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Sample records for controlled radical polymerization

  1. Graphene oxide as a radical initiator: Free radical and controlled radical polymerization of sodium 4-vinylbenzenesulfonate with graphene oxide

    DOE PAGESBeta

    Voylov, Dmitry N.; Saito, Tomonori; Lokitz, Bradley S.; Uhrig, David; Wang, Yangyang; Agapov, Alexander L.; Holt, Adam P.; Bocharova, Vera; Kisliuk, Alexander; Sokolov, Alexei P.

    2016-01-19

    The free radical and controlled radical polymerization of sodium 4-vinylbenzenesulfonate using graphene oxide as a radical initiator was studied. This work demonstrates that graphene oxide can initiate radical polymerization in an aqueous solution without any additional initiator. Poly(sodium 4-vinylbenzenesulfonate) obtained via reversible addition fragmentation chain transfer polymerization had a controlled molecular weight with a very narrow polydispersity ranging between 1.01 and 1.03. Furthermore, the reduction process of graphene oxide as well as the resulting composite material properties were analyzed in detail.

  2. Application of Controlled Radical Polymerization for Nucleic Acid Delivery

    PubMed Central

    CHU, DAVID S.H.; SCHELLINGER, JOAN G.; SHI, JULIE; CONVERTINE, ANTHONY J.; STAYTON, PATRICK S.; PUN, SUZIE H.

    2012-01-01

    CONSPECTUS Nucleic acid-based therapeutics can potentially address otherwise untreatable genetic disorders and have significant potential for a wide range of diseases. Therapeutic gene delivery can restore protein function by replacing defunct genes to restore cellular health while RNA interference (RNAi) can mask mutated and harmful genes. Cationic polymers have been extensively studied for nucleic acid delivery applications due to their self-assembly with nucleic acids into virus-sized nanoparticles and high transfection efficiency in vitro, but toxicity and particle stability have limited their clinical applications. The advent of controlled radical polymerization has improved the quality, control and reproducibility of synthesized materials. Controlled radical polymerization yields well-defined, narrowly disperse materials of designable architectures and molecular weight, allowing study of the effects of polymer architecture and molecular weight on transfection efficiency and cytotoxicity for improved design of next-generation vectors. Robust methods such as atom transfer radical polymerization (ATRP), reverse addition-fragmentation chain transfer polymerization (RAFT), and ring-opening metastasis polymerization (ROMP) have been used to engineer materials that specifically enhance extracellular stability, cellular specificity, and decrease toxicity. This Account reviews findings from structure-function studies that have elucidated key design motifs necessary for the development of effective nucleic acid vectors. In addition, polymers that are biodegradable, form supramolecular structures, target specific cells, or facilitate endosomal release are also discussed. Finally, promising materials with in vivo applications ranging from pulmonary gene delivery to DNA vaccines are described. PMID:22242774

  3. Photomediated Controlled Radical Polymerization and Block Copolymerization of Vinylidene Fluoride.

    PubMed

    Asandei, Alexandru D

    2016-02-24

    This review summarizes recent research on novel photochemical methods for the initiation and control of the polymerization of main chain fluorinated monomers as exemplified by vinylidene fluoride (VDF) and for the synthesis of their block copolymers. Such reactions can be carried out at ambient temperature in glass tubes using visible light. Novel, original protocols include the use of hypervalent iodide carboxylates alone or in conjunction with molecular iodine, as well as the use of photoactive transition metal carbonyls in the presence of alkyl, fluoroalkyl, and perfluoroalkyl halides. An in-depth study of the reaction parameters highlights the use of dimethyl carbonate as a preferred polymerization solvent and outlines the structure-property relationship for hypervalent iodide carboxylates and halide initiators in both the free radical and iodine degenerative transfer controlled radical polymerization (IDT-CRP) of VDF. Finally, the rational selection of metal carbonyls that are successful not only as IDT mediators but, more importantly, in the quantitative activation of both PVDF-CH2-CF2-I and PVDF-CF2-CH2-I chain ends toward the synthesis of well-defined PVDF block copolymers is presented. PMID:26760676

  4. Photo-Regeneration of Severed Gel Using Photo-Controlled Radical Polymerization

    NASA Astrophysics Data System (ADS)

    Singh, Awaneesh; Kuksenok, Olga; Johnson, Jeremiah A.; Balazs, Anna C.

    Using the framework of dissipative particle dynamics (DPD) simulation, we developed a novel computational model that enables photo-regeneration of the gel matrix when a significant portion of the material is severed. We considered photo-controlled radical polymerization (photo-CRP) within polymer networks with embedded iniferters (initiators for the photo-CRP reaction). These iniferters turn on the polymerization process in the presence of light with monomers and cross-linkers in the solution. This ''photo-growth'' allow us to effectively regenerate severed gels under the application of light. The growth process can be turned off once the polymerization is near completion, which forms a new cross-linked gel that resembles the uncut material. The polymerization rate can be modulated by altering the light intensity.

  5. Tailoring the Structure of Polymer Networks with Photo-Controlled Radical Polymerization

    NASA Astrophysics Data System (ADS)

    Singh, Awaneesh; Kuksenok, Olga; Johnson, Jeremiah A.; Balazs, Anna C.

    Using dissipative particle dynamics (DPD) approach, we developed a novel computational model to study the photo-controlled radical polymerization (photo-CRP) within polymer networks with embedded iniferters. The polymerization process can be turned ``on'' or ``off'' in response to light and the polymerization rate can be modulated by altering the light intensity. This ``photo-growth'' approach allows us to impart changes in the gel network pore size and composition to form photo-tunable smart materials. For example, our approach allows us to design gel composites that are comprised of two distinct layers made of two compatible components at low photo-iniferter concentrations or gel composites that are comprised of two incompatible components that are relatively well intermixed at high photo-iniferter concentration.

  6. Radical-Mediated Enzymatic Polymerizations

    PubMed Central

    Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  7. Radical-Mediated Enzymatic Polymerizations.

    PubMed

    Zavada, Scott R; Battsengel, Tsatsral; Scott, Timothy F

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes--catalytic proteins--owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol-ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  8. Recyclable Crosslinked Polymer Networks via One-Step Controlled Radical Polymerization.

    PubMed

    Jin, Kailong; Li, Lingqiao; Torkelson, John M

    2016-08-01

    A nitroxide-mediated polymerization strategy allows one-step synthesis of recyclable crosslinked polymeric materials from any monomers or polymers that contain carbon-carbon double bonds amenable to radical polymerization. The resulting materials with dynamic covalent bonds can show full property recovery after multiple melt-reprocessing recycles. This one-step strategy provides for both robust, relatively sustainable recyclability of crosslinked polymers and design of networks for advanced technologies. PMID:27206061

  9. Controlled synthesis of photochromic polymer brushes by atom transfer radical polymerization.

    SciTech Connect

    Piech, Marcin; Bell, Nelson Simmons; Long, Timothy Michael

    2005-06-01

    This work reports on the grafting of methyl methacrylate polymer brushes containing spirobenzopyran pendant groups from flat silica surfaces and colloidal particles utilizing atom transfer radical polymerization (ATRP). The reaction conditions were optimized with respect to the kind of surface bound initiator, the type of halide and ligand used in the catalytic complex, the presence/absence of untethered initiator, and solvent type. This enabled synthesis of coatings up to 80 {+-} 3 nm thick with controlled spirobenzopyran content. While polymerization kinetics indicate the presence of chain termination reactions, the 'living' character of the process is confirmed by controlled formation of block copolymer brushes. UV/vis spectroscopy was used to characterize the UV-induced isomerization of spirobenzopyran to zwitterionic merocyanine and the thermal back-reaction. Spectral and kinetic analyses of this latter bleaching process points to the existence of free and associated merocyanines in the polymeric brush in both tetrahydrofuran and toluene. However, stabilization of merocyanine species by the polymer matrix is considerably greater in toluene with thermal back-reaction rates approaching those determined for solid dry films.

  10. Modular and Versatile Spatial Functionalization of Tissue Engineering Scaffolds through Fiber‐Initiated Controlled Radical Polymerization

    PubMed Central

    Harrison, Rachael H.; Steele, Joseph A. M.; Chapman, Robert; Gormley, Adam J.; Chow, Lesley W.; Mahat, Muzamir M.; Podhorska, Lucia; Palgrave, Robert G.; Payne, David J.; Hettiaratchy, Shehan P.; Dunlop, Iain E.

    2015-01-01

    Native tissues are typically heterogeneous and hierarchically organized, and generating scaffolds that can mimic these properties is critical for tissue engineering applications. By uniquely combining controlled radical polymerization (CRP), end‐functionalization of polymers, and advanced electrospinning techniques, a modular and versatile approach is introduced to generate scaffolds with spatially organized functionality. Poly‐ε‐caprolactone is end functionalized with either a polymerization‐initiating group or a cell‐binding peptide motif cyclic Arg‐Gly‐Asp‐Ser (cRGDS), and are each sequentially electrospun to produce zonally discrete bilayers within a continuous fiber scaffold. The polymerization‐initiating group is then used to graft an antifouling polymer bottlebrush based on poly(ethylene glycol) from the fiber surface using CRP exclusively within one bilayer of the scaffold. The ability to include additional multifunctionality during CRP is showcased by integrating a biotinylated monomer unit into the polymerization step allowing postmodification of the scaffold with streptavidin‐coupled moieties. These combined processing techniques result in an effective bilayered and dual‐functionality scaffold with a cell‐adhesive surface and an opposing antifouling non‐cell‐adhesive surface in zonally specific regions across the thickness of the scaffold, demonstrated through fluorescent labelling and cell adhesion studies. This modular and versatile approach combines strategies to produce scaffolds with tailorable properties for many applications in tissue engineering and regenerative medicine. PMID:27134621

  11. Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide

    PubMed Central

    2014-01-01

    We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a ‘grafting from’ technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures (Tg) than those of pristine PMMA. PMID:25114639

  12. Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Chung, Jin Suk; Hur, Seung Hyun

    2014-07-01

    We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a `grafting from' technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures ( T g) than those of pristine PMMA.

  13. Controlled radical polymerization of an acrylamide containing L-alanine moiety via ATRP.

    PubMed

    Rafiee, Zahra

    2016-02-01

    Homopolymerization of an optically active acrylamide having an amino acid moiety in the side chain, N-acryloyl-L-alanine (AAla) was carried out via atom transfer radical polymerization (ATRP) at room temperature using 2-hydroxyethyl-2'-methyl-2'-bromopropionate (HMB) or sodium-4-(bromomethyl)benzoate (SBB) as initiator in pure water, methanol/water mixture and pure methanol solvents. The polymerization reaction resulted in the optically active biocompatible amino acid-based homopolymer in good yield with narrow molecular weight distribution. The number average molecular weight increased with conversion and polydispersity was low. The structure and molecular weight of synthesized polymer were characterized by (1)H NMR, FT-IR spectroscopic techniques and size-exclusion chromatography. PMID:26385362

  14. Nonspherical nanoparticles with controlled morphologies via seeded surface-initiated single electron transfer radical polymerization in soap-free emulsion.

    PubMed

    Yuan, Jinfeng; Wang, Lixia; Zhu, Lei; Pan, Mingwang; Wang, Wenjie; Liu, Ying; Liu, Gang

    2015-04-14

    This work reports a facile novel approach to prepare asymmetric poly(vinylidene fluoride)/polystyrene (PVDF/PS) composite latex particles with controllable morphologies using one-step soap-free seeded emulsion polymerization, i.e., surface-initiated single electron transfer radical polymerization (SET-RP) of styrene (St) at the surface of PVDF seed particles. It was observed that the morphology was influenced mainly by the St/PVDF feed ratio, the polymerization temperature, and the length of the catalyst Cu(0) wire (Φ 1.00 mm). When the feed ratio was St/PVDF = 5.0 g/1.0 g, snowman-like Janus particles were exclusively obtained. Raspberry-like and popcorn-like composite particles were observed at a higher reaction temperature or a shorter length of the catalyst wire. The reaction kinetics plots demonstrated some unique features. The formation of nonspherical composite nanoparticles can be ascribed to the surface nucleation of PS bulges following the SET-RP. PMID:25797695

  15. Spatial control over brush growth through sunlight-induced atom transfer radical polymerization using dye-sensitized TiO2 as a photocatalyst.

    PubMed

    Li, Bin; Yu, Bo; Zhou, Feng

    2014-07-01

    Simulated-sunlight induced atom transfer radical polymerization is used for spatial control over polymer brush growth by in situ photo-generation of the Cu(I) /L activator complex from its higher oxidation state Cu(II) /L deactivator complex using dye sensitized titanium dioxide nano-particles. The polymerization is well controlled under sunlight irradiation. Another attractive feature of this method is the possibility of creating various patterned surfaces of brushes using photomasks. When a nanoporous alumina oxide membrane is used as the template for confinement diffusion of photogenerated Cu(I) /L catalyst, patterns with sub-50 nm resolution are obtained. PMID:24740888

  16. Micropatterned Surfaces for Atmospheric Water Condensation via Controlled Radical Polymerization and Thin Film Dewetting.

    PubMed

    Wong, Ian; Teo, Guo Hui; Neto, Chiara; Thickett, Stuart C

    2015-09-30

    Inspired by an example found in nature, the design of patterned surfaces with chemical and topographical contrast for the collection of water from the atmosphere has been of intense interest in recent years. Herein we report the synthesis of such materials via a combination of macromolecular design and polymer thin film dewetting to yield surfaces consisting of raised hydrophilic bumps on a hydrophobic background. RAFT polymerization was used to synthesize poly(2-hydroxypropyl methacrylate) (PHPMA) of targeted molecular weight and low dispersity; spin-coating of PHPMA onto polystyrene films produced stable polymer bilayers under appropriate conditions. Thermal annealing of these bilayers above the glass transition temperature of the PHPMA layer led to complete dewetting of the top layer and the formation of isolated PHPMA domains atop the PS film. Due to the vastly different rates of water nucleation on the two phases, preferential dropwise nucleation of water occurred on the PHPMA domains, as demonstrated by optical microscopy. The simplicity of the preparation method and ability to target polymers of specific molecular weight demonstrate the value of these materials with respect to large-scale water collection devices or other materials science applications where patterning is required. PMID:26372163

  17. Controlled/Living Radical Polymerization in the Undergraduate Laboratories. 1. Using ATRP to Prepare Block and Statistical Copolymers of n-Butyl Acrylate and Styrene

    NASA Astrophysics Data System (ADS)

    Beers, Kathryn L.; Woodworth, Brian; Matyjaszewski, Krzysztof

    2001-04-01

    A simple method of preparing well-defined (co)polymers has been developed for application in an advanced undergraduate laboratory. The method utilizes atom transfer radical polymerization (ATRP), a controlled/living radical polymerization, to prepare difunctional poly(n-butyl acrylate) with bromine end groups, which is chain-extended with styrene to yield an ABA triblock copolymer. Simultaneously, a statistical copolymer of the two monomers is prepared for comparison. The two copolymers are isolated and compositions and molecular weights are determined using 1H NMR and SEC, respectively. Optional additions to the experiment include performing a kinetic analysis of the homopolymerization using GC and SEC, and possibly comparing the results to those expected for conventional radical polymerization. Material differences in the copolymers can be observed qualitatively or measured using thermal or mechanical analysis. The lab is designed in such a way that several parts of the whole can be used to emphasize different areas of polymer science. A more synthetic course such as the organic synthesis lab can opt to investigate only the kinetic and composition analyses, whereas an engineering or materials science course may pursue more rigorous analysis of the materials' properties. Results included here are intended for application in an organic synthesis laboratory course.

  18. Atom Transfer Radical Polymerization of Methacrylic Acid: A Won Challenge.

    PubMed

    Fantin, Marco; Isse, Abdirisak A; Venzo, Alfonso; Gennaro, Armando; Matyjaszewski, Krzysztof

    2016-06-15

    Polymerization of acidic monomers is one of the biggest challenges for atom transfer radical polymerization (ATRP). An intramolecular cyclization reaction leading to the loss of the C-X chain-end functionality was found to be the main reason for the partial termination of the growing polymer chains. Three approaches were used to overcome this problem: using Cl as the chain-end halogen, lowering the pH (to 0.9), and increasing polymerization rate. Methacrylic acid (MAA) was polymerized by both electrochemically mediated ATRP and supplemental activator and reducing agent ATRP up to high conversion (>90%), in t ≤ 4 h at 25 °C, using inexpensive and nontoxic reagents (NaCl, diluted HCl, water). Control over molecular weight (MW) dispersity was satisfactory, and MWs were in agreement with theoretical values. The "livingness" of the process was confirmed by an electrochemical switch, used to repeatedly and periodically deactivate/reactivate growing chains. PMID:27244091

  19. Ultraviolet/Ozone as a Tool To Control Grafting Density in Surface-Initiated Controlled-Radical Polymerizations via Ablation of Bromine.

    PubMed

    Sheridan, Richard J; Orski, Sara V; Muramoto, Shin; Stafford, Christopher M; Beers, Kathryn L

    2016-08-16

    We used an ultraviolet-ozone (UVO) cleaner to create substrates for atom-transfer radical polymerization (ATRP) with varying surface initiator coverage. We collected complementary time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) measurements to investigate the precise chemical origin of the variation in grafting density. At short exposure times, the atomic composition underwent minor changes except for the relative amount of bromine. At longer UVO exposure times, there is clear evidence of exposure-dependent surface initiator oxidation. We interpret these data as evidence of a bromine ablation process within the UVO cleaner, with additional oxidative modification of the rest of the surface. We then used these substrates to create a series of poly(methyl methacrylate) (PMMA) brushes varying in grafting density, demonstrating the utility of this tool for the control of polymer brush density. The measured brush grafting densities were correlated with the bromine concentration measured by both ToF-SIMS and XPS. XPS and brush thicknesses correlated strongly, following an exponential decay with a half-life of 18 ± 1 s. PMID:27442615

  20. ATOM TRANSFER RADICAL POLYMERIZATION OF N-BUTYL METHACRYLATE IN AQUEOUS DISPERSED SYSTEMS: A MINIEMULSION APPROACH. (R826735)

    EPA Science Inventory

    Ultrasonication was applied in combination with a hydrophobe for the copper-mediated atom transfer radical polymerization of n-butyl methacrylate in an aqueous dispersed system. A controlled polymerization was successfully achieved, as demonstrated by a linear correlation between...

  1. Organocatalyzed atom transfer radical polymerization driven by visible light.

    PubMed

    Theriot, Jordan C; Lim, Chern-Hooi; Yang, Haishen; Ryan, Matthew D; Musgrave, Charles B; Miyake, Garret M

    2016-05-27

    Atom transfer radical polymerization (ATRP) has become one of the most implemented methods for polymer synthesis, owing to impressive control over polymer composition and associated properties. However, contamination of the polymer by the metal catalyst remains a major limitation. Organic ATRP photoredox catalysts have been sought to address this difficult challenge but have not achieved the precision performance of metal catalysts. Here, we introduce diaryl dihydrophenazines, identified through computationally directed discovery, as a class of strongly reducing photoredox catalysts. These catalysts achieve high initiator efficiencies through activation by visible light to synthesize polymers with tunable molecular weights and low dispersities. PMID:27033549

  2. Single Electron Transfer Living Radical Polymerization via a New Initiator

    NASA Astrophysics Data System (ADS)

    Bai, Xiongxiong; Hu, Ying; Zhang, Xu; Ai, Lingling; Cheng, Chuanjie

    2014-08-01

    Research and development of novel initiating system such as single electron transfer living radical polymerization (SET-LRP) is of high importance in polymer chemistry. A new SET-LRP initiator was synthesized and applied to prepare end-functionalized poly(methyl methacrylate) (PMMA) in this study. α-Trichloromethyl benzyl alcohol was firstly synthesized, followed by preparation of PMMA under SET-LRP conditions. Conversion of MMA was 81.9%, and the molecular weight of PMMA was about 2.5 kDa at 60 °C for 1 h. Consistency of the number-average molecular weight of PMMA from NMR, GPC and theoretical calculation indicated that the polymerization featured controllable property. Broad molecular weight distribution (MWD) may be ascribed to branched polymers formed by initiation and chain transfer.

  3. Biomimetic radical polymerization via cooperative assembly of segregating templates

    NASA Astrophysics Data System (ADS)

    McHale, Ronan; Patterson, Joseph P.; Zetterlund, Per B.; O'Reilly, Rachel K.

    2012-06-01

    Segregation and templating approaches have been honed by billions of years of evolution to direct many complex biological processes. Nature uses segregation to improve biochemical control by organizing reactants into defined, well-regulated environments, and the transfer of genetic information is a primary function of templating. The ribosome, wherein messenger RNA is translated into polypeptides, combines both techniques to allow for ideal biopolymer syntheses. Herein is presented a biomimetic segregation/templating approach to synthetic radical polymerization. Polymerization of a nucleobase-containing vinyl monomer in the presence of a complementary block copolymer template of low molecular weight yields high molecular weight (Mw up to ~400,000 g mol-1), extremely low polydispersity (≤1.08) daughter polymers. Control is attained by segregation of propagating radicals in discrete micelle cores (via cooperative assembly of dynamic template polymers). Significantly reduced bimolecular termination, combined with controlled propagation along a defined number of templates, ensures unprecedented control to afford well-defined high molecular weight polymers.

  4. Macromolecular engineering by atom transfer radical polymerization.

    PubMed

    Matyjaszewski, Krzysztof; Tsarevsky, Nicolay V

    2014-05-01

    This Perspective presents recent advances in macromolecular engineering enabled by ATRP. They include the fundamental mechanistic and synthetic features of ATRP with emphasis on various catalytic/initiation systems that use parts-per-million concentrations of Cu catalysts and can be run in environmentally friendly media, e.g., water. The roles of the major components of ATRP--monomers, initiators, catalysts, and various additives--are explained, and their reactivity and structure are correlated. The effects of media and external stimuli on polymerization rates and control are presented. Some examples of precisely controlled elements of macromolecular architecture, such as chain uniformity, composition, topology, and functionality, are discussed. Syntheses of polymers with complex architecture, various hybrids, and bioconjugates are illustrated. Examples of current and forthcoming applications of ATRP are covered. Future challenges and perspectives for macromolecular engineering by ATRP are discussed. PMID:24758377

  5. pH-responsive controlled-release fertilizer with water retention via atom transfer radical polymerization of acrylic acid on mussel-inspired initiator.

    PubMed

    Ma, Zhi-yuan; Jia, Xin; Zhang, Guo-xiang; Hu, Jia-mei; Zhang, Xiu-lan; Liu, Zhi-yong; Wang, He-yun; Zhou, Feng

    2013-06-12

    This work reports a polydopamine-graft-poly(acrylic acid) (Pdop-g-PAA)-coated controlled-release multi-element compound fertilizer with water-retention function by a combination of mussel-inspired chemistry and surface-initiated atom transfer radical polymerization (SI-ATRP) techniques for the first time. The morphology and composition of the products were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography (GPC), and inductively coupled plasma (ICP) emission spectrometry. The results revealed that the stimuli-responsive layer formed by a Pdop inner layer and a PAA outer corona exhibit outstanding selective permeability to charged nutrients and the release rate of encapsulated elements can be tailored by the pH values. At low pH, the Pdop-g-PAA layer can reduce nutrient loss, and at high pH, the coating restrains transportation of negative nutrients but favors the release of cations. Moreover, PAA brushes provide good water-retention property. This Pdop-graft-polymer brushes coating will be effective and promising in the research and development of multi-functional controlled-release fertilizer. PMID:23692274

  6. Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst.

