoride-co-hexafluoropropylene) polymer membranes with multi-sized honeycomb-like porous architectures. The as-prepared polymer electrolyte membranes contain porosity as high as 78%, which leads to the high electrolyte uptake of 86.2 wt%. The PVDF-HFP gel polymer electrolyte membranes exhibited a high ionic conductivity of 1.03 mS cm-1 at room temperature, which is much higher than that of commercial polymer membranes. Moreover, the as-obtained gel polymer membranes are also thermally stable up to 350°C and non-combustible in fire (fire-proof). When applied in lithium ion batteries with LiFePO4 as cathode materials, the gel polymer electrolyte demonstrated excellent electrochemical performances. This investigation indicates that PVDF-HFP gel polymer membranes could be potentially applicable for high power lithium ion batteries with the features of high safety, low cost and good performance.

Honeycomb-like porous gel polymer electrolyte membrane for lithium ion batteries with enhanced safety

PubMed Central

Zhang, Jinqiang; Sun, Bing; Huang, Xiaodan; Chen, Shuangqiang; Wang, Guoxiu

2014-01-01

Lithium ion batteries have shown great potential in applications as power sources for electric vehicles and large-scale energy storage. However, the direct uses of flammable organic liquid electrolyte with commercial separator induce serious safety problems including the risk of fire and explosion. Herein, we report the development of poly(vinylidene difluoride-co-hexafluoropropylene) polymer membranes with multi-sized honeycomb-like porous architectures. The as-prepared polymer electrolyte membranes contain porosity as high as 78%, which leads to the high electrolyte uptake of 86.2 wt%. The PVDF-HFP gel polymer electrolyte membranes exhibited a high ionic conductivity of 1.03 mS cm−1 at room temperature, which is much higher than that of commercial polymer membranes. Moreover, the as-obtained gel polymer membranes are also thermally stable up to 350°C and non-combustible in fire (fire-proof). When applied in lithium ion batteries with LiFePO4 as cathode materials, the gel polymer electrolyte demonstrated excellent electrochemical performances. This investigation indicates that PVDF-HFP gel polymer membranes could be potentially applicable for high power lithium ion batteries with the features of high safety, low cost and good performance. PMID:25168687

Studies on the effect of dispersoid(ZrO2) in PVdF-co-HFP based gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Sivakumar, M.; Subadevi, R.; Muthupradeepa, R.

2013-06-01

Gel polymer electrolytes containing poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) / Lithium bis(trifluoromethane sulfon)imide (LiTFSI) / mixture of ethylene carbonate and propylene carbonate (EC+PC) with different concendration of ZrO2 has been prepared using the solution casting technique. The conductivity of the prepared electrolyte sample has been determined by AC impedance technique in the range 303-353K. The temperature dependent ionic conductivity plot seems to obey VTF relation. The maximum ionic conductivity value of 4.46 × 10-3S/cm has been obtained for PVdF-co-HFP(32%) - LiTFSI(8%) - EC+PC (60%) + ZrO2(6wt%) based polymer electrolyte. The surface morphology of the prepared electrolyte sample has been studied using SEM.

A Polymer Electrolyte for Dye-Sensitized Solar Cells Based on a Poly(Polyvinylidenefluoride-Co-Hexafluoropropylene)/Hydroxypropyl Methyl Cellulose Blend

NASA Astrophysics Data System (ADS)

Won, Lee Ji; Kim, Jae Hong; Thogiti, Suresh

2018-05-01

A novel polymer blend electrolyte for dye-sensitized solar cells (DSSCs) was synthesized by quasi-solidifying a liquid-based electrolyte containing an iodide/triiodide redox couple and supporting salts with a mixture of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and indigenous hydroxypropyl methyl cellulose (HPMC). A high ionic conductivity of 8.8 × 10-4 S cm-1 was achieved after introducing 5 wt% of HPMC with respect to the weight of PVDH-HFP. DSSCs were fabricated using gel polymer blend electrolytes, and the J-V characteristics of the fabricated devices were analyzed. Under optimal conditions, the photovoltaic conversion efficiency of cells with the novel HPMC-blended gel electrolyte (5.34%) was significantly greater than that of cells without HPMC (3.97%).

Two Players Make a Formidable Combination: In Situ Generated Poly(acrylic anhydride-2-methyl-acrylic acid-2-oxirane-ethyl ester-methyl methacrylate) Cross-Linking Gel Polymer Electrolyte toward 5 V High-Voltage Batteries.

PubMed

Ma, Yue; Ma, Jun; Chai, Jingchao; Liu, Zhihong; Ding, Guoliang; Xu, Gaojie; Liu, Haisheng; Chen, Bingbing; Zhou, Xinhong; Cui, Guanglei; Chen, Liquan

2017-11-29

Electrochemical performance of high-voltage lithium batteries with high energy density is limited because of the electrolyte instability and the electrode/electrolyte interfacial reactivity. Hence, a cross-linking polymer network of poly(acrylic anhydride-2-methyl-acrylic acid-2-oxirane-ethyl ester-methyl methacrylate) (PAMM)-based electrolyte was introduced via in situ polymerization inspired by "shuangjian hebi", which is a statement in a traditional Chinese Kungfu story similar to the synergetic effect of 1 + 1 > 2. A poly(acrylic anhydride) and poly(methyl methacrylate)-based system is very promising as electrolyte materials for lithium-ion batteries, in which the anhydride and acrylate groups can provide high voltage resistance and fast ionic conductivity, respectively. As a result, the cross-linking PAMM-based electrolyte possesses a significant comprehensive enhancement, including electrochemical stability window exceeding 5 V vs Li + /Li, an ionic conductivity of 6.79 × 10 -4 S cm -1 at room temperature, high mechanical strength (27.5 MPa), good flame resistance, and excellent interface compatibility with Li metal. It is also demonstrated that this gel polymer electrolyte suppresses the negative effect resulting from dissolution of Mn 2+ ions at 25 and 55 °C. Thus, the LiNi 0.5 Mn 1.5 O 4 /Li and LiNi 0.5 Mn 1.5 O 4 /Li 4 Ti 5 O 12 cells using the optimized in situ polymerized cross-linking PAMM-based gel polymer electrolyte deliver stable charging/discharging profiles and excellent rate performance at room temperature and even at 55 °C. These findings suggest that the cross-linking PAMM is an intriguing candidate for 5 V class high-voltage gel polymer electrolyte toward high-energy lithium-on batteries.

A Gel-Polymer Sn-C/LiMn0.5Fe0.5PO4 Battery Using a Fluorine-Free Salt.

PubMed

Di Lecce, Daniele; Fasciani, Chiara; Scrosati, Bruno; Hassoun, Jusef

2015-09-30

Safety and environmental issues, because of the contemporary use of common liquid electrolytes, fluorinated salts, and LiCoO2-based cathodes in commercial Li-ion batteries, might be efficiently mitigated by employing alternative gel-polymer battery configurations and new electrode materials. Herein we study a lithium-ion polymer cell formed by combining a LiMn0.5Fe0.5PO4 olivine cathode, prepared by simple solvothermal pathway, a nanostructured Sn-C anode, and a LiBOB-containing PVdF-based gel electrolyte. The polymer electrolyte, here analyzed in terms of electrochemical stability by impedance spectroscopy (EIS) and voltammetry, reveals full compatibility for cell application. The LiBOB electrolyte salt and the electrochemically delithiaded Mn0.5Fe0.5PO4 have a higher thermal stability compared to conventional LiPF6 and Li0.5CoO2, as confirmed by thermogravimetric analysis (TGA) and by galvanostatic cycling at high temperature. LiMn0.5Fe0.5PO4 and Sn-C, showing in lithium half-cell a capacity of about 120 and 350 mAh g(-1), respectively, within the gelled electrolyte configuration are combined in a full Li-ion polymer battery delivering a stable capacity of about 110 mAh g(-1), with working voltage ranging from 2.8 to 3.6 V.

Anisotropically Swelling Gels Attained through Axis-Dependent Crosslinking of MOF Crystals.

PubMed

Ishiwata, Takumi; Kokado, Kenta; Sada, Kazuki

2017-03-01

Anisotropically deforming objects have attracted considerable interest for use in molecular machines and artificial muscles. Herein, we focus on a new approach based on the crystal crosslinking of organic ligands in a pillared-layer metal-organic framework (PLMOF). The approach involves the transformation from crosslinked PLMOF to polymer gels through hydrolysis of the coordination bonds between the organic ligands and metal ions, giving a network polymer that exhibits anisotropic swelling. The anisotropic monomer arrangement in the PLMOF underwent axis-dependent crosslinking to yield anisotropically swelling gels. Therefore, the crystal crosslinking of MOFs should be a useful method for creating actuators with designable deformation properties. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimizing Ionic Electrolytes for Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Fan, Xiaojuan; Hall, Sarah

2009-03-01

Dye-sensitized solar cells DSSCs provide next generation, low cost, and easy fabrication photovoltaic devices based on organic sensitizing molecules, polymer gel electrolyte, and metal oxide semiconductors. One of the key components is the solvent-free ionic liquid electrolyte that has low volatility and high stability. We report a rapid and low cost method to fabricate ionic polymer electrolyte used in DSSCs. Poly(ethylene oxide) (PEO) is blended with imidazolinium salt without any chemical solvent to form a gel electrolyte. Uniform and crack-free porous TiO2 thin films are sensitized by porphrine dye covered by the synthesized gel electrolyte. The fabricated DSSCs are more stable and potentially increase the photo-electricity conversion efficiency.

Preliminary investigation of PAGAT polymer gel radionuclide dosimetry of Tc-99m

NASA Astrophysics Data System (ADS)

Braun, Kelly; Bailey, Dale; Hill, Brendan; Baldock, Clive

2009-05-01

PAGAT polymer gel was investigated as a suitable dosimeter materials for measuring absorbed dose from the unsealed source radionuclide Tc-99m. Differing amounts of Tc-99m over the range of 25-5000 MBq were introduced into a normoxic polymer gel mixture (PAGAT) in sealed nitrogen-filled P6 glass vials. After irradiation the gels were evaluated using MRI more than 48 hours after preparation to allow for radioactive decay. The dose delivered to the vial was also calculated empirically. R2 versus total activity curves were obtained over a number of experiments and these were used to evaluate the relationship between the amount of gel polymerization and the dose deposited by the radionuclide. A linear response up to 1000 MBq (corresponding to 20Gy) was displayed and was still behaving monotonically at 5000 MBq. Polymer gels offer the potential to measure radiation dose three-dimensionally using MRI.

Modeling the controllable pH-responsive swelling and pore size of networked alginate based biomaterials.

PubMed

Chan, Ariel W; Neufeld, Ronald J

2009-10-01

Semisynthetic network alginate polymer (SNAP), synthesized by acetalization of linear alginate with di-aldehyde, is a pH-responsive tetrafunctionally linked 3D gel network, and has potential application in oral delivery of protein therapeutics and active biologicals, and as tissue bioscaffold for regenerative medicine. A constitutive polyelectrolyte gel model based on non-Gaussian polymer elasticity, Flory-Huggins liquid lattice theory, and non-ideal Donnan membrane equilibria was derived, to describe SNAP gel swelling in dilute and ionic solutions containing uni-univalent, uni-bivalent, bi-univalent or bi-bi-valent electrolyte solutions. Flory-Huggins interaction parameters as a function of ionic strength and characteristic ratio of alginates of various molecular weights were determined experimentally to numerically predict SNAP hydrogel swelling. SNAP hydrogel swells pronouncedly to 1000 times in dilute solution, compared to its compact polymer volume, while behaving as a neutral polymer with limited swelling in high ionic strength or low pH solutions. The derived model accurately describes the pH-responsive swelling of SNAP hydrogel in acid and alkaline solutions of wide range of ionic strength. The pore sizes of the synthesized SNAP hydrogels of various crosslink densities were estimated from the derived model to be in the range of 30-450 nm which were comparable to that measured by thermoporometry, and diffusion of bovine serum albumin. The derived equilibrium swelling model can characterize hydrogel structure such as molecular weight between crosslinks and crosslinking density, or can be used as predictive model for swelling, pore size and mechanical properties if gel structural information is known, and can potentially be applied to other point-link network polyelectrolytes such as hyaluronic acid gel.

Large strain deformation behavior of polymeric gels in shear- and cavitation rheology

NASA Astrophysics Data System (ADS)

Hashemnejad, Seyed Meysam; Kundu, Santanu

Polymeric gels are used in many applications including in biomedical and in food industries. Investigation of mechanical responses of swollen polymer gels and linking that to the polymer chain dynamics are of significant interest. Here, large strain deformation behavior of two different gel systems and with different network architecture will be presented. We consider biologically relevant polysaccharide hydrogels, formed through ionic and covalent crosslinking, and physically associating triblock copolymer gels in a midblock selective solvent. Gels with similar low-strain shear modulus display distinctly different non-linear rheological behavior in large strain shear deformation. Both these gels display strain-stiffening behavior in shear-deformation prior to macroscopic fracture of the network, however, only the alginate gels display negative normal stress. The cavitation rheology data show that the critical pressure for cavitation is higher for alginate gels than that observed for triblock gels. These distinctly different large-strain deformation behavior has been related to the gel network structure, as alginate chains are much stiffer than the triblock polymer chains.

Acylhydrazone bond dynamic covalent polymer gel monolithic column online coupling to high-performance liquid chromatography for analysis of sulfonamides and fluorescent whitening agents in food.

PubMed

Zhang, Chengjiang; Luo, Xialin; Wei, Tianfu; Hu, Yufei; Li, Gongke; Zhang, Zhuomin

2017-10-13

A new dynamic covalent polymer (DCP) gel was well designed and constructed based on imine chemistry. Polycondensation of 4,4'-biphenyldicarboxaldehyde and 1,3,5-benzenetricarbohydrazide via Schiff-base reaction resulted in an acylhydrazone bond gel (AB-gel) DCP. AB-gel DCP had three-dimensional network of interconnected nanoparticles with hierarchically porous structure. AB-gel DCP was successfully fabricated as a monolithic column by an in-situ chemical bonding method for online enrichment and separation purpose with excellent permeability. AB-gel DCP based monolithic column showed remarkable adsorption affinity towards target analytes including sulfonamides (SAs) and fluorescent whitening agents (FWAs) due to its strong π-π affinity, hydrophobic effect and hydrogen bonding interaction. Then, AB-gel DCP based monolithic column was applied for online separation and analysis of trace SAs and FWAs in food samples coupled with high-performance liquid chromatography (HPLC). Sulfathiazole (ST) and sulfadimidine (SM2) in one positive weever sample were actually found and determined with concentrations of 273.8 and 286.3μg/kg, respectively. 2,5-Bis(5-tert-butyl-2-benzoxazolyl) thiophene (FWA184) was actually quantified in one tea infusion sample with the concentration of 268.5ng/L. The spiked experiments suggested the good recoveries in range of 74.5-110% for SAs in weever and shrimp samples with relative standard deviations (RSDs) less than 9.7% and in range of 74.0-113% for FWAs in milk and tea infusion samples with RSDs less than 9.0%. AB-gel DCP monolithic column was proved to be a promising sample preparation medium for online separation and analysis of trace analytes in food samples with complex matrices. Copyright © 2017 Elsevier B.V. All rights reserved.

Self-assembling semiconducting polymers--rods and gels from electronic materials.

PubMed

Clark, Andrew P-Z; Shi, Chenjun; Ng, Benny C; Wilking, James N; Ayzner, Alexander L; Stieg, Adam Z; Schwartz, Benjamin J; Mason, Thomas G; Rubin, Yves; Tolbert, Sarah H

2013-02-26

In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.

Electrochemical characteristics of Li/LiMn 2O 4 cells using gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Kim, Dong-Won; Ko, Jang-Myoun; Chun, Jong-Han

Gel polymer electrolytes composed of acrylonitrile-methylmethacrylate (AM) copolymer and 1 M LiClO 4-ethylene carbonate (EC)/propylene carbonate (PC) are prepared. The ionic conductivity reaches 1.9×10 -3 S cm -1 in a gel polymer electrolyte with 20 wt.% of AM copolymer and 80 wt.% of LiClO 4-EC/PC at room temperature. These systems showed no solvent exudation from the matrix polymer due to enhanced compatibility between AM copolymer and organic liquid electrolyte. A Li/gel polymer electrolyte/LiMn 2O 4 cell has a reversible capacity of 132 mAh g -1 in the voltage range of 3.0-4.3 V at the C/5 rate and shows good cycling performance with a coulombic efficiency >99%.

Lamellar Biogels: Fluid-Membrane-Based Hydrogels Containing Polymer Lipids

NASA Astrophysics Data System (ADS)

Warriner, Heidi E.; Idziak, Stefan H. J.; Slack, Nelle L.; Davidson, Patrick; Safinya, Cyrus R.

1996-02-01

A class of lamellar biological hydrogels comprised of fluid membranes of lipids and surfactants with small amounts of low molecular weight poly(ethylene glycol)-derived polymer lipids (PEG-lipids) were studied by x-ray diffraction, polarized light microscopy, and rheometry. In contrast to isotropic hydrogels of polymer networks, these membrane-based birefringent liquid crystalline biogels, labeled Lα,g, form the gel phase when water is added to the liquid-like lamellar L_α phase, which reenters a liquid-like mixed phase upon further dilution. Furthermore, gels with larger water content require less PEG-lipid to remain stable. Although concentrated (~50 weight percent) mixtures of free PEG (molecular weight, 5000) and water do not gel, gelation does occur in mixtures containing as little as 0.5 weight percent PEG-lipid. A defining signature of the Lα,g regime as it sets in from the fluid lamellar L_α phase is the proliferation of layer-dislocation-type defects, which are stabilized by the segregation of PEG-lipids to the defect regions of high membrane curvature that connect the membranes.

Cross-linked Composite Gel Polymer Electrolyte using Mesoporous Methacrylate-Functionalized SiO2 Nanoparticles for Lithium-Ion Polymer Batteries

PubMed Central

Shin, Won-Kyung; Cho, Jinhyun; Kannan, Aravindaraj G.; Lee, Yoon-Sung; Kim, Dong-Won

2016-01-01

Liquid electrolytes composed of lithium salt in a mixture of organic solvents have been widely used for lithium-ion batteries. However, the high flammability of the organic solvents can lead to thermal runaway and explosions if the system is accidentally subjected to a short circuit or experiences local overheating. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures. PMID:27189842

Dual release and molecular mechanism of bilayered aceclofenac tablet using polymer mixture.

PubMed

Van Nguyen, Hien; Nguyen, Van Hong; Lee, Beom-Jin

2016-12-30

The objectives of the present study were to develop a controlled-release bilayered tablet of aceclofenac (AFN) 200mg with dual release and to gain a mechanistic understanding of the enhanced sustained release capability achieved by utilizing a binary mixture of the sustained release materials. Different formulations of the sustained-release layer were formulated by employing hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) as the major retarding polymers. The in vitro dissolution studies of AFN bilayered tablets were carried out in intestinal fluid (pH 6.8 buffer). The mechanism of the synergistic rate-retarding effect of the polymer mixture containing HPC and carbomer was elucidated by the rate of swelling and erosion in intestinal fluid and the molecular interactions in the polymer network. The optimized bilayered tablets had similar in vitro dissolution profiles to the marketed tablet Clanza ® CR based on the similarity factor (f2) in combination with their satisfactory micromeritic, physicochemical properties, and stability profiles. Drug release from HPMC-based matrix was controlled by non-Fickian transport, while drug release from HPC-based matrix was solely governed by drug diffusion. The swelling and erosion data exhibited a dramatic increase of water uptake and a reduction of weight loss in the polymer mixture-loaded tablet. Fourier transform infrared (FTIR) spectra revealed strong hydrogen bonding between HPC and carbomer in the polymer mixture. Regarding spatial distribution of polymers in the polymer mixture-loaded tablet, carbomer was found to be the main component of the gel layer during the first 2h of the hydration process, which was responsible for retarding drug release at initial stage. This process was then followed by a gradual transition of HPC from the glassy core to the gel layer for further increasing gel strength. Copyright © 2016 Elsevier B.V. All rights reserved.

Facile and Reliable in Situ Polymerization of Poly(Ethyl Cyanoacrylate)-Based Polymer Electrolytes toward Flexible Lithium Batteries.

PubMed

Cui, Yanyan; Chai, Jingchao; Du, Huiping; Duan, Yulong; Xie, Guangwen; Liu, Zhihong; Cui, Guanglei

2017-03-15

Polycyanoacrylate is a very promising matrix for polymer electrolyte, which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups. Herein, a facile and reliable in situ polymerization strategy of poly(ethyl cyanoacrylate) (PECA) based gel polymer electrolytes (GPE) via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO 4 in carbonate solvents. The in situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity (2.7 × 10 -3 S cm -1 ) at room temperature, and exhibited a considerable electrochemical stability window up to 4.8 V vs Li/Li + . The LiFePO 4 /PECA-GPE/Li and LiNi 1.5 Mn 0.5 O 4 /PECA-GPE/Li batteries using this in-situ-polymerized GPE delivered stable charge/discharge profiles, considerable rate capability, and excellent cycling performance. These results demonstrated this reliable in situ polymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries, micropower lithium batteries, and deformable lithium batteries for special purpose.

Development of dye-sensitized solar cells composed of liquid crystal embedded, electrospun poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers as polymer gel electrolytes.

PubMed

Ahn, Sung Kwang; Ban, Taewon; Sakthivel, P; Lee, Jae Wook; Gal, Yeong-Soon; Lee, Jin-Kook; Kim, Mi-Ra; Jin, Sung-Ho

2012-04-01

In order to overcome the problems associated with the use of liquid electrolytes in dye-sensitized solar cells (DSSCs), a new system composed of liquid crystal embedded, polymer electrolytes has been developed. For this purpose, three types of DSSCs have been fabricated. The cells contain electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (e-PVdF-co-HFP) polymer gel electrolyte, with and without doping with the liquid crystal E7 and with a liquid electrolyte. The morphologies of the newly prepared DSSCs were explored using field emission scanning electron microscopy (FE-SEM). Analysis of the FE-SEM images indicate that the DSSC composed of E7 embedded on e-PVdF-co-HFP polymer gel electrolyte has a greatly regular morphology with an average diameter. The ionic conductivity of E7 embedded on e-PVdF-co-HFP polymer gel electrolyte was found to be 2.9 × 10(-3) S/cm at room temperature, a value that is 37% higher than that of e-PVdF-co-HFP polymer gel electrolyte. The DCCS containing the E7 embedded, e-PVdF-co-HFP polymer gel electrolyte was observed to possess a much higher power conversion efficiency (PCE = 6.82%) than that of an e-PVdF-co-HFP nanofiber (6.35%). In addition, DSSCs parameters of the E7 embedded, e-PVdF-co-HFP polymer gel electrolyte (V(oc) = 0.72 V, J(sc) = 14.62 mA/cm(2), FF = 64.8%, and PCE = 6.82% at 1 sun intensity) are comparable to those of a liquid electrolyte (V(oc) = 0.75 V, J(sc) = 14.71 mA/cm(2), FF = 64.9%, and PCE = 7.17%, both at a 1 sun intensity).

3D polymer gel dosimetry using a 3D (DESS) and a 2D MultiEcho SE (MESE) sequence

NASA Astrophysics Data System (ADS)

Maris, Thomas G.; Pappas, Evangelos; Karolemeas, Kostantinos; Papadakis, Antonios E.; Zacharopoulou, Fotini; Papanikolaou, Nickolas; Gourtsoyiannis, Nicholas

2006-12-01

The utilization of 3D techniques in Magnetic Resonance Imaging data aquisition and post-processing analysis is a prerequisite especially when modern radiotherapy techniques (conformal RT, IMRT, Stereotactic RT) are to be used. The aim of this work is to compare a 3D Double Echo Steady State (DESS) and a 2D Multiple Echo Spin Echo (MESE) sequence in 3D MRI radiation dosimetry using two different MRI scanners and utilising N-VInylPyrrolidone (VIPAR) based polymer gels.

A theory for fracture of polymeric gels

NASA Astrophysics Data System (ADS)

Mao, Yunwei; Anand, Lallit

2018-06-01

A polymeric gel is a cross-linked polymer network swollen with a solvent. If the concentration of the solvent or the deformation is increased to substantial levels, especially in the presence of flaws, then the gel may rupture. Although various theoretical aspects of coupling of fluid permeation with large deformation of polymeric gels are reasonably well-understood and modeled in the literature, the understanding and modeling of the effects of fluid diffusion on the damage and fracture of polymeric gels is still in its infancy. In this paper we formulate a thermodynamically-consistent theory for fracture of polymeric gels - a theory which accounts for the coupled effects of fluid diffusion, large deformations, damage, and also the gradient effects of damage. The particular constitutive equations for fracture of a gel proposed in our paper, contain two essential new ingredients: (i) Our constitutive equation for the change in free energy of a polymer network accounts for not only changes in the entropy, but also changes in the internal energy due the stretching of the Kuhn segments of the polymer chains in the network. (ii) The damage and failure of the polymer network is taken to occur by chain-scission, a process which is driven by the changes in the internal energy of the stretched polymer chains in the network, and not directly by changes in the configurational entropy of the polymer chains. The theory developed in this paper is numerically implemented in an open-source finite element code MOOSE, by writing our own application. Using this simulation capability we report on our study of the fracture of a polymeric gel, and some interesting phenomena which show the importance of the diffusion of the fluid on fracture response of the gel are highlighted.

Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries.

PubMed

Pandey, Gaind P; Klankowski, Steven A; Li, Yonghui; Sun, Xiuzhi Susan; Wu, Judy; Rojeski, Ronald A; Li, Jun

2015-09-23

This study demonstrates the full infiltration of gel polymer electrolyte into silicon-coated vertically aligned carbon nanofibers (Si-VACNFs), a high-capacity 3D nanostructured anode, and the electrochemical characterization of its properties as an effective electrolyte/separator for future all-solid-state lithium-ion batteries. Two fabrication methods have been employed to form a stable interface between the gel polymer electrolyte and the Si-VACNF anode. In the first method, the drop-casted gel polymer electrolyte is able to fully infiltrate into the open space between the vertically aligned core-shell nanofibers and encapsulate/stabilize each individual nanofiber in the polymer matrix. The 3D nanostructured Si-VACNF anode shows a very high capacity of 3450 mAh g(-1) at C/10.5 (or 0.36 A g(-1)) rate and 1732 mAh g(-1) at 1C (or 3.8 A g(-1)) rate. In the second method, a preformed gel electrolyte film is sandwiched between an Si-VACNF electrode and a Li foil to form a half-cell. Most of the vertical core-shell nanofibers of the Si-VACNF anode are able to penetrate into the gel polymer film while retaining their structural integrity. The slightly lower capacity of 2800 mAh g(-1) at C/11 rate and ∼1070 mAh g(-1) at C/1.5 (or 2.6 A g(-1)) rate have been obtained, with almost no capacity fade for up to 100 cycles. Electrochemical impedance spectroscopy does not show noticeable changes after 110 cycles, further revealing the stable interface between the gel polymer electrolyte and the Si-VACNFs anode. These results show that the infiltrated flexible gel polymer electrolyte can effectively accommodate the stress/strain of the Si shell due to the large volume expansion/contraction during the charge-discharge processes, which is particularly useful for developing future flexible solid-state lithium-ion batteries incorporating Si-anodes.

Polymer gel water equivalence and relative energy response with emphasis on low photon energy dosimetry in brachytherapy

NASA Astrophysics Data System (ADS)

Pantelis, E.; Karlis, A. K.; Kozicki, M.; Papagiannis, P.; Sakelliou, L.; Rosiak, J. M.

2004-08-01

The water equivalence and stable relative energy response of polymer gel dosimeters are usually taken for granted in the relatively high x-ray energy range of external beam radiotherapy based on qualitative indices such as mass and electron density and effective atomic number. However, these favourable dosimetric characteristics are questionable in the energy range of interest to brachytherapy especially in the case of lower energy photon sources such as 103Pd and 125I that are currently utilized. In this work, six representative polymer gel formulations as well as the most commonly used experimental set-up of a LiF TLD detector-solid water phantom are discussed on the basis of mass attenuation and energy absorption coefficients calculated in the energy range of 10 keV-10 MeV with regard to their water equivalence as a phantom and detector material. The discussion is also supported by Monte Carlo simulation results. It is found that water equivalence of polymer gel dosimeters is sustained for photon energies down to about 60 keV and no corrections are needed for polymer gel dosimetry of 169Yb or 192Ir sources. For 125I and 103Pd sources, however, a correction that is source-distance dependent is required. Appropriate Monte Carlo results show that at the dosimetric reference distance of 1 cm from a source, these corrections are of the order of 3% for 125I and 2% for 103Pd. These have to be compared with corresponding corrections of up to 35% for 125I and 103Pd and up to 15% even for the 169Yb energies for the experimental set-up of the LiF TLD detector-solid water phantom.

Polymer gel water equivalence and relative energy response with emphasis on low photon energy dosimetry in brachytherapy.

PubMed

Pantelis, E; Karlis, A K; Kozicki, M; Papagiannis, P; Sakelliou, L; Rosiak, J M

2004-08-07

The water equivalence and stable relative energy response of polymer gel dosimeters are usually taken for granted in the relatively high x-ray energy range of external beam radiotherapy based on qualitative indices such as mass and electron density and effective atomic number. However, these favourable dosimetric characteristics are questionable in the energy range of interest to brachytherapy especially in the case of lower energy photon sources such as 103Pd and 125I that are currently utilized. In this work, six representative polymer gel formulations as well as the most commonly used experimental set-up of a LiF TLD detector-solid water phantom are discussed on the basis of mass attenuation and energy absorption coefficients calculated in the energy range of 10 keV-10 MeV with regard to their water equivalence as a phantom and detector material. The discussion is also supported by Monte Carlo simulation results. It is found that water equivalence of polymer gel dosimeters is sustained for photon energies down to about 60 keV and no corrections are needed for polymer gel dosimetry of 169Yb or 192Ir sources. For 125I and 103Pd sources, however, a correction that is source-distance dependent is required. Appropriate Monte Carlo results show that at the dosimetric reference distance of 1 cm from a source, these corrections are of the order of 3% for 125I and 2% for 103Pd. These have to be compared with corresponding corrections of up to 35% for 125I and 103Pd and up to 15% even for the 169Yb energies for the experimental set-up of the LiF TLD detector-solid water phantom.

Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-05-01

Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid organic-inorganic materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared by an organic base or Bronsted acid (formic or triflic acid), without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

Photo-induced locomotion of chemo-responsive polymer gels

NASA Astrophysics Data System (ADS)

Dayal, Pratyush; Kuksenok, Olga; Balazs, Anna C.

2009-03-01

The need to translate chemical energy into a mechanical response, a characteristic of many biological processes, has motivated the study of stimuli-responsive polymer gels. Recently, it has been shown experimentally that by coupling the mechanical properties of the gel with the Belousov-Zhabotinsky (BZ) reaction it is possible to induce self-sustained oscillations in the gel. One of the means for controlling these chemical oscillations is using light as an external stimulus. To study the effect of light on the mechanical behavior of the gel, we use our recently developed a 3D gel lattice spring model (gLSM) which couples the BZ reaction kinetics to the gel dynamics. In this model, the polymer-solvent interactions were taken into account by adding a coupling term to the Flory-Huggins free energy. By virtue of this coupling term, the swelling---de-swelling behavior of the gel was captured in 3D. In order to include the effect of the polymer on the reaction kinetics, the Oregonator model for the photo-sensitive BZ reaction was also modified. Using gLSM model, we probed the effect of non-uniform light irradiation on the gel dynamics. We were able to manipulate the direction and velocity of locomotion of the gel using light as a control parameter. This ability to control the movement of the gel can be utilized in a variety of applications, ranging from bio-actuators to controlled drug release systems.

pH and temperature dual-sensitive liposome gel based on novel cleavable mPEG-Hz-CHEMS polymeric vaginal delivery system

PubMed Central

Chen, Daquan; Sun, Kaoxiang; Mu, Hongjie; Tang, Mingtan; Liang, Rongcai; Wang, Aiping; Zhou, Shasha; Sun, Haijun; Zhao, Feng; Yao, Jianwen; Liu, Wanhui

2012-01-01

Background In this study, a pH and temperature dual-sensitive liposome gel based on a novel cleavable hydrazone-based pH-sensitive methoxy polyethylene glycol 2000-hydrazone-cholesteryl hemisuccinate (mPEG-Hz-CHEMS) polymer was used for vaginal administration. Methods The pH-sensitive, cleavable mPEG-Hz-CHEMS was designed as a modified pH-sensitive liposome that would selectively degrade under locally acidic vaginal conditions. The novel pH-sensitive liposome was engineered to form a thermogel at body temperature and to degrade in an acidic environment. Results A dual-sensitive liposome gel with a high encapsulation efficiency of arctigenin was formed and improved the solubility of arctigenin characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. The dual-sensitive liposome gel with a sol-gel transition at body temperature was degraded in a pH-dependent manner, and was stable for a long period of time at neutral and basic pH, but cleavable under acidic conditions (pH 5.0). Arctigenin encapsulated in a dual-sensitive liposome gel was more stable and less toxic than arctigenin loaded into pH-sensitive liposomes. In vitro drug release results indicated that dual-sensitive liposome gels showed constant release of arctigenin over 3 days, but showed sustained release of arctigenin in buffers at pH 7.4 and pH 9.0. Conclusion This research has shed some light on a pH and temperature dual-sensitive liposome gel using a cleavable mPEG-Hz-CHEMS polymer for vaginal delivery. PMID:22679372

Viscoplastic fracture transition of a biopolymer gel.

PubMed

Frieberg, Bradley R; Garatsa, Ray-Shimry; Jones, Ronald L; Bachert, John O; Crawshaw, Benjamin; Liu, X Michael; Chan, Edwin P

2018-06-13

Physical gels are swollen polymer networks consisting of transient crosslink junctions associated with hydrogen or ionic bonds. Unlike covalently crosslinked gels, these physical crosslinks are reversible thus enabling these materials to display highly tunable and dynamic mechanical properties. In this work, we study the polymer composition effects on the fracture behavior of a gelatin gel, which is a thermoreversible biopolymer gel consisting of denatured collagen chains bridging physical network junctions formed from triple helices. Below the critical volume fraction for chain entanglement, which we confirm via neutron scattering measurements, we find that the fracture behavior is consistent with a viscoplastic type process characterized by hydrodynamic friction of individual polymer chains through the polymer mesh to show that the enhancement in fracture scales inversely with the squared of the mesh size of the gelatin gel network. Above this critical volume fraction, the fracture process can be described by the Lake-Thomas theory that considers fracture as a chain scission process due to chain entanglements.

Soft matter: rubber and networks

NASA Astrophysics Data System (ADS)

McKenna, Gregory B.

2018-06-01

Rubber networks are important and form the basis for materials with properties ranging from rubber tires to super absorbents and contact lenses. The development of the entropy ideas of rubber deformation thermodynamics provides a powerful framework from which to understand and to use these materials. In addition, swelling of the rubber in the presence of small molecule liquids or solvents leads to materials that are very soft and ‘gel’ like in nature. The review covers the thermodynamics of polymer networks and gels from the perspective of the thermodynamics and mechanics of the strain energy density function. Important relationships are presented and experimental results show that the continuum ideas contained in the phenomenological thermodynamics are valid, but that the molecular bases for some of them remain to be fully elucidated. This is particularly so in the case of the entropic gels or swollen networks. The review is concluded with some perspectives on other networks, ranging from entropic polymer networks such as thermoplastic elastomers to physical gels in which cross-link points are formed by glassy or crystalline domains. A discussion is provided for other physical gels in which the network forms a spinodal-like decomposition, both in thermoplastic polymers that form a glassy network upon phase separation and for colloidal gels that seem to have a similar behavior.

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

NASA Astrophysics Data System (ADS)

Savina, Irina N.; Ingavle, Ganesh C.; Cundy, Andrew B.; Mikhalovsky, Sergey V.

2016-02-01

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200 μm in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400 ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeshita, Kenji

A mathematical model to predict the extraction behavior of metal ion between a polymer gel and an aqueous solution was proposed. It consists of the Flory-Huggins formula for evaluating thermodynamically the physico-chemical properties of polymer gel, the modified Stokes-Einstein equation to evaluate the mass transfer rate of metal ion into polymer gel and the equation to evaluate the extraction equilibrium. The extraction of lanthanide elements, Nd(III), Sm(III) and Gd(III), from an aqueous solution containing nitrate ion was carried out by the use of SDB (styrene-divinylbenzene copolymer) gel swollen with a bidentate organophosphorus compound, CMP (dihexyl-N,N-diethylcarbamoylmethylpohosphonate). The binary extraction and themore » effect of the crosslinking degree of SDB gel on the extraction rate were examined. These experimental results were in agreement with the predictions calculated by the proposed model. It was confirmed that the extraction behavior of lanthanide ions into the SDB gel was predicted accurately, when the physico-chemical properties of SDB gel, such as the affinity between SDB and CMP ({chi}) and the crosslinking degree ({nu}{sub e}), and a coefficient defined in the modified Stokes-Einstein equation (K{sub 0}) were known. This model is available as a tool to design an extraction chromatographic process using polymer gel.« less

Coordination polymer gels with important environmental and biological applications.

PubMed

Jung, Jong Hwa; Lee, Ji Ha; Silverman, Julian R; John, George

2013-02-07

Coordination Polymer Gels (CPGs) constitute a subset of solid-like metal ion and bridging organic ligand structures (similar to metal-organic frameworks) that form multi-dimensional networks through a trapped solvent as a result of non-covalent interactions. While physical properties of these gels are similar to conventional high molecular weight organic polymer gels, coordination polymer gel systems are often fully reversible and can be assembled and disassembled in the presence of additional energy (heat, sonication, shaking) to give a solution of solvated gelators. Compared to gels resulting from purely organic self-assembled low molecular weight gelators, metal ions incorporated into the fibrilar networks spanning the bulk solvent can impart CPGs with added functionalities. The solid/liquid nature of the gels allows for species to migrate through the gel system and interact with metals, ligands, and the solvent. Chemosensing, catalysis, fluorescence, and drug-delivery applications are some of the many potential uses for these dynamic systems, taking advantage of the metal ion's coordination, the organic polydentate ligand's orientation and functionality, or a combination of these properties. By fine tuning these systems through metal ion and ligand selection and by directing self-assembly with external stimuli the rational synthesis of practical systems can be envisaged.

Ophthalmic gels: Past, present and future.

PubMed

Al-Kinani, Ali A; Zidan, Ghada; Elsaid, Naba; Seyfoddin, Ali; Alani, Adam W G; Alany, Raid G

2018-02-15

Aqueous gels formulated using hydrophilic polymers (hydrogels) along with those based on stimuli responsive polymers (in situ gelling or gel forming systems) continue to attract increasing interest for various eye health-related applications. They allow the incorporation of a variety of ophthalmic pharmaceuticals to achieve therapeutic levels of drugs and bioactives at target ocular sites. The integration of sophisticated drug delivery technologies such as nanotechnology-based ones with intelligent and environment responsive systems can extend current treatment duration to provide more clinically relevant time courses (weeks and months instead of hours and days) which will inevitably reduce dose frequency, increase patient compliance and improve clinical outcomes. Novel applications and design of contact lenses and intracanalicular delivery devices along with the move towards integrating gels into various drug delivery devices like intraocular pumps, injections and implants has the potential to reduce comorbidities caused by glaucoma, corneal keratopathy, cataract, diabetic retinopathies and age-related macular degeneration. This review describes ophthalmic gelling systems with emphasis on mechanism of gel formation and application in ophthalmology. It provides a critical appraisal of the techniques and methods used in the characterization of ophthalmic preformed gels and in situ gelling systems along with a thorough insight into the safety and biocompatibility of these systems. Newly developed ophthalmic gels, hydrogels, preformed gels and in situ gelling systems including the latest in the area of stimuli responsive gels, molecularly imprinted gels, nanogels, 3D printed hydrogels; 3D printed devices comprising ophthalmic gels are covered. Finally, new applications of gels in the production of artificial corneas, corneal wound healing and hydrogel contact lenses are described. Copyright © 2017 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balhoff, Matthew; Tavassoli, Shayan; Fei Ho, Jostine

The potential leakage of hydrocarbon fluids or CO 2 out of subsurface formations through wells with fractured cement or debonded microannuli is a primary concern in oil and gas production and CO 2 storage. The presence of fractures in a cement annulus with apertures on the order of 10–300 microns can pose a significant leakage danger with effective permeability in the range of 0.1–1 mD (millidarcy). Leakage pathways with small apertures are often difficult to repair using conventional oilfield cement, thus a low-viscosity sealant that can be easily placed into these fractures while providing an effective seal is desired. Themore » development of a novel application using pH-triggered polymeric sealants could potentially be the solution to plugging these fractures and that was the research aim of this study. The application is based on the transport and reaction of a low-pH poly(acrylic acid) polymer through fractures in strongly alkaline cement. The pH-sensitive microgels viscosify upon neutralization with cement to become highly swollen gels with substantial yield stress that can block fluid flow. Experiments in a cement fracture determined the effects of the viscosification and gel deposition via real-time visual observation and measurements of pressure gradient and effluent pH. While the pH-triggered gelling mechanism and rheology measurements of the neutralized polymer gel show promising results, the polymer solution in contact with cement undergoes an undesirable reaction known as polymer syneresis. Syneresis is caused by the release of calcium cation from cement that collapses the polymer network. Syneresis produces an unstable calcium-precipitation byproduct that is detrimental to the strength and stability of the gel in place. As a result, gel-sealed leakage pathways that subjected to various degrees of syneresis often failed to hold back pressures. Several chemicals were studied to inhibit polymer syneresis and tested for pretreatment of cement cores to remove calcium and prevent syneresis during polymer placement. A chelating agent, sodium triphosphate (Na 5P 3O 10), was found to successfully eliminate syneresis without compromising the injectivity of polymer solution during placement. Polymer gel strength is determined by recording the maximum holdback pressure gradients during liquid breakthrough tests after various periods of pretreatment and polymer shut-in time. Cores pretreated with Na 5P 3O 10 successfully held up to an average of 80 psi/ft, which is significantly greater than the expected threshold value of about 0.1-5 psi/ft required to prevent flow in a typical CO 2 leakage scenario. The use of such inexpensive, pH-triggered poly-acrylic acid polymer allows long-term robust seal of leaky wellbores under high pH conditions.« less

Ionically conducting PVA-LiClO4 gel electrolyte for high performance flexible solid state supercapacitors.

PubMed

Chodankar, Nilesh R; Dubal, Deepak P; Lokhande, Abhishek C; Lokhande, Chandrakant D

2015-12-15

The synthesis of polymer gel electrolyte having high ionic conductivity, excellent compatibility with active electrode material, mechanical tractability and long life is crucial to obtain majestic electrochemical performance for flexible solid state supercapacitors (FSS-SCs). Our present work describes effect of different polymers gel electrolytes on electrochemical properties of MnO2 based FSS-SCs device. It is revealed that, MnO2-FSS-SCs with polyvinyl alcohol (PVA)-Lithium perchlorate (LiClO4) gel electrolyte demonstrate excellent electrochemical features such as maximum operating potential window (1.2V), specific capacitance of 112Fg(-1) and energy density of 15Whkg(-1) with extended cycling stability up to 2500CV cycles. Moreover, the calendar life suggests negligible decrease in the electrochemical performance of MnO2-FSS-SCs after 20days. Copyright © 2015 Elsevier Inc. All rights reserved.

Investigation of Preparation and Mechanisms of a Dispersed Particle Gel Formed from a Polymer Gel at Room Temperature

PubMed Central

Zhao, Guang; Dai, Caili; Zhao, Mingwei; You, Qing; Chen, Ang

2013-01-01

A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles. PMID:24324817

Nanoparticle solutions as adhesives for gels and biological tissues

NASA Astrophysics Data System (ADS)

Rose, Séverine; Prevoteau, Alexandre; Elzière, Paul; Hourdet, Dominique; Marcellan, Alba; Leibler, Ludwik

2014-01-01

Adhesives are made of polymers because, unlike other materials, polymers ensure good contact between surfaces by covering asperities, and retard the fracture of adhesive joints by dissipating energy under stress. But using polymers to `glue' together polymer gels is difficult, requiring chemical reactions, heating, pH changes, ultraviolet irradiation or an electric field. Here we show that strong, rapid adhesion between two hydrogels can be achieved at room temperature by spreading a droplet of a nanoparticle solution on one gel's surface and then bringing the other gel into contact with it. The method relies on the nanoparticles' ability to adsorb onto polymer gels and to act as connectors between polymer chains, and on the ability of polymer chains to reorganize and dissipate energy under stress when adsorbed onto nanoparticles. We demonstrate this approach by pressing together pieces of hydrogels, for approximately 30 seconds, that have the same or different chemical properties or rigidities, using various solutions of silica nanoparticles, to achieve a strong bond. Furthermore, we show that carbon nanotubes and cellulose nanocrystals that do not bond hydrogels together become adhesive when their surface chemistry is modified. To illustrate the promise of the method for biological tissues, we also glued together two cut pieces of calf's liver using a solution of silica nanoparticles. As a rapid, simple and efficient way to assemble gels or tissues, this method is desirable for many emerging technological and medical applications such as microfluidics, actuation, tissue engineering and surgery.

How do monomeric components of a polymer gel dosimeter respond to ionising radiation: A steady-state radiolysis towards preparation of a 3D polymer gel dosimeter

NASA Astrophysics Data System (ADS)

Kozicki, Marek

2011-12-01

Ionising radiation-induced reactions of aqueous single monomer solutions and mixtures of poly(ethylene glycol) diacrylate (PEGDA) and N, N'-methylenebisacrylamide (Bis) in a steady-state condition are presented below and above gelation doses in order to highlight reactions in irradiated 3D polymer gel dosimeters, which are assigned for radiotherapy dosimetry. Both monomers are shown to undergo radical polymerisation and cross-linking, which result in the measured increase in molecular weight and radius of gyration of the formed polydisperse polymer coils. The formation of nanogels was also observed for Bis solutions at a low concentration. In the case of PEGDA-Bis mixtures, co-polymerisation is suggested as well. At a sufficiently high radiation dose, the formation of a polymer network was observed for both monomers and their mixture. For this reason a sol-gel analysis for PEGDA and Bis was performed gravimetrically and a proposition of an alternative to this method employing a nuclear magnetic resonance technique is made. The two monomers were used for preparation of 3D polymer gel dosimeters having the acronyms PABIG and PABIG nx. The latter is presented for the first time in this work and is a type of the formerly established PABIG polymer gel dosimeter. The elementary characteristics of the new composition are presented, underlining the ease of its preparation, low dose threshold, and slightly increased sensitivity but lower quasi-linear range of dose response in comparison to PABIG.

Strong poly(ethylene oxide) based gel adhesives via oxime cross-linking.

PubMed

Ghosh, Smita; Cabral, Jaydee D; Hanton, Lyall R; Moratti, Stephen C

2016-01-01

There is a demand for materials to replace or augment the use of sutures and staples in surgical procedures. Currently available commercial surgical adhesives provide either high bond strength with biological toxicity or polymer and protein-based products that are biologically acceptable (though with potential sensitizing potential) but have much reduced bond strength. It is desirable to provide novel biocompatible and biodegradable surgical adhesives/sealants capable of high strength with minimal immune or inflammatory response. In this work, we report the end group derivatization of 8-arm star PEOs with aldehyde and amine end groups. Gels were prepared employing the Schiff-base chemistry between the aldehydes and the amines. Gel setting times, swelling behavior and rheological characterization were carried out for these gels. The mechanical-viscoelastic properties were found to be directly proportional to the crosslinking density of the gels, the 10K PEO gel was stiffer in comparison to the 20K PEO gel. The adhesive properties of these gels were tested using porcine skin and showed excellent adhesion properties. Cytotoxicity studies were carried out for the individual gel components using two different methods: (a) Crystal Violet Staining assay (CVS assay) and (b) impedance and cell index measurement by the xCELLigence system at concentrations >5%. Gels prepared by mixing 20% w/w solutions were also tested for cytotoxicity. The results revealed that the individual gel components as well as the prepared gels and their leachables were non-cytotoxic at these concentrations. This work presents a new type of glue that is aimed at surgery applications using a water soluble star shaped polymer. It show excellent adhesion to skin and is tough and easy to use. We show that it is very biocompatible based on tests on live human cells, and could therefore in principle be used for internal surgery. Comparison with other reported and commercial glues shows that it is stronger than most, and does not swell in water to the same degree as many other water based bioadhesives. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In situ measurements of the optical absorption of dioxythiophene-based conjugated polymers

NASA Astrophysics Data System (ADS)

Hwang, J.; Schwendeman, I.; Ihas, B. C.; Clark, R. J.; Cornick, M.; Nikolou, M.; Argun, A.; Reynolds, J. R.; Tanner, D. B.

2011-05-01

Conjugated polymers can be reversibly doped by electrochemical means. This doping introduces new subband-gap optical absorption bands in the polymer while decreasing the band-gap absorption. To study this behavior, we have prepared an electrochemical cell allowing in situ measurements of the optical properties of the polymer. The cell consists of a thin polymer film deposited on gold-coated Mylar behind which is another polymer that serves as a counterelectrode. An infrared transparent window protects the upper polymer from ambient air. By adding a gel electrolyte and making electrical connections to the polymer-on-gold films, one may study electrochromism in a wide spectral range. As the cell voltage (the potential difference between the two electrodes) changes, the doping level of the conjugated polymer films is changed reversibly. Our experiments address electrochromism in poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-dimethylpropylenedioxythiophene) (PProDOT-Me2). This closed electrochemical cell allows the study of the doping induced subband-gap features (polaronic and bipolaronic modes) in these easily oxidized and highly redox switchable polymers. We also study the changes in cell spectra as a function of polymer thickness and investigate strategies to obtain cleaner spectra, minimizing the contributions of water and gel electrolyte features.

Nano-sponge ionic liquid-polymer composite electrolytes for solid-state lithium power sources

NASA Astrophysics Data System (ADS)

Liao, Kang-Shyang; Sutto, Thomas E.; Andreoli, Enrico; Ajayan, Pulickel; McGrady, Karen A.; Curran, Seamus A.

Solid polymer gel electrolytes composed of 75 wt.% of the ionic liquid, 1- n-butyl-2,3-dimethylimidazolium bis-trifluoromethanesulfonylimide with 1.0 M lithium bis-trifluoromethanesulfonylimide and 25 wt.% poly(vinylidenedifluoro-hexafluoropropene) are characterized as the electrolyte/separator in solid-state lithium batteries. The ionic conductivity of these gels ranges from 1.5 to 2.0 mS cm -1, which is several orders of magnitude more conductive than any of the more commonly used solid polymers, and comparable to the best solid gel electrolytes currently used in industry. TGA indicates that these polymer gel electrolytes are thermally stable to over 280 °C, and do not begin to thermally decompose until over 300 °C; exhibiting a significant advancement in the safety of lithium batteries. Atomic force microscopy images of these solid thin films indicate that these polymer gel electrolytes have the structure of nano-sponges, with a sub-micron pore size. For these thin film batteries, 150 charge-discharge cycles are run for Li xCoO 2 where x is cycled between 0.95 down to 0.55. Minimal internal resistance effects are observed over the charging cycles, indicating the high ionic conductivity of the ionic liquid solid polymer gel electrolyte. The overall cell efficiency is approximately 98%, and no significant loss in battery efficiency is observed over the 150 cycles.

Comparison of starch and gelatin hydrogels for non-toxic supercapacitor electrolytes

NASA Astrophysics Data System (ADS)

Railanmaa, Anna; Lehtimäki, Suvi; Lupo, Donald

2017-06-01

Starch and gelatin are two of the most abundantly available natural polymers. Their non-toxicity, low cost, and compatibility with aqueous solvents make them ideal for use in ubiquitous, environmentally friendly electronics systems. This work presents the results of conductivity measurements through impedance spectroscopy for gelatin- and starch-based aqueous gel electrolytes. The NaCl-based gels were physically cross-linked. The conductivity values were 84.6 mS/cm at 1.5 mol L-1 and 71.5 mS/cm at 2 mol L-1 for gelatin and starch, respectively. The mechanical properties of gelatin were found preferable to those of starch, although they deteriorated significantly when the salt concentration exceeded 2 mol L-1. The ability of the gels to successfully act as a supercapacitor electrolyte was demonstrated with printed electrodes on plastic substrate. The devices were characterized through cyclic voltammetry measurements. The results imply that these polymer gel electrolytes are very promising for replacing the traditional aqueous liquid electrolytes in supercapacitors in applications where, for example, user and environmental safety is essential.

Design of electro-active polymer gels as actuator materials

NASA Astrophysics Data System (ADS)

Popovic, Suzana

Smart materials, alternatively called active or adaptive, differ from passive materials in their sensing and activation capability. These materials can sense changes in environment such as: electric field, magnetic field, UV light, pH, temperature. They are capable of responding in numerous ways. Some change their stiffness properties (electro-rheological fluids), other deform (piezos, shape memory alloys, electrostrictive materials) or change optic properties (electrochromic polymers). Polymer gels are one of such materials which can change the shape, volume and even optical properties upon different applied stimuli. Due to their low stiffness property they are capable of having up to 100% of strain in a short time, order of seconds. Their motion resembles the one of biosystems, and they are often seen as possible artificial muscle materials. Despite their delicate nature, appropriate design can make them being used as actuator materials which can form controllable surfaces and mechanical switches. In this study several different groups of polymer gel material were investigated: (a) acrylamide based gels are sensitive to pH and electric field and respond in volume change, (b) polyacrylonitrile (PAN) gel is sensitive to pH and electric field and responds in axial strain and bending, (c) polyvinylalcohol (PVA) gel is sensitive to electric field and responds in axial strain and bending and (d) perfluorinated sulfonic acid membrane, Nafion RTM, is sensitive to electric field and responds in bending. Electro-mechanical and chemo-mechanical behavior of these materials is a function of a variety of phenomena: polymer structure, affinity of polymer to the solvent, charge distribution within material, type of solvent, elasticity of polymer matrix, etc. Modeling of this behavior is a task aimed to identify what is driving mechanism for activation and express it in a quantitative way in terms of deformation of material. In this work behavior of the most promising material as an actuator material, Nafion 117, was simulated. It was suggested that dominant phenomenon causing the material deformation is non-uniform water distribution within a material, that causes it to expand on one side and shrink on the other, macroscopically inducing bending of membrane. Uneven distribution of water is believed to be under the influence of two processes, electroosmosis and self-diffusion of free water.

A rheological assessment of the nature of interactions between mucoadhesive polymers and a homogenised mucus gel.

PubMed

Madsen, F; Eberth, K; Smart, J D

1998-06-01

The ability of mucoadhesive materials to produce a large increase in the resistance to deformation when incorporated into a mucus gel, relative to when the mucus gel and test materials are evaluated separately at the same concentration, has been reported in several previous studies. It has been proposed that this phenomenon, termed rheological synergism, can be used as a measure of the strength of the mucoadhesive interaction. This study investigated the interactions between four putative mucoadhesive polymers (Noveon, Pemulen TR-2, carageenan and sodium carboxymethylcellulose) and a homogenised mucus gel, using dynamic oscillatory rheology. It was shown that, with the exception of sodium carboxymethylcellulose, incorporating a mucoadhesive polymer into a mucus gel produces rheological behaviour indicative of a weakly cross-linked gel network, which suggested a structure containing physical chain entanglements and non-covalent (probably hydrogen) bonds. Optimum gel strengthening occurred in a weakly acidic environment, suggesting an optimum conformation and degree of ionisation of the polymer and mucus molecules. Subsequent work suggested that the macromolecular interactions between polymer and mucus are sensitive to temperature, with the dynamic moduli decreasing with increasing temperature, further indicating bonding of a non-covalent nature. This work provide further evidence that rheological methods can be used as a tool to evaluate the interactions between a mucoadhesive macromolecule and a mucus gel. It also adds to the perception that molecular interpenetration may be an important factor in mucoadhesion by strengthening the mucus in the mucoadhesive/mucosal interfacial layer.

Evaluation of dose delivery accuracy of gamma knife using MRI polymer gel dosimeter in an inhomogeneous phantom

NASA Astrophysics Data System (ADS)

Pourfallah T, A.; Alam N, Riahi; M, Allahverdi; M, Ay; M, Zahmatkesh

2009-05-01

Polymer gel dosimetry is still the only dosimetry method for directly measuring three-dimensional dose distributions. MRI Polymer gel dosimeters are tissue equivalent and can act as a phantom material. Because of high dose response sensitivity, the MRI was chosen as readout device. In this study dose profiles calculated with treatment-planning software (LGP) and measurements with the MR polymer gel dosimeter for single-shot irradiations were compared. A custom-built 16 cm diameter spherical plexiglas head phantom was used in this study. Inside the phantom, there is a cubic cutout for insertion of gel phantoms and another cutout for inserting the inhomogeneities. The phantoms were scanned with a 1.5T MRI (Siemens syngo MR 2004A 4VA25A) scanner. The multiple spin-echo sequence with 32 echoes was used for the MRI scans. Calibration relations between the spin-spin relaxation rate and the absorbed dose were obtained by using small cylindrical vials, which were filled with the PAGAT polymer gel from the same batch as for the spherical phantom. 1D and 2D data obtained using gel dosimeter for homogeneous and inhomogeneous phantoms were compared with dose obtained using LGP calculation. The distance between relative isodose curves obtained for homogeneous phantom and heterogeneous phantoms exceed the accepted total positioning error (>±2mm). The findings of this study indicate that dose measurement using PAGAT gel dosimeter can be used for verifying dose delivering accuracy in GK unit in presence of inhomogeneities.

Responsive hydrogels--structurally and dimensionally optimized smart frameworks for applications in catalysis, micro-system technology and material science.

PubMed

Döring, Artjom; Birnbaum, Wolfgang; Kuckling, Dirk

2013-09-07

Although the technological and scientific importance of functional polymers has been well established over the last few decades, the most recent focus that has attracted much attention has been on stimuli-responsive polymers. This group of materials is of particular interest due to its ability to respond to internal and/or external chemico-physical stimuli, which is often manifested as large macroscopic responses. Aside from scientific challenges of designing stimuli-responsive polymers, the main technological interest lies in their numerous applications ranging from catalysis through microsystem technology and chemomechanical actuators to sensors that have been extensively explored. Since the phase transition phenomenon of hydrogels is theoretically well understood advanced materials based on the predictions can be prepared. Since the volume phase transition of hydrogels is a diffusion-limited process the size of the synthesized hydrogels is an important factor. Consistent downscaling of the gel size will result in fast smart gels with sufficient response times. In order to apply smart gels in microsystems and sensors, new preparation techniques for hydrogels have to be developed. For the up-coming nanotechnology, nano-sized gels as actuating materials would be of great interest.

DNA Based Electrolyte/Separator for Lithium Battery Application (Postprint)

DTIC Science & Technology

2015-10-07

Lithium - ion or sodium- ion ) batteries and the second are the gel polymer electrolyte (GPE) metal- ion batteries also known as metal- ion polymer...AFRL-RX-WP-JA-2016-0302 DNA BASED ELECTROLYTE/SEPARATOR FOR LITHIUM BATTERY APPLICATION (POSTPRINT) Jitendra Kumar1, Fahima...BASED ELECTROLYTE/SEPARATOR FOR LITHIUM BATTERY APPLICATION (POSTPRINT) 5a. CONTRACT NUMBER FA8650-15-D-5405-0001 5b. GRANT NUMBER 5c. PROGRAM

Microsponges based novel drug delivery system for augmented arthritis therapy

PubMed Central

Osmani, Riyaz Ali M.; Aloorkar, Nagesh H.; Ingale, Dipti J.; Kulkarni, Parthasarathi K.; Hani, Umme; Bhosale, Rohit R.; Jayachandra Dev, Dandasi

2015-01-01

The motive behind present work was to formulate and evaluate gel containing microsponges of diclofenac diethylamine to provide prolonged release for proficient arthritis therapy. Quasi-emulsion solvent diffusion method was implied using Eudragit RS-100 and microsponges with varied drug–polymer ratios were prepared. For the sake of optimization, diverse factors affecting microparticles physical properties were too investigated. Microsponges were characterized by SEM, DSC, FT-IR, XRPD and particle size analysis, and evaluated for morphology, drug loading, in vitro drug release and ex vivo diffusion as well. There were no chemical interactions between drug and polymers used as revealed by compatibility studies outcomes. The drug polymer ratio reflected notable effect on drug content, encapsulation efficiency and particle size. SEM results revealed spherical microsponges with porous surface, and had 7.21 μm mean particle size. The microsponges were then incorporated in gel; which exhibited viscous modulus along with pseudoplastic behavior. In vitro drug release results depicted that microsponges with 1:2 drug–polymer ratio were more efficient to give extended drug release of 75.88% at the end of 8 h; while conventional formulation get exhausted incredibly earlier by releasing 81.11% drug at the end of 4 h only. Thus the formulated microsponge-based gel of diclofenac diethylamine would be a promising alternative to conventional therapy for safer and efficient treatment of arthritis and musculoskeletal disorders. PMID:26594124

Microsponges based novel drug delivery system for augmented arthritis therapy.

PubMed

Osmani, Riyaz Ali M; Aloorkar, Nagesh H; Ingale, Dipti J; Kulkarni, Parthasarathi K; Hani, Umme; Bhosale, Rohit R; Jayachandra Dev, Dandasi

2015-10-01

The motive behind present work was to formulate and evaluate gel containing microsponges of diclofenac diethylamine to provide prolonged release for proficient arthritis therapy. Quasi-emulsion solvent diffusion method was implied using Eudragit RS-100 and microsponges with varied drug-polymer ratios were prepared. For the sake of optimization, diverse factors affecting microparticles physical properties were too investigated. Microsponges were characterized by SEM, DSC, FT-IR, XRPD and particle size analysis, and evaluated for morphology, drug loading, in vitro drug release and ex vivo diffusion as well. There were no chemical interactions between drug and polymers used as revealed by compatibility studies outcomes. The drug polymer ratio reflected notable effect on drug content, encapsulation efficiency and particle size. SEM results revealed spherical microsponges with porous surface, and had 7.21 μm mean particle size. The microsponges were then incorporated in gel; which exhibited viscous modulus along with pseudoplastic behavior. In vitro drug release results depicted that microsponges with 1:2 drug-polymer ratio were more efficient to give extended drug release of 75.88% at the end of 8 h; while conventional formulation get exhausted incredibly earlier by releasing 81.11% drug at the end of 4 h only. Thus the formulated microsponge-based gel of diclofenac diethylamine would be a promising alternative to conventional therapy for safer and efficient treatment of arthritis and musculoskeletal disorders.

Entropic trapping of macromolecules by mesoscopic periodic voids in a polymer hydrogel

NASA Astrophysics Data System (ADS)

Liu, Lei; Li, Pusheng; Asher, Sanford A.

1999-01-01

The separation of macromolecules such as polymers and DNA by means of electrophoresis, gel permeation chromatography or filtration exploits size-dependent differences in the time it takes for the molecules to migrate through a random porous network. Transport through the gel matrices, which usually consist of full swollen crosslinked polymers, depends on the relative size of the macromolecule compared with the pore radius. Sufficiently small molecules are thought to adopt an approximately spherical conformation when diffusing through the gel matrix, whereas larger ones are forced to migrate in a snake-like fashion. Molecules of intermediate size, however, can get temporarily trapped in the largest pores of the matrix, where the molecule can extend and thus maximize its conformational entropy. This `entropic trapping' is thought to increase the dependence of diffusion rate on molecular size. Here we report the direct experimental verification of this phenomenon. Bragg diffraction from a hydrogel containing a periodic array of monodisperse water voids confirms that polymers of different weights partition between the hydrogel matrix and the water voids according to the predictions of the entropic trapping theory. Our approach might also lead to the design of improved separation media based on entropic trapping.

Fabrication and characterization of polymer gel for MRI phantom with embedded lesion particles

NASA Astrophysics Data System (ADS)

In, Eunji; Naguib, Hani E.; Haider, Masoom

2012-04-01

Magnetic Resonance Imaging (MRI) is a medical imaging technique used in radiology to visualize the detailed internal structure and body soft tissues in complete 3D image. MRI performs best when optimal imaging parameters such as contrast, signal to noise ratio (SNR), spatial resolution and total scan time are utilized. However, due to a variety of imaging parameters that differ with the manufacturer, a calibration medium that allows the control of these parameters is necessary. Therefore, a phantom that behaves similar to human soft tissue is developed to replace a real human. Polymer gel is novel material that has great potential in the medical imaging. Since very few have focused on examining the behavior of polymer lesions, the motivation of this study is to develop a polymer gel phantom, especially for liver, with embedded lesions. Both the phantom and lesions should be capable of reflecting T1 and T2 relaxation values through various characterization processes. In this paper, phantom and lesion particles were fabricated with carrageenan as a gelling agent by physical aggregation. Agar was used as supplementary gelling agent and T2 modifier and Gd-DTPA as T1 modifier. The polymer gel samples were fabricated by varying the concentrations of the gelling agent, and T1 and T2 modifiers. The lesion particles were obtained by extracting molten polymer gel solution in chilled oil bath to obtain spherical shape. The polymer gel properties including density, elastic modulus, dielectric constant and optical properties were measured to compare with human tissue values for long period of time.

Lamellar biogels comprising fluid membranes with a newly synthesized class of polyethylene glycol-surfactants

NASA Astrophysics Data System (ADS)

Warriner, Heidi E.; Davidson, Patrick; Slack, Nelle L.; Schellhorn, Matthias; Eiselt, Petra; Idziak, Stefan H. J.; Schmidt, Hans-Werner; Safinya, Cyrus R.

1997-09-01

A series of four polymer-surfactant macromolecules, each consisting of a double-chain hydrophobic moiety attached onto a monofunctional polyethylene glycol (PEG) polymer chain, were synthesized in order to study their effect upon the fluid lamellar liquid crystalline (Lα) phase of the dimyristoylphosphatidylcholine/pentanol/water system. The main finding of this study is that the addition of these compounds induces a new lamellar gel, called Lα,g. We have determined the phase diagrams as a function of PEG-surfactant concentration, cPEG, and weight fraction water, ΦW. All phase diagrams are qualitatively similar and show the existence of the gel. Unlike more common polymer physical gels, this gel can be induced either by increasing cPEG or by adding water at constant cPEG. In particular, less polymer is required for gelation as water concentration increases. Moreover, the gel phase is attained at concentrations of PEG-surfactant far below that required for classical polymer gels and is stable at temperatures comparable to the lower critical solution temperature of free PEG-water mixtures. Small angle x-ray experiments demonstrate the lamellar structure of the gel phase, while wide angle x-ray scattering experiments prove that the structure is Lα, not Lβ' (a common chain-ordered phase which is also a gel). The rheological behavior of the Lα,g phase demonstrates the existence of three dimensional elastic properties. Polarized light microscopy of Lα,g samples reveals that the Lα,g is induced by a proliferation of defect structures, including whispy lines, spherulitic defects, and a nematiclike Schlieren texture. We propose a model of topological defects created by the aggregation of PEG-surfactant into highly curved regions within the membranes. This model accounts for both the inverse relationship between ΦW and cPEG observed along the gel transition line and the scaling dependence of the interlayer spacing at the gel transition with the PEG molecular weight. These Lα hydrogels could serve as the matrix for membrane-anchored peptides, proteins or other drug molecules, creating a "bioactive gel" with mechanical stability deriving from the polymer-lipid minority component.

Mechanism of Enhancement of Virus Plaques by Cationic Polymers

PubMed Central

Wallis, Craig; Melnick, Joseph L.

1968-01-01

It has been assumed that plaque enhancement by cationic polymers is due to their binding of sulfated polysaccharides in agar. However, viruses that are enhanced by cationic polymers, diethylaminoethyl-dextran, and protamine were found not to be inhibited by polyanions in agar under the usual overlay conditions. In the case of adenovirus, enhancement by protamine seems to be due to the protamine serving as a source of arginine; enzymes released from the cultured cells digest the protamine and provide a reservoir of arginine for the cells. Other viruses (herpes and echovirus types 3, 4, 5, and 6) known to be susceptible to agar inhibitors were found to be enhanced by cationic polymers even under starch gel and methylcellulose overlays, which are free of polyanions. Since cationic polymers enhance the diffusion of virus through agar or starch gel, plaque enhancement seems to be the result of the gel becoming positively charged so that viruses can move effectively through them. The observation that starch gel and methylcellulose enhance plaque formation with viruses known to be inhibited under agar was also reinvestigated. When the consistency of the agar gel was reduced to the same viscosity of starch gel and methylcellulose overlays, the same plaque counts and sizes were observed under all three overlays. PMID:4986901

3-V Solid-State Flexible Supercapacitors with Ionic-Liquid-Based Polymer Gel Electrolyte for AC Line Filtering.

PubMed

Kang, Yu Jin; Yoo, Yongju; Kim, Woong

2016-06-08

State-of-the-art solid-state flexible supercapacitors with sufficiently fast response speed for AC line filtering application suffer from limited energy density. One of the main causes of the low energy density is the low cell voltage (1 V), which is limited by aqueous-solution-based gel electrolytes. In this work, we demonstrate for the first time a 3-V flexible supercapacitor for AC line filtering based on an ionic-liquid-based polymer gel electrolyte and carbon nanotube electrode material. The flexible supercapacitor exhibits an areal energy density that is more than 20 times higher than that of the previously demonstrated 1-V flexible supercapacitor (0.66 vs 0.03 μWh/cm(2)) while maintaining excellent capacitive behavior at 120 Hz. The supercapacitor shows a maximum areal power density of 1.5 W/cm(2) and a time constant of 1 ms. The improvement of the cell voltage while maintaining the fast-response capability greatly improves the potential of supercapacitors for high-frequency applications in wearable and/or portable electronics.

Nanocrystal/sol-gel nanocomposites

DOEpatents

Klimov, Victor L.; Petruska, Melissa A.

2010-05-25

The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

Structure and Conductivity of Semiconducting Polymer Hydrogels.

PubMed

Huber, Rachel C; Ferreira, Amy S; Aguirre, Jordan C; Kilbride, Daniel; Toso, Daniel B; Mayoral, Kenny; Zhou, Z Hong; Kopidakis, Nikos; Rubin, Yves; Schwartz, Benjamin J; Mason, Thomas G; Tolbert, Sarah H

2016-07-07

Poly(fluorene-alt-thiophene) (PFT) is a conjugated polyelectrolyte that self-assembles into rod-like micelles in water, with the conjugated polymer backbone running along the length of the micelle. At modest concentrations (∼10 mg/mL in aqueous solutions), PFT forms hydrogels, and this work focuses on understanding the structure and intermolecular interactions in those gel networks. The network structure can be directly visualized using cryo electron microscopy. Oscillatory rheology studies further tell us about connectivity within the gel network, and the data are consistent with a picture where polymer chains bridge between micelles to hold the network together. Addition of tetrahydrofuran (THF) to the gels breaks those connections, but once the THF is removed, the gel becomes stronger than it was before, presumably due to the creation of a more interconnected nanoscale architecture. Small polymer oligomers can also passivate the bridging polymer chains, breaking connections between micelles and dramatically weakening the hydrogel network. Fits to solution-phase small-angle X-ray scattering data using a Dammin bead model support the hypothesis of a bridging connection between PFT micelles, even in dilute aqueous solutions. Finally, time-resolved microwave conductivity measurements on dried samples show an increase in carrier mobility after THF annealing of the PFT gel, likely due to increased connectivity within the polymer network.

Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method.

PubMed

Khosravi, H; Hashemi, B; Mahdavi, S R; Hejazi, P

2015-03-01

Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions. The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices. A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.

Ultra-low density microcellular polymer foam and method

DOEpatents

Simandl, Ronald F.; Brown, John D.

1996-01-01

An ultra-low density, microcellular open-celled polymer foam and a method for making such foam. A polymer is dissolved in a heated solution consisting essentially of at least one solvent for the dissolution of the polymer in the heated solution and the phase inversion of the dissolved polymer to a liquid gel upon sufficient cooling of the heated solution. The heated solution is contained in a containment means provided with a nucleating promoting means having a relatively rough surface formed of fixed nucleating sites. The heated solution is cooled for a period of time sufficient to form a liquid gel of the polymer by phase inversion. From the gel, a porous foam having a density of less than about 12.0 mg/cm.sup.3 and open porosity provided by well interconnected strut morphology is formed.

Ultra-low density microcellular polymer foam and method

DOEpatents

Simandl, R.F.; Brown, J.D.

1996-03-19

An ultra-low density, microcellular open-celled polymer foam and a method for making such foam are disclosed. A polymer is dissolved in a heated solution consisting essentially of at least one solvent for the dissolution of the polymer in the heated solution and the phase inversion of the dissolved polymer to a liquid gel upon sufficient cooling of the heated solution. The heated solution is contained in a containment means provided with a nucleating promoting means having a relatively rough surface formed of fixed nucleating sites. The heated solution is cooled for a period of time sufficient to form a liquid gel of the polymer by phase inversion. From the gel, a porous foam having a density of less than about 12.0 mg/cm{sup 3} and open porosity provided by well interconnected strut morphology is formed.

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

PubMed Central

Savina, Irina N.; Ingavle, Ganesh C.; Cundy, Andrew B.; Mikhalovsky, Sergey V.

2016-01-01

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200 μm in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400 ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications. PMID:26883390

Preparation and characterization of hydrophobic P(TFE) blend electrospun gel polymer electrolyte fibrous membranes for Li-O2 battery

NASA Astrophysics Data System (ADS)

Padmaraj, O.; Suthanthiraraj, S. Austin

2018-04-01

A novel stable electrospun gel polymer electrolyte [(100-x)% P(VdF-co-HFP)+(x)% P(TFE), (x = 5, 10, 15, 20, 25 & 30)/1 M Li(CF3SO2)2N-] fibrous membranes with an addition of various concentrations of hydrophobic P(TFE) polymer were prepared by an electrospinning technique. All the prepared electrospun polymer blend fibrous membranes were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, high resolution scanning electron microscopy techniques and water contact angle measurements. The newly developed electrospun pure and hydrophobic P(TFE) blend fibrous membranes were activated into separator-cum gel polymer electrolyte fibrous membranes by soaking in an electrolyte solution contains 1 M Li(CF3SO2)2N- in EC: PC (1:1, v/v) in an argon filled glove box. Among the various concentrations of hydrophobic P(TFE) blend polymer fibrous membranes, the electrospun gel polymer blend electrolyte with 5% P(TFE) showed low crystallinity, high thermal stability, high electrolyte uptake, good hydrophobicity and high ionic conductivity (2.680×10-2 S cm-1) at room temperature.

Ionic cross-linked polyether and silica gel mixed matrix membranes for CO 2 separation from flue gas

DOE PAGES

Sekizkardes, Ali K.; Zhou, Xu; Nulwala, Hunaid B.; ...

2017-09-22

Mixed matrix membranes (MMMs) were prepared by incorporating 10 wt%, 20 wt% and 30 wt% silica gel filler particles into novel ionic cross-linked polyether (IXPE) polymers. Porous silica gel has the advantage of high surface area that can increase the free volume and permeability in a polymer film while also being commercially available and low cost. The MMMs featured high chemical and thermal stability as well as a modest improvement in storage modulus. These features are due to the excellent interfacial interaction between silica gel filler particles and the polymer matrix. Increasing the loading of silica gel particles in MMMsmore » resulted in higher permeability up to 120 Barrer for CO 2, which is about 40% higher than the neat polymer matrix. Finally, most importantly, the MMMs maintained a very high CO 2/N 2 selectivity performance of around 41 for all particle loadings that were tested.« less

Dosimetry Evolution in Teletherapy: Polimer Gel

NASA Astrophysics Data System (ADS)

Hamann, J. H.; Peixoto, J. G. P.

2018-03-01

Polymer gels evolution and chemical composition used in dosimetry. Type Composition First gels Folin’s Phenol or Gallic Acid Polymer Gel Agarose and N,N’-methylene-bis-acrylamide BANANA Bis, acrylamide, nitrous oxide and agarose BANG-1TM Bis, acrylamide, nitrogen and gelatin BANG-2TM Bis, acrylic acid, sodium hydroxide, nitrogen and gelatin BANG-3TM Bis, methacrylate acid, sodium hydroxide, nitrogen and gelatin MAGIC Methacrylate acid, ascorbic acid, gelatin and copper sulphate

Microstructural aspects in steel fiber reinforced acrylic emulsion polymer modified concrete

NASA Astrophysics Data System (ADS)

Hazimmah, Dayang; Ayob, Afizah; Sie Yee, Lau; Chee Cung, Wong

2018-03-01

Scanning electron microscope observations of polymer-free and polymer-modified cements have shown that the polymer particles are partitioned between the inside of hydrates and the surface of anhydrous cement grains. For optimum dosage of acrylic emulsion polymer with 2.5%, the C-S-H gel in this structure is finer and more acicular. Some polymer adheres or deposit on the surface of the C-S-H gel. The presence of acrylic emulsion polymer confines the ionic diffusion so that the Ca(OH)2 crystallized locally to form fine crystals. The void in the structures seems to be smaller but no polymer films appears to be bridging the walls of pores although many polymer bonds or C-S-H spread into the pore spaces. In addition to porosity reduction, acrylic emulsion polymer modified the hydration products in the steel fiber -matrix ITZ. The hydration product C-S-H appeared as a needle like shape. The needle-shaped C-S-H increases and gradually formed the gel, with needles growing into the pore space. The phenomenon is more obvious as curing age increased.

Study on Movable gel Profiling/Flooding System Optimization at Boundary Temperature

NASA Astrophysics Data System (ADS)

Gao, Shanshan; Xie, Gang; Zhang, Tiantian; Wang, Zhiqiang; Jiang, Peijun; Wei, Junjie; Gu, Yi; Lei, Xiaoyang; Guo, Suzhen; Lei, Shi

2017-12-01

65-75°C is the boundary temperature of phenol-formaldehyde resin and organic chrome crosslink with HPAM to generate movable gel. Generally speaking, when the reservoir temperature is below 65-75°C, the crosslinking agent is Organic chrome. Phenol-formaldehyde resin is used when the temperature is above 65-75°C. In this paper the gelation properties of phenol-formaldehyde resin and organic chrome were compared at 70°C. The experiment results showed that the crosslinking time of phenol-formaldehyde resin gel was longer and more conducive to field injection. In addition the phenol-formaldehyde resin gel had greater viscosity, adhesion and shearing resistance compared with the organic chrome gel. So the phenol-formaldehyde resin was chosen for further optimization. The crosslinking time was shortened and the gel viscosity increased with the increase of the polymer concentration. As the polymer crosslinker proportion increased The crosslinking time was shortened and the gel viscosity increased first and then decreased. Reinforcer NC and stabilizer WG were added to improve the temperature and salt tolerance of the gel. The gel formula suitable for the boundary temperature was obtained. The optimum polymer concentration is 1200mg/L, the polymer crosslinker proportion is 1:1.1, the best reinforcer concentration is 400mg/L and the concentration of the stabilizer is 150mg/L. The crosslinking time is 31h, the gel viscosity is above 2100mPa·s. The gel did not shrink and no water separation was observed at 70°C for 150 days. The viscosity retention rate was more than 70%.

Smart membranes: Hydroxypropyl cellulose for flavor delivery

NASA Astrophysics Data System (ADS)

Heitfeld, Kevin A.

2007-12-01

This work focuses on the use of temperature responsive gels (TRGs) (polymeric hydrogels with a large temperature-dependent change in volume) for flavor retention at cooking temperatures. Specifically, we have studied a gel with a lower critical solution temperature (LCST) that swells at low temperatures and collapses at high temperatures. In the collapsed state, the polymer acts as a transport barrier, keeping the volatile flavors inside. An encapsulation system was designed to utilize the solution (phase separation) behavior of a temperature responsive gel. The gel morphology was understood and diffusive properties were tailored through morphology manipulation. Heterogeneous and homogeneous gels were processed by understanding the effect of temperature on gel morphology. A morphology model was developed linking bulk diffusive properties to molecular morphology. Flavor was encapsulated within the gel and the emulsifying capability was determined. The capsules responded to temperature similarly to the pure polymer. The release kinetcs were compared to commercial gelatin capsules and the temperature responsive polymer took longer to release.

Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

2015-12-01

The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton's law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization.

Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization.

PubMed

Sen, Swati; Kundagrami, Arindam

2015-12-14

The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton's law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization.

Synthesis, characterization and evaluation of thiolated tamarind seed polysaccharide as a mucoadhesive polymer.

PubMed

Kaur, Harmanmeet; Yadav, Shikha; Ahuja, Munish; Dilbaghi, Neeraj

2012-11-06

In the present study, thiol-functionalization of tamarind seed polysaccharide was carried out by esterification with thioglycolic acid. Thiol-functionalization was confirmed by SH stretch in Fourier-transformed infra-red spectra at 2586 cm(-1). It was found to possess 104.5 mM of thiol groups per gram. The results of differential scanning calorimetry and X-ray diffraction study indicate increase in crystallinity. Polymer compacts of thiolated tamarind seed polysaccharide required 6.85-fold greater force to detach from the mucin coated membrane than that of tamarind seed polysaccharide. Comparative evaluation of Carbopol-based metronidazole gels containing thiolated tamarind seed polysaccharide with gels containing tamarind seed polysaccharide for mucoadhesive strength using chicken ileum by modified balance method revealed higher mucoadhesion of gels containing thiolated tamarind seed polysaccharide. Further, the gels containing tamarind seed polysaccharide and thiolated tamarind seed polysaccharide released the drug by Fickian-diffusion following the first-order and Higuchi's-square root release kinetics, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Water-Hydrogel Binding Affinity Modulates Freeze-Drying-Induced Micropore Architecture and Skeletal Myotube Formation.

PubMed

Rich, Max H; Lee, Min Kyung; Marshall, Nicholas; Clay, Nicholas; Chen, Jinrong; Mahmassani, Ziad; Boppart, Marni; Kong, Hyunjoon

2015-08-10

Freeze-dried hydrogels are increasingly used to create 3D interconnected micropores that facilitate biomolecular and cellular transports. However, freeze-drying is often plagued by variance in micropore architecture based on polymer choice. We hypothesized that water-polymer binding affinity plays a significant role in sizes and numbers of micropores formed through freeze-drying, influencing cell-derived tissue quality. Poly(ethylene glycol)diacrylate (PEGDA) hydrogels with alginate methacrylate (AM) were used due to AM's higher binding affinity for water than PEGDA. PEGDA-AM hydrogels with larger AM concentrations resulted in larger sizes and numbers of micropores than pure PEGDA hydrogels, attributed to the increased mass of water binding to the PEGDA-AM gel. Skeletal myoblasts loaded in microporous PEGDA-AM hydrogels were active to produce 3D muscle-like tissue, while those loaded in pure PEGDA gels were localized on the gel surface. We propose that this study will be broadly useful in designing and improving the performance of various microporous gels.

Box-like gel capsules from heterostructures based on a core-shell MOF as a template of crystal crosslinking.

PubMed

Ishiwata, Takumi; Michibata, Ayano; Kokado, Kenta; Ferlay, Sylvie; Hosseini, Mir Wais; Sada, Kazuki

2018-02-06

New polymer capsules (PCs) were obtained using a crystal crosslinking (CC) method on core-shell MOF crystals. The latter are based on the epitaxial growth of two isostructural coordination polymers which are then selectively crosslinked. Decomposition of the non-reticulated phase leads to new PCs, possessing a well-defined hollow cubic shape reflecting the heterostructure of the template.

Three-dimensional radiation dosimetry using polymer gel and solid radiochromic polymer: From basics to clinical applications

PubMed Central

Watanabe, Yoichi; Warmington, Leighton; Gopishankar, N

2017-01-01

Accurate dose measurement tools are needed to evaluate the radiation dose delivered to patients by using modern and sophisticated radiation therapy techniques. However, the adequate tools which enable us to directly measure the dose distributions in three-dimensional (3D) space are not commonly available. One such 3D dose measurement device is the polymer-based dosimeter, which changes the material property in response to radiation. These are available in the gel form as polymer gel dosimeter (PGD) and ferrous gel dosimeter (FGD) and in the solid form as solid plastic dosimeter (SPD). Those are made of a continuous uniform medium which polymerizes upon irradiation. Hence, the intrinsic spatial resolution of those dosimeters is very high, and it is only limited by the method by which one converts the dose information recorded by the medium to the absorbed dose. The current standard methods of the dose quantification are magnetic resonance imaging, optical computed tomography, and X-ray computed tomography. In particular, magnetic resonance imaging is well established as a method for obtaining clinically relevant dosimetric data by PGD and FGD. Despite the likely possibility of doing 3D dosimetry by PGD, FGD or SPD, the tools are still lacking wider usages for clinical applications. In this review article, we summarize the current status of PGD, FGD, and SPD and discuss the issue faced by these for wider acceptance in radiation oncology clinic and propose some directions for future development. PMID:28396725

Control of gel swelling and phase separation of weakly charged thermoreversible gels by salt addition

PubMed Central

Solis, Francisco J.; Vernon, Brent

2009-01-01

Doping of thermoreversible polymer gels with charged monomers provides a way to control phase separation and gelation conditions by coupling the properties of the gel with a tunable ionic environment. We analyze the dependence of the gelation and phase separation conditions on the amount of salt present using a mean field model of weakly charged associative polymers. The ions and co-ions present are explicitly considered at the mean field level, and we determine their concentrations in the different equilibrium phases when the system undergoes phase separation. For weak polymer charge, the entropic contributions of the ions to the free energy of the system play a central role in the determination of the location of phase equilibrium. In the simplest case, when the associative interaction responsible for gel formation is independent of the electrostatic interaction, the addition of salt changes the polymer equilibrium concentrations and indirectly changes the measurable swelling of the gel. We construct phase diagrams of these systems showing the location of the coexistence region, the gel-sol boundary and the location of the tie-lines. We determine the swelling of the gel within the co-existence region. Our main result is that the description of the effect of the salt on the properties of the weakly charged gel can be described through an extra contribution to the effective immiscibility parameter χ proportional to the square of the doping degree f2 and to the inverse square of the added salt concentration s−2. PMID:19759854

Thermosensitive In Situ Gel Based on Solid Dispersion for Rectal Delivery of Ibuprofen.

PubMed

Liu, Yangdan; Wang, Xin; Liu, Youping; Di, Xin

2018-01-01

The objective of this study was to develop a thermosensitive in situ gel based on solid dispersions (SDs) for rectal delivery of ibuprofen (IBU). Thermosensitive (poloxamer 407) and mucoadhesive (hydroxypropylmethyl cellulose E5 and sodium alginate) polymers were used to prepare the in situ gel and the sol-gel transition temperature (T sol-gel ) and gel strength were optimized. The in vitro release performance and in vivo pharmacokinetic properties of the in situ gel after their rectal administration to rabbits were investigated. Compared with the solid suppository, the cumulative release of the IBU SDs loaded in situ gel was significantly increased. The in vivo pharmacokinetics indicated that in situ gel had a higher peak plasma concentration (C max ) and area under the curve (AUC (0-∞) ) in plasma than the solid suppositories. Histopathology results showed that the IBU in situ gel given at a dose of 15 mg/kg did not produce any irritation. In conclusion, this study suggested that the in situ gel could be an effective rectal formulation for IBU.

Method for molding ceramic powders using a water-based gel casting

DOEpatents

Janney, Mark A.; Omatete, Ogbemi O.

1991-07-02

A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant, and a monomer solution. The monomer solution includes at least one monofunctional monomer and at least one difunctional monomer, a free-radical initiator, and a aqueous solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product any be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, whereafter the product may be sintered.

Method for molding ceramic powders using a water-based gel casting process

DOEpatents

Jenny, Mark A.; Omalete, Ogbemi O.

1992-09-08

A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant, and a monomer solution. The monomer solution includes at least one monofunctional monomer and at least one difunctional monomer, a free-radical initiator, and a aqueous solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product may be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, whereafter the product may be sintered.

In vitro and in vivo characteristics of a thermogelling rectal delivery system of etodolac.

PubMed

Barakat, Nahla S

2009-01-01

Rectal etodolac-Poloxamer gel systems composed of Poloxamer and bioadhesive polymers were developed and evaluated. Hydroxypropylmethyl cellulose, poly)vinyl) pyrrolidone, methyl cellulose, hydroxyethylcellulose, and carbopol were examined as mucoadhesive polymers. The characteristics of the rectal gels differed according to the properties of mucoadhesive polymers. The physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations were investigated. The analysis of release mechanism showed that the release of etodolac was proportional to the square root of time, indicating that etodolac might be released from the suppositories by Fickian diffusion. The anti-inflammatory effect of etodolac-Poloxamer gel system was also studied in rats. Moreover, liquid suppository of etodolac did not cause any morphological damage to the rectal tissues. These results suggested that in situ gelling liquid suppository with etodolac and mucoadhesive polymer was a physically safe, convenient, and effective rectal dosage form for etodolac.

The properties of water in swollen cross-linked polystyrene sulfo acids

NASA Astrophysics Data System (ADS)

Gagarin, A. N.; Tokmachev, M. G.; Kovaleva, S. S.; Ferapontov, N. B.

2008-11-01

The properties of water in polystyrene sulfo acid gels with various cross-linking degrees were studied by optical volumetry and dynamic desorption porosimetry. The isotherms of water desorption obtained by dynamic desorption porosimetry coincided with isopiestic isotherms, which allowed this method to be recommended for the determination of the amount of water in polymer gels. Joint optical volumetry and dynamic desorption porosimetry studies showed that the interphase boundary in the cross-liked hydrophilic polymer-water system did not coincide with the visible gel boundary, because gels were two-phase systems, which contained water of two types, “free” and “bound.” The influence of the degree of polymer cross-linking on the amounts and properties of water of the two types was studied. It was shown that constants of water distribution in the polymer could be calculated from the dynamic desorption porosimetry data.

Formulation development and evaluation of innovative two-polymer (SR-2P) bioadhesive vaginal gel.

PubMed

Podaralla, Satheesh; Alt, Carsten; Shankar, Gita N

2014-08-01

The main objective of this investigation was to study the feasibility of developing a vaginal bioadhesive microbicide using a SRI's proprietary two-polymer gel platform (SR-2P). Several formulations were prepared with different combinations of temperature-sensitive polymer (Pluronic® F-127) and mucoadhesive polymer (Noveon® AA-1), producing gels of different characteristics. Prototype polymeric gels were evaluated for pH, osmolality, buffering capacity, and viscosity under simulated vaginal semen dilutions, and bioadhesivity using ex vivo mini pig vaginal tissues and texture analyzer. The pH of the polymeric gel formulations ranged from 5.1 to 6.4; the osmolality varied from 13 to 173 mOsm. Absolute viscosity ranged from 513 to 3,780 cPs, and was significantly reduced (1.5- to 3-fold) upon incubation with simulated vaginal and semen fluid mixture. Among the tested gels (indicated in the middle row as a molar ratio of a mixture of Noveon vs. Pluronic), only SR-2P retained gel structure upon dilution with simulated fluids and mild simulated coital stress. The pH of the SR-2P gel was maintained at about 4.6 in simulated vaginal fluid and also showed high peak force of adhesion in mini pig vaginal tissue. Furthermore, SR-2P gel caused no or only minimal irritation in a mouse vaginal irritation model. The results of this preliminary study demonstrated the potential application of SR-2P gel as a vaginal microbicide vehicle for delivery of anti-HIV agents.

MAGIC with formaldehyde applied to dosimetry of HDR brachytherapy source

NASA Astrophysics Data System (ADS)

Marques; T; Fernandes; J; Barbi; G; Nicolucci; P; Baffa; O

2009-05-01

The use of polymer gel dosimeters in brachytherapy can allow the determination of three-dimensional dose distributions in large volumes and with high spatial resolution if an adequate calibration process is performed. One of the major issues in these experiments is the polymer gel response dependence on dose rate when high dose rate sources are used and the doses in the vicinity of the sources are to be determinated. In this study, the response of a modified MAGIC polymer gel with formaldehyde around an Iridium-192 HDR brachytherapy source is presented. Experimental results obtained with this polymer gel were compared with ionization chamber measurements and with Monte Carlo simulation with PENELOPE. A maximum difference of 3.10% was found between gel dose measurements and Monte Carlo simulation at a radial distance of 18 mm from the source. The results obtained show that the gel's response is strongly influenced by dose rate and that a different calibration should be used for the vicinity of the source and for regions of lower dose rates. The results obtained in this study show that, provided the proper calibration is performed, MAGIC with formaldehyde can be successfully used to accurate determinate dose distributions form high dose rate brachytherapy sources.

π-Conjugated polymer anisotropic organogel nanofibrous assemblies for thermoresponsive photonic switches.

PubMed

Narasimha, Karnati; Jayakannan, Manickam

2014-11-12

The present work demonstrates one of the first examples of π-conjugated photonic switches (or photonic wave plates) based on the tailor-made π-conjugated polymer anisotropic organogel. New semicrystalline segmented π-conjugated polymers are designed with rigid aromatic oligophenylenevinylene π-core and flexible alkyl chain along the polymer backbone. These polymers are found to be self-assembled as semicrystalline or amorphous with respect to the number of carbon atoms in the alkyl units. These semicrystalline polymers produce organogels having nanofibrous morphology of 20 nm thickness with length up to 5 μm. The polymer organogel is aligned in a narrow glass capillary, and this anisotropic gel device is further demonstrated as photonic switches. The glass capillary device behaves as typical λ/4 photonic wave plates upon the illumination of the plane polarized light. The λ/4 photonic switching ability is found to be maximum at θ = 45° angle under the cross polarizers. The orthogonal arrangements of the gel capillaries produce dark and bright spots as on-and-off optical switches. Thermoreversibility of the polymer organogel (also its xerogel) was exploited to construct thermoresponsive photonic switches for the temperature window starting from 25 to 160 °C. The organic photonic switch concept can be adapted to large number of other π-conjugated materials for optical communication and storage.

Fabrication of highly uniform and porous MgF2 anti-reflective coatings by polymer-based sol-gel processing on large-area glass substrates.

PubMed

Raut, Hemant Kumar; Dinachali, Saman Safari; Ansah-Antwi, Kwadwo Konadu; Ganesh, V Anand; Ramakrishna, Seeram

2013-12-20

Despite recent progress in the fabrication of magnesium fluoride (MgF2) anti-reflective coatings (ARCs), simple, effective and scalable sol-gel fabrication of MgF2 ARCs for large-area glass substrates has prospective application in various optoelectronic devices. In this paper, a polymer-based sol-gel route was devised to fabricate highly uniform and porous MgF2 ARCs on large-area glass substrates. A sol-gel precursor made of polyvinyl acetate and magnesium trifluoroacetate assisted in the formation of uniformly mesoporous MgF2 ARCs on glass substrates, leading to the attainment of a refractive index of ~1.23. Systematic optimization of the thickness of the ARC in the sub-wavelength regime led to achieving ~99.4% transmittance in the case of the porous MgF2 ARC glass. Precise control of the thickness of porous MgF2 ARC glass also resulted in a mere ~0.1% reflection, virtually eliminating reflection off the glass surface at the target wavelength. Further manipulation of the thickness of the ARC on either side of the glass substrate led to the fabrication of relatively broadband, porous MgF2 ARC glass.

Development, Characterization, and Utilization of Food-Grade Polymer Oleogels.

PubMed

Davidovich-Pinhas, M; Barbut, Shai; Marangoni, A G

2016-01-01

The potential of organogels (oleogels) for oil structuring has been identified and investigated extensively using different gelator-oil systems in recent years. This review provides a comprehensive summary of all oil-structuring systems found in the literature, with an emphasis on ethyl-cellulose (EC), the only direct food-grade polymer oleogelator. EC is a semicrystalline material that undergoes a thermoreversible sol-gel transition in the presence of liquid oil. This unique behavior is based on the polymer's ability to associate through physical bonds. These interactions are strongly affected by external fields such as shear and temperature, as well as by solvent chemistry, which in turn strongly affect final gel properties. Recently, EC-based oleogels have been used as a replacement for fats in foods, as heat-resistance agents in chocolate, as oil-binding agents in bakery products, and as the basis for cosmetic pastes. Understanding the characteristics of the EC oleogel is essential for the development of new applications.

The viscoelastic effect in bending bucky-gel actuators

NASA Astrophysics Data System (ADS)

Kruusamäe, Karl; Mukai, Ken; Sugino, Takushi; Asaka, Kinji

2014-03-01

Electromechanically active polymers (EAP) are considered a good actuator candidate for a variety of reasons, e.g. they are soft, easy to miniaturize and operate without audible noise. The main structural component in EAPs is, as the name states, a type of deformable polymer. As polymers are known to exhibit a distinct mechanical response, the nature of polymer materials should never be neglected when characterizing and modeling the performance of EAP actuators. Bucky-gel actuators are a subtype of EAPs where ion-containing polymer membrane acts as an electronically insulating separator between two electrodes of carbon nanotubes and ionic liquid. In many occasions, the electrodes also contain polymer for the purpose of binding it together. Therefore, mechanically speaking, bucky-gel actuators are composite structures with layers of different mechanical nature. The viscoelastic response and the shape change property are perhaps the most characteristic effects in polymers. These effects are known to have high dependence on factors such as the type of polymer, the concentration of additives and the structural ratio of different layers. At the same time, most reports about optimization of EAP actuators describe the alteration of electromechanical performance dependent on the same factors. In this paper, the performance of bucky-gel actuators is measured as a function between the output force and bending deflection. It is observed that effective stiffness of these actuators depends on the input voltage. This finding is also supported by dynamic mechanical analysis which demonstrates that the viscoelastic response of bucky-gel laminate depends on both frequency and temperature. Moreover, the dynamic mechanical analysis reveals that in the range of standard operation temperatures, tested samples were in their glass transition region, which made it possible to alter their shape by using mechanical fixing. The mechanical fixity above 90% was obtained when high-frequency input signal was used to heat the bucky-gel sample.

Superabsorbent Multilayer Fabric

NASA Technical Reports Server (NTRS)

Coreale, J. V.; Dawn, F. S.

1982-01-01

Material contains gel-forming polymer and copolymer that absorb from 70 to 200 times their weight of liquid. Superabsorbent Polymer and Copolymer form gels to bind and retain liquid in multiply fabric. Until reaction between liquid and absorbent masses forms gel, backing layer retains liquids within fabric; also allows material to "breathe." Possible applications include baby diapers, female hygiene napkins, and hospital bedpads. Might also have uses in improvement of dry soil.

s-Triazine and tri-s-triazine based organic-inorganic hybrid gels prepared from chlorosilanes by exchange reactions.

PubMed

El-Gamel, Nadia E A; Schwarz, Marcus; Brendler, Erica; Kroke, Edwin

2006-12-07

Hybrid polymers [(DeltaO3)4Si3]n and [(DeltaO3)SiMe]n (where Delta = C6N7 or C3N3) have been prepared by a novel sol-gel process based on exchange reactions of MeSiCl3 or SiCl4 with C6N7(OSiMe3)3 and C3N3(OSiMe3)3.

Charge-regularized swelling kinetics of polyelectrolyte gels: Elasticity and diffusion

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

2017-11-01

We apply a recently developed method [S. Sen and A. Kundagrami, J. Chem. Phys. 143, 224904 (2015)], using a phenomenological expression of osmotic stress, as a function of polymer and charge densities, hydrophobicity, and network elasticity for the swelling of spherical polyelectrolyte (PE) gels with fixed and variable charges in a salt-free solvent. This expression of stress is used in the equation of motion of swelling kinetics of spherical PE gels to numerically calculate the spatial profiles for the polymer and free ion densities at different time steps and the time evolution of the size of the gel. We compare the profiles of the same variables obtained from the classical linear theory of elasticity and quantitatively estimate the bulk modulus of the PE gel. Further, we obtain an analytical expression of the elastic modulus from the linearized expression of stress (in the small deformation limit). We find that the estimated bulk modulus of the PE gel decreases with the increase of its effective charge for a fixed degree of deformation during swelling. Finally, we match the gel-front locations with the experimental data, taken from the measurements of charged reversible addition-fragmentation chain transfer gels to show an increase in gel-size with charge and also match the same for PNIPAM (uncharged) and imidazolium-based (charged) minigels, which specifically confirms the decrease of the gel modulus value with the increase of the charge. The agreement between experimental and theoretical results confirms general diffusive behaviour for swelling of PE gels with a decreasing bulk modulus with increasing degree of ionization (charge). The new formalism captures large deformations as well with a significant variation of charge content of the gel. It is found that PE gels with large deformation but same initial size swell faster with a higher charge.

Ion irradiation induced surface modification studies of polymers using SPM

NASA Astrophysics Data System (ADS)

Tripathi, A.; Kumar, Amit; Singh, F.; Kabiraj, D.; Avasthi, D. K.; Pivin, J. C.

2005-07-01

Various types of scanning probe microscopy (SPM) techniques: atomic force microscopy (AFM) (contact and tapping in height and amplitude mode), scanning tunnelling microscopy (STM) and conducting atomic force microscopy (C-AFM) are used for studying ion beam induced surface modifications, nanostructure/cluster formation and disintegration in polymers and similar soft carbon based materials. In the present study, the results of studies on four materials, namely, (A) methyltriethoxysilane/phenyltriethoxysilane (MTES/PTES) based gel, (B) triethoxisilane (TH) based gel, (C) highly oriented pyrolytic graphite (HOPG) bulk and (D) fullerene (C60) thin films are discussed. In the case of Si based gels prepared from pre-cursors containing organic groups (MTES/PTES), hillocks are observed at the surface and their size decreases from 70 to 25 nm with increasing fluence, whereas, in the case of a gel with a stoichiometry SiO1.25H1, prepared from TH, an increases in the size of hillocks is observed. Hillocks are also formed at the surface of HOPG irradiated with 120 MeV Au beam at a low fluence, whereas, formation of craters and a re-organisation of surface features is observed at a higher fluence. In the case of C60 films, 120 MeV Au ion irradiation induces the formation of conducting ion tracks, which is attributed to the transformation from insulating C60 to conducting graphite like carbon.

Sol-gel approach to in situ creation of high pH-resistant surface-bonded organic-inorganic hybrid zirconia coating for capillary microextraction (in-tube SPME).

PubMed

Alhooshani, Khalid; Kim, Tae-Young; Kabir, Abuzar; Malik, Abdul

2005-01-07

A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME).

Membranes in Lithium Ion Batteries

PubMed Central

Yang, Min; Hou, Junbo

2012-01-01

Lithium ion batteries have proven themselves the main choice of power sources for portable electronics. Besides consumer electronics, lithium ion batteries are also growing in popularity for military, electric vehicle, and aerospace applications. The present review attempts to summarize the knowledge about some selected membranes in lithium ion batteries. Based on the type of electrolyte used, literature concerning ceramic-glass and polymer solid ion conductors, microporous filter type separators and polymer gel based membranes is reviewed. PMID:24958286

MAGIC polymer gel for dosimetric verification in boron neutron capture therapy

PubMed Central

Heikkinen, Sami; Kotiluoto, Petri; Serén, Tom; Seppälä, Tiina; Auterinen, Iiro; Savolainen, Sauli

2007-01-01

Radiation‐sensitive polymer gels are among the most promising three‐dimensional dose verification tools developed to date. We tested the normoxic polymer gel dosimeter known by the acronym MAGIC (methacrylic and ascorbic acid in gelatin initiated by copper) to evaluate its use in boron neutron capture therapy (BNCT) dosimetry. We irradiated a large cylindrical gel phantom (diameter: 10 cm; length: 20 cm) in the epithermal neutron beam of the Finnish BNCT facility at the FiR 1 nuclear reactor. Neutron irradiation was simulated with a Monte Carlo radiation transport code MCNP. To compare dose–response, gel samples from the same production batch were also irradiated with 6 MV photons from a medical linear accelerator. Irradiated gel phantoms then underwent magnetic resonance imaging to determine their R2 relaxation rate maps. The measured and normalized dose distribution in the epithermal neutron beam was compared with the dose distribution calculated by computer simulation. The results support the feasibility of using MAGIC gel in BNCT dosimetry. PACS numbers: 87.53.Qc, 87.53.Wz, 87.66.Ff PMID:17592463

Branched Polymers for Enhancing Polymer Gel Strength and Toughness

DTIC Science & Technology

2013-02-01

Molecular Massively Parallel Simulator ( LAMMPS ) program and the stress-strain relations were calculated with varying strain-rates (figure 6). A...Acronyms ARL U.S. Army Research Laboratory D3 hexamethylcyclotrisiloxane FTIR Fourier transform infrared GPC gel permeation chromatography LAMMPS

Solvent-free, supersoft and superelastic bottlebrush melts and networks

NASA Astrophysics Data System (ADS)

Daniel, William F. M.; Burdyńska, Joanna; Vatankhah-Varnoosfaderani, Mohammad; Matyjaszewski, Krzysztof; Paturej, Jarosław; Rubinstein, Michael; Dobrynin, Andrey V.; Sheiko, Sergei S.

2016-02-01

Polymer gels are the only viable class of synthetic materials with a Young's modulus below 100 kPa conforming to biological applications, yet those gel properties require a solvent fraction. The presence of a solvent can lead to phase separation, evaporation and leakage on deformation, diminishing gel elasticity and eliciting inflammatory responses in any surrounding tissues. Here, we report solvent-free, supersoft and superelastic polymer melts and networks prepared from bottlebrush macromolecules. The brush-like architecture expands the diameter of the polymer chains, diluting their entanglements without markedly increasing stiffness. This adjustable interplay between chain diameter and stiffness makes it possible to tailor the network's elastic modulus and extensibility without the complications associated with a swollen gel. The bottlebrush melts and elastomers exhibit an unprecedented combination of low modulus (~100 Pa), high strain at break (~1,000%), and extraordinary elasticity, properties that are on par with those of designer gels.

Effect of thiolated polymers to textural and mucoadhesive properties of vaginal gel formulations prepared with polycarbophil and chitosan.

PubMed

Cevher, Erdal; Sensoy, Demet; Taha, Mohamed A M; Araman, Ahmet

2008-01-01

The aim of this study was to design and evaluate of mucoadhesive gel formulations for the vaginal application of clomiphene citrate (CLM) for local treatment of human papilloma virus (HPV) infections. Chitosan (CHI) and polycarbophil (PC) were covalently modified using the thioglycolic acid and L-cysteine, respectively. The formation of thiol conjugates of chitosan (CHI-TG) and polycarbophil (PC-CYS) were confirmed by FT-IR analysis and PC-CYS and CHI-TG were found to have 148.42 +/- 4.16 and 41.17 +/- 2.34 micromol of thiol groups per gram of polymer, respectively. One percent CLM gels were prepared by combination of various concentrations of PC and CHI with thiolated conjugates of these polymers. Hardness, compressibility, elasticity, adhesiveness and cohesiveness of the gels were measured by Texture profile analysis and the vaginal mucoadhesion was investigated by mucoadhesion test. The increasing in the amount of the thiol conjugates was found to enhance the elasticity, cohesiveness, adhesiveness and mucoadhesion of the gel formulations but not their hardness and compressibility when compared to gels prepared using their respective parent formulations. Slower release rate of CLM from gels was achieved when the polymer concentrations were increased in the gel formulations. PC and its thiol conjugate were found to prolong the release of CLM longer than 70 h unlike gel formulations prepared using CHI and its thiol conjugate which were able to release CLM up to 12 h. Stability of CLM was preserved during the 3 month stability analysis under controlled room temperature and accelerated conditions.

Physicochemical characterization of diclofenac sodium-loaded poloxamer gel as a rectal delivery system with fast absorption.

PubMed

Yong, Chul Soon; Sah, Hongkee; Jahng, Yurngdong; Chang, Hyeun Wook; Son, Jong-Keun; Lee, Seung Ho; Jeong, Tae Cheon; Rhee, Jong-Dal; Baek, Suk Hwan; Kim, Chong-Kook; Choi, Han-Gon

2003-05-01

Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium.

pH-sensitive methacrylic copolymer gels and the production thereof

DOEpatents

Mallapragada, Surya K [Ames, IA; Anderson, Brian C [Lake Bluff, IA

2007-05-15

The present invention provides novel gel forming methacrylic blocking copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol)methyl ether polymer. The polymers may be used for drug and gene delivery, protein separation, as structural supplements, and more.

Feasibility of CBCT dosimetry for IMRT using a normoxic polymethacrylic-acid gel dosimeter

NASA Astrophysics Data System (ADS)

Bong, Ji Hye; Kwon, Soo-Il; Kim, Kum Bae; Kim, Mi Suk; Jung, Hai Jo; Ji, Young Hoon; Ko, In Ok; Park, Ji Ae; Kim, Kyeong Min

2013-09-01

The purpose of this study is to evaluate the availability of cone-beam computed tomography(CBCT) for gel dosimetry. The absorbed dose was analyzed by using intensity-modulated radiation therapy(IMRT) to irradiate several tumor shapes with a calculated dose and several tumor acquiring images with CBCT in order to verify the possibility of reading a dose on the polymer gel dosimeter by means of the CBCT image. The results were compared with those obtained using magnetic resonance imaging(MRI) and CT. The linear correlation coefficients at doses less than 10 Gy for the polymer gel dosimeter were 0.967, 0.933 and 0.985 for MRI, CT and CBCT, respectively. The dose profile was symmetric on the basis of the vertical axis in a circular shape, and the uniformity was 2.50% for the MRI and 8.73% for both the CT and the CBCT. In addition, the gradient in the MR image of the gel dosimeter irradiated in an H shape was 109.88 while the gradients of the CT and the CBCT were 71.95 and 14.62, respectively. Based on better image quality, the present study showed that CBCT dosimetry for IMRT could be restrictively performed using a normoxic polymethacrylic-acid gel dosimeter.