    PubMed

    Theriot, Jordan C; Ryan, Matthew D; French, Tracy A; Pearson, Ryan M; Miyake, Garret M

    2016-01-01

    A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism. PMID:27166728

  7. Radical Polymerization of Vinyl Monomers in Porous Organic Cages.

    PubMed

    Uemura, Takashi; Nakanishi, Ryo; Mochizuki, Shuto; Kitagawa, Susumu; Mizuno, Motohiro

    2016-05-23

    The radical polymerization of vinyl monomers was performed in a tetrahedral imine-linked organic cage with extrinsic porosity (CC3). Because of its dynamic and responsive packing structure, CC3 endowed the polymerization with specific behaviors. The adsorption of styrene triggered a change in the CC3 assembly, resulting in a monomer arrangement that was suitable for polymerization within the host matrix. The polymerization reaction was strongly dependent on the crystallinity of CC3 and was promoted by amorphization of the host in a cooperative manner, which is not possible with conventional rigid porous materials. Furthermore, CC3 can recognize the polarity of substrates, and thus polar monomers, such as methyl methacrylate and acrylonitrile, could not induce the structural changes in CC3 that are required for polymerization. This monomer specificity governed by the flexibility of CC3 is useful to the prevent incorporation of unfavorable monomers into the polymeric products. PMID:27027409

  8. A chaperonin as protein nanoreactor for atom-transfer radical polymerization.

    PubMed

    Renggli, Kasper; Nussbaumer, Martin G; Urbani, Raphael; Pfohl, Thomas; Bruns, Nico

    2014-01-27

    The group II chaperonin thermosome (THS) from the archaea Thermoplasma acidophilum is reported as nanoreactor for atom-transfer radical polymerization (ATRP). A copper catalyst was entrapped into the THS to confine the polymerization into this protein cage. THS possesses pores that are wide enough to release polymers into solution. The nanoreactor favorably influenced the polymerization of N-isopropyl acrylamide and poly(ethylene glycol)methylether acrylate. Narrowly dispersed polymers with polydispersity indices (PDIs) down to 1.06 were obtained in the protein nanoreactor, while control reactions with a globular protein-catalyst conjugate only yielded polymers with PDIs above 1.84. PMID:24459061

  9. Controlled/Living Radical Polymerization in the Undergraduate Laboratories. 2. Using ATRP in Limited Amounts of Air to Prepare Block and Statistical Copolymers of n-Butyl Acrylate and Styrene

    NASA Astrophysics Data System (ADS)

    Matyjaszewski, Krzysztof; Beers, Kathryn L.; Woodworth, Brian; Metzner, Zachary

    2001-04-01

    Developments in controlled radical polymerization have facilitated the use of living polymer chemistry in the undergraduate laboratories. In the first paper of this series, a procedure for the use of atom transfer radical polymerization (ATRP) to prepare block and statistical copolymers was described and the use of kinetic analysis to differentiate between living and conventional processes was demonstrated. In this paper, the experiment is extended to polymerizations run in limited amounts of air so that the use of inert gases is unnecessary. The Cu(I) catalyst can be lost owing to oxidation or termination reactions; however, a scavenger, Cu(0), is added to react with oxidized catalyst to regenerate the Cu(I) complex. A difunctional macroinitiator of poly(n-butyl acrylate) is prepared and chain-extended with polystyrene. A statistical copolymer using the same monomer pair is also prepared. These copolymers are isolated and characterized along with the homopolymeric macroinitiator using 1H NMR and SEC. Kinetic analysis is also carried out using GC and SEC. The significant difference in these two approaches, in addition to slight variations in the reaction conditions, is apparent in the chain extension to yield the ABA triblock copolymer.

  10. Novel Patterned Films by Free-Radical Polymerization Techniques

    NASA Astrophysics Data System (ADS)

    Ward, Jennifer H.; Peppas, Nicholas A.

    2000-03-01

    We have developed novel techniques for the preparation of micropatterned structures by the block copolymerization of thin layers using UV free-radical polymerizations. The process involves polymerizing the first layer in the presence of an iniferter (initiator-transfer agent-terminator) with a dithiocarbamate group to make a photosensitive polymer. Upon application of a second monomer layer on the first polymer layer and irradiation, a copolymer is formed between the two layers. Patterns are created on the films by applying a mask and selectively irradiating the surface. Applications of this type of material are in biomaterials and biosensors for the selective adhesion of cells and proteins. We have successfully polymerized poly(ethylene glycol) (PEG) onto a layer of poly(methyl methacrylate) (PMMA) in the presence of tetraethylthiuran disulfide. Cells will adhere to the exposed PMMA areas but not to the PEG surfaces. This work has been supported by National Science Foundation grant No. DGE-9972770.

  11. Fluorescent dye-labelled polymer synthesis by nitroxide mediated radical polymerization

    NASA Astrophysics Data System (ADS)

    Kollár, Jozef; Chmela, Štefan; Hrčková, Ľudmila; Hrdlovič, Pavol

    2012-07-01

    New applications of polymers at advanced technologies demand increased requirements on their properties. These properties are influenced by molecular as well as supramolecular structure. Controlled radical polymerization mediated by stable nitroxides (NMP) or substituted alkoxyamines offers simple method for preparation of polymers with programmable structure of macromolecules which possess remarkable better physical as well as chemical properties. They can be used as a macro initiators for the synthesis of block copolymers. At the present time it has been generally accepted that the extent of "livingness" is high for all conversions [1-4]. To verify this statement a series of fluorescent dye-labelled regulators has been synthesized, spectrally characterized and used as the mediators of styrene and n-butyl acrylate polymerization. Direct quantification of dormant species concentration (extent of livingness) and calculation of molar mass of marked polymers was performed by absorption and/or emission spectroscopy. Controlled radical polymerization mediated by stable nitroxides bearing fluorescence mark represents unconventional approach for monitoring and evaluation of mechanism and kinetics of polymerization process. Results indicate that the extent of livingness is strongly influenced by conversion as well as mediator concentration. There is a clear tendency toward to decreasing amount of dormant species with increasing monomer conversion. Moreover, lower mediator concentration decreases livingness of polymerization process.

  12. Surface Grafting via Photo-Induced Copper-Mediated Radical Polymerization at Extremely Low Catalyst Concentrations.

    PubMed

    Laun, Joachim; Vorobii, Mariia; de los Santos Pereira, Andres; Pop-Georgievski, Ognen; Trouillet, Vanessa; Welle, Alexander; Barner-Kowollik, Christopher; Rodriguez-Emmenegger, Cesar; Junkers, Thomas

    2015-09-01

    Surface-initiated photo-induced copper-mediated radical polymerization is employed to graft a wide range of polyacrylate brushes from silicon substrates at extremely low catalyst concentrations. This is the first time that the controlled nature of the reported process is demonstrated via block copolymer formation and re-initiation experiments. In addition to unmatched copper catalyst concentrations in the range of few ppb, film thicknesses up to almost 1 μm are achieved within only 1 h. PMID:26149622

  13. Surface active properties of polyoxyethylene macromonomers and their role in radical polymerization in disperse systems.

    PubMed

    Capek, I

    2000-12-26

    Conventional dispersion polymerization and copolymerization of low-molecular weight (conventional) unsaturated monomers allows preparation of monodisperse and micronsize polymer particles. A similar behavior can be found in the surfactant-free dispersion polymerization of non-traditional vinyl monomers, unsaturated macromonomers. The latter systems allow preparation of random, comb-like, star-like and graft copolymers as well. An interesting alternative arises with the use of amphiphilic reactive macromonomers that contain a polymerizable group and aggregate into an organized structure -- a micelle. Under such conditions the high rate of polymerization and ultrafine (microparticles) polymer dispersions are generated. Thus, the surface-active macromonomers promote the formation of micelles and polymer growth within the main reaction loci -- polymer particles. Furthermore, the surface-active compounds can be formed during the copolymerization of hydrophilic macromonomer and hydrophobic low-molecular weight comonomer. The reactive surface-active oligomeric radicals are incorporated into the polymer matrix or the particle surface layer, which prevents them from subsequent migration. Besides, the covalently bound surface-active groups at the particle surface strongly increase the colloidal stability of final polymer dispersion. This article presents a review of the current literature in the field of the surfactant-free dispersion polymerization of the polyoxyethylene unsaturated macromonomers. Besides a short introduction into some kinetic aspects of radical polymerization of traditional monomers in homogeneous and disperse systems, we mainly focus on the organized aggregation of amphiphilic polyoxyethylene macromonomers, the characterization of amphiphilic graft copolymers and their aggregation properties, and radical copolymerization of polyoxyethylene macromonomers. We discuss the birth and growth of chains, the transfer of reaction loci from the continuous phase to

  14. Radical initiated polymerization in a bifunctional mixture via computer simulation

    NASA Astrophysics Data System (ADS)

    Diamond, Keri L.; Pandey, Ras B.; Thames, Shelby F.

    2004-06-01

    Computer simulations are performed to study the polymerization behavior in a mixture of bifunctional groups such as olefins (A) and acrylates (B) in an effective solvent (a coarse description for vegetable oil derived macromonomers (VOMMs) in solution) on a cubic lattice. A set of interactions between these units and solvent (S) constituents and their relative concentrations (pA, pB, and pS) are considered. Samples are equilibrated with Metropolis algorithm to model the perceived behavior of VOMMs. The covalent bonding between monomeric units is then implemented via reaction pathways initiated by stochastic motion of free radicals (a very small fraction). The rate of reaction shows decay patterns with the time steps (t) with power laws (i.e., Rabαt-r, r≅0.4-0.8), exponential decays (i.e., Rabαe-0.001t), and their combination. Growth of A-B bonding is studied as a function of polymer concentration p=pA+pB for four different model systems appropriate for VOMMs. The data from the free radical initiated simulations are compared to the original simulations with homopolymerization. While most of the data are consistent with experimental observations, the variations are found to be model dependent.

  15. Precision design of ethylene- and polar-monomer-based copolymers by organometallic-mediated radical polymerization.

    PubMed

    Kermagoret, Anthony; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

    2014-03-01

    The copolymerization of ethylene with polar monomers is a major challenge when it comes to the manufacture of materials with potential for a wide range of commercial applications. In the chemical industry, free-radical polymerization is used to make a large proportion of such copolymers, but the forcing conditions result in a lack of fine control over the architecture of the products. Herein we introduce a synthetic tool, effective under mild experimental conditions, for the precision design of unprecedented ethylene- and polar-monomer-based copolymers. We demonstrate how an organocobalt species can control the growth of the copolymer chains, their composition and the monomer distribution throughout the chain. By fine tuning the ethylene pressure during polymerization and by exploiting a unique reactive mode of the end of the organometallic chain, novel block-like copolymer structures can be prepared. This highly versatile synthetic platform provides access to a diverse range of polymer materials. PMID:24557131

  16. Precision design of ethylene- and polar-monomer-based copolymers by organometallic-mediated radical polymerization

    NASA Astrophysics Data System (ADS)

    Kermagoret, Anthony; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

    2014-03-01

    The copolymerization of ethylene with polar monomers is a major challenge when it comes to the manufacture of materials with potential for a wide range of commercial applications. In the chemical industry, free-radical polymerization is used to make a large proportion of such copolymers, but the forcing conditions result in a lack of fine control over the architecture of the products. Herein we introduce a synthetic tool, effective under mild experimental conditions, for the precision design of unprecedented ethylene- and polar-monomer-based copolymers. We demonstrate how an organocobalt species can control the growth of the copolymer chains, their composition and the monomer distribution throughout the chain. By fine tuning the ethylene pressure during polymerization and by exploiting a unique reactive mode of the end of the organometallic chain, novel block-like copolymer structures can be prepared. This highly versatile synthetic platform provides access to a diverse range of polymer materials.

  17. Antibacterial polypropylene via surface-initiated atom transfer radical polymerization.

    PubMed

    Huang, Jinyu; Murata, Hironobu; Koepsel, Richard R; Russell, Alan J; Matyjaszewski, Krzysztof

    2007-05-01

    Polypropylene (PP) coated by a non-leachable biocide was prepared by chemically attaching poly(quaternary ammonium) (PQA) to the surface of PP. The well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), a precursor of PQA, was grown from the surface of PP via atom transfer radical polymerization (ATRP). The tertiary ammine groups in PDMAEMA were consequently converted to QA in the presence of ethyl bromide. Successful surface modification was confirmed by ATR-FTIR, contact angle measurement, and an antibacterial activity test against Escherichia coli (E. coli). The biocidal activity of the resultant surfaces depends on the amount of the grafted polymers (the number of available quaternary ammonium units). With the same grafting density, the surface grafted with relatively high MW polymers (M(n) > 10,000 g/mol) showed almost 100% killing efficiency (killing all of the input E. coli (2.9 x 10(5)) in the shaking test), whereas a low biocidal activity (85%) was observed for the surface grafted with shorter PQA chains (M(n) = 1,500 g/mol). PMID:17417906

  18. Bio-Based Polyketones by Selective Ring-Opening Radical Polymerization of α-Pinene-Derived Pinocarvone.

    PubMed

    Miyaji, Hisanari; Satoh, Kotaro; Kamigaito, Masami

    2016-01-22

    The most abundant naturally occurring terpene, α-pinene, which cannot be directly polymerized into high polymers by any polymerization method, was quantitatively converted under visible-light irradiation into pinocarvone, which possesses a reactive exo methylene group. The bicyclic vinyl ketone was quantitatively polymerized in fluoroalcohols by selective (99%) ring-opening radical polymerization of the four-membered ring, which results in unique polymers containing chiral six-membered rings with conjugated ketone units in the main chain. These polymers display good thermal properties, optical activities, and contain reactive conjugated ketone units. Reversible addition fragmentation chain transfer (RAFT) polymerization was successfully accomplished by using appropriate trithiocarbonate RAFT agents, enabling the synthesis of thermoplastic elastomers based on controlled macromolecular architectures. PMID:26663490

  19. Recent developments in atom transfer radical polymerization (ATRP): methods to reduce metal catalyst concentrations.

    PubMed

    Lou, Qin; Shipp, Devon A

    2012-10-01

    Atom transfer radical polymerization (ATRP) was initially developed in the mid-1990s, and with continued refinement and use has led to significant discoveries in new materials. However, metal contamination of the polymer product is an issue that has proven detrimental to widespread industrial application of ATRP. The laboratories of K. Matyjaszewski have made significant progress towards removing this impediment, leading the development of "activators regenerated by electron transfer" ATRP (ARGET ATRP) and electrochemically mediated ATRP (eATRP) technologies. These variants of ATRP allow polymers to be produced with great molecular weight and functionality control but at significantly reduced catalyst concentrations, typically at parts per million levels. This Concept examines these polymerizations in terms of their mechanism and outcomes, and is aimed at giving the reader an overview of recent developments in the field of ATRP. PMID:22539367

  20. Development of Initiation Strategies for the Optimization and Stabilization of Brushes Formed by Surface-Initiated Radical Polymerization

    NASA Astrophysics Data System (ADS)

    Bain, Erich D.

    Three challenges facing the continued development of the surface-initiated (SI) polymerization field are addressed. The first challenge is that surface-initiated free radical polymerization (SI-FRP) is currently under-represented in literature reports, despite the fact that SI-FRP offers several important advantages over surface-initiated controlled radical polymerization (SI-CRP) and represents a complementary approach. Recognizing that simple, efficient, and safer approaches to synthesizing effective surface free radical initiators are needed, we present a novel synthetic route to an azo type free radical initiator that forms self-assembled monolayers on oxide coated surfaces such as silicon and glass. The yield of the novel synthetic approach is approximately double that of the previous method, and the usage of cyanide is reduced dramatically. We characterize the decomposition kinetics of the initiator using differential scanning calorimetry, comparing it with other similar initiators. We characterize the surface properties of initiator layers on silicon using ellipsometry, water contact angle measurements, and x-ray photoelectron spectroscopy (XPS). We demonstrate the use of the initiator for SI-FRP as well as SI-CRP mechanisms including reverse atom transfer radical polymerization (RATRP) and reversible addition-fragmentation transfer (RAFT) polymerization. A second challenge facing the field of SI polymerization involves the stability of grafted polymer brushes in aqueous environments and under tension, both of which are commonly encountered in many applications. We hypothesize that the mechanism of brush degrafting involves hydrolysis of ester backbone units in the initiator, which are ubiquitous in surface-bound polymerization initiator systems. The novel initiator described herein is unique in that its backbone consists of a chemically stable alkane chain, free of esters or other easily hydrolysable groups. We present results of experiments demonstrating

  1. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, Douglas B.; Shahinpoor, Mohsen; Segalman, Daniel J.; Witkowski, Walter R.

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

  2. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

    1993-10-05

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

  3. Interfacial/free radical polymerization microencapsulation: kinetics of particle formation.

    PubMed

    Mahabadi, H K; Ng, T H; Tan, H S

    1996-01-01

    Microcapsules containing pigment and polymer were prepared by dispersing a viscous mixture of pigment, core monomers, initiators and oil-soluble shell monomer in an aqueous solution of surfactants, forming oil-in-water droplets. Subsequently, a water-soluble shell monomer was added to these droplets, encapsulating them via interfacial (IF) polycondensation. These microcapsules were then heated for free radical (FR) polymerization of the core monomers. Effects of primary variables, such as the shearing time during particle formation, surfactant concentration, organic phase concentration, and mode of water-soluble shell monomer addition, were studied. The results indicated that polyvinylalcohol (PVOH), used as the surfactant/stabilizer, reacted with the oil-soluble shell monomers. The depletion of PVOH, especially when PVOH concentration was low, resulted in rapid growth of particle size and, eventually, suspension failure. The kinetic data revealed a particle formation mechanism which consists of two processes. The first process is the formation of an equilibrium particle size by the equilibrium process of particle breakage due to the mechanical shearing force and coalescence due to collisions among particles and surface tension forces. The second process is the reaction between PVOH and oil-soluble shell monomer which leads to the depletion of PVOH and consequently causes more coalescence of particles and a significant increase in the equilibrium particle size. The net effect of these two processes shows an optimum shearing time where the smallest particle size can be attained, and this optimum time is a function of several primary variables. Methods to prevent the reaction and therefore the depletion of PVOH are proposed. PMID:8864993

  4. Ring-opening metathesis polymerization of 18-e Cobalt(I)-containing norbornene and application as heterogeneous macromolecular catalyst in atom transfer radical polymerization.

    PubMed

    Yan, Yi; Zhang, Jiuyang; Wilbon, Perry; Qiao, Yali; Tang, Chuanbing

    2014-11-01

    In the last decades, metallopolymers have received great attention due to their various applications in the fields of materials and chemistry. In this article, a neutral 18-electron exo-substituted η(4) -cyclopentadiene CpCo(I) unit-containing polymer is prepared in a controlled/"living" fashion by combining facile click chemistry and ring-opening meta-thesis polymerization (ROMP). This Co(I)-containing polymer is further used as a heterogeneous macromolecular catalyst for atom transfer radical polymerization (ATRP) of methyl methacrylate and styrene. PMID:25250694

  5. Free radical polymerization of poly(ethylene glycol) diacrylate macromers: impact of macromer hydrophobicity and initiator chemistry on polymerization efficiency.

    PubMed

    Dai, Xiaoshu; Chen, Xi; Yang, Laura; Foster, Sarah; Coury, Arthur J; Jozefiak, Thomas H

    2011-05-01

    A series of poly(ethylene glycol)-co-poly(lactide) diacrylate macromers was synthesized with variable PEG molecular weights (10 or 20 kDa) and lactate contents (0 or 6 lactates per end group). These macromers were polymerized to form hydrogels by free radical polymerization using either redox or photochemical initiators. The extent of polymerization was determined by monitoring the compressive modulus of the resulting hydrogels and by quantitative determination of unreacted acrylate after exhaustive hydrolysis of the gel. Polymerization efficiency was found to depend on the lactate content of the macromer, with higher lactate macromers giving more efficient polymerization. For redox-initiated polymerization using ferrous gluconate/t-butyl hydroperoxide initiator, macromers containing approximately six lactate repeats per end group required lower concentrations of initiator to reach high conversion than lactate-free macromers. Photochemical polymerization with α,α-dimethoxy-α-phenylacetophenone (Irgacure 651(®)) was found to be less efficient than redox polymerization, requiring the addition of N-vinyl-2- pyrrolidone (NVP) as a co-monomer to achieve conversions comparable with redox polymerization. When conditions were optimized to provide near complete conversion for all gels, the presence of lactate repeat units in the hydrogel was generally found to reduce swelling and increase the compressive modulus. Calculated values of molecular weight between cross-links (M(c)) and mesh size using Flory-Rehner theory showed that macromer molecular weight had the greatest impact on the network structure of the gel. PMID:21232638

  6. Facile Soap-Free Miniemulsion Polymerization of Methyl Methacrylate via Reverse Atom Transfer Radical Polymerization.

    PubMed

    Zhu, Gaohua; Zhang, Lifen; Pan, Xiangqiang; Zhang, Wei; Cheng, Zhenping; Zhu, Xiulin

    2012-12-21

    A facile soap-free miniemulsion polymerization of methyl methacrylate (MMA) was successfully carried out via a reverse ATRP technique, using a water-soluble potassium persulfate (KPS) or 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V-50) both as the initiator and the stabilizer, and using an oil-soluble N,N-n-butyldithiocarbamate copper (Cu(S2CN(C4H9)2)2) as the catalyst without adding any additional ligand. Polymerization results demonstrated the "living"/controlled characteristics of ATRP and the resultant latexes showed good colloidal stability with average particle size around 300-700 nm in diameter. The monomer droplet nucleation mechanism was proposed. NMR spectroscopy and chain-extension experiments under UV light irradiation confirmed the attachment and livingness of UV light sensitive -S-C(=S)-N(C4H9)2 group in the chain end. PMID:23019131

  7. Free Radical Polymerization of Styrene: A Radiotracer Experiment

    ERIC Educational Resources Information Center

    Mazza, R. J.

    1975-01-01

    Describes an experiment designed to acquaint the chemistry student with polymerization reactions, vacuum techniques, liquid scintillation counting, gas-liquid chromatography, and the handling of radioactive materials. (MLH)

  8. Polyacrylamide grafting of modified graphene oxides by in situ free radical polymerization

    SciTech Connect

    Tang, Mingyi; Xu, Xiaoyang; Wu, Tao; Zhang, Sai; Li, Xianxian; Li, Yi

    2014-12-15

    Highlights: • Graphene oxide (GO) was modified by chemical reactions to functionalized GO (FGO). • The FGOs and the GO were then subjected to in situ free radical polymerization. • Hydroxyl groups of GO were the most reactive grafting sites. - Abstract: Graphene oxide (GO) was modified using chemical reactions to obtain three types of functionalized GO sheets (FGO). The FGO sheets and the GO were then subjected to in situ free radical polymerization in order to study the grafting polymerization. The FGO and grafted-.FGO were analyzed with Fourier transform infrared spectroscopy, scanning electronic microscopy, thermo-gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The grafting percentages in the materials were calculated using the TGA and XPS results. The FGO sheets with different functional groups exhibited different grafting abilities, and hydroxyl groups were proven to be the most reactive grafting sites for the in situ free radical grafting polymerization of polyacrylamide.

  9. Free Radical Polymerization of Styrene and Methyl Methacrylate in Various Room Temperature Ionic Liquids

    SciTech Connect

    Zhang, Hongwei; Hong, Kunlun; Mays, Jimmy

    2005-01-01

    Conventional free radical polymerization of styrene and methyl methacrylate was carried out in various room temperature ionic liquids (RTILs). The RTILs used in this research encompass a wide range of cations and anions. Typical cations include imidazolium, phosphonium, pyridinium, and pyrrolidinium; typical anions include amide, borate, chloride, imide, phosphate, and phosphinate. Reactions are faster and polymers obtained usually have higher molecular weights when compared to polymerizations carried out in volatile organic solvents under the same conditions. This shows that rapid rates of polymerization and high molecular weights are general features of conventional radical polymerizations in RTILs. Attempts to correlate the polarities and viscosities of the RTILs with the polymerization behavior fail to yield discernible trends.

  10. Free-radical solution-polymerization of trifluoronitrosomethane with tetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Gdickman, S. A.

    1972-01-01

    Heavy-walled glass reactor, equipped with aerosol-compatible couplings and needle valve and charged with solvent and initiator, is utilized for polymerization. Polymer conversions and reactor/vessel operation are discussed.

  11. A novel solid state photocatalyst for living radical polymerization under UV irradiation

    NASA Astrophysics Data System (ADS)

    Fu, Qiang; McKenzie, Thomas G.; Ren, Jing M.; Tan, Shereen; Nam, Eunhyung; Qiao, Greg G.

    2016-02-01

    This study presents the development of a novel solid state photocatalyst for the photoinduced controlled radical polymerization of methacrylates under mild UV irradiation (λmax ≈ 365 nm) in the absence of conventional photoinitiators, metal-catalysts or dye sensitizers. The photocatalyst design was based on our previous finding that organic amines can act in a synergistic photochemical reaction with thiocarbonylthio compounds to afford well controlled polymethacrylates under UV irradiation. Therefore, in the current contribution an amine-rich polymer was covalently grafted onto a solid substrate, thus creating a heterogeneous catalyst that would allow for facile removal, recovery and recyclability when employed for such photopolymerization reactions. Importantly, the polymethacrylates synthesized using the solid state photocatalyst (ssPC) show similarly excellent chemical and structural integrity as those catalysed by free amines. Moreover, the ssPC could be readily recovered and re-used, with multiple cycles of polymerization showing minimal effect on the integrity of the catalyst. Finally, the ssPC was employed in various photo-“click” reactions, permitting high yielding conjugations under photochemical control.