Solvent-resistant sol-gel polydimethyldiphenylsiloxane coating for on-line hyphenation of capillary microextraction with high-performance liquid chromatography.

PubMed

Segro, Scott S; Malik, Abdul

2008-09-26

A sol-gel polydimethyldiphenylsiloxane (PDMDPS) coating was developed for capillary microextraction on-line hyphenated with high-performance liquid chromatography (HPLC). This coating was created using methyltrimethoxysilane (MTMS) as the sol-gel precursor and di-hydroxy-terminated PDMDPS as the sol-gel active polymer. The methyl and phenyl groups on the sol-gel active polymer and the methyl groups on the sol-gel precursor ultimately turned into pendant groups providing the ability to extract non-polar analytes. A 40-cm segment of 0.25 mm I.D. fused silica capillary containing the sol-gel PDMDPS coating was installed as an external sampling loop in an HPLC injection port. Aqueous samples containing polycyclic aromatic hydrocarbons (PAHs), aromatic compounds, ketones, and aldehydes were passed through this capillary wherein the analytes were extracted by the sol-gel coating. The extracted analytes were then transferred to the HPLC column using isocratic or gradient elution with an acetonitrile/water mobile phase. This capillary demonstrated excellent extraction capability for non-polar (e.g., polycyclic aromatic hydrocarbons and aromatic compounds) as well as moderately polar compounds, such as aromatic amines, ketones, and aldehydes. The test results indicate that PDMDPS can be successfully immobilized into a sol-gel network and that the resulting solvent-resistant sol-gel organic-inorganic hybrid coating can be effectively used for on-line hyphenation of capillary microextraction with high-performance liquid chromatography. The test results also indicate that the sol-gel PDMDPS coated capillary is resistant to high-temperature solvents, making it suitable for applications in high-temperature HPLC. To the best of our knowledge, this is the first report on the creation of a silica-based sol-gel PDMDPS coating used in capillary microextraction on-line hyphenated to HPLC.

Delivery of fullerene-containing complexes via microgel swelling and shear-induced release.

PubMed

Tarabukina, Elena; Zoolshoev, Zoolsho; Melenevskaya, Elena; Budtova, Tatiana

2010-01-15

The absorption and release of poly(vinylpyrrolidone)-fullerene C60 complexes (PVP/C60) from a model microgel is studied. A dry microgel based on a chemically cross-linked sodium polyacrylate was swollen in the aqueous solutions of complexes which were afterwards released under shear stress. First, gel swelling degree in static conditions in the excess of PVP/C60 solutions was studied: the degree of swelling decreases with the increase in PVP/C60 concentration. While pure PVP is homogeneously distributed between the gel and the surrounding solution, a slight concentration of complexes outside the gel was recorded. It was attributed to PVP/C60 hydrophobicity leading to the decrease in the thermodynamic quality of fullerene-containing solution being gel solvent. The release of PVP/C60 solutions induced by shear was studied with counter-rotating rheo-optical technique and compared with PVP solution release under the same conditions. The amount of solution released depends on polymer concentration and shear strain. Contrary to pure PVP solutions in which rate of release decreases with the increase in polymer concentration, PVP/C60 complexes are released faster when fullerene concentration inside the gel is higher.

High aspect ratio template and method for producing same

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Weiss, James R. (Inventor); Fleurial, Jean-Pierre (Inventor); Kisor, Adam (Inventor); Tuszynski, Mark (Inventor); Stokols, Shula (Inventor); Holt, Todd Edward (Inventor); Welker, David James (Inventor); Breckon, Christopher David (Inventor)

2010-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers.

MAGAT gel and EBT2 film‐based dosimetry for evaluating source plugging‐based treatment plan in Gamma Knife stereotactic radiosurgery

PubMed Central

Vivekanandhan, S.; Kale, S.S.; Rath, G.K.; Senthilkumaran, S.; Thulkar, S.; Subramani, V.; Laviraj, M.A.; Bisht, R.K.; Mahapatra, A.K.

2012-01-01

This work illustrates a procedure to assess the overall accuracy associated with Gamma Knife treatment planning using plugging. The main role of source plugging or blocking is to create dose falloff in the junction between a target and a critical structure. We report the use of MAGAT gel dosimeter for verification of an experimental treatment plan based on plugging. The polymer gel contained in a head‐sized glass container simulated all major aspects of the treatment process of Gamma Knife radiosurgery. The 3D dose distribution recorded in the gel dosimeter was read using a 1.5T MRI scanner. Scanning protocol was: CPMG pulse sequence with 8 equidistant echoes, TR=7 s, echo step=14 ms, pixel size=0.5 mm x 0.5 mm, and slice thickness of 2 mm. Using a calibration relationship between absorbed dose and spin‐spin relaxation rate (R2), we converted R2 images to dose images. Volumetric dose comparison between treatment planning system (TPS) and gel measurement was accomplished using an in‐house MATLAB‐based program. The isodose overlay of the measured and computed dose distribution on axial planes was in close agreement. Gamma index analysis of 3D data showed more than 94% voxel pass rate for different tolerance criteria of 3%/2 mm, 3%/1 mm and 2%/2 mm. Film dosimetry with GAFCHROMIC EBT 2 film was also performed to compare the results with the calculated TPS dose. Gamma index analysis of film measurement for the same tolerance criteria used for gel measurement evaluation showed more than 95% voxel pass rate. Verification of gamma plan calculated dose on account of shield is not part of acceptance testing of Leksell Gamma Knife (LGK). Through this study we accomplished a volumetric comparison of dose distributions measured with a polymer gel dosimeter and Leksell GammaPlan (LGP) calculations for plans using plugging. We propose gel dosimeter as a quality assurance (QA) tool for verification of plug‐based planning. PACS number: 87.53.Ly, 87.55.‐x, 87.56.N‐ PMID:23149780

Fabrication and Characterization of Dense Zirconia and Zirconia-Silica Ceramic Nanofibers

PubMed Central

Guo, Guangqing; Fan, Yuwei

2011-01-01

The objective of this study was to prepare dense zirconia-yttria (ZY), zirconia-silica (ZS) and zirconia-yttria-silica (ZYS) nanofibers as reinforcing elements for dental composites. Zirconium (IV) propoxide, yttrium nitrate hexahydrate, and tetraethyl orthosilicate (TEOS) were used as precursors for the preparation of zirconia, yttria, and silica sols. A small amount (1–1.5 wt%) of polyethylene oxide (PEO) was used as a carry polymer. The sols were preheated at 70 °C before electrospinning and their viscosity was measured with a viscometer at different heating time. The gel point was determined by viscosity–time (η–t) curve. The ZY, ZS and ZYS gel nanofibers were prepared using a special reactive electrospinning device under the conditions near the gel point. The as-prepared gel nanofibers had diameters between 200 and 400 nm. Dense (nonporous) ceramic nanofibers of zirconia-yttria (96/4), zirconia-silica (80/20) and zirconia-yttria-silica (76.8/3.2/20) with diameter of 100–300 nm were obtained by subsequent calcinations at different temperatures. The gel and ceramic nanofibers obtained were characterized by scanning electron microscope (SEM), high-resolution field-emission scanning electron microscope (FE-SEM), thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), Fourier transform infrared spectrometer (FT-IR), and X-ray diffraction (XRD). SEM micrograph revealed that ceramic ZY nanofibers had grained structure, while ceramic ZS and ZYS nanofibers had smooth surfaces, both showing no visible porosity under FE-SEM. Complete removal of the polymer PEO was confirmed by TGA/DSC and FT-IR. The formation of tetragonal phase of zirconia and amorphous silica was proved by XRD. In conclusion, dense zirconia-based ceramic nanofibers can be fabricated using the new reactive sol–gel electrospinning technology with minimum organic polymer additives. PMID:21133090

Amphiphilic polymers formed from ring-opening polymerization: a strategy for the enhancement of gene delivery.

PubMed

Zhang, Yi-Mei; Huang, Zheng; Zhang, Ji; Wu, Wan-Xia; Liu, Yan-Hong; Yu, Xiao-Qi

2017-03-28

Cationic liposomes and polymers are both important candidates for use as non-viral gene vectors. However, both of them have special shortcomings and application limits. This work is devoted to the combination of advantages of liposomes and polymers. The ring-opening polymerization strategy was used for the preparation of amphiphilic polymers from cyclen-based cationic small lipids. The non-hydrophobic polymer and the corresponding lipids were also prepared for performing structure-activity relationship studies. Gel electrophoresis results reveal that both the lipopolymers and liposomes could effectively condense DNA into nanoparticles and protect DNA from degradation. Compared to polymers, the DNA binding ability of liposomes is more affected by hydrophobic tails. Under the same dosage, the synthetic polymers have stronger DNA binding ability than the liposomes. In vitro transfection experiments show that the polymers could give better transfection efficiency, which was much higher than those of the corresponding liposomes and non-hydrophobic polymer. The oleyl moiety is suitable for lipidic vectors, but things were different for polymers. Under optimized conditions, up to 14.2 times higher transfection efficiency than that for 25 kDa bPEI could be obtained. More importantly, the lipopolymers showed much better serum tolerance, which was further confirmed by protein adsorption, gel electrophoresis, flow cytometry, and CLSM assays. The results indicate that ring-opening polymerization is a promising strategy for the enhancement of the gene delivery efficiency and biocompatibility of cationic lipids.

Bio-inspired network optimization in soft materials — Insights from the plant cell wall

NASA Astrophysics Data System (ADS)

Vincent, R. R.; Cucheval, A.; Hemar, Y.; Williams, M. A. K.

2009-01-01

The dynamic-mechanical responses of ionotropic gels made from the biopolymer pectin have recently been investigated by microrheological experiments and found to exhibit behaviour indicative of semi-flexible polymer networks. In this work we investigate the gelling behaviour of pectin systems in which an enzyme (pectinmethylesterase, PME) is used to liberate ion-binding sites on initially inert polymers, while in the presence of ions. This is in contrast to the previous work, where it was the release of ions (rather than ion-binding groups) that was controlled and the polymers had pre-existing cross-linkable moieties. In stark contrast to the semi-flexible network paradigm of biological gels and the previous work on pectin, the gels studied herein exhibit the properties of chemically cross-linked networks of flexible polymers.

Amperometric L-lysine enzyme electrodes based on carbon nanotube/redox polymer and graphene/carbon nanotube/redox polymer composites.

PubMed

Kaçar, Ceren; Erden, Pınar Esra; Kılıç, Esma

2017-04-01

Highly sensitive L-lysine enzyme electrodes were constructed by using poly(vinylferrocene)-multiwalled carbon nanotubes-gelatine (PVF/MWCNTs-GEL) and poly(vinylferrocene)-multiwalled carbon nanotubes-gelatine-graphene (PVF/MWCNTs-GEL/GR) composites as sensing interfaces and their performances were evaluated. Lysine oxidase (LO) was immobilized onto the composite modified glassy carbon electrodes (GCE) by crosslinking using glutaraldehyde and bovine serum albumin. Effects of pH value, enzyme loading, applied potential, electrode composition, and interfering substances on the amperometric response of the enzyme electrodes were discussed. The analytical characteristics of the enzyme electrodes were also investigated. The linear range, detection limit, and sensitivity of the LO/PVF/MWCNTs-GEL/GCE were 9.9 × 10 -7 -7.0 × 10 -4  M, 1.8 × 10 -7  M (S/N = 3), and 13.51 μA mM -1  cm -2 , respectively. PVF/MWCNTs-GEL/GR-based L-lysine enzyme electrode showed a short response time (<5 s) and a linear detection range from 9.9 × 10 -7 to 7.0 × 10 -4  M with good sensitivity of 17.8 μA mM -1  cm -2 and a low detection limit of 9.2 × 10 -8  M. The PVF/MWCNTs-GEL/GR composite-based L-lysine enzyme electrode exhibited about 1.3-fold higher sensitivity than its MWCNTs-based counterpart and its detection limit was superior to the MWCNTs-based one. In addition, enzyme electrodes were successfully applied to determine L-lysine in pharmaceutical sample and cheese.

Preparation and electrochemical characterization of polymer electrolytes based on electrospun poly(vinylidene fluoride- co-hexafluoropropylene)/polyacrylonitrile blend/composite membranes for lithium batteries

NASA Astrophysics Data System (ADS)

Raghavan, Prasanth; Zhao, Xiaohui; Shin, Chorong; Baek, Dong-Ho; Choi, Jae-Won; Manuel, James; Heo, Min-Yeong; Ahn, Jou-Hyeon; Nah, Changwoon

Apart from PEO based solid polymer electrolytes, tailor-made gel polymer electrolytes based on blend/composite membranes of poly(vinylidene fluoride- co-hexafluoropropylene) and polyacrylonitrile are prepared by electrospinning using 14 wt% polymer solution in dimethylformamide. The membranes show uniform morphology with an average fiber diameter of 320-490 nm, high porosity and electrolyte uptake. Polymer electrolytes are prepared by soaking the electrospun membranes in 1 M lithium hexafluorophosphate in ethylene carbonate/dimethyl carbonate. Temperature dependent ionic conductivity and their electrochemical performance are studied. The blend/composite polymer electrolytes show good ionic conductivity in the range of 10 -3 S cm -1 at ambient temperature and good electrochemical performance. All the Polymer electrolytes show an anodic stability >4.6 V with stable interfacial resistance with storage time. The prototype cell shows good charge-discharge properties and stable cycle performance with comparable capacity fade compared to liquid electrolyte under the test conditions.

Optical fiber sensor having a sol-gel fiber core and a method of making

DOEpatents

Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

2006-06-06

A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.

Electroactive Ionic Soft Actuators with Monolithically Integrated Gold Nanocomposite Electrodes.

PubMed

Yan, Yunsong; Santaniello, Tommaso; Bettini, Luca Giacomo; Minnai, Chloé; Bellacicca, Andrea; Porotti, Riccardo; Denti, Ilaria; Faraone, Gabriele; Merlini, Marco; Lenardi, Cristina; Milani, Paolo

2017-06-01

Electroactive ionic gel/metal nanocomposites are produced by implanting supersonically accelerated neutral gold nanoparticles into a novel chemically crosslinked ion conductive soft polymer. The ionic gel consists of chemically crosslinked poly(acrylic acid) and polyacrylonitrile networks, blended with halloysite nanoclays and imidazolium-based ionic liquid. The material exhibits mechanical properties similar to that of elastomers (Young's modulus ≈ 0.35 MPa) together with high ionic conductivity. The fabrication of thin (≈100 nm thick) nanostructured compliant electrodes by means of supersonic cluster beam implantation (SCBI) does not significantly alter the mechanical properties of the soft polymer and provides controlled electrical properties and large surface area for ions storage. SCBI is cost effective and suitable for the scaleup manufacturing of electroactive soft actuators. This study reports the high-strain electromechanical actuation performance of the novel ionic gel/metal nanocomposites in a low-voltage regime (from 0.1 to 5 V), with long-term stability up to 76 000 cycles with no electrode delamination or deterioration. The observed behavior is due to both the intrinsic features of the ionic gel (elasticity and ionic transport capability) and the electrical and morphological features of the electrodes, providing low specific resistance (<100 Ω cm -2 ), high electrochemical capacitance (≈mF g -1 ), and minimal mechanical stress at the polymer/metal composite interface upon deformation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gelling ability of kefiran in the presence of sucrose and fructose and physicochemical characterization of the resulting cryogels.

PubMed

Zavala, Lucía; Roberti, Paula; Piermaria, Judith A; Abraham, Analía G

2015-08-01

In this work, the influence of sucrose and fructose on the gel-forming capacity of kefiran was investigated as well as the physicochemical characteristics of the resulting gels. The addition of sugar to gel-forming solutions did not alter the pseudoplastic flow properties of kefiran solutions and after one freeze-thaw cycle translucent gels with high water-holding capability were obtained. A highly porous matrix was revealed by microscopy whose pore size varied with sugar concentration. Sucrose and fructose had different effects on the rheological characteristics of sugar-kefiran gels. An increment in the strength of the gels with progressive concentrations of sucrose was evidenced by an increase in the elastic modulus (G'), indicating that sucrose reinforces the binding interactions between the polymer molecules (p ≤ 0.05). A drastic reduction in elastic modulus occurred, however, when 50.0 % w/w sucrose was added to kefiran gels, resulting in less elasticity. In contrast, when fructose was added to kefiran gels, elastic modulus decreased slightly with progressive sugar concentrations up to 10 %, thereafter increasing up to 50 % (p ≤ 0.05). Supplementation with up to 30 % sugar contributed to water retention and increased the viscous modulus. The relative increment in the elastic and viscous moduli elevated the loss tangent (tanδ) depending on the type and concentration of sugar. Sugars (sucrose, fructose) present in the matrix of the polysaccharide networks modified water-polymer and polymer-polymer interactions and consequently changed the gels' physicochemical characteristics, thus allowing the possibility of selecting the appropriate formulation through tailor-made kefiran cryogels.

Hierarchical Sol-Gel Transition Induced by Thermosensitive Self-Assembly of an ABC Triblock Polymer in an Ionic Liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitazawa, Yuzo; Ueki, Takeshi; McIntosh, Lucas D.

2016-04-29

Here we investigate a hierarchical morphology change and accompanying sol–gel transition using a doubly thermosensitive ABC-triblock copolymer in an ionic liquid (IL). The triblock copolymer contains two different lower critical solution temperature (LCST) thermosensitive polymers, poly(benzyl methacrylate) (PBnMA) and poly(2-phenylethyl methacrylate) (PPhEtMA), as the end blocks and poly(methyl methacrylate) (PMMA) as the middle block (PBnMA-b-PMMA-b-PPhEtMA: BMP). BMP undergoes a hierarchical phase transition corresponding to the self-assembly of each of the thermosensitive blocks in the IL, and a sol–gel transition was observed in concentrated, above 10 wt %, polymer solutions. The gelation behavior was affected by polymer concentration, and at 20more » wt %, the BMP/IL composite showed a phase transition, with increasing temperature, from solution through a jammed micelle suspension to a physically cross-linked gel. For each phase was formed reversibly and rapidly over the corresponding temperature range. Finally, the jammed micelle and cross-linked gel states were characterized using viscoelastic measurements and small-angle X-ray scattering (SAXS).« less

Selective digestion of Ba2+/Ca2+ alginate gel microdroplets for single-cell handling

NASA Astrophysics Data System (ADS)

Odaka, Masao; Hattori, Akihiro; Matsuura, Kenji; Yasuda, Kenji

2018-06-01

Cells encapsuled by polymer microdroplets are an effective platform for the identification and separation of individual cells for single-cell-based analysis. However, a key challenge is to maintain and release the captured cells in the microdroplets selectively, nondestructively, and noninvasively. We developed a simple method of encapsulating cells in alginate microdroplets having different digestion characteristics. Cells were diluted with an alginate polymer of sol state and encapsulated into microdroplets with Ba2+ and Ca2+ by a spray method. When a chelating buffer was applied, alginate gel microdroplets were digested according to the difference in chelating efficiency of linkage-divalent cations; hence, two types of alginate microdroplets were formed. Moreover, we examined the capability of the alginate gel to exchange linkage-divalent cations and found that both Ca2+ exchange in Ba-alginate microdroplets and Ba2+ exchange in Ca-alginate microdroplets occurred. These results indicate that the potential applications of a mixture of alginate microdroplets with different divalent cations control the selective digestion of microdroplets to improve the high-throughput, high-content microdroplet-based separation, analysis, or storage of single cells.

Enhanced mixing in polyacrylamide gels containing embedded silica nanoparticles as internal electroosmotic pumps.

PubMed

Matos, Marvi A; White, Lee R; Tilton, Robert D

2008-02-15

Many biosensors, including those based on sensing agents immobilized inside hydrogels, suffer from slow response dynamics due to mass transfer limitations. Here we present an internal pumping strategy to promote convective mixing inside crosslinked polymer gels. This is envisioned as a potential tool to enhance biosensor response dynamics. The method is based on electroosmotic flows driven by non-uniform, oscillating electric fields applied across a polyacrylamide gel that has been doped with charged colloidal silica inclusions. Evidence for enhanced mixing was obtained from florescence recovery after photobleaching (FRAP) measurements with fluorescein tracer dyes dissolved in the gel. Mixing rates in silica-laden gels under the action of the applied electric fields were more than an order of magnitude faster than either diffusion or electrophoretically driven mixing in gels that did not contain silica. The mixing enhancement was due in comparable parts to the electroosmotic pumping and to the increase in gel swelling caused by the presence of the silica inclusions. The latter had the effect of increasing tracer mobility in the silica-laden gels.

Polymer/Carbon-Based Hybrid Aerogels: Preparation, Properties and Applications

PubMed Central

Zuo, Lizeng; Zhang, Youfang; Zhang, Longsheng; Miao, Yue-E; Fan, Wei; Liu, Tianxi

2015-01-01

Aerogels are synthetic porous materials derived from sol-gel materials in which the liquid component has been replaced with gas to leave intact solid nanostructures without pore collapse. Recently, aerogels based on natural or synthetic polymers, called polymer or organic aerogels, have been widely explored due to their porous structures and unique properties, such as high specific surface area, low density, low thermal conductivity and dielectric constant. This paper gives a comprehensive review about the most recent progresses in preparation, structures and properties of polymer and their derived carbon-based aerogels, as well as their potential applications in various fields including energy storage, adsorption, thermal insulation and flame retardancy. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this review. PMID:28793602

Structured copolymers and their use as absorbents, gels and carriers of metal ions

DOEpatents

Hedstrand, David M.; Helmer, Bradley J.; Tomalia, Donald A.

1996-01-01

Dense star polymers or dendrimers having a highly branched interior structure capable of associating or chelating with metal ions are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell. The modified dendrimers are useful for dispersing metal ions in a non-aqueous polymer matrix. Also dense star polymers or dendrimers having a highly branched hydrophilic interior structure are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell, which modified polymers are useful as gels and surfactants.

Structured copolymers and their use as absorbents, gels and carriers of metal ions

DOEpatents

Hedstrand, D.M.; Helmer, B.J.; Tomalia, D.A.

1996-10-01

Dense star polymers or dendrimers having a highly branched interior structure capable of associating or chelating with metal ions are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell. The modified dendrimers are useful for dispersing metal ions in a non-aqueous polymer matrix. Also dense star polymers or dendrimers having a highly branched hydrophilic interior structure are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell, which modified polymers are useful as gels and surfactants.

Investigation of the PAGAT polymer gel dosimeter using magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Venning, A. J.; Hill, B.; Brindha, S.; Healy, B. J.; Baldock, C.

2005-08-01

Investigation of the normoxic PAGAT polymer gel dosimeter has been undertaken. The concentrations of the chemical components of the gel were varied and its response to ionizing radiation evaluated. Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2 was determined to be 4.5% N, N'-methylene-bis-acrylamide (bis), 4.5% acrylamide (AA), 5% gelatine, 5 mM tetrakis (hydroxymethyl) phosphonium chloride (THPC), 0.01 mM hydroquinone (HQ) and 86% H2O. The optimal post-manufacture irradiation and post-irradiation imaging times were both determined to be 12 h. The R2-dose response was linear up to 7 Gy with R2-dose sensitivities of (0.183 ± 0.005) s-1 Gy-1, (0.182 ± 0.005) s-1 Gy-1 and (0.192 ± 0.005) s-1 Gy-1 when imaged at 12 h, 7 days and 24 days post-irradiation, respectively. The R2-dose sensitivities were within the range of previously published values for the hypoxic PAG formulations. For the imaging parameters used in this study the optimum dose resolution was achieved for low doses. The normalized R2 edge response showed a high degree of spatial stability over a 24 day period. This study has shown that the normoxic PAGAT polymer gel has the properties of a dosimetric tool, which can be used in clinical radiotherapy. The PAGAT polymer gel has been shown to have similar qualities to the PAG polymer gel, while offering the significant advantage of simplification of the manufacturing procedure.

[In vitro evaluation of the gels properties prepared thermosensitive polymers as vehicles for administration substance by injection].

PubMed

Karolewicz, Bozena; Owczarek, Artur; Pluta, Janusz

2011-01-01

The aim of this study was to prepare a thermoresponsive formulations, which are a carrier for substance administered directly into site of action and which obtain sol-gel transitions at physiological ranges of temperature. The investigated formulations of liquid consistency at room temperature were obtained in sterile conditions on the basis of nonionic polymers Pluronic F-127, Pluronic F-68 and anionic polymer hyaluronic acid in different concentrations. The sol-gel transition temperature of the formulations was investigated and their physicochemical properties such as pH, density, osmotic pressure, sol-gel transition temperature, texture and release of vancomycin hydrochloride were studied. In vitro release experiments indicated that the optimised platform was able to prolong vancomycin hydrochloride release and their physico-chemical properties allow for application by injection form.

Normal stresses in semiflexible polymer hydrogels

NASA Astrophysics Data System (ADS)

Vahabi, M.; Vos, Bart E.; de Cagny, Henri C. G.; Bonn, Daniel; Koenderink, Gijsje H.; MacKintosh, F. C.

2018-03-01

Biopolymer gels such as fibrin and collagen networks are known to develop tensile axial stress when subject to torsion. This negative normal stress is opposite to the classical Poynting effect observed for most elastic solids including synthetic polymer gels, where torsion provokes a positive normal stress. As shown recently, this anomalous behavior in fibrin gels depends on the open, porous network structure of biopolymer gels, which facilitates interstitial fluid flow during shear and can be described by a phenomenological two-fluid model with viscous coupling between network and solvent. Here we extend this model and develop a microscopic model for the individual diagonal components of the stress tensor that determine the axial response of semiflexible polymer hydrogels. This microscopic model predicts that the magnitude of these stress components depends inversely on the characteristic strain for the onset of nonlinear shear stress, which we confirm experimentally by shear rheometry on fibrin gels. Moreover, our model predicts a transient behavior of the normal stress, which is in excellent agreement with the full time-dependent normal stress we measure.

Polymer gel dosimeters with reduced toxicity: a preliminary investigation of the NMR and optical dose response using different monomers

NASA Astrophysics Data System (ADS)

Senden, R. J.; DeJean, P.; McAuley, K. B.; Schreiner, L. J.

2006-07-01

In this work, three new polymer gel dosimeter recipes were investigated that may be more suitable for widespread applications than polyacrylamide gel dosimeters, since the extremely toxic acrylamide has been replaced with the less harmful monomers N-isopropylacrylamide (NIPAM), diacetone acrylamide and N-vinylformamide. The new gel dosimeters studied contained gelatin (5 wt%), monomer (3 wt%), N,N'-methylene-bis-acrylamide crosslinker (3 wt%) and tetrakis (hydroxymethyl) phosphonium chloride antioxidant (10 mM). The NMR response (R2) of the dosimeters was analysed for conditions of varying dose, dose rate, time post-irradiation, and temperature during irradiation and scanning. It was shown that the dose-response behaviour of the NIPAM/Bis gel dosimeter is comparable to that of normoxic polyacrylamide gel (PAGAT) in terms of high dose-sensitivity and low dependence on dose rate and irradiation temperature, within the ranges considered. The dose-response (R2) of NIPAM/Bis appears to be linear over a greater dose range than the PAGAT gel dosimeter. The effects of time post-irradiation (temporal instability) and temperature during NMR scanning on the R2 response were more significant for NIPAM/Bis dosimeters. Diacetone acrylamide and N-vinylformamide gel dosimeters possessed considerably lower dose-sensitivities. The optical dose-response, measured in terms of the attenuation coefficient for each polymer gel dosimeter, showed potential for the use of optical imaging techniques in future studies.

Oscillation of a polymer gel entrained with a periodic force.

PubMed

Shiota, Takaya; Ikura, Yumihiko S; Nakata, Satoshi

2013-02-21

The oscillation of a polymer gel induced by the Belousov-Zhabotinsky (BZ) reaction was investigated under an external force composed of a square wave. The oscillation of the BZ reaction entrained to the periodic force and the features of this entrainment changed depending on the period and duty cycle of the square wave. The experimental results suggest that the change in the volume of the gel also gave feedback to the BZ reaction. The mechanism of entrainment is discussed in relation to the compression of the gel and the reaction-diffusion system in the BZ reaction.

Introduction of a deformable x-ray CT polymer gel dosimetry system

NASA Astrophysics Data System (ADS)

Maynard, E.; Heath, E.; Hilts, M.; Jirasek, A.

2018-04-01

This study introduces the first 3D deformable dosimetry system based on x-ray computed tomography (CT) polymer gel dosimetry and establishes the setup reproducibility, deformation characteristics and dose response of the system. A N-isopropylacrylamide (NIPAM)-based gel formulation optimized for x-ray CT gel dosimetry was used, with a latex balloon serving as the deformable container and low-density polyethylene and polyvinyl alcohol providing additional oxygen barrier. Deformable gels were irradiated with a 6 MV calibration pattern to determine dosimetric response and a dosimetrically uniform plan to determine the spatial uniformity of the response. Wax beads were added to each gel as fiducial markers to track the deformation and setup of the gel dosimeters. From positions of the beads on CT images the setup reproducibility and the limits and reproducibility of gel deformation were determined. Comparison of gel measurements with Monte Carlo dose calculations found excellent dosimetric accuracy, comparable to that of an established non-deformable dosimetry system, with a mean dose discrepancy of 1.5% in the low-dose gradient region and a gamma pass rate of 97.9% using a 3%/3 mm criterion. The deformable dosimeter also showed good overall spatial dose uniformity throughout the dosimeter with some discrepancies within 20 mm of the edge of the container. Tracking of the beads within the dosimeter found that sub-millimetre setup accuracy is achievable with this system. The dosimeter was able to deform and relax when externally compressed by up to 30 mm without sustaining any permanent damage. Internal deformations in 3D produced average marker movements of up to 12 mm along the direction of compression. These deformations were also shown to be reproducible over 100 consecutive deformations. This work has established several important characteristics of a new deformable dosimetry system which shows promise for future clinical applications, including the validation of deformable dose accumulation algorithms.

Improvement of N-phthaloylchitosan based gel polymer electrolyte in dye-sensitized solar cells using a binary salt system.

PubMed

Yusuf, S N F; Azzahari, A D; Selvanathan, V; Yahya, R; Careem, M A; Arof, A K

2017-02-10

A binary salt system utilizing lithium iodide (LiI) as the auxiliary component has been introduced to the N-phthaloylchitosan (PhCh) based gel polymer electrolyte consisting of ethylene carbonate (EC), dimethylformamide (DMF), tetrapropylammonium iodide (TPAI), and iodine (I 2 ) in order to improve the performance of dye-sensitized solar cell (DSSC) with efficiency of 6.36%, photocurrent density, J SC of 17.29mAcm -2 , open circuit voltage, V OC of 0.59V and fill factor, FF of 0.62. This efficiency value is an improvement from the 5.00% performance obtained by the DSSC consisting of only TPAI single salt system. The presence of the LiI in addition to the TPAI improves the charge injection rates and increases the iodide contribution to the total conductivity and both factors contribute to the increase in efficiency of the DSSC. The interaction behavior between polymer-plasticizer-salt was thoroughly investigated using EIS, FTIR spectroscopy and XRD. Copyright © 2016 Elsevier Ltd. All rights reserved.

A novel gel based on an ionic complex from a dendronized polymer and ciprofloxacin: Evaluation of its use for controlled topical drug release.

PubMed

García, Mónica C; Cuggino, Julio C; Rosset, Clarisa I; Páez, Paulina L; Strumia, Miriam C; Manzo, Ruben H; Alovero, Fabiana L; Alvarez Igarzabal, Cecilia I; Jimenez-Kairuz, Alvaro F

2016-12-01

The development and characterization of a novel, gel-type material based on a dendronized polymer (DP) loaded with ciprofloxacin (CIP), and the evaluation of its possible use for controlled drug release, are presented in this work. DP showed biocompatible and non-toxic behaviors in cultured cells, both of which are considered optimal properties for the design of a final material for biomedical applications. These results were encouraging for the use of the polymer loaded with CIP (as a drug model), under gel form, in the development of a new controlled-release system to be evaluated for topical administration. First, DP-CIP ionic complexes were obtained by an acid-base reaction using the high density of carboxylic acid groups of the DP and the amine groups of the CIP. The complexes obtained in the solid state were broadly characterized using FTIR spectroscopy, XRP diffraction, DSC-TG analysis and optical microscopy techniques. Gels based on the DP-CIP complexes were easily prepared and presented excellent mechanical behaviors. In addition, optimal properties for application on mucosal membranes and skin were achieved due to their high biocompatibility and acute skin non-irritation. Slow and sustained release of CIP toward simulated physiological fluids was observed in the assays (in vitro), attributed to ion exchange phenomenon and to the drug reservoir effect. An in vitro bacterial growth inhibition assay showed significant CIP activity, corresponding to 38 and 58% of that exhibited by a CIP hydrochloride solution at similar CIP concentrations, against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. However, CIP delivery was appropriate, both in terms of magnitude and velocity to allow for a bactericidal effect. In conclusion, the final product showed promising behavior, which could be exploited for the treatment of topical and mucosal opportunistic infections in human or veterinary applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Interphase Transformations at Metal (Copper, Iron)-Polymer Gel-Electrolyte Interfaces

NASA Astrophysics Data System (ADS)

Lyamina, G. V.; Dubinina, O. V.; Vaitulevich, E. A.; Mokrousov, G. M.

2018-07-01

The results from studies of the interface boundaries between metals (copper and iron) and gel electrolyte based on methacrylic copolymers are organized systematically. In contrast to processes in liquid electrolytes, a number of key features of the reactions that occur at such interfaces are revealed: a diffusion limiting stage; a lack of reverse reactions; and the formation of coordination compounds of metal ions with the functional groups of polymers, the stabilities of which are several orders of magnitude greater than that of coordination with their low-molecular weight counterparts. It is shown that processes which employ polymeric organogels can be used for the careful cleaning of the metal surfaces, and for the formation of a desired phase composition on the latter.

In situ gelling polymers in ocular drug delivery systems: a review.

PubMed

Mundada, Atish S; Avari, Jasmine G

2009-01-01

The review article aims to highlight the recent developments in various in situ gel-forming polymeric systems that are used to achieve prolonged contact time of drugs with the cornea and increase their ocular bioavailability. These phase-change polymers, which trigger the drug release in response to external stimuli, are the most investigated in controlled drug delivery. The present review summarizes in detail these various polymers, which undergo sol-gel transition due to physical (temperature) or chemical (pH, ions) stimuli when instilled in the eye. As a whole, this article provides valuable insight into current trends in the field of in situ gel-forming ocular drug delivery systems.

Synthesis and characterization of a new photo-crosslinkable glycol chitosan thermogel for biomedical applications.

PubMed

Cho, Ik Sung; Cho, Myeong Ok; Li, Zhengzheng; Nurunnabi, Md; Park, Sung Young; Kang, Sun-Woong; Huh, Kang Moo

2016-06-25

The major limitations of typical thermogelling polymers for practical applications are low gel stability and weak mechanical properties under physiological conditions. In this study, we have synthesized a new polysaccharide-based thermogelling polymer that can be photo-crosslinked by UV irradiation to form a mechanically resilient and elastic hydrogel. Methacrylated hexanoyl glycol chitosan (M-HGC), was synthesized by a series of chemical modifications, N-hexanoylation and N-methacrylation, of glycol chitosan (GC). Various M-HGC polymers with different methacryl group contents were synthesized and their thermogelling and photo-crosslinkable properties were evaluated. The M-HGCs demonstrated a thermo-reversible sol-gel transition behavior in aqueous solutions. The thermally-induced hydrogels could be chemically crosslinked by UV-triggered photo-crosslinking. From the cytotoxicity studies using MTT and the live/dead assay, the M-HGC hydrogels showed non-cytotoxicity. These photo-crosslinkable thermogelling M-HGC polymers may hold great promises for various biomedical applications, such as an injectable delivery system and 3D cell culture. Copyright © 2016 Elsevier Ltd. All rights reserved.

Large deformation of self-oscillating polymer gel

NASA Astrophysics Data System (ADS)

Maeda, Shingo; Kato, Terukazu; Otsuka, Yuji; Hosoya, Naoki; Cianchetti, Matteo; Laschi, Cecilia

2016-01-01

A self-oscillating gel is a system that generates an autonomous volume oscillation. This oscillation is powered by the chemical energy of the Belousov-Zhabotinsky (BZ) reaction, which demonstrates metal ion redox oscillation. A self-oscillating gel is composed of Poly-N -isopropylacrylamide (PNIPAAm) with a metal ion. In this study, we found that the displacement of the volume oscillation in a self-oscillating gel could be controlled by its being subjected to a prestraining process. We also revealed the driving mechanism of the self-oscillating gel from the point of view of thermodynamics. We observed that the polymer-solvent interaction parameter χ is altered by the redox changes to the metal ion incorporated in the self-oscillating gel. The prestraining process leads to changes in χ and changes in enthalpy and entropy when the self-oscillating gel is in a reduced and oxidized state. We found that nonprestrained gel samples oscillate in a poor solution (χ >0.5 ) and prestrained gel samples oscillate in a good solution (χ <0.5 ).

NMR Water Self–Diffusion and Relaxation Studies on Sodium Polyacrylate Solutions and Gels in Physiologic Ionic Solutions

PubMed Central

Bai, Ruiliang; Basser, Peter J.; Briber, Robert M.; Horkay, Ferenc

2013-01-01

Water self-diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca2+ and Na+. Several physical models describing the self-diffusion of the solvent were applied and compared. A free-volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non-linear behavior at higher concentrations. Both the water self-diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na+ on the mobility of water molecules was practically undetectable. By contrast, addition of Ca2+ strongly increased the longitudinal relaxation rate while its effect on the self-diffusion coefficient was much less pronounced. PMID:24409001

NMR Water Self-Diffusion and Relaxation Studies on Sodium Polyacrylate Solutions and Gels in Physiologic Ionic Solutions.

PubMed

Bai, Ruiliang; Basser, Peter J; Briber, Robert M; Horkay, Ferenc

2014-03-15

Water self-diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca 2+ and Na + . Several physical models describing the self-diffusion of the solvent were applied and compared. A free-volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non-linear behavior at higher concentrations. Both the water self-diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na + on the mobility of water molecules was practically undetectable. By contrast, addition of Ca 2+ strongly increased the longitudinal relaxation rate while its effect on the self-diffusion coefficient was much less pronounced.

Preparation, characterization and adsorption study of o-cresol molecularly imprinted grafted silica gel sorbent synthesized by sol-gel polymerization

NASA Astrophysics Data System (ADS)

Zinalibdin, Mohamad Raizul; Jaafar, Jafariah; Majid, Zaiton Abdul; Sanagi, Mohd Marsin

2017-11-01

In this study, a new composite core-shell of o-cresol molecularly imprinted polymer grafted silica gel (MIP@SiO2) was prepared via sol-gel polymerization. It was synthesized using o-cresol as the template molecule, 3-propyl(metacrylate)trimethoxysilane (3-PMTMOS) as the functional monomer, tetraethoxysilane (TEOS) as the cross-linker and ethanol as the porogenic solvent in the surface of silica gel. The non-imprinted polymer-grafted silica gel (NIP@SiO2) was prepared with the same technique but without template molecule. This analyte was selected as a template due to the fact that it is one of toluene metabolites. The characterization of MIP@SiO2 and NIP@SiO2 were observed by N2 adsorption analysis and Field emission scanning electron microscopy-energy dispersive x-ray (FESEM-EDX). The MIP@SiO2 and NIP@SiO2 were employed as an adsorbent for the extraction of o-cresol, a metabolite in urine sample for the monitoring of occupational toluene exposure in workers. Based on the results of the adsorption study, the MIP prepared using 0.5 mmol 3-(propylmethacrylate)trimethoxysilane), 10 mL of ethanol, 4 mmol TEOS,0.05 mmol o-cresol, 0.1g silica gel and 1mL of 0.01 mol/L acetic acid was found the adsorption capacity (0.9920 mg g-1) and imprint factor (5.21).

Manganese oxide electrochemical capacitor with potassium poly(acrylate) hydrogel electrolyte

NASA Astrophysics Data System (ADS)

Lee, Kuang-Tsin; Wu, Nae-Lih

An aqueous gel electrolyte has for the first time been successfully applied to the MnO 2· nH 2O-based pseudocapacitive electrochemical capacitors (ECs). The gel electrolyte is made of potassium poly(acrylate) (PAAK) polymer and aqueous solution of KCl. With the selected composition, PAAK:KCl:H 2O = 9.0%:6.7%:84.3% by weight, the gel shows no fluidity, possessing an ionic conductivity in the order of 10 -1 S cm -1. The gel electrolyte has been found to give substantially higher specific capacitances than those in the liquid electrolyte with the same salt (KCl) composition (1 M) and high power capability (>10 kW/kg).

Multiscale Computer Simulation of Tensile and Compressive Strain in Polymer- Coated Silica Aerogels

NASA Technical Reports Server (NTRS)

Good, Brian

2009-01-01

While the low thermal conductivities of silica aerogels have made them of interest to the aerospace community as lightweight thermal insulation, the application of conformal polymer coatings to these gels increases their strength significantly, making them potentially useful as structural materials as well. In this work we perform multiscale computer simulations to investigate the tensile and compressive strain behavior of silica and polymer-coated silica aerogels. Aerogels are made up of clusters of interconnected particles of amorphous silica of less than bulk density. We simulate gel nanostructure using a Diffusion Limited Cluster Aggregation (DLCA) procedure, which produces aggregates that exhibit fractal dimensions similar to those observed in real aerogels. We have previously found that model gels obtained via DLCA exhibited stress-strain curves characteristic of the experimentally observed brittle failure. However, the strain energetics near the expected point of failure were not consistent with such failure. This shortcoming may be due to the fact that the DLCA process produces model gels that are lacking in closed-loop substructures, compared with real gels. Our model gels therefore contain an excess of dangling strands, which tend to unravel under tensile strain, producing non-brittle failure. To address this problem, we have incorporated a modification to the DLCA algorithm that specifically produces closed loops in the model gels. We obtain the strain energetics of interparticle connections via atomistic molecular statics, and abstract the collective energy of the atomic bonds into a Morse potential scaled to describe gel particle interactions. Polymer coatings are similarly described. We apply repeated small uniaxial strains to DLCA clusters, and allow relaxation of the center eighty percent of the cluster between strains. The simulations produce energetics and stress-strain curves for looped and nonlooped clusters, for a variety of densities and interaction parameters.

The dose distribution of low dose rate Cs-137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement

NASA Astrophysics Data System (ADS)

Fragoso, M.; Love, P. A.; Verhaegen, F.; Nalder, C.; Bidmead, A. M.; Leach, M.; Webb, S.

2004-12-01

In this study, the dose distribution delivered by low dose rate Cs-137 brachytherapy sources was investigated using Monte Carlo (MC) techniques and polymer gel dosimetry. The results obtained were compared with a commercial treatment planning system (TPS). The 20 mm and the 30 mm diameter Selectron vaginal applicator set (Nucletron) were used for this study. A homogeneous and a heterogeneous—with an air cavity—polymer gel phantom was used to measure the dose distribution from these sources. The same geometrical set-up was used for the MC calculations. Beyond the applicator tip, differences in dose as large as 20% were found between the MC and TPS. This is attributed to the presence of stainless steel in the applicator and source set, which are not considered by the TPS calculations. Beyond the air cavity, differences in dose of around 5% were noted, due to the TPS assuming a homogeneous water medium. The polymer gel results were in good agreement with the MC calculations for all the cases investigated.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, LeRoy Louis; Nichols, Monte Carl; Wheeler, David Roger; Loy, Douglas Anson

1997-01-01

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolized in an inert atmosphere to form a SiC foam.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

1997-09-16

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolyzed in an inert atmosphere to form a SiC foam. 9 figs.

The effect of polymer composition on the gelation behavior of PLGA-g-PEG biodegradable thermoreversible gels.

PubMed

Tarasevich, B J; Gutowska, A; Li, X S; Jeong, B-M

2009-04-01

Graft copolymers consisting of a poly(D,L-lactic acid-co-glycolic acid) backbone grafted with polyethylene glycol side chains were synthesized and formed thermoreversible gels in aqueous solutions that exhibited solution behavior at low temperature and sol-to-gel transitions at higher temperature. The composition of the polymer and relative amounts of polylactic acid, glycolic acid, and ethylene glycol were varied by controlling the precursor concentrations and reaction temperature. The gelation temperature could be systematically tailored from 15 to 34 degrees C by increasing the concentration of polyethylene glycol in the graft copolymer. The gelation temperature also depended on the polymer molecular weight and concentration. This work has importance for the development of water soluble gels with tailored compositions and gelation temperatures for use in tissue engineering and as injectable depots for drug delivery. Copyright 2008 Wiley Periodicals, Inc.

Controlled Sol-Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger.

PubMed

Wang, Caihong; Hashimoto, Kei; Tamate, Ryota; Kokubo, Hisashi; Watanabe, Masayoshi

2018-01-02

Producing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light-controlled mechanical sol-gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light-controlled sol-gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self-assembly of a thermoresponsive polymer, leading to macroscopic light-controlled sol-gel transitions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gel Phase Formation in Dilute Triblock Copolyelectrolyte Complexes

NASA Astrophysics Data System (ADS)

Srivastava, Samanvaya; Andreev, Marat; Prabhu, Vivek; de Pablo, Juan; Tirrell, Matthew

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at extremely low polymer concentrations (<1 % by mass) has been observed in scattering experiments and molecular dynamics simulations. In contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing polymer concentrations, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assemblies of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously upon solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of triblock copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries not only contribute to our fundamental understanding of the structure and pathways of complexation driven assemblies, but also raise intriguing prospects for formation of gel structures at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

Gel electrolytes and electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleischmann, Sven; Bunte, Christine; Mikhaylik, Yuriy V.

Gel electrolytes, especially gel electrolytes for electrochemical cells, are generally described. In some embodiments, the gel electrolyte layers comprise components a) to c). Component a) may be at least one layer of at least one polymer comprising polymerized units of: a1) at least one monomer containing an ethylenically unsaturated unit and an amido group and a2) at least one crosslinker. Component b) may be at least one conducting salt and component c) may be at least one solvent. Electrodes may comprise the components a), d) and e), wherein component a) may be at least one layer of at least onemore » polymer as described herein. Component d) may be at least one electroactive layer and component e) may be at least one ceramic layer. Furthermore, electrochemical cells comprising component a) which may be at least one layer of at least one polymer as described herein, are also provided.« less

Formulation of Convenient, Easily Scalable, and Efficient Granisetron HCl Intranasal Droppable Gels.

PubMed

Ibrahim, Howida K; Abdel Malak, Nevine S; Abdel Halim, Sally A

2015-06-01

Deacetylated gellan gum and two sodium alginate polymer types were used each at three concentrations in the suitable range for their sol-gel transition. The prepared nine droppable gels were evaluated in vitro, ex vivo through sheep nasal mucosa, as well as in vivo in comparison to drug solution given intravenously and orally at the same dose. The prepared formulas gelled instantaneously in simulated nasal fluid and the obtained gels sustained their shear thinning and thixotropic behavior up to 48 h. Polymer type and concentration had significant effects on the apparent viscosities and the in vitro release profile of granisetron from the prepared gels. The drug release data best fitted a modified Higuchi equation with initial burst and followed Fickian diffusion mechanism. A 0.5% gellan-gum-based formula sustained the in vitro drug release up to 3 h and enhanced the drug permeation without need for an enhancer. The histopatholgical study revealed the safety of the tested formula. Intranasal delivery recorded double the drug bioavailabilty in comparison to the oral route. It had an absolute bioavailability of 0.6539 and the maximum plasma drug concentration reached after 1.5 h. The developed formula could be promising for the management of chemotherapy-induced nausea and vomiting regarding its improved bioavailability, patient acceptability, and ease of production.

Mimicking nature: Self-strengthening properties in a dental adhesive.

PubMed

Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette

2016-04-15

Chemical and enzymatic hydrolysis provoke a cascade of events that undermine methacrylate-based adhesives and the bond formed at the tooth/composite interface. Infiltration of noxious agents, e.g. enzymes, bacteria, and so forth, into the spaces created by the defective bond will ultimately lead to failure of the composite restoration. This paper reports a novel, synthetic resin that provides enhanced hydrolytic stability as a result of intrinsic reinforcement of the polymer network. The behavior of this novel resin, which contains γ-methacryloxyproyl trimethoxysilane (MPS) as its Si-based compound, is reminiscent of self-strengthening properties found in nature. The efforts in this paper are focused on two essential aspects: the visible-light irradiation induced (photoacid-induced) sol-gel reaction and the mechanism leading to intrinsic self-strengthening. The FTIR band at 2840cm(-1) corresponding to CH3 symmetric stretch in -Si-O-CH3 was used to evaluate the sol-gel reaction. Results from the real-time FTIR indicated that the newly developed resin showed a limited sol-gel reaction (<5%) during visible-light irradiation, but after 48h dark storage, the reaction was over 65%. The condensation of methoxysilane mainly occurred under wet conditions. The storage moduli and glass transition temperature of the copolymers increased in wet conditions with the increasing MPS content. The cumulative amounts of leached species decreased significantly when the MPS-containing adhesive was used. The results suggest that the polymethacrylate-based network, which formed first as a result of free radical initiated polymerization, retarded the photoacid-induced sol-gel reaction. The sol-gel reaction provided a persistent, intrinsic reinforcement of the polymer network in both neutral and acidic conditions. This behavior led to enhanced mechanical properties of the dental adhesives under conditions that simulate the wet, oral environment. A self-strengthening dental adhesive system was developed through a dual curing process, which involves the free radical photopolymerization followed by slow hydrolysis and condensation (photoacid-induced sol-gel reaction) of alkoxylsilane groups. The concept of "living" photoacid-induced sol-gel reaction with visible-light irradiation was confirmed in the polymer. The sol-gel reaction was retarded by the polymethacrylate network, which was generated first; the network extended the life and retained the activity of silanol groups. The self-strengthening behavior was evaluated by monitoring the mechanical properties of the hybrid copolymers under wet conditions. The present research demonstrates the sol-gel reaction in highly crosslinked network as a potentially powerful strategy to prolong the functional lifetime of engineered biomaterials in wet environments. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Flexible all-solid-state asymmetric supercapacitors based on free-standing carbon nanotube/graphene and Mn3O4 nanoparticle/graphene paper electrodes.

PubMed

Gao, Hongcai; Xiao, Fei; Ching, Chi Bun; Duan, Hongwei

2012-12-01

We report the design of all-solid-state asymmetric supercapacitors based on free-standing carbon nanotube/graphene (CNTG) and Mn(3)O(4) nanoparticles/graphene (MG) paper electrodes with a polymer gel electrolyte of potassium polyacrylate/KCl. The composite paper electrodes with carbon nanotubes or Mn(3)O(4) nanoparticles uniformly intercalated between the graphene nanosheets exhibited excellent mechanical stability, greatly improved active surface areas, and enhanced ion transportation, in comparison with the pristine graphene paper. The combination of the two paper electrodes with the polymer gel electrolyte endowed our asymmetric supercapacitor of CNTG//MG an increased cell voltage of 1.8 V, a stable cycling performance (capacitance retention of 86.0% after 10,000 continuous charge/discharge cycles), more than 2-fold increase of energy density (32.7 Wh/kg) compared with the symmetric supercapacitors, and importantly a distinguished mechanical flexibility.

CONFORMANCE IMPROVEMENT USING GELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randall S. Seright

2003-09-01

This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysismore » suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of fractures (with widths from 1 to 4 mm) during brine and oil flow after placement. Regardless of gel age before placement, very little gel washed out from the fractures during brine or oil flow. However, increased brine or oil flow rate and cyclic injection of oil and water significantly decreased the level of permeability reduction. A particular need exists for gels that can plug large apertures (e.g., wide fractures and vugs). Improved mechanical strength and stability were demonstrated (in 1- to 4-mm-wide fractures) for a gel that contained a combination of high- and low-molecular weight polymers. This gel reduced the flow capacity of 2- and 4-mm-wide fractures by 260,000. In a 1-mm-wide fracture, it withstood 26 psi/ft without allowing any brine flow through the fracture. Cr(III)-acetate-HPAM gels exhibited disproportionate permeability reduction in fractures. The effect was most pronounced when the gel was placed as gelant or partially formed gels. The effect occurred to a modest extent with concentrated gels and with gels that were ''fully formed'' when placed. The effect was not evident in tubes. We explored swelling polymers for plugging fractures. Polymer suspensions were quickly prepared and injected. In concept, the partially dissolved polymer would lodge and swell to plug the fracture. For three types of swelling polymers, behavior was promising. However, additional development is needed before their performance will be superior to that of conventional gels.« less

Self-consistent field theory of polymer-ionic molecule complexation.

PubMed

Nakamura, Issei; Shi, An-Chang

2010-05-21

A self-consistent field theory is developed for polymers that are capable of binding small ionic molecules (adsorbates). The polymer-ionic molecule association is described by Ising-like binding variables, C(i) ((a))(kDelta)(=0 or 1), whose average determines the number of adsorbed molecules, n(BI). Polymer gelation can occur through polymer-ionic molecule complexation in our model. For polymer-polymer cross-links through the ionic molecules, three types of solutions for n(BI) are obtained, depending on the equilibrium constant of single-ion binding. Spinodal lines calculated from the mean-field free energy exhibit closed-loop regions where the homogeneous phase becomes unstable. This phase instability is driven by the excluded-volume interaction due to the single occupancy of ion-binding sites on the polymers. Moreover, sol-gel transitions are examined using a critical degree of conversion. A gel phase is induced when the concentration of adsorbates is increased. At a higher concentration of the adsorbates, however, a re-entrance from a gel phase into a sol phase arises from the correlation between unoccupied and occupied ion-binding sites. The theory is applied to a model system, poly(vinyl alcohol) and borate ion in aqueous solution with sodium chloride. Good agreement between theory and experiment is obtained.