  12. A novel solid state photocatalyst for living radical polymerization under UV irradiation.

    PubMed

    Fu, Qiang; McKenzie, Thomas G; Ren, Jing M; Tan, Shereen; Nam, Eunhyung; Qiao, Greg G

    2016-01-01

    This study presents the development of a novel solid state photocatalyst for the photoinduced controlled radical polymerization of methacrylates under mild UV irradiation (λmax ≈ 365 nm) in the absence of conventional photoinitiators, metal-catalysts or dye sensitizers. The photocatalyst design was based on our previous finding that organic amines can act in a synergistic photochemical reaction with thiocarbonylthio compounds to afford well controlled polymethacrylates under UV irradiation. Therefore, in the current contribution an amine-rich polymer was covalently grafted onto a solid substrate, thus creating a heterogeneous catalyst that would allow for facile removal, recovery and recyclability when employed for such photopolymerization reactions. Importantly, the polymethacrylates synthesized using the solid state photocatalyst (ssPC) show similarly excellent chemical and structural integrity as those catalysed by free amines. Moreover, the ssPC could be readily recovered and re-used, with multiple cycles of polymerization showing minimal effect on the integrity of the catalyst. Finally, the ssPC was employed in various photo-"click" reactions, permitting high yielding conjugations under photochemical control. PMID:26863939

  13. A novel solid state photocatalyst for living radical polymerization under UV irradiation

    PubMed Central

    Fu, Qiang; McKenzie, Thomas G.; Ren, Jing M.; Tan, Shereen; Nam, Eunhyung; Qiao, Greg G.

    2016-01-01

    This study presents the development of a novel solid state photocatalyst for the photoinduced controlled radical polymerization of methacrylates under mild UV irradiation (λmax ≈ 365 nm) in the absence of conventional photoinitiators, metal-catalysts or dye sensitizers. The photocatalyst design was based on our previous finding that organic amines can act in a synergistic photochemical reaction with thiocarbonylthio compounds to afford well controlled polymethacrylates under UV irradiation. Therefore, in the current contribution an amine-rich polymer was covalently grafted onto a solid substrate, thus creating a heterogeneous catalyst that would allow for facile removal, recovery and recyclability when employed for such photopolymerization reactions. Importantly, the polymethacrylates synthesized using the solid state photocatalyst (ssPC) show similarly excellent chemical and structural integrity as those catalysed by free amines. Moreover, the ssPC could be readily recovered and re-used, with multiple cycles of polymerization showing minimal effect on the integrity of the catalyst. Finally, the ssPC was employed in various photo-“click” reactions, permitting high yielding conjugations under photochemical control. PMID:26863939

  14. Sustainable Electrochemically-Mediated Atom Transfer Radical Polymerization with Inexpensive Non-Platinum Electrodes.

    PubMed

    Fantin, Marco; Lorandi, Francesca; Isse, Abdirisak A; Gennaro, Armando

    2016-08-01

    Electrochemically-mediated atom transfer radical polymerization (eATRP) of oligo(ethylene oxide) methyl ether methacrylate in water is investigated on glassy carbon, Au, Ti, Ni, NiCr and SS304. eATRPs are performed both in divided and undivided electrochemical cells operating under either potentiostatic or galvanostatic mode. The reaction is fast, reaching high conversions in ≈4 h, and yields polymers with dispersity <1.2 and molecular weights close to the theoretical values. Most importantly, eATRP in a highly simplified setup (undivided cell under galvanostatic mode) with inexpensive nonnoble metals, such as NiCr and SS304, as cathode is well-controlled. Additionally, these electrodes neither release harmful ions in solution nor react directly with the CX chain end and can be reused several times. It is demonstrated that Pt can be replaced with cheaper, and more readily available materials without negatively affecting eATRP performance. PMID:27333068

  15. Lewis-Acid-Mediated Stereospecific Radical Polymerization of Acrylimides Bearing Chiral Oxazolidinones.

    PubMed

    Fujita, Takehiro; Yamago, Shigeru

    2015-12-14

    Lewis acid (MgBr2)-catalyzed radical polymerization of acrylimides bearing chiral oxazolidinones gave highly isotactic polyacrylimides with up to >99% meso tetrad (mmm) selectivity. Polymerization in the absence of Lewis acid gave atactic polymers with 80% racemo diad (r) selectivity; the selectivity was deliberately tuned from 80% r to >99% mmm by varying the polymerization conditions. The polyacrylimide was quantitatively converted to corresponding polyacrylates while preserving the stereoregularity, thus providing a general method for the synthesis of atactic to isotactic polyacrylates. PMID:26500040

  16. Key role of intramolecular metal chelation and hydrogen bonding in the cobalt-mediated radical polymerization of N-vinyl amides.

    PubMed

    Debuigne, Antoine; Morin, Aurélie N; Kermagoret, Anthony; Piette, Yasmine; Detrembleur, Christophe; Jérôme, Christine; Poli, Rinaldo

    2012-10-01

    This work reveals the preponderance of an intramolecular metal chelation phenomenon in a controlled radical polymerization system involving the reversible trapping of the radical chains by a cobalt complex bis(acetylacetonato)cobalt(II). The cobalt-mediated radical polymerization (CMRP) of a series of N-vinyl amides was considered with the aim of studying the effect of the cobalt chelation by the amide moiety of the last monomer unit of the chain. The latter reinforces the cobalt-polymer bond in the order N-vinylpyrrolidonecontrol of the polymerizations observed for the last two monomers. Such a double linkage between the controlling agent and the polymer, through a covalent bond and a dative bond, is unique in the field of controlled radical polymerization and represents a powerful opportunity to fine tune the equilibrium between latent and free radicals. Possible hydrogen bond formation is also taken into account in the case of N-vinyl acetamide and N-vinyl formamide. These results are essential for understanding the factors influencing Co-C bond strength in general, and the CMRP mechanism in particular, but also for developing a powerful platform for the synthesis of new precision poly(N-vinyl amide) materials, which are an important class of polymers that sustain numerous applications today. PMID:22907863

  17. Anticoagulant surface of 316 L stainless steel modified by surface-initiated atom transfer radical polymerization.

    PubMed

    Guo, Weihua; Zhu, Jian; Cheng, Zhenping; Zhang, Zhengbiao; Zhu, Xiulin

    2011-05-01

    Polished 316 L stainless steel (SS) was first treated with air plasma to enhance surface hydrophilicity and was subsequently allowed to react with 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane to introduce an atom transfer radical polymerization (ATRP) initiator. Accordingly, the surface-initiated atom transfer radical polymerization of polyethylene glycol methacrylate (PEGMA) was carried out on the surface of the modified SS. The grafting progress was monitored by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy. The polymer thickness as a function different polymerization times was characterized using a step profiler. The anticoagulative properties of the PEGMA modified SS surface were investigated. The results showed enhanced anticoagulative to acid-citrate-dextrose (ACD) blood after grafting PEGMA on the SS surface. PMID:21528878

  18. Mechano-chemical radical formation and polymerization initiation during wet grinding of alumina.

    PubMed

    Damm, C; Peukert, W

    2011-11-01

    The formation of free radicals during wet grinding of alumina in a stirred media mill was studied by using the test radical 2,2-diphenyl-1-picrylhydracyl (DPPH). The kinetics of mechano-chemical radical formation follows a zeroth-order rate law. Particle breakage as well as mechanical activation of the surface of the alumina particles contributes to the radical formation. The rate constants of the radical formation due to mechanical activation of the particle surface k(A) and due to particle breakage k(B) depend on the milling process parameters. The radical formation during wet grinding of alumina was exploited to initiate mechano-chemical polymerization reactions of acrylic acid and acryl amide, respectively. In this way nanoparticles functionalized with polyacrylic acid and polyacryl amide, respectively, are obtained. The influence of the milling process parameters on the kinetics of mechano-chemical radical formation and on the grafted amount of polymer is discussed on the basis of stress energy and number of stress events in the mill. A correlation between the grafted amount of polyacryl amide on the alumina particles and the total radical formation rate was found showing that the concentration of mechano-chemically formed free radicals governs the efficacy of a chemical reaction at activated particle surfaces. PMID:21820123

  19. Advancing Polymer-Supported Ionogel Electrolytes Formed via Radical Polymerization

    NASA Astrophysics Data System (ADS)

    Visentin, Adam F.

    fabricated. In addition to developing an understanding of UV-polymerized systems, a rapid 10 to 20 second, microwave-assisted polymerization method was developed as a novel means to create ionogels. These ionogels exhibited comparable mechanical response and ionic conductivity levels to those gels fabricated by the UV method. Lastly, an EDLC prototype was fabricated using a UV-polymerized ionogel formed in situ between two high-surface area carbon electrodes. The device performance metrics were comparable to commercial EDLCs, and functioned for several thousand cycles with limited loss in capacitance.

  20. The fabrication of superlow protein absorption zwitterionic coating by electrochemically mediated atom transfer radical polymerization and its application.

    PubMed

    Hu, Yichuan; Yang, Guang; Liang, Bo; Fang, Lu; Ma, Guanglong; Zhu, Qin; Chen, Shengfu; Ye, Xuesong

    2015-02-01

    A well-controllable electrochemically mediated surface-initiated atom transfer radical polymerization (e-siATRP) method for the fabrication of superlow protein absorption zwitterionic hydrogel coatings based on poly(sulbetaine methacrylate) (pSBMA) was developed in this work. The effects of the electric condition on polymerization as well as its antifouling performances both in vitro and in vivo were also investigated. Different potentials (-0.08 V, -0.15 V and -0.22 V) and polymerization times (from 8 to 48 h) were chosen to study the polymerization procedure. X-ray photoelectron spectroscopy, atomic force microscopy and ellipsometry measurements were used to characterize the properties of the polymer layers. Ellipsometry measurements showed that a higher potential provided faster polymerization and thicker polymer layers; however, the protein absorption experiments showed that the best polymerization condition was under a constant potential of -0.15 V and 32 h, under which the protein absorption was 0.8% in an enzyme-linked immunosorbent assay (compared to a bare gold electrode). The electrodes with a pSBMA coating effectively deduced the current sensitivity decay both in undiluted serum and in vivo. The usage of the commercially available polymerization monomer of SBMA, the simple convenient synthesis process regardless of the presence of oxygen and the excellent controllability of e-siATRP make it a very promising and universal technique in the preparation of zwitterionic polymer coatings, especially in the development of biocompatible material for implantable devices such as neural and biosensor electrodes. PMID:25463508

  1. Surface-initiated atom transfer radical polymerization from chitin nanofiber macroinitiator film.

    PubMed

    Yamamoto, Kazuya; Yoshida, Sho; Kadokawa, Jun-Ichi

    2014-11-01

    This paper reports the preparation of chitin nanofiber-graft-poly(2-hydroxyethyl acrylate) (CNF-g-polyHEA) films by surface-initiated atom transfer radical polymerization (ATRP) of HEA monomer from a CNF macroinitiator film. First, a CNF film was prepared by regeneration from a chitin ion gel with an ionic liquid. Then, acylation of the CNF surface with α-bromoisobutyryl bromide was carried out to obtain the CNF macroinitiator film having the initiating moieties (α-bromoisobutyrate group). The surface-initiated graft polymerization of HEA from the CNF macroinitiator film by ATRP was performed to produce the CNF-g-polyHEA film. The IR, XRD, and SEM measurements of the resulting film indicated the progress of the graft polymerization of HEA on surface of CNFs. The molecular weights of the grafted polyHEAs increased with prolonged polymerization times, which affected the mechanical properties of the films under tensile mode. PMID:25129725

  2. Chemical control of rate and onset temperature of nadimide polymerization

    NASA Technical Reports Server (NTRS)

    Lauver, R. W.

    1985-01-01

    The chemistry of norbornenyl capped imide compounds (nadimides) is briefly reviewed with emphasis on the contribution of Diels-Alder reversion in controlling the rate and onset of the thermal polymerization reaction. Control of onset temperature of the cure exotherm by adjusting the concentration of maleimide is demonstrated using selected model compounds. The effects of nitrophenyl compounds as free radical retarders on nadimide reactivity are discussed. A simple copolymerization model is proposed for the overall nadimide cure reaction. An approximate numerical analysis is carried out to demonstrate the ability of the model to simulate the trends observed for both maleimide and nitrophenyl additions.

  3. Synthesis and characterization of carbon fibers functionalized with poly (glycidyl methacrylate) via atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Wu, Yongwei; Xiong, Lei; Qin, Xiaokang; Wang, Zhengyue; Ding, Bei; Ren, Huan; Pi, Xiaolong

    2015-07-01

    In this work, polyacrylonitrile (PAN)-based carbon fibers (CF) were chemically modified with poly (glycidyl methacrylate) (PGMA) via atom transfer radical polymerization (ATRP) to improve the interaction between the CF and polymer matrix. The FT-IR, TGA, and XPS were used to determine the chemical structure of the resulting products and the quantities of PGMA chains grafted from the CF surface. The experimental results confirm that the CF surface was functionalized and glycidyl methacrylate was graft-polymerized onto the CF, and the grafting content of polymer could reach 10.2%.

  4. Modeling the cure kinetics of crosslinking free radical polymerizations using the Avrami theory of phase transformation

    SciTech Connect

    Finnegan, G.R.; Shine, A.D.

    1995-12-01

    A model, based on Avrami`s theory of phase transformation, has been developed to describe the cure kinetics of crosslinking free radical polymerizations. The model assumes the growing polymer can be treated as a distinct phase and the nucleation rate is proportional to the initiation rate of the polymerization. The Avrami time exponent was verified to be 4.0. This physically-based, two-parameter model fits vinyl ester resin heat flow data as well as the empirical, four-parameter autocatalytic model, and is capable of describing both neat and fiber-containing resin.

  5. Phenacyl Ethyl Carbazolium as a Long Wavelength Photoinitiator for Free Radical Polymerization.

    PubMed

    Kara, Merve; Dadashi-Silab, Sajjad; Yagci, Yusuf

    2015-12-01

    A new phenacyl-type photoinitiator based on ethyl carbazole as a long wavelength photo-initiator is developed for free radical polymerization. Phenacyl ethyl carbazolium hexafluoroantimonate (PECH) photoinitiator is synthesized in a two-step, one-pot manner by quaternizing ethyl carbazole with phenacyl bromide and subsequent ion exchange reaction with potassium hexafluoroantimonate. Under irradiation, PECH tends to undergo homolytic bond cleavage bringing about initiating free radicals. However, as evidenced by cyclic voltammetry and real-time photobleaching studies, formation of initiating cationic species is highly unlikely as the photochemically formed charged carbazole units tend to couple. PMID:26356628

  6. Photoinduced Atom Transfer Radical Polymerization with ppm-Level Cu Catalyst by Visible Light in Aqueous Media.

    PubMed

    Pan, Xiangcheng; Malhotra, Nikhil; Simakova, Antonina; Wang, Zongyu; Konkolewicz, Dominik; Matyjaszewski, Krzysztof

    2015-12-16

    Photoinduced ATRP was successfully performed in aqueous media. Polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) in the presence of CuBr2 catalyst and tris(2-pyridylmethyl)amine ligand when irradiated with visible light of 392 nm wavelength at 0.9 mW/cm(2) intensity was well controlled. Linear semi-logarithmic kinetic plots and molecular weights increasing with conversion were observed. Polymers of OEOMA were synthesized with low dispersity (Mw/Mn = 1.12) using only 22 ppm of copper catalyst in the presence of excess bromide anions in highly diluted (90% v/v) aqueous media. The effects of copper concentration, salt, and targeted degrees of polymerization were investigated. The polymerization could be directly regulated by external stimulation, i.e., switching the irradiation on/off, with a good retention of chain-end functionality, as proved by clean chain extension of the OEOMA polymers. This new system could enable applications for controlled aqueous radical polymerization due to its low catalyst loading in the absence of any other chemicals. PMID:26634963

  7. Silver nanoparticles coated with thioxanthone derivative as hybrid photoinitiating systems for free radical polymerization.

    PubMed

    Nehlig, Emilie; Schneider, Raphaël; Vidal, Loic; Clavier, Gilles; Balan, Lavinia

    2012-12-21

    A new type of photoinitiator for free radical polymerization was synthesized and characterized. 2-(11-Mercaptoundecyloxy)thioxanthone (1) was anchored at the surface of silver nanoparticles (NPs), and the interaction of plasmon field generated in the immediate vicinity of Ag NPs carrying the chromophores was evaluated. The optical features and structure of the silver-initiator nanoassemblies (Ag@1) were characterized by UV-vis and fluorescence spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). TEM and XRD studies revealed the presence of ca. 5-6 nm diameter Ag NPs, and XPS also confirmed the successful anchorage of 1 at their periphery. The nanoassemblies Ag@1 were successfully used as macroinitiator for radical polymerization of acrylate monomers, triggered photochemically, to obtain Ag(0)-polyacrylate nanocomposite materials. The nanocomposite materials synthesized with the use of Ag@1 exhibit attractive possibilities for patterning the surface of thin films. PMID:23231028

  8. Structural and Mechanistic Aspects of Copper Catalyzed Atom Transfer Radical Polymerization

    NASA Astrophysics Data System (ADS)

    Pintauer, Tomislav; Matyjaszewski, Krzysztof

    During the past decade, atom transfer radical polymerization (ATRP) has had a tremendous impact on the synthesis of macromolecules with well-defined compositions, architectures, and functionalities. Structural features of copper(I) and copper(II) complexes with bidentate, tridentate, tetradentate, and multidentate nitrogen-based ligands commonly utilized in ATRP are reviewed and discussed. Additionally, recent advances in mechanistic understanding of copper-mediated ATRP are outlined.

  9. Well-defined biohybrids using reversible-deactivation radical polymerization procedures.

    PubMed

    Averick, Saadyah; Mehl, Ryan A; Das, Subha R; Matyjaszewski, Krzysztof

    2015-05-10

    The use of reversible deactivation radical polymerization (RDRP) methods has significantly expanded the field of bioconjugate synthesis. RDRP procedures have allowed the preparation of a broad range of functional materials that could not be realized using prior art poly(ethylene glycol) functionalization. The review of procedures for synthesis of biomaterials is presented with a special focus on the use of RDRP to prepare biohybrids with proteins, DNA and RNA. PMID:25483427

  10. Preparation of well-defined poly(2-hydroxyethyl methacrylate) macromonomers via atom transfer radical polymerization.

    PubMed

    Yang, Pengcheng; Armes, Steven P

    2014-01-01

    A series of six near-monodisperse methacrylic macromonomers is prepared via atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate using a tertiary amine-functionalized initiator at 50 °C, followed by quaternization with excess 4-vinylbenzyl chloride at 20 °C. GPC analyses indicate polydispersities of around 1.20 and their mean degrees of polymerization (DP) range from 20 to 70, as judged by both (1) H NMR and UV spectroscopy. The former technique is more convenient but the latter proved more accurate for the higher DP values, provided that an appropriate model compound is utilized for calibration. Finally, these new macromonomers are used to prepare sterically stabilized polystyrene latexes with relatively narrow size distributions via alcoholic dispersion polymerization. PMID:24123461

  11. Creating monodisperse polyacrylamide free-radically via thermal frontal polymerization in confined geometries

    NASA Astrophysics Data System (ADS)

    Datta, Preeta; Efimenko, Kirill; Genzer, Jan

    2014-03-01

    Bulk free radical polymerization reactions lead to highly polydisperse polymers (polydispersity index, PDI >> 1.5). In the past, researchers have shown that polymerization in porous microreactors can lower polydispersity (PDI ~1.5-1.7) by promoting gelation. We employ free-radical thermal frontal polymerization reaction of acrylamide (AAm) in DMSO in highly confined reactors (height <1mm) to produce high molecular weight (~300 kDa) PAAm of relatively low PDI (~1.2). In frontal polymerization systems, a localized reaction zone propagates in space along the direction of heat transfer, sustained by the interplay of heat diffusion and Arrhenius reaction kinetics. The directional heat transfer assists in maintaining the uniformity of the front temperature. While convection improves thermal transport, it causes inhomogeneity in the propagating front in horizontal reactors. In highly confined systems, convection is heavily suppressed, as manifested by the ``flattening'' of the reaction front and the absence of ``fingering''. Gelation lowers termination rate and increases the life time of the active reaction centers. Elimination of convection in confined geometries coupled with directional heat transfer and gelation results in polymers with high molecular weights and low PDIs.

  12. Influence of cure via network structure on mechanical properties of a free-radical polymerizing thermoset

    NASA Astrophysics Data System (ADS)

    Ganglani, Manisha Sachin

    The matrix of a composite material exerts influence over composite properties. The hypothesis is that control of molecular architecture of the matrix allows for the control of resin properties and therefore impacts composite properties. The objective of this research is to define the relationship between cure chemistry, network structure, and final physical properties of vinyl ester-styrene (VE/S) resin, a free-radical polymerizing thermoset polymer often used as the matrix of fiber reinforced polymers. Tensile and fracture properties of the polymer are found to depend on both cure schedule and cure formulation. The possibilities of phase separation and microgel formation being the cause for the differences in mechanical properties are examined. This research shows that the VE/S system does not phase separate under the conditions studied. This proven, the research examines changes in network architecture under different cure conditions. It is found that though bulk properties of the resin are unaffected by the details of the cure, the microscopic morphology, in particular the type of crosslink formed (intermolecular bond or intramolecular bond), is sensitive to both cure temperature and initiation mechanism as determined by cure formulation. Thus, the molecular architecture of the network is responsible for the bulk mechanical properties of the resin. A kinetic analysis shows that both temperature and initiation mechanism affect the apparent "reaction order" of the VE/S system as determined by the autoacceleration equation. This apparent reaction order is interpreted as being an indication of the degree of heterogeneity in the resin. By controlling cure temperature and cure formulation, it is possible to minimize the apparent reaction order and thereby optimize physical properties. Finally, a theory is adapted from other non-network polymer systems to describe qualitatively how cure temperature and initiation mechanism may alter the heterogeneity in network

  13. A Mechanochemical Switch to Control Radical Intermediates

    PubMed Central

    2015-01-01

    B12-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB12-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch. When the switch is “off”, the 5′-deoxyadenosyl radical moiety is stabilized by releasing the internal strain of an enzyme-imposed conformation. Turning the switch “on,” the enzyme environment becomes the driving force to impose a distinct conformation of the 5′-deoxyadenosyl radical to avoid deleterious radical transfer. This mechanochemical switch illustrates the elaborate way in which enzymes attain selectivity of extremely chemically challenging reactions. PMID:24846280

  14. A mechanochemical switch to control radical intermediates.

    PubMed

    Brunk, Elizabeth; Kellett, Whitney F; Richards, Nigel G J; Rothlisberger, Ursula

    2014-06-17

    B₁₂-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB₁₂-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch. When the switch is "off", the 5'-deoxyadenosyl radical moiety is stabilized by releasing the internal strain of an enzyme-imposed conformation. Turning the switch "on," the enzyme environment becomes the driving force to impose a distinct conformation of the 5'-deoxyadenosyl radical to avoid deleterious radical transfer. This mechanochemical switch illustrates the elaborate way in which enzymes attain selectivity of extremely chemically challenging reactions. PMID:24846280

  15. Preparation and characterization of optical-functional diblock copolymer brushes on hollow sphere surface via atom transfer radical polymerization

    SciTech Connect

    Wang, Li-Ping; Li, Wen-Zhi; Zhao, Li-Min; Zhang, Chun-Juan; Wang, Yan-Dong; Kong, Li-Li; Li, Ling-Ling

    2010-09-15

    The optical-functional poly(methyl methacrylate)-block-Tb complex diblock copolymer brushes grafted from hollow sphere surface via atom transfer radical polymerization were investigated in this work. A sufficient amount of azo initiator was introduced onto hollow sphere surface firstly. Then the monomer methyl methacrylate was polymerized via surface-initiated reverse atom transfer radical polymerization using azo group modified hollow sphere as initiator. Following, the poly(methyl methacrylate) modified hollow sphere was used as maroinitiator for surface-initiated atom transfer radical polymerization of Tb complex. The samples were characterized by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, gel permeation chromatographer and transmission electron microscopy, respectively. The results indicated that the poly(methyl methacrylate) had grafted from hollow sphere surface and the average diameter of hollow core was about 1 {mu}m. The optical properties of the poly(methyl methacrylate)-block-Tb copolymer modified hollow sphere were also reported.