Adhesive Properties of Polyacrylate Gels

NASA Astrophysics Data System (ADS)

Flanigan, Cynthia; Shull, Kenneth

1998-03-01

Soft, low-modulus gels provide an interesting opportunity to examine small adhesive interactions between two bodies in contact. As shown through dynamic rheological studies, our materials undergo a rapid gelation as they are cooled from a viscous liquid at elevated temperatures to a soft, elastic solid at room temperature. At low temperatures, the gels exhibit a linearly elastic response and display moduli close to 100Pa, thereby forming materials with great potential for quantifying weak adhesive interactions with a variety of bodies ranging from polymer surfaces to biological entities. Our current studies focus on investigating interfacial effects by performing axisymmetric adhesion tests with a model polyacrylate gel formed by diluting the copolymer poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) to a 5-15 percent solution in 2-ethyl hexanol, a selective solvent for the midblock. We have explored two different experimental geometries including a hemispherical rigid indenter of glass pressed into a gel layer of varying thicknesses, and a soft, gel cap in contact with a rigid polymer surface. By simultaneously measuring the applied load, displacement between the two bodies, and contact area during loading cycles, we are able to employ a linearly elastic fracture mechanics analysis to obtain estimates of the gel's modulus over a range of polymer concentrations, and G, the energy release rate.

A STUDY OF THE MECHANISM OF RADIATION-INDUCED GELATION IN MONOMER-POLYMER MIXTURES. Quarterly Summary Report, August 1, 1961-October 31, 1961

DOE Office of Scientific and Technical Information (OSTI.GOV)

Odian, G.; Bernstein, B.S.; Kelly, J.J.

1961-11-01

Gel contents can be obtained with polyethylene swollen with inhibitor- free allyl acrylate or inhibitor-free allyl methacrylate at a dose of only 0.05 Mrads Using Co/sup 60/ as the radiation source, allyl methacrylate gives higher gel content than allyl acrylate under similar conditions. icant and continues after Co/sup 60/ irradiation has been completed. Monomer desorption after a dose of 1.2 Mrads is less than after 0.05 Mrads, and does not continue after irradiation is stopped. Gel contents can be obtained without prior equilibrium swelling of polymer--monomer mixtures by irradiating the polymer in the presence of the monomer in a nitrogenmore » atmosphere. By irradiating under these conditions with prior equilibrium swelling, gel fractions appear to be higher than those normally obtained. Gel contents of irradiated equilibrium-swollen polyethylene/ allyl acrylate and polyethylene/allyl methacrylate increase with increasing radiation dose from 0.05 to 1.2 Mrads. Gel contents of 1.2 Mrad irradiated polyethyleneallyl methacrylate systems containing various initial amounts of monomer, increase with increasing monomer content. Polypropylene can be radiation crosslinked to give over 40% gel by prior equilibrium swelling with allyl acrylate or allyl methacrylate. (auth)« less

1,2-diketones promoted degradation of poly(epsilon-caprolactone)

NASA Astrophysics Data System (ADS)

Danko, Martin; Borska, Katarina; Ragab, Sherif Shaban; Janigova, Ivica; Mosnacek, Jaroslav

2012-07-01

Photochemical reactions of Benzil and Camphorquinone were used for modification of poly(ɛ-caprolactone) polymer films. Photochemistry of dopants was followed by infrared spectroscopy, changes on polymer chains of matrix were followed by gel permeation chromatography. Benzoyl peroxide was efficiently photochemically generated from benzyl in solid polymer matrix in the presence of air. Following decomposition of benzoyl peroxide led to degradation of matrix. Photochemical transformation of benzil in vacuum led to hydrogen abstraction from the polymer chains in higher extent, which resulted to chains recombination and formation of gel. Photochemical transformation of camphorquinone to corresponding camphoric peroxide was not observed. Only decrease of molecular weight of polymer matrix doped with camphorquinone was observed during the irradiation.

Rapid Self-healing Nanocomposite Hydrogel with Tunable Dynamic Mechanics

NASA Astrophysics Data System (ADS)

Li, Qiaochu; Mishra, Sumeet; Chapman, Brian; Chen, Pangkuan; Tracy, Joseph; Holten-Andersen, Niels

The macroscopic healing rate and efficiency in self-repairing hydrogel materials are largely determined by the dissociation dynamics of their polymer network, which is hardly achieved in a controllable manner. Inspired by mussel's adhesion chemistry, we developed a novel approach to assemble inorganic nanoparticles and catechol-decorated PEG polymer into a hydrogel network. When utilized as reversible polymer-particle crosslinks, catechol-metal coordination bonds yield a unique gel network with dynamic mechanics controlled directly by interfacial crosslink structure. Taking advantage of this structure-property relationship at polymer-particle interfaces, we designed a hierarchically structured hybrid gel with two distinct relaxation timescales. By tuning the relative contribution of the two relaxation modes, we are able to finely control the gel's dynamic mechanical behavior from a viscoelastic fluid to a stiff solid, yet preserving its rapid self-healing property without the need for external stimuli.

Fibrin-polyethylene oxide interpenetrating polymer networks: new self-supported biomaterials combining the properties of both protein gel and synthetic polymer.

PubMed

Akpalo, E; Bidault, L; Boissière, M; Vancaeyzeele, C; Fichet, O; Larreta-Garde, V

2011-06-01

Interpenetrating polymer network (IPN) architectures were conceived to improve the mechanical properties of a fibrin gel. Conditions allowing an enzymatic reaction to create one of the two networks in IPN architecture were included in the synthesis pathway. Two IPN series were carried out, starting from two polyethylene oxide (PEO) network precursors leading to different cross-linking densities of the PEO phase. The fibrin concentration varied from 5 to 20 wt.% in each series. The behavior of these materials during dehydration/hydration cycles was also studied. The mechanical properties of the resulting IPN were characterized in the wet and dry states. These self-supported biomaterials combine the properties of both a protein gel and a synthetic polymer. Finally, cells were grown on PEO/fibrin IPN, indicating that they are non-cytotoxic. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Cholesteric liquid crystal gels with a graded mechanical stress

NASA Astrophysics Data System (ADS)

Agez, Gonzague; Relaix, Sabrina; Mitov, Michel

2014-02-01

In cholesteric liquid-crystalline gels, the mechanical role of the polymer network over the structure of the whole gel has been ignored. We show that it is the stress gradient exerted by the network over the helical structure that drives the broadening of the optical band gap, as evidenced by the absence of a gradient in chiral species. Model calculations and finite-difference time-domain simulations show that the network acts as a spring with a stiffness gradient. The present results indicate a revision to the common understanding of the physical properties of liquid-crystalline gels is necessary when a concentration gradient in a polymer network is present.

Cholesteric liquid crystal gels with a graded mechanical stress.

PubMed

Agez, Gonzague; Relaix, Sabrina; Mitov, Michel

2014-02-01

In cholesteric liquid-crystalline gels, the mechanical role of the polymer network over the structure of the whole gel has been ignored. We show that it is the stress gradient exerted by the network over the helical structure that drives the broadening of the optical band gap, as evidenced by the absence of a gradient in chiral species. Model calculations and finite-difference time-domain simulations show that the network acts as a spring with a stiffness gradient. The present results indicate a revision to the common understanding of the physical properties of liquid-crystalline gels is necessary when a concentration gradient in a polymer network is present.

Living Additive Manufacturing: Transformation of Parent Gels into Diversely Functionalized Daughter Gels Made Possible by Visible Light Photoredox Catalysis

PubMed Central

2017-01-01

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinduced single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized. PMID:28280779

Living Additive Manufacturing: Transformation of Parent Gels into Diversely Functionalized Daughter Gels Made Possible by Visible Light Photoredox Catalysis.

PubMed

Chen, Mao; Gu, Yuwei; Singh, Awaneesh; Zhong, Mingjiang; Jordan, Alex M; Biswas, Santidan; Korley, LaShanda T J; Balazs, Anna C; Johnson, Jeremiah A

2017-02-22

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials "dead" toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative "living additive manufacturing" strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant "parent" materials to generate more complex and diversely functionalized "daughter" materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinduced single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent's average composition, strand length, and/or cross-linking density. Daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.

Dose response evaluation of a low-density normoxic polymer gel dosimeter using MRI

NASA Astrophysics Data System (ADS)

Haraldsson, P.; Karlsson, A.; Wieslander, E.; Gustavsson, H.; Bäck, S. Å. J.

2006-02-01

A low-density (~0.6 g cm-3) normoxic polymer gel, containing the antioxidant tetrakis (hydroxymethyl) phosponium (THP), has been investigated with respect to basic absorbed dose response characteristics. The low density was obtained by mixing the gel with expanded polystyrene spheres. The depth dose data for 6 and 18 MV photons were compared with Monte Carlo calculations. A large volume phantom was irradiated in order to study the 3D dose distribution from a 6 MV field. Evaluation of the gel was carried out using magnetic resonance imaging. An approximately linear response was obtained for 1/T2 versus dose in the dose range of 2 to 8 Gy. A small decrease in the dose response was observed for increasing concentrations of THP. A good agreement between measured and Monte Carlo calculated data was obained, both for test tubes and the larger 3D phantom. It was shown that a normoxic polymer gel with a reduced density could be obtained by adding expanded polystyrene spheres. In order to get reliable results, it is very important to have a uniform distribution of the gel and expanded polystyrene spheres in the phantom volume.

Poster - Thur Eve - 69: Electron beam dosimetry in heterogeneous phantoms using the MAGIC normoxic polymer gel.

PubMed

Nedaie, H A; Ghahraman, A R; Bolouri, B; Arbabi, A

2012-07-01

Recently, radiation sensitive polymer gels are being used as a reliable dosimetry method for three-dimensional (3D) verification of radiation doses in clinical use. Some properties of gel dosimeters have made them useful in verifying complex situations in electron therapy. The aim of this study was to experimentally evaluate the influence of tissue inhomogeneities on electron beam dose distributions by use of polymer gel dosimetry. Another purpose was to evaluate the appropriateness of polymer gels for electron beam dosimetry applications. A cylindrical phantom filled with MAGIC polymer gel with a polyacrilic wall (ρ = 1.18 g.cm -3 ) was placed in a Perspex water-filled tank exactly underneath the bone inhomogeneity region .Then, the slab phantom was irradiated with a dose of 5Gy of 8MeV electrons to measure the dose distribution beyond the heterogeneity region. Afterwards, another cylindrical gel phantom similar to the above was used and irradiated with the same dose of 15 MeV electrons to measure the dose distribution beyond the same heterogeneity region. The same mentioned setup was repeated for measurement of the dose distribution beneath the air heterogeneity and homogenous phantom. The results of gel dosimetry under bone inhomogeneity have shown a reduction in dose. This is related to the high mass stopping and mass scattering powers of bone tissue. In addition, dose enhancement is seen laterally near the bone-tissue interface, due to increased side scattering of electrons. Hot and cold scatter lobes under heterogeneity regions are other effects that can be seen. The results of gel dosimetry under the air inhomogeneity have shown an increase in dose. This is related to the low mass stopping and mass scattering powers of the air cavity. When a high energy beam passes through a low-density medium or an air cavity, electronic equilibrium is lost along the central axis of the beam .The dose rebuild up is a consequence of this electronic disequilibrium. An overall good agreement was found between measurements with gel and with a diode detector for the single beam experiment. Electron dose distributions are significantly altered in the presence of tissue inhomogeneities such as bone and air cavities which are related to mass stopping and mass scattering powers of heterogeneous materials. © 2012 American Association of Physicists in Medicine.

Polymer-gel formation and reformation on irradiation of tertiary-butyl acrylate

NASA Astrophysics Data System (ADS)

Yao, Tiantian; Denkova, Antonia G.; Warman, John M.

2014-04-01

The purpose of the present research was to provide a radiation-chemical basis for the use of tertiary-butyl acrylate gels in radio-fluorogenic dose-imaging applications (Warman et al. 2011a,b, 2013a,b). The radiation-induced polymerization of tertiary-butyl acrylate (TBA) results in the formation of a transparent gel with an optical density lower than 0.1 cm-1 from 600 nm down to 315 nm. The fractional monomer-to-polymer conversion, CM, determined gravimetrically, increases super-linearly with dose, D Gy. Up to CM≈40%, and over the dose rate range D‧=3.5 to 49 cGy s-1, the dose dependence is given by CM=[1+ACM]KD/√D‧ with K=1.43×10-3 Gy-0.5 s-0.5 and A=0.70. For D‧=3.5 cGy s-1 the average polymer size is estimated to be 1.2×105 monomer units or 17 megadalton. For CM≥10% the gel is quasi-rigid, displaying little tendency to flow on a timescale of an hour or more. After removal of monomer by evacuation, the gel can be reformed by adding a volume of monomer to the remaining polymer equal to that removed and allowing this to swell for several days. The dose and dose rate dependence of radiation-induced monomer conversion in the reformed gel show no evidence of a discontinuity caused by the intervening evacuation and reformation procedures.

Polymer/graphite oxide composites as high-performance materials for electric double layer capacitors

NASA Astrophysics Data System (ADS)

Tien, Chien-Pin; Teng, Hsisheng

A single graphene sheet represents a carbon material with the highest surface area available to accommodating molecules or ions for physical and chemical interactions. Here we demonstrate in an electric double layer capacitor the outstanding performance of graphite oxide for providing a platform for double layer formation. Graphite oxide is generally the intermediate compound for obtaining separated graphene sheets. Instead of reduction with hydrazine, we incorporate graphite oxide with a poly(ethylene oxide)-based polymer and anchor the graphene oxide sheets with poly(propylene oxide) diamines. This polymer/graphite oxide composite shows in a "dry" gel-electrolyte system a double layer capacitance as high as 130 F g -1. The polymer incorporation developed here can significantly diversify the application of graphene-based materials in energy storage devices.

Investigation of dose characteristics in three-dimensional MAGAT-type polymer gel dosimetry with MSE MR imaging

NASA Astrophysics Data System (ADS)

Lee, Jason J. S.; Tsai, Chia-Jung; Lo, Man-Kuok; Huang, Yung-Hui; Chen, Chien-Chuan; Wu, Jay; Tyan, Yeu-Sheng; Wu, Tung-Hsin

2008-05-01

A new type of normoxic polymer gel dosimeter, named MAGAT responses well to absorbed dose even when manufacturing in the presence of normal levels of oxygen. The aim of this study was to evaluate dose response, diffusion effect and cumulated dose response under multiple fractional irradiations of the MAGAT gel dosimeter using Multiple Spin-Echo (MSE) Magnetic Resonance (MR) sequence. Dose response was performed by irradiating MAGAT-gel-filled testing vials with a 6 MV linear accelerator and a linear relationship was present with doses from 0 to 6 Gy, but gradually, a bi-exponential function result was obtained with given doses up to 20 Gy. No significant difference in dose response was present between single and cumulated doses (p > 0.05). For study of diffusion effect, edge sharpness of the R2 map imaging between two split doses was smaller than 1 cm of dose profile penumbra between 20% and 80%. In conclusion, the MAGAT polymer gel dosimeter with MSE MR imaging is a promising method for dose verification in clinical radiation therapy practice.

Performance evaluation of an improved optical computed tomography polymer gel dosimeter system for 3D dose verification of static and dynamic phantom deliveries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopatiuk-Tirpak, O.; Langen, K. M.; Meeks, S. L.

2008-09-15

The performance of a next-generation optical computed tomography scanner (OCTOPUS-5X) is characterized in the context of three-dimensional gel dosimetry. Large-volume (2.2 L), muscle-equivalent, radiation-sensitive polymer gel dosimeters (BANG-3) were used. Improvements in scanner design leading to shorter acquisition times are discussed. The spatial resolution, detectable absorbance range, and reproducibility are assessed. An efficient method for calibrating gel dosimeters using the depth-dose relationship is applied, with photon- and electron-based deliveries yielding equivalent results. A procedure involving a preirradiation scan was used to reduce the edge artifacts in reconstructed images, thereby increasing the useful cross-sectional area of the dosimeter by nearly amore » factor of 2. Dose distributions derived from optical density measurements using the calibration coefficient show good agreement with the treatment planning system simulations and radiographic film measurements. The feasibility of use for motion (four-dimensional) dosimetry is demonstrated on an example comparing dose distributions from static and dynamic delivery of a single-field photon plan. The capability to visualize three-dimensional dose distributions is also illustrated.« less

Intelligent windows using new thermotropic layers with long-term stability

NASA Astrophysics Data System (ADS)

Watanabe, Haruo

1995-08-01

This paper concerns the autonomous responsive type light adjustment window (intelligent windows) among smart windows which adjust the light upon receiving environmental energy. More specifically, this is a thermotropic window panel that laminates and seals a new type of highly viscous polymer aqueous solution gel. A conventional thermotropic window panel has never been put to practical use since the reversible change between the colorless, transparent state (water-clear) and translucent scattered state (paper-white) with uniformity was not possible. The change involved phase separation and generated non-uniformity. The author, after fundamental studies of hydrophobic bonding, successfully solved the problem by developing a polymer aqueous solution gel with amphiphatic molecule as the third component in addition to water and water-soluble polymer with hydrophobic radical, based on the molecular spacer concept. In addition, the author established peripheral technologies and succeeded in experimentally fabricating a panel type 'Affinity's Intelligent Window (AIW)' that has attained the level of practical use.

Electrical and electrochemical studies on sodium ion-based gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Isa, K. B. Md; Othman, L.; Hambali, D.; Osman, Z.

2017-09-01

Gel polymer electrolytes (GPEs) have captured great attention because of their unique properties such as good mechanical stability, high flexibility and high conductivity approachable to that of the liquid electrolytes. In this work, we have prepared sodium ion conducting gel polymer electrolyte (GPE) films consisting of polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) as a polymer host using the solution casting technique. Sodium trifluoromethane- sulfonate (NaCF3SO3) was used as an ionic salt and the mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizing solvent. Impedance spectroscopy measurements were carried out to determine the ionic conductivity of the GPE films. The sample containing 20 wt.% of NaCF3SO3 salt exhibits the highest room temperature ionic conductivity of 2.50 × 10-3 S cm-1. The conductivity of the GPE films was found to depend on the salt concentration that added to the films. The ionic and cationic transference numbers of GPE films were estimated by DC polarization and the combination of AC and DC polarization method, respectively. The results had shown that both ionic and cationic transference numbers are consistent with the conductivity studies. The electrochemical stability of the GPE films was tested using linear sweep voltammetry (LSV) and the value of working voltage range appears to be high enough to be used as an electrolyte in sodium batteries. The cyclic voltammetry (CV) studies confirmed the sodium ion conduction in the GPE films.

Iodopropyl-branched polysiloxane gel electrolytes with improved ionic conductivity upon cross-linking.

PubMed

De Gregorio, G L; Giannuzzi, R; Cipolla, M P; Agosta, R; Grisorio, R; Capodilupo, A; Suranna, G P; Gigli, G; Manca, M

2014-11-21

We here report the implementation of poly[(3-N-methylimidazoliumpropyl)methylsiloxane-co-dimethylsiloxane]iodides as suitable polymeric hosts for a novel class of in situ cross-linkable iodine/iodide-based gel-electrolytes for dye-sensitized solar cells. The polymers are first partially quaternized and then subjected to a thermal cross-linking which allows the formation of a 3D polymeric network which is accompanied by a dramatic enhancement of the ionic conductivity.

Comparative study of nuclear magnetic resonance and UV-visible spectroscopy dose-response of polymer gel based on N-(Isobutoxymethyl) acrylamide

NASA Astrophysics Data System (ADS)

Lotfy, S.; Basfar, A. A.; Moftah, B.; Al-Moussa, A. A.

2017-12-01

A comparative study of nuclear magnetic resonance and UV-visible spectroscopy of dose-response for polymer gel dosimeters was performed. Dosimeters were prepared using N-(Isobutoxymethyl) acrylamide (NIBMA) as a new monomer via radiation induced polymerization for use in radiotherapy planning. The prepared dosimeters were irradiated with doses up to 30 Gy at a constant dose rate of 600 MU/min. Using a medical linear accelerator at irradiation energies of 6, 10 and 18 MV photon beam. The nuclear magnetic resonance (NMR), via spin-spin relaxation rate (R2) for water proton surrounding the polymer formulation and UV-Visible spectroscopy, via the optical absorbance measurements of irradiated dosimeters at selected wavelengths of 500 nm, was used to investigate the dose response of NIBMAGAT gel dosimeters. Scavenge of oxygen was done using tetrakis (hydroxymethyl) phosphonium chloride (THPC). The THPC optimum concentration in the dosimeters formulations were 5 and 10 mM for the NMR and optical absorbance measurements respectively. The quantitative investigation of the dosimeters components reveals the selective formulations based on 4% w/w gelatin, 1% w/w NIBMA, 3% w/w BisAAm, 5 or 10 mM THPC and 17% w/w glycerol which significantly increase the dosimeters dose response. The prepared dosimeters were found to be dose rate and photon beam irradiation energy independent. The stability study shows no change in the relaxation rate or in the optical absorbance of the gel dosimeters up to 8 days post-irradiation. The prepared polymer gel dosimeters at the energies of 6, 10 and 18 MV photon beam irradiation in the range of 1-30 Gy have the linearity of the dose response function in the case of R2 is better than in the case of absorbance measurements; correlation coefficient (r2) equals 0.995 and 0.991, respectively. Dose sensitivity, R2 of NIBMAGAT dosimeters (0.0775 s-1 Gy-1). The absorption band intensity increases linearly with a dose sensitivity of 0.016 cm-1 Gy-1. The detection limit of the present dosimeter analyzed by R2 and absorbance measurements is 1 Gy and 2 Gy respectively. The overall uncertainty measurements of dose approve that by using the absorbance measurements the gel is not useful as a dosimeter like as R2 measurements. It could be a new composition of dosimeters successfully utilized for MRI (Magnetic Resonance Imaging) for radiotherapy treatment planning.

An application of optical coherence tomography and a smart polymer gel to construct an enzyme-free sugar sensor

NASA Astrophysics Data System (ADS)

Ouiganon, Sirirat; Thammakhet, Chongdee; Thavarungkul, Panote; Kanatharana, Proespichaya; Buranachai, Chittanon

2016-06-01

This work reports a novel enzyme-free sugar sensor development based on optical coherence tomography (OCT) and a 3-acrylamidophenylboronic acid-acrylamide copolymer gel that swells when it binds sugar molecules. Utilizing OCT to measure the gel swelling in the presence of glucose and fructose, selected as model targets, the sensor provided a linear range of 2.5-20.0 mM for glucose and 0.01-0.20 mM for fructose detections with a good sensitivity for both sugars under optimal conditions. With some further improvements, the sensor could be used in harsh conditions that are not suitable for enzyme-based sugar sensors and for highly visible light-absorbing solutions.

Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers.

PubMed

Karlsson, Rose-Marie Pernilla; Larsson, Per Tomas; Yu, Shun; Pendergraph, Samuel Allen; Pettersson, Torbjörn; Hellwig, Johannes; Wågberg, Lars

2018-06-01

Macroscopic beads of water-based gels consisting of uncharged and partially charged β-(1,4)-d-glucan polymers were developed to be used as a novel model material for studying the water induced swelling of the delignified plant fiber walls. The gel beads were prepared by drop-wise precipitation of solutions of dissolving grade fibers carboxymethylated to different degrees. The internal structure was analyzed using Solid State Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance and Small Angle X-ray Scattering showing that the internal structure could be considered a homogeneous, non-crystalline and molecularly dispersed polymer network. When beads with different charge densities were equilibrated with aqueous solutions of different ionic strengths and/or pH, the change in water uptake followed the trends expected for weak polyelectrolyte gels and the trends found for cellulose-rich fibers. When dried and subsequently immersed in water the beads also showed an irreversible loss of swelling depending on the charge and type of counter-ion which is commonly also found for cellulose-rich fibers. Taken all these results together it is clear that the model cellulose-based beads constitute an excellent tool for studying the fundamentals of swelling of cellulose rich plant fibers, aiding in the elucidation of the different molecular and supramolecular contributions to the swelling. Copyright © 2018 Elsevier Inc. All rights reserved.

Mimicking Nature: Self-strengthening Properties in a Dental Adhesive

PubMed Central

Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette

2016-01-01

Chemical and enzymatic hydrolysis provoke a cascade of events that undermine methacrylate-based adhesives and the bond formed at the tooth/composite interface. Infiltration of noxious agents, e.g. enzymes, bacteria, and so forth, into the spaces created by the defective bond will ultimately lead to failure of the composite restoration. This paper reports a novel, synthetic resin that provides enhanced hydrolytic stability as a result of intrinsic reinforcement of the polymer network. The behavior of this novel resin, which contains γ-methacryloxyproyl trimethoxysilane (MPS) as its Si-based compound, is reminiscent of self-strengthening properties found in nature. The efforts in this paper are focused on two essential aspects: the visible-light irradiation induced (photoacid-induced) sol-gel reaction and the mechanism leading to intrinsic self-strengthening. The FTIR band at 2840 cm−1 corresponding to CH3 symmetric stretch in −Si−O−CH3 was used to evaluate the sol-gel reaction. Results from the real-time FTIR indicated that the newly developed resin showed a limited sol-gel reaction (<5%) during visible-light irradiation, but after 48h dark storage, the reaction was over 65%. The condensation of methoxysilane mainly occurred under wet conditions. The storage moduli and glass transition temperature of the copolymers increased in wet conditions with the increasing MPS content. The cumulative amounts of leached species decreased significantly when the MPS-containing adhesive was used. The results suggest that the polymethacrylate-based network, which formed first as a result of free radical initiated polymerization, retarded the photoacid-induced sol-gel reaction. The sol-gel reaction provided a persistent, intrinsic reinforcement of the polymer network in both neutral and acidic conditions. This behavior led to enhanced mechanical properties of the dental adhesives under conditions that simulate the wet, oral environment. PMID:26883773

Dose evaluation of an NIPAM polymer gel dosimeter using gamma index

NASA Astrophysics Data System (ADS)

Chang, Yuan-Jen; Lin, Jing-Quan; Hsieh, Bor-Tsung; Yao, Chun-Hsu; Chen, Chin-Hsing

2014-11-01

An N-isopropylacrylamide (NIPAM) polymer gel dosimeter has great potential in clinical applications. However, its three-dimensional dose distribution must be assessed. In this work, a quantitative evaluation of dose distributions was performed to evaluate the NIPAM polymer gel dosimeter using gamma analysis. A cylindrical acrylic phantom filled with NIPAM gel measuring 10 cm (diameter) by 10 cm (height) by 3 mm (thickness) was irradiated by a 4×4 cm2 square light field. The irradiated gel phantom was scanned using an optical computed tomography (optical CT) scanner (OCTOPUS™, MGS Research, Inc., Madison, CT, USA) at 1 mm resolution. The projection data were transferred to an image reconstruction program, which was written using MATLAB (The MathWorks, Natick, MA, USA). The program reconstructed the image of the optical density distribution using the algorithm of a filter back-projection. Three batches of replicated gel phantoms were independently measured. The average uncertainty of the measurements was less than 1%. The gel was found to have a high degree of spatial uniformity throughout the dosimeter and good temporal stability. A comparison of the line profiles of the treatment planning system and of the data measured by optical CT showed that the dose was overestimated in the penumbra region because of two factors. The first is light scattering due to changes in the refractive index at the edge of the irradiated field. The second is the edge enhancement caused by free radical diffusion. However, the effect of edge enhancement on the NIPAM gel dosimeter is not as significant as that on the BANG gel dosimeter. Moreover, the dose uncertainty is affected by the inaccuracy of the gel container positioning process. To reduce the uncertainty of 3D dose distribution, improvements in the gel container holder must be developed.

Characterization of internal structure of hydrated agar and gelatin matrices by cryo-SEM.

PubMed

Rahbani, Janane; Behzad, Ali R; Khashab, Niveen M; Al-Ghoul, Mazen

2013-02-01

There has been a considerable interest in recent years in developing polymer gel matrices for many important applications such as 2DE for quantization and separation of a variety of proteins and drug delivery system to control the release of active agents. However, a well-defined knowledge of the ultrastructures of the gels has been elusive. In this study, we report the characterization of two different polymers used in 2DE: Gelatin, a naturally occurring polymer derived from collagen (protein) and agar, a polymer of polysaccharide (sugar) origin. Low-temperature SEM is used to examine the internal structure of these gels in their frozen natural hydrated states. Results of this study show that both polymers have an array of hollow cells that resembles honeycomb structures. While agar pores are almost circular, the corresponding Gaussian curve is very broad exhibiting a range of radii from nearly 370 to 700 nm. Gelatin pores are smaller and more homogeneous reflecting a narrower distribution from nearly 320 to 650 nm. Overall, these ultrastructural findings could be used to correlate with functions of the polymers. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computational investigation of suitable polymer gel composition for the QA of the beam components of a BNCT irradiation field.

PubMed

Tanaka, Kenichi; Sakurai, Yoshinori; Hayashi, Shin-Ichiro; Kajimoto, Tsuyoshi; Uchida, Ryohei; Tanaka, Hiroki; Takata, Takushi; Bengua, Gerard; Endo, Satoru

2017-09-01

This study investigated the optimum composition of the MAGAT polymer gel which is to be used in the quality assurance measurement of the thermal neutron, fast neutron and gamma ray components in the irradiation field used for boron neutron capture therapy at the Kyoto University Reactor. Simulations using the PHITS code showed that when combined with the gel, 6 Li concentrations of 0, 10 and 100ppm were found to be potentially usable. Copyright © 2017 Elsevier Ltd. All rights reserved.

1,2-diketones promoted degradation of poly(epsilon-caprolactone)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danko, Martin; Borska, Katarina; Ragab, Sherif Shaban

2012-07-11

Photochemical reactions of Benzil and Camphorquinone were used for modification of poly({epsilon}-caprolactone) polymer films. Photochemistry of dopants was followed by infrared spectroscopy, changes on polymer chains of matrix were followed by gel permeation chromatography. Benzoyl peroxide was efficiently photochemically generated from benzyl in solid polymer matrix in the presence of air. Following decomposition of benzoyl peroxide led to degradation of matrix. Photochemical transformation of benzil in vacuum led to hydrogen abstraction from the polymer chains in higher extent, which resulted to chains recombination and formation of gel. Photochemical transformation of camphorquinone to corresponding camphoric peroxide was not observed. Only decreasemore » of molecular weight of polymer matrix doped with camphorquinone was observed during the irradiation.« less

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions

PubMed Central

Yin, De-Wei; Horkay, Ferenc; Douglas, Jack F.; de Pablo, Juan J.

2008-01-01

Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the Flory–Huggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory–Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions. PMID:19045224

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions.

PubMed

Yin, De-Wei; Horkay, Ferenc; Douglas, Jack F; de Pablo, Juan J

2008-10-21

Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the Flory-Huggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory-Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions.

(ZrO 2) 0.85( REO 1.5) 0.15 ( RE=Sc, Y) solid solutions prepared via three Pechini-type gel routes: 1—gel formation and calcination behaviors

NASA Astrophysics Data System (ADS)

Zhang, Yawen; Li, Ang; Yan, Zhengguang; Xu, Gang; Liao, Chunsheng; Yan, Chunhua

2003-02-01

(ZrO2)0.85(REO1.5)0.15 (RE=Sc, Y) nanoparticles with pure cubic fluorite structure have been synthesized by three Pechini-type gel routes, viz. poly(vinyl alcohol) containing-process (route I), poly(ethylene glycol) and formic acid-containing process (route II), and in situ polymerizable complex method (route III). The coordination modes between metal ions and polymers in the gels are shown to be highly correlative with the synthesis route used. The gels prepared by route III have the strongest coordination throughout their network and therefore the best chemical homogeneity. The altered variety of polymer and cross-linking within the gels adopted by these three routes has made the as-synthesized samples show appreciable differences in thermal behavior, powder reactivity and nanoparticle properties.

Pyrocarbons prepared by carbonisation of polymers adsorbed or synthesised on a surface of silica and mixed oxides

NASA Astrophysics Data System (ADS)

Gun'ko, V. M.; Skubiszewska-Zi ęba, J.; Leboda, R.; Voronin, E. F.; Zarko, V. I.; Levitskaya, S. I.; Brei, V. V.; Guzenko, N. V.; Kazakova, O. A.; Seledets, O.; Janusz, W.; Chibowski, S.

2004-04-01

Initial oxides fumed silica, alumina/silica and titania/silica and silica gel and hybrid adsorbents with pyrocarbon formed on these oxide substrates by carbonisation of immobilised (adsorbed or synthesised) polymers such as starch, methyl cellulose, polyvinylpyrrolidone, polystyrene, and polybutylvinyl ether were studied by adsorption, AFM, TEM, and FTIR methods. Polymer/oxide materials were investigated by nitrogen and Pb(II) adsorption, FTIR, and potentiometric titration methods. Analysis of nitrogen adsorption-desorption isotherms by different methods, FTIR spectra, AFM and TEM images of the initial and hybrid adsorbents reveals that the morphology of the substrates significantly changes on carbonisation of oxygen-containing polymers because of hydrothermal treatment of them by water eliminated as a product of pyrolysis. Contribution of own microporosity of pyrocarbon deposits formed on carbonisation of immobilised polymers is greater (dependent on reaction conditions) than that on pyrolysis of low-molecular compounds at the same oxide substrates. Pyrocarbon particles formed on silica gel are larger than those formed on fumed oxides and larger than those formed on silica gel on pyrolysis of low-molecular compounds.

Determining equilibrium osmolarity in poly(ethylene glycol)/chondrotin sulfate gels mimicking articular cartilage.

PubMed

Sircar, S; Aisenbrey, E; Bryant, S J; Bortz, D M

2015-01-07

We present an experimentally guided, multi-phase, multi-species polyelectrolyte gel model to make qualitative predictions on the equilibrium electro-chemical properties of articular cartilage. The mixture theory consists of two different types of polymers: poly(ethylene gylcol) (PEG), chondrotin sulfate (ChS), water (acting as solvent) and several different ions: H(+), Na(+), Cl(-). The polymer chains have covalent cross-links whose effect on the swelling kinetics is modeled via Doi rubber elasticity theory. Numerical studies on equilibrium polymer volume fraction and net osmolarity (difference in the solute concentration across the gel) show a complex interplay between ionic bath concentrations, pH, cross-link fraction and the average charge per monomer. Generally speaking, swelling is aided due to a higher average charge per monomer (or a higher particle fraction of ChS, the charged component of the polymer), low solute concentration in the bath, a high pH or a low cross-link fraction. A peculiar case arises at higher values of cross-link fraction, where it is observed that increasing the average charge per monomer leads to gel deswelling. Copyright © 2014 Elsevier Ltd. All rights reserved.

High performance photolithographically-patterned polymer thin-film transistors gated with an ionic liquid/poly(ionic liquid) blend ion gel

NASA Astrophysics Data System (ADS)

Thiburce, Q.; Porcarelli, L.; Mecerreyes, D.; Campbell, A. J.

2017-06-01

We demonstrate the fabrication of polymer thin-film transistors gated with an ion gel electrolyte made of the blend of an ionic liquid and a polymerised ionic liquid. The ion gel exhibits a high stability and ionic conductivity, combined with facile processing by simple drop-casting from solution. In order to avoid parasitic effects such as high hysteresis, high off-currents, and slow switching, a fluorinated photoresist is employed in order to enable high-resolution orthogonal patterning of the polymer semiconductor over an area that precisely defines the transistor channel. The resulting devices exhibit excellent characteristics, with an on/off ratio of 106, low hysteresis, and a very large transconductance of 3 mS. We show that this high transconductance value is mostly the result of ions penetrating the polymer film and doping the entire volume of the semiconductor, yielding an effective capacitance per unit area of about 200 μF cm-2, one order of magnitude higher than the double layer capacitance of the ion gel. This results in channel currents larger than 1 mA at an applied gate bias of only -1 V. We also investigate the dynamic performance of the devices and obtain a switching time of 20 ms, which is mostly limited by the overlap capacitance between the ion gel and the source and drain contacts.

Lipophilic Super-Absorbent Swelling Gels as Cleaners for Use on Weapons Systems and Platforms

DTIC Science & Technology

2011-08-18

polymer gel systems. Further research will address the post-cleaning gel removal method, the use of non- fluorinated compounds in gel synthesis, and...be proposed to address other issues including the method for removing the gels after swelling, the use of non- fluorinated compounds in gel...strength. Elimination of fluorinated compounds in the gel synthesis was the focus of this and subsequent phases of this research. TECHNICAL APPROACH

Synthesis and Anticoagulant Activity of Polyureas Containing Sulfated Carbohydrates

PubMed Central

2015-01-01

Polyurea-based synthetic glycopolymers containing sulfated glucose, mannose, glucosamine, or lactose as pendant groups have been synthesized by step-growth polymerization of hexamethylene diisocyanate and corresponding secondary diamines. The obtained polymers were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The nonsulfated polymers showed similar results to the commercially available biomaterial polyurethane TECOFLEX in a platelet adhesion assay. The average degree of sulfation after reaction with SO3 was calculated from elemental analysis and found to be between three and four −OSO3 groups per saccharide. The blood-compatibility of the synthetic polymers was measured using activated partial thromboplastin time, prothrombin time, thrombin time, anti-IIa, and anti-Xa assays. Activated partial thromboplastin time, prothrombin time, and thrombin time results indicated that the mannose and lactose based polymers had the highest anticoagulant activities among all the sulfated polymers. The mechanism of action of the polymers appears to be mediated via an anti-IIa pathway rather than an anti-Xa pathway. PMID:25329742

Living additive manufacturing: Transformation of parent gels into diversely functionalized daughter gels made possible by visible light photoredox catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Mao; Gu, Yuwei; Singh, Awaneesh

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinducedmore » single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Furthermore, daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.« less

Living additive manufacturing: Transformation of parent gels into diversely functionalized daughter gels made possible by visible light photoredox catalysis

DOE PAGES

Chen, Mao; Gu, Yuwei; Singh, Awaneesh; ...

2017-01-13

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinducedmore » single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Furthermore, daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.« less

New Gel-Like Polymers as Selective Weak-Base Anion Exchangers

PubMed Central

Gierczyk, Błażej; Cegłowski, Michał; Zalas, Maciej

2015-01-01

A group of new anion exchangers, based on polyamine podands and of excellent ion-binding capacity, were synthesized. The materials were obtained in reactions between various poly(ethyleneamines) with glycidyl derivatives of cyclotetrasiloxane. The final polymeric, strongly cross-linked materials form gel-like solids. Their structures and interactions with anions adsorbed were studied by spectroscopic methods (CP-MAS NMR, FR-IR, UV-Vis). The sorption isotherms and kinetic parameters were determined for 29 anions. Materials studied show high ion capacity and selectivity towards some important anions, e.g., selenate(VI) or perrhenate. PMID:25946220

A functionalizable reverse thermal gel based on a polyurethane/PEG block copolymer

PubMed Central

Park, Daewon; Wu, Wei; Wang, Yadong

2010-01-01

Injectable reverse thermal gels have great potentials as biomaterials for tissue engineering and drug delivery. However, most existing gels lack functional groups that can be modified with biomolecules that can guide cell/material interactions. We created an amine-functionalized ABA block copolymer, poly(ethylene glycol)-poly(serinol hexamethylene urethane), or ESHU. This reverse thermal gel consists of a hydrophobic block (B): poly(serinol hexamethylene urethane) and a hydrophilic block (A): poly(ethylene glycol). The polymer was characterized by GPC, FTIR and 1H FTNMR. Rheological study demonstrated that ESHU solution in phosphate-buffered saline initiated phase transition at 32°C and reached maximum elastic modulus at 37°C. The in vitro degradation tests performed in PBS and cholesterol esterase solutions revealed that the polymer was hydrolyzable and the presence of cholesterol esterase greatly accelerated the hydrolysis. The in vitro cytotoxicity tests carried out using baboon smooth muscle cells demonstrated that ESHU had good cytocompatibility with cell viability indistinguishable from tissue culture treated polystyrene. Subcutaneous implantation in rats revealed well tolerated accurate inflammatory response with moderate ED-1 positive macrophages in the early stages, which largely resolved 4 weeks post-implantation. We functionalized ESHU with a hexapeptide, Ile-Lys-Val-Ala-Val-Ser (IKVAVS), which gelled rapidly at body temperature. We expect this new platform of functionalizable reverse thermal gels to provide versatile biomaterials in tissue engineering and regenerative medicine. PMID:20937526

Highly efficient gel-state dye-sensitized solar cells prepared using propionitrile and poly(vinylidene fluoride-co-hexafluoropropylene)

NASA Astrophysics Data System (ADS)

Venkatesan, Shanmuganathan; Hidayati, Noor; Liu, I.-Ping; Lee, Yuh-Lang

2016-12-01

Propionitrile (PPN) solvent based iodide/triiodide liquid-electrolyte is utilized to prepare highly efficient poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer gel electrolytes (PGEs) of dye-sensitized solar cells, aiming at improving the energy conversion efficiency as well as the stability of gel-state DSSCs. The concentrations effect of the PVdF-HFP on the properties of PGEs and the performance of the corresponding cells are studied. The results show that the in-situ gelation is performed for the PVdF-HFP concentration range of 8-18% at room temperature. However, increasing the concentration of polymer in the PGEs triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the phase transition temperature of the PGEs. A high phase transition temperature is obtained for the PGEs with 18 wt% PVdF-HFP, which increase the long-term stability of the gel-state DSSC. By using the 18 wt% PVdF-HFP in the presence of 5 wt% TiO2 nanofillers (NFs), gel-state cells with an efficiency of 8.38% can be obtained, which is higher than that achieved by liquid-state cells (7.55%). After 1000 h test at room temperature (RT) and 50 °C, the cell can retain 96% and 82%, respectively, of its initial efficiency.

Lamellar Biogels: Fluid-Membrane Based Hydrogels Containing Polymer-Lipids

NASA Astrophysics Data System (ADS)

Warriner, Heidi E.; Davidson, P.; Slack, N. L.; Idziak, S. H. J.; Schmidt, H. W.; Safinya, C. R.

1996-03-01

A new class of lamellar biogels containing low molecular weight (MW 5181, 2053 and 576 g/mole) polyethylene glycol-surfactants is described (H. Warriner et. al., Science, (in press)). The gels were formed in 7 different systems using two types of polymer-surfactants: (i) polymer-lipids based on the lipid DMPE covalently attached to the different MW of PEG (ii) polymer-surfactants of the two largest PEG MW covalently attached to double-tailed phenyl surfactants with 14 or 18 carbon tails. Unlike isotropic hydrogels of polymer networks, these membrane-based liquid crystalline biogels, labeled L_α,g, form through the addition of water to a liquid-like L_α phase. The signature of the L_α,g regime in these systems is a dramatic increase in layer-dislocation defects, stabilized by aggregation of the PEG-surfactants to the high curvature defect regions. These regions connect and "entangle" the membranes, causing gelation. A simple model describing these phenomena is that the inclusion of the polymer-surfactants in lamellar membranes softens the free energy of high curvature line-defects, leading to proliferation and gelation.

Theory of DNA electrophoresis in physical gels and entangled polymer solutions

NASA Astrophysics Data System (ADS)

Duke, Thomas; Viovy, Jean Louis

1994-03-01

A scaling theory is presented for the electrophoretic mobility of DNA in sieving media that form dynamically evolving meshworks, such as physical gels and solutions of entangled polymers. In such media, the topological constraints on the DNA's motion are perpetually changing as cross links break and rejoin or as the polymers diffuse. It is shown that if the rate of constraint release falls within a certain range (which depends on the field strength), fractionation can be extended to higher molecular weights than would be feasible using a permanent gel of equivalent pore size. This improvement is a consequence of the disruptive effect that constraint release has on the mechanism of molecular orientation. Numerical simulations support the predictions of the theory. The possibility of realizing such a system in practice, with the aim of improving on current electrophoresis methods, is commented upon. It is suggested that semidilute polymer solutions may be a versatile medium for the rapid separation of long single-stranded DNA molecules, and the particular quality of solution required is identified.

UCST-Type Thermoresponsive Polymers in Synthetic Lubricating Oil Polyalphaolefin (PAO)

DOE PAGES

Fu, Wenxin; Bai, Wei; Jiang, Sisi; ...

2018-02-20

Here, this article reports a family of UCST-type thermoresponsive polymers, poly(alkyl methacrylate)s with an appropriate alkyl pendant length, in an industrially important non-volatile organic liquid polyalphaolefin (PAO). The cloud point (CP) can be readily tuned over a wide temperature range by changing the alkyl pendant length; at a concentration of 1 wt% and similar polymer molecular weights, the CP varies linearly with the (average) number of carbon atoms in the alkyl pendant. PAO solutions of ABA triblock copolymers, composed of a PAO-philic middle block and thermoresponsive outer blocks with appropriate block lengths, undergo thermoreversible sol-gel transitions at sufficiently high concentrations.more » The discovery of thermoresponsive polymers in PAO makes it possible to explore new applications by utilizing PAO’s unique characteristics such as thermal stability, non-volatility, superior lubrication properties, etc. Lastly, two examples are presented: thermoresponsive physical gels for control of optical transmittance and injectable gel lubricants.« less

UCST-Type Thermoresponsive Polymers in Synthetic Lubricating Oil Polyalphaolefin (PAO)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Wenxin; Bai, Wei; Jiang, Sisi

Here, this article reports a family of UCST-type thermoresponsive polymers, poly(alkyl methacrylate)s with an appropriate alkyl pendant length, in an industrially important non-volatile organic liquid polyalphaolefin (PAO). The cloud point (CP) can be readily tuned over a wide temperature range by changing the alkyl pendant length; at a concentration of 1 wt% and similar polymer molecular weights, the CP varies linearly with the (average) number of carbon atoms in the alkyl pendant. PAO solutions of ABA triblock copolymers, composed of a PAO-philic middle block and thermoresponsive outer blocks with appropriate block lengths, undergo thermoreversible sol-gel transitions at sufficiently high concentrations.more » The discovery of thermoresponsive polymers in PAO makes it possible to explore new applications by utilizing PAO’s unique characteristics such as thermal stability, non-volatility, superior lubrication properties, etc. Lastly, two examples are presented: thermoresponsive physical gels for control of optical transmittance and injectable gel lubricants.« less

Radiation preparation of drug carriers based polyacrylic acid (PAAc) using poly(vinyl pyrrolidone) (PVP) as a template polymer

NASA Astrophysics Data System (ADS)

Abd El-Rehim, H. A.; Hegazy, E. A.; Khalil, F. H.; Hamed, N. A.

2007-01-01

The present study deals with the radiation synthesis of stimuli response hydrophilic polymers from polyacrylic acid (PAAc). To maintain the property of PAAc and control the water swellibility for its application as a drug delivery system, radiation polymerization of AAc in the presence of poly(vinyl pyrrolidone) (PVP) as a template polymer was carried out. Characterization of the prepared PAA/PVP inter-polymer complex was investigated by determining gel content, swelling property, hydrogel microstructure and the release rate of caffeine as a model drug. The release rate of caffeine from the PAA/PVP inter-polymer complexes showed pH-dependency, and seemed to be mainly controlled by the dissolution rate of the complex above a p Ka of PAAc. The prepared inter-polymer complex could be used for application as drug carriers.

Radiation dose enhancement of gold nanoparticle on different polymer gel dosimeters

NASA Astrophysics Data System (ADS)

Jabaseelan Samuel, E. James; Srinivasan, K.; Poopathi, V.

2017-05-01

In this work, we evaluated the dose enhancement produced by gold nanoparticle on ten different polymer gel dosimeters with a concentration of 7mgAu /g over a wide photon energy range of 15KeV to 20MeV and the results were compared with Soft tissue ICRU-44 produced. Our result showed that maximum DEF was observed at 40KeV, while it was almost negligible at higher energy range. Dose enhancement produced by AuNP on the gel dosimeter medium was varied compared to the reference ICRU-44 tissue, it was ± <1% for PAGAT, NIPAM, nPAG and ± <5% for PABIG, VIPAR, HEAG, BANG1, nMAG & ± <10% for MAGIC, ABAGIC gel dosimeters. Hence, we conclude that choosing the proper gel dosimeter is essential in dose enhancement study.

Advanced Polymer Network Structures

DTIC Science & Technology

2016-02-01

double networks in a single step was identified from coarse-grained molecular dynamics simulations of polymer solvents bearing rigid side chains dissolved...in a polymer network. Coarse-grained molecular dynamics simulations also explored the mechanical behavior of traditional double networks and...DRI), polymer networks, polymer gels, molecular dynamics simulations , double networks 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

Ethanol-assisted gel chromatography for single-chirality separation of carbon nanotubes

NASA Astrophysics Data System (ADS)

Zeng, Xiang; Hu, Jinwen; Zhang, Xiao; Zhou, Naigen; Zhou, Weiya; Liu, Huaping; Xie, Sishen

2015-10-01

Surfactants or polymers are usually used for the liquid processing of carbon nanotubes for their structure separation. However, they are difficult to remove after separation, affecting the intrinsic properties and applications of the separated species. Here, we report an ethanol-assisted gel chromatography for the chirality separation of single-walled carbon nanotubes (SWCNTs), in which ethanol is employed to finely tune the density/coverage of sodium dodecyl sulfate (SDS) on nanotubes, and thus the interactions between SWCNTs and an allyl dextran-based gel. Incrementally increasing the ethanol content in a low-concentration SDS eluent leads to successive desorption of the different structure SWCNTs adsorbed on the gel, and to achieve multiple distinct (n, m) single-chirality species. The use of ethanol enables the working concentration of SDS to be reduced dramatically and also avoids the introduction of other surfactants or chemical reagents. More importantly, ethanol can be easily removed after separation. The ability of ethanol to tune the interactions between SWCNTs and the gel also gives a deeper insight into the separation mechanism of SWCNTs using gel chromatography.Surfactants or polymers are usually used for the liquid processing of carbon nanotubes for their structure separation. However, they are difficult to remove after separation, affecting the intrinsic properties and applications of the separated species. Here, we report an ethanol-assisted gel chromatography for the chirality separation of single-walled carbon nanotubes (SWCNTs), in which ethanol is employed to finely tune the density/coverage of sodium dodecyl sulfate (SDS) on nanotubes, and thus the interactions between SWCNTs and an allyl dextran-based gel. Incrementally increasing the ethanol content in a low-concentration SDS eluent leads to successive desorption of the different structure SWCNTs adsorbed on the gel, and to achieve multiple distinct (n, m) single-chirality species. The use of ethanol enables the working concentration of SDS to be reduced dramatically and also avoids the introduction of other surfactants or chemical reagents. More importantly, ethanol can be easily removed after separation. The ability of ethanol to tune the interactions between SWCNTs and the gel also gives a deeper insight into the separation mechanism of SWCNTs using gel chromatography. Electronic supplementary information (ESI) available: Fig. S1-S13, additional discussion and experimental details. See DOI: 10.1039/c5nr04116c

Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

NASA Astrophysics Data System (ADS)

Abd El-Rehim, H. A.

2005-10-01

Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers.

Synthesis, properties, and biomedical applications of gelatin methacryloyl (GelMA) hydrogels

PubMed Central

Yue, Kan; Santiago, Grissel Trujillo-de; Alvarez, Mario Moisés; Tamayol, Ali; Annabi, Nasim; Khademhosseini, Ali

2015-01-01

Gelatin methacryloyl (GelMA) hydrogels have been widely used for various biomedical applications due to their suitable biological properties and tunable physical characteristics. Three dimensional (3D) GelMA hydrogels closely resemble some essential properties of native extracellular matrix (ECM) due to the presence of cell-attaching and matrix metalloproteinase responsive peptide motifs, which allow cells to proliferate and spread in GelMA-based scaffolds. GelMA is also versatile from a processing perspective. It crosslinks when exposed to light irradiation to form hydrogels with tunable mechanical properties which mimic the native ECM. It can also be microfabricated using different methodologies including micromolding, photomasking, bioprinting, self-assembly, and microfluidic techniques to generate constructs with controlled architectures. Hybrid hydrogel systems can also be formed by mixing GelMA with nanoparticles such as carbon nanotubes and graphene oxide, and other polymers to form networks with desired combined properties and characteristics for specific biological applications. Recent research has demonstrated the proficiency of GelMA-based hydrogels in a wide range of applications including engineering of bone, cartilage, cardiac, and vascular tissues, among others. Other applications of GelMA hydrogels, besides tissue engineering, include fundamental single-single cell research, cell signaling, drug and gene delivery, and bio-sensing. PMID:26414409

Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications

DOE PAGES

Zhao, Fei; Shi, Ye; Pan, Lijia; ...

2017-06-26

Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocksmore » into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. Our hope is that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.« less

Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Fei; Shi, Ye; Pan, Lijia

Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocksmore » into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. Our hope is that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.« less

Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications.

PubMed

Zhao, Fei; Shi, Ye; Pan, Lijia; Yu, Guihua

2017-07-18

Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocks into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. We hope that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.

Bistable electroactive polymers (BSEP): large-strain actuation of rigid polymers

NASA Astrophysics Data System (ADS)

Yu, Zhibin; Niu, Xiaofan; Brochu, Paul; Yuan, Wei; Li, Huafeng; Chen, Bin; Pei, Qibing

2010-04-01

Reversible, large-strain, bistable actuation has been a lasting puzzle in the pursuit of smart materials and structures. Conducting polymers are bistable, but the achievable strain is small. Large deformations have been achieved in dielectric elastomers at the expense of mechanical strength. The gel or gel-like soft polymers generally have elastic moduli around or less than 10 MPa. The deformed polymer relaxes to its original shape once the applied electric field is removed. We report new, bistable electroactive polymers (BSEP) that are capable of electrically actuated strains as high as 335% area strain. The BSEP could be useful for constructing rigid structures. The structures can support high mechanical loads, and be actuated to large-strain deformations. We will present one unique application of the BSEP for Braille displays that can be quickly refreshed and maintain the displayed contents without a bias voltage.

Electroencephalogram measurement using polymer-based dry microneedle electrode

NASA Astrophysics Data System (ADS)

Arai, Miyako; Nishinaka, Yuya; Miki, Norihisa

2015-06-01

In this paper, we report a successful electroencephalogram (EEG) measurement using polymer-based dry microneedle electrodes. The electrodes consist of needle-shaped substrates of SU-8, a silver film, and a nanoporous parylene protective film. Differently from conventional wet electrodes, microneedle electrodes do not require skin preparation and a conductive gel. SU-8 is superior as a structural material to poly(dimethylsiloxane) (PDMS; Dow Corning Toray Sylgard 184) in terms of hardness, which was used in our previous work, and facilitates the penetration of needles through the stratum corneum. SU-8 microneedles can be successfully inserted into the skin without breaking and could maintain a sufficiently low skin-electrode contact impedance for EEG measurement. The electrodes successfully measured EEG from the frontal pole, and the quality of acquired signals was verified to be as high as those obtained using commercially available wet electrodes without any skin preparation or a conductive gel. The electrodes are readily applicable to record brain activities for a long period with little stress involved in skin preparation to the users.

Creating Reconfigurable Materials Using ``Colonies'' of Oscillating Polymer Gels

NASA Astrophysics Data System (ADS)

Deb, Debabrata; Dayal, Pratyush; Kuksenok, Olga; Balazs, Anna

2013-03-01

Species ranging from single-cell organisms to social insects can undergo auto-chemotaxis, where the entities move towards a chemo-attractant that they themselves emit. This mode of signaling allows the organisms to form large-scale structures. Using computational modeling, we show that millimeter-sized polymer gels can display similar auto-chemotaxis. In particular, we demonstrate that gels undergoing the self-oscillating Belousov-Zhabotinsky (BZ) reaction not only respond to a chemical signal from the surrounding solution, but also emit this signal and thus, multiple gel pieces can spontaneously self-aggregate. We focus on the collective behavior of ``colonies'' of BZ gels and show that communication between the individual pieces critically depends on all the neighboring gels. We isolate the conditions at which the BZ gels can undergo a type of self-recombining: if a larger gel is cut into distinct pieces that are moved relatively far apart, then their auto-chemotactic behavior drives them to move and autonomously recombine into a structure resembling the original, uncut sample. These findings reveal that the BZ gels can be used as autonomously moving building blocks to construct multiple structures and thus, provide a new route for creating dynamically reconfigurable materials.

Effects of HPMC substituent pattern on water up-take, polymer and drug release: An experimental and modelling study.

PubMed

Caccavo, Diego; Lamberti, Gaetano; Barba, Anna Angela; Abrahmsén-Alami, Susanna; Viridén, Anna; Larsson, Anette

2017-08-07

The purpose of this study was to investigate the hydration behavior of two matrix formulations containing the cellulose derivative hydroxypropyl methylcellulose (HPMC). The two HPMC batches investigated had different substitution pattern along the backbone; the first one is referred to as heterogeneous and the second as homogenous. The release of both the drug molecule theophylline and the polymer was determined. Additionally, the water concentrations at different positions in the swollen gel layers were determined by Magnetic Resonance Imaging. The experimental data was compared to predicted values obtained by the extension of a mechanistic Fickian based model. The hydration of tablets containing the more homogenous HPMC batch showed a gradual water concentration gradient in the gel layer and could be well predicted. The hydration process for the more heterogeneous batch showed a very abrupt step change in the water concentration in the gel layer and could not be well predicted. Based on the comparison between the experimental and predicted data this study suggests, for the first time, that formulations with HPMC of different heterogeneities form gels in different ways. The homogeneous HPMC batch exhibits a water sorption behavior ascribable to a Ficḱs law for the diffusion process whereas the more heterogeneous HPMC batches does not. This conclusion is important in the future development of simulation models and in the understanding of drug release mechanism from hydrophilic matrices. Copyright © 2017 Elsevier B.V. All rights reserved.

Equilibrium polymerization of cyclic carbonate oligomers. III. Chain branching and the gel transition

NASA Astrophysics Data System (ADS)

Ballone, P.; Jones, R. O.

2002-10-01

Ring-opening polymerization of cyclic polycarbonate oligomers, where monofunctional active sites act on difunctional monomers to produce an equilibrium distribution of rings and chains, leads to a "living polymer." Monte Carlo simulations [two-dimensional (2D) and three-dimensional (3D)] of the effects of single [J. Chem. Phys. 115, 3895 (2001)] and multiple active sites [J. Chem. Phys. 116, 7724 (2002)] are extended here to trifunctional active sites that lead to branching. Low concentrations of trifunctional particles c3 reduce the degree of polymerization significantly in 2D, and higher concentrations (up to 32%) lead to further large changes in the phase diagram. Gel formation is observed at high total density and sizable c3 as a continuous transition similar to percolation. Polymer and gel are much more stable in 3D than in 2D, and both the total density and the value of c3 required to produce high molecular weight aggregates are reduced significantly. The degree of polymerization in high-density 3D systems is increased by the addition of trifunctional monomers and reduced slightly at low densities and low c3. The presence of branching makes equilibrium states more sensitive (in 2D and 3D) to changes in temperature T. The stabilities of polymer and gel are enhanced by increasing T, and—for sufficiently high values of c3—there is a reversible polymer-gel transformation at a density-dependent floor temperature.

Emerging Nanotechnology-based Corrosion Control Coatings

DTIC Science & Technology

2009-02-01

Posdorfer, J., Synth. Met., 102, 1400-1401, 1999. • Fluoro- and silicon/silicone modified polymers • Organic- inorganic hybrid polymers Hopkins, A, The...O O S u b s t ra te Hybrid Organic- Inorganic Sol-gel Coating Bis-Ureasil HN NH O HN NH O Si MeO OMe MeO Si OMe OMe OMeR C2H5O Si OC2H5 OC2H5 OC2H5...Cycloaliphatic Amine 35% 65% 100% Nanotechnology-based coatings Ce+3Ce+3 Δ, H2O, OH - ΔEnviron > Tm =40 oC + Corrosion resistant Hybrid Organic- Inorganic

Microwave-assisted synthesis and micellization behavior of soy-based copoly(2-oxazoline)s.

PubMed

Hoogenboom, Richard; Leenen, Mark A M; Huang, Haiying; Fustin, Charles-André; Gohy, Jean-François; Schubert, Ulrich S

2006-01-01

Polymers based on renewable resources are promising candidates for replacing common organic polymers, and thus, for reducing oil consumption. In this contribution we report the microwave-assisted synthesis of block and statistical copolymers from 2-ethyl-2-oxazoline and 2-"soy alkyl"-2-oxazoline via a cationic ring-opening polymerization mechanism. The synthesized copolymers were characterized by gel permeation chromatography and 1 H-NMR spectroscopy. The micellization of these amphiphilic copolymers was investigated by dynamic light scattering and atomic force microscopy to examine the effect of hydrophobic block length and monomer distribution on the resulting micellar characteristics.

Preconcentration and Determination of Mefenamic Acid in Pharmaceutical and Biological Fluid Samples by Polymer-grafted Silica Gel Solid-phase Extraction Following High Performance Liquid Chromatography

PubMed Central

Bagheri Sadeghi, Hayedeh; Panahi, Homayon Ahmad; Mahabadi, Mahsa; Moniri, Elham

2015-01-01

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-infammatory and antipyretic actions. It is used to relieve mild to moderate pains. Solid-phase extraction of mefenamic acid by a polymer grafted to silica gel is reported. Poly allyl glycidyl ether/iminodiacetic acid-co-N, N-dimethylacrylamide was synthesized and grafted to silica gel and was used as an adsorbent for extraction of trace mefenamic acid in pharmaceutical and biological samples. Different factors affecting the extraction method were investigated and optimum conditions were obtained. The optimum pH value for sorption of mefenamic acid was 4.0. The sorption capacity of grafted adsorbent was 7.0 mg/g. The best eluent solvent was found to be trifluoroacetic acid-acetic acid in methanol with a recovery of 99.6%. The equilibrium adsorption data of mefenamic acid by grafted silica gel was analyzed by Langmuir model. The conformation of obtained data to Langmuir isotherm model reveals the homogeneous binding sites of grafted silica gel surface. Kinetic study of the mefenamic acid sorption by grafted silica gel indicates the good accessibility of the active sites in the grafted polymer. The sorption rate of the investigated mefenamic acid on the grafted silica gel was less than 5 min. This novel synthesized adsorbent can be successfully applied for the extraction of trace mefenamic acid in human plasma, urine and pharmaceutical samples. PMID:26330865

The use of normoxic polymer gel for measuring dose distributions of 1, 4 and 30 mm cones

NASA Astrophysics Data System (ADS)

Lee, C. C.; Wu, J. F.; Chang, K. P.; Chu, C. H.; Wey, S. P.; Liu, H. L.; Tung, C. J.; Wu, S. W.; Chao, T. C.

2014-11-01

This study demonstrates the use of normoxic polymer gel for measuring dose distributions of small fields that lack lateral electronic equilibrium. Two different types of normoxic polymer gel, MAGAT and PAGAT, are studied in a larger field (10 cm×10 cm) and 1, 4 and 30 mm cones to obtain cone factors, dose profiles and percentage depth doses. These results were then compared to KODAK XV film measurements and BEAMnrc Monte Carlo simulations. The results show that the sensitivity of PAGAT gel is 0.090±0.074 s-1 Gy-1, which may not be suitable for small-field dosimetry with a 0.3 mm resolution scanned using a 3 T MR imager in a dose range lower than 2.5 Gy. There are good agreements between cone factors estimated using KODAK XV film and MAGAT gel. In a dose profile comparison, good dose agreement among MAGAT gel, XV film and MC simulation can be seen in the central area for a 30 mm cone. In penumbra, the distance to agreement is at most 1.2 mm (4 pixel), and less than 0.3 mm (1 pixel) for 4 and 1 mm cones. In a percentage depth dose comparison, there were good agreements between MAGAT and MC up to a depth of 8 cm. Possible factors for gel uncertainty such as MRI magnetic field inhomogeneity and temperature were also investigated.

Design and Construction of an Optical Computed Tomography Scanner for Polymer Gel Dosimetry Application

PubMed Central

Zakariaee, Seyed Salman; Mesbahi, Asghar; Keshtkar, Ahmad; Azimirad, Vahid

2014-01-01

Polymer gel dosimeter is the only accurate three dimensional (3D) dosimeter that can measure the absorbed dose distribution in a perfect 3D setting. Gel dosimetry by using optical computed tomography (OCT) has been promoted by several researches. In the current study, we designed and constructed a prototype OCT system for gel dosimetry. First, the electrical system for optical scanning of the gel container using a Helium-Neon laser and a photocell was designed and constructed. Then, the mechanical part for two rotational and translational motions was designed and step motors were assembled to it. The data coming from photocell was grabbed by the home-built interface and sent to a personal computer. Data processing was carried out using MATLAB software. To calibrate the system and tune up the functionality of it, different objects was designed and scanned. Furthermore, the spatial and contrast resolution of the system was determined. The system was able to scan the gel dosimeter container with a diameter up to 11 cm inside the water phantom. The standard deviation of the pixels within water flask image was considered as the criteria for image uniformity. The uniformity of the system was about ±0.05%. The spatial resolution of the system was approximately 1 mm and contrast resolution was about 0.2%. Our primary results showed that this system is able to obtain two-dimensional, cross-sectional images from polymer gel samples. PMID:24761377

Stability Improvements of DNA Photonic Devices

DTIC Science & Technology

2008-12-20

possible in such areas as photonics, separation process or biomedical materials . Recent research results on DNA-lipid complexes have shown various...onto Teflon- coated glass plate to obtain films by irradiating UV light to cause crosslinking reactions of the Adeka sol-gel materials Clear and...into sol-gel materials or synthetic polymers so that water permeation is prevented by glass or synthetic polymers to stabilize and to keep the optical

Effects of swelling on the viscoelastic properties of polyester films made from glycerol and glutaric acid

USDA-ARS?s Scientific Manuscript database

Viscoelastic properties have been determined for poly(glycerol-co-glutaric acid) films synthesized from Lewis acid-catalyzed polyesterifications. The polymers were prepared by synthesizing polymer gels that were subsequently cured at 125 degrees C to form polymer films. The polymers were evaluated ...

Development of molecularly imprinted polymer-based field effect transistor for sugar chain sensing

NASA Astrophysics Data System (ADS)

Nishitani, Shoichi; Kajisa, Taira; Sakata, Toshiya

2017-04-01

In this study, we developed a molecularly imprinted polymer-based field-effect transistor (MIP-gate FET) for selectively detecting sugar chains in aqueous media, focusing on 3‧-sialyllactose (3SLac) and 6‧-sialyllactose (6SLac). The FET biosensor enables the detection of small molecules as long as they have intrinsic charges. Additionally, the MIP gels include the template for the target molecule, which is selectively trapped without requiring enzyme-target molecule reaction. The MIP gels were synthesized on the gate surface of the FET device, including phenylboronic acid (PBA), which enables binding to sugar chains. Firstly, the 3SLac-MIP-gate FET quantitatively detected 3SLac at µM levels. This is because the FET device recognized the change in molecular charges on the basis of PBA-3SLac binding in the MIP gel. Moreover, 3SLac was selectively detected using the 3SLac- and 6SLac-MIP-gate FETs to some extent, where the detecting signal from the competent was suppressed by 40% at maximum. Therefore, a platform based on the MIP-coupled FET biosensor is suitable for a selective biosensing system in an enzyme-free manner, which can be applied widely in medical fields. However, we need to further improve the selectivity of MIP-gate FETs to discriminate more clearly between similar structures of sugar chains such as 3SLac and 6SLac.

Safety assessment of thiolated polymers: effect on ciliary beat frequency in human nasal epithelial cells.

PubMed

Palmberger, Thomas F; Augustijns, Patrick; Vetter, Anja; Bernkop-Schnürch, Andreas

2011-12-01

The aim of this study was to investigate the nasal safety of gel formulations of thiolated polymers (thiomers) by assessing their effect on ciliary beat frequency (CBF) in human nasal epithelial cells. Poly(acrylic acid) 450 kDa-cysteine (PAA-cys) and alginate-cysteine (alg-cys) were synthesized by covalent attachment of L-cysteine to the polymeric backbone. The cationic polymer chitosan-thiobutylamidine (chito-TBA) was synthesized by attaching iminothiolane to chitosan. CBF using was measured by a photometric system. CBF was measured before incubating the cells with test gels, during incubation and after washing out the polymeric test gels to evaluate reversibility of cilio-inhibition. The influence of viscosity on CBF was determined by using hydroxyethylcellulose (HEC)-gels of various concentrations. Ciliary beating was observed to be affected by viscosity, but cilia were still beating in the presence of a HEC-gel displaying an apparent viscosity of 25 Pa.s. In case of thiolated polymers and their unmodified control, a concentration-dependent decrease in CBF could be observed. PAA-cys, alg-cys, chito-TBA and their corresponding unmodified controls exhibited a moderate cilio-inhibitory effect, followed by a partial recovery of CBF when used at a concentration of 1%. Alg-cys 2% and chito-TBA 2% (m/v) gels exhibited severe cilio-inhibition, which was partially reversible. L-cysteine and reduced glutathione led to mild cilio-inhibition at concentrations of 3% (m/v). Taking into account that dilution after application and cilio-modifying effects is usually more pronounced under in vitro conditions, thiomers can be considered as suitable excipients for nasal drug delivery systems.

Block copolymers for biomimetic composites

NASA Astrophysics Data System (ADS)

Calvert, Paul D.; Oner, Mualla; Burdon, Jeremy; Rieke, Peter C.; Farmer, Kelly

1993-07-01

Mineralized biological tissues can be regarded as composites where a fine reinforcement is laid down in a very controlled fashion within a tough polymeric matrix. Such materials include bone, antler, tooth enamel, mollusc shell, and crustacean shell. We have been exploring ways of forming similar structures by synthetic routes involving precipitation of reinforcing particles directly into a polymeric matrix. Part of this biomimetic approach requires polymer matrices which can exert a high degree of control over the mineralization process. Polymer gels have been formed from cross-linked methacrylates with various types of functionality within the gel. By incorporating calcium binding groups we have been producing gels which lead to preferential mineralization of the gel when it is incubated in a supersaturated solution of calcium oxalate or calcium carbonate. Similarly we have been incorporating silane groups within the gel in order to promote the deposition of silica in a gel body when it is immersed in a metastable solution of partly hydrolysed silicon alkoxides.

The actuation of a biomimetic poly(vinyl alcohol)poly(acrylic acid) gel.

PubMed

Marra, S P; Ramesh, K T; Douglas, A S

2002-02-15

Active polymer gels expand and contract in response to certain environmental stimuli, such as the application of an electric field or a change in the pH level of the surroundings. This ability to achieve large, reversible deformations with no external mechanical loading has generated much interest in the use of these gels as biomimetic actuators and "artificial muscles". In previous work, a thermodynamically consistent finite-elastic constitutive model has been developed to describe the mechanical and actuation behaviours of active polymer gels. The mechanical properties were characterized by a free-energy function, and the model uses an evolving internal variable to describe the actuation state. In this work, an evolution law for the internal variable is determined from free actuation experiments on a poly(vinyl alcohol)poly(acrylic acid) (PVAPAA) gel. The complete finite-elastic/evolution law constitutive model is then used to predict the response of the PVA-PAA gel to isotonic and isometric loading and actuation. The model is shown to give relatively good agreement with experimental results.

Rheological Enhancement of Pork Myofibrillar Protein-Lipid Emulsion Composite Gels via Glucose Oxidase Oxidation/Transglutaminase Cross-Linking Pathway.

PubMed

Wang, Xu; Xiong, Youling L; Sato, Hiroaki

2017-09-27

Porcine myofibrillar protein (MP) was modified with glucose oxidase (GluOx)-iron that produces hydroxyl radicals then subjected to microbial transglutaminase (TGase) cross-linking in 0.6 M NaCl at 4 °C. The resulting aggregation and gel formation of MP were examined. The GluOx-mediated oxidation promoted the formation of both soluble and insoluble protein aggregates via disulfide bonds and occlusions of hydrophobic groups. The subsequent TGase treatment converted protein aggregates into highly cross-linked polymers. MP-lipid emulsion composite gels formed with such polymers exhibited markedly enhanced gelling capacity: up to 4.4-fold increases in gel firmness and 3.5-fold increases in gel elasticity over nontreated protein. Microstructural examination showed small oil droplets dispersed in a densely packed gel matrix when MP was oxidatively modified, and the TGase treatment further contributed to such packing. The enzymatic GluOx oxidation/TGase treatment shows promise to improve the textural properties of emulsified meat products.

Formulation and evaluation of Alendronate Sodium gel for the treatment of bone resorptive lesions in Periodontitis.

PubMed

Reddy, G Thirumal; Kumar, T M Pramod; Veena

2005-01-01

Alendronate sodium is formulated into gels and evaluated for the treatment of bone resorptive lesions in periodontitis. Carbopol 934P was used for the preparation of gels in three different concentrations. The prepared gel was evaluated for various properties such as preformulation, content uniformity, viscosity, compatibility, sterility, in vitro diffusion, and in vivo studies. The drug and the polymer were found to be compatible and confirmed by Fourier transform infrared spectroscopy. Viscosity of the gels increased with the increase in the polymer concentration. The formulations were found to be sterile. In vitro release study revealed that drug released from the gel follows non-Fickian diffusion followed by first-order release. In vivo studies were carried out for 6 months in patients. The results revealed a significant improvement in the clinical parameters such as gingival index, probing pocket depth, clinical attachment level, and potent inhibitory effect on bone resorption by inhibition of osteoclasts. In addition, there was increase in the new bone formation.

Non-volatile copolymer compositions for fabricating gel element microarrays

PubMed Central

Golova, Julia B.; Chernov, Boris K.; Perov, Alexander N.; Reynolds, Jennifer; Linger, Yvonne L.; Kukhtin, Alexander; Chandler, Darrell P.

2011-01-01

By modifying polymer compositions and cross-linking reagents, we have developed a simple yet effective manufacturing strategy for copolymerized three-dimensional gel element arrays. A new gel-forming monomer (2-(hydroxyethyl) methacrylamide; HEMAA) was used that possesses low volatility and improves the stability of copolymerized gel element arrays to on-chip thermal cycling procedures relative to previously used monomers. Probe immobilization efficiency within the new polymer was 55%, equivalent to that obtained with acrylamide (AA) and methacrylamide (MA) monomers. Non-specific binding of single stranded targets was equivalent for all monomers. Increasing cross-linker chain length improved hybridization kinetics and end-point signal intensities relative to N,N-methylenebisacrylamide (Bis). The new copolymer formulation was successfully applied to a model orthopox array. Because HEMAA greatly simplifies gel element array manufacture, we expect it (in combination with new cross-linkers described herein) to find widespread application in microarray science. PMID:22033291

Thiol Modification of Psyllium Husk Mucilage and Evaluation of Its Mucoadhesive Applications

PubMed Central

Bhatia, Meenakshi

2013-01-01

Thiol functionalization of psyllium was carried out to enhance its mucoadhesive potential. Thiolation of psyllium was achieved by esterification with thioglycolic acid. Thiolation was observed to change the surface morphology of psyllium from fibrous to granular and result in a slight increase in the crystallinity and swelling. Thiolated psyllium was found to contain 3.282 m moles of thiol groups/g of the polymer. Mucoadhesive applications of thiolated psylium were explored by formulating gels using metronidazole as the model drug. On comparative evaluation thiolated psyllium gels showed 3-fold higher mucoadhesive strength than the psyllium gels as determined by modified physical balance using chicken buccal pouch. The results of in vitro release study revealed that thiolated psyllium gels provided a prolonged release of metronidazole. Further, the psyllium and thiolated psyllium gels were found to release the drug following first-order kinetics by combination of polymer relaxation and diffusion through the matrix. PMID:24348147

Thermo-responsive gels that absorb moisture and ooze water.

PubMed

Matsumoto, Kazuya; Sakikawa, Nobuki; Miyata, Takashi

2018-06-13

The water content of thermo-responsive hydrogels can be drastically altered by small changes in temperature because their polymer chains change from hydrophilic to hydrophobic above their low critical solution temperature (LCST). In general, such smart hydrogels have been utilized in aqueous solutions or in their wet state, and no attempt has been made to determine the phase-transition behavior of the gels in their dried states. Here we demonstrate an application of the thermo-responsive behavior of an interpenetrating polymer network (IPN) gel comprising thermo-responsive poly(N-isopropylacrylamide) and hydrophilic sodium alginate networks in their dried states. The dried IPN gel absorbs considerable moisture from air at temperatures below its LCST and oozes the absorbed moisture as liquid water above its LCST. These phenomena provide energy exchange systems in which moisture from air can be condensed to liquid water using the controllable hydrophilic/hydrophobic properties of thermo-responsive gels with a small temperature change.

Surface friction of hydrogels with well-defined polyelectrolyte brushes.

PubMed

Ohsedo, Yutaka; Takashina, Rikiya; Gong, Jian Ping; Osada, Yoshihito

2004-08-03

Hydrogels of poly(2-hydroxyethyl methacrylate) (PHEMA) with well-defined polyelectrolyte brushes of poly(sodium 4-styrenesulfonate) (PNaSS) of various molecular weights were synthesized, keeping the distance between the polymer brushes constant at ca. 20 nm. The effect of polyelectrolyte brush length on the sliding friction against a glass plate, an electrorepulsive solid substrate, was investigated in water in a velocity range of 7.5 x 10(-5) to 7.5 x 10(-2) m/s. It is found that the presence of polymer brush can dramatically reduce the friction when the polymer brushes are short. With an increase in the length of the polymer brush, this drag reduction effect only works at a low sliding velocity, and the gel with long polymer brushes even shows a higher friction than that of a normal network gel at a high sliding velocity. The strong polymer length and sliding velocity dependence indicate a dynamic mechanism of the polymer brush effect.

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography.

PubMed

Shih, Tian-Yu; Wu, Jay; Shih, Cheng-Ting; Lee, Yao-Ting; Wu, Shin-Hua; Yao, Chun-Hsu; Hsieh, Bor-Tsung

2016-01-01

With advances in therapeutic instruments and techniques, three-dimensional dose delivery has been widely used in radiotherapy. The verification of dose distribution in a small field becomes critical because of the obvious dose gradient within the field. The study investigates the dose distributions of various field sizes by using NIPAM polymer gel dosimeter. The dosimeter consists of 5% gelatin, 5% monomers, 3% cross linkers, and 5 mM THPC. After irradiation, a 24 to 96 hour delay was applied, and the gel dosimeters were read by a cone beam optical computed tomography (optical CT) scanner. The dose distributions measured by the NIPAM gel dosimeter were compared to the outputs of the treatment planning system using gamma evaluation. For the criteria of 3%/3 mm, the pass rates for 5 × 5, 3 × 3, 2 × 2, 1 × 1, and 0.5 × 0.5 cm2 were as high as 91.7%, 90.7%, 88.2%, 74.8%, and 37.3%, respectively. For the criteria of 5%/5 mm, the gamma pass rates of the 5 × 5, 3 × 3, and 2 × 2 cm2 fields were over 99%. The NIPAM gel dosimeter provides high chemical stability. With cone-beam optical CT readouts, the NIPAM polymer gel dosimeter has potential for clinical dose verification of small-field irradiation.

Preparation and adsorption behavior of berberine hydrochloride imprinted polymers by using silica gel as sacrificed support material

NASA Astrophysics Data System (ADS)

Li, Hui; Li, Yuzhuo; Li, Zhiping; Peng, Xiyang; Li, Yanan; Li, Gui; Tan, Xianzhou; Chen, Gongxi

2012-03-01

Preparation of berberine hydrochloride (B-Cl) imprinted polymers (MIPs) based on surface imprinting technique with silica gel as sacrificial support material was performed successfully by using B-Cl as template, methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and cross-linker, respectively. The prepared polymers were characterized by Fourier transmission infrared spectrometry (FTIR) and scanning electron microscopy (SEM). Adsorption behavior of the MIPs for the template and its structural analogues was investigated. Sites distribution on the surface of MIPs was explored by using different isotherm adsorption models and thermodynamic parameters for the adsorption of B-Cl on the MIPs determined. Sample application and reusability for the MIPs was also evaluated. Results indicated the strong adsorption and high selectivity of the MIPs for B-Cl. Saturated adsorption capacity reached 27.2 μmol g-1 and the selectivity coefficient of the MIPs for B-Cl relative to jatrorrhizine hydrochloride (J-Cl) and palmatine palmatus hydrochloride (P-Cl) are 3.70 and 6.03, respectively. In addition, the MIPs were shown with good reusability and selectively retention ability in sample application.

Integration of motor proteins - towards an ATP fueled soft actuator.

PubMed

Kakugo, Akira; Shikinaka, Kazuhiro; Gong, Jian Ping

2008-09-01

We present a soft bio-machine constructed from biological motors (actin/myosin). We have found that chemically cross-linked polymer-actin complex gel filaments can move on myosin coated surfaces with a velocity as high as that of native F-actin, by coupling to ATP hydrolysis. Additionally, it is shown that the velocity of polymer-actin complex gel depends on the species of polycations binding to the F-actins. Since the design of functional actuators of well-defined size and morphology is important, the structural behavior of polymer-actin complexes has been investigated. Our results show that the morphology and growth size of polymer-actin complex can be controlled by changes in the electrostatic interactions between F-actins and polycations. Our results indicate that bio actuators with desired shapes can be created by using a polymer-actin complex.

Heat- and light-induced thiol-ene oligomerization of soybean oil-based polymercaptan

USDA-ARS?s Scientific Manuscript database

Polymercaptanized soybean oil (PMSO), the product of a thiol-ene reaction between soybean oil and hydrogen sulfide, is a material of interest as a lubricant additive and polymer precursor. We investigated with gel permeation chromatography, nuclear magnetic resonance (one-dimensional and two-dimensi...

Method for the preparation of high surface area high permeability carbons

DOEpatents

Lagasse, Robert R.; Schroeder, John L.

1999-05-11

A method for preparing carbon materials having high surface area and high macropore volume to provide high permeability. These carbon materials are prepared by dissolving a carbonizable polymer precursor, in a solvent. The solution is cooled to form a gel. The solvent is extracted from the gel by employing a non-solvent for the polymer. The non-solvent is removed by critical point drying in CO.sub.2 at an elevated pressure and temperature or evaporation in a vacuum oven. The dried product is heated in an inert atmosphere in a first heating step to a first temperature and maintained there for a time sufficient to substantially cross-link the polymer material. The cross-linked polymer material is then carbonized in an inert atmosphere.

Ionic Liquid-Doped Gel Polymer Electrolyte for Flexible Lithium-Ion Polymer Batteries

PubMed Central

Zhang, Ruisi; Chen, Yuanfen; Montazami, Reza

2015-01-01

Application of gel polymer electrolytes (GPE) in lithium-ion polymer batteries can address many shortcomings associated with liquid electrolyte lithium-ion batteries. Due to their physical structure, GPEs exhibit lower ion conductivity compared to their liquid counterparts. In this work, we have investigated and report improved ion conductivity in GPEs doped with ionic liquid. Samples containing ionic liquid at a variety of volume percentages (vol %) were characterized for their electrochemical and ionic properties. It is concluded that excess ionic liquid can damage internal structure of the batteries and result in unwanted electrochemical reactions; however, samples containing 40–50 vol % ionic liquid exhibit superior ionic properties and lower internal resistance compared to those containing less or more ionic liquids.

Self-Consistent Field Lattice Model for Polymer Networks.

PubMed

Tito, Nicholas B; Storm, Cornelis; Ellenbroek, Wouter G

2017-12-26

A lattice model based on polymer self-consistent field theory is developed to predict the equilibrium statistics of arbitrary polymer networks. For a given network topology, our approach uses moment propagators on a lattice to self-consistently construct the ensemble of polymer conformations and cross-link spatial probability distributions. Remarkably, the calculation can be performed "in the dark", without any prior knowledge on preferred chain conformations or cross-link positions. Numerical results from the model for a test network exhibit close agreement with molecular dynamics simulations, including when the network is strongly sheared. Our model captures nonaffine deformation, mean-field monomer interactions, cross-link fluctuations, and finite extensibility of chains, yielding predictions that differ markedly from classical rubber elasticity theory for polymer networks. By examining polymer networks with different degrees of interconnectivity, we gain insight into cross-link entropy, an important quantity in the macroscopic behavior of gels and self-healing materials as they are deformed.

Development of New Supramolecular Lyotropic Liquid Crystals and Their Application as Alignment Media for Organic Compounds.

PubMed

Leyendecker, Martin; Meyer, Nils-Christopher; Thiele, Christina M

2017-09-11

Most alignment media for the residual dipolar coupling (RDC) based molecular structure determination of small organic compounds consist of rod-like polymers dissolved in organic solvents or of swollen cross-linked polymer gels. Thus far, the synthesis of polymer-based alignment media has been a challenging process, which is often followed by a time-consuming sample preparation. We herein propose the use of non-polymeric alignment media based on benzenetricarboxamides (BTAs), which self-assemble into rod-like supramolecules. Our newly found supramolecular lyotropic liquid crystals (LLCs) are studied in terms of their LLC properties and their suitability as alignment media in NMR spectroscopy. Scalable enantiodifferentiating properties are introduced through a sergeant-and-soldier principle by blending achiral with chiral substituted BTAs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of pH on the rheological properties of borate crosslinked hydroxypropyl guar gum hydrogel and hydroxypropyl guar gum.

PubMed

Wang, Shibin; Tang, Hongbiao; Guo, Jianchun; Wang, Kunjie

2016-08-20

pH is an important factor affecting the performance of polymer fluid. The rheological properties of hydroxypropyl guar gum (HPG) base fluid and the structural strength, rheological properties, viscoelastic properties and thixotropy properties of HPG gel depend largely on the pH values. For the base fluid, an apparent viscosity-increasing effect was observed over the pH range from 7 to 11, and the apparent viscosity gradually decreased at pH 11.5-14, exhibiting electrostatic repulsion behavior and steric effects. For the HPG gel, at pH 7-12.5, the gel possessed higher apparent viscosity, higher elastic modulus (G'), lower tanδ (the ratio of the viscous modulus to the elastic modulus) and an "8"-shaped hysteresis loop, indicating stronger gel structure strength and the elastic dominant property. At pH 13-13.5, the gel samples exhibited the transition from a pseudoplastic fluid to a Newtonian fluid, and their viscosity, elastic modulus decreased but tanδ increased with the increase in pH values, exhibiting gradually weakened elastic properties. When the pH was 14, the gel mainly exhibited viscous characteristics. Copyright © 2016 Elsevier Ltd. All rights reserved.

A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles

NASA Astrophysics Data System (ADS)

Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A.

2015-12-01

Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries.

A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles.

PubMed

Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A

2015-12-04

Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries.

A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles

PubMed Central

Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A.

2015-01-01

Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries. PMID:26634644

Auto-Origami and Soft Programmable Transformers: Simulation Studies of Liquid Crystal Elastomers and Swelling Polymer Gels

NASA Astrophysics Data System (ADS)

Konya, Andrew; Santangelo, Christian; Selinger, Robin

2014-03-01

When the underlying microstructure of an actuatable material varies in space, simple sheets can transform into complex shapes. Using nonlinear finite element elastodynamic simulations, we explore the design space of two such materials: liquid crystal elastomers and swelling polymer gels. Liquid crystal elastomers (LCE) undergo shape transformations induced by stimuli such as heating/cooling or illumination; complex deformations may be programmed by ``blueprinting'' a non-uniform director field in the sample when the polymer is cross-linked. Similarly, swellable gels can undergo shape change when they are swollen anisotropically as programmed by recently developed halftone gel lithography techniques. For each of these materials we design and test programmable motifs which give rise to complex deformation trajectories including folded structures, soft swimmers, apertures that open and close, bas relief patterns, and other shape transformations inspired by art and nature. In order to accommodate the large computational needs required to model these materials, our 3-d nonlinear finite element elastodynamics simulation algorithm is implemented in CUDA, running on a single GPU-enabled workstation.

Conductivity of gel polymer electrolytes doped with solutions of phosphonic acid or protic ionic liquids

NASA Astrophysics Data System (ADS)

Shmukler, Liudmila E.; Fadeeva, Yuliya A.; Glushenkova, Ekaterina V.; Nguyen, Van Thuc; Safonova, Liubov P.

2018-04-01

The proton-conducting gel electrolytes (PCGEs) based on PMMA, PVdF or PVdF-HFP doped with solutions of phosphonic acid or ammonium based protic ionic liquids (PILs) in DMF have been synthesized. Rather high values of the conductivity (10-4-10-3 S cm-1) have been reached at low dopant concentrations (up to 1 mol l-1). The influence of the nature of both polymeric matrix and dopant as well as dopant concentration on the conductivity values was discussed. It was established that the dependence of conductivity on the nature of dopant, but not the polymeric matrix, was more pronounced.

Measurement of residual chemical shift anisotropies in compressed polymethylmethacrylate gels. Automatic compensation of gel isotropic shift contribution.

PubMed

Hallwass, Fernando; Teles, Rubens R; Hellemann, Erich; Griesinger, Christian; Gil, Roberto R; Navarro-Vázquez, Armando

2018-05-01

Mechanical compression of polymer gels provides a simple way for the measurement of residual chemical shift anisotropies, which then can be employed, on its own, or in combination with residual dipolar couplings, for structural elucidation purposes. Residual chemical shift anisotropies measured using compression devices needed a posteriori correction to account for the increase of the polymer to solvent ratio inside the swollen gel. This correction has been cast before in terms of a single-free parameter which, as shown here, can be simultaneously optimized along with the components of the alignment tensor while still retaining discriminating power of the different relative configurations as illustrated in the stereochemical analysis of α-santonin and 10-epi-8-deoxycumambrin B. Copyright © 2018 John Wiley & Sons, Ltd.

Self-Healing Nanocomposite Hydrogel with Well-Controlled Dynamic Mechanics

NASA Astrophysics Data System (ADS)

Li, Qiaochu; Mishra, Sumeet; Chen, Pangkuan; Tracy, Joseph; Holten-Andersen, Niels

Network dynamics is a crucial factor that determines the macroscopic self-healing rate and efficiency in polymeric hydrogel materials, yet its controllability is seldom studied in most reported self-healing hydrogel systems. Inspired by mussel's adhesion chemistry, we developed a novel approach to assemble inorganic nanoparticles and catechol-decorated PEG polymer into a hydrogel network. When utilized as reversible polymer-particle crosslinks, catechol-metal coordination bonds yield a unique gel network with dynamic mechanics controlled directly by interfacial crosslink structure. Taking advantage of this structure-property relationship at polymer-particle interfaces, we next designed a hierarchically structured hybrid gel with two distinct relaxation timescales. By tuning the relative contribution of the two hierarchical relaxation modes, we are able to finely control the gel's dynamic mechanical behavior from a viscoelastic fluid to a stiff solid, yet preserving its fast self-healing property without the need for external stimuli.

Self-assembled hydrogels utilizing polymer-nanoparticle interactions

NASA Astrophysics Data System (ADS)

Appel, Eric A.; Tibbitt, Mark W.; Webber, Matthew J.; Mattix, Bradley A.; Veiseh, Omid; Langer, Robert

2015-02-01

Mouldable hydrogels that flow on applied stress and rapidly self-heal are increasingly utilized as they afford minimally invasive delivery and conformal application. Here we report a new paradigm for the fabrication of self-assembled hydrogels with shear-thinning and self-healing properties employing rationally engineered polymer-nanoparticle (NP) interactions. Biopolymer derivatives are linked together by selective adsorption to NPs. The transient and reversible interactions between biopolymers and NPs enable flow under applied shear stress, followed by rapid self-healing when the stress is relaxed. We develop a physical description of polymer-NP gel formation that is utilized to design biocompatible gels for drug delivery. Owing to the hierarchical structure of the gel, both hydrophilic and hydrophobic drugs can be entrapped and delivered with differential release profiles, both in vitro and in vivo. The work introduces a facile and generalizable class of mouldable hydrogels amenable to a range of biomedical and industrial applications.

Photoreversible Covalent Hydrogels for Soft-Matter Additive Manufacturing.

PubMed

Kabb, Christopher P; O'Bryan, Christopher S; Deng, Christopher C; Angelini, Thomas E; Sumerlin, Brent S

2018-05-16

Reversible covalent chemistry provides access to robust materials with the ability to be degraded and reformed upon exposure to an appropriate stimulus. Photoresponsive units are attractive for this purpose, as the spatial and temporal application of light is easily controlled. Coumarin derivatives undergo a [2 + 2] cycloaddition upon exposure to long-wave UV irradiation (365 nm), and this process can be reversed using short-wave UV light (254 nm). Therefore, polymers cross-linked by coumarin groups are excellent candidates as reversible covalent gels. In this work, copolymerization of coumarin-containing monomers with the hydrophilic comonomer N, N-dimethylacrylamide yielded water-soluble, linear polymers that could be cured with long-wave UV light into free-standing hydrogels, even in the absence of a photoinitiator. Importantly, the gels were reverted back to soluble copolymers upon short-wave UV irradiation. This process could be cycled, allowing for recycling and remolding of the hydrogel into additional shapes. Further, this hydrogel can be imprinted with patterns through a mask-based, post-gelation photoetching method. Traditional limitations of this technique, such as the requirement for uniform etching in one direction, have been overcome by combining these materials with a soft-matter additive manufacturing methodology. In a representative application of this approach, we printed solid structures in which the interior coumarin-cross-linked gel is surrounded by a nondegradable gel. Upon exposure to short-wave UV irradiation, the coumarin-cross-linked gel was reverted to soluble prepolymers that were washed away to yield hollow hydrogel objects.

A practical multilayered conducting polymer actuator with scalable work output

NASA Astrophysics Data System (ADS)

Ikushima, Kimiya; John, Stephen; Yokoyama, Kazuo; Nagamitsu, Sachio

2009-09-01

Household assistance robots are expected to become more prominent in the future and will require inherently safe design. Conducting polymer-based artificial muscle actuators are one potential option for achieving this safety, as they are flexible, lightweight and can be driven using low input voltages, unlike electromagnetic motors; however, practical implementation also requires a scalable structure and stability in air. In this paper we propose and practically implement a multilayer conducting polymer actuator which could achieve these targets using polypyrrole film and ionic liquid-soaked separators. The practical work density of a nine-layer multilayer actuator was 1.4 kJ m-3 at 0.5 Hz, when the volumes of the electrolyte and counter electrodes were included, which approaches the performance of mammalian muscle. To achieve air stability, we analyzed the effect of air-stable ionic liquid gels on actuator displacement using finite element simulation and it was found that the majority of strain could be retained when the elastic modulus of the gel was kept below 3 kPa. As a result of this work, we have shown that multilayered conducting polymer actuators are a feasible idea for household robotics, as they provide a substantial practical work density in a compact structure and can be easily scaled as required.

Experimental investigation of heat transfer characteristics of guar-based polymer solutions and gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azouz, I.; Vinod, P.S.; Shah, S.N.

1996-12-31

An experimental investigation of the heat transfer characteristics of hydraulic fracturing fluids was conducted at the Fracturing Fluid Characterization Facility (FFCF) of the University of Oklahoma. The facility is equipped with a high pressure fracture simulator, coiled tubing fluid pre-conditioning system, and a full-scale, counter-current, double pipe heat exchanger. The fluids investigated include non-crosslinked and borate-crosslinked guar gum and hydroxypropyl guar (HPG). Results were also obtained for water and were used as a basis for comparison. The effects of flow rate, operating temperature, pH, and various levels of shear pre-conditioning, on the heat transfer behavior of the test fluids weremore » investigated. Results show a significant difference between the heat transfer coefficient of the pure solvent (water) and those of the polymer solutions tested. While all polymer solutions tested exhibited lower heat transfer coefficients than that of the pure solvent, crosslinking appears to enhance the heat transfer characteristics of the polymer fluids. It was also observed that shear preconditioning does not seem to have a significant effect on the heat transfer coefficient of the crosslinked gels. These findings are of great interest to the industry, especially to the petroleum industry where these fluids are commonly used during hydraulic fracturing of hydrocarbon reservoirs.« less

Verification on the Dose Profile Variation of a 3-D—NIPAM Polymer Gel Dosimeter

NASA Astrophysics Data System (ADS)

Hsieh, Bor-Tsung; Wu, Jay; Chang, Yuan-Jen

2013-04-01

A gel dosimeter is a three-dimensional (3-D) device that is used in radiotherapy. It is more efficient than traditional one-dimensional and two-dimensional dosimeters because it can be used in complicated radiation therapy applications. However, the achievement of temporal and spatial stabilities for gel dosimeters remains challenging in clinical applications because the fabrication process affects the polymerization reaction during irradiation. This study investigated the dose profile variation of an N-isopropyl acrylamide (NIPAM) polymer gel dosimeter by using the 3-D optical computed tomography scanner OCTOPUSTM 10X (MGS Research Inc.). Two acrylic containers (diameter=10, height=10, and diameter=15, height=15cm ) filled with polymer gel (gelatin: 5%, NIPAM: 5%, Bis: 3%, THPC: 5 mM) were irradiated by using intensity-modulated radiotherapy (SIEMENS Oncor Impression, 6 MV Photo beam). The treatment field was a 3 cm 3 cm square field, and the prescribed dose was 5 Gy. The results of the reconstruction line profile showed that the uncertainty of non-irradiated gel is less than 1.3% when a container with 10 cm diameters cooled in a refrigerator with a water bath. The maximum uncertainties of the irradiated gel at 24 h, 48 h, and 72 h post-irradiation were 2.9%, 2.9%, and 3.1%, respectively. However, the maximum uncertainty of the non-irradiated gel dosimeter increased to 3% when a container with 15 cm diameter was cooled in the same refrigerator. After irradiation, the maximum uncertainties of the irradiated gel at 24 h, 48 h, and 72 h post-irradiation were 13.1%, 13.7%, and 12.95%, respectively. The uncertainty differences for gels at different container sizes were attributed to the different cooling rates that were applied to the gels. The time required for large gel containers to cool in the refrigerator was more than 10 h, whereas the cooling process only took 4.2 h for gels in a small container. The time difference produced different temperature histories for gels and may result in changes in gel sensitivity. Given the thermally induced pre-radiation polymerization, the time difference resulted in a deviation in dose profiles. This study reports that thermal control during gel preparation should be carefully performed for clinical applications to achieve a more accurate dose distribution in 3-D image reconstruction.

Hemostatic potential of natural/synthetic polymer based hydrogels crosslinked by gamma radiation

NASA Astrophysics Data System (ADS)

Barba, Bin Jeremiah D.; Tranquilan-Aranilla, Charito; Abad, Lucille V.

2016-01-01

Various raw materials and hydrogels prepared from their combination were assessed for hemostatic capability using swine whole blood clotting analysis. Initial screening showed efficient coagulative properties from κ-carrageenan and its carboxymethylated form, and α-chitosan, even compared to commercial products like QuikClot Zeolite Powder. Blending natural and synthetic polymers formed into hydrogels using gamma radiation produced materials with improved properties. KC and CMKC hydrogels were found to have the lowest blood clotting index in granulated form and had the higher capacity for platelet adhesion in foamed form compared to GelFoam. Possible mechanisms involved in the evident thrombogenicity of the materials include adsorption of platelets and related proteins that aid in platelet activation (primary hemostasis), absorption of water to concentrate protein factors that control the coagulation cascade, contact activation by its negatively charged surface and the formation of gel-blood clots.

Material and Structural Design of Novel Binder Systems for High-Energy, High-Power Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Ye; Zhou, Xingyi; Yu, Guihua

Developing high-performance battery systems requires the optimization of every battery component, from electrodes and electrolyte to binder systems. However, the conventional strategy to fabricate battery electrodes by casting a mixture of active materials, a nonconductive polymer binder, and a conductive additive onto a metal foil current collector usually leads to electronic or ionic bottlenecks and poor contacts due to the randomly distributed conductive phases. When high-capacity electrode materials are employed, the high stress generated during electrochemical reactions disrupts the mechanical integrity of traditional binder systems, resulting in decreased cycle life of batteries. Thus, it is critical to design novel bindermore » systems that can provide robust, low-resistance, and continuous internal pathways to connect all regions of the electrode. Here in this Account, we review recent progress on material and structural design of novel binder systems. Nonconductive polymers with rich carboxylic groups have been adopted as binders to stabilize ultrahigh-capacity inorganic electrodes that experience large volume or structural change during charge/discharge, due to their strong binding capability to active particles. To enhance the energy density of batteries, different strategies have been adopted to design multifunctional binder systems based on conductive polymers because they can play dual functions of both polymeric binders and conductive additives. We first present that multifunctional binder systems have been designed by tailoring the molecular structures of conductive polymers. Different functional groups are introduced to the polymeric backbone to enable multiple functionalities, allowing separated optimization of the mechanical and swelling properties of the binders without detrimental effect on electronic property. Then, we describe the design of multifunctional binder systems via rationally controlling their nano- and molecular structures, developing the conductive polymer gel binders with 3D framework nanostructures. These gel binders provide multiple functions owing to their structure derived properties. The gel framework facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. The polymer coating formed on every particle acts as surface modification and prevents particle aggregation. The mechanically strong and ductile gel framework also sustains long-term stability of electrodes. In addition, the structures and properties of gel binders can be facilely tuned. We further introduce the development of multifunctional binders by hybridizing conductive polymers with other functional materials. Meanwhile mechanistic understanding on the roles that novel binders play in the electrochemical processes of batteries is also reviewed to reveal general design rules for future binder systems. We conclude with perspectives on their future development with novel multifunctionalities involved. Highly efficient binder systems with well-tailored molecular and nanostructures are critical to reach the entire volume of the battery and maximize energy use for high-energy and high-power lithium batteries. We hope this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of multifunctional binder materials.« less

Material and Structural Design of Novel Binder Systems for High-Energy, High-Power Lithium-Ion Batteries

DOE PAGES

Shi, Ye; Zhou, Xingyi; Yu, Guihua

2017-10-05

Developing high-performance battery systems requires the optimization of every battery component, from electrodes and electrolyte to binder systems. However, the conventional strategy to fabricate battery electrodes by casting a mixture of active materials, a nonconductive polymer binder, and a conductive additive onto a metal foil current collector usually leads to electronic or ionic bottlenecks and poor contacts due to the randomly distributed conductive phases. When high-capacity electrode materials are employed, the high stress generated during electrochemical reactions disrupts the mechanical integrity of traditional binder systems, resulting in decreased cycle life of batteries. Thus, it is critical to design novel bindermore » systems that can provide robust, low-resistance, and continuous internal pathways to connect all regions of the electrode. Here in this Account, we review recent progress on material and structural design of novel binder systems. Nonconductive polymers with rich carboxylic groups have been adopted as binders to stabilize ultrahigh-capacity inorganic electrodes that experience large volume or structural change during charge/discharge, due to their strong binding capability to active particles. To enhance the energy density of batteries, different strategies have been adopted to design multifunctional binder systems based on conductive polymers because they can play dual functions of both polymeric binders and conductive additives. We first present that multifunctional binder systems have been designed by tailoring the molecular structures of conductive polymers. Different functional groups are introduced to the polymeric backbone to enable multiple functionalities, allowing separated optimization of the mechanical and swelling properties of the binders without detrimental effect on electronic property. Then, we describe the design of multifunctional binder systems via rationally controlling their nano- and molecular structures, developing the conductive polymer gel binders with 3D framework nanostructures. These gel binders provide multiple functions owing to their structure derived properties. The gel framework facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. The polymer coating formed on every particle acts as surface modification and prevents particle aggregation. The mechanically strong and ductile gel framework also sustains long-term stability of electrodes. In addition, the structures and properties of gel binders can be facilely tuned. We further introduce the development of multifunctional binders by hybridizing conductive polymers with other functional materials. Meanwhile mechanistic understanding on the roles that novel binders play in the electrochemical processes of batteries is also reviewed to reveal general design rules for future binder systems. We conclude with perspectives on their future development with novel multifunctionalities involved. Highly efficient binder systems with well-tailored molecular and nanostructures are critical to reach the entire volume of the battery and maximize energy use for high-energy and high-power lithium batteries. We hope this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of multifunctional binder materials.« less

Development of ionic gels using thiol-based monomers in ionic liquid

NASA Astrophysics Data System (ADS)

Ahmed, Kumkum; Naga, Naofumi; Kawakami, Masaru; Furukawa, Hidemitsu

2016-04-01

Ionic gels (IGs) using ionic liquids (ILs) can propose diverse applications in the field of optics, sensors and separation have opened wide prospects in materials science. ILs have attracted remarkable interest for gel polymer electrolytes and batteries based on their useful properties such as non-volatility, non-flammability, a wide electrochemical window, high thermal stability and a high ionic conductivity. The formation of gel in IL media makes it possible to immobilize ILs within organic or inorganic matrices and to take advantage of their unique properties in the solid state, thus eliminating some shortcomings related to shaping and risk of leakage. In this work for the first time we used multifunctional thiol monomers having uniform structure and good compatibility with the IL of our interest. Therefore we focused on developing thiol monomer-based IGs using multifunctional thiol monomers and acrylate crosslinkers utilizing thiol-ene reaction between monomer and crosslinking molecules in an IL medium and characterize their physico-chemical properties like thermal, conductive, mechanical properties etc.. This work has been focused mainly to improve the mechanical strength of IGs and make prospects of IGs in tribology and lubricants.

Development, in vitro and in vivo evaluation of novel injectable smart gels of azithromycin for chronic periodontitis.

PubMed

Venkatesh, M P; Kumar, T M Pramod; Avinash, B S; Kumar, G Sheela

2013-04-01

Periodontitis is an inflammatory condition affecting teeth resulting in progressive destruction of periodontal ligaments, resorption of alveolar bone and loss of teeth. Treatment of periodontitis includes surgical and non surgical management. Systemic antibiotics are also used for the treatment of periodontitis. The aim of this research was to formulate smart gel system of azithromycin (AZT) and to evaluate in vitro and in vivo for non-surgical treatment of chronic periodontitis. Azithromycin dihydrate, used systemically in the treatment of periodontitis, was formulated into smart gels using biodegradable, thermosensitive polymer Pluronic® F-127 (PF-127) and Hydroxy Ethyl Cellulose (HEC) as copolymer. The prepared smart gels were evaluated for sterility, content uniformity, gelation temperature and time, syringeability, rheological behavior, in vitro diffusion and in vivo efficacy in human patients. The prepared smart gels were clear and transparent, sterile, thermoresponsive and injectable. Viscosity of gels increased with increase in concentration of polymer/co-polymer and also with temperature. They gelled in short response time below the body temperature. In vitro release studies showed controlled drug release which was influenced significantly by the properties and concentration of PF-127 and HEC. In vivo efficacy studies showed a significant improvement (p <0.001) in clinical parameters such as gingival index, probing pocket depth, clinical attachment level, bleeding index and plaque index. The developed azithromycin smart gel system is a novel approach for the treatment of chronic periodontitis since it reduces the dose and side effects, bypasses the usual surgical procedures and improves patient compliance.

Light-triggered thermoelectric conversion based on a carbon nanotube-polymer hybrid gel.

PubMed

Miyako, Eijiro; Nagata, Hideya; Funahashi, Ryoji; Hirano, Ken; Hirotsu, Takahiro

2009-01-01

Lights? Nanotubes? Action! A hydrogel comprising lysozymes, poly(ethylene glycol), phospholipids, and functionalized single-walled carbon nanotubes is employed for light-driven thermoelectric conversion. A photoinduced thermoelectric conversion module based on the hydrogel functions as a novel electric power generator (see image). This concept may find application in various industries, such as robotics and aerospace engineering.

Novel Hydrogels from Telechelic Polymers

NASA Astrophysics Data System (ADS)

Taribagil, Rajiv R.

The last two decades have seen telechelic polymers support an increasing number of applications as stabilizers and flow modifiers in fields as varied as pharmaceutics, paints and oil recovery. Mainly consisting of a long hydrophilic block end-capped with hydrophobic blocks, these polymers form gels at modest concentrations, comprising hydrophobic junctions with hydrophilic blocks bridging these junctions. This thesis examines two different types of telechelic polymer hydrogels: concentrated dispersions of telechelic triblock copolymers and dilute solutions of wormlike micelles cross-linked by hydrophobically end-capped polymers. Aqueous gels of telechelic poly(ethylene oxide) (PEO)-based triblock polymers, with homo and hetero combinations of 1,2-polybutadiene (PB) and poly(perfluoropropylene oxide) (PFPO) as hydrophobic end-blocks, were investigated using a combination of cryogenic scanning electron microscopy and small-angle neutron scattering. The PB-b-PEO-b-PB copolymers formed networks of spherical micelles at all concentrations as expected, albeit with significant spatial heterogeneity that diminished with increasing concentration. The PFPO-b-PEO-b-PFPO copolymers also formed networks by aggregation of the end-blocks, but the PFPO blocks tended to adopt disk-like or even sheet-like structures. This is attributed to the extremely high interfacial tension of PFPO with water and is consistent with the "super-strong" segregation regime behavior. The heterotelechelic PB-b-PEO- b-PFPO terpolymers adopted a quite different structure, namely an intricate bicontinuous open-cell foam, with cells on the order of 500 nm in size and cell walls composed of PFPO disks embedded in PB sheets. These various network structures illustrate the potential of using end-block chemistry to manipulate both the morphology and the physical properties of polymer gels. Dilute aqueous solutions containing 1 wt% cetyltrimethylammonium tosylate, a surfactant well recognized to form wormlike micelles, and low concentrations of hydrophobically end-capped poly(ethylene oxide), were investigated using dynamic mechanical spectroscopy and small-angle neutron scattering. The detailed examination shows that addition of as little as 0.1 wt% of the polymer to the dilute wormlike micelle solution leads to a massive enhancement in its viscoelastic response. This phenomenon raises the possibility of significantly reducing the amount of additive required to achieve a desired rheological profile, with concomitant advantages in both cost and environmental impact.

Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-04-04

Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

Progress report

NASA Technical Reports Server (NTRS)

Abhiraman, A.; Collard, D.; Cardelino, B.; Bhatia, S.; Desai, P.; Harruna, I.; Khan, I.; Mariam, Y.; Mensah, T.; Mitchell, M.