  16. Instantaneous Directional Growth of Block Copolymer Nanowires During Heterogeneous Radical Polymerization (HRP).

    PubMed

    Lu, Chunliang; Urban, Marek W

    2016-04-13

    Polymeric nanowires that consist of ultrahigh molecular weight block copolymers were instantaneously prepared via one-step surfactant-free heterogeneous radical polymerization (HRP). Under heterogeneous reaction and initiator-starvation conditions, the sequential copolymerization of hydrophilic and hydrophobic monomers facilitates the formation of amphiphilic ultrahigh molecular weight block copolymers, which instantaneously assemble to polymeric nanowires. As polymerization progresses, initially formed nanoparticles exhibit the directional growth due to localized repulsive forces of hydrophilic blocks and confinement of the hydrophobic blocks that adopt favorable high aspect ratio nanowire morphologies. Using one-step synthetic approach that requires only four ingredients (water as a solvent, two polymerizable monomers (one hydrophilic and one hydrophobic), and water-soluble initiator), block copolymer nanowires ∼70 nm in diameter and hundreds of microns in length are instantaneously grown. For example, when 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and styrene (St) were copolymerized, high aspect ratio nanowires consist of ultrahigh (>10(6) g/mol) molecular weight pDMAEMA-b-St block copolymers and the presence of temperature responsive pDMAEMA blocks facilitates nanowire diameter changes as a function of temperature. These morphologies may serve as structural components of the higher order biological constructs at micro and larger length scales, ranging from single strand nanowires to engineered biomolecular networks capable of responding to diverse and transient environmental signals, and capable of dimensional changes triggered by external stimuli. PMID:27002238

  17. Controlled polymerization of acrylonitrile proceeded along with the Belousov-Zhabotinsky oscillator by changing its stirring conditions

    NASA Astrophysics Data System (ADS)

    Furue, Yuuka; Okano, Kunihiko; Banno, Taisuke; Asakura, Kouichi

    2016-02-01

    Chemical oscillations of the manganese-ion catalyzed Belousov-Zhabotinsky (BZ) reaction system were found to be controlled by changing its stirring conditions. The oscillation stopped at a high stirring rate, while it reappeared immediately by reducing the stirring rate. It is known in the BZ reaction system, that the radical polymerization takes place along with the oscillation when acrylic monomers are added. By the addition of acrylonitrile to the system stirred at a high stirring rate, the oscillation as well as the polymerization of acrylonitrile stopped. The radical polymerization of acrylonitrile by the BZ oscillator is thus found to be made controllable by changing the mixing conditions.

  18. Fixed Point Transformations Based Iterative Control of a Polymerization Reaction

    NASA Astrophysics Data System (ADS)

    Tar, József K.; Rudas, Imre J.

    As a paradigm of strongly coupled non-linear multi-variable dynamic systems the mathematical model of the free-radical polymerization of methyl-metachrylate with azobis (isobutyro-nitrile) as an initiator and toluene as a solvent taking place in a jacketed Continuous Stirred Tank Reactor (CSTR) is considered. In the adaptive control of this system only a single input variable is used as the control signal (the process input, i.e. dimensionless volumetric flow rate of the initiator), and a single output variable is observed (the process output, i.e. the number-average molecular weight of the polymer). Simulation examples illustrate that on the basis of a very rough and primitive model consisting of two scalar variables various fixed-point transformations based convergent iterations result in a novel, sophisticated adaptive control.

  19. Stimuli-responsive surfaces using polyampholyte polymer brushes prepared via atom transfer radical polymerization.

    PubMed

    Ayres, Neil; Cyrus, Crystal D; Brittain, William J

    2007-03-27

    The synthesis of AB diblock copolymer polyampholyte polymer brushes of the type Si/SiO2//poly(acrylic acid-b-vinyl pyridine) prepared using atom transfer radical polymerization is reported. Both 2- and 4-vinyl pyridine have been used. The diblock polyampholyte polymer brushes demonstrate stimuli-responsive behavior with respect to pH, showing both polyelectrolyte and polyampholyte effects. Furthermore, we have quaternized the 4-vinyl pyridine segments to form a mixed weak/strong, or annealed/quenched, polyelectrolyte system. The quaternized polymer brush exhibits different pH-responsive behavior, with decreasing film thickness being observed with increasing pH. PMID:17319701

  20. Rapid synthesis of polymer brush surfaces via microwave-assisted surface-initiated radical polymerization.

    PubMed

    Guo, Wei; Hensarling, Ryan M; LeBlanc, Arthur L; Hoff, Emily A; Baranek, Austin D; Patton, Derek L

    2012-05-14

    Microwave-assisted surface-initiated radical polymerization (μW-SIP) is demonstrated for the rapid synthesis of polymer brush surfaces on two-dimensional substrates. μW-SIP is carried out at constant temperature and microwave power allowing comparison with conventional SIP carried out in an oil bath at the same effective solution temperature. We show μW-SIP enables significant enhancements (up to 39-fold increase) in brush thickness at reduced reaction times for a range of monomer types (i.e. acrylamides, acrylates, methacrylates, and styrene). The effects of reaction time, monomer concentration, and microwave power on film thickness are explored. PMID:22514123

  1. An ultra-sensitive microfluidic immunoassay using living radical polymerization and porous polymer monoliths.

    SciTech Connect

    Abhyankar, Vinay V.; Singh, Anup K.; Hatch, Anson V.

    2010-07-01

    We present a platform that combines patterned photopolymerized polymer monoliths with living radical polymerization (LRP) to develop a low cost microfluidic based immunoassay capable of sensitive (low to sub pM) and rapid (<30 minute) detection of protein in 100 {micro}L sample. The introduction of LRP functionality to the porous monolith allows one step grafting of functionalized affinity probes from the monolith surface while the composition of the hydrophilic graft chain reduces non-specific interactions and helps to significantly improve the limit of detection.

  2. Facile synthesis of brush poly(phosphoamidate)s via one-pot tandem ring-opening metathesis polymerization and atom transfer radical polymerization.

    PubMed

    Ding, Liang; Qiu, Jun; Wei, Jun; Zhu, Zhenshu

    2014-09-01

    Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)-based brush poly(phosphoamidate)s are successfully synthesized by a combination of ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) following either a commutative two-step procedure or a straightforward one-pot process using Grubbs ruthenium-based catalysts for tandem catalysis. Compared with the traditional polymerization method, combining ROMP and ATRP in a one-pot process allows the preparation of brush copolymers characterized by a relatively moderate molecular weight distribution and quantitative conversion of monomer. Moreover, the surface morphologies and aggregation behaviors of these polymers are studied by AFM and TEM measurements. PMID:24729161

  3. A silver bullet: elemental silver as an efficient reducing agent for atom transfer radical polymerization of acrylates.

    PubMed

    Williams, Valerie A; Ribelli, Thomas G; Chmielarz, Pawel; Park, Sangwoo; Matyjaszewski, Krzysztof

    2015-02-01

    Elemental silver was used as a reducing agent in the atom transfer radical polymerization (ATRP) of acrylates. Silver wire, in conjunction with a CuBr(2)/TPMA catalyst, enabled the controlled, rapid preparation of polyacrylates with dispersity values down to Đ = 1.03. The silver wire in these reactions was reused several times in sequential reactions without a decline in performance, and the amount of copper catalyst used was reduced to 10 ppm without a large decrease in control. A poly(n-butyl acrylate)-block-poly(tert-butyl acrylate) diblock copolymer was synthesized with a molecular weight of 91 400 and Đ = 1.04, demonstrating good retention of chain-end functionality and a high degree of livingness in this ATRP system. PMID:25599253

  4. Study on the role of active radicals on plasma sterilization inside small diameter flexible polymeric tubes

    NASA Astrophysics Data System (ADS)

    Mstsuura, Hiroto; Fujiyama, Takatomo; Okuno, Yasuki; Furuta, Masakazu; Okuda, Shuichi; Takemura, Yuichiro

    2015-09-01

    Recently, atmospheric pressure discharge plasma has gathered attention in various fields. Among them, plasma sterilization with many types of plasma source has studied for decades and its mechanism is still an open question. If active radicals produced in plasma has main contribution of killing bacterias, direct contact of the so-called plasma flame might not be necessary. To confirm this, sterilization inside small diameter flexible polymeric tubes is studied in present work. DBD type plasma jet is produce by flowing helium gas in a glass tube. A long polymeric tube is connected and plasma jet is introduced into it. Plasma flame length depends on helium gas flow rate, but limited to about 10 cm in our experimental condition. E.colis set at the exit plasma source is easily killed during 10 min irradiation. At the tube end (about 20 cm away from plasma source exit), sterilization is possible with 30 min operation. This result shows that active radical is produced with helium plasma and mist contained in sample, and it can be transferred more than 20 cm during it life time. More plasma diagnostic data will also be shown at the conference. This work was partially supported by the ''ZE Research Program, IAE(ZE27B-4).

  5. Application of living radical polymerization to the synthesis of resist polymers for radiation lithography

    NASA Astrophysics Data System (ADS)

    Shimizu, Takashi; Ichikawa, Tsuneki

    2005-07-01

    Poly(styrene) and poly(methyl acrylate) with benzyl ester of carboxylic acid at the center of the polymer skeletons were synthesized by living radical polymerization for developing a new type of radiation resist with high resistivity to plasma etching and high sensitivity and spatial resolution to ionizing radiations. The initiators were benzyl esters with two functional groups for living radical polymerization on the benzyl and the carboxylic sides. Introduction of benzyl ester to the polymer skeletons changed the polymers from cross-link type to scission type upon γ-irradiation. Irradiation of the polymers resulted in the binary change of the molecular weight, due to dissociative capture of secondary electrons by the benzyl ester, as MnR1 COOCH (C6H5)R2Mn +e- →MnR1COO- + rad CH (C6H5)R2Mn . The generated polymer fragments were not decomposed by further irradiation, which suggests that the synthesized polymers have high resistivity to plasma etching.

  6. Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts.

    PubMed

    Pearson, Ryan M; Lim, Chern-Hooi; McCarthy, Blaine G; Musgrave, Charles B; Miyake, Garret M

    2016-09-01

    N-Aryl phenoxazines have been synthesized and introduced as strongly reducing metal-free photoredox catalysts in organocatalyzed atom transfer radical polymerization for the synthesis of well-defined polymers. Experiments confirmed quantum chemical predictions that, like their dihydrophenazine analogs, the photoexcited states of phenoxazine photoredox catalysts are strongly reducing and achieve superior performance when they possess charge transfer character. We compare phenoxazines to previously reported dihydrophenazines and phenothiazines as photoredox catalysts to gain insight into the performance of these catalysts and establish principles for catalyst design. A key finding reveals that maintenance of a planar conformation of the phenoxazine catalyst during the catalytic cycle encourages the synthesis of well-defined macromolecules. Using these principles, we realized a core substituted phenoxazine as a visible light photoredox catalyst that performed superior to UV-absorbing phenoxazines as well as previously reported organic photocatalysts in organocatalyzed atom transfer radical polymerization. Using this catalyst and irradiating with white LEDs resulted in the production of polymers with targeted molecular weights through achieving quantitative initiator efficiencies, which possess dispersities ranging from 1.13 to 1.31. PMID:27554292

  7. All-polymeric control of nanoferronics

    PubMed Central

    Xu, Beibei; Li, Huashan; Hall, Asha; Gao, Wenxiu; Gong, Maogang; Yuan, Guoliang; Grossman, Jeffrey; Ren, Shenqiang

    2015-01-01

    In the search for light and flexible nanoferronics, significant research effort is geared toward discovering the coexisting magnetic and electric orders in crystalline charge-transfer complexes. We report the first example of multiferroicity in centimeter-sized crystalline polymeric charge-transfer superstructures that grow at the liquid-air interface and are controlled by the regioregularity of the polymeric chain. The charge order–driven ferroic mechanism reveals spontaneous and hysteretic polarization and magnetization at the donor-acceptor interface. The charge transfer and ordering in the ferroic assemblies depend critically on the self-organizing and molecular packing of electron donors and acceptors. The invention described here not only represents a new coupling mechanism of magnetic and electric ordering but also creates a new class of emerging all-organic nanoferronics. PMID:26824068

  8. All-polymeric control of nanoferronics.

    PubMed

    Xu, Beibei; Li, Huashan; Hall, Asha; Gao, Wenxiu; Gong, Maogang; Yuan, Guoliang; Grossman, Jeffrey; Ren, Shenqiang

    2015-12-01

    In the search for light and flexible nanoferronics, significant research effort is geared toward discovering the coexisting magnetic and electric orders in crystalline charge-transfer complexes. We report the first example of multiferroicity in centimeter-sized crystalline polymeric charge-transfer superstructures that grow at the liquid-air interface and are controlled by the regioregularity of the polymeric chain. The charge order-driven ferroic mechanism reveals spontaneous and hysteretic polarization and magnetization at the donor-acceptor interface. The charge transfer and ordering in the ferroic assemblies depend critically on the self-organizing and molecular packing of electron donors and acceptors. The invention described here not only represents a new coupling mechanism of magnetic and electric ordering but also creates a new class of emerging all-organic nanoferronics. PMID:26824068

  9. Integration of lignin and acrylic monomers towards grafted copolymers by free radical polymerization.

    PubMed

    Liu, Xiaohuan; Xu, Yuzhi; Yu, Juan; Li, Shouhai; Wang, Jifu; Wang, Chunpeng; Chu, Fuxiang

    2014-06-01

    Three kinds of acrylic monomers (2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA), methyl methacrylate (MMA) and butyl acrylate (BA)) were utilized to modify the lignin (BBL) by "grafting from" free radical polymerization (FRP), respectively. Calcium chloride/hydrogen peroxide (CaCl2/H2O2) was used as initiator. Effects of monomer type and concentration, initiator concentration and polymerization time on grafting from BBL were studied. Grafting of poly (acrylic monomers) onto BBL was verified by the following characterizations and this synthesis method was found to be high efficient and selective for grafting polymerization of BBL. The presence of the BBL moiety in the backbone also resulted in higher glass transition temperature compared with the homopolymer of each monomer, and some modified copolymers also improved its thermal stability. All modifications made BBL more hydrophobic and the static contact angles of these modified copolymers were above 80°. XPS analysis revealed that the surface of these modified BBL copolymers were dominated by acrylate monomer moiety. Additionally, the BBL-g-PBA copolymers can be used as dispersion modifiers in PLA-based materials to enhance UV absorption. PMID:24742785

  10. Mechanism of Photoinduced Metal-Free Atom Transfer Radical Polymerization: Experimental and Computational Studies.

    PubMed

    Pan, Xiangcheng; Fang, Cheng; Fantin, Marco; Malhotra, Nikhil; So, Woong Young; Peteanu, Linda A; Isse, Abdirisak A; Gennaro, Armando; Liu, Peng; Matyjaszewski, Krzysztof

    2016-02-24

    Photoinduced metal-free atom transfer radical polymerization (ATRP) of methyl methacrylate was investigated using several phenothiazine derivatives and other related compounds as photoredox catalysts. The experiments show that all selected catalysts can be involved in the activation step, but not all of them participated efficiently in the deactivation step. The redox properties and the stability of radical cations derived from the catalysts were evaluated by cyclic voltammetry. Laser flash photolysis (LFP) was used to determine the lifetime and activity of photoexcited catalysts. Kinetic analysis of the activation reaction according to dissociative electron-transfer (DET) theory suggests that the activation occurs only with an excited state of catalyst. Density functional theory (DFT) calculations revealed the structures and stabilities of the radical cation intermediates as well as the reaction energy profiles of deactivation pathways with different photoredox catalysts. Both experiments and calculations suggest that the activation process undergoes a DET mechanism, while an associative electron transfer involving a termolecular encounter (the exact reverse of DET pathway) is favored in the deactivation process. This detailed study provides a deeper understanding of the chemical processes of metal-free ATRP that can aid the design of better catalytic systems. Additionally, this work elucidates several important common pathways involved in synthetically useful organic reactions catalyzed by photoredox catalysts. PMID:26820243

  11. Preparation of poly(methyl methacrylate) grafted titanate nanotubes by in situ atom transfer radical polymerization.

    PubMed

    Gao, Yuan; Gao, Xueping; Zhou, Yongfeng; Yan, Deyue

    2008-12-10

    This paper reports the successful preparation of core-shell hybrid nanocomposites by a 'grafting from' approach based on in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from titanate nanotubes (TNTs). Transmission electron microscope (TEM) images of the products provide direct evidence for the formation of a core-shell structure, possessing a hard core of TNTs and a soft shell of poly-MMA (PMMA). Fourier-transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance ((1)H NMR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to determine the chemical structure, morphology, and the grafted PMMA quantities of the resulting products. The grafted PMMA content was well controlled and increased with increasing monomer/initiator ratio. Further copolymerization of hydroxyethyl methacrylate (HEMA) with PMMA-coated TNTs as initiators was realized, illustrating the 'living' characteristics of the ATRP method used in this paper. PMID:21730679

  12. In-Channel Atom-Transfer Radical Polymerization of Thermoset Polyester Microfluidic Devices for Bioanalytical Applications

    PubMed Central

    Pan, Tao; Fiorini, Gina S.; Chiu, Daniel T.; Woolley, Adam T.

    2012-01-01

    A new technique for polymer microchannel surface modification, called in-channel atom-transfer radical polymerization, has been developed and applied in the surface derivatization of thermoset polyester (TPE) microdevices with poly(ethylene glycol) (PEG). X-ray photoelectron spectroscopy, electroosmotic flow (EOF), and contact angle measurements indicate that PEG has been grafted on the TPE surface. Moreover, PEG-modified microchannels have much lower and more pH-stable EOF, more hydrophilic surfaces and reduced nonspecific protein adsorption. Capillary electrophoresis separation of amino acid and peptide mixtures in these PEG-modified TPE microchips had good reproducibility. Phosducin-like protein and phosphorylated phosducin-like protein were also separated to measure the phosphorylation efficiency. Our results indicate that PEG-grafted TPE microchips have broad potential application in biomolecular analysis. PMID:17640094

  13. Encapsidated Atom-Transfer Radical Polymerization in Qβ Virus-like Nanoparticles

    PubMed Central

    2015-01-01

    Virus-like particles (VLPs) are unique macromolecular structures that hold great promise in biomedical and biomaterial applications. The interior of the 30 nm-diameter Qβ VLP was functionalized by a three-step process: (1) hydrolytic removal of endogenously packaged RNA, (2) covalent attachment of initiator molecules to unnatural amino acid residues located on the interior capsid surface, and (3) atom-transfer radical polymerization of tertiary amine-bearing methacrylate monomers. The resulting polymer-containing particles were moderately expanded in size; however, biotin-derivatized polymer strands were only very weakly accessible to avidin, suggesting that most of the polymer was confined within the protein shell. The polymer-containing particles were also found to exhibit physical and chemical properties characteristic of positively charged nanostructures, including the ability to easily enter mammalian cells and deliver functional small interfering RNA. PMID:25073013

  14. Surface modification of nanoporous 1,2-polybutadiene by atom transfer radical polymerization or click chemistry.

    PubMed

    Guo, Fengxiao; Jankova, Katja; Schulte, Lars; Vigild, Martin E; Ndoni, Sokol

    2010-02-01

    Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy. PMID:20099923

  15. [Preparation of a novel polymer monolith using atom transfer radical polymerization method for solid phase extraction].

    PubMed

    Shen, Ying; Qi, Li; Qiao, Juan; Mao, Lanqun; Chen, Yi

    2013-04-01

    In this study, a novel polymer monolith based solid phase extraction (SPE) material has been prepared by two-step atom transfer radical polymerization (ATRP) method. Firstly, employing ethylene glycol dimethacrylate (EDMA) as a cross-linker, a polymer monolith filled in a filter head has been in-situ prepared quickly under mild conditions. Then, the activators generated by electron transfer ATRP (ARGET ATRP) was used for the modification of poly(2-(dimethylamino)ethyl-methacrylate) (PDMAEMA) on the monolithic surface. Finally, this synthesized monolith for SPE was successfully applied in the extraction and enrichment of steroids. The results revealed that ATRP can be developed as a facile and effective method with mild reaction conditions for monolith construction and has the potential for preparing monolith in diverse devices. PMID:23898628

  16. Uranium Recovery from Seawater: Development of Fiber Adsorbents Prepared via Atom-Transfer Radical Polymerization

    SciTech Connect

    Saito, Tomonori; Brown, Suree; Chatterjee, Sabornie; Kim, Jungseung; Tsouris, Costas; Mayes, Richard T; Kuo, Li-Jung; Gill, Gary; Oyola, Yatsandra; Janke, Christopher James; Dai, Sheng

    2014-01-01

    A novel adsorbent preparation method using atom-transfer radical polymerization (ATRP) combined with radiation-induced graft polymerization (RIGP) was developed to synthesize an adsorbent for uranium recovery from seawater. The ATRP method allowed a much higher degree of grafting on the adsorbent fibers (595 2818%) than that allowed by RIGP alone. The adsorbents were prepared with varied composition of amidoxime groups and hydrophilic acrylate groups. The successful preparation revealed that both ligand density and hydrophilicity were critical for optimal performance of the adsorbents. Adsorbents synthesized in this study showed a relatively high performance (141 179 mg/g at 49 62 % adsorption) in laboratory screening tests using a uranium concentration of ~6 ppm. This performance is much higher than that of known commercial adsorbents. However, actual seawater experiment showed impeded performance compared to the recently reported high-surface-area-fiber adsorbents, due to slow adsorption kinetics. The impeded performance motivated an investigation of the effect of hydrophilic block addition on the graft chain terminus. The addition of hydrophilic block on the graft chain terminus nearly doubled the uranium adsorption capacity in seawater, from 1.56 mg/g to 3.02 mg/g. The investigation revealed the importance of polymer chain conformation, in addition to ligand and hydrophilic group ratio, for advanced adsorbent synthesis for uranium recovery from seawater.

  17. Preparation of polystyrene brush film by radical chain-transfer polymerization and micromechanical properties

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Chen, Miao; An, Yanqing; Liu, Jianxi; Yan, Fengyuan

    2008-12-01

    A radical chain-transfer polymerization technique has been applied to graft-polymerize brushes of polystyrene (PSt) on single-crystal silicon substrates. 3-Mercapto-propyltrimethoxysilane (MPTMS), as a chain-transfer agent for grafting, was immobilized on the silicon surface by a self-assembling process. The structure and morphology of the graft-functionalized silicon surfaces were characterized by the means of contact-angle measurement, ellipsometric thickness measurement, Fourier transformation infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The nanotribological and micromechanical properties of the as-prepared polymer brush films were investigated by frictional force microscopy (FFM), force-volume analysis and scratch test. The results indicate that the friction properties of the grafted polymer films can be improved significantly by the treatment of toluene, and the chemically bonded polystyrene film exhibits superior scratch resistance behavior compared with the spin-coated polystyrene film. The resultant polystyrene brush film is expected to develop as a potential lubrication coating for microelectromechanical systems (MEMS).

  18. Effect of pH on Swelling Behavior of Polyelectrolyte Brushes Produced via Surface Confined Atom Transfer Radical Polymerization.

    NASA Astrophysics Data System (ADS)

    Sankhe, Amit

    2005-03-01

    Surface-tethered polyelectrolyte brushes comprised of poly (itaconic acid) (PIA) and poly(methacrylic acid) (PMAA) were grown using surface-confined atom transfer radical polymerization (ATRP). The surface- tethered initiator monolayer was formed by self-assembling 2-bromoisobutyryl bromide terminated thiol molecules on gold coated silicon substrates. This polymerization initiator molecule and a copper-based organometallic catalyst allowed tethered polyelectrolyte chains to be grown via radical polymerization at room temperature in aqueous solutions. The behavior of these polyelectrolyte brushes as a function of pH was studied using a phase modulated ellipsometery. The presentation explains how the brushes are affected by external conditions such as the pH of the contacting solution. As the polymer brushes already exist in the charged state, addition of neutral water or salt solution did not affect the polymer brush height, however a decrease of thickness with pH is found.

  19. Radical-initiated controlled synthesis of homo- and copolymers based on acrylonitrile

    NASA Astrophysics Data System (ADS)

    Grishin, D. F.; Grishin, I. D.

    2015-07-01

    Data on the controlled synthesis of polyacrylonitrile and acrylonitrile copolymers with other (meth)acrylic and vinyl monomers upon radical initiation and metal complex catalysis are analyzed. Primary attention is given to the use of metal complexes for the synthesis of acrylonitrile-based (co)polymers with defined molecular weight and polydispersity in living mode by atom transfer radical polymerization. The prospects for using known methods of controlled synthesis of macromolecules for the preparation of acrylonitrile homo- and copolymers as carbon fibre precursors are estimated. The major array of published data analyzed in the review refers to the last decade. The bibliography includes 175 references.