1992-01-01

The NASA funding allowed Clark Atlanta University (CAU) to establish a High Performance Polymers And Ceramics (HiPPAC) Research Center. The HiPPAC Center is consolidating and expanding the existing polymer and ceramic research capabilities at CAU through the development of interdepartmental and interinstitutional research in: (1) polymer synthesis; (2) polymer characterization and properties; (3) polymer processing; (4) polymer-based ceramic synthesis; and (5) ceramic characterization and properties. This Center has developed strong interactions between scientists and materials scientists of CAU and their counterparts from sister institutions in the Atlanta University Center (AUC) and the Georgia Institute of Technology. As a component of the center, we have started to develop strong collaborations with scientists from other universities and the HBCU's, national and federal agency laboratories, and the private sector during this first year. During this first year we have refined the focus of the research in the HiPPAC Center to three areas with seven working groups that will start programmatic activities on January 1, 1993, as follows: (1) nonlinear optical properties of chitosan derivatives; (2) polymeric electronic materials; (3) nondestructive characterization and prediction of polyimide performance; (4) solution processing of high-performance materials; (5) processable polyimides for composite applications; (6) sol-gel based ceramic materials processing; and (7) synthetic based processing of pre-ceramic polymers.

Method for the preparation of high surface area high permeability carbons

DOEpatents

Lagasse, R.R.; Schroeder, J.L.

1999-05-11

A method for preparing carbon materials having high surface area and high macropore volume to provide high permeability. These carbon materials are prepared by dissolving a carbonizable polymer precursor, in a solvent. The solution is cooled to form a gel. The solvent is extracted from the gel by employing a non-solvent for the polymer. The non-solvent is removed by critical point drying in CO{sub 2} at an elevated pressure and temperature or evaporation in a vacuum oven. The dried product is heated in an inert atmosphere in a first heating step to a first temperature and maintained there for a time sufficient to substantially cross-link the polymer material. The cross-linked polymer material is then carbonized in an inert atmosphere. 3 figs.

Hopping Diffusion of Nanoparticles in Polymer Matrices

PubMed Central

2016-01-01

We propose a hopping mechanism for diffusion of large nonsticky nanoparticles subjected to topological constraints in both unentangled and entangled polymer solids (networks and gels) and entangled polymer liquids (melts and solutions). Probe particles with size larger than the mesh size ax of unentangled polymer networks or tube diameter ae of entangled polymer liquids are trapped by the network or entanglement cells. At long time scales, however, these particles can diffuse by overcoming free energy barrier between neighboring confinement cells. The terminal particle diffusion coefficient dominated by this hopping diffusion is appreciable for particles with size moderately larger than the network mesh size ax or tube diameter ae. Much larger particles in polymer solids will be permanently trapped by local network cells, whereas they can still move in polymer liquids by waiting for entanglement cells to rearrange on the relaxation time scales of these liquids. Hopping diffusion in entangled polymer liquids and networks has a weaker dependence on particle size than that in unentangled networks as entanglements can slide along chains under polymer deformation. The proposed novel hopping model enables understanding the motion of large nanoparticles in polymeric nanocomposites and the transport of nano drug carriers in complex biological gels such as mucus. PMID:25691803

High aspect ratio template and method for producing same for central and peripheral nerve repair

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Chan, Christina (Inventor); Tuszynski, Mark Henry (Inventor); Mehrotra, Sumit (Inventor); Gros, Thomas (Inventor)

2011-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers. The scaffolds may be used in, among other applications, the repair of central and peripheral nerves. Scaffolds for the repair of peripheral nerves may include a reservoir for the sustained release of nerve growth factor. The scaffolds may also include a multifunctional polyelectrolyte layer for the sustained release of nerve growth factor and enhance biocompatibility.

Structure and function of airway surface layer of the human lungs & mobility of probe particles in complex fluids

NASA Astrophysics Data System (ADS)

Cai, Liheng

Numerous infectious particles such as bacteria and pathogens are deposited on the airway surface of the human lungs during our daily breathing. To avoid infection the lung has evolved to develop a smart and powerful defense system called mucociliary clearance. The airway surface layer is a critical component of this mucus clearance system, which consists of two parts: (1) a mucus layer, that traps inhaled particles and transports them out of the lung by cilia-generated flow; and (2) a periciliary layer, that provides a favorable environment for ciliary beating and cell surface lubrication. For 75 years, it has been dogma that a single gel-like mucus layer, which is composed of secreted mucin glycoproteins, is transported over a "watery" periciliary layer. This one-gel model, however, does not explain fundamental features of the normal system, e.g. formation of a distinct mucus layer, nor accurately predict how the mucus clearance system fails in disease. In the first part of this thesis we propose a novel "Gel-on-Brush" model with a mucus layer (the "gel") and a "brush-like" periciliary layer, composed of mucins tethered to the luminal of airway surface, and supporting data accurately describes both the biophysical and cell biological bases for normal mucus clearance and its failure in disease. Our "Gel-on-Brush" model describes for the first time how and why mucus is efficiently cleared in health and unifies the pathogenesis of major human diseases, including cystic fibrosis and chronic obstructive pulmonary disease. It is expected that this "Gel-on-Brush" model of airway surface layer opens new directions for treatments of airway diseases. A dilemma regarding the function of mucus is that, although mucus traps any inhaled harmful particulates, it also poses a long-time problem for drug delivery: mobility of cargos carrying pharmaceutical agents is slowed down in mucus. The second part of this thesis aims to answer the question: can we theoretically understand the relation between the motion of a probe particle and the local structure and dynamics of complex fluids such as mucus, or even one step back, simple polymer solutions and gels? It is well known that the thermal motion of a particle in simple solutions like water can be described by Stokes-Einstein relation, in which the mean-square displacement of the particle is (1) linearly proportional to time and (2) inversely proportional to the bulk viscosity of the solution. We found that these two statements become questionable if the particle size is relatively small and the solutions become complex fluids such as polymer solutions and gels. The motion of small particles with size smaller than the entanglement length (network mesh size) of a polymer solution (gel) is sub-diffusive with mean-square displacement proportional to the square root of time at relatively short time scales. Even at long time scales at which the mean-square displacement of the particles is diffusive, the mean-square displacement of the particles is not necessarily determined by the bulk viscosity, and is inversely proportional to an effective viscosity that is much smaller than the bulk value. An interesting question related to the particle motion in polymer gels is whether particles with size larger than the network mesh size can move through the gel? An intuitive answer would be that such large particles are trapped by the local network cages. We argue that the large particles can still diffuse via hopping mechanism, i.e., particles can wait for fluctuations of surrounding network cages that could be large enough to allow them to slip though. This hopping diffusion can be applied to understand the motion of large particles subjected to topological constraints such as permanent or reversible crosslinked networks as well as entanglements in high molecular weight polymer solutions, melts, and networks.

Roles of Segmental and Oligomeric Diffusion on the Gel Effect in Free Radical Polymerization

NASA Astrophysics Data System (ADS)

Wisnudel, M. B.; Torkelson, J. M.

1996-03-01

Termination between radicals has been simulated by phosphorescence quenching, showing strong roles for segmental and oligomeric radical self-diffusion in the origin of the gel effect. Quenching rate constants (k_q) were measured between benzil-terminated polymer as a function of anthracene-terminated polymer in polymer solutions. In dilute solution, interactions between 10k or 73k MW benzil-terminated polystyrene (PS- B) and anthracence-terminated polystyrene (PS-A) of varying MW, the MW effect is weaker than the Smoluchowski eq. prediction (kq MW^- 0.5). At higher concentration, interactions of PS-B and PS-A of like MW show only weak dependence of kq on MW and a concentration dependence similar to that of segmental mobility, indicating that segmental diffusion is important in termination. Finally, with interactions between 73k MW PS-B and PS-A of varying MW at 35 wt% PS, kq decreases by a factor of 10 in going from MW's of 100 to 1000 g/mol; beyond 1000 g/mol, kq is MW independent. Such effects cannot be explained by polymer-radical self-diffusion. However, they support the notion that the gel effect onset is associated with the concentration dependence of oligomeric radical self-diffusion and polymer radical chain-end segmental mobility.

Preparation and analysis of multilayer composites based on polyelectrolyte complexes

NASA Astrophysics Data System (ADS)

Petrova, V. A.; Orekhov, A. S.; Chernyakov, D. D.; Baklagina, Yu. G.; Romanov, D. P.; Kononova, S. V.; Volod'ko, A. V.; Ermak, I. M.; Klechkovskaya, V. V.; Skorik, Yu. A.

2016-11-01

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan-hyaluronic acid, chitosan-alginic acid, and chitosan-carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Feasibility study of basic characterization of MAGAT polymer gel using CBCT attached in linear accelerator: Preliminary study

NASA Astrophysics Data System (ADS)

Sathiyaraj, P.; Samuel, E. James jebaseelan

2018-01-01

The aim of this study is to evaluate the methacrylic acid, gelatin and tetrakis (hydroxymethyl) phosphonium chloride gel (MAGAT) by cone beam computed tomography (CBCT) attached with modern linear accelerator. To compare the results of standard diagnostic computed tomography (CT) with CBCT, different parameters such as linearity, sensitivity and temporal stability were checked. MAGAT gel showed good linearity for both diagnostic CT and CBCT measurements. Sensitivity and temporal stability were also comparable with diagnostic CT measurements. In both the modalities, the sensitivity of the MAGAT increased to 4 days and decreased till the 10th day of post irradiation. Since all measurements (linearity, sensitivity and temporal stability) from diagnostic CT and CBCT were comparable, CBCT could be a potential tool for dose analysis study for polymer gel dosimeter.

Polymer-Silica Nanocomposites: A Versatile Platform for Multifunctional Materials

NASA Astrophysics Data System (ADS)

Chiu, Chi-Kai

Solution sol-gel synthesis is a versatile approach to create polymer-silica nanocomposite materials. The solution-to-solid transformation results in a solid consisting of interconnected nanoporous structure in 3D space, making it the ideal material for filtration, encapsulation, optics, electronics, drug release, and biomaterials, etc. Although the pore between nano and meso size may be tunable using different reaction conditions, the intrinsic properties such as limited diffusion within pore structure, complicated interfacial interactions at the pore surfaces, shrinkage and stress-induced cracking and brittleness have limited the applications of this material. To overcome these problems, diffusion, pore size, shrinkage and stress-induced defects need further investigation. Thus, the presented thesis will address these important questions such as whether these limitations can be utilized as the novel method to create new materials and lead to new applications. First, the behaviors of polymers such as poly(ethylene glycol) inside the silica pores are examined by studying the nucleation and growth of AgCl at the surface of the porous matrix. The pore structure and the pressure induced by the shrinkage affect have been found to induce the growth of AgCl nanocrystals. When the same process is carried out at 160 °C, silver metallization is possible. Due to the shrinkage-induced stresses, the polymer tends to move into open crack spaces and exterior surfaces, forming interconnected silver structure. This interconnected silver structure is very unique because its density is not related to the size scale of nanopore structures. These findings suggest that it is possible to utilize defect surface of silica material as the template to create interconnected silver structure. When the scale is small, polymer may no longer be needed if the diffusion length of Ag is more than the size of silica particles. To validate our assumption, monoliths of sol-gel sample containing AgNO3 was ground into two different sizes of powder followed by powder pressing, heat-treating and etching. A new robust porous silver foam was then successfully made. By combining the results from room temperature and high temperature processes, we further study the patterned silver nanoparticles arrays in order to examine how mobility of silver can be controlled on a quantifiable scale. Furthermore, we have identified a thiolcontaining sol-gel precursor to control the affinity between silver and silica matrix. Lastly, the effects of interfacial interactions between sol-gel silica and other nanocomposite components and the effect of thickness of the sol-gel layer on mechanical properties were investigated. These studies were applied to the biomimetic hydroxyapatite-gelatin system. We have found that by limiting the thickness while maintaining interfacial interactions of the sol-gel layer, a unique moldable property and short hardening time from these nanocomposites can be achieved without compromising its biocompatibility. Their biocompatibility has been proven based on the in vitro and in vivo testing of these materials. In conclusion, the present study has demonstrated that polymer-silica nanocomposite is a versatile platform to carry out applications in nanocrystal growth, nanoporous metals, metal-ceramic composites, nano-imprint thin film, and bone grafts. These important findings not only provide new insights into nanocomposites but also give new meanings to the previously functional-limited sol-gel materials.

Inter-crosslinking network gels having both shape memory and high ductility

NASA Astrophysics Data System (ADS)

Amano, Yoshitaka; Hidema, Ruri; Furukawa, Hidemitsu

2012-04-01

Medical treatment for injuries should be easy and quick in many accidents. Plasters or bandages are frequently used to wrap and fix injured parts. If plasters or bandages have additional smart functions, such as cooling, removability and repeatability, they will be much more useful and effective. Here we propose innovative biocompatible materials, that is, nontoxic high-strength shape-memory gels as novel smart medical materials. These smart gels were prepared from two monomers (DMAAm and SA), a polymer (HPC), and an inter-crosslinking agent (Karenz-MOI). In the synthesis of the gels, 1) a shape-memory copolymer network is made from the DMAAm and the SA, and 2) the copolymer and the HPC are crosslinked by the Karenz-MOI. Thus the crosslinking points are connected only between the different polymers. This is our original technique of developing a new network structure of gels, named Inter-Crosslinking Network (ICN). The ICN gels achieve high ductility, going up to 700% strain in tensile tests, while the ICN gels contain about 44% water. Moreover the SA has temperature dependence due to its crystallization properties; thus the ICN gels obtain shape memory properties and are named ICN-SMG. While the Young's modulus of the ICN-SMG is large below their crystallization temperature and the gels behave like plastic materials, the modulus becomes smaller above the temperature and the gels turn back to their original shape.

Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

DOEpatents

Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

2006-05-02

An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrova, V. A.; Orekhov, A. S.; Chernyakov, D. D.

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

The relationship between mechanical properties and ballistic penetration depth in a viscoelastic gel.

PubMed

Mrozek, Randy A; Leighliter, Brad; Gold, Christopher S; Beringer, Ian R; Yu, Jian H; VanLandingham, Mark R; Moy, Paul; Foster, Mark H; Lenhart, Joseph L

2015-04-01

The fundamental material response of a viscoelastic material when impacted by a ballistic projectile has important implication for the defense, law enforcement, and medical communities particularly for the evaluation of protective systems. In this paper, we systematically vary the modulus and toughness of a synthetic polymer gel to determine their respective influence on the velocity-dependent penetration of a spherical projectile. The polymer gels were characterized using tensile, compression, and rheological testing taking special care to address the unique challenges associated with obtaining high fidelity mechanical data on highly conformal materials. The depth of penetration data was accurately described using the elastic Froude number for viscoelastic gels ranging in Young's modulus from ~60 to 630 kPa. The minimum velocity of penetration was determined to scale with the gel toughness divided by the gel modulus, a qualitative estimate for the zone of deformation size scale upon impact. We anticipate that this work will provide insight into the critical material factors that control ballistic penetration behavior in soft materials and aid in the design and development of new ballistic testing media. Published by Elsevier Ltd.

Polymer Molecular Weight Analysis by [Superscript 1]H NMR Spectroscopy

ERIC Educational Resources Information Center

Izunobi, Josephat U.; Higginbotham, Clement L.

2011-01-01

The measurement and analysis of molecular weight and molecular weight distribution remain matters of fundamental importance for the characterization and physical properties of polymers. Gel permeation chromatography (GPC) is the most routinely used method for the molecular weight determination of polymers whereas matrix-assisted laser…

Sol-gel derived polymer composites for energy storage and conversion

NASA Astrophysics Data System (ADS)

Han, Kuo

Sol-gel process is a simple chemistry to convert the small precursor molecules into an inorganic polymer, which could be applied to synthesize inorganic materials, modify the interface of materials, bridge the organic and inorganic materials, etc. In this dissertation, novel sol-gel derived composites have been developed for high dielectric breakdown capacitors, low high frequency loss capacitors and flexible piezoelectrics. Numerous efforts have been made in the past decades to improve the energy storage capability of composite materials by incorporating nanometer scale ceramic addictives with high dielectric permittivity into dielectric polymers with high breakdown strength. However, most composites suffer from the low breakdown strength and make the potential gain in energy density small. Here, a new chemical strategy is proposed that, through sol-gel reactions between ceramic precursors and functional groups at the end of the functionalized Poly(vinylidene fluoride -co-chlorotrifluoroethylene) chains, amorphous low permittivity ceramics was in-situ generated in the polymer matrix and cross-linked the polymer chains simultaneously. By carefully tuning precursors, the polymer/precursors feeding ratios, a series of nanocomposites were systematically designed. All the samples are comprehensively characterized and the structure-property correlations are well investigated. The optimal samples exhibit higher breakdown strength than the pristine polymer. The enhanced breakdown strength ascribed to low contrast in permittivity, great dispersion and improved electrical and mechanical properties. This newly developed approach has shown great promise for new composite capacitors. The percolative polymer composites have recently exhibited great potential in energy storage due to their high dielectric permittivities at the neighborhood of the percolation threshold. Yet high energy dissipation and poor voltage endurance of the percolative composites resulted from electrical conduction are still open issues to be addressed before full potential can be realized. Herein we report the percolative composites based on ferroelectric poly(vinylidene fluoride-co-chlorotrifluoroethylene) as the matrix and sol-gel derived SiO2 coated reduced graphene oxide nanosheets as the filler. By capitalizing on the SiO2 surface layers which have high electrical resistivity and breakdown strength, the composites exhibit superior dielectric performance as compared to the respective composites containing bare reduced graphene oxide nanosheet fillers. In addition to greatly reduced dielectric loss, little change in dielectric loss has been observed within medium frequency range (ie. 300 KHz-3 MHz) in the prepared composites even with a filler concentration beyond the percolation threshold, indicating significantly suppressed energy dissipation and the feasibility of using the conductor-insulator composites beyond the percolation threshold. Moreover, remarkable breakdown strength of 80 MV/m at the percolation threshold has been achieved in the composite, which far exceeds those of conventional percolative composites (lower than 0.1 MV/m in most cases) and thus enables the applications of the percolative composites at high electric fields. This work offers a new avenue to the percolative polymer composites exhibiting high permittivity, reduced loss and excellent breakdown strength for electrical energy storage applications. Flexible piezoelectric materials have attracted extensive attention because they can provide a practical way to scavenge energy from the environment and motions. It also provides the possibility to fabricate wearable and self-powered energy generator for powering small electronic devices. In the dissertation a new composite including BTO 3D structure and PDMS has been successfully fabricated using the sol-gel process. The structure, flexibility, dielectric and piezoelectric properties have been well studied. The new material shows a high g33 value of more than 400 mV m/N. Moreover, the durability of this composite has been confirmed by cycle tests even though the BTO structure falls apart into small pieces in the PDMS matrix. The unique morphology of the composite allows the broken piece to connect with each other to generate power under stress. This work also opens a new route toward flexible piezoelectric composites.

Rapid, quantitative analysis of ppm/ppb nicotine using surface-enhanced Raman scattering from polymer-encapsulated Ag nanoparticles (gel-colls).

PubMed

Bell, Steven E J; Sirimuthu, Narayana M S

2004-11-01

Rapid, quantitative SERS analysis of nicotine at ppm/ppb levels has been carried out using stable and inexpensive polymer-encapsulated Ag nanoparticles (gel-colls). The strongest nicotine band (1030 cm(-1)) was measured against d(5)-pyridine internal standard (974 cm(-1)) which was introduced during preparation of the stock gel-colls. Calibration plots of I(nic)/I(pyr) against the concentration of nicotine were non-linear but plotting I(nic)/I(pyr) against [nicotine](x)(x = 0.6-0.75, depending on the exact experimental conditions) gave linear calibrations over the range (0.1-10 ppm) with R(2) typically ca. 0.998. The RMS prediction error was found to be 0.10 ppm when the gel-colls were used for quantitative determination of unknown nicotine samples in 1-5 ppm level. The main advantages of the method are that the gel-colls constitute a highly stable and reproducible SERS medium that allows high throughput (50 sample h(-1)) measurements.

Development and Characterization of Poly(1-vinylpyrrolidone-co-vinyl acetate) Copolymer Based Polymer Electrolytes

PubMed Central

Sa'adun, Nurul Nadiah; Subramaniam, Ramesh; Kasi, Ramesh

2014-01-01

Gel polymer electrolytes (GPEs) are developed using poly(1-vinylpyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] as the host polymer, lithium bis(trifluoromethane) sulfonimide [LiTFSI] as the lithium salt and ionic liquid, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [EMImTFSI] by using solution casting technique. The effect of ionic liquid on ionic conductivity is studied and the optimum ionic conductivity at room temperature is found to be 2.14 × 10−6 S cm−1 for sample containing 25 wt% of EMImTFSI. The temperature dependence of ionic conductivity from 303 K to 353 K exhibits Arrhenius plot behaviour. The thermal stability of the polymer electrolyte system is studied by using thermogravimetric analysis (TGA) while the structural and morphological properties of the polymer electrolyte is studied by using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis (XRD), respectively. PMID:25431781

Design of poly(acrylonitrile)-based gel electrolytes for high-performance lithium ion batteries.

PubMed

Wang, Shih-Hong; Kuo, Ping-Lin; Hsieh, Chien-Te; Teng, Hsisheng

2014-11-12

The use of polyacrylonitrile (PAN) as a host for gel polymer electrolytes (GPEs) commonly produces a strong dipole-dipole interaction with the polymer. This study presents a strategy for the application of PAN in GPEs for the production of high performance lithium ion batteries. The resulting gel electrolyte GPE-AVM comprises a poly(acrylonitrile-co-vinyl acetate) copolymer blending poly(methyl methacrylate) as a host, which is swelled using a liquid electrolyte (LE) of 1 M LiPF6 in carbonate solvent. Vinyl acetate and methacrylate groups segregate the PAN chains in the GPE, which produces high ionic conductivity (3.5 × 10 (-3) S cm(-1) at 30 °C) and a wide electrochemical voltage range (>6.5 V) as well as an excellent Li(+) transference number of 0.6. This study includes GPE-AVM in a full-cell battery comprising a LiFePO4 cathode and graphite anode to promote ion motion, which reduced resistance in the battery by 39% and increased the specific power by 110%, relative to the performance of batteries based on LE. The proposed GPE-based battery has a capacity of 140 mAh g(-1) at a discharge rate of 0.1 C and is able to deliver 67 mAh g(-1) of electricity at 17 C. The proposed GPE-AVM provides a robust interface with the electrodes in full-cell batteries, resulting in 93% capacity retention after 100 charge-discharge cycles at 17 C and 63% retention after 1000 cycles.

Gels of sodium alginate‒chitosan interpolyelectrolyte complexes

NASA Astrophysics Data System (ADS)

Brovko, O. S.; Palamarchuk, I. A.; Val'chuk, N. A.; Chukhchin, D. G.; Bogolitsyn, K. G.; Boitsova, T. A.

2017-08-01

Aspects of the formation of gels of interpolyelectrolyte complexes (IPECs) based on sodium alginate (NaAlg) and chitosan are studied. The effect the conditions of synthesis and complex composition have on the morphological structure and functional properties of these complexes is examined. It is established that complexation in this system proceeds according to a mechanism of electrostatic interaction between the oppositely charged carboxylic groups of the L-hyaluronic acid pyranose cycles of NaAlg proximal polymer chains and chitosan's amino groups, along with a multitude of hydrogen bonds and dispersion forces. We show that the mechanism of IPEC formation is strongly influenced by the conformational state of a lyophilizing component that is present in the system in excess. The inner surfaces of cryogels based on NaAlg‒chitosan IPECs is found to be strongly influenced by the degree of conversion between the parental polyelectrolytes. The most developed mesoporous structure is obtained when a denser gel forms in the system.

Microstructure investigation on micropore formation in microporous silica materials prepared via a catalytic sol-gel process by small angle X-ray scattering.

PubMed

Shimizu, Wataru; Hokka, Junsuke; Sato, Takaaki; Usami, Hisanao; Murakami, Yasushi

2011-08-04

The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) < 2 nm and low fractal dimensions ∼2, which is identical to that of an ideal coil polymer, can selectively be synthesized, yielding the uniform micropores with diameters <2 nm in the solid materials. In contrast, the absence of HA or substitution of 1-propanol led to considerably different scattering behavior reflecting the particle-like aggregate formation in the precursor solution, which resulted in the formation of mesopores (diameter >2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications.

Study on Influence Factors and Governance Countermeasures of Movable Gel Prepared with Backfilling Waste Water

NASA Astrophysics Data System (ADS)

Gao, Shanshan; Zhang, Jianzhong; Zhang, Tiantian; Cui, Yanjie; Wang, Zhiqiang; Sun, Xinrui; Li, Jing; Zhang, Lianchao

2018-05-01

Movable gel as profile control and flooding is one of the main measures in tertiary oil recovery in Huabei Oilfield. Many blocks have tight fresh water supplies, but produced waste water can not be discharged. Therefore, preparing movable gel with backfilling waste water has become an inevitable development trend of profile control and flooding. Three different quality of sewage water named SW, YW and ZW were used to prepare gel and then compared with gel prepared clean water. The results showed that the gel viscosity prepared with clean water was 1.5-5.6 times of sewage water at the same formula concentration. For this reason, the effect of Na+, Ca2+, Fe2+ on the gel performance were analyzed. The above ions lead to a decrease in the gel viscosity and poor stability, which can not even be crosslinked. According to the sewage water characteristics, corresponding treatment measures were developed respectively. The best treatment of SW and ZW was increasing polymer concentration followed by the addition of thiourea. The best treatment of YW was also increasing polymer concentration followed by stirring and aeration. The gel viscosity reached to 1800-2500mPaṡs and maintained at 800-1200mPaṡs after 90 days at formation temperature. It showed that the treatment can effectively improve the gel viscosity and stability prepared with sewage water. The results provide valuable experiences for the preparation of movable gel with different quality waste water.

Variation of concentration of tetrakis and hydroquinone with post-irradiation times in PAGAT polymer gel dosimeter

NASA Astrophysics Data System (ADS)

Venning, Anthony J.; Hill, Brendan; Baldock, Clive

2006-12-01

Following on from the investigation of the normoxic PAGAT polymer gel dosimeter by Venning A J, Hill B, Brindha S, Healy B J and Baldock C 2005 Phys. Med. Biol. 50 3875-3888 this paper examines the change in transverse relaxation rate R2 with time for different concentrations of tetrakis (hydroxymethyl) phosphonium chloride and hydroquinone for fixed concentrations of N,N-methylene-bis-acrylamide, acrylamide, gelatine and H2M/O.

Highly porous ceramic oxide aerogels having improved flexibility

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

2012-01-01

Ceramic oxide aerogels incorporating periodically dispersed flexible linkages are provided. The flexible linkages impart greater flexibility than the native aerogels without those linkages, and have been shown to reduce or eliminate the need for supercritical CO.sub.2-mediated drying of the corresponding wet gels. The gels may also be polymer cross-linked via organic polymer chains that are attached to and extend from surface-bound functional groups provided or present over the internal surfaces of a mesoporous ceramic oxide particle network via appropriate chemical reactions.

Highly stable gel electrolytes for dye solar cells based on chemically engineered polymethacrylic hosts.

PubMed

De Gregorio, Gian Luca; Agosta, Rita; Giannuzzi, Roberto; Martina, Francesca; De Marco, Luisa; Manca, Michele; Gigli, Giuseppe

2012-03-25

Four different species of ionically conductive polymers were synthesized and successfully implemented to formulate novel quasi-solid electrolytes for dye solar cells. A power conversion efficiency superior to 85% of the correspondent liquid electrolyte as well as an excellent cell's stability was demonstrated after 500 days of storage.

Viscoelastic Properties, Ionic Conductivity, and Materials Design Considerations for Poly(styrene-b-ethylene oxide-b-styrene)-Based Ion Gel Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Sipei; Lee, Keun Hyung; Sun, Jingru

2013-03-07

The viscoelastic properties and ionic conductivity of ion gels based on the self-assembly of a poly(styrene-b-ethylene oxide-b-styrene) (SOS) triblock copolymer (M{sub n,S} = 3 kDa, M{sub n,O} = 35 kDa) in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMI][TFSA]) were investigated over the composition range of 10-50 wt % SOS and the temperature range of 25-160 C. The poly(styrene) (PS) end-blocks associate into micelles, whereas the poly(ethylene oxide) (PEO) midblocks are well-solvated by this ionic liquid. The ion gel with 10 wt % SOS melts at 54 C, with the longest relaxation time exhibiting a similar temperature dependence to that of themore » viscosity of bulk PS. However, the actual values of the gel relaxation time are more than 4 orders of magnitude larger than the relaxation time of bulk PS. This is attributed to the thermodynamic penalty of pulling PS end-blocks through the PEO/[EMI][TFSA] matrix. Ion gels with 20-50 wt % SOS do not melt and show two plateaus in the storage modulus over the temperature and frequency ranges measured. The one at higher frequencies is that of an entangled network of PEO strands with PS cross-links; the modulus displays a quadratic dependence on polymer weight fraction and agrees with the prediction of linear viscoelastic theory assuming half of the PEO chains are elastically effective. The frequency that separates the two plateaus, {omega}{sub c}, reflects the time scale of PS end-block pull-out. The other plateau at lower frequencies is that of a congested micelle solution with PS cores and PEO coronas, which has a power law dependence on domain spacing similar to diblock melts. The ionic conductivity of the ion gels is compared to PEO homopolymer solutions at similar polymer concentrations; the conductivity is reduced by a factor of 2.1 or less, decreases with increasing PS volume fraction, and follows predictions based on a simple obstruction model. Our collective results allow the formulation of basic design considerations for optimizing the mechanical properties, thermal stability, and ionic conductivity of these gels.« less

Molecular structure effects on the post irradiation diffusion in polymer gel dosimeters.

PubMed

Mattea, Facundo; Romero, Marcelo R; Vedelago, José; Quiroga, Andrés; Valente, Mauro; Strumia, Miriam C

2015-06-01

Polymer gel dosimeters have specific advantages for recording 3D radiation dose distribution in diagnostic and therapeutic medical applications. But, even in systems where the 3D structure is usually maintained for long periods of time after irradiation, it is still not possible to eliminate the diffusion of the different species in the regions of dose gradients within the gel. As a consequence, information of the dose loses quality over time. In the pursuit of a solution and to improve the understanding of this phenomenon a novel system based on itaconic acid and N-N'-methylene-bisacrylamide (BIS) is hereby proposed. Effects of changes in the chemical structure of the monomers over the dosimetric sensitivity and over the post-irradiation diffusion of species was studied. In this study, one of the carboxylic groups of the itaconic acid molecule was modified with aniline to obtain molecules with similar reactivity but different molecular sizes. Then, dosimeters based on these modified species and on the original ITA molecules were irradiated in an X-ray tomography apparatus at different doses up to 173Gy. Afterwards, the resulting dosimeters were characterized by Raman spectroscopy and optical absorbance in order to study their feasibility and capabilities as dosimetric systems, and by optical-CT to analyze the post irradiation diffusion. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stable, concentrated solutions of polyaniline using amines as gel inhibitors

DOEpatents

Wang, Hsing-Lin; Mattes, Benjamin R.

2002-01-01

Stable, concentrated solutions of high-molecular weight polyaniline using amines as gel inhibitors. Certain amine compounds (gel inhibitors) are used to form highly concentrated, stable solutions of the emeraldine base form of polyaniline in numerous organic solvents from which coatings, films and fibers are readily prepared without problems associated with rapid gelation which occurs when concentrated solutions are attempted without the use of the gel inhibitors of the present invention. Tertiary amines are used to solubilize low-molecular weight fractions (M.sub.w <120,000, M.sub.n <30,000) of the pernigraniline, emeraldine, and leucoemeraldine oxidation states of polyaniline as concentrated (>20 wt. %) polyaniline solutions, while primary and secondary amines are used to produce solutions having 15-40 wt % of high-molecular weight polyaniline [M.sub.w.gtoreq.120,000, M.sub.n.gtoreq.30,000]. Concentrated solutions of polyaniline co-polymers or ring and/or nitrogen-substituted polyanilines may also be prepared.

Polymer-mediated formation of polyoxomolybdate nanomaterials

NASA Astrophysics Data System (ADS)

Wan, Quan

A polymer-mediated synthetic pathway to a polyoxomolybdate nanomaterial is investigated in this work. Block copolymers or homopolymers containing poly(ethylene oxide) (PEO) are mixed with a MoO2(OH)(OOH) aqueous solution to form a golden gel or viscous solution. As revealed by synchrotron X-ray scattering measurements, electron microscopy, and other characterization techniques, the final dark blue polyoxomolybdate product is a highly ordered simple cubic network similar to certain zeolite structure but with a much larger lattice constant of ˜5.2 nm. The average size of the cube-like single crystals is close to 1 mum. Based on its relatively low density (˜2.2 g/cm3), the nanomaterial can be highly porous if the amount of the residual polymer can be substantially reduced. The valence of molybdenum is ˜5.7 based on cerimetric titration, representing the mixed-valence nature of the polyoxomolybdate structure. The self-assembled structures (if any) of the polymer gel do not have any correlation with the final polyoxomolybdate nanostructure, excluding the possible role of polymers being a structure-directing template. On the other hand, the PEO polymer stabilizes the precursor molybdenum compound through coordination between its ether oxygen atoms and molybdenum atoms, and reduces the molybdenum (VI) precursor compound with its hydroxyl group being a reducing agent. The rare simple cubic ordering necessitates the existence of special affinities among the polyoxomolybdate nanosphere units resulted from the reduction reaction. Our mechanism study shows that the acidified condition is necessary for the synthesis of the mixed-valence polyoxomolybdate clusters, while H2O2 content modulates the rate of the reduction reaction. The polymer degradation is evidenced by the observation of a huge viscosity change, and is likely through a hydrolysis process catalyzed by molybdenum compounds. Cube-like polyoxomolybdate nanocrystals with size of ˜40 nm are obtained by means of inversed microemulsions. Reducing agents such as di(ethylene glycol) and glycerol are utilized to synthesize various nanoscale ordering polyoxomolybdate structures. Only PEO-containing polymers are capable of producing the simple cubic polyoxomolybdate nanomaterials. Such a synthetic strategy may open up new pathways to prepare similar functional nanomaterials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Boxin; Schneiderman, Deborah K.; Zare Bidoky, Fazel

We have designed printable, biocompatible, and degradable ion gels by combining a novel ABA triblock aliphatic polyester, poly(ε-decalactone)-b-poly(dl-lactide)-b-poly(ε-decalactone), and a low toxicity ionic liquid, 1-butyl-1-methylpyrrolidinium bistrifluoromethanesulfonylimide ([P14][TFSI]). Due to the favorable compatibility between amorphous poly(dl-lactide) and [P14][TFSI] and the insolubility of the poly(ε-decalactone), the triblock polymer forms self-assembled micellar cross-links similar to thermoplastic elastomers, which ensures similar processing conditions and mechanical robustness during the fabrication of printed electrolyte-gated organic transistor devices. Additionally, the ester backbone in the polymer structure enables efficient hydrolytic degradation of these ion gels compared to those made previously using carbon-backbone polymers.

Outstanding features of alginate-based gel electrolyte with ionic liquid for electric double layer capacitors

NASA Astrophysics Data System (ADS)

Soeda, Kazunari; Yamagata, Masaki; Ishikawa, Masashi

2015-04-01

An alginate-based gel electrolyte with an ionic liquid (Alg/IL) is investigated for electric double-layer capacitors (EDLCs) by using physicochemical and electrochemical measurements. The Alg/EMImBF4 (EMImBF4 = 1-ethyl-3-methylimidazolium tetrafluoroborate) gel electrolyte is thermally stable up to 280 °C, where EMImBF4 decomposes. Furthermore, the EDLC with the gel electrolyte can be operated even at high temperature. The cell containing Alg/EMImBF4 is also electrochemically stable even under high voltage (∼3.5 V) operation. Thus, the alginate is a suitable host polymer for the gel electrolyte for EDLCs. According to the result of charge-discharge characteristics, the voltage drop in the charge-discharge curve for the cell with Alg/EMImBF4 gel electrolyte is considerably smaller than that with liquid-phase EMImBF4 electrolyte. To clarify the effect of Alg in contact with the activated carbon electrode, we also prepared an Alg-containing ACFC electrode (Alg + ACFC), and evaluated its EDLC characteristics in liquid EMImBF4. The results prove that the presence of Alg close to the active materials significantly reduces the internal resistance of the EDLC cell, which may be attributed to the high affinity of Alg to activated carbon.

Optimization and formulation design of gels of Diclofenac and Curcumin for transdermal drug delivery by Box-Behnken statistical design.

PubMed

Chaudhary, Hema; Kohli, Kanchan; Amin, Saima; Rathee, Permender; Kumar, Vikash

2011-02-01

The aim of this study was to develop and optimize a transdermal gel formulation for Diclofenac diethylamine (DDEA) and Curcumin (CRM). A 3-factor, 3-level Box-Behnken design was used to derive a second-order polynomial equation to construct contour plots for prediction of responses. Independent variables studied were the polymer concentration (X(1)), ethanol (X(2)) and propylene glycol (X(3)) and the levels of each factor were low, medium, and high. The dependent variables studied were the skin permeation rate of DDEA (Y(1)), skin permeation rate of CRM (Y(2)), and viscosity of the gels (Y(3)). Response surface plots were drawn, statistical validity of the polynomials was established to find the compositions of optimized formulation which was evaluated using the Franz-type diffusion cell. The permeation rate of DDEA increased proportionally with ethanol concentration but decreased with polymer concentration, whereas the permeation rate of CRM increased proportionally with polymer concentration. Gels showed a non-Fickian super case II (typical zero order) and non-Fickian diffusion release mechanism for DDEA and CRM, respectively. The design demonstrated the role of the derived polynomial equation and contour plots in predicting the values of dependent variables for the preparation and optimization of gel formulation for transdermal drug release. Copyright © 2010 Wiley-Liss, Inc.

A needle extraction utilizing a molecularly imprinted-sol-gel xerogel for on-line microextraction of the lung cancer biomarker bilirubin from plasma and urine samples.

PubMed

Moein, Mohammad Mahdi; Jabbar, Dunia; Colmsjö, Anders; Abdel-Rehim, Mohamed

2014-10-31

In the present work, a needle trap utilizing a molecularly imprinted sol-gel xerogel was prepared for the on-line microextraction of bilirubin from plasma and urine samples. Each prepared needle could be used for approximately one hundred extractions before it was discarded. Imprinted and non-imprinted sol-gel xerogel were applied for the extraction of bilirubin from plasma and urine samples. The produced molecularly imprinted sol-gel xerogel polymer showed high binding capacity and fast adsorption/desorption kinetics for bilirubin in plasma and urine samples. The adsorption capacity of molecularly imprinted sol-gel xerogel polymer was approximately 60% higher than that of non-imprinted polymer. The effect of the conditioning, washing and elution solvents, pH, extraction time, adsorption capacity and imprinting factor were investigated. The limit of detection and the lower limit of quantification were set to 1.6 and 5nmolL(-1), respectively using plasma or urine samples. The standard calibration curves were obtained within the concentration range of 5-1000nmolL(-1) in both plasma and urine samples. The coefficients of determination values (R(2)) were ≥0.998 for all runs. The extraction recovery was approximately 80% for BR in the human plasma and urine samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Modeling the effects of pH and ionic strength on swelling of anionic polyelectrolyte gels

NASA Astrophysics Data System (ADS)

Drozdov, A. D.; deClaville Christiansen, J.

2015-07-01

A constitutive model is developed for the elastic response of an anionic polyelectrolyte gel under swelling in water with an arbitrary pH and an arbitrary molar fraction of dissolved monovalent salt. A gel is treated as a three-phase medium consisting of a solid phase (polymer network), solvent (water), and solute (mobile ions). Transport of solvent and solute is thought of as their diffusion through the polymer network accelerated by an electric field formed by mobile and fixed ions and accompanied by chemical reactions (dissociation of functional groups attached to polymer chains and formation of ion pairs between bound charges and mobile counter-ions). Constitutive equations are derived by means of the free energy imbalance inequality for an arbitrary three-dimensional deformation with finite strains. These relations are applied to analyze equilibrium swelling diagrams on poly(acrylic acid) gel, poly(methacrylic acid) gel, and three composite hydrogels under water uptake in a bath (i) with a fixed molar fraction of salt and varied pH, and (ii) with a fixed pH and varied molar fraction of salt. To validate the ability of the model to predict observations quantitatively, material constants are found by matching swelling curves under one type of experimental conditions and results of simulation are compared with experimental data in the other type of tests.

Ethanol-assisted gel chromatography for single-chirality separation of carbon nanotubes.

PubMed

Zeng, Xiang; Hu, Jinwen; Zhang, Xiao; Zhou, Naigen; Zhou, Weiya; Liu, Huaping; Xie, Sishen

2015-10-21

Surfactants or polymers are usually used for the liquid processing of carbon nanotubes for their structure separation. However, they are difficult to remove after separation, affecting the intrinsic properties and applications of the separated species. Here, we report an ethanol-assisted gel chromatography for the chirality separation of single-walled carbon nanotubes (SWCNTs), in which ethanol is employed to finely tune the density/coverage of sodium dodecyl sulfate (SDS) on nanotubes, and thus the interactions between SWCNTs and an allyl dextran-based gel. Incrementally increasing the ethanol content in a low-concentration SDS eluent leads to successive desorption of the different structure SWCNTs adsorbed on the gel, and to achieve multiple distinct (n, m) single-chirality species. The use of ethanol enables the working concentration of SDS to be reduced dramatically and also avoids the introduction of other surfactants or chemical reagents. More importantly, ethanol can be easily removed after separation. The ability of ethanol to tune the interactions between SWCNTs and the gel also gives a deeper insight into the separation mechanism of SWCNTs using gel chromatography.

Polymer sol-gel composite inverse opal structures.

PubMed

Zhang, Xiaoran; Blanchard, G J

2015-03-25

We report on the formation of composite inverse opal structures where the matrix used to form the inverse opal contains both silica, formed using sol-gel chemistry, and poly(ethylene glycol), PEG. We find that the morphology of the inverse opal structure depends on both the amount of PEG incorporated into the matrix and its molecular weight. The extent of organization in the inverse opal structure, which is characterized by scanning electron microscopy and optical reflectance data, is mediated by the chemical bonding interactions between the silica and PEG constituents in the hybrid matrix. Both polymer chain terminus Si-O-C bonding and hydrogen bonding between the polymer backbone oxygens and silanol functionalities can contribute, with the polymer mediating the extent to which Si-O-Si bonds can form within the silica regions of the matrix due to hydrogen-bonding interactions.

Biodegradable magnesium alloys for orthopaedic applications: A review on corrosion, biocompatibility and surface modifications.

PubMed

Agarwal, Sankalp; Curtin, James; Duffy, Brendan; Jaiswal, Swarna

2016-11-01

Magnesium (Mg) and its alloys have been extensively explored as potential biodegradable implant materials for orthopaedic applications (e.g. Fracture fixation). However, the rapid corrosion of Mg based alloys in physiological conditions has delayed their introduction for therapeutic applications to date. The present review focuses on corrosion, biocompatibility and surface modifications of biodegradable Mg alloys for orthopaedic applications. Initially, the corrosion behaviour of Mg alloys and the effect of alloying elements on corrosion and biocompatibility is discussed. Furthermore, the influence of polymeric deposit coatings, namely sol-gel, synthetic aliphatic polyesters and natural polymers on corrosion and biological performance of Mg and its alloy for orthopaedic applications are presented. It was found that inclusion of alloying elements such as Al, Mn, Ca, Zn and rare earth elements provides improved corrosion resistance to Mg alloys. It has been also observed that sol-gel and synthetic aliphatic polyesters based coatings exhibit improved corrosion resistance as compared to natural polymers, which has higher biocompatibility due to their biomimetic nature. It is concluded that, surface modification is a promising approach to improve the performance of Mg-based biomaterials for orthopaedic applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Water-based thixotropic polymer gel electrolyte for dye-sensitized solar cells.

PubMed

Park, Se Jeong; Yoo, Kichoen; Kim, Jae-Yup; Kim, Jin Young; Lee, Doh-Kwon; Kim, Bongsoo; Kim, Honggon; Kim, Jong Hak; Cho, Jinhan; Ko, Min Jae

2013-05-28

For the practical application of dye-sensitized solar cells (DSSCs), it is important to replace the conventional organic solvents based electrolyte with environmentally friendly and stable ones, due to the toxicity and leakage problems. Here we report a noble water-based thixotropic polymer gel electrolyte containing xanthan gum, which satisfies both the environmentally friendliness and stability against leakage and water intrusion. For application in DSSCs, it was possible to infiltrate the prepared electrolyte into the mesoporous TiO2 electrode at the fluidic state, resulting in sufficient penetration. As a result, this electrolyte exhibited similar conversion efficiency (4.78% at 100 mW cm(-2)) and an enhanced long-term stability compared to a water-based liquid electrolyte. The effects of water on the photovoltaic properties were examined elaborately from the cyclic voltammetry curves and impedance spectra. Despite the positive shift in the conduction band potential of the TiO2 electrode, the open-circuit voltage was enhanced by addition of water in the electrolyte due to the greater positive shift in the I(-)/I3(-) redox potential. However, due to the dye desorption and decreased diffusion coefficient caused by the water content, the short-circuit photocurrent density was reduced. These results will provide great insight into the development of efficient and stable water-based electrolytes.

Silica- and perfluoro-based nanoparticular polymeric network for the skin protection against organophosphates

NASA Astrophysics Data System (ADS)

Bignon, Cécile; Amigoni, Sonia; Guittard, Frédéric

2016-06-01

Due to their small size, nanoparticles possess unique properties such as high absorption or pollutant degradation, making them useful for skin protection against chemicals. By covalently grafting to a hydrophobically modified alkali-soluble emulsion (HASE), a thickening polymer, nanoparticles can be dispersed as gels in water at neutral pH. With this modification the potential aggregation and toxicity typical of nanoparticles are avoided. Once integrated into a cosmetic formula, these gels can be spread onto skin to afford protective barriers. This paper reports (1) the benefit of SiO2 nanoparticles grafted to a perfluorocarbon HASE polymer (HASE-F/SiO2) which is then integrated into a new formula and it is influence on the efficacy against the penetration of paraoxone, as well as (2) the stability of the barrier cream (BC) and (3) how the homogenous dispersion of nanoparticles maintains a high active surface area of SiO2 nanoparticles. The efficiency of the new active topical skin protectant was proved at different doses (5-27 mg cm-2), under occlusive conditions and validated on human skin. Therefore, the combination of the HASE-F polymer, nanoparticle grafting, and polyvinylpyrrolidone and glycerol formulation led to a very effective active BC.

The Formation Mechanism of Hydrogels.

PubMed

Lu, Liyan; Yuan, Shiliang; Wang, Jing; Shen, Yun; Deng, Shuwen; Xie, Luyang; Yang, Qixiang

2017-06-12

Hydrogels are degradable polymeric networks, in which cross-links play a vital role in structure formation and degradation. Cross-linking is a stabilization process in polymer chemistry that leads to the multi-dimensional extension of polymeric chains, resulting in network structures. By cross-linking, hydrogels are formed into stable structures that differ from their raw materials. Generally, hydrogels can be prepared from either synthetic or natural polymers. Based on the types of cross-link junctions, hydrogels can be categorized into two groups: the chemically cross-linked and the physically cross-linked. Chemically cross-linked gels have permanent junctions, in which covalent bonds are present between different polymer chains, thus leading to excellent mechanical strength. Although chemical cross-linking is a highly resourceful method for the formation of hydrogels, the cross-linkers used in hydrogel preparation should be extracted from the hydrogels before use, due to their reported toxicity, while, in physically cross-linked gels, dissolution is prevented by physical interactions, such as ionic interactions, hydrogen bonds or hydrophobic interactions. Physically cross-linked methods for the preparation of hydrogels are the alternate solution for cross-linker toxicity. Both methods will be discussed in this essay. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

A novel lithium/sulfur battery based on sulfur/graphene nanosheet composite cathode and gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Zhang, Yongguang; Zhao, Yan; Bakenov, Zhumabay

2014-03-01

A novel sulfur/graphene nanosheet (S/GNS) composite was prepared via a simple ball milling of sulfur with commercial multi-layer graphene nanosheet, followed by a heat treatment. High-resolution transmission and scanning electronic microscopy observations showed the formation of irregularly interlaced nanosheet-like structure consisting of graphene with uniform sulfur coating on its surface. The electrochemical properties of the resulting composite cathode were investigated in a lithium cell with a gel polymer electrolyte (GPE) prepared by trapping 1 mol dm-3 solution of lithium bistrifluoromethanesulfonamide in tetraethylene glycol dimethyl ether in a polymer matrix composed of poly(vinylidene fluoride-co-hexafluoropropylene)/poly(methylmethacrylate)/silicon dioxide (PVDF-HFP/PMMA/SiO2). The GPE battery delivered reversible discharge capacities of 809 and 413 mAh g-1 at the 1st and 50th cycles at 0.2C, respectively, along with a high coulombic efficiency over 50 cycles. This performance enhancement of the cell was attributed to the suppression of the polysulfide shuttle effect by a collective effect of S/GNS composite cathode and GPE, providing a higher sulfur utilization. PACS: 82.47.Aa; 82.45.Gj; 62.23.Kn

Rheological and tribological study of complex soft gels containing polymer, phospholipids, oil, and water

NASA Astrophysics Data System (ADS)

Farias, Barbara; Hsiao, Lilian; Khan, Saad

Oil-in-water emulsions with polymers are widely used for personal care products. Since the accumulation of traditional surfactants on the skin can promote irritation, an alternative is the use of hydrogenated phosphatidylcholine (HPC), a phospholipid that can form a lamellar structure similar to the skin barrier. This research aims to investigate the effect of composition on the rheological and tribological characteristics in complex systems containing HPC. For tribology experiments we used a soft model contacts made of polydimethylsiloxane (PDMS), while for bulk rheology studies we used dynamic and steady shear experiments. We examine how the addition of polymer, HPC and oil affects friction coefficients, lubrication regimes, viscoelasticity, yield stress, and gel formation. The bulk rheology shows that the studied systems are shear thinning and have gel-like behavior. The effect of each component was investigated by going from simple to more complex systems. The Stribeck curves obtained are related to the bulk rheology results to obtain physical insights into these complex systems. The results suggest that the polymer and phospholipids are being adsorbed onto the PDMS surface, reducing the friction coefficient at lower entrainment speeds.

Gel phase formation in dilute triblock copolyelectrolyte complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chainmore » aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.« less

Gel phase formation in dilute triblock copolyelectrolyte complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chainmore » aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Finally, our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.« less

Gel phase formation in dilute triblock copolyelectrolyte complexes

DOE PAGES

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.; ...

2017-02-23

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chainmore » aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Finally, our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.« less

Gel phase formation in dilute triblock copolyelectrolyte complexes

NASA Astrophysics Data System (ADS)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.; Goldfeld, David J.; Mao, Jun; Heller, William T.; Prabhu, Vivek M.; de Pablo, Juan J.; Tirrell, Matthew V.

2017-02-01

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

Micelle Morphology and Mechanical Response of Triblock Gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seitz, Michelle E.; Burghardt, Wesley R.; Shull, Kenneth R.

2010-01-12

The effect of polymer concentration on mechanical response and micelle morphology of ABA and AB copolymers in B-selective solvents has been systematically studied. Micelle morphology was determined using a combination of small-angle X-ray scattering, shear, and birefringence while mechanical response at low and high strains was determined using indentation techniques. Self-consistent field theory calculations were used to determine micelle volume fraction profiles and to construct an equilibrium phase map. The transition from spherical to cylindrical micelles increases the triblock gel modulus and energy dissipation. Combining knowledge of gel relaxation time, which determines the rate at which the gel can equilibratemore » its micelle structure, with the equilibrium phase map allows estimation of the experimental temperatures and time scales over which kinetic trapping will arrest micelle structure evolution. Kinetic trapping enables cylindrical morphologies to be obtained at significantly lower polymer fractions than is possible in equilibrated systems.« less

Synthesis of hydrogel via click chemistry for DNA electrophoresis.

PubMed

Finetti, Chiara; Sola, Laura; Elliott, Jim; Chiari, Marcella

2017-09-01

This work introduces a novel sieving gel for DNA electrophoresis using a classical click chemistry reaction, the copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC), to cross-link functional polymer chains. The efficiency of this reaction provides, under mild conditions, hydrogels with near-ideal network connectivity and improved physical properties. Hydrogel formation via click chemistry condensation of functional polymers does not involve the use of toxic monomers and UV initiation. The performance of the new hydrogel in the separation of double stranded DNA fragments was evaluated in the 2200 TapeStation system, an analytical platform, recently introduced by Agilent that combines the advantages of CE in terms of miniaturization and automation with the simplicity of use of slab gel electrophoresis. The click gel enables addition of florescent dyes prior to electrophoresis with considerable improvement of resolution and separation efficiency over conventional cross-linked polyacrylamide gels. Copyright © 2017 Elsevier B.V. All rights reserved.

Improvement of the titanium implant biological properties by coating with poly (ε-caprolactone)-based hybrid nanocomposites synthesized via sol-gel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catauro, Michelina; Bollino, Flavia; Papale, Ferdinando

When bioactive coatings are applied to medical implants by means of sol-gel dip coating technique, the biological proprieties of the implant surface can be modified to match the properties of the surrounding tissues. In this study organo-inorganic nanocomposites materials were synthesized via sol-gel. They consisted of an inorganic zirconium-based and silica-based matrix, in which a biodegradable polymer (the poly-ε-caprolactone, PCL) was incorporated in different weight percentages. The synthesized materials, in sol phase, were used to dip-coat a substrate of commercially pure titanium grade 4 (CP Ti gr. 4) in order to improve its biological properties. A microstructural analysis of themore » obtained films was carried out by scanning electron microscopy (SEM) and attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FT-IR). Biological proprieties of the coated substrates were investigated by means of in vitro tests.« less

Exploring the dynamics of phase separation in colloid-polymer mixtures with long range attraction.

PubMed

Sabin, Juan; Bailey, Arthur E; Frisken, Barbara J

2016-06-28

We have studied the kinetics of phase separation and gel formation in a low-dispersity colloid - non-adsorbing polymer system with long range attraction using small-angle light scattering. This system exhibits two-phase and three-phase coexistence of gas, liquid and crystal phases when the strength of attraction is between 2 and 4kBT and gel phases when the strength of attraction is increased. For those samples that undergo macroscopic phase separation, whether to gas-crystal, gas-liquid or gas-liquid-crystal coexistence, we observe dynamic scaling of the structure factor and growth of a characteristic length scale that behaves as expected for phase separation in fluids. In samples that gel, the power law associated with the growth of the dominant length scale is not equal to 1/3, but appears to depend mainly on the strength of attraction, decreasing from 1/3 for samples near the coexistence region to 1/27 at 8kBT, over a wide range of colloid and polymer concentrations.

Investigations on gel forming media use in low gravity bioseparations research

NASA Technical Reports Server (NTRS)

Todd, Paul; Szlag, David C.; Plank, Lindsay D.; Delcourt, Scott G.; Kunze, M. Elaine

1989-01-01

Research on gelling media and conditions suitable for the preservation of the spatial configuration of cell suspensions and macromolecular solutions after separation in free fluid during low gravity experiments is presented. The examples studied included free electrophoresis of cells in a cylindrical column and two-phase aqueous polymer separation. Microgravity electrophoresis experiments were simulated by separating model cell types (animal or human) in a vertical density gradient containing low-conductivity buffer, 1.7-6.5 percent Ficoll, 6.8-5.0 percent sucrose, and 1 percent SeaPrep low-melting temperature agarose. Upon cooling, a gel formed in the column and cells could be captured at the forming locations. Two-phase extraction experiments were simulated using two-polymer solutions in which phase separation occurs in normal saline at temperatures compatible with cell viability and in which one or both phases form a gel upon cooling. Suitable polymers included commercial agaroses (1-2 percent), maltodextrin (5-7 percent), and gelatin (5-20 percent).

Nano- and microsized cubic gel particles from cyclodextrin metal-organic frameworks.

PubMed

Furukawa, Yuki; Ishiwata, Takumi; Sugikawa, Kouta; Kokado, Kenta; Sada, Kazuki

2012-10-15

Sweet cube o' mine: Bottom-up control of gel particles has been regarded as a great challenge. By employing internal cross-linking of cyclodextrin metal-organic frameworks, cubic sugar gels were formed with sharp edges that reflect the shape of the crystals. This enabled the fabrication of shape- and size-controlled polymer gels from porous crystals (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wood-Based Nanocomposite Derived by in Situ Formation of Organic-Inorganic Hybrid Polymer within Wood via a Sol-Gel Method.

PubMed

Dong, Xiaoying; Zhuo, Xiao; Wei, Jie; Zhang, Gang; Li, Yongfeng

2017-03-15

Solid wood materials and wood-plastic composites as two kinds of lightweight materials are attracting great interest from academia and industry due to their green and recycling nature. However, the relatively lower specific strength limits their wider applications. In particular, solid wood is vulnerable to moisture and decay fungi in nature, resulting in its poor durability for effectively long-term utilization. Inspired from the porous structure of wood, we propose a new design to build a wood-based nanocomposite with higher specific strength and satisfactory durability by in situ generation of organic-inorganic hybrid polymer within wood via a sol-gel method. The derived composite has 50-1200% improvement of impact toughness, 56-192% improvement of tensile strength, and 110-291% improvement of flexural strength over those of typical wood-plastic composites, respectively; and even 34% improvement of specific tensile strength than that of 36A steel; 208% enhancement of hardness; and 156% enhancement of compression strength than those of compared solid wood, respectively; as well as significantly improved dimensional stability and decay resistance over those of untreated natural wood. Such materials could be potentially utilized as lightweight and high-strength materials for applications in construction and automotive industries. This method could be extended to constitute other inorganic nanomaterials for novel organic-inorganic hybrid polymer within wood.

Paradoxes of thermodynamics of swelling equilibria of polymers in liquids and vapors.

PubMed

Davankov, Vadim A; Pastukhov, Alexander V

2011-12-29

An automatic registration of the changing size of a single spherical microbead of a cross-linked polymer was applied for studying the swelling process of the bead by the sorption of vapors and/or liquids. Many representatives of all three basic types of polymeric networks, gel-type, hypercrosslinked, and macroporous, were examined. Only the first two display large volume changes and prove suitable for following the kinetics and extent of swelling by the above dilatometric technique. The results unambiguously prove that swelling of all polymeric networks in liquids is always higher than in corresponding saturated vapors (Schroeder's paradox). The general nature of this phenomenon implies that the absolute activity of any sorbate in its liquid form is always larger than in the form of its saturated vapor. Surprisingly, gels with any solvent contents, which fall into the broad range between the vapor-equilibrated and liquid-equilibrated extreme contents, retain their volumes constant in the saturated vapor atmosphere. This paradox of a wide range of gels swollen to a different extent and, nevertheless, standing in equilibrium with saturated vapor is explained by the specificity of the network polymers, namely, that the energy of the solvent-polymer interactions is easily compensated by the energy of remaining between-chain interactions at any solvent content in the above range. Therefore, the strain-free swollen gels do not generate enhanced vapor pressure, but neither display the ability to take up more sorbate from its vapor. © 2011 American Chemical Society

Effect of gellan gum on the thermogelation property and drug release profile of Poloxamer 407 based ophthalmic formulation.

PubMed

Dewan, Mitali; Sarkar, Gunjan; Bhowmik, Manas; Das, Beauty; Chattoapadhyay, Atis Kumar; Rana, Dipak; Chattopadhyay, Dipankar

2017-09-01

The effect of gellan gum on the gelation behavior and in-vitro release of a specific drug named pilocarpine hydrochloride from different ophthalmic formulations based on poloxamer 407 is examined. The mixture of 0.3wt% gellan gum and 18wt% poloxamer (PM) solutions show a considerable increase in gel strength in physiological condition. Gel dissolution rate from PM based formulation is significantly decreased due to the addition of gellan gum. FTIR spectra analysis witnesses an interaction in between OH groups of two polymers which accounts for lowering in gelation temperature of PM-gellan gum based formulations. It is also observed from the cryo-SEM study that the pore size of PM gel decreases with an addition of gellan gum and in-vitro release studies indicate that PM-gellan gum based formulation retain drug better than the PM solution alone. Therefore, the developed formulation has the potential to be utilized as an in-situ ophthalmic drug carrier. Copyright © 2017 Elsevier B.V. All rights reserved.

Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

2000-01-01

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (>15% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

Method for preparing polyaniline fibers

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

2000-01-01

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (>15% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

Monte Carlo modeling of a conventional X-ray computed tomography scanner for gel dosimetry purposes.

PubMed

Hayati, Homa; Mesbahi, Asghar; Nazarpoor, Mahmood

2016-01-01

Our purpose in the current study was to model an X-ray CT scanner with the Monte Carlo (MC) method for gel dosimetry. In this study, a conventional CT scanner with one array detector was modeled with use of the MCNPX MC code. The MC calculated photon fluence in detector arrays was used for image reconstruction of a simple water phantom as well as polyacrylamide polymer gel (PAG) used for radiation therapy. Image reconstruction was performed with the filtered back-projection method with a Hann filter and the Spline interpolation method. Using MC results, we obtained the dose-response curve for images of irradiated gel at different absorbed doses. A spatial resolution of about 2 mm was found for our simulated MC model. The MC-based CT images of the PAG gel showed a reliable increase in the CT number with increasing absorbed dose for the studied gel. Also, our results showed that the current MC model of a CT scanner can be used for further studies on the parameters that influence the usability and reliability of results, such as the photon energy spectra and exposure techniques in X-ray CT gel dosimetry.

Formulation, functional evaluation and ex vivo performance of thermoresponsive soluble gels - A platform for therapeutic delivery to mucosal sinus tissue.

PubMed

Pandey, Preeti; Cabot, Peter J; Wallwork, Benjamin; Panizza, Benedict J; Parekh, Harendra S

2017-01-01

Mucoadhesive in situ gelling systems (soluble gels) have received considerable attention recently as effective stimuli-transforming vectors for a range of drug delivery applications. Considering this fact, the present work involves systematic formulation development, optimization, functional evaluation and ex vivo performance of thermosensitive soluble gels containing dexamethasone 21-phosphate disodium salt (DXN) as the model therapeutic. A series of in situ gel-forming systems comprising the thermoreversible polymer poloxamer-407 (P407), along with hydroxypropyl methyl cellulose (HPMC) and chitosan were first formulated. The optimized soluble gels were evaluated for their potential to promote greater retention at the mucosal surface, for improved therapeutic efficacy, compared to existing solution/suspension-based steroid formulations used clinically. Optimized soluble gels demonstrated a desirable gelation temperature with Newtonian fluid behaviour observed under storage conditions (4-8°C), and pseudoplastic fluid behaviour recorded at nasal cavity/sinus temperature (≈34°C). The in vitro characterization of formulations including rheological evaluation, textural analysis and mucoadhesion studies of the gel form were investigated. Considerable improvement in mechanical properties and mucoadhesion was observed with incorporation of HPMC and chitosan into the gelling systems. The lead poloxamer-based soluble gels, PGHC4 and PGHC7, which were carried through to ex vivo permeation studies displayed extended drug release profiles in conditions mimicking the human nasal cavity, which indicates their suitability for treating a range of conditions affecting the nasal cavity/sinuses. Copyright © 2016 Elsevier B.V. All rights reserved.

Detection of Macromolecular Fractions in HCN Polymers Using Electrophoretic and Ultrafiltration Techniques.

PubMed

Marín-Yaseli, Margarita R; Cid, Cristina; Yagüe, Ana I; Ruiz-Bermejo, Marta

2017-02-01

Elucidating the origin of life involves synthetic as well as analytical challenges. Herein, for the first time, we describe the use of gel electrophoresis and ultrafiltration to fractionate HCN polymers. Since the first prebiotic synthesis of adenine by Oró, HCN polymers have gained much interest in studies on the origins of life due to the identification of biomonomers and related compounds within them. Here, we demonstrate that macromolecular fractions with electrophoretic mobility can also be detected within HCN polymers. The migration of polymers under the influence of an electric field depends not only on their sizes (one-dimensional electrophoresis) but also their different isoelectric points (two-dimensional electrophoresis, 2-DE). The same behaviour was observed for several macromolecular fractions detected in HCN polymers. Macromolecular fractions with apparent molecular weights as high as 250 kDa were detected by tricine-SDS gel electrophoresis. Cationic macromolecular fractions with apparent molecular weights as high as 140 kDa were also detected by 2-DE. The HCN polymers synthesized were fractionated by ultrafiltration. As a result, the molecular weight distributions of the macromolecular fractions detected in the HCN polymers directly depended on the synthetic conditions used to produce these polymers. The implications of these results for prebiotic chemistry will be discussed. © 2017 Wiley-VHCA AG, Zurich, Switzerland.

Gel in core carbosomes as novel ophthalmic vehicles with enhanced corneal permeation and residence.

PubMed

Moustafa, Mona A; El-Refaie, Wessam M; Elnaggar, Yosra S R; Abdallah, Ossama Y

2018-05-17

Carbopol is a good bio-adhesive polymer that increases the residence time in the eye. However, the effect of blinking and lacrimation still reduce the amount of polymer and the incorporated drug available for bioadhesion. Gel-core liposomes are advanced systems offering benefits making it a good tool for improved ocular drug delivery and residence time. Incorporation of carbopol in gel-core liposomes and their potential in ocular delivery have not so far been investigated. Fluconazole (FLZ) was selected as a challenging important ocular antifungal suffering from poor corneal permeation and short residence time. In this study, gel-core carbosomes have been elaborated as novel carbopol-based ophthalmic vehicles to solve ocular delivery obstacles of FLZ and to sustain its effect. Full in vitro appraisal was performed considering gel-core structure, entrapment efficiency, particle size and stability of the vesicles as quality attributes. Structure elucidation of the nanocarrier was performed using optical, polarizing and transmission electron microscopy before and after Triton-X100 addition. Ex-vivo ocular permeation and in vivo performance were investigated on male albino rabbits. Optimized formulation (CBS5) showed gel-core structure, nanosize (339.00 ± 5.50 nm) and not defined before (62.00% ± 1.73) entrapment efficiency. Cumulative amount of CBS5 permeated ex-vivo after 6 h, was 2.43 and 3.43 folds higher than that of conventional liposomes and FLZ suspension, respectively. In-vivo corneal permeation of CBS5 showed significantly higher AUC0-24 h (487.12 ± 74.80) compared to that of FLZ suspension (204.34 ± 7.46) with longer residence time in the eye lasts for more than 18 h. In conclusion, novel gel-core carbosomes could successfully be used as a promising delivery system for chronic ocular diseases. Copyright © 2018 Elsevier B.V. All rights reserved.

Development of polypyrrole based solid-state on-chip microactuators using photolithography

NASA Astrophysics Data System (ADS)

Zhong, Yong; Lundemo, Staffan; Jager, Edwin W. H.

2018-07-01

There is a need for soft microactuators, especially for biomedical applications. We have developed a microfabrication process to create such soft, on-chip polymer based microactuators that can operate in air. The on-chip microactuators were fabricated using standard photolithographic techniques and wet etching, combined with special designed process to micropattern the electroactive polymer polypyrrole that drives the microactuators. By immobilizing a UV-patternable gel containing a liquid electrolyte on top of the electroactive polypyrrole layer, actuation in air was achieved although with reduced movement. Further optimization of the processing is currently on-going. The result shows the possibility to batch fabricate complex microsystems such as microrobotics and micromanipulators based on these solid-state on-chip microactuators using microfabrication methods including standard photolithographic processes.

Facile construction of terpridine-based metallo-polymers in hydrogels, crystals and solutions directed by metal ions.

PubMed

Li, Yajuan; Guo, Jiangbo; Dai, Bo; Geng, Lijun; Shen, Fengjuan; Zhang, Yajun; Yu, Xudong

2018-07-01

Driven by tunable metal-ligand interactions, a polydentate ligand TC containing terpyridine and carboxylic acid units was developed to construct metallo-polymers that showed multiple aggregation modes with controlled macroscopic properties. In the presence of different kind of Zn 2+ ions or NaOH, TC could form metallo-polymers via π-π stacking and metal-ligand interaction that further trapped water molecules, resulting in hydrogels and crystals. Moreover, these TC/Zn 2+ hydrogels could transform to soluble and fluorescent aggregates in the presence of NaOH due to the formation of binuclear metallo-polymers with enhanced ICT emission. The metal-ligand interactions tuned by different metal salts in gels, crystals, and sols were also studied and illustrated in detail, it was also proved that water was an essential linker for constructing Na + -based metallo-polymers from the TC/NaOH crystal data. This work demonstrated the engineered coordination pathways in generating controllable hydrogels and metallo-polymers for the first time, which led to novel approach for facilely constructing a number of hydrogels with tailorable macroscopic properties. Copyright © 2018 Elsevier Inc. All rights reserved.

Bioinspired Programmable Polymer Gel Controlled by Swellable Guest Medium.

PubMed

Deng, Heng; Dong, Yuan; Su, Jheng-Wun; Zhang, Cheng; Xie, Yunchao; Zhang, Chi; Maschmann, Matthew R; Lin, Yuyi; Lin, Jian

2017-09-13

Responsive materials with functions of forming three-dimensional (3D) origami and/or kirigami structures have a broad range of applications in bioelectronics, metamaterials, microrobotics, and microelectromechanical (MEMS) systems. To realize such functions, building blocks of actuating components usually possess localized inhomogeneity so that they respond differently to external stimuli. Previous fabrication strategies lie in localizing nonswellable or less-swellable guest components in their swellable host polymers to reduce swelling ability. Herein, inspired by ice plant seed capsules, we report an opposite strategy of implanting swellable guest medium inside nonswellable host polymers to locally enhance the swelling inhomogeneity. Specifically, we adopted a skinning effect induced surface polymerization combined with direct laser writing to control gradient of swellable cyclopentanone (CP) in both vertical and lateral directions of the nonswellable SU-8. For the first time, the laser direct writing was used as a novel strategy for patterning programmable polymer gel films. Upon stimulation of organic solvents, the dual-gradient gel films designed by origami or kirigami principles exhibit reversible 3D shape transformation. Molecular dynamics (MD) simulation illustrates that CP greatly enhances diffusion rates of stimulus solvent molecules in the SU-8 matrix, which offers the driving force for the programmable response. Furthermore, this bioinspired strategy offers unique capabilities in fabricating responsive devices such as a soft gripper and a locomotive robot, paving new routes to many other responsive polymers.

Immobilization of pectin depolymerising polygalacturonase using different polymers.

PubMed

Ur Rehman, Haneef; Aman, Afsheen; Nawaz, Muhammad Asif; Karim, Asad; Ghani, Maria; Baloch, Abdul Hameed; Ul Qader, Shah Ali

2016-01-01

Polygalacturonase catalyses the hydrolysis of pectin substances and widely has been used in food and textile industries. In current study, different polymers such as calcium alginate beads, polyacrylamide gel and agar-agar matrix were screened for the immobilization of polygalacturonase through entrapment technique. Polyacrylamide gel was found to be most promising one and gave maximum (89%) immobilization yield as compared to agar-agar (80%) and calcium alginate beads (46%). The polymers increased the reaction time of polygalacturonase and polymers entrapped polygalacturonases showed maximum pectinolytic activity after 10 min of reaction as compared to free polygalacturonase which performed maximum activity after 5.0 min of reaction time. The temperature of polygalacturonase for maximum enzymatic activity was increased from 45°C to 50°C and 55°C when it was immobilized within agar-agar and calcium alginate beads, respectively. The optimum pH (pH 10) of polygalacturonase was remained same when it was immobilized within polyacrylamide gel and calcium alginate beads, but changed from pH 10 to pH 9.0 after entrapment within agar-agar. Thermal stability of polygalacturonase was improved after immobilization and immobilized polygalacturonases showed higher tolerance against different temperatures as compared to free enzyme. Polymers entrapped polygalacturonases showed good reusability and retained more than 80% of their initial activity during 2nd cycles. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental study of porous media flow using hydro-gel beads and LED based PIV

NASA Astrophysics Data System (ADS)

Harshani, H. M. D.; Galindo-Torres, S. A.; Scheuermann, A.; Muhlhaus, H. B.

2017-01-01

A novel experimental approach for measuring porous flow characteristics using spherical hydro-gel beads and particle image velocimetry (PIV) technique is presented. A transparent porous medium consisting of hydro-gel beads that are made of a super-absorbent polymer, allows using water as the fluid phase while simultaneously having the same refractive index. As a result, a more adaptable and cost effective refractive index matched (RIM) medium is created. The transparent nature of the porous medium allows optical systems to visualize the flow field by using poly-amide seeding particles (PSP). Low risk light emitting diode (LED) based light was used to illuminate the plane in order to track the seeding particles’ path for the characterization of the flow inside the porous medium. The system was calibrated using a manually measured flow by a flow meter. Velocity profiles were obtained and analysed qualitatively and quantitatively in order to characterise the flow. Results show that this adaptable, low risk experimental set-up can be used for flow measurements in porous medium under low Reynolds numbers. The limitations of using hydro-gel beads are also discussed.

The application of polymer gel dosimeters to dosimetry for targeted radionuclide therapy

NASA Astrophysics Data System (ADS)

Gear, J. I.; Flux, G. D.; Charles-Edwards, E.; Partridge, M.; Cook, G.; Ott, R. J.

2006-07-01

There is a lack of standardized methodology to perform dose calculations for targeted radionuclide therapy and at present no method exists to objectively evaluate the various approaches employed. The aim of the work described here was to investigate the practicality and accuracy of calibrating polymer gel dosimeters such that dose measurements resulting from complex activity distributions can be verified. Twelve vials of the polymer gel dosimeter, 'MAGIC', were uniformly mixed with varying concentrations of P-32 such that absorbed doses ranged from 0 to 30 Gy after a period of 360 h before being imaged on a magnetic resonance scanner. In addition, nine vials were prepared and irradiated using an external 6 MV x-ray beam. Magnetic resonance transverse relaxation time, T2, maps were obtained using a multi-echo spin echo sequence and converted to R2 maps (where T2 = 1/R2). Absorbed doses for P-32 irradiated gel were calculated according to the medical internal radiation dose schema using EGSnrc Monte Carlo simulations. Here the energy deposited in cylinders representing the irradiated vials was scored. A relationship between dose and R2 was determined. Effects from oxygen contamination were present in the internally irradiated vials. An increase in O2 sensitivity over those gels irradiated externally was thought to be a result of the longer irradiation period. However, below the region of contamination dose response appeared homogenous. Due do a drop-off of dose at the periphery of the internally irradiated vials, magnetic resonance ringing artefacts were observed. The ringing did not greatly affect the accuracy of calibration, which was comparable for both methods. The largest errors in calculated dose originated from the initial activity measurements, and were approximately 10%. Measured R2 values ranged from 5-35 s-1 with an average standard deviation of 1%. A clear relationship between R2 and dose was observed, with up to 40% increased sensitivity for internally irradiated gels. Curve fits to the calibration data followed a single exponential function. The correlation coefficients for internally and externally irradiated gels were 0.991 and 0.985, respectively. With the ability to accurately calibrate internally dosed polymer gels, this technology shows promise as a means to evaluate dosimetry methods, particularly in cases of non-uniform uptake of a radionuclide.

Effect of sieving polymer concentration on separation of 100 bp DNA Ladder by capillary gel electrophoresis

NASA Astrophysics Data System (ADS)

Nakazumi, T.; Hara, Y.

2017-09-01

We studied the effect of sieving polymer concentration on separation of a 100 bp DNA Ladder by capillary gel electrophoresis (CGE) using hydroxyethyl cellulose (HEC) with a molecular size of 1000 k. For measurement purposes, we selected a fused silica capillary with total length of 15 cm and effective length of 7.5 cm; this was applied to compact CGE equipment for a Point-Care-Testing (POCT) system. Measurement results of the 100 bp DNA Ladder sample indicated that small DNA separation was significantly affected by HEC sieving polymer concentration. This was due to the level of entanglement between small DNA molecules and the sieving polymer chain significantly influencing migration time, mobility, and resolution length of the CGE process. We concluded that 1.0 w/v % HEC sieving polymer concentration was optimal for CGE separation of DNA ≥1000bp in the 100 bp DNA Ladder (100-1500 bp) when using the short-length capillary.

Systems for production of polymer encapsuated solids

DOEpatents

Bourcier, William L.; Aines, Roger D.; Baker, Sarah E.; Duoss, Eric B.; Maiti, Amitesh; Roberts, Jeffery J.; Spadaccini, Christopher M.; Stolaroff, Joshuah K.; Vericella, John J.; Lewis, Jennifer A.; Hardin, IV, James O.; Floyd, III, William C.

2017-11-21

Encapsulated solids are made by first encapsulating precursor materials in a polymer shell. The precursors are some combination of solids, liquids, gases, and/or gels. The precursors are then transformed into solids by emplacement of the capsule in an environment where gas or fluid transport into or out of the polymer shell causes transformation into solids.

Forming giant-sized polymersomes using gel-assisted rehydration

DOE PAGES

Greene, Adrienne C.; Sasaki, Darryl Y.; Bachand, George D.

2016-05-26

Here, we present a protocol to rapidly form giant polymer vesicles ( pGVs). Briefly, polymer solutions are dehydrated on dried agarose films adhered to coverslips. Rehydration of the polymer films results in rapid formation of pGVs. This method greatly advances the preparation of synthetic giant vesicles for direct applications in biomimetic studies.

Creation of high-refractive-index amorphous titanium oxide thin films from low-fractal-dimension polymeric precursors synthesized by a sol-gel technique with a hydrazine monohydrochloride catalyst.

PubMed

Shimizu, Wataru; Nakamura, Satoshi; Sato, Takaaki; Murakami, Yasushi

2012-08-21

Amorphous titanium dioxide (TiO(2)) thin films exhibiting high refractive indices (n ≈ 2.1) and high transparency were fabricated by spin-coating titanium oxide liquid precursors having a weakly branched polymeric structure. The precursor solution was prepared from titanium tetra-n-butoxide (TTBO) via the catalytic sol-gel process with hydrazine monohydrochloride used as a salt catalyst, which serves as a conjugate acid-base pair catalyst. Our unique catalytic sol-gel technique accelerated the overall polycondensation reaction of partially hydrolyzed alkoxides, which facilitated the formation of liner polymer-like titanium oxide aggregates having a low fractal dimension of ca. (5)/(3), known as a characteristic of the so-called "expanded polymer chain". Such linear polymeric features are essential to the production of highly dense amorphous TiO(2) thin films; mutual interpenetration of the linear polymeric aggregates avoided the creation of void space that is often generated by the densification of high-fractal-dimension (particle-like) aggregates produced in a conventional sol-gel process. The mesh size of the titanium oxide polymers can be tuned either by water concentration or the reaction time, and the smaller mesh size in the liquid precursor led to a higher n value of the solid thin film, thanks to its higher local electron density. The reaction that required no addition of organic ligand to stabilize titanium alkoxides was advantageous to overcoming issues from organic residues such as coloration. The dense amorphous film structure suppressed light scattering loss owing to its extremely smooth surface and the absence of inhomogeneous grains or particles. Furthermore, the fabrication can be accomplished at a low heating temperature of <80 °C. Indeed, we successfully obtained a transparent film with a high refractive index of n = 2.064 (at λ = 633 nm) on a low-heat-resistance plastic, poly(methyl methacrylate), at 60 °C. The result offers an efficient route to high-refractive-index amorphous TiO(2) films as well as base materials for a wider range of applications.

Convective polymer assembly for the deposition of nanostructures and polymer thin films on immobilized particles.

PubMed

Richardson, Joseph J; Björnmalm, Mattias; Gunawan, Sylvia T; Guo, Junling; Liang, Kang; Tardy, Blaise; Sekiguchi, Shota; Noi, Ka Fung; Cui, Jiwei; Ejima, Hirotaka; Caruso, Frank

2014-11-21

We report the preparation of polymer particles via convective polymer assembly (CPA). Convection is used to move polymer solutions and cargo through an agarose gel that contains immobilized template particles. This method both coats and washes the particles in a process that is amenable to automation, and does not depend on passive diffusion or electrical currents, thus facilitating incorporation of fragile and nanoscale objects, such as liposomes and gold nanoparticles, into the thin polymer films. Template dissolution leads to the formation of stable polymer particles and capsules.

Development of Curcumin loaded chitosan polymer based nanoemulsion gel: In vitro, ex vivo evaluation and in vivo wound healing studies.

PubMed

Thomas, Lydia; Zakir, Foziyah; Mirza, Mohd Aamir; Anwer, Md Khalid; Ahmad, Farhan Jalees; Iqbal, Zeenat

2017-08-01

In the present study, various nanoemulsions were prepared using Labrafac PG+Triacetin as oil, Tween 80 as a surfactant and polyethylene glycol (PEG 400) as a co-surfactant. The developed nanoemulsions (NE1-NE5) were evaluated for physicochemical characterizations and ex-vivo for skin permeation and deposition studies. The highest skin deposition was observed for NE2 with 46.07% deposition amongst all developed nanoemulsions (NE1-NE5). Optimized nanoemulsion (NE2) had vesicle size of 84.032±0.023nm, viscosity 78.23±22.2 cps, refractive index 1.404. Nanoemulsion gel were developed by incorporation of optimized nanoemulsion (NE2) into 1-3% chitosan and characterized by physical evaluation and rheological studies. Chitosan gel (2%) was found to be suitable for gelation of nanoemulsion based on its consistency, feel and ease of spreadability. The flux of nanoemulsion gel was found 68.88μg/cm 2 /h as compared to NE2 (76.05μg/cm 2 /h) is significantly lower suggesting limited skin permeation of curcumin form gel. However, the retained amount of curcumin on skin by gel formulation (980.75±88μg) is significantly higher than NE2 (771.25±67μg). Enhanced skin permeation of NE2 (46.07%) was observed when compared to nanoemulsion gel (31.25%) and plain gel (11.47%). The outcome of this study evidently points out the potential of curcumin entrapped nanoemulsion gel in wound healing. Copyright © 2017 Elsevier B.V. All rights reserved.

Changes in ionic selectivity with changes in density of water in gels and cells

PubMed Central

Wiggins, Philippa M.; van Ryn, René T.

1990-01-01

Gels equilibrated with aqueous solutions of impermeant solutes reached a steady state in which, in the absence of a pressure difference, the activity of water in the pores of the gel was higher than that of water in the external solution. The chemical potential of water in the gel/polymer solution slurry was higher than that in the supernatant polymer solution removed from the gel. Water in the pores of the gel decreased in density to 0.96 as increasing osmotic stress was applied. It is argued that at constant temperature and pressure water can equilibrate between two compartments of unequal osmolality only by adjusting its molar volume. Experiments showed that when gel water had a higher activity than external water it was K+ selective; when it had a lower activity it was Na+ selective. It is proposed that a continuous spectrum of water structures can exist in these two compartment systems from dense, reactive, weakly-bonded water which selects highly hydrated ions, to expanded, stretched, unreactive, viscous water which is strongly hydrogen bonded and selects K+ and univalent anions. These findings are related to the state and properties of cytoplasmic water which is probably held under osmotic stress by the activity of the sodium pump. PMID:19431765

Anticorrosion Coatings Based on Assemblies of Superhydrophobic Particles Impregnated with Conductive Oil

DTIC Science & Technology

2016-05-13

silver nanowires synthesized in our group using sol-gel techniques...been demonstrated (Figure 12). The electrical resistance of the coatings should further be decreased Figure 14. High aspect ratio silver nanowires ...the coatings is to use a conductive polymer matrix and disperse high aspect ratio silver nanowires into the coating formulations. The electrical

Tung oil-based unsaturated co-ester macromonomer for thermosetting polymers: Synergetic synthesis and copolymerization with styrene

USDA-ARS?s Scientific Manuscript database

A novel unsaturated co-ester (co-UE) macromonomer containing both maleates and acrylates was synthesized from tung oil (TO) and its chemical structure was characterized by FT-IR, 1H-NMR, 13C-NMR, and gel permeation chromatography (GPC). The monomer was synthesized via a new synergetic modification o...

DNA Based Electrochromic and Photovoltaic Cells

DTIC Science & Technology

2012-01-01

electrolyte/CeO2- TiO2 /ITO/glass configuration [29]. 2. Experimental 2.1 Gel polymeric electrolytes The electrolytes were prepared according to the...transparent membranes. Blend samples were also prepared by the addition of other macromolecules (gelatin), synthetic polymers, such as poly(ethylene...Electrochromic devices Electrochromic devices with the glass/ITO/WO3/DNA-based electrolyte/CeO2- TiO2 /ITO/glass configuration were obtained by assembling

Quasi-solid state electrolyte for semi-transparent bifacial dye-sensitized solar cell with over 10% power conversion efficiency

NASA Astrophysics Data System (ADS)

Hwang, Dae-Kue; Nam, Jung Eun; Jo, Hyo Jeong; Sung, Shi-Joon

2017-09-01

In traditional dye-sensitized solar cells (DSSCs), the liquid electrolyte (LE) presents a problem for long-term stability. Herein, we demonstrate a bifacial DSSC by combining a new metal-free organic dye and a quasi-solid state electrolyte (QSSE) that contains poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP)-based polymer gel. The incident light irradiates the front side of the DSSC, and the transmitted light is reused after reflection on the back side. Owing to the semi-transparent DSSC electrode, the reflected light can penetrate and be absorbed by the dye molecules in the DSSC, thereby enhancing the short-circuit current density and thus the overall power conversion efficiency (PCE). The PCE for the DSSC device with QSSE from bifacial irradiation is 10.37%, a value that is comparable to that obtained with LE-based DSSC (9.89%). The stability of the device is enhanced when the polymer gel containing PVdF-HFP is mixed with the LE, and the effectiveness of PVdF-HFP as a gelator is attributed to its interaction with the Li+ ions. Based on our preliminary results, this architecture can lead to more stable bifacial QSSE-based DSSCs without sacrificing the photovoltaic performance.

Evaluation of an injectable polymeric delivery system for controlled and localized release of biological factors to promote therapeutic angiogenesis

NASA Astrophysics Data System (ADS)

Rocker, Adam John

Cardiovascular disease remains as the leading cause of death worldwide and is frequently associated with partial or full occlusion of coronary arteries. Currently, angioplasty and bypass surgery are the standard approaches for treating patients with these ischemic heart conditions. However, a large number of patients cannot undergo these procedures. Therapeutic angiogenesis provides a minimally invasive tool for treating cardiovascular diseases by inducing new blood vessel growth from the existing vasculature. Angiogenic growth factors can be delivered locally through gene, cell, and protein therapy. Natural and synthetic polymer growth factor delivery systems are under extensive investigation due their widespread applications and promising therapeutic potential. Although biocompatible, natural polymers often suffer from batch-to-batch variability which can cause unpredictable growth factor release rates. Synthetic polymers offer advantages for growth factor delivery as they can be easily modified to control release kinetics. During the angiogenesis process, vascular endothelial growth factor (VEGF) is necessary to initiate neovessel formation while platelet-derived growth factor (PDGF) is needed later to help stabilize and mature new vessels. In the setting of myocardial infarction, additional anti-inflammatory cytokines like IL-10 are needed to help optimize cardiac repair and limit the damaging effects of inflammation following infarction. To meet these angiogenic and anti-inflammatory needs, an injectable polymer delivery system created from a sulfonated reverse thermal gel encapsulating micelle nanoparticles was designed and evaluated. The sulfonate groups on the thermal gel electrostatically bind to VEGF which controls its release rate, while the micelles are loaded with PDGF and are slowly released as the gel degrades. IL-10 was loaded into the system as well and diffused from the gel over time. An in vitro release study was performed which demonstrated the sequential release capabilities of the polymer system. The ability of the polymer system to induce new blood vessel formation was analyzed in vivo using a subcutaneous injection mouse model. Histological assessment was used to quantify blood vessel formation and an inflammatory response which showed that the polymer delivery system demonstrated a significant increase in functional and mature vessel formation while significantly reducing inflammation.

Role of precursors and coating polymers in sol-gel chemistry toward enhanced selectivity and efficiency in solid phase microextraction.

PubMed

Bagheri, Habib; Piri-Moghadam, Hamed; Ahdi, Tayebeh

2012-09-12

To evaluate the selectivity and efficiency of solid phase microextraction (SPME) fiber coatings, synthesized by sol-gel technology, roles of precursors and coating polymers were extensively investigated. An on-line combination of capillary microextraction (CME) technique and high performance liquid chromatography (HPLC) was set up to perform the investigation. Ten different fiber coatings were synthesized in which five of them contained only the precursor and the rests were prepared using both the precursor and coating polymer. All the coatings were chemically bonded to the inner surface of copper tubes, intended to be used as the CME device and already functionalized by self-assembly monolayers of 3-(mercaptopropyl)trimethoxysilane (3MPTMOS). The selected precursors included tetramethoxysilane (TMOS), 3-(trimethoxysilyl)propylmethacrylate (TMSPMA), 3-(triethoxysilyl)-propylamine (TMSPA), 3MPTMOS, [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane (EPPTMOS) while poly(ethyleneglycol) (PEG) was chosen as the coating polymer. The effects of different precursors on the extraction efficiency and selectivity, was studied by selecting a list of compounds ranging from non-polar to polar ones, i.e. polycyclic aromatic hydrocarbon, herbicides, estrogens and triazines. The results from CME-HPLC analysis revealed that there is no significant difference between precursors, except TMOS, in which has the lowest extraction efficiency. Most of the selected precursors have rather similar interactions toward the selected analytes which include Van der Walls, dipole-dipole and hydrogen bond while TMOS has only dipole-dipole interaction and therefore the least efficiency. TMOS is silica but the other sorbents are organically modified silica (ORMOSIL). Our investigation revealed that it is rather impossible to prepare a selective coating using conventional sol-gel methodologies. The comparison study performed among the fiber coatings contained only a precursor and those synthesized by a precursor along with coating polymer proved that the extraction efficiency obtained for all coatings are the same. This is an indication that by selecting the appropriate precursor there is no need to use any coating polymer. In overall, a fiber coating in sol-gel process could be synthesize with no coating polymer which leads to faster, easier, cheaper and more controllable synthesis. Copyright © 2012 Elsevier B.V. All rights reserved.

Holographic Recording Materials Development

NASA Technical Reports Server (NTRS)

Verber, C. M.; Schwerzel, R. E.; Perry, P. J.; Craig, R. A.

1976-01-01

Organic photorefractive materials were evaluated for application in a reversible holographic memory system. Representative indigo and thioindigo derivatives and several stilbene derivatives were studied as well as 15, 16-dialkyldihydropyrene derivatives the following goals were achieved: (1) the successful writing of phase holograms in a thioindigo/polymer gel system, (2) the successful writing and erasing of phase holograms in a variety of indigo/polymer gel and indigo/solid polymer systems, and (3) the identification of indigoid dyes and 15, 16-dialkyldihydropyrene derivatives as materials potentially suitable for utilization in an operational system. Photochemical studies of the stilbene, indigo, thioindigo, and dialkyldihydropyrene derivatives in solution and in a variety of polymer matrix materials were conducted with the goal of optimizing the photorefractive behavior of the chemical system as a whole. The spectroscopic properties required of optimal photorefractive materials were identified, and it was shown that both the indigoid dyes and the dialkyldihydropyrenes closely match the required properties.

Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

PubMed

Yin, H; Casey, P S; Chow, G M

2012-11-01

Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

Conductivity and power factor enhancement of n-type semiconducting polymers using sodium silica gel dopant

NASA Astrophysics Data System (ADS)

Madan, Deepa; Zhao, Xingang; Ireland, Robert M.; Xiao, Derek; Katz, Howard E.

2017-08-01

This work demonstrates the use of sodium silica gel (Na-SG) particles as a reducing agent for n-type conjugated polymers to improve the conductivity and thermoelectric properties. Substantial increase in the electrical conductivity (σ, from 10-7 to 10-3 S/cm in air) was observed in two naphthalenetetracarboxylic diimide solution-processable n-type polymers, one of which was designed and synthesized in our lab. Systematic investigations of electrical conductivity were done by varying the weight percentage of Na-SG in the polymers. Additional evidence for the reduction process was obtained from electron spin resonance spectroscopy and control experiments involving nonreducing silica particles and non-electron-accepting polystyrene. The Seebeck coefficient S of the highest conductivity sample was measured and found to be in agreement with an empirical model. All the electrical conductivity and Seebeck coefficients measurements were performed in ambient atmosphere.

Method of Cross-Linking Aerogels Using a One-Pot Reaction Scheme

NASA Technical Reports Server (NTRS)

Meador, Ann B.; Capadona, Lynn A.

2008-01-01

A document discusses a new, simplified method for cross-linking silica and other oxide aerogels, with a polymeric material to increase strength of such materials without adversely affecting porosity or low density. This innovation introduces the polymer precursor into the sol before gelation either as an agent, which co-reacts with the oxide gel, or as soluble polymer precursors, which do not interact with the oxide gel in any way. Subsequent exposure to heat, light, catalyst or other method of promoting polymerization causes cross-linking without any additional infiltration steps.

Ultrasonic degradation of butadiene, styrene and their copolymers.

PubMed

Sathiskumar, P S; Madras, Giridhar

2012-05-01

Ultrasonic degradation of commercially important polymers, styrene-butadiene (SBR) rubber, acrylonitrile-butadiene (NBR) rubber, styrene-acrylonitrile (SAN), polybutadiene rubber and polystyrene were investigated. The molecular weight distributions were measured using gel permeation chromatography (GPC). A model based on continuous distribution kinetics approach was used to study the time evolution of molecular weight distribution for these polymers during degradation. The effect of solvent properties and ultrasound intensity on the degradation of SBR rubber was investigated using different pure solvents and mixed solvents of varying volatility and different ultrasonic intensities. Copyright © 2011 Elsevier B.V. All rights reserved.

Preparation, characterization, and activity of α-Ti(HPO4)2 supported metallocene catalysts

NASA Astrophysics Data System (ADS)

Shi, Yasai; Yuan, Yuan; Xu, Qinghong; Yi, Jianjun

2016-10-01

A series of heterogeneous catalysts by loading metallocenes on surface of α-Ti(HPO4)2, a kind of solid acid, has been synthesized. Polymerization of alkenes, including ethylene and propylene, based on participation of the heterogeneous catalysts were studied and the results were compared to metallocenes supported on silica gel, α-Zr(HPO4)2 and clay. Higher catalytic activity, larger polymer molecular weight and narrow distribution of polymer molecular weight were obtained. Acidic strength of the support and its influence to metallocenes were studied to discover intrinsic factors in the polymerizations.

Preparation of oxide glasses from metal alkoxides by sol-gel method

NASA Technical Reports Server (NTRS)

Kamiya, K.; Yoko, T.; Sakka, S.

1987-01-01

An investigation is carried out on the types of siloxane polymers produced in the course of the hydrolysis of silicon tetraethoxide, as well as the preparation of oxide glasses from metal alkoxides by the sol-gel method.

Bond rupture between colloidal particles with a depletion interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitaker, Kathryn A.; Furst, Eric M., E-mail: furst@udel.edu

The force required to break the bonds of a depletion gel is measured by dynamically loading pairs of colloidal particles suspended in a solution of a nonadsorbing polymer. Sterically stabilized poly(methyl methacrylate) colloids that are 2.7 μm diameter are brought into contact in a solvent mixture of cyclohexane-cyclohexyl bromide and polystyrene polymer depletant. The particle pairs are subject to a tensile load at a constant loading rate over many approach-retraction cycles. The stochastic nature of the thermal rupture events results in a distribution of bond rupture forces with an average magnitude and variance that increases with increasing depletant concentration. The measuredmore » force distribution is described by the flux of particle pairs sampling the energy barrier of the bond interaction potential based on the Asakura–Oosawa depletion model. A transition state model demonstrates the significance of lubrication hydrodynamic interactions and the effect of the applied loading rate on the rupture force of bonds in a depletion gel.« less

Recent advances in material science for developing enzyme electrodes.

PubMed

Sarma, Anil Kumar; Vatsyayan, Preety; Goswami, Pranab; Minteer, Shelley D

2009-04-15

The enzyme-modified electrode is the fundamental component of amperometric biosensors and biofuel cells. The selection of appropriate combinations of materials, such as: enzyme, electron transport mediator, binding and encapsulation materials, conductive support matrix and solid support, for construction of enzyme-modified electrodes governs the efficiency of the electrodes in terms of electron transfer kinetics, mass transport, stability, and reproducibility. This review investigates the varieties of materials that can be used for these purposes. Recent innovation in conductive electro-active polymers, functionalized polymers, biocompatible composite materials, composites of transition metal-based complexes and organometallic compounds, sol-gel and hydro-gel materials, nanomaterials, other nano-metal composites, and nano-metal oxides are reviewed and discussed here. In addition, the critical issues related to the construction of enzyme electrodes and their application for biosensor and biofuel cell applications are also highlighted in this article. Effort has been made to cover the recent literature on the advancement of materials sciences to develop enzyme electrodes and their potential applications for the construction of biosensors and biofuel cells.

Characterization and quantitation of polyolefin microplastics in personal-care products using high-temperature gel-permeation chromatography.

PubMed

Hintersteiner, Ingrid; Himmelsbach, Markus; Buchberger, Wolfgang W

2015-02-01

In recent years, the development of reliable methods for the quantitation of microplastics in different samples, including evaluating the particles' adverse effects in the marine environment, has become a great concern. Because polyolefins are the most prevalent type of polymer in personal-care products containing microplastics, this study presents a novel approach for their quantitation. The method is suitable for aqueous and hydrocarbon-based products, and includes a rapid sample clean-up involving twofold density separation and a subsequent quantitation with high-temperature gel-permeation chromatography. In contrast with previous procedures, both errors caused by weighing after insufficient separation of plastics and matrix and time-consuming visual sorting are avoided. In addition to reliable quantitative results, in this investigation a comprehensive characterization of the polymer particles isolated from the product matrix, covering size, shape, molecular weight distribution and stabilization, is provided. Results for seven different personal-care products are presented. Recoveries of this method were in the range of 92-96 %.

Molecular Dynamics Simulation Study of the Selectivity of a Silica Polymer for Ibuprofen

PubMed Central

Concu, Riccardo; Cordeiro, M. Natalia D. S.

2016-01-01

In the past few years, the sol-gel polycondensation technique has been increasingly employed with great success as an alternative approach to the preparation of molecularly imprinted materials (MIMs). The main aim of this study was to study, through a series of molecular dynamics (MD) simulations, the selectivity of an imprinted silica xerogel towards a new template—the (±)-2-(P-Isobutylphenyl) propionic acid (Ibuprofen, IBU). We have previously demonstrated the affinity of this silica xerogel toward a similar molecule. In the present study, we simulated the imprinting process occurring in a sol-gel mixture using the Optimized Potentials for Liquid Simulations-All Atom (OPLS-AA) force field, in order to evaluate the selectivity of this xerogel for a template molecule. In addition, for the first time, we have developed and verified a new parameterisation for the Ibuprofen® based on the OPLS-AA framework. To evaluate the selectivity of the polymer, we have employed both the radial distribution functions, interaction energies and cluster analyses. PMID:27399685

Molecular Dynamics Simulation Study of the Selectivity of a Silica Polymer for Ibuprofen.

PubMed

Concu, Riccardo; Cordeiro, M Natalia D S

2016-07-07

In the past few years, the sol-gel polycondensation technique has been increasingly employed with great success as an alternative approach to the preparation of molecularly imprinted materials (MIMs). The main aim of this study was to study, through a series of molecular dynamics (MD) simulations, the selectivity of an imprinted silica xerogel towards a new template-the (±)-2-(P-Isobutylphenyl) propionic acid (Ibuprofen, IBU). We have previously demonstrated the affinity of this silica xerogel toward a similar molecule. In the present study, we simulated the imprinting process occurring in a sol-gel mixture using the Optimized Potentials for Liquid Simulations-All Atom (OPLS-AA) force field, in order to evaluate the selectivity of this xerogel for a template molecule. In addition, for the first time, we have developed and verified a new parameterisation for the Ibuprofen(®) based on the OPLS-AA framework. To evaluate the selectivity of the polymer, we have employed both the radial distribution functions, interaction energies and cluster analyses.

Novel microemulsion-based gels for topical delivery of indomethacin: Formulation, physicochemical properties and in vitro drug release studies.

PubMed

Froelich, Anna; Osmałek, Tomasz; Snela, Agnieszka; Kunstman, Paweł; Jadach, Barbara; Olejniczak, Marta; Roszak, Grzegorz; Białas, Wojciech

2017-12-01

Microemulsion-based semisolid systems may be considered as an interesting alternative to the traditional dosage forms applied in topical drug delivery. Mechanical properties of topical products are important both in terms of application and dosage form effectiveness. In this study we designed and evaluated novel microemulsion-based gels with indomethacin and analyzed the factors affecting their mechanical characteristics and drug release. The impact of the microemulsion composition on the extent of isotropic region was investigated with the use of pseudoternary phase diagrams. Selected microemulsions were analyzed in terms of electrical conductivity and surface tension in order to determine the microemulsion type. Microemulsions were transformed into polymer-based gels and subjected to rheological and textural studies. Finally, the indomethacin release from the analyzed gels was studied and compared to commercially available product. The extent of isotropic domain in pseudoternary phase diagrams seems to be dependent on the polarity of the oil phase. The surface tension and conductivity monitored as a function of water content in microemulsion systems revealed possible structural transformations from w/o through bicontinuous systems into o/w. The mechanical properties of semisolid microemulsion-based systems depended on the composition of surface active agents and the drug presence. The drug release profiles observed in the case of the investigated gels differed from those recorded for the commercially available product which was most probably caused by the different structure of both systems. Copyright © 2017 Elsevier Inc. All rights reserved.

Three-dimensional dose verification of the clinical application of gamma knife stereotactic radiosurgery using polymer gel and MRI.

PubMed

Papagiannis, P; Karaiskos, P; Kozicki, M; Rosiak, J M; Sakelliou, L; Sandilos, P; Seimenis, I; Torrens, M

2005-05-07

This work seeks to verify multi-shot clinical applications of stereotactic radiosurgery with a Leksell Gamma Knife model C unit employing a polymer gel-MRI based experimental procedure, which has already been shown to be capable of verifying the precision and accuracy of dose delivery in single-shot gamma knife applications. The treatment plan studied in the present work resembles a clinical treatment case of pituitary adenoma using four 8 mm and one 14 mm collimator helmet shots to deliver a prescription dose of 15 Gy to the 50% isodose line (30 Gy maximum dose). For the experimental dose verification of the treatment plan, the same criteria as those used in the clinical treatment planning evaluation were employed. These included comparison of measured and GammaPlan calculated data, in terms of percentage isodose contours on axial, coronal and sagittal planes, as well as 3D plan evaluation criteria such as dose-volume histograms for the target volume, target coverage and conformity indices. Measured percentage isodose contours compared favourably with calculated ones despite individual point fluctuations at low dose contours (e.g., 20%) mainly due to the effect of T2 measurement uncertainty on dose resolution. Dose-volume histogram data were also found in a good agreement while the experimental results for the percentage target coverage and conformity index were 94% and 1.17 relative to corresponding GammaPlan calculations of 96% and 1.12, respectively. Overall, polymer gel results verified the planned dose distribution within experimental uncertainties and uncertainty related to the digitization process of selected GammaPlan output data.

Investigation of in situ gelling alginate formulations as a sustained release vehicle for co-precipitates of dextromethrophan and Eudragit S 100.

PubMed

El Maghraby, Gamal Mohamed; Elzayat, Ehab Mostafa; Alanazi, Fars Kaed

2014-03-01

Alginate vehicles are capable of forming a gel matrix in situ when they come into contact with gastric medium in the presence of calcium ions. However, the gel structure is pH dependent and can break after gastric emptying, leading to dose dumping. The aim of this work was to develop modified in situ gelling alginate formulations capable of sustaining dextromethorphan release throughout the gastrointestinal tract. Alginate solution (2 %, m/m) was used as a vehicle for the tested formulations. Solid matrix of the drug and Eudragit S 100 was prepared by dissolving the drug and polymer in acetone. The organic solvent was then evaporated and the deposited solid matrix was micronized, sieved and dispersed in alginate solution to obtain candidate formulations. The release behavior of dextromethorphan was monitored and evaluated in a medium simulating the gastric and intestinal pH. Drug-polymer compatibility and possible solid-state interactions suggested physical interaction through hydrogen bonding between the drug and the polymer. A significant decrease in the rate and extent of dextromethorphan release was observed with increasing Eudragit S 100 concentration in the prepared particles. Most formulations showed sustained release profiles similar to that of a commercial sustained-release liquid based on ion exchange resin. The release pattern indicated strict control of drug release both under gastric and intestinal conditions, suggesting the potential advantage of using a solid dispersion of drug-Eudragit S 100 to overcome the problem of dose dumping after the rupture of the pH dependent alginate gels.

Estimation of the influence of radical effect in the proton beams using a combined approach with physical data and gel data

NASA Astrophysics Data System (ADS)

Haneda, K.

2016-04-01

The purpose of this study was to estimate an impact on radical effect in the proton beams using a combined approach with physical data and gel data. The study used two dosimeters: ionization chambers and polymer gel dosimeters. Polymer gel dosimeters have specific advantages when compared to other dosimeters. They can measure chemical reaction and they are at the same time a phantom that can map in three dimensions continuously and easily. First, a depth-dose curve for a 210 MeV proton beam measured using an ionization chamber and a gel dosimeter. Second, the spatial distribution of the physical dose was calculated by Monte Carlo code system PHITS: To verify of the accuracy of Monte Carlo calculation, and the calculation results were compared with experimental data of the ionization chamber. Last, to evaluate of the rate of the radical effect against the physical dose. The simulation results were compared with the measured depth-dose distribution and showed good agreement. The spatial distribution of a gel dose with threshold LET value of proton beam was calculated by the same simulation code. Then, the relative distribution of the radical effect was calculated from the physical dose and gel dose. The relative distribution of the radical effect was calculated at each depth as the quotient of relative dose obtained using physical and gel dose. The agreement between the relative distributions of the gel dosimeter and Radical effect was good at the proton beams.

Effect of calcium/sodium ion exchange on the osmotic properties and structure of polyelectrolyte gels.

PubMed

Horkay, Ferenc; Basser, Peter J; Hecht, Anne-Marie; Geissler, Erik

2015-12-01

We discuss the main findings of a long-term research program exploring the consequences of sodium/calcium ion exchange on the macroscopic osmotic and elastic properties, and the microscopic structure of representative synthetic polyelectrolyte (sodium polyacrylate, (polyacrylic acid)) and biopolymer gels (DNA). A common feature of these gels is that above a threshold calcium ion concentration, they exhibit a reversible volume phase transition. At the macroscopic level, the concentration dependence of the osmotic pressure shows that calcium ions influence primarily the third-order interaction term in the Flory-Huggins model of polymer solutions. Mechanical tests reveal that the elastic modulus is practically unaffected by the presence of calcium ions, indicating that ion bridging does not create permanent cross-links. At the microscopic level, small-angle neutron scattering shows that polyacrylic acid and DNA gels exhibit qualitatively similar structural features in spite of important differences (e.g. chain flexibility and chemical composition) between the two polymers. The main effect of calcium ions is that the neutron scattering intensity increases due to the decrease in the osmotic modulus. At the level of the counterion cloud around dissolved macroions, anomalous small-angle X-ray scattering measurements made on DNA indicate that divalent ions form a cylindrical sheath enveloping the chain, but they are not localized. Small-angle neutron scattering and small-angle X-ray scattering provide complementary information on the structure and interactions in polymer solutions and gels. © IMechE 2015.

Synthesis and Characterization of Electroresponsive Materials with Applications In: Part I. Second Harmonic Generation. Part II. Organic-Lanthanide Ion Complexes for Electroluminescence and Optical Amplifiers.

NASA Astrophysics Data System (ADS)

Claude, Charles

1995-01-01

Materials for optical waveguides were developed from two different approaches, inorganic-organic composites and soft gel polymers. Inorganic-organic composites were developed from alkoxysilane and organically modified silanes based on nonlinear optical chromophores. Organically modified silanes based on N-((3^' -trialkoxysilyl)propyl)-4-nitroaniline were synthesized and sol-gelled with trimethoxysilane. After a densification process at 190^circC with a corona discharge, the second harmonic of the film was measured with a Nd:YAG laser with a fundamental wavelength of 1064nm, d_{33} = 13pm/V. The decay of the second harmonic was expressed by a stretched bi-exponential equation. The decay time (tau _2) was equal to 3374 hours, and was comparable to nonlinear optical systems based on epoxy/Disperse Orange 1. The processing temperature of the organically modified silane was limited to 200^circC due to the decomposition of the organic chromophore. Soft gel polymers were synthesized and characterized for the development of optical waveguides with dc-electrical field assisted phase-matching. Polymers based on 4-nitroaniline terminated poly(ethylene oxide-co-propylene oxide) were shown to exhibit second harmonic generation that were optically phase-matched in an electrical field. The optical signals were stable and reproducible. Siloxane polymers modified with 1-mercapto-4-nitrobenzene and 1-mercapto-4-methylsulfonylstilbene nonlinear optical chromophores were synthesized. The physical and the linear and nonlinear optical properties of the polymers were characterized. Waveguides were developed from the polymers which were optically phase -matched and had an efficiency of 8.1%. The siloxane polymers exhibited optical phase-matching in an applied electrical field and can be used with a semiconductor laser. Organic lanthanide ion complexes for electroluminescence and optical amplifiers were synthesized and characterized. The complexes were characterized for their thermal and oxidative stability and for their optical properties. Organic-europium ion complexes based on derivatives of 2-benzoyl benzoate are stable to a temperature 70^circ C higher than the europium beta -diketonate complexes. The optical and fluorescence properties of the organic-europium ion complexes were characterized. The methoxy and the t-butyl derivatives of the europium 2-benzoylbenzoate complexes exhibited fluorescence quantum efficiencies that were comparable to europium tris(thenoyl trifluoroacetonate) in methylene chloride but the extinction coefficient was two-thirds of the europium thenoyltrifluoroacetonate complexes. The last complex characterized was the europium bis(diphenylphosphino)imine complex. The complex exhibited thermal stability to 550 ^circC under nitrogen.