  20. Development of an arylthiobismuthine cocatalyst in organobismuthine-mediated living radical polymerization: applications for synthesis of ultrahigh molecular weight polystyrenes and polyacrylates.

    PubMed

    Kayahara, Eiichi; Yamago, Shigeru

    2009-02-25

    Diphenyl(2,6-dimesitylphenylthio)bismuthine (1a) serves as an excellent cocatalyst in organobismuthine-mediated living radical polymerization (BIRP). Both low and high molecular weight polystyrenes and poly(butyl acrylate)s (PBAs) with controlled molecular weights and low polydispersity indexes (PDIs) were synthesized by the addition of a catalytic amount of 1a to an organobismuthine chain-transfer agent, methyl 2-dimethylbismuthanyl-2-methylpropionate (3). The number-average molecular weight (M(n)) of the resulting polymers increases linearly with the monomer/3 ratio. Structurally well-defined polystyrenes with M(n)'s in the range from 1.0 x 10(4) to 2.0 x 10(5) and PDIs of 1.07-1.15 as well as PBAs with M(n)'s in the range from 1.2 x 10(4) to 2.8 x 10(6) and PDIs of 1.06-1.43 were successfully prepared under mild thermal conditions. Control experiments suggested that 1a reversibly reacts with the polymer-end radical to generate an organobismuthine dormant species and 2,6-dimesitylphenylthiyl radical (2a). This reaction avoids the occurrence of chain termination reactions involving the polymer-end radicals and avoids undesired loss of the bismuthanyl polymer end group. The bulky 2,6-dimesitylphenyl group attached to the sulfur atom may prevent the addition of thiyl radicals to the vinyl monomers to generate new polymer chains. PMID:19161331

  1. Controlled polymerization by incarceration of monomers in nanochannels.

    PubMed

    Uemura, Takashi; Kitagawa, Susumu

    2010-01-01

    Porous Coordination Polymers (PCPs) composed of transition metal ions and bridging organic ligands have been extensively studied. The characteristic features of PCPs are highly regular channel structures, controllable channel sizes approximating molecular dimensions, designable surface potentials and functionality, and flexible frameworks responsive to guest molecules. Owing to these advantages, successful applications of PCPs range from molecular storage and separation to heterogeneous catalysts. In particular, use of their regulated and tunable nanochannels in the field of polymerization has allowed multi-level control of polymerization via control of stereoregularlity, molecular weight, etc. In this chapter, we focus on recent progress in polymerization utilizing the nanochannels of PCPs, and demonstrate why this polymerization system is attractive and promising from the viewpoint of precision control of polymeric structures. PMID:21618745

  2. Quantum mechanical investigation on bimolecular hydrogen abstractions in butyl acrylate-based free radical polymerization processes.

    PubMed

    Mavroudakis, Evangelos; Cuccato, Danilo; Moscatelli, Davide

    2014-03-13

    The present computational study focuses on the investigation of bimolecular hydrogen abstractions that can occur during free radical polymerization (FRP) processes. In particular, several hydrogen abstractions from four monomers (butyl acrylate, BA; styrene, ST; butyl methacrylate, BMA; vinyl acetate, VA) and three different backbone chains (poly-BA, poly-BA-co-VA, and poly-BA-co-ST) have been studied. The aim is to provide an overview of the kinetics for all possible intermolecular hydrogen abstraction reactions from all chemical species present in a bulk FRP as well as to support the understanding of the influence of chemical environment on hydrogen abstractions. All simulations were performed using density functional theory (DFT) with quantum tunneling factors estimated using the Eckart model. This study provides proof that the presence of an electron donating group in the chemical environment of the abstracted hydrogen atoms can lead to lower activation energies and higher rate coefficients for abstraction whereas the presence of an electron withdrawing group leads to opposite effects. PMID:24555565

  3. Modification of polysulfone membranes via surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Dong, Han-Bang; Xu, You-Yi; Yi, Zhuan; Shi, Jun-Li

    2009-08-01

    Hydrophilic poly((poly(ethylene glycol) methyl ether methacrylate) (P(PEGMA)) and poly(glycidylmethacrylate) (PGMA) brushes were grafted from chloromethylated polysulfone (CMPSF) membrane surfaces via surface-initiated atom transfer radical polymerization (ATRP). Prior to ATRP, chloromethylation of PSF was performed beforehand and the obtained CMPSF was prepared into porous membranes by phase inversion process. It was demonstrated that the benzyl chloride groups on the CMPSF membrane surface afforded effective macroinitiators to graft the well-defined polymer brushes. 1H NMR was employed to confirm the structure of CMPSF. The grafting yield of P(PEGMA) and PGMA was determined by weight gain measurement. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) and PGMA chains. Water contact angle measurements indicated that the introduction of P(PEGMA) and PGMA graft chains promoted remarkably the surface hydrophilicity of PSF membranes. The effects of P(PEGMA) and PGMA immobilization on membrane morphology, permeability and fouling resistance were investigated. It was found that P(PEGMA) and PGMA grafts brought higher pure water flux, improved hydrophilic surface and better anti-protein absorption ability to PSF membranes after modification. And evidently, macromonomer P(PEGMA) brought much better properties to the PSF membranes than PGMA macromonomer.

  4. Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates

    PubMed Central

    Foster, Rami N.; Keefe, Andrew J.; Jiang, Shaoyi; Castner, David G.

    2013-01-01

    This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone. PMID:24482558

  5. Rapid cellular internalization of multifunctional star polymers prepared by atom transfer radical polymerization.

    PubMed

    Cho, Hong Y; Gao, Haifeng; Srinivasan, Abiraman; Hong, Joanna; Bencherif, Sidi A; Siegwart, Daniel J; Paik, Hyun-Jong; Hollinger, Jeffrey O; Matyjaszewski, Krzysztof

    2010-09-13

    Poly(ethylene glycol) (PEG) star polymers containing GRGDS (Gly-Arg-Gly-Asp-Ser) peptide sequences on the star periphery were synthesized by atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether methacrylate (PEGMA), GRGDS modified poly(ethylene glycol) acrylate (GRGDS-PEG-Acryl), fluorescein o-methacrylate (FMA), and ethylene glycol dimethacrylate (EGDMA) via an "arm-first" method. Star polymers were approximately 20 nm in diameter, as measured by dynamic light scattering and atomic force microscopy. Conjugation of FMA to the stars was confirmed by fluorescence microscopy, and successful attachment of GRGDS segments to the star periphery was confirmed by (1)H NMR spectroscopy. Both fluorescent PEG star polymers with and without peripheral GRGDS peptide segments were cultured with MC3T3-E1.4 cells. These star polymers were biocompatible with ≥ 90% cell viability after 24 h of incubation. Cellular uptake of PEG star polymers in MC3T3-E1.4 cells was observed by confocal microscopy. Rapid uptake of PEG star polymers with GRGDS peptides (∼ 100% of FITC-positive cells in 15 min measured by flow cytometry) was observed, suggesting enhanced delivery potential of these functional star polymers. PMID:20831270

  6. Surface modification of polymer microfluidic devices using in-channel atom transfer radical polymerization.

    PubMed

    Sun, Xuefei; Liu, Jikun; Lee, Milton L

    2008-07-01

    In-channel atom transfer radical polymerization (ATRP) was used to graft a PEG layer on the surface of microchannels formed in poly(glycidyl methacrylate)-co-(methyl methacrylate) (PGMAMMA) microfluidic devices. The patterned and cover plates were first anchored with ATRP initiator and then thermally bonded together, followed by pumping a solution containing monomer, catalyst, and ligand into the channel to perform ATRP. A PEG-functionalized layer was grafted on the microchannel wall, which resists protein adsorption. X-ray photoelectron spectroscopy (XPS) was used to investigate the initiator-bound surface, and EOF was measured to evaluate the PEG-grafted PGMAMMA microchannel. Fast, efficient, and reproducible separations of amino acids, peptides, and proteins were obtained using the resultant microdevices. Separation efficiencies were higher than 1.0x10(4) plates for a 3.5 cm separation microchannel. Compared with microdevices modified using a previously reported ATRP technique, these in-channel modified microdevices demonstrated better long-term stability. PMID:18615784

  7. Characterization of silver/polystyrene nanocomposites prepared by in situ bulk radical polymerization

    SciTech Connect

    Vukoje, Ivana D.; Vodnik, Vesna V.; Džunuzović, Jasna V.; Džunuzović, Enis S.; Marinović-Cincović, Milena T.; Jeremić, Katarina; Nedeljković, Jovan M.

    2014-01-01

    Graphical abstract: - Highlights: • Synthesis and characterization of polystyrene nanocomposites based on Ag nanoparticles. • The glass transition temperature decreased in nanocomposites with respect to the pure polymer. • Resistance of the polymer to thermal degradation enhanced with Ag nanoparticles content. - Abstract: Nanocomposites (NCs) with different content of silver nanoparticles (Ag NPs) embeded in polystyrene (PS) matrix were prepared by in situ bulk radical polymerization. The nearly monodisperse Ag NPs protected with oleylamine were synthesized via organic solvo-thermal method and further used as a filler. The as-prepared spherical Ag NPs with diameter of 7.0 ± 1.5 nm were well dispersed in the PS matrix. The structural properties of the resulting Ag/PS NCs were characterized by transmission electron microscope (TEM) and Fourier transform infrared (FTIR) spectroscopy, while optical properties were characterized using optical absorption measurements. The gel permeation chromatography (GPC) measurements showed that the presence of Ag NPs stabilized with oleylamine has no influence on the molecular weight and polydispersity of the PS matrix. The influence of silver content on the thermal properties of Ag/PS NCs was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicated that resistance of PS to thermal degradation was improved upon incorporation of Ag NPs. The Ag/PS NCs have lower glass transition temperatures than neat PS because loosely packed oleylamine molecules at the interface caused the increase of free volume and chain segments mobility near the surface of Ag NPs.

  8. Stereo- and Temporally Controlled Coordination Polymerization Triggered by Alternating Addition of a Lewis Acid and Base.

    PubMed

    Liu, Bo; Cui, Dongmei; Tang, Tao

    2016-09-19

    Significant progress has been made with regard to temporally controlled radical and ring-opening polymerizations, for example, by means of chemical reagents, light, and voltage, whereas quantitative switch coordination polymerization is still challenging. Herein, we report the temporally and stereocontrolled 3,4-polymerization of isoprene through allosterically regulating the active metal center by alternating addition of Lewis basic pyridine to "poison" the Lewis acidic active metal species through acid-base interactions and Lewis acidic Al(i) Bu3 to release the original active species through pyridine abstraction. This process is quick, quantitative, and can be repeated multiple times while maintaining high 3,4-selectivity. Moreover, this strategy is also effective for the switch copolymerization of isoprene and styrene with dual 3,4- and syndiotactic selectivity. Tuning the switch cycles and intervals enables the isolation of various copolymers with different distributions of 3,4-polyisoprene and syndiotactic polystyrene sequences. PMID:27539866

  9. Expanded corn starch as a versatile material in atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate.

    PubMed

    Bansal, Ankushi; Kumar, Arvind; Latha, Patnam Padma; Ray, Siddharth Sankar; Chatterjee, Alok Kumar

    2015-10-01

    Polymerization of styrene (St) and methyl methacrylate (MMA) was performed by surface initiated (SI) and activator generated by electron transfer (AGET) systems of atom transfer radical polymerization (ATRP) using renewable expanded corn starch (ECS) as a support. This prepared ECS is found to have V type crystallinity with 50 m(2)g(-1) surface area (<1m(2)g(-1) for corn starch (CS)) and average pore volume of 0.43 cm(3)g(-1) (<0.1cm(3)g(-1) for CS). In SI-ATRP, hydroxyl groups on ECS were converted into macro-initiator by replacing with 2-bromoisobutyryl bromide (BIBB) with a 0.06 degree of substitution determined from NMR. In AGET-ATRP, CuBr2/ligand complex get adsorbed on ECS (Cu(II)/ECS=10 wt.%) to catalyze the polymerization. Synthesized PS/PMMA was characterized by SEM, FT-IR, (1)H NMR. PMID:26076629

  10. Radical polymerization of N-vinylpyrrolidone in the presence of syndiotactic poly(methacrylic acid) templates. [Gamma ray

    SciTech Connect

    Koetsier, D.W.; Tan, Y.Y.; Challa, G.

    1980-06-01

    Radical polymerization of N-vinylpyrrolidone along poly(methacrylic acid) templates of high syndiotactic content was followed dilatometrically in dimethylformamide, which was used as solvent. The effects of template concentration, template molar mass, and temperature on polymerization rate and average molar mass of the formed polyvinylpyrrolidone (PVP) were examined. Template concentrations were varied around the critical concentration for homogeneous segmental distribution, C. Below this concentration, template coils can act as separate microreactors wherein growing PVP radicals exhibit maximum rate enhancement, i.e., relative rate upsilon/sub R/ = upsilon/sub R max/. In the free solution, blank polymerization occurs, i.e., upsilon/sub R/ = 1. Consequently, upsilon/sub R/ can be approximated by the equation ..nu../sub R/ = phi..nu../sub R/max/ + (1 - phi), where phi represents the volume fraction occupied by template coils. The slight increase in ..nu../sub R/ and PVP molar mass with the template chain length is supposed to be caused by the influence of translational diffusion on the termination step. Over the investigated temperature range of 50 to 70/sup 0/C, the activation energy and entropy were almost identical for blank and template polymerization. An expected decrease of ..delta..E not equal to and ..delta..S not equal to in template systems is supposed to be compensated by the effects of desolvation of the template macromolecules during the propagation step.

  11. Comparative study on the separation behavior of monolithic columns prepared via ring-opening metathesis polymerization and via electron beam irradiation triggered free radical polymerization for proteins.

    PubMed

    Bandari, Rajendar; Knolle, Wolfgang; Buchmeiser, Michael R

    2008-05-16

    Monolithic columns have been prepared via ring-opening metathesis polymerization using different monomers and crosslinkers, i.e. norborn-2-ene, 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene, cyclooctene and tris(cyclooct-4-en-1-yloxy)methylsilane. 2-Propanol and toluene were used as macro- and microporogens. Alternatively, monolithic supports were realized via electron beam triggered free radical polymerization using trimethylolpropane triacrylate and ethylmethacrylate. Here, 2-propanol, 1-dodecanol and toluene were used as porogens. The three monolithic supports were structurally characterized by inverse size exclusion chromatography and investigated for their separation capabilities for a series of proteins. Separation efficiencies are discussed within the context of the different structural features of the monolithic supports and are compared to the separation data obtained on a commercial silica-based Chromolith RP-18e column. PMID:18037426

  12. One-Step Immobilization of Initiators for Surface-Initiated Ring Opening Polymerization and Atom Transfer Radical Polymerization by Poly(norepinephrine) Coating.

    PubMed

    Kang, Sung Min; Lee, Haeshin

    2015-02-01

    We report a facile method for surface-initiated ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) via a poly(norepinephrine) coating. Solid substrates were modified by poly(norepinephrine) under alkaline conditions, with concurrent co-adsorption of an ATRP initiator. The poly(norepinephrine) layer acted as a ROP initiator due to the presence of hydroxyl groups in its side chain, resulting in a surface that was able to initiate ATRP and ROP simultaneously. ε-Caprolactone (ε-CL) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) were grafted onto the surface via ROP and ATRP, respectively, and the polymers subsequently grown from the surfaces were characterized in detail using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle goniometry, and atomic force microscopy (AFM). PMID:26353697

  13. Reduction biodegradable brushed PDMAEMA derivatives synthesized by atom transfer radical polymerization and click chemistry for gene delivery.

    PubMed

    Liu, Jia; Xu, Yanglin; Yang, Qizhi; Li, Cao; Hennink, Wim E; Zhuo, Renxi; Jiang, Xulin

    2013-08-01

    Novel reducible and degradable brushed poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) derivatives were synthesized and evaluated as non-viral gene delivery vectors. First, alkyne-functionalized poly(aspartic acid) with a disulfide linker between the propargyl group and backbone poly([(propargyl carbamate)-cystamine]-α,β-aspartamide) (P(Asp-SS-AL)) was synthesized. Second, linear low molecular weight (LMW) monoazido-functionalized PDMAEMAs synthesized via atom transfer radical polymerization were conjugated to the polypeptide side-chains of P(Asp-SS-AL) via click chemistry to yield high molecular weight (HMW) polyaspartamide-based disulfide-containing brushed PDMAEMAs (PAPDEs). The PAPDEs were able to condense plasmid DNA to form 100 to 200nm polyplexes with positive ζ-potentials. Moreover, in the presence of dithiothreitol the PAPDEs degraded into LMW PDAMEMA, resulting in disintegration of the PAPDE/DNA polyplexes and subsequent release of plasmid DNA. In vitro experiments revealed that the PAPDEs were less cytotoxic and more effective in gene transfection than control 25kDa poly(ethyleneimine) and HMW linear PDMAEMA. In conclusion, reducible and degradable polycations composed of LMW PDMAEMAs coupled to a polypeptide backbone via reduction-sensitive disulfide bonds are effective gene vectors with an excellent cytocompatibility. PMID:23660547

  14. Visible-Light Organic Photocatalysis for Latent Radical-Initiated Polymerization via 2e–/1H+ Transfers: Initiation with Parallels to Photosynthesis

    PubMed Central

    2015-01-01

    We report the latent production of free radicals from energy stored in a redox potential through a 2e–/1H+ transfer process, analogous to energy harvesting in photosynthesis, using visible-light organic photoredox catalysis (photocatalysis) of methylene blue chromophore with a sacrificial sterically hindered amine reductant and an onium salt oxidant. This enables light-initiated free-radical polymerization to continue over extended time intervals (hours) in the dark after brief (seconds) low-intensity illumination and beyond the spatial reach of light by diffusion of the metastable leuco-methylene blue photoproduct. The present organic photoredox catalysis system functions via a 2e–/1H+ shuttle mechanism, as opposed to the 1e– transfer process typical of organometallic-based and conventional organic multicomponent photoinitiator formulations. This prevents immediate formation of open-shell (radical) intermediates from the amine upon light absorption and enables the “storage” of light-energy without spontaneous initiation of the polymerization. Latent energy release and radical production are then controlled by the subsequent light-independent reaction (analogous to the Calvin cycle) between leuco-methylene blue and the onium salt oxidant that is responsible for regeneration of the organic methylene blue photocatalyst. This robust approach for photocatalysis-based energy harvesting and extended release in the dark enables temporally controlled redox initiation of polymer syntheses under low-intensity short exposure conditions and permits visible-light-mediated synthesis of polymers at least 1 order of magnitude thicker than achievable with conventional photoinitiated formulations and irradiation regimes. PMID:24786755

  15. Protein microarrays based on polymer brushes prepared via surface-initiated atom transfer radical polymerization.

    PubMed

    Barbey, Raphael; Kauffmann, Ekkehard; Ehrat, Markus; Klok, Harm-Anton

    2010-12-13

    Polymer brushes represent an interesting platform for the development of high-capacity protein binding surfaces. Whereas the protein binding properties of polymer brushes have been investigated before, this manuscript evaluates the feasibility of poly(glycidyl methacrylate) (PGMA) and PGMA-co-poly(2-(diethylamino)ethyl methacrylate) (PGMA-co-PDEAEMA) (co)polymer brushes grown via surface-initiated atom transfer radical polymerization (SI-ATRP) as protein reactive substrates in a commercially available microarray system using tantalum-pentoxide-coated optical waveguide-based chips. The performance of the polymer-brush-based protein microarray chips is assessed using commercially available dodecylphosphate (DDP)-modified chips as the benchmark. In contrast to the 2D planar, DDP-coated chips, the polymer-brush-covered chips represent a 3D sampling volume. This was reflected in the results of protein immobilization studies, which indicated that the polymer-brush-based coatings had a higher protein binding capacity as compared to the reference substrates. The protein binding capacity of the polymer-brush-based coatings was found to increase with increasing brush thickness and could also be enhanced by copolymerization of 2-(diethylamino)ethyl methacrylate (DEAEMA), which catalyzes epoxide ring-opening of the glycidyl methacrylate (GMA) units. The performance of the polymer-brush-based microarray chips was evaluated in two proof-of-concept microarray experiments, which involved the detection of biotin-streptavidin binding as well as a model TNFα reverse assay. These experiments revealed that the use of polymer-brush-modified microarray chips resulted not only in the highest absolute fluorescence readouts, reflecting the 3D nature and enhanced sampling volume provided by the brush coating, but also in significantly enhanced signal-to-noise ratios. These characteristics make the proposed polymer brushes an attractive alternative to commercially available, 2D microarray

  16. Surface modification of glycidyl-containing poly(methyl methacrylate) microchips using surface-initiated atom-transfer radical polymerization.

    PubMed

    Sun, Xuefei; Liu, Jikun; Lee, Milton L

    2008-02-01

    Fabrication of microfluidic systems from polymeric materials is attractive because of simplicity and low cost. Unfortunately, the surfaces of many polymeric materials can adsorb biological samples. Therefore, it is necessary to modify their surfaces before these polymeric materials can be used for separation and analysis. Oftentimes it is difficult to modify polymeric surfaces because of their resistance to chemical reaction. Recently, we introduced a surface-reactive acrylic polymer, poly(glycidyl methacrylate-co-methyl methacrylate) (PGMAMMA), which can be modified easily and is suitable for fabrication of microfluidic devices. Epoxy groups on the surface can be activated by air plasma treatment, hydrolysis, or aminolysis. In this work, the resulting hydroxyl or amino groups were reacted with 2-bromoisobutylryl bromide to introduce an initiator for surface-initiated atom-transfer radical polymerization (SI-ATRP). Polyethylene glycol (PEG) layers grown on the surface using this method were uniform, hydrophilic, stable, and resistant to protein adsorption. Contact angle measurement and X-ray photoelectron spectroscopy (XPS) were used to characterize activated polymer surfaces, initiator-bound surfaces, and PEG-grafted surfaces. We obtained excellent capillary electrophoresis (CE) separations of proteins and peptides with the PEG-modified microchips. A separation efficiency of 4.4 x 10(4) plates for a 3.5 cm long separation channel was obtained. PMID:18179249

  17. Chain Reaction Polymerization.

    ERIC Educational Resources Information Center

    McGrath, James E.

    1981-01-01

    The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

  18. Stress-induced colouration and crosslinking of polymeric materials by mechanochemical formation of triphenylimidazolyl radicals.

    PubMed

    Verstraeten, F; Göstl, R; Sijbesma, R P

    2016-06-30

    Under mechanical stress, the hexaarylbiimidazole (HABI) motif can cleave to triphenylimidazolyl radicals when incorporated into a polymer matrix. The mechanically produced coloured radicals can initiate secondary radical reactions yielding polymer networks. Thus, the HABI mechanophore combines optical reporting of bond scission and reinforcement of polymers in a single molecular moiety. PMID:27326922

  19. Radical and ion molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in RF plasmas at low pressures ( 1.0 torr)

    NASA Technical Reports Server (NTRS)

    Avni, R.; Carmi, U.; Inspektor, A.; Rosenthal, I.

    1984-01-01

    The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes.

  20. Surface modification of carbon nanotubes via combination of mussel inspired chemistry and chain transfer free radical polymerization

    NASA Astrophysics Data System (ADS)

    Wan, Qing; Tian, Jianwen; Liu, Meiying; Zeng, Guangjian; Huang, Qiang; Wang, Ke; Zhang, Qingsong; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2015-08-01

    In this work, a novel strategy for surface modification of carbon nanotubes (CNTs) was developed via combination of mussel inspired chemistry and chain transfer free radical polymerization. First, pristine CNTs were functionalized with polydopamine (PDA), which is formed via self-polymerization of dopamine in alkaline conditions. These PDA functionalized CNTs can be further reacted with amino-terminated polymers (named as PDMC), which was synthesized through chain transfer free radical polymerization using cysteamine hydrochloride as chain transfer agent and methacryloxyethyltrimethyl ammonium chloride as the monomer. PDMC perfectly conjugated with CNT-PDA was ascertained by a series of characterization techniques including transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The dispersibility of obtained CNT nanocomposites (named as CNT-PDA-PDMC) was further examined. Results showed that the dispersibility of CNT-PDA-PDMC in aqueous and organic solutions was obviously enhanced. Apart from PDMC, many other amino-terminated polymers can also be used to functionalization of CNTs via similar strategy. Therefore, the method described in this work should be a general strategy for fabrication various polymer nanocomposites.

  1. Protein adsorption resistance of PVP-modified polyurethane film prepared by surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Yuan, Huihui; Qian, Bin; Zhang, Wei; Lan, Minbo

    2016-02-01

    An anti-fouling surface of polyurethane (PU) film grafted with Poly(N-vinylpyrrolidone) (PVP) was prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). And the polymerization time was investigated to obtain PU films with PVP brushes of different lengths. The surface properties and protein adsorption of modified PU films were evaluated. The results showed that the hydrophilicity of PU-PVP films were improved with the increase of polymerization time, which was not positive correlation with the surface roughness due to the brush structure. Additionally, the protein resistance performance was promoted when prolonging the polymerization time. The best antifouling PU-PVP (6.0 h) film reduced the adsoption level of bovine serum albumin (BSA), lysozyme (LYS), and brovin serum fibrinogen (BFG) by 93.4%, 68.3%, 85.6%, respectively, compared to the unmodified PU film. The competitive adsorption of three proteins indicated that LYS preferentially adsorbed on the modified PU film, while BFG had the lowest adsorption selectivity. And the amount of BFG on PU-PVP (6.0 h) film reduced greatly to 0.08 μg/cm2, which was almost one-tenth of its adsorption from the single-protein system. Presented results suggested that both hydrophilicity and surface roughness might be the important factors in all cases of protein adsorption, and the competitive or selective adsorption might be related to the size of the proteins, especially on the non-charged films.

  2. One-Pot Synthesis of Double Poly(Ionic Liquid) Block Copolymers by Cobalt-Mediated Radical Polymerization-Induced Self-Assembly (CMR-PISA) in Water.

    PubMed

    Cordella, Daniela; Debuigne, Antoine; Jérôme, Christine; Kochovski, Zdravko; Taton, Daniel; Detrembleur, Christophe

    2016-07-01

    Amphiphilic double poly(ionic liquid) (PIL) block copolymers are directly prepared by cobalt-mediated radical polymerization induced self-assembly (CMR-PISA) in water of N-vinyl imidazolium monomers carrying distinct alkyl chains. The cobalt-mediated radical polymerization of N-vinyl-3-ethyl imidazolium bromide (VEtImBr) is first carried out until high conversion in water at 30 °C, using an alkyl bis(acetylacetonate)cobalt(III) adduct as initiator and controlling agent. The as-obtained hydrophilic poly(N-vinyl-3-ethyl imidazolium bromide) (PVEtImBr) is then used as a macroinitiator for the CMR-PISA of N-vinyl-3-octyl imidazolium bromide (VOcImBr). Self-assembly of the amphiphilic PVEtImBr-b-PVOcImBr block copolymer, i.e., of PIL-b-PIL-type, rapidly takes place in water, forming polymer nanoparticles consisting of a hydrophilic PVEtImBr corona and a hydrophobic PVOcImBr core. Preliminary investigation into the effect of the size of the hydrophobic block on the dimension of the nanoparticles is also described. PMID:26991998

  3. Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose.

    PubMed

    Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

    2015-10-28

    This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. PMID:26412343

  4. Nanoengineered analytical immobilized metal affinity chromatography stationary phase by atom transfer radical polymerization: Separation of synthetic prion peptides

    PubMed Central

    McCarthy, P.; Chattopadhyay, M.; Millhauser, G.L.; Tsarevsky, N.V.; Bombalski, L.; Matyjaszewski, K.; Shimmin, D.; Avdalovic, N.; Pohl, C.

    2010-01-01

    Atom transfer radical polymerization (ATRP) was employed to create isolated, metal-containing nanoparticles on the surface of non-porous polymeric beads with the goal of developing a new immobilized metal affnity chromatography (IMAC) stationary phase for separating prion peptides and proteins. Transmission electron microscopy was used to visualize nanoparticles on the substrate surface. Individual ferritin molecules were also visualized as ferritin–nanoparticle complexes. The column's resolving power was tested by synthesizing peptide analogs to the copper binding region of prion protein and injecting mixtures of these analogs onto the column. As expected, the column was capable of separating prion-related peptides differing in number of octapeptide repeat units (PHGGGWGQ), (PHGGGWGQ)2, and (PHGGGWGQ)4. Unexpectedly, the column could also resolve peptides containing the same number of repeats but differing only in the presence of a hydrophilic tail, Q → A substitution, or amide nitrogen methylation. PMID:17481564

  5. Bottom-Up Fabrication of Nanopatterned Polymers on DNA Origami by In Situ Atom-Transfer Radical Polymerization.

    PubMed

    Tokura, Yu; Jiang, Yanyan; Welle, Alexander; Stenzel, Martina H; Krzemien, Katarzyna M; Michaelis, Jens; Berger, Rüdiger; Barner-Kowollik, Christopher; Wu, Yuzhou; Weil, Tanja

    2016-05-01

    Bottom-up strategies to fabricate patterned polymers at the nanoscale represent an emerging field in the development of advanced nanodevices, such as biosensors, nanofluidics, and nanophotonics. DNA origami techniques provide access to distinct architectures of various sizes and shapes and present manifold opportunities for functionalization at the nanoscale with the highest precision. Herein, we conduct in situ atom-transfer radical polymerization (ATRP) on DNA origami, yielding differently nanopatterned polymers of various heights. After cross-linking, the grafted polymeric nanostructures can even stably exist in solution without the DNA origami template. This straightforward approach allows for the fabrication of patterned polymers with low nanometer resolution, which provides access to unique DNA-based functional hybrid materials. PMID:27058968

  6. Activators generated by electron transfer for atom transfer radical polymerization of styrene in the presence of mesoporous silica nanoparticles

    SciTech Connect

    Khezri, Khezrollah; Roghani-Mamaqani, Hossein

    2014-11-15

    Graphical abstract: Effect of mesoporous silica nanoparticles (MCM-41) on the activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is investigated. Decrement of conversion and number average molecular weight and also increment of polydispersity index (PDI) values are three main results of addition of MCM-41 nanoparticles. Incorporation of MCM-41 nanoparticles in the polystyrene matrix can clearly increase thermal stability and decrease glass transition temperature of the nanocomposites. - Highlights: • Spherical morphology, hexagonal structure, and high surface area with regular pore diameters of the synthesized MCM-41 nanoparticles are examined. • AGET ATRP of styrene in the presence of MCM-41 nanoparticles is performed. • Effect of MCM-41 nanoparticles addition on the polymerization rate, conversion and molecular weights of the products are discussed. • Improvement in thermal stability of the nanocomposites and decreasing T{sub g} values was also observed by incorporation of MCM-41 nanoparticles. - Abstract: Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3 wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798 g mol{sup −1}. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2 ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric

  7. Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose

    NASA Astrophysics Data System (ADS)

    Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

    2015-10-01

    This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection.This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. Electronic supplementary information (ESI) available: Experimental details and ESI figures. See DOI: 10.1039/c5nr05716g

  8. Advances in light-induced polymerizations: I. Shadow cure in free radical photopolymerizations II. Experimental and modeling studies of photoinitiator systems for effective polymerizations with LEDs

    NASA Astrophysics Data System (ADS)

    Kitano, Hajime

    Photopolymerization has become the standard for many coating and printing applications that require rapid curing at room temperature due to its potential to reduce volatile organic compound (VOC) emissions while providing a means for efficient manufacturing processes. These advantages could be useful in a variety of emerging applications, such as anisotropic conductive films (ACF) if photopolymerization could extend into relatively narrow shadow regions which are not directly illuminated, and if visible wavelengths that are not absorbed by polyimide films could be used to trigger the reaction. The broad objectives of this research are i) to examine the factors that determine the attainable extent of shadow cure in free radical polymerizations, and ii) to develop initiator systems effective for polymerization using visible light and light emitting diode (LED) lamps. Project I: Shadow Cure in Free Radical Photopolymerizations. In this project, the extent of shadow cure in visible-light-induced free radical photopolymerization is investigated. A number of effective methods such as adding additives, utilizing a reflective stage, and increasing the light intensity are introduced. In addition, the use of fluorescent dyes in multi-component photoinitiator systems proved to be very effective for shadow cure because the fluorescent light emitted from the dye could irradiate the shadow region. When considering practical resins, mixtures of oligomers and monomers, the viscosity is the major barrier that must be overcome in order to achieve high conversion in the shadow regions using visible-light-induced multi-component photoinitiator systems. Hence, instead of using multi-component systems, a commercial visible-light-induced single-component photoinitiator is investigated. As a result, a high conversion in shadow regions of the viscous oligomer containing resin is achieved. Project II: Experimental and Modeling Studies of Photoinitiator Systems for Effective Polymerizations

  9. PolyPEGA with predetermined molecular weights from enzyme-mediated radical polymerization in water.

    PubMed

    Ng, Yeap-Hung; di Lena, Fabio; Chai, Christina L L

    2011-06-14

    The preparation of acrylic polymers with predetermined molecular weights using metalloenzymes as catalysts, ascorbic acid as reducing agent and alkyl halides as initiators is reported. The mechanism of polymerization resembles an ARGET ATRP process. PMID:21552589

  10. Regulated dielectric loss of polymer composites from coating carbon nanotubes with a cross-linked silsesquioxane shell through free-radical polymerization.

    PubMed

    Sun, Da; Zhou, Zheng; Chen, Guang-Xin; Li, Qifang

    2014-11-12

    We report a synthetic strategy for coating multiwalled carbon nanotubes (MWCNTs) with cross-linked octa-methacrylate-polyhedral oligomeric silsesquioxane (MA-POSS) by direct, in situ free-radical polymerization in a controlled manner. This strategy resulted in a core-shell structure with an MWCNT center. The shell thickness could be varied from ∼ 7 nm to 40 nm by choosing different initiators, solvents, and weight ratios of MWCNT and octa-MA-POSS. Coated MWCNT hybrids had controlled electrical performance depending on the coating layer thickness and were well-dispersed in the polymer matrix. POSS-coated MWCNTs were compounded with poly(vinylidene fluoride) to obtain a composite with high dielectric permittivity and low dielectric loss. PMID:25337905

  11. A new approach to network heterogeneity: Polymerization Induced Phase Separation in photo-initiated, free-radical methacrylic systems.

    PubMed

    Szczepanski, Caroline R; Pfeifer, Carmem S; Stansbury, Jeffrey W

    2012-09-28

    Non-reactive, thermoplastic prepolymers (poly- methyl, ethyl and butyl methacrylate) were added to a model homopolymer matrix composed of triethylene glycol dimethacrylate (TEGDMA) to form heterogeneous networks via polymerization induced phase separation (PIPS). PIPS creates networks with distinct phase structure that can partially compensate for volumetric shrinkage during polymerization through localized internal volume expansion. This investigation utilizes purely photo-initiated, free-radical systems, broadening the scope of applications for PIPS since these processing conditions have not been studied previously.The introduction of prepolymer into TEGDMA monomer resulted in stable, homogeneous monomer formulations, most of which underwent PIPS upon photo-irradiation, creating heterogeneous networks. During polymerization the presence of prepolymer enhanced autoacceleration, allowing for a more extensive ambient cure of the material. Phase separation, as characterized by dynamic changes in sample turbidity, was monitored simultaneously with monomer conversion and either preceded or was coincident with network gelation. Dynamic mechanical analysis shows a broadening of the tan delta peak and secondary peak formation, characteristic of phase-separated materials, indicating one phase rich in prepolymer and another depleted form upon phase separation. In certain cases, PIPS leads to an enhanced physical reduction of volumetric shrinkage, which is attractive for many applications including dental composite materials. PMID:23109733

  12. Functional polymeric microparticles engineered from controllable microfluidic emulsions.

    PubMed

    Wang, Wei; Zhang, Mao-Jie; Chu, Liang-Yin

    2014-02-18

    Functional polymeric microparticles with typical sizes of 1-1000 μm have received considerable attention for many applications. Especially in biomedical fields, polymeric microparticles with advanced functions such as targeted delivery, controlled encapsulation, or "capture and release" show great importance as delivery systems for active molecules and drugs, as imaging agents for analytics and diagnostics, as microreactors for confined bioreactions, and more. Generally, the functions of these microparticles rely on both their structures and the properties of their component materials. Thus, creating unique structures from functional materials provides an important strategy for developing advanced functional polymeric microparticles. Several methods, such as dispersion polymerization, precipitation polymerization, copolymer self-assembly, and phase-separated polymer precipitation can be used to make functional microparticles, but each has limitations, for example, their limited control over the particle size and structure. Using emulsions as templates, however, allows precise control over the size, shape, composition, and structure of the resulting microparticles by tuning those of the emulsions via specific emulsification techniques. Microfluidic methods offer excellent control of emulsion droplets, thereby providing a powerful platform for continuous, reproducible, scalable production of polymeric microparticles with unprecedented control over their monodispersity, structures, and compositions. This approach provides broad opportunities for producing polymeric microparticles with novel structure-property combinations and elaborately designed functions. In this Account, we highlight recent efforts in microfluidic fabrication of advanced polymeric microparticles with well-designed functions for potential biomedical applications, and we describe the development of microfluidic techniques for producing monodisperse and versatile emulsion templates. We begin by

  13. Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification

    PubMed Central

    2015-01-01

    The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers’ molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by 1H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods. PMID:25997518

  14. Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification.

    PubMed

    Hedir, Guillaume G; Bell, Craig A; O'Reilly, Rachel K; Dove, Andrew P

    2015-07-13

    The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods. PMID:25997518

  15. Thermally-initiated free radical polymerization for reproducible production of stable linear polyacrylamide coated capillaries, and their application to proteomic analysis using capillary zone electrophoresis-mass spectrometry.

    PubMed

    Zhu, Guijie; Sun, Liangliang; Dovichi, Norman J

    2016-01-01

    Proteomic analysis using capillary zone electrophoresis (CZE) typically is performed with linear polyacrylamide (LPA) coated capillaries. These capillaries both minimize the adsorption of peptides and proteins to the inner wall of the capillary and decrease electroosmosis, which increases the separation capacity. LPA coating protocols were first reported by Hjerten in 1985. Conventional LPA production is based on the use of tetramethylethylenediamine (TEMED) to catalyze the free-radical polymerization that couples acrylamide to a capillary wall that has been pretreated with γ-methacryloxypropyltrimethoxysilane. The treated capillary is filled with a mixture of monomer, TEMED, and ammonium persulfate; free radical polymerization forms the LPA coating. Over many years, we have observed significant variation in the electroosmotic properties of commercial LPA coated capillaries both along the capillary length and between lots. We believe this variation is due to differences in the time between initiation of the reaction and the filling of the capillary. Here, we report a simple method for the generation of very stable and reproducible coatings. In this protocol, the monomer mixture and an ammonium persulfate initiator are introduced into the capillary without TEMED initiator. The mixture is stable and does not begin polymerization at room temperature. The filled capillary is then heated in a water bath to initiate polymerization in a well-controlled manner. A mixture of four standard proteins was used to evaluate the coating performance. Compared with commercialized LPA capillaries, our LPA capillaries generate much better separation performance and superior protein peak shape in CZE analysis. We also analyzed an intact antibody (MW 150K) by CZE-MS with the new LPA capillary in triplicate runs. The intact antibody generated a Gaussian-shaped electrophoresis peak with 1.2% relative standard deviation in migration time and 8.5% in base peak intensity. An automated CZE

  16. A New Hyaluronic Acid Derivative Obtained from Atom Transfer Radical Polymerization as a siRNA Vector for CD44 Receptor Tumor Targeting.

    PubMed

    Palumbo, Fabio Salvatore; Bavuso Volpe, Antonella; Bongiovì, Flavia; Pitarresi, Giovanna; Giammona, Gaetano

    2015-11-01

    Two derivatives of hyaluronic acid (HA) have been synthesized by atom transfer radical polymerization (ATRP), starting from an ethylenediamino HA derivative (HA-EDA) and by using diethylaminoethyl methacrylate (DEAEMA) as a monomer for polymerization. Both samples, indicated as HA-EDA-pDEAEMA a and b, are able to condense siRNA, as determined by gel retardation assay and resulting complexes show a size and a zeta potential value dependent on polymerization number, as determined by dynamic light scattering measurements. In vitro studies performed on HCT 116 cell line, that over express CD44 receptor, demonstrate a receptor mediated uptake of complexes, regardless of their surface charge. PMID:26136372

  17. Electron spin resonance spectra of nitroxyl radicals

    NASA Astrophysics Data System (ADS)

    Botek, Edith; Zarycz, Natalia; Champagne, Benoît; Sciannaméa, Valérie; Detrembleur, Christophe

    2012-12-01

    Hyperfine coupling constants (HFCCs) of nitroxyl radicals were calculated using density functional theory (DFT) to address the structure of nitroxide intermediates in controlled radical polymerization. In a preliminary step, the reliability of different theoretical methods has been substantiated by comparing calculated HFCCs to experimental data for a set of acyclic and cyclic alkylnitroxyl radicals. In a second step this tested approach was applied to support experimental evidence of several nitroxide-mediated polymerization (NMP) reactions.

  18. Picosecond Control of Photogenerated Radical Pair Lifetimes Using a Stable Third Radical.

    PubMed

    Horwitz, Noah E; Phelan, Brian T; Nelson, Jordan N; Krzyaniak, Matthew D; Wasielewski, Michael R

    2016-05-12

    Photoinduced electron transfer reactions in organic donor-acceptor systems leading to long-lived radical ion pairs (RPs) have attracted broad interest for their potential applications in fields as diverse as solar energy conversion and spintronics. We present the photophysics and spin dynamics of an electron donor - electron acceptor - stable radical system consisting of a meta-phenylenediamine (mPD) donor covalently linked to a 4-aminonaphthalene-1,8-dicarboximide (ANI) electron-accepting chromophore as well as an α,γ-bisdiphenylene-β-phenylallyl (BDPA) stable radical. Selective photoexcitation of ANI produces the BDPA-mPD(+•)-ANI(-•) triradical in which the mPD(+•)-ANI(-•) RP spins are strongly exchange coupled. The presence of BDPA is found to greatly increase the RP intersystem crossing rate from the initially photogenerated BDPA-(1)(mPD(+•)-ANI(-•)) to BDPA-(3)(mPD(+•)-ANI(-•)), resulting in accelerated RP recombination via the triplet channel to produce BDPA-mPD-(3*)ANI as compared to a reference molecule lacking the BDPA radical. The RP recombination rates observed are much faster than those previously reported for weakly coupled triradical systems. Time-resolved EPR spectroscopy shows that this process is also associated with strong spin polarization of the stable radical. Overall, these results show that RP intersystem crossing rates can be strongly influenced by stable radicals nearby strongly coupled RP systems, making it possible to use a third spin to control RP lifetimes down to a picosecond time scale. PMID:27108738

  19. Regiochemical control of monolignol radical coupling: a new paradigm for lignin and lignan biosynthesis

    NASA Technical Reports Server (NTRS)

    Gang, D. R.; Costa, M. A.; Fujita, M.; Dinkova-Kostova, A. T.; Wang, H. B.; Burlat, V.; Martin, W.; Sarkanen, S.; Davin, L. B.; Lewis, N. G.

    1999-01-01

    BACKGROUND: Although the lignins and lignans, both monolignol-derived coupling products, account for nearly 30% of the organic carbon circulating in the biosphere, the biosynthetic mechanism of their formation has been poorly understood. The prevailing view has been that lignins and lignans are produced by random free-radical polymerization and coupling, respectively. This view is challenged, mechanistically, by the recent discovery of dirigent proteins that precisely determine both the regiochemical and stereoselective outcome of monolignol radical coupling. RESULTS: To understand further the regulation and control of monolignol coupling, leading to both lignan and lignin formation, we sought to clone the first genes encoding dirigent proteins from several species. The encoding genes, described here, have no sequence homology with any other protein of known function. When expressed in a heterologous system, the recombinant protein was able to confer strict regiochemical and stereochemical control on monolignol free-radical coupling. The expression in plants of dirigent proteins and proposed dirigent protein arrays in developing xylem and in other lignified tissues indicates roles for these proteins in both lignan formation and lignification. CONCLUSIONS: The first understanding of regiochemical and stereochemical control of monolignol coupling in lignan biosynthesis has been established via the participation of a new class of dirigent proteins. Immunological studies have also implicated the involvement of potential corresponding arrays of dirigent protein sites in controlling lignin biopolymer assembly.

  20. Radical graft polymerization of an Allyl Monomer onto Hydrophilic Polymers and their antibacterial nanofibrous membranes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydrophilic poly (vinyl alcohol-co-ethylene) (PVA-co-PE) copolymers with 27 mol %, 32 mol % and 44 mol % ethylene were functionalized by melt radical graft copolymerization with 2,4-diamino-6-diallylamino-1,3,5-triazine (NDAM) using reactive extrusion. This functionalization imparts antibacterial pr...

  1. First multi-reactive dextran-based inisurf for atom transfer radical polymerization in miniemulsion.

    PubMed

    Wu, Man; Forero Ramirez, Laura M; Rodriguez Lozano, Ana; Quémener, Damien; Babin, Jérôme; Durand, Alain; Marie, Emmanuelle; Six, Jean-Luc; Nouvel, Cécile

    2015-10-01

    A multi-reactive polysaccharide-based inisurf (acting both as initiator and stabilizer) has been designed for the first time from dextran with the aim of preparing dextran-covered nanoparticles with covalent linkage between core and coverage. This inisurf was used for polymerizing butyl acrylate in miniemulsion by AGET-ATRP. Both hydrophobic phenoxy groups and initiator groups (bromoisobutyryl ester) were introduced within hydrophilic dextran chain, conferring it amphiphilic and macroinitiator characters. Amphiphilic properties of dextran inisurfs have been evidenced as well as their ability to stabilize the direct miniemulsion of n-butyl acrylate. After optimization of polymerization conditions with model studies, assays were successfully realized with dextran-based inisurfs. Because of their amphiphilic character, inisurfs migrated at oil/water interface and initiated polymerization from bromoisobutyryl ester groups. Therefore graft copolymers were produced at oil/water interface, due to the multifunctional character of these inisurfs and constituted the particle inner core with covalent links to the dextran coverage. PMID:26076610

  2. Preparation of Core-Shell Hybrid Compounds by Atomic Transfer Radical Polymerization and Its Application to Plastic Lens of Headlamp.

    PubMed

    Noh, Seung-Man; Ahn, Jae-Beum; Choi, Ki-Hyun; Park, Seung-Kyu

    2015-09-01

    Nano silica ball (NSB) core polymethylmethacrylate (PMMA) shell hybrid nanocomposites were synthesized by atomic transfer radical polymerization (ATRP) method for the application to the clearcoat to enhance scratch resistance. The characteristics of the synthesized inorganic/organic hybrid material were examined by scanning electron microscope (SEM), particle size analysis, Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis-differential scanning calorimetry (TGA-DSC). The scratch resistance and light transmittance of the clearcoat were measured by a nano-scratch tester and UV-visible spectroscopy, respectively. The average particle size of the NSB-PMMA hybrid compounds was 30 nm with narrow size distribution. Even 0.1 wt% loading of NSB-PMMA in the clearcoat dramatically enhanced the scratch resistance, about 40% increase in the force of the first fracture, while slightly reduced the light transmittance, about 5% only. PMID:26716303

  3. Reverse atom transfer radical polymerization (RATRP) for anti-clotting PU-LaCl3-g-P(MPC) films

    NASA Astrophysics Data System (ADS)

    Lu, Chunyan; Zhou, Ninglin; Xiao, Yinghong; Tang, Yida; Jin, Suxing; Wu, Yue; Shen, Jian

    2013-01-01

    Low grafting density is a disadvantage both in reverse atom transfer radical polymerization (RATRP) and ATRP. In this work, the surfaces of polyurethane (PU) were treated by LaCl3·6H2O to obtain modified surfaces with hydrated layers. The reaction of surface-initiated RATRP was carried out easily, which may be attributed to the enriched hydroxyl groups on the hydrated layers. An innovation found in this work is that some free lanthanum ions (La3+) reacted with the silane coupling agent (CPTM) and the product served as mixed ligand complex. The mixed ligand complex instead of conventional 2,2‧-bipyridine was adopted to serve as a ligand in the process of RATRP. As a result, PU surfaces grafted with well-defined polymer brushes (MPC) were obtained. PU substrates before and after modification were characterized by FTIR, XPS, AFM, SEM, SCA, respectively. The results showed that zwitterionic brushes were successfully fabricated on the PU surfaces (P(MPC)), and the content of the grafted layer increased gradually with polymerization time with the grafting density as high as 97.9%. The blood compatibility of the PU substrates was evaluated by plasma recalcification profiles test and platelet adhesion tests in vitro. It was found that all PU functionalized with zwitterionic brush showed improved resistance to nonspecific protein adsorption and platelet adhesion.