Molecular engineering of polymer actuators for biomedical and industrial use

NASA Astrophysics Data System (ADS)

Banister, Mark; Eichorst, Rebecca; Gurr, Amy; Schweitzer, Georgette; Geronov, Yordan; Rao, Pavalli; McGrath, Dominic

2012-04-01

Five key materials engineering components and how each component impacted the working performance of a polymer actuator material are investigated. In our research we investigated the change of actuation performance that occurred with each change we made to the material. We investigated polymer crosslink density, polymer chain length, polymer gelation, type and density of reactive units, as well as the addition of binders to the polymer matrix. All five play a significant role and need to be addressed at the molecular level to optimize a polymer gel for use as a practical actuator material for biomedical and industrial use.

Enhancement of Dose Response and Nuclear Magnetic Resonance Image of PAGAT Polymer Gel Dosimeter by Adding Silver Nanoparticles

PubMed Central

Sabbaghizadeh, Rahim; Shamsudin, Roslinda; Deyhimihaghighi, Najmeh; Sedghi, Arman

2017-01-01

In the present study, the normoxic polyacrylamide gelatin and tetrakis hydroxy methyl phosphoniun chloride (PAGAT) polymer gel dosimeters were synthesized with and without the presence of silver (Ag) nanoparticles. The amount of Ag nanoparticles varied from 1 to 3 ml with concentration 3.14 g/l, thus forming two types of PAGAT polymer gel dosimeters before irradiating them with 6 to 25 Gy produced by 1.25-MeV 60Co gamma rays. In this range, the predominant gamma ray interaction with matter is by Compton scattering effect, as the photoelectric absorption effect diminishes. MRI was employed when evaluating the polymerization of the dosimeters and the gray scale of the MRI film was determined via an optical densitometer. Subsequent analyses of optical densities revealed that the extent of polymerization increased with the increase in the absorbed dose, while the increase of penetration depth within the dosimeters has a reverse effect. Moreover, a significant increase in the optical density-dose response (11.82%) was noted for dosimeters containing 2 ml Ag nanoparticles. PMID:28060829

Isolation and characterization of a mannan from mesosomal membrane vesicles of Micrococcus lysodeikticus.

PubMed

Owen, P; Salton, M R

1975-10-06

The carbohydrate content of mesosomal membranes of Micrococcus lysodeikticus has been shown to be consistently higher (about four times) than that of corresponding plasma membrane preparations. Analysis of washed membrane fractions by gas-liquid chromatography indicated that mannose was the major neutral sugar of both types of membrane (accounting for 95 and 89%, respectively, of the mesosomal and plasma membrane carbohydrate). Small amounts of inositol, glucose and ribose were also detected. We have shown by polyacrylamide gel electrophoresis in sodium dodecylsulphate and by precipitation and agar gel diffusion experiments with concanavalin A that a mannan is the major carbohydrate component of both types of membrane. This polymer can be selectively released from mesosomal membranes by a simple procedure involving low ionic strength-shock and heating to 80 degrees C for 1 min, and purified by ultrafiltration and ethanol precipitation. The mannan contains mannose as the only neutral carbohydrate, is not phosphorylated and does not contain significant amounts of amino sugars or uronic acids. Agar gel electrophoresis experiments, however, indicate an anionic polymer whose acidic properties are eliminated upon mild base hydrolysis. Analysis of native mannan by infrared spectroscopy reveals absorption bands attributable to ester carbonyl groups and to carboxylate ions, consistent with the presence of succinyl residues in the polymer (Owen, P. and Salton, M.R.J. (1975) Biochem, Biophys. Res. Commun. 63, 875--800). A sedimentation coefficient of 1.39 S was obtained by analytical ultracentrifugation in 1.0 M NaCl and a value of one reducing equivalent per 50 mannose residues by reduction with NaB3H4. The polysaccharide was only slightly degraded (2%) by jack bean alpha-mannosidase and could precipitate 15 times its own weight of concanavalin A. The acidic polymers was also detected in the cell "periplasm" and was secreted from cells grown in defined media during the period of decelerating growth.

Water-equivalence of gel dosimeters for radiology medical imaging.

PubMed

Valente, M; Vedelago, J; Chacón, D; Mattea, F; Velásquez, J; Pérez, P

2018-03-08

International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography. Photon mass attenuation coefficients and electron stopping powers were examined. Theoretical, Monte Carlo and experimental results confirmed good water-equivalence for all gel dosimeters. Overall variations with respect to water in the low energy radiology range (up to 130 kVp) were found to be less than 3% in average. Copyright © 2018 Elsevier Ltd. All rights reserved.

pH-Mediated Fluorescent Polymer Particles and Gel from Hyperbranched Polyethylenimine and the Mechanism of Intrinsic Fluorescence.

PubMed

Liu, Shi Gang; Li, Na; Ling, Yu; Kang, Bei Hua; Geng, Shuo; Li, Nian Bing; Luo, Hong Qun

2016-02-23

We report that fluorescence properties and morphology of hyperbranched polyethylenimine (hPEI) cross-linked with formaldehyde are highly dependent on the pH values of the cross-linking reaction. Under acidic and neutral conditions, water-soluble fluorescent copolymer particles (CPs) were produced. However, under basic conditions, white gels with weak fluorescence emission would be obtained. The water-soluble hPEI-formaldehyde (hPEI-F) CPs show strong intrinsic fluorescence without the conjugation to any classical fluorescent agents. By the combination of spectroscopy and microscopy techniques, the mechanism of fluorescence emission was discussed. We propose that the intrinsic fluorescence originates from the formation of a Schiff base in the cross-linking process between hPEI and formaldehyde. Schiff base bonds are the fluorescence-emitting moieties, and the compact structure of hPEI-F CPs plays an important role in their strong fluorescence emission. The exploration on fluorescence mechanism may provide a new strategy to prepare fluorescent polymer particles. In addition, the investigation shows that the hPEI-F CPs hold potential as a fluorescent probe for the detection of copper ions in aqueous media.

Particle-Based Microarrays of Oligonucleotides and Oligopeptides.

PubMed

Nesterov-Mueller, Alexander; Maerkle, Frieder; Hahn, Lothar; Foertsch, Tobias; Schillo, Sebastian; Bykovskaya, Valentina; Sedlmayr, Martyna; Weber, Laura K; Ridder, Barbara; Soehindrijo, Miriam; Muenster, Bastian; Striffler, Jakob; Bischoff, F Ralf; Breitling, Frank; Loeffler, Felix F

2014-10-28

In this review, we describe different methods of microarray fabrication based on the use of micro-particles/-beads and point out future tendencies in the development of particle-based arrays. First, we consider oligonucleotide bead arrays, where each bead is a carrier of one specific sequence of oligonucleotides. This bead-based array approach, appearing in the late 1990s, enabled high-throughput oligonucleotide analysis and had a large impact on genome research. Furthermore, we consider particle-based peptide array fabrication using combinatorial chemistry. In this approach, particles can directly participate in both the synthesis and the transfer of synthesized combinatorial molecules to a substrate. Subsequently, we describe in more detail the synthesis of peptide arrays with amino acid polymer particles, which imbed the amino acids inside their polymer matrix. By heating these particles, the polymer matrix is transformed into a highly viscous gel, and thereby, imbedded monomers are allowed to participate in the coupling reaction. Finally, we focus on combinatorial laser fusing of particles for the synthesis of high-density peptide arrays. This method combines the advantages of particles and combinatorial lithographic approaches.

Particle-Based Microarrays of Oligonucleotides and Oligopeptides

PubMed Central

Nesterov-Mueller, Alexander; Maerkle, Frieder; Hahn, Lothar; Foertsch, Tobias; Schillo, Sebastian; Bykovskaya, Valentina; Sedlmayr, Martyna; Weber, Laura K.; Ridder, Barbara; Soehindrijo, Miriam; Muenster, Bastian; Striffler, Jakob; Bischoff, F. Ralf; Breitling, Frank; Loeffler, Felix F.

2014-01-01

In this review, we describe different methods of microarray fabrication based on the use of micro-particles/-beads and point out future tendencies in the development of particle-based arrays. First, we consider oligonucleotide bead arrays, where each bead is a carrier of one specific sequence of oligonucleotides. This bead-based array approach, appearing in the late 1990s, enabled high-throughput oligonucleotide analysis and had a large impact on genome research. Furthermore, we consider particle-based peptide array fabrication using combinatorial chemistry. In this approach, particles can directly participate in both the synthesis and the transfer of synthesized combinatorial molecules to a substrate. Subsequently, we describe in more detail the synthesis of peptide arrays with amino acid polymer particles, which imbed the amino acids inside their polymer matrix. By heating these particles, the polymer matrix is transformed into a highly viscous gel, and thereby, imbedded monomers are allowed to participate in the coupling reaction. Finally, we focus on combinatorial laser fusing of particles for the synthesis of high-density peptide arrays. This method combines the advantages of particles and combinatorial lithographic approaches. PMID:27600347

Fabrication of chiroptically switchable films via co-gelation of a small chiral gelator with an achiral azobenzene-containing polymer.

PubMed

Yang, Dong; Zhang, Li; Yin, Lu; Zhao, Yin; Zhang, Wei; Liu, Minghua

2017-09-20

Helical polymers are widely found in nature and synthetic functional materials. Although a number of elaborate strategies have been developed to endow polymers with helicity through either covalent bonds or supramolecular techniques, it still remains a challenge to get the desired helical polymers with controlled handedness in an easy but effective manner. In this study, we report an easily accessible gelation-guided self-assembly system where the chirality of a gelator can be easily transferred to an achiral azobenzene-containing polymer during gelation. It is found that during the process of chiral induction, the induced chirality of the polymer was entirely dominated by the molecular chirality of the gelator. Experimentally, achiral azobenzene-containing polymers with different side-chain lengths were doped into a supramolecular gel system formed with amphiphilic N,N'-bis-(octadecyl)-l(d)-Boc-glutamic (LBG-18 or DBG-18 for short). CD spectra and SEM observation confirmed that the co-assembly of polymer/LBG-18 or polymer/DBG-18 in the xerogel state exhibited supramolecular chirality. More importantly, alternate UV and visible light irradiation on the xerogel film caused the induced CD signal to switch between on and off states. Thus a chiroptical switch was fabricated based on the isomerization of the azo-polymer in xerogel films.

Preparation of porous titania film and its application in solar cells.

PubMed

Zhang, Tianhui; Zhao, Suling; Piao, Lingyu; Xu, Zheng; Liu, Xiaodong; Kong, Chao; Xu, Xurong

2011-11-01

Polymer/nanocrystal bulk heterojunction photovoltaic cells have attracted substantial interest because the hybrid active layer combines the advantages of inorganic materials and polymers. In this work, a porous TiO2 was prepared via the sol-gel method with a polyethylene glycol 2000 (PEG2000) template. A kind of polymer/inorganic solar cell based on poly (3-hexylthiophene) (P3HT)/TiO2 was fabricated on the indium-tin-oxide (ITO) glass substrate and the structure of device was ITO/TiO2/P3HT/Au. The device showed the performance with a short circuit current (J(SC)) of 1.29 mA/cm2, an open circuit voltage (V(OC)) of 0.55 V and a fill factor (FF) of 28.7%.

Materials comprising polydienes and hydrophilic polymers and related methods

DOEpatents

Mays, Jimmy W [Knoxville, TN; Deng, Suxiang [Knoxville, TN; Mauritz, Kenneth A [Hattiesburg, MS; Hassan, Mohammad K [Hattiesburg, MS; Gido, Samuel P [Hadley, MA

2011-11-22

Materials prepared from polydienes, such as poly(cyclohexadiene), and hydrophilic polymers, such as poly(alkylene oxide), are described. Methods of making the materials and their use in fuel cell membranes, batteries, breathable chemical-biological protective materials, and templates for sol-gel polymerization are also provided. The materials can be crosslinked and sulfonated, and can include copolymers and polymer blends.

SU-F-T-580: New Tumor Modeling Using 3D Gel Dosimeter for Brain Stereoctactic Radiotherpy (SRT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, K; Kim, M; Kwak, J

Purpose: The purpose of this study is to develop new tumor model using 3D printing with 3D dosimeter for brain stereoctactic radiotherpy (SRT). Methods: BANG{sup 3} polymer gel was prepared and the gel-filled glass vials were irradiated with a 6 MV photon beam to acquire the calibration curve that present the change of R2 (1/T{sub 2}) value with dose. Graded doses from 0 to 12 Gy with an interval of 2 Gy were delivered. A kit for calibration of gel dosimeter and an 2 tumor model phantoms with a spherical shape were produced using a 3D printer with a polylacticmore » acid after its 3D images were created using Autodesk software. 3D printed tumor phantoms and EBT3 films were irradiated to compare with treatment plan. After irradiation, vials for calibration and tumor model phantoms were scanned at 9.4T MRI. The spin-spin relaxation times (T{sub 2}) according to the each dose were calculated to evaluate the dose response. Acquired images were analyzed using an ImageJ. Scanned MRI images of tumor models were transferred treatment planning system and these were registered to the CT images. In all treatment plans, two arc plans (CW and CCW) were designed to deliver 50 Gy for 10 fractions. For first PTV, treatment plan was accurately designed that 95% of dose to cover 100% of PTV. But 2nd PTV was not intentionally cover 100% of PTV to evaluate the intensity of delivered tumor phantom with polymer gel. We compared the 3D dose distributions obtained from measurements with the 3D printed phantom and calculated with the TPS. Results: 3D printed phantom with a polymer gel was successfully produced. The dose distributions showed qualitatively good agreement among gel, film, and RTP data. Conclusion: A hybrid phantom represents a useful to validate the 3D dose distributions for patient-specific QA.« less

Experimental determination of the effect of detector size on profile measurements in narrow photon beams.

PubMed

Pappas, E; Maris, T G; Papadakis, A; Zacharopoulou, F; Damilakis, J; Papanikolaou, N; Gourtsoyiannis, N

2006-10-01

The aim of this work is to investigate experimentally the detector size effect on narrow beam profile measurements. Polymer gel and magnetic resonance imaging dosimetry was used for this purpose. Profile measurements (Pm(s)) of a 5 mm diameter 6 MV stereotactic beam were performed using polymer gels. Eight measurements of the profile of this narrow beam were performed using correspondingly eight different detector sizes. This was achieved using high spatial resolution (0.25 mm) two-dimensional measurements and eight different signal integration volumes A X A X slice thickness, simulating detectors of different size. "A" ranged from 0.25 to 7.5 mm, representing the detector size. The gel-derived profiles exhibited increased penumbra width with increasing detector size, for sizes >0.5 mm. By extrapolating the gel-derived profiles to zero detector size, the true profile (Pt) of the studied beam was derived. The same polymer gel data were also used to simulate a small-volume ion chamber profile measurement of the same beam, in terms of volume averaging. The comparison between these results and actual corresponding small-volume chamber profile measurements performed in this study, reveal that the penumbra broadening caused by both volume averaging and electron transport alterations (present in actual ion chamber profile measurements) is a lot more intense than that resulted by volume averaging effects alone (present in gel-derived profiles simulating ion chamber profile measurements). Therefore, not only the detector size, but also its composition and tissue equivalency is proved to be an important factor for correct narrow beam profile measurements. Additionally, the convolution kernels related to each detector size and to the air ion chamber were calculated using the corresponding profile measurements (Pm(s)), the gel-derived true profile (Pt), and convolution theory. The response kernels of any desired detector can be derived, allowing the elimination of the errors associated with narrow beam profile measurements.

Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

DOEpatents

Mattes, Benjamin R.; Wang, Hsing-Lin

1999-11-09

Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (between 15% and 30% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

Dose of radiation enhancement, using silver nanoparticles in a human tissue equivalent gel dosimeter.

PubMed

Hassan, Muhammad; Waheed, Muhammad Mohsin; Anjum, Muhammad Naeem

2016-01-01

To quantify the radiation dose enhancement in a human tissue-equivalent polymer gel impregnated with silver nanoparticles. The case-control study was conducted at the Bahawalpur Institute of Nuclear Medicine and Oncology, Bahawalpur, Pakistan, in January 2014. Silver nanoparticles used in this study were prepared by wet chemical method. Polymer gel was prepared by known quantity of gelatine, methacrylic acid, ascorbic acid, copper sulphate pentahydrate, hydroquinone and water. Different concentrations of silver nanoparticles were added to the gel during its cooling process. The gel was cooled in six plastic vials of 50ml each. Two vials were used as a control sample while four vials were impregnated with silver nanoparticles. After 22 hours, the vials were irradiated with gamma rays by aCobalt-60 unit. Radiation enhancement was assessed by taking magnetic resonance images of the vials. The images were analysed using Image J software. The dose enhancement factor was 24.17% and 40.49% for 5Gy and 10Gy dose respectively. The dose enhancement factor for the gel impregnated with 0.10mM silver nanoparticles was 32.88% and 51.98% for 5Gy and 10Gy dose respectively. The impregnation of a tissue-equivalent gel with silver nanoparticles resulted in dose enhancement and this effect was magnified up to a certain level with the increase in concentration of silver nanoparticles.

High optical and switching performance electrochromic devices based on a zinc oxide nanowire with poly(methyl methacrylate) gel electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chun, Young Tea; Chu, Daping, E-mail: dpc31@cam.ac.uk; Neeves, Matthew

2014-11-10

High performance electrochromic devices have been fabricated and demonstrated utilizing a solid polymer electrolyte and zinc oxide (ZnO) nanowire (NW) array counter electrode. The poly(methyl methacrylate) based polymer electrolyte was spin coated upon hydrothermally grown ZnO NW array counter electrodes, while electron beam evaporated NiO{sub x} thin films formed the working electrodes. Excellent optical contrast and switching speeds were observed in the fabricated devices with active areas of 2 cm{sup 2}, exhibiting an optical contrast of 73.11% at the wavelength of 470 nm, combined with a fast switching time of 0.2 s and 0.4 s for bleaching and coloration, respectively.

Ionic conductivity and relaxation studies in PVDF-HFP:PMMA-based gel polymer blend electrolyte with LiClO4 salt

NASA Astrophysics Data System (ADS)

Gohel, Khushbu; Kanchan, D. K.

Poly(vinylidene fluoride-hexafluropropylene) (PVDF-HFP) and poly(methyl methacrylate) (PMMA)-based gel polymer electrolytes (GPEs) comprising propylene carbonate and diethyl carbonate mixed plasticizer with variation of lithium perchlorate (LiClO4) salt concentrations have been prepared using a solvent casting technique. Structural characterization has been carried out using XRD wherein diffraction pattern reveals the amorphous nature of sample up to 7.5wt.% salt and complexation of polymers and salt have been studied by FTIR analysis. Surface morphology of the samples has been studied using scanning electron microscope. Electrochemical impedance spectroscopy in the temperature range 303-363K has been carried out for electrical conductivity. The maximum room temperature conductivity of 2.83×10-4S cm-1 has been observed for the GPE incorporating 7.5wt.% LiClO4. The temperature dependence of ionic conductivity obeys the Arrhenius relation. The increase in ionic conductivity with change in temperatures and salt content is observed. Transport number measurement is carried out by Wagner’s DC polarization method. Loss tangent (tan δ) and imaginary part of modulus (M‧‧) corresponding to dielectric relaxation and conductivity relaxation respectively show faster relaxation process with increasing salt content up to optimum value of 7.5wt.% LiClO4. The modulus (M‧‧) shows that the conductivity relaxation is of non-Debye type (broader than Debye peak).

Vapour-phase method in the synthesis of polymer-ibuprofen sodium-silica gel composites.

PubMed

Kierys, Agnieszka; Krasucka, Patrycja; Grochowicz, Marta

2017-11-01

The study discusses the synthesis of polymer-silica composites comprising water soluble drug (ibuprofen sodium, IBS). The polymers selected for this study were poly(TRIM) and poly(HEMA- co -TRIM) produced in the form of permanently porous beads via the suspension-emulsion polymerization method. The acid and base set ternary composites were prepared by the saturation of the solid dispersions of drug (poly(TRIM)-IBS and/or poly(HEMA- co -TRIM)-IBS) with TEOS, and followed by their exposition to the vapour mixture of water and ammonia, or water and hydrochloric acid, at autogenous pressure. The conducted analyses reveal that the internal structure and total porosity of the resulting composites strongly depend on the catalyst which was used for silica precursor gelation. The parameters characterizing the porosity of both of the acid set composites are much lower than the parameters of the base set composites. Moreover, the basic catalyst supplied in the vapour phase does not affect the ibuprofen sodium molecules, whereas the acid one causes transformation of the ibuprofen sodium into the sodium chloride and a derivative of propanoic acid, which is poorly water soluble. The release profiles of ibuprofen sodium from composites demonstrate that there are differences in the rate and efficiency of drug desorption from them. They are mainly affected by the chemical character of the polymeric carrier but are also associated with the restricted swelling of the composites in the buffer solution after precipitation of silica gel.

Synthesis of polymer coated Co0.5Zn0.5Fe2O4 nanoparticles and their enhanced anticancer activity against HepG2 cell line

NASA Astrophysics Data System (ADS)

Ali, Z.; Abbasi, R.; Khan, A. J.; Arshad, J.; Atif, M.; Ahmad, N.; Khalid, W.

2018-05-01

Cobalt zinc ferrite nanoparticles with stoichiometry Co0.5Zn0.5Fe2O4 (CZFN) were synthesized by sol-gel method with high colloidal stability having room temperature ferromagnetism. For biological applications, CZFN were transferred to aqueous phase by polymer coating with amphiphilic polymer, whereas fluorescent dye (ATTO-590) was used as model system for anti-cancer drug loaded polymer shell. The amount of functional molecule varied up to 25% of the anhydride rings, which provides greater affinity of drug loading in polymer shell. CZFN were characterized by x-ray diffraction, Fourier transformed infrared spectroscopy, UV–vis absorption spectroscopy, gel electrophoresis and vibrating sample magnetometer. The in vitro cytotoxicity of CZFN was examined against HepG2 which revealed that CZFN (IC50:3.01 nM) strongly inhabits growth of the cells. Further the particles did not induce any significant hemolysis. Stimulatingly, this seems to be a noteworthy improvement towards the ability of surface functionalized multifunctional CZFN as carriers for drugs for anti-cancer therapy and their use as nanomedicine.

Annular gel reactor for chemical pattern formation

DOEpatents

Nosticzius, Zoltan; Horsthemke, Werner; McCormick, William D.; Swinney, Harry L.; Tam, Wing Y.

1990-01-01

The present invention is directed to an annular gel reactor suitable for the production and observation of spatiotemporal patterns created during a chemical reaction. The apparatus comprises a vessel having at least a first and second chamber separated one from the other by an annular polymer gel layer (or other fine porous medium) which is inert to the materials to be reacted but capable of allowing diffusion of the chemicals into it.

A comparative analysis of modified binders : original asphalts and materials extracted from existing pavements.

DOT National Transportation Integrated Search

2010-01-18

This research demonstrated the application of gel permeation chromatography (GPC) as an analytical tool to : ascertain the amounts of polymer modifiers in polymer modified asphalt cements, which are soluble in eluting GPC : solvents. The technique wa...

A Comparative Analysis of Modified Binders : Original Asphalt and Material Extracted from Existing Pavement

DOT National Transportation Integrated Search

2010-01-18

This research demonstrated the application of gel permeation chromatography (GPC) as an analytical tool to ascertain the amounts of polymer modifiers in polymer modified asphalt cements, which are soluble in eluting GPC solvents. The technique was ap...

Injectable biocompatible and biodegradable pH-responsive hollow particle gels containing poly(acrylic acid): the effect of copolymer composition on gel properties.

PubMed

Halacheva, Silvia S; Adlam, Daman J; Hendow, Eseelle K; Freemont, Tony J; Hoyland, Judith; Saunders, Brian R

2014-05-12

The potential of various pH-responsive alkyl (meth)acrylate ester- and (meth)acrylic acid-based copolymers, including poly(methyl methacrylate-co-acrylic acid) (PMMA-AA) and poly(n-butyl acrylate-co-methacrylic acid) (PBA-MAA), to form pH-sensitive biocompatible and biodegradable hollow particle gel scaffolds for use in non-load-bearing soft tissue regeneration have been explored. The optimal copolymer design criteria for preparation of these materials have been established. Physical gels which are both pH- and redox-sensitive were formed only from PMMA-AA copolymers. MMA is the optimal hydrophobic monomer, whereas the use of various COOH-containing monomers, e.g., MAA and AA, will always induce a pH-triggered physical gelation. The PMMA-AA gels were prepared at physiological pH range from concentrated dispersions of swollen, hollow, polymer-based particles cross-linked with either cystamine (CYS) or 3,3'-dithiodipropionic acid dihydrazide (DTP). A linear relationship between particle swelling ratios, gel elasticity, and ductility was observed. The PMMA-AA gels with lower AA contents feature lower swelling ratios, mechanical strengths, and ductilities. Increasing the swelling ratio (e.g., through increasing AA content) decreased the intraparticle elasticity; however, intershell contact and gel elasticity were found to increase. The mechanical properties and performance of the gels were tuneable upon varying the copolymers' compositions and the structure of the cross-linker. Compared to PMMA-AA/CYS, the PMMA-AA/DTP gels were more elastic and ductile. The biodegradability and cytotoxicity of the new hollow particle gels were tested for the first time and related to their composition, mechanical properties, and morphology. The new PMMA-AA/CYS and PMMA-AA/DTP gels have shown good biocompatibility, biodegradability, strength, and interconnected porosity and therefore have good potential as a tissue repair agent.

Brush-Like Polymers: New Design Platforms for Soft, Dry Materials with Unique Property Relations

NASA Astrophysics Data System (ADS)

Daniel, William Francis McKemie, Jr.

Elastomers represent a unique class of engineering materials due to their light weight, low cost, and desirable combination of softness (105 -107 Pa) and large extensibilities (up to 1000%). Despite these advantages, there exist applications that require many times softer modulus, greater extensibility, and stronger strain hardening for the purpose of mimicking the mechanical properties of systems such as biological tissues. Until recently, only liquid-filled gels were suitable materials for such applications, including soft robotics and implants. A considerable amount of work has been done to create gels with superior properties, but despite unique strengths they also suffer from unique weaknesses. This class of material displays fundamental limitations in the form of heterogeneous structures, solvent loss and phase transitions at extreme temperatures, and loss of liquid fraction upon high deformations. In gels the solvent fraction also introduces a large solvent/polymer interaction parameter which must be carefully considered when designing the final mechanical properties. These energetic considerations further exaggerate the capacity for inconstant mechanical properties caused by fluctuations of the solvent fraction. In order to overcome these weaknesses, a new platform for single component materials with low modulus (<105 Pa) must be developed. Single component systems do not suffer from compositional changes over time and display more stable performance in a wider variety of temperatures and humidity conditions. A solvent-free system also has the potential to be homogeneous which replaces the large energetic interactions with comparatively small architectural interaction parameters. If a solvent-free alternative to liquid-filled gels is to be created, we must first consider the fundamental barrier to softer elastomers, i.e. entanglements - intrinsic topological restrains which define a lower limit of modulus ( 105 Pa). These entanglements are determined by chemistry specific parameters (repeat unit volume and Kuhn segment size) in the polymer liquid (melt) prior to crosslinking. Previous solvent free replacements for gels include elastomers end-linked in semidilute conditions. These materials are generated through crosslinking telechelic polymer chains in semidilute solutions at the onset of chain overlap. At such low polymer concentrations entanglements are greatly diluted and once the resulting gel is dried it creates a supersoft and super-elastic network. Although such methods have successfully generated materials with moduli below the 105 Pa limit and high extensibilities ( 1000%) they present their own limitations. Firstly, the semidilute crosslinking methods uses an impractically large volume of solvent which is unattractive in industry. Second, producing and crosslinking large monodisperse telechelic chains is a nontrivial process leading to large uncertainties in the final network architecture and properties. Specifically, telechelics have a distribution of end-to-end distances and in semidilute solutions with extremely low fraction of chain ends the crosslink reaction is diffusion limited, very slow, and imprecise. In order to achieve a superior solvent-free platform, we propose alteration of mechanical properties through the architectural disentanglement of brush-like polymer structures. In recent year there has been an increase in the synthetic conditions and crosslinking schemes available for producing brush-like structures. This makes brush-like materials an attractive alternative to more restrictive methods such as end-linking. Standard networks have one major control factor outside of chemistry, the network stand length. Brush-like architectures are created from long strands with regularly grafted side chains creating three characteristic length scales which may be independently manipulated. In collaboration with M. Rubinstein, we have utilized bottlebrush polymer architectures (a densely grafted brush-like polymer) to experimentally verify theoretical predictions of disentangled bottlebrush melts. By attaching well-defined side chains onto long polymer backbones, individual polymer strands are separated in space (similar to dilution with solvent) accompanied by a comparatively small increase in the rigidity of the strands. The end result is an architectural disentangled melt with an entanglement plateau modulus as much as three orders of magnitude lower than typical linear polymers and a broadly expanded potential for extensibility once crosslinked.

Swelling-induced optical anisotropy of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate): deswelling kinetics probed by quantitative Mueller matrix polarimetry.

PubMed

Patil, Nagaraj; Soni, Jalpa; Ghosh, Nirmalya; De, Priyadarsi

2012-11-29

Thermodynamically favored polymer-water interactions below the lower critical solution temperature (LCST) caused swelling-induced optical anisotropy (linear retardance) of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate). This was exploited to study the macroscopic deswelling kinetics quantitatively by a generalized polarimetry analysis method, based on measurement of the Mueller matrix and its subsequent inverse analysis via the polar decomposition approach. The derived medium polarization parameters, namely, linear retardance (δ), diattenuation (d), and depolarization coefficient (Δ), of the hydrogels showed interesting differences between the gels prepared by conventional free radical polymerization (FRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) and also between dry and swollen state. The effect of temperature, cross-linking density, and polymerization technique employed to synthesize hydrogel on deswelling kinetics was systematically studied via conventional gravimetry and corroborated further with the corresponding Mueller matrix derived quantitative polarimetry characteristics (δ, d, and Δ). The RAFT gels exhibited higher swelling ratio and swelling-induced optical anisotropy compared to FRP gels and also deswelled faster at 30 °C. On the contrary, at 45 °C, deswelling was significantly retarded for the RAFT gels due to formation of a skin layer, which was confirmed and quantified via the enhanced diattenuation and depolarization parameters.

Electrolyte transport in neutral polymer gels embedded with charged inclusions

NASA Astrophysics Data System (ADS)

Hill, Reghan

2005-11-01

Ion permeable membranes are the basis of a variety of molecular separation technologies, including ion exchange, gel electrophoresis and dialysis. This work presents a theoretical model of electrolyte transport in membranes comprised of a continuous polymer gel embedded with charged spherical inclusions, e.g., biological cells and synthetic colloids. The microstructure mimics immobilized cell cultures, where electric fields have been used to promote nutrient transport. Because several important characteristics can, in principle, be carefully controlled, the theory provides a quantitative framework to help tailor the bulk properties for enhanced molecular transport, microfluidic pumping, and physicochemical sensing applications. This talk focuses on the electroosmotic flow driven by weak electric fields and electrolyte concentration gradients. Also of importance is the influence of charge on the effective ion diffusion coefficients, bulk electrical conductivity, and membrane diffusion potential.

Bio-based topical system for enhanced salicylic acid delivery: preparation and performance of gels.

PubMed

Langasco, Rita; Spada, Gianpiera; Tanriverdi, Sakine Tuncay; Rassu, Giovanna; Giunchedi, Paolo; Özer, Özgen; Gavini, Elisabetta

2016-08-01

New salicylic acid (SA)-loaded gels were developed using excipients made from renewable materials, and our goal was to improve drug permeation in the topical treatment of acne vulgaris. We studied the preparation parameters to obtain suitable gel formulations. Only naturally occurring polymers were used as gelling agents. Two hydrogels and three lipogels were selected and characterized in terms of drug loading, pH, viability cells, rheology, mechanical properties and in vitro permeation; these hydrogels and lipogels were compared with the traditional ointment. We also evaluated skin parameters before and after gel application. The formulations that we studied are non-Newtonian fluids; they have high drug loading and suitable mechanical properties. Lipogels exhibit a slower and more linear in vitro permeation profile compared with hydrogels. The different vehicles that we used affected drug permeation and improve patient compliance. Cytotoxicity studies suggest that all of the formulations are non-toxic. Lipogels demonstrate appropriate technological features and improved performance compared with the traditional ointment with regard to their composition. Lipogels may represent a new bio-based topical system for SA delivery. The use of 'green' excipients leads to 'skin-friendly' formulations that are able to satisfy environmental safety. © 2016 Royal Pharmaceutical Society.

A composite of borohydride and super absorbent polymer for hydrogen generation

NASA Astrophysics Data System (ADS)

Li, Z. P.; Liu, B. H.; Liu, F. F.; Xu, D.

To develop a hydrogen source for underwater applications, a composite of sodium borohydride and super absorbent polymer (SAP) is prepared by ball milling sodium borohydride powder with SAP powder, and by dehydrating an alkaline borohydride gel. When sodium polyacrylate (NaPAA) is used as the SAP, the resulting composite exhibits a high rate of borohydride hydrolysis for hydrogen generation. A mechanism of hydrogen evolution from the NaBH 4-NaPAA composite is suggested based on structure analysis by X-ray diffraction and scanning electron microscopy. The effects of water and NiCl 2 content in the precursor solution on the hydrogen evolution behavior are investigated and discussed.

Magnetization transfer proportion: a simplified measure of dose response for polymer gel dosimetry.

PubMed

Whitney, Heather M; Gochberg, Daniel F; Gore, John C

2008-12-21

The response to radiation of polymer gel dosimeters has most often been described by measuring the nuclear magnetic resonance transverse relaxation rate as a function of dose. This approach is highly dependent upon the choice of experimental parameters, such as the echo spacing time for Carr-Purcell-Meiboom-Gill-type pulse sequences, and is difficult to optimize in imaging applications where a range of doses are applied to a single gel, as is typical for practical uses of polymer gel dosimetry. Moreover, errors in computing dose can arise when there are substantial variations in the radiofrequency (B1) field or resonant frequency, as may occur for large samples. Here we consider the advantages of using magnetization transfer imaging as an alternative approach and propose the use of a simplified quantity, the magnetization transfer proportion (MTP), to assess doses. This measure can be estimated through two simple acquisitions and is more robust in the presence of some sources of system imperfections. It also has a dependence upon experimental parameters that is independent of dose, allowing simultaneous optimization at all dose levels. The MTP is shown to be less susceptible to B1 errors than are CPMG measurements of R2. The dose response can be optimized through appropriate choices of the power and offset frequency of the pulses used in magnetization transfer imaging.

In Situ Forming Polymeric Drug Delivery Systems

PubMed Central

Madan, M.; Bajaj, A.; Lewis, S.; Udupa, N.; Baig, J. A.

2009-01-01

In situ forming polymeric formulations are drug delivery systems that are in sol form before administration in the body, but once administered, undergo gelation in situ, to form a gel. The formation of gels depends on factors like temperature modulation, pH change, presence of ions and ultra violet irradiation, from which the drug gets released in a sustained and controlled manner. Various polymers that are used for the formulation of in situ gels include gellan gum, alginic acid, xyloglucan, pectin, chitosan, poly(DL-lactic acid), poly(DL-lactide-co-glycolide) and poly-caprolactone. The choice of solvents like water, dimethylsulphoxide, N-methyl pyrrolidone, triacetin and 2-pyrrolidone for these formulations depends on the solubility of polymer used. Mainly in situ gels are administered by oral, ocular, rectal, vaginal, injectable and intraperitoneal routes. The in situ gel forming polymeric formulations offer several advantages like sustained and prolonged action in comparison to conventional drug delivery systems. The article presents a detailed review of these types of polymeric systems, their evaluation, advancements and their commercial formulations. From a manufacturing point of view, the production of such devices is less complex and thus lowers the investment and manufacturing cost. PMID:20490289

Poly(ortho esters)--from concept to reality.

PubMed

Heller, Jorge; Barr, John

2004-01-01

The development of poly(ortho esters) dates back to the early 1970s, and during that time, four distinct families were developed. These polymers can be prepared by a transesterification reaction or by the addition of polyols to diketene acetals, and it is the latter method that has proven to be preferred one. The latest polymer, now under intense development, incorporates a latent acid segment in the polymer backbone that takes advantage of the acid-labile nature of the ortho ester linkages and allows control over erosion rates. By use of diols having selected chain flexibility, polymers that range from hard, brittle materials to materials that have a gel-like consistency at room temperature can be obtained. Drug release from solid materials will be illustrated with 5-fluorouacil and bovine serum albumin, and drug release from gel-like materials will be illustrated with mepivacaine, now in Phase II clinical trials as a delivery system to treat post-operative pain. A brief summary of preclinical toxicology studies is also presented.

A High-Energy-Density Potassium Battery with a Polymer-Gel Electrolyte and a Polyaniline Cathode.

PubMed

Gao, Hongcai; Xue, Leigang; Xin, Sen; Goodenough, John B

2018-05-04

A safe, rechargeable potassium battery of high energy density and excellent cycling stability has been developed. The anion component of the electrolyte salt is inserted into a polyaniline cathode upon charging and extracted from it during discharging while the K + ion of the KPF 6 salt is plated/stripped on the potassium-metal anode. The use of a p-type polymer cathode increases the cell voltage. By replacing the organic-liquid electrolyte in a glass-fiber separator with a polymer-gel electrolyte of cross-linked poly(methyl methacrylate), a dendrite-free potassium anode can be plated/stripped, and the electrode/electrolyte interface is stabilized. The potassium anode wets the polymer, and the cross-linked architecture provides small pores of adjustable sizes to stabilize a solid-electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to low-cost potassium batteries for the stationary storage of electric power. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication, characterization, and evaluation of microsponge delivery system for facilitated fungal therapy

PubMed Central

Moin, Afrasim; Deb, Tamal K.; Osmani, Riyaz Ali M.; Bhosale, Rohit R.; Hani, Umme

2016-01-01

Objective: The rationale behind present research vocation was to develop and investigate a novel microsponge based gel as a topical carrier for the prolonged release and cutaneous drug deposition of fluconazole (FLZ); destined for facilitated fungal therapy. Materials and Methods: Microsponges were prepared using quasi-emulsion solvent diffusion method using Eudragit S-100. In the direction of optimization, the effect of formulation variables (drug-polymer ratio and amount of emulsifier) and diverse factors affecting physical characteristics of microsponge were investigated as well. Fabricated microsponges were characterized by differential scanning calorimetry, Fourier transform-infrared, scanning electron microscopy (SEM), particle size analysis, and also evaluated for drug content, encapsulation efficiency, in vitro drug release and in vitro antifungal activity. Results: Compatibility studies results reflected no sign of any chemical interaction between the drug and polymers used. Whereas, varied drug-polymer ratios and emulsifier concentration indicated significant effect on production yield, drug content, encapsulation efficiency, particle size and drug release. Spherical microsponges with a porous surface and 29.327 ± 0.31 μm mean particle size were evident from SEM micrographs. In vitro release outcomes, from microsponge loaded gels depicted that F1 formulation was more efficient to give extended drug release of 85.38% at the end of 8 h, while conventional formulation by releasing 83.17% of drug got exhausted incredibly earlier at the end of 4 h merely. Moreover, microsponge gels demonstrated substantial spreadability and extrudability along with promising antifungal activity. Conclusions: Fabricated microsponges would be impending pharmaceutical topical carriers of FLZ and a leading alternative to conventional therapy for efficient, safe and facilitated eradication of fungal infections. PMID:27057125

Dynamic impact indentation of hydrated biological tissues and tissue surrogate gels

NASA Astrophysics Data System (ADS)

Ilke Kalcioglu, Z.; Qu, Meng; Strawhecker, Kenneth E.; Shazly, Tarek; Edelman, Elazer; VanLandingham, Mark R.; Smith, James F.; Van Vliet, Krystyn J.

2011-03-01

For both materials engineering research and applied biomedicine, a growing need exists to quantify mechanical behaviour of tissues under defined hydration and loading conditions. In particular, characterisation under dynamic contact-loading conditions can enable quantitative predictions of deformation due to high rate 'impact' events typical of industrial accidents and ballistic insults. The impact indentation responses were examined of both hydrated tissues and candidate tissue surrogate materials. The goals of this work were to determine the mechanical response of fully hydrated soft tissues under defined dynamic loading conditions, and to identify design principles by which synthetic, air-stable polymers could mimic those responses. Soft tissues from two organs (liver and heart), a commercially available tissue surrogate gel (Perma-Gel™) and three styrenic block copolymer gels were investigated. Impact indentation enabled quantification of resistance to penetration and energy dissipative constants under the rates and energy densities of interest for tissue surrogate applications. These analyses indicated that the energy dissipation capacity under dynamic impact increased with increasing diblock concentration in the styrenic gels. Under the impact rates employed (2 mm/s to 20 mm/s, corresponding to approximate strain energy densities from 0.4 kJ/m3 to 20 kJ/m3), the energy dissipation capacities of fully hydrated soft tissues were ultimately well matched by a 50/50 triblock/diblock composition that is stable in ambient environments. More generally, the methodologies detailed here facilitate further optimisation of impact energy dissipation capacity of polymer-based tissue surrogate materials, either in air or in fluids.

Polymer Electrolyte Through Enzyme Catalysis for High Performance Lithium-Ion Batteries

DTIC Science & Technology

1998-10-16

by block number) FIELD GROUP SUB-GROUP Polymer Electrolyte, Solid State, Enzyme Catalysis, Lithium - Ion Battery , Sol Gel, High Conductivity 19...excellent candidates for lithium - ion battery development. Furthermore, the processes used to achieve the final product yield very good mechanical properties...Objectives This research was initiated to investigate synthesis of improved polymer electrolytes for lithium - ion battery applications. The overall

Electrostatic polymer-based microdeformable mirror for adaptive optics

NASA Astrophysics Data System (ADS)

Zamkotsian, Frederic; Conedera, Veronique; Granier, Hugues; Liotard, Arnaud; Lanzoni, Patrick; Salvagnac, Ludovic; Fabre, Norbert; Camon, Henri

2007-02-01

Future adaptive optics (AO) systems require deformable mirrors with very challenging parameters, up to 250 000 actuators and inter-actuator spacing around 500 μm. MOEMS-based devices are promising for the development of a complete generation of new deformable mirrors. Our micro-deformable mirror (MDM) is based on an array of electrostatic actuators with attachments to a continuous mirror on top. The originality of our approach lies in the elaboration of layers made of polymer materials. Mirror layers and active actuators have been demonstrated. Based on the design of this actuator and our polymer process, realization of a complete polymer-MDM has been done using two process flows: the first involves exclusively polymer materials while the second uses SU8 polymer for structural layers and SiO II and sol-gel for sacrificial layers. The latest shows a better capability in order to produce completely released structures. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then, we have developed a dedicated 14-bit electronics in order to "linearize" the actuation, using a calibration and a sixth-order polynomial fitting strategy. The response is nearly perfect over our 3×3 MDM prototype with a standard deviation of 3.5 nm; the influence function of the central actuator has been measured. First evaluation on the cross non-linarities has also been studied on OKO mirror and a simple look-up table is sufficient for determining the location of each actuator whatever the locations of the neighbor actuators. Electrostatic MDM are particularly well suited for open-loop AO applications.

Thiolated polymers: evidence for the formation of disulphide bonds with mucus glycoproteins.

PubMed

Leitner, Verena M; Walker, Greg F; Bernkop-Schnürch, Andreas

2003-09-01

Disulphide bonds between thiolated polymers (thiomers) and cysteine-rich subdomains of mucus glycoproteins are supposed to be responsible for the enhanced mucoadhesive properties of thiomers. This study set out to provide evidence for these covalent interactions using poly(acrylic acid)-cysteine conjugates of 2 and 450 kDa (PAA2-Cys, PAA450-Cys) displaying 402.5-776.0 micromol thiol groups per gram polymer. The effect of the disulphide bond breaker cysteine on thiomer-mucin disulphide bonds was monitored by (1) mucoadhesion studies and (2) rheological studies. Furthermore, (3) diffusion studies and (4) gel filtration studies were performed with thiomer-mucus mixtures. The addition of cysteine significantly (P<0.01) reduced the adhesion of thiomer tablets to porcine mucosa and G'/G" values of thiomer-mucin mixtures, whereas unthiolated controls were not influenced. These results indicate the cleavage of disulphide bonds between thiomer and mucus glycoproteins. Diffusion studies demonstrated that a 12.8-fold higher concentration of the thiomer (PAA2-Cys) remains in the mucin gel than the corresponding unmodified polymer. Gel filtration studies showed that PAA2-Cys was able to form disulphide bonds with mucin glycoproteins resulting in an altered elution profile of the mucin/PAA2-Cys mixture in comparison to mucin alone or mucin/PAA2 mixture. According to these results, the study provides evidence for the formation of covalent bonds between thiomer and mucus glycoproteins.

Room-Temperature-Cured Copolymers for Lithium Battery Gel Electrolytes

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Tigelaar, Dean M.

2009-01-01

Polyimide-PEO copolymers (PEO signifies polyethylene oxide) that have branched rod-coil molecular structures and that can be cured into film form at room temperature have been invented for use as gel electrolytes for lithium-ion electric-power cells. These copolymers offer an alternative to previously patented branched rod-coil polyimides that have been considered for use as polymer electrolytes and that must be cured at a temperature of 200 C. In order to obtain sufficient conductivity for lithium ions in practical applications at and below room temperature, it is necessary to imbibe such a polymer with a suitable carbonate solvent or ionic liquid, but the high-temperature cure makes it impossible to incorporate and retain such a liquid within the polymer molecular framework. By eliminating the high-temperature cure, the present invention makes it possible to incorporate the required liquid.

Enzymatic synthesis of lignin-siloxane hybrid functional polymers.

PubMed

Prasetyo, Endry Nugroho; Kudanga, Tukayi; Fischer, Roman; Eichinger, Reinhard; Nyanhongo, Gibson S; Guebitz, Georg M

2012-02-01

This study combines the properties of siloxanes and lignin polymers to produce hybrid functional polymers that can be used as adhesives, coating materials, and/or multifunctionalized thin-coating films. Lignin-silica hybrid copolymers were synthesized by using a sol-gel process. Laccases from Trametes hirsuta were used to oxidize lignosulphonates to enhance their reactivity towards siloxanes and then were incorporated into siloxane precursors undergoing a sol-gel process. In vitro copolymerization studies using pure lignin monomers with aminosilanes or ethoxytrimethylsilane and analysis by ²⁹Si NMR spectroscopy revealed hybrid products. Except for kraft lignin, an increase in lignin concentration positively affected the tensile strength in all samples. Similarly, the viscosity generally increased in all samples with increasing lignin concentration and also affected the curing time. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel Detox Gel Depot sequesters β-Amyloid Peptides in a mouse model of Alzheimer's Disease.

PubMed

Sundaram, Ranjini K; Kasinathan, Chinnaswamy; Stein, Stanley; Sundaram, Pazhani

2012-06-01

Alzheimer's Disease (AD), a debilitating neurodegenerative disease is caused by aggregation and accumulation of a 39-43 amino acid peptide (amyloid β or Aβ) in brain parenchyma and cerebrovasculature. The rational approach would be to use drugs that interfere with Aβ-Aβ interaction and disrupt polymerization. Peptide ligands capable of binding to the KLVFF (amino acids 16-20) region in the Aβ molecule have been investigated as possible drug candidates. Retro-inverso (RI) peptide of this pentapeptide, ffvlk, has been shown to bind artificial fibrils made from Aβ with moderate affinity. We hypothesized that a 'detox gel', which is synthesized by covalently linking a tetrameric version of RI peptide ffvlk to poly (ethylene glycol) polymer chains will act like a 'sink' to capture Aβ peptides from the surrounding environment. We previously demonstrated that this hypothesis works in an in vitro system. The present study extended this hypothesis to an in vivo mouse model of Alzheimer's Disease and determined the therapeutic effect of our detox gel. We injected detox gel subcutaneously to AD model mice and analyzed brain levels of Aβ-42 and improvement in memory parameters. The results showed a reduction of brain amyloid burden in detox gel treated mice. Memory parameters in the treated mice improved. No undesirable immune response was observed. The data strongly suggest that our detox gel can be used as an effective therapy to deplete brain Aβ levels. Considering recent abandonment of failed antibody based therapies, our detox gel appears to have the advantage of being a non-immune based therapy.

Gel polymer electrolytes based on nanofibrous polyacrylonitrile–acrylate for lithium batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Dul-Sun; Woo, Jang Chang; Youk, Ji Ho, E-mail: youk@inha.ac.kr

2014-10-15

Graphical abstract: - Highlights: • Nanofibrous polyacrylonitrile–acrylate membranes were prepared by electrospinning. • Trimethylolpropane triacrylate was used as a crosslinking agent of fibers. • The GPE based on PAN–acrylate (1/0.5) showed good electrochemical properties. - Abstract: Nanofibrous membranes for gel polymer electrolytes (GPEs) were prepared by electrospinning a mixture of polyacrylonitrile (PAN) and trimethylolpropane triacrylate (TMPTA) at weight ratios of 1/0.5 and 1/1. TMPTA is used to achieve crosslinking of fibers thereby improving mechanical strength. The average fiber diameters increased with increasing TMPTA concentration and the mechanical strength was also improved due to the enhanced crosslinking of fibers. GPEs basedmore » on electrospun membranes were prepared by soaking them in a liquid electrolyte of 1 M LiPF{sub 6} in ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1, v/v). The electrolyte uptake and ionic conductivity of GPEs based on PAN and PAN–acrylate (weight ratio; 1/1 and 1/0.5) were investigated. Ionic conductivity of GPEs based on PAN–acrylate was the highest for PAN/acrylate (1/0.5) due to the proper swelling of fibers and good affinity with liquid electrolyte. Both GPEs based on PAN and PAN–acrylate membranes show good oxidation stability, >5.0 V vs. Li/Li{sup +}. Cells with GPEs based on PAN–acrylate (1/0.5) showed remarkable cycle performance with high initial discharge capacity and low capacity fading.« less

Charge-regularized swelling kinetics of polyelectrolyte gels

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

The swelling kinetics of polyelectrolyte gels with fixed and variable degrees of ionization in salt-free solvent is studied by solving the constitutive equation of motion of the spatially and temporally varying displacement variable. Two methods for the swelling kinetics - the Bulk Modulus Method (BMM), which uses a linear stress-strain relationship (and, hence a bulk modulus), and the Stress Relaxation Method (SRM), which uses a phenomenological expression of osmotic stress, are explored to provide the spatio-temporal profiles for polymer density, osmotic stress, and degree of ionization, along with the time evolution of the gel size. Further, we obtain an analytical expression for the elastic modulus for linearized stress in the limit of small deformations. We match our theoretical profiles with the experiments of swelling of PNIPAM (uncharged) and Imidazolium-based (charged) minigels available in the literature. Ministry of Human Resource Development (MHRD), Government of India.

Soft particles at a fluid interface

NASA Astrophysics Data System (ADS)

Mehrabian, Hadi; Harting, Jens; Snoeijer, Jacco H.

2015-11-01

Particles added to a fluid interface can be used as a surface stabilizer in the food, oil and cosmetic industries. As an alternative to rigid particles, it is promising to consider highly deformable particles that can adapt their conformation at the interface. In this study, we compute the shapes of soft elastic particles using molecular dynamics simulations of a cross-linked polymer gel, complemented by continuum calculations based on the linear elasticity. It is shown that the particle shape is not only affected by the Young's modulus of the particle, but also strongly depends on whether the gel is partially or completely wetting the fluid interface. We find that the molecular simulations for the partially wetting case are very accurately described by the continuum theory. By contrast, when the gel is completely wetting the fluid interface the linear theory breaks down and we reveal that molecular details have a strong influence on the equilibrium shape.

Facile and green preparation of novel adsorption materials by combining sol-gel with ion imprinting technology for selective removal of Cu(II) ions from aqueous solution

NASA Astrophysics Data System (ADS)

Ren, Zhongqi; Zhu, Xinyan; Du, Jian; Kong, Delong; Wang, Nian; Wang, Zhuo; Wang, Qi; Liu, Wei; Li, Qunsheng; Zhou, Zhiyong

2018-03-01

A novel green adsorption polymer was prepared by ion imprinted technology in conjunction with sol-gel process under mild conditions for the selective removal of Cu(II) ions from aqueous solution. Effects of preparation conditions on adsorption performance of prepared polymers were studied. The ion-imprinted polymer was prepared using Cu(II) ion as template, N-[3-(2-aminoethylamino) propyl] trimethoxysilane (AAPTMS) as functional monomer and tetraethyl orthosilicate (TEOS) as cross-linker. Water was used as solvent in the whole preparation process. The imprinted and non-imprinted polymers were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM), Brunauer, Emmett and Teller (BET) and zeta potential. Three-dimensional network structure was formed and functional monomer was successfully cross-linked into the network structure of polymers. Effects of adsorption conditions on adsorption performance of prepared polymers were studied too. The pH value is of great influence on adsorption behavior. Adsorption by ion-imprinted polymer was fast (adsorption equilibrium was reached within 60 min). The adsorption capacity of Cu(II) ion-imprinted polymer was always larger than that of non-imprinted polymer. Pseudo-second-order kinetics model and Freundlich isotherm model fitted well with adsorption data. The maximum adsorption capacity of Cu(II) ion-imprinted polymer was 39.82 mg·g-1. However, the preparation conditions used in this work are much milder than those reported in literatures. The Cu(II) ion-imprinted polymer showed high selectivity and relative selectivity coefficients for Pb(II), Ni(II), Cd(II) and Co(II). In addition, the prepared ion-imprinted polymer could be reused several times without significant loss of adsorption capacity.