  4. Electroless plating of copper on polyimide films modified by surface-initiated atom-transfer radical polymerization of 4-vinylpyridine

    NASA Astrophysics Data System (ADS)

    Li, Liang; Yan, Guoping; Wu, Jiangyu; Yu, Xianghua; Guo, Qingzhong; Kang, Entang

    2008-09-01

    Surface modification of polyimide (PI) films were first carried out by chloromethylation under mild conditions, followed by surface-initiated atom-transfer radical polymerization (ATRP) of 4-vinylpyridine (4VP) from the chloromethylated PI surfaces. The composition and topography of the PI surfaces modified by poly(4-vinylpyridine) (P4VP) were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The P4VP brushes with well-preserved pyridine groups on the PI surface was used not only as the chemisorption sites for the palladium complexes without prior sensitization by SnCl 2 solution during the electroless plating of copper, but also as an adhesion promotion layer to enhance the adhesion of the electrolessly deposited copper to the PI surfaces. The T-peel adhesion strength of the electrolessly deposited copper on the modified PI surface could reach about 6.6 N/cm. Effects of the polymerization time and the activation time in the PdCl 2 solution on the T-peel adhesion strength of the electrolessly deposited copper in the Sn-free process to the modified PI surface were also studied.

  5. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization from Chlorinated Polypropylene and Polyethylene Trunk Fibers

    DOE PAGESBeta

    Brown, Suree; Chatterjee, Sabornie; Li, Meijun; Yue, Yanfeng; Tsouris, Costas; Janke, Christopher J.; Saito, Tomonori; Dai, Sheng

    2015-12-10

    Seawater contains a large amount of uranium (~4.5 billion tons) which can serve as a limitless supply of an energy source. However, in order to make the recovery of uranium from seawater economically feasible, lower manufacturing and deployment costs are required, and thus, solid adsorbents must have high uranium uptake, reusability, and high selectivity toward uranium. In this study, atom-transfer radical polymerization (ATRP), without the radiation-induced graft polymerization (RIGP), was used for grafting acrylonitrile (AN) and tert-butyl acrylate (tBA) from a new class of trunk fibers, forming adsorbents in a readily deployable form. The new class of trunk fibers wasmore » prepared by the chlorination of PP round fiber, hollow-gear-shaped PP fiber, and hollow-gear-shaped PE fiber. During ATRP, degrees of grafting (d.g.) varied according to the structure of active chlorine sites on trunk fibers and ATRP conditions, and the d.g. as high as 2570% was obtained. Resulting adsorbent fibers were evaluated in U-spiked simulated seawater and the maximum adsorption capacity of 146.6 g U/kg, much higher than that of a standard adsorbent JAEA fiber (75.1 g/kg), was obtained. This new type of trunk fibers can be used for grafting a variety of uranium-interacting ligands, including designed ligands that are highly selective toward uranium.« less

  6. Effect of Surface Charge on Surface-Initiated Atom Transfer Radical Polymerization from Cellulose Nanocrystals in Aqueous Media.

    PubMed

    Zoppe, Justin O; Xu, Xingyu; Känel, Cindy; Orsolini, Paola; Siqueira, Gilberto; Tingaut, Philippe; Zimmermann, Tanja; Klok, Harm-Anton

    2016-04-11

    Cellulose nanocrystals (CNCs) with different charge densities were utilized to examine the role of electrostatic interactions on surface-initiated atom transfer radical polymerization (SI-ATRP) in aqueous media. To this end, growth of hydrophilic uncharged poly(N,N-dimethylacrylamide) (PDMAM) brushes was monitored by electrophoresis, (1)H NMR spectroscopy, and dynamic light scattering (DLS). Molecular weight and polydispersity of PDMAM brushes was determined by GPC analysis of hydrolytically cleaved polymers. Initiator and polymer brush grafting densities, and thus, initiator efficiencies were derived from elemental analysis. Higher initiator efficiency of polymer brush growth was observed for CNCs with higher anionic surface sulfate half-ester group density, but at the expense of high polydispersity caused by inefficient deactivation. PDMAM grafts with number-average molecular weights up to 530 kDa and polydispersity indices <1.5 were obtained under highly diluted monomer concentrations. The role of surface chemistry on the growth of neutral polymer brushes from CNCs in water is emphasized and a model of the interfacial region at the onset of polymerization is proposed. The results presented here could have implications for other substrates that present surface charges and for the assumption that the kinetics of Cu-mediated SI-CRP are analogous to those conducted in solution. PMID:26901869

  7. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization from Chlorinated Polypropylene and Polyethylene Trunk Fibers

    SciTech Connect

    Brown, Suree; Chatterjee, Sabornie; Li, Meijun; Yue, Yanfeng; Tsouris, Costas; Janke, Christopher J.; Saito, Tomonori; Dai, Sheng

    2015-12-10

    Seawater contains a large amount of uranium (~4.5 billion tons) which can serve as a limitless supply of an energy source. However, in order to make the recovery of uranium from seawater economically feasible, lower manufacturing and deployment costs are required, and thus, solid adsorbents must have high uranium uptake, reusability, and high selectivity toward uranium. In this study, atom-transfer radical polymerization (ATRP), without the radiation-induced graft polymerization (RIGP), was used for grafting acrylonitrile (AN) and tert-butyl acrylate (tBA) from a new class of trunk fibers, forming adsorbents in a readily deployable form. The new class of trunk fibers was prepared by the chlorination of PP round fiber, hollow-gear-shaped PP fiber, and hollow-gear-shaped PE fiber. During ATRP, degrees of grafting (d.g.) varied according to the structure of active chlorine sites on trunk fibers and ATRP conditions, and the d.g. as high as 2570% was obtained. Resulting adsorbent fibers were evaluated in U-spiked simulated seawater and the maximum adsorption capacity of 146.6 g U/kg, much higher than that of a standard adsorbent JAEA fiber (75.1 g/kg), was obtained. This new type of trunk fibers can be used for grafting a variety of uranium-interacting ligands, including designed ligands that are highly selective toward uranium.

  8. PREPARATION OF BLOCK COPOLYMERS OF POLY(STYRENE) AND POLY(T-BUTYL ACRYLATE) OF VARIOUS MOLECULAR WEIGHTS AND ARCHITECTURES BY ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

    EPA Science Inventory

    Block copolymers of polystyrene and poly(t-butyl acrylate) were prepared using atom transfer radical polymerization techniques. These polymers were synthesized with a CuBr/N,N,N,NFree Radical Addition Polymerization Kinetics without Steady-State Approximations: A Numerical Analysis for the Polymer, Physical, or Advanced Organic Chemistry Course

    ERIC Educational Resources Information Center

    Iler, H. Darrell; Brown, Amber; Landis, Amanda; Schimke, Greg; Peters, George

    2014-01-01

    A numerical analysis of the free radical addition polymerization system is described that provides those teaching polymer, physical, or advanced organic chemistry courses the opportunity to introduce students to numerical methods in the context of a simple but mathematically stiff chemical kinetic system. Numerical analysis can lead students to an…

  9. Preparation of a thick polymer brush layer composed of poly(2-methacryloyloxyethyl phosphorylcholine) by surface-initiated atom transfer radical polymerization and analysis of protein adsorption resistance.

    PubMed

    Inoue, Yuuki; Onodera, Yuya; Ishihara, Kazuhiko

    2016-05-01

    The purpose of this study was to prepare a thick polymer brush layer composed of poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) and assess its resistance to protein adsorption from the dissolved state of poly(MPC) chains in an aqueous condition. The thick poly(MPC) brush layer was prepared through the surface-initiated atom transfer radical polymerization (SI-ATRP) of MPC with a free initiator from an initiator-immobilized substrate at given [Monomer]/[Free initiator] ratios. The ellipsometric thickness of the poly(MPC) brush layers could be controlled by the polymerization degree of the poly(MPC) chains. The thickness of the poly(MPC) brush layer in an aqueous medium was larger than that in air, and this tendency became clearer when the polymerization degree of the poly(MPC) increased. The maximum thickness of the poly(MPC) brush layer in an aqueous medium was around 110nm. The static air contact angle of the poly(MPC) brush layer in water indicated a reasonably hydrophilic nature, which was independent of the thickness of the poly(MPC) brush layer at the surface. This result occurred because the hydrated state of the poly(MPC) chains is not influenced by the environment surrounding them. Finally, as measured with a quartz crystal microbalance, the amount of protein adsorbed from a fetal bovine serum solution (10% in phosphate-buffered saline) on the original substrate was 420ng/cm(2). However, the poly(MPC) brush layer reduced this value dramatically to less than 50ng/cm(2). This effect was independent of the thickness of the poly(MPC) brush layer for thicknesses between 20nm and about 110nm. These results indicated that the surface covered with a poly(MPC) brush layer is a promising platform to avoid biofouling and could also be applied to analyze the reactions of biological molecules with a high signal/noise ratio. PMID:26896657

  10. Kinetics of a methyl methacrylate polymerization initiated by the stable free radicals in irradiated polytetrafluoroethylene and properties of the resultant graft polymer

    SciTech Connect

    Donato, K.A.E.

    1987-01-01

    The kinetics of the polymerization of methyl methacrylate (MMA) initiated by the stable free radicals in commercially available irradiated polytetrafluoroethylene micropowder and the rheological, thermal, chemical, and mechanical properties of the resultant graft polymer are described. Test tube runs using different ratios of MMA to PTFE were made to determine the feasibility of the reaction and optimum reaction conditions. The amount of graft produced was equal to the weight gain of the solids after removal of the adventitious homopolymer by extraction in acetone. Test quantities of material were produced in a 500 milliliter agitated reactor. A higher ratio of PTFE to excess MMA and longer reaction times result in higher conversion in test tubes. A kinetic model was developed to relate the original concentration of PTFE free radical to the amount of MMA polymer. Graft polymer containing PTFE micropowder, PMMA graft, and PMMA homopolymer in a ratio of 18:5:1 was used for property characterization. The graft material extrudes well at 513K and has a viscosity comparable to that of PMMA homopolymer. The material is stable upon re-extrusion. DSC thermograms show that the heat of transition of the PTFE melting peak is proportional to the amount of PTFE in the sample. Good solvents for PMMA are detrimental to the structural integrity of the graft extrudate; heat treatment improves the chemical resistance. The PTFE block controls the mechanical properties of the graft.

  11. Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate.

    PubMed

    Xia, Hesheng; Wang, Qi; Liao, Yongqin; Xu, Xi; Baxter, Steven M; Slone, Robert V; Wu, Shuguang; Swift, Graham; Westmoreland, David G

    2002-07-01

    The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared. PMID:12154689

  12. Self-assembly of well-defined polyacrylamide-polystyrene copolymer on fibrillar clays via ultrasonic-assisted surface-initiated atom transfer radical polymerization.

    PubMed

    Liu, Peng; Wang, Tingmei; Su, Zhixing

    2006-06-01

    Well-defined polyacrylamide-polystyrene copolymers were grafted from the fibrillar clay, attapulgite, by a four-step self-assembly process: (i) the gamma-aminopropyltriethoxyl silane was self-assembled onto the surfaces of the attapulgite; (ii) the surface amino groups were amidated with bromoacetylbromide; (iii) the bromo-acetamide modified attapulgite was used as macro-initiator for the surface-initiated atom transfer radical polymerization of styrene with the catalyst of the complex of 1,10-phenanthroline and Cu(I)Br; (iv) the polystyrene grafted attapulgite was then used as macroinitiator for the polymerization of acrylamide. The two steps of the surface-initiated atom transfer radical polymerizations were all conducted under ultrasonic irradiation at room temperature. The product, polyacrylamide-polystyrene copolymers grafted attapulgite, had been characterized with elemental analysis, Fourier transform infrared spectroscopy, Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy. PMID:17025071

  13. Skylab D024 thermal control coatings and polymeric films experiment

    NASA Technical Reports Server (NTRS)

    Lehn, William L.; Hurley, Charles J.

    1992-01-01

    The Skylab D024 Thermal Control Coatings and Polymeric Films Experiment was designed to determine the effects of the external Skylab space environment on the performance and properties of a wide variety of selected thermal control coatings and polymeric films. Three duplicate sets of thermal control coatings and polymeric films were exposed to the Skylab space environment for varying periods of time during the mission. The specimens were retrieved by the astronauts during extravehicular activities (EVA) and placed in hermetically sealed return containers, recovered, and returned to the Wright Laboratory/Materials Laboratory/WPAFB, Ohio for analysis and evaluation. Postflight analysis of the three sets of recovered thermal control coatings indicated that measured changes in specimen thermo-optical properties were due to a combination of excessive contamination and solar degradation of the contaminant layer. The degree of degradation experienced over-rode, obscured, and compromised the measurement of the degradation of the substrate coatings themselves. Results of the analysis of the effects of exposure on the polymeric films and the contamination observed are also presented. The D024 results were used in the design of the LDEF M0003-5 Thermal Control Materials Experiment. The results are presented here to call to the attention of the many other LDEF experimenters the wealth of directly related, low earth orbit, space environmental exposure data that is available from the ten or more separate experiments that were conducted during the Skylab mission. Results of these experiments offer data on the results of low altitude space exposure on materials recovered from space with exposure longer than typical STS experiments for comparison with the LDEF results.

  14. Shape Control in Engineering of Polymeric Nanoparticles for Therapeutic Delivery

    PubMed Central

    Williford, John-Michael; Santos, Jose Luis; Shyam, Rishab; Mao, Hai-Quan

    2015-01-01

    Nanoparticle-mediated delivery of therapeutics holds great potential for the diagnosis and treatment of a wide range of diseases. Significant advances have been made in the design of new polymeric nanoparticle carriers through modulation of their physical and chemical structures and biophysical properties. Nanoparticle shape has been increasingly proposed as an important attribute dictating their transport properties in biological milieu. In this review, we highlight three major methods for preparing polymeric nanoparticles that allow for exquisite control of particle shape. Special attention is given to various approaches to controlling nanoparticle shape by tuning copolymer structural parameters and assembly conditions. This review also provides comparisons of these methods in terms of their unique capabilities, materials choices, and specific delivery cargos, and summarizes the biological effects of nanoparticle shape on transport properties at the tissue and cellular levels. PMID:26146550

  15. Non-local photo-polymerization kinetics including multiple termination mechanisms and dark reactions: Part III. Primary radical generation and inhibition

    SciTech Connect

    Gleeson, Michael R.; Liu Shui; Guo Jinxin; Sheridan, John T.

    2010-09-15

    Photopolymers are playing an ever more important role in diverse areas of research such as holographic data storage, hybrid photonic circuits, and solitary waves. In each of these applications, the production of primary radicals is the driving force of the polymerization processes. Therefore an understanding of the production, removal, and scavenging processes of free radicals in a photopolymer system is crucial in determining a material's response to a given exposure. One such scavenging process is inhibition. In this paper the non-local photo-polymerization driven diffusion model is extended to more accurately model the effects of (i) time varying primary radical production, (ii) the rate of removal of photosensitizer, and (iii) inhibition. The model is presented to specifically analyze the effects of inhibition, which occur most predominantly at the start of grating growth, and comparisons between theory and experiment are performed which quantify these effects.

  16. Controlled release of ethylene via polymeric films for food packaging

    NASA Astrophysics Data System (ADS)

    Pisano, Roberto; Bazzano, Marco; Capozzi, Luigi Carlo; Ferri, Ada; Sangermano, Marco

    2015-12-01

    In modern fruit supply chain a common method to trigger ripening is to keep fruits inside special chambers and initiate the ripening process through administration of ethylene. Ethylene is usually administered through cylinders with inadequate control of its final concentration in the chamber. The aim of this study is the development of a new technology to accurately regulate ethylene concentration in the atmosphere where fruits are preserved: a polymeric film, containing an inclusion complex of α-cyclodextrin with ethylene, was developed. The complex was prepared by molecular encapsulation which allows the entrapment of ethylene into the cavity of α-cyclodextrin. After encapsulation, ethylene can be gradually released from the inclusion complex and its release rate can be regulated by temperature and humidity. The inclusion complex was dispersed into a thin polymeric film produced by UV-curing. This method was used because is solvent-free and involves low operating temperature; both conditions are necessary to prevent rapid release of ethylene from the film. The polymeric films were characterized with respect to thermal behaviour, crystalline structure and kinetics of ethylene release, showing that can effectively control the release of ethylene within confined volume.

  17. Reticulated Nanoporous Polymers by Controlled Polymerization-Induced Microphase Separation

    SciTech Connect

    Seo, Myungeun; Hillmyer, Marc A.

    2013-04-08

    Materials with percolating mesopores are attractive for applications such as catalysis, nanotemplating, and separations. Polymeric frameworks are particularly appealing because the chemical composition and the surface chemistry are readily tunable. We report on the preparation of robust nanoporous polymers with percolating pores in the 4- to 8-nanometer range from a microphase-separated bicontinuous precursor. We combined polymerization-induced phase separation with in situ block polymer formation from a mixture of multifunctional monomers and a chemically etchable polymer containing a terminal chain transfer agent. This marriage results in microphase separation of the mixture into continuous domains of the etchable polymer and the emergent cross-linked polymer. Precise control over pore size distribution and mechanical integrity renders these materials particularly suited for various advanced applications.

  18. A strategy for sequence control in vinyl polymers via iterative controlled radical cyclization.

    PubMed

    Hibi, Yusuke; Ouchi, Makoto; Sawamoto, Mitsuo

    2016-01-01

    There is a growing interest in sequence-controlled polymers toward advanced functional materials. However, control of side-chain order for vinyl polymers has been lacking feasibility in the field of polymer synthesis because of the inherent feature of chain-growth propagation. Here we show a general and versatile strategy to control sequence in vinyl polymers through iterative radical cyclization with orthogonally cleavable and renewable bonds. The proposed methodology employs a repetitive and iterative intramolecular cyclization via a radical intermediate in a one-time template with a radical-generating site at one end and an alkene end at the other, each of which is connected to a linker via independently cleavable and renewable bonds. The unique design specifically allowed control of radical addition reaction although inherent chain-growth intermediate (radical species) was used, as well as the iterative cycle and functionalization for resultant side chains, to lead to sequence-controlled vinyl polymers (or oligomers). PMID:26996881

  19. A strategy for sequence control in vinyl polymers via iterative controlled radical cyclization

    PubMed Central

    Hibi, Yusuke; Ouchi, Makoto; Sawamoto, Mitsuo

    2016-01-01

    There is a growing interest in sequence-controlled polymers toward advanced functional materials. However, control of side-chain order for vinyl polymers has been lacking feasibility in the field of polymer synthesis because of the inherent feature of chain-growth propagation. Here we show a general and versatile strategy to control sequence in vinyl polymers through iterative radical cyclization with orthogonally cleavable and renewable bonds. The proposed methodology employs a repetitive and iterative intramolecular cyclization via a radical intermediate in a one-time template with a radical-generating site at one end and an alkene end at the other, each of which is connected to a linker via independently cleavable and renewable bonds. The unique design specifically allowed control of radical addition reaction although inherent chain-growth intermediate (radical species) was used, as well as the iterative cycle and functionalization for resultant side chains, to lead to sequence-controlled vinyl polymers (or oligomers). PMID:26996881

  1. A strategy for sequence control in vinyl polymers via iterative controlled radical cyclization

    NASA Astrophysics Data System (ADS)

    Hibi, Yusuke; Ouchi, Makoto; Sawamoto, Mitsuo

    2016-03-01

    There is a growing interest in sequence-controlled polymers toward advanced functional materials. However, control of side-chain order for vinyl polymers has been lacking feasibility in the field of polymer synthesis because of the inherent feature of chain-growth propagation. Here we show a general and versatile strategy to control sequence in vinyl polymers through iterative radical cyclization with orthogonally cleavable and renewable bonds. The proposed methodology employs a repetitive and iterative intramolecular cyclization via a radical intermediate in a one-time template with a radical-generating site at one end and an alkene end at the other, each of which is connected to a linker via independently cleavable and renewable bonds. The unique design specifically allowed control of radical addition reaction although inherent chain-growth intermediate (radical species) was used, as well as the iterative cycle and functionalization for resultant side chains, to lead to sequence-controlled vinyl polymers (or oligomers).

  2. UV-Induced Radical Photo-Polymerization: A Smart Tool for Preparing Polymer Electrolyte Membranes for Energy Storage Devices.

    PubMed

    Nair, Jijeesh R; Chiappone, Annalisa; Destro, Matteo; Jabbour, Lara; Zeng, Juqin; Di Lupo, Francesca; Garino, Nadia; Meligrana, Giuseppina; Francia, Carlotta; Gerbaldi, Claudio

    2012-01-01

    In the present work, the preparation and characterization of quasi-solid polymer electrolyte membranes based on methacrylic monomers and oligomers, with the addition of organic plasticizers and lithium salt, are described. Noticeable improvements in the mechanical properties by reinforcement with natural cellulose hand-sheets or nanoscale microfibrillated cellulose fibers are also demonstrated. The ionic conductivity of the various prepared membranes is very high, with average values approaching 10-3 S cm-1 at ambient temperature. The electrochemical stability window is wide (anodic breakdown voltages > 4.5 V vs. Li in all the cases) along with good cyclability in lithium cells at ambient temperature. The galvanostatic cycling tests are conducted by constructing laboratory-scale lithium cells using LiFePO4 as cathode and lithium metal as anode with the selected polymer electrolyte membrane as the electrolyte separator. The results obtained demonstrate that UV induced radical photo-polymerization is a well suited method for an easy and rapid preparation of easy tunable quasi-solid polymer electrolyte membranes for energy storage devices. PMID:24958178

  3. UV-Induced Radical Photo-Polymerization: A Smart Tool for Preparing Polymer Electrolyte Membranes for Energy Storage Devices.

    PubMed

    Nair, Jijeesh R; Chiappone, Annalisa; Destro, Matteo; Jabbour, Lara; Meligrana, Giuseppina; Gerbaldi, Claudio

    2012-01-01

    In the present work, the preparation and characterization of quasi-solid polymer electrolyte membranes based on methacrylic monomers and oligomers, with the addition of organic plasticizers and lithium salt, are described. Noticeable improvements in the mechanical properties by reinforcement with natural cellulose hand-sheets or nanoscale microfibrillated cellulose fibers are also demonstrated. The ionic conductivity of the various prepared membranes is very high, with average values approaching 10-3 S cm-1 at ambient temperature. The electrochemical stability window is wide (anodic breakdown voltages > 4.5 V vs. Li in all the cases) along with good cyclability in lithium cells at ambient temperature. The galvanostatic cycling tests are conducted by constructing laboratory-scale lithium cells using LiFePO4 as cathode and lithium metal as anode with the selected polymer electrolyte membrane as the electrolyte separator. The results obtained demonstrate that UV induced radical photo-polymerization is a well suited method for an easy and rapid preparation of easy tunable quasi-solid polymer electrolyte membranes for energy storage devices. PMID:24958425

  4. Preparation of 17β-estradiol-imprinted material by surface-initiated atom transfer radical polymerization and its application.

    PubMed

    Gong, Yanru; Niu, Yuling; Gong, Xiaohan; Ma, Meihua; Ren, Xiaowei; Zhu, Weihua; Luo, Ruiming; Gong, Bolin

    2015-04-01

    A novel 17β-estradiol molecularly imprinted polymer was grafted onto the surface of initiator-immobilized silica by surface-initiated atom transfer radical polymerization. The resulting molecularly imprinted polymer was characterized by elemental analysis and thermogravimetric analysis. The binding property of molecularly imprinted polymer for 17β-estradiol was also studied with both static and dynamic methods. The results showed that the molecularly imprinted polymer possessed excellent recognition capacity for 17β-estradiol (180.65 mg/g at 298 K), and also exhibited outstanding selectivity for 17β-estradiol over the other competitive compounds (such as testosterone and progesterone). Then, the determination of trace 17β-estradiol in beef samples was successfully developed by using molecularly imprinted polymer solid-phase extraction coupled with high-performance liquid chromatography. The limit of detection was 0.25 ng/mL, and the amount of 17β-estradiol in beef samples was detected at 2.83 ng/g. This work proposed a sensitive, rapid, reliable, and convenient approach for the determination of trace 17β-estradiol in complicated beef samples. PMID:25619938

  5. Protein-resistant polyurethane via surface-initiated atom transfer radical polymerization of oligo(ethylene glycol) methacrylate.

    PubMed

    Jin, Zhilin; Feng, Wei; Zhu, Shiping; Sheardown, Heather; Brash, John L

    2009-12-15

    Protein-resistant polyurethane (PU) surfaces were prepared by surface-initiated simultaneous normal and reverse atom transfer radical polymerization (s-ATRP) of poly(oligo(ethylene glycol) methacrylate) (poly (OEGMA)). Oxygen plasma treatment was employed for initial activation of the PU surface. The grafted polymer chain length was adjusted by varying the molar ratio of monomer to sacrificial initiator in solution from 5:1 to 200:1. The modified PU surfaces were characterized by water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Protein adsorption experiments from tris-buffered saline (TBS) and plasma were carried out to evaluate the protein-resistance of the surfaces. Adsorption from single and binary protein solutions as well as from plasma was significantly reduced after modification. Adsorption decreased with increasing poly(OEGMA) chain length. Fibrinogen (Fg) adsorption on the 200:1 monomer/initiator surface was in the range of 3-33 ng/cm(2) representing 96-99% reduction compared with the unmodified PU. Fg adsorption from 0.01-10% plasma was as low as 1-5 ng/cm(2). Moreover, binary protein adsorption experiments using Fg and lysozyme (Lys) showed that protein size is a factor in the protein resistance of these surfaces. PMID:19148931

  6. Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

    NASA Astrophysics Data System (ADS)

    Wang, Jingjing; Wei, Jun

    2016-09-01

    Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

  7. Synthesis of zwitterionic polymer-based amphiphilic triblock copolymers by atom transfer radical polymerization for production of extremely stable nanoemlusions

    NASA Astrophysics Data System (ADS)

    Lee, Jin Yong; Kim, Ji Eun; Kim, Jin Woong

    2015-03-01

    In fields of soft matter, there have been growing interests in utilizing amphiphilic block copolymers due to their intriguing properties, such as surface activity as well as self-assembly. In this work, we synthesize a series of poly (2-(methacryloyloxy) ethyl phosphorylcholine)- b-poly (ɛ-caprolactone)- b-poly (2-(methacryloyloxy) ethyl phosphorylcholine) (PMPC- b-PCL- b-PMPC) triblock copolymers by using atom transfer radical polymerization (ATRP). We have a particular interest in using poly (2-(methacryloyloxy) ethyl phosphorylcholine) (PMPC) as a hydrophilic block, since it can have both electrostatic repulsion and steric repulsion in complex fluid systems. Assembling them at the oil-water interface by using the phase inversion method enables production of highly stable nanoemulsions. From the analyses of the crystallography and self-assembly behavior, we have found that the triblock copolymers assemble to form a flexible but tough molecular thin film at the interface, which is essential for the remarkable improvement in the emulsion stability.

  8. UV-Induced Radical Photo-Polymerization: A Smart Tool for Preparing Polymer Electrolyte Membranes for Energy Storage Devices

    PubMed Central

    Nair, Jijeesh R.; Chiappone, Annalisa; Destro, Matteo; Jabbour, Lara; Meligrana, Giuseppina; Gerbaldi, Claudio

    2012-01-01

    In the present work, the preparation and characterization of quasi-solid polymer electrolyte membranes based on methacrylic monomers and oligomers, with the addition of organic plasticizers and lithium salt, are described. Noticeable improvements in the mechanical properties by reinforcement with natural cellulose hand-sheets or nanoscale microfibrillated cellulose fibers are also demonstrated. The ionic conductivity of the various prepared membranes is very high, with average values approaching 10-3 S cm-1 at ambient temperature. The electrochemical stability window is wide (anodic breakdown voltages > 4.5 V vs. Li in all the cases) along with good cyclability in lithium cells at ambient temperature. The galvanostatic cycling tests are conducted by constructing laboratory-scale lithium cells using LiFePO4 as cathode and lithium metal as anode with the selected polymer electrolyte membrane as the electrolyte separator. The results obtained demonstrate that UV induced radical photo-polymerization is a well suited method for an easy and rapid preparation of easy tunable quasi-solid polymer electrolyte membranes for energy storage devices. PMID:24958425

  9. UV-Induced Radical Photo-Polymerization: A Smart Tool for Preparing Polymer Electrolyte Membranes for Energy Storage Devices

    PubMed Central

    Nair, Jijeesh R.; Chiappone, Annalisa; Destro, Matteo; Jabbour, Lara; Zeng, Juqin; Lupo, Francesca Di; Garino, Nadia; Meligrana, Giuseppina; Francia, Carlotta; Gerbaldi, Claudio

    2012-01-01

    In the present work, the preparation and characterization of quasi-solid polymer electrolyte membranes based on methacrylic monomers and oligomers, with the addition of organic plasticizers and lithium salt, are described. Noticeable improvements in the mechanical properties by reinforcement with natural cellulose hand-sheets or nanoscale microfibrillated cellulose fibers are also demonstrated. The ionic conductivity of the various prepared membranes is very high, with average values approaching 10−3 S cm−1 at ambient temperature. The electrochemical stability window is wide (anodic breakdown voltages > 4.5 V vs. Li in all the cases) along with good cyclability in lithium cells at ambient temperature. The galvanostatic cycling tests are conducted by constructing laboratory-scale lithium cells using LiFePO4 as cathode and lithium metal as anode with the selected polymer electrolyte membrane as the electrolyte separator. The results obtained demonstrate that UV induced radical photo-polymerization is a well suited method for an easy and rapid preparation of easy tunable quasi-solid polymer electrolyte membranes for energy storage devices. PMID:24958178

  10. Robust Thick Polymer Brushes Grafted from Gold Surfaces Using Bidentate Thiol-Based Atom-Transfer Radical Polymerization Initiators.

    PubMed

    Park, Chul Soon; Lee, Han Ju; Jamison, Andrew C; Lee, T Randall

    2016-03-01

    A new bromoisobutyrate-terminated alkanethiol, 16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl 2-bromo-2-methylpropanoate (BMTBM), was designed as a bidentate adsorbate to form thermally stable bromoisobutyrate-terminated self-assembled monolayers (SAMs) on flat gold surfaces to conduct atom-transfer radical polymerizations (ATRPs). The monolayers derived from BMTBM were characterized by ellipsometry, X-ray photoelectron spectroscopy (XPS), and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to the monolayers formed from 16-mercaptohexadecyl 2-bromo-2-methylpropanoate (MBM), 16-(3-(mercaptomethyl)phenoxy)hexadecyl 2-bromo-2-methyl-propanoate (MTBM), and octadecanethiol (C18SH). In this study, although the monolayer derived from BMTBM was less densely packed than those derived from MBM and MTBM, the bidentate adsorbates demonstrated much higher thermal stability in solution-phase thermal desorption tests, owing to the "chelate effect". The enhanced stability of the BMTBM SAMs ensured the development of thick brushes of poly(methyl methacrylate) and polystyrene at elevated temperatures (60, 90, 105, and 120 °C). In contrast, SAMs derived from MBM and MTBM failed to grow polymer brushes at temperatures above 100 °C. PMID:26841087

  11. In situ development of self-reinforced cellulose nanocrystals based thermoplastic elastomers by atom transfer radical polymerization.

    PubMed

    Yu, Juan; Wang, Chunpeng; Wang, Jifu; Chu, Fuxiang

    2016-05-01

    Recently, the utilization of cellulose nanocrystals (CNCs) as a reinforcing material has received a great attention due to its high elastic modulus. In this article, a novel strategy for the synthesis of self-reinforced CNCs based thermoplastic elastomers (CTPEs) is presented. CNCs were first surface functionalized with an initiator for surface-initiated atom transfer radical polymerization (SI-ATRP). Subsequently, SI-ATRP of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in the presence of sacrificial initiator to form CTPEs in situ. The CTPEs together with the simple blends of CNCs and linear poly(MMA-co-BA) copolymer (P(MMA-co-BA)) were characterized for comparative study. The results indicated that P(MMA-co-BA) was successfully grafted onto the surface of CNCs and the compatibility between CNCs and the polymer matrix in CTPEs was greatly enhanced. Specially, the CTPEs containing 2.15wt% CNCs increased Tg by 19.2°C and tensile strength by 100% as compared to the linear P(MMA-co-BA). PMID:26877006

  12. Electron beam triggered, free radical polymerization-derived monolithic capillary columns for high-performance liquid chromatography.

    PubMed

    Schlemmer, Bettina; Bandari, Rajendar; Rosenkranz, Lutz; Buchmeiser, Michael R

    2009-03-27

    Monolithic capillary columns were prepared via electron beam triggered free radical polymerization within the confines of 0.2 and 0.1mm I.D. capillary columns using ethyl methacrylate and trimethylolpropane triacrylate as monomers as well as 2-propanol, 1-dodecanol and toluene as porogenic system. The influence of column diameter on reproducibility and separation performance was investigated. For evaluation, a protein standard consisting of five proteins in the range of 5800-66,000 g mol(-1) was used. Reproducibility was checked by determining the relative standard deviations in retention times, peak widths at half height, asymmetry and resolution. Excellent run-to-run reproducibility was found for both 0.2 and 0.1mm I.D. columns; batch-to-batch reproducibility was good for both column types. In order to enhance the non-polar character of the monolithic columns, lauryl methacrylate-based capillary columns were prepared. These were successfully used for the separation of proteins and a cytochrome c digest. PMID:18809181

  13. Lack of influence of extracellular polymeric substances (EPS) level on hydroxyl radical mediated disinfection of Escherichia coli.

    PubMed

    Gong, Amy S; Lanzl, Caylyn A; Cwiertny, David M; Walker, Sharon L

    2012-01-01

    Photolysis of nitrate, a prevalent constituent in agriculturally impacted waters, may influence pathogen attenuation in such systems through production of hydroxyl radical ((•)OH). This study focuses on the efficacy of (•)OH generated during nitrate photolysis in promoting E. coli die-off as a function of extracellular polymeric substances (EPS) coverage. EPS levels of four E. coli isolates were systematically altered through a sonication extraction method and photochemical batch experiments with a solar simulator examined isolate viability loss as a function of time in nitrate solutions. E. coli viability loss over time exhibited two regimes: an initial induction time, t(s), with little decay was followed by rapid exponential decay characterized by a first-order disinfection rate constant, k. Increasing steady-state (•)OH concentrations enhanced E. coli viability loss, increasing values of k and decreasing t(s) values, both of which were quantified with a multitarget bacterial disinfection model. Notably, at a given steady-state (•)OH concentration, values of t(s) and k were independent of EPS levels, nor did they vary among the different E. coli strains considered. Results herein show that while (•)OH generated via nitrate photolysis enhances rates of disinfection in surface water, the mechanism by which (•)OH kills E. coli is relatively insensitive to common bacterial variables. PMID:22082030

  14. Metal-centered polymers: Using controlled polymerization methodologies for the generation of responsive materials

    NASA Astrophysics Data System (ADS)

    Johnson, Robert Matthew

    Controlled polymerization methods were used to prepare highly modular polymeric metal complexes via convergent and divergent strategies. In these materials, the metal center provides a versatile hub for preparing diverse architectures through coordinative bonds. Moreover, the metal complex introduces various properties to the polymer such as luminescence, magnetism, or electroactivity. Suitably functionalized metal complexes have been used for the atom transfer radical polymerization of acrylate and methacrylate monomers by metalloinitiation to generate luminescent biocompatible materials through a divergent synthesis. By cleaving the tert-butyl groups from poly(tert -butyl acrylate), water soluble [Ru(bpyPAA2)3] 2+ has been prepared as well as the amphiphilic star block copolymer [Ru{bpy(PLA-PAA)2}3]2+ (PLA = poly(lactic acid), PAA = poly(acrylic acid) Bipyridine-centered polymeric macroligands may be chelated to a variety of metal salts. The polymer size greatly influences the formation of [Fe(bpy) 3]2+ centered polymers. As the molecular weight increases (> ˜25 kDa) tris complex formation decreases. Tris(bpy) synthesis is also impacted by chemical composition. BpyPtBA2 (PtBA = poly(tert-butyl acrylate) generates an iron mono(bpy) complex before giving rise to the bis(bpy) iron complex; no tris complex is observed. In contrast, the combination of bpyPEG2 (3 equiv) (PEG = (poly(ethylene glycol)) results in the formation of some iron tris(bpy) compound; however, complete tris(bpy) product formation is suppressed, presumably because of the chelating ability of the PEG chains. These examples contrast with other polymeric macroligands such as bpyPS2, bpyPMMA2, bpyPCL2 and bpyPLA 2 (PS = polystyrene; PMMA = poly(methyl methacrylate); PCL = poly(epsilon-caprolactone); PLA = poly(DL-lactic acid)) for which chelation reactions are facile for low molecular weight macroligands (<15 kDa), with chelation efficiencies (defined as (epsilonPMC/epsilonbpy) x 100%) only declining

  15. Controlling internal pore sizes in bicontinuous polymeric nanospheres.

    PubMed

    McKenzie, Beulah E; Friedrich, Heiner; Wirix, Maarten J M; de Visser, Joël F; Monaghan, Olivia R; Bomans, Paul H H; Nudelman, Fabio; Holder, Simon J; Sommerdijk, Nico A J M

    2015-02-16

    Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17 kDa and hydrophilic weight fractions of ≤0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460 nm. Significantly, altering the block copolymer hydrophilic-hydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19 nm. PMID:25640026

  16. Controlling Internal Pore Sizes in Bicontinuous Polymeric Nanospheres**

    PubMed Central

    McKenzie, Beulah E; Friedrich, Heiner; Wirix, Maarten J M; de Visser, Joël F; Monaghan, Olivia R; Bomans, Paul H H; Nudelman, Fabio; Holder, Simon J; Sommerdijk, Nico A J M

    2015-01-01

    Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17 kDa and hydrophilic weight fractions of ≤0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460 nm. Significantly, altering the block copolymer hydrophilic–hydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19 nm. PMID:25640026

  17. Polymer-based monolithic columns in capillary format tailored by using controlled in situ polymerization.

    PubMed

    Aoki, Hiroshi; Tanaka, Nobuo; Kubo, Takuya; Hosoya, Ken

    2009-02-01

    This review introduces to the readers our new perspectives of polymer-based monolithic column with a high performance for small solutes such as drug candidates, illustrating the fabrication of LC columns in capillary. First, we briefly reviewed the status quo of polymer-based monolithic columns, comparing with silica monoliths. The miniaturization of LC system with higher throughput (shorter analytical time) was stressed conceptually, along with a fine permeable bicontinuous monolithic structure with submicron domain size (skeletal thickness + pore size) for higher performance. Second, from these perspectives, our column preparation was described, while our specially designed porogenic solvents were introduced as a controller of the monolithic morphology via reaction-induced phase separation. Specifically, monolithic columns were exemplified in two polymer formats, that is, one monolith prepared by free radical polymerization of glycerin 1,3-dimethacrylate, GDMA, and the other prepared by stepwise polymerization of newly introduced multifunctional epoxy and diamino monomers. Both monolithic columns in capillary format demonstrated a fine bicontinuous structure, affording a good compatibility of the efficiency (H) and permeability (D). Especially, the epoxy-based column showed an excellent separation impedance, E (=H(2)/D). Our micro-HPLC data were discussed along with a prototyped wired chip device. PMID:19142909

  18. Controlled RAFT Polymerization of 2-Vinyl-4,4-Dimethylazlactone (VDMA): A Facile Route to Bio-Inspired Polymer Surfaces

    SciTech Connect

    Lokitz, Bradley S; Messman, Jamie M; Hinestrosa Salazar, Juan Pablo; Alonzo Calderon, Jose E; Verduzco, Rafael; Brown, Rebecca H; Osa, Masashi; Ankner, John Francis; Kilbey, II, S Michael

    2009-01-01

    We report the controlled radical polymerization of 2-vinyl-4,4-dimethyl azlactone (VDMA), a 2-alkenyl-2-oxazolin-5-one monomer that contains a polymerizable vinyl moiety as well as a highly reactive, pendant azlactone as well as solution characterizations and surface attachment and functionaliztion. Reversible addition fragmentation chain transfer (RAFT) was used to polymerize of VDMA in benzene at 65 C using either 2-(2-cyanopropyl) dithiobenzoate (CPDB) or 2-dodecylsulfanylthiocarbonyl-sulfanyl-2-methylpropionic acid (DMP) as RAFT chain transfer agents (CTAs). The pseudo first order kinetics and resultant well-defined polymers of low polydispersity indicate that both CTAs afford control over the RAFT polymerization of VDMA. Dynamic and static light scattering and small angle neutron scattering were performed to determine the dn/dc, weight-average molecular weight, radius of gyration, and second virial coefficient of VDMA homopolymers in THF. Additionally, well-defined polymers of VDMA containing carboxyl end groups were covalently attached to epoxy modified silicon wafers via esterification to produce polymeric scaffolds that could be subsequently functionalized for various bio-inspired applications.

  19. Control over Colloidal Particle Morphology by Dispersion Polymerization

    NASA Astrophysics Data System (ADS)

    Peng, B.

    2013-03-01

    The main subject of this thesis is the structure and morphology control of colloidal polymer particles, in particular, poly(methyl methacrylate) (PMMA) particles, by dispersion polymerization in polar solvents. The structure control, ranging from surface morphology and internal structure to shape manipulation of polymer particles, was attempted through copolymerization of monomers with various types of materials, such as cross-linkers, dyes, and colloidal silica spheres or rods. The obtained spherical or non-spherical particles are interesting as model systems as they mimic molecules at colloidal scales. Their phase behavior can be studied in the presence or absence of external fields (like electric and gravity fields). Additionally, they can be used for various applications, such as photonic crystals

  20. ESR studies of semicontinuous emulsion polymerization

    SciTech Connect

    Lau, W.; Westmoreland, D.G.

    1993-12-31

    Electron spin resonance (ESR) is used in the detection and quantification of propagating radicals during a semicontinuous emulsion polymerization. The propagating radical concentration is crucial for the determination of kinetic parameters of the emulsion polymerization process. A flow reactor was built which involves a closed-loop flow system that circulates latex from the polymerization reactor through the ESR cavity for free-radical measurements and back to the reactor. With the continuous measurement of the radical concentrations during a polymerization of methyl methacrylate (MMA), {bar n} (average number of radicals per particle) and k{sub p} (propagating rate constant), are measured throughout the entire polymerization. For the polymerization of the MMA system studied, the authors observed a gradual increased in n and decrease in k{sub p} during the run, suggesting a diffusionally controlled process and that the polymerization is not occurring homogeneously throughout the polymer particles. In the glassy pMMA matrix, radicals can be {open_quotes}trapped{close_quotes} within a minimum volume and remain unterminated.

  1. p-Hydroxyphenyl (H) Units Lower the Degree of Polymerization in Lignin: Chemical Control in Lignin Biosynthesis

    SciTech Connect

    Sangha, A. K.; Parks, J. M.; Davis, M. F.; Smith, J. C.

    2013-01-01

    Lignin, composed predominantly of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) subunits, is a major component of plant cell walls that imparts resistance toward chemical and microbial deconstruction of plant biomass, rendering its conversion inefficient and costly. Previous studies have shown that alterating lignin composition, i.e., the relative abundance of H, G and S subunits, promises more efficient extraction of sugars from plant biomass. Smaller and less branched lignin chains are more easily extracted during pretreatment, making cellulose more readily degradable. Here, using density functional theory calculations, we show that the incorporation of H subunits into lignin via b-b and b-5 interunit linkages reduces the degree of polymerization in lignin. Frontier molecular orbital analyses of lignin dimers and trimers show that H as a terminal subunit on a growing lignin polymer linked via b-b and b-5 linkage cannot undergo radical formation, preventing further chain growth by endwise polymerization resulting in lignin polymers with lower degree of polymerization. These results indicate that, for endwise polymerization in lignin synthesis, there exists a chemical control that may lay a significant role in determining the structure of lignin.

  2. Morphology Control of Multicomponent Polymeric Surfactants Using Pressure

    NASA Astrophysics Data System (ADS)

    Cho, Junhan

    The development of nanoscale morphologies for a molten polymeric surfactant under pressure is investigated by using a recently formulated self-consistent field theory. A linear ABC block copolymer is taken as our model system that allows a disparity in the propensities for curved interfaces and pressure responses of ij-pairs. The interplay of those features lead the copolymer to new morphologies at a moderate segregation level and at ambient condition such as networks and pillars of 2-dimensional array. It is shown that pressure is an effective means of morphology control and identification for those new structures. The role of volume fluctuations in the development of those structures is discussed. J.C. acknowledges the support from Center for Photofunctional Energy Materials through Gyeonggi Regional Research Program.

  3. Photoacid-mediated ring opening polymerization driven by visible light.

    PubMed

    Fu, Changkui; Xu, Jiangtao; Boyer, Cyrille

    2016-06-01

    A novel methodology of visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid was reported for the first time. In combination with a photoinduced radical polymerization technique, a dual wavelength light controlled orthogonal polymerization system was investigated to switch the polymerization between two different monomers and for the preparation of block and graft copolymers in one pot. PMID:27167862

  4. Spatial control of actin polymerization during neutrophil chemotaxis

    PubMed Central

    Weiner, Orion D.; Servant, Guy; Welch, Matthew D.; Mitchison, Timothy J.; Sedat, John W.; Bourne, Henry R.

    2010-01-01

    Neutrophils respond to chemotactic stimuli by increasing the nucleation and polymerization of actin filaments, but the location and regulation of these processes are not well understood. Here, using a permeabilized-cell assay, we show that chemotactic stimuli cause neutrophils to organize many discrete sites of actin polymerization, the distribution of which is biased by external chemotactic gradients. Furthermore, the Arp2/3 complex, which can nucleate actin polymerization, dynamically redistributes to the region of living neutrophils that receives maximal chemotactic stimulation, and the least-extractable pool of the Arp2/3 complex co-localizes with sites of actin polymerization. Our observations indicate that chemoattractant-stimulated neutrophils may establish discrete foci of actin polymerization that are similar to those generated at the posterior surface of the intracellular bacterium Listeria monocytogenes. We propose that asymmetrical establishment and/or maintenance of sites of actin polymerization produces directional migration of neutrophils in response to chemotactic gradients. PMID:10559877

  5. Etching radical controlled gas chopped deep reactive ion etching

    DOEpatents

    Olynick, Deidre; Rangelow, Ivo; Chao, Weilun

    2013-10-01

    A method for silicon micromachining techniques based on high aspect ratio reactive ion etching with gas chopping has been developed capable of producing essentially scallop-free, smooth, sidewall surfaces. The method uses precisely controlled, alternated (or chopped) gas flow of the etching and deposition gas precursors to produce a controllable sidewall passivation capable of high anisotropy. The dynamic control of sidewall passivation is achieved by carefully controlling fluorine radical presence with moderator gasses, such as CH.sub.4 and controlling the passivation rate and stoichiometry using a CF.sub.2 source. In this manner, sidewall polymer deposition thicknesses are very well controlled, reducing sidewall ripples to very small levels. By combining inductively coupled plasmas with controlled fluorocarbon chemistry, good control of vertical structures with very low sidewall roughness may be produced. Results show silicon features with an aspect ratio of 20:1 for 10 nm features with applicability to nano-applications in the sub-50 nm regime. By comparison, previous traditional gas chopping techniques have produced rippled or scalloped sidewalls in a range of 50 to 100 nm roughness.

  6. Adhesion controls bacterial actin polymerization-based movement.

    PubMed

    Soo, Frederick S; Theriot, Julie A

    2005-11-01

    As part of its infectious life cycle, the bacterial pathogen Listeria monocytogenes propels itself through the host-cell cytoplasm by triggering the polymerization of host-cell actin near the bacterial surface, harnessing the activity of several cytoskeletal proteins used during actin-based cell crawling. To distinguish among several classes of biophysical models of actin-based bacterial movement, we used a high-throughput tracking technique to record the movement of many individual bacteria during temperature shifts. The speed of each bacterium varied strongly with temperature, closely following the Arrhenius rate law. Among bacteria, the prefactor A of the Arrhenius dependence unexpectedly varied exponentially with apparent activation energy, E(a), over a wide range (8-21 kcal/mol), reminiscent of the "rate compensation effect" of classical catalytic reactions. Average E(a) were increased for mutant bacteria deficient in binding Ena/VASP proteins and bacteria moving in diluted extract. These two effects were additive. The observed temperature and rate compensation effects are consistent with a class of simple kinetic models in which the bacterium advances through the thermally driven, cooperative breakage of groups of adhesive bonds on its surface. The estimated number of coupled adhesive bonds N on the bacterial surface varies between 10 and 40 bonds. In contrast to other models, this model correctly predicts an experimentally observed negative correlation between bacterial speed and actin gel density. The idea that speed depends on adhesion, rather than polymerization, suggests several alternative mechanisms by which known cytoskeletal regulatory proteins could control cellular movement. PMID:16251274

  7. Photochemical Control of DNA Structure via Radical Disproportionation

    PubMed Central

    Pedro, Joanna Maria N. San; Greenberg, Marc M.

    2013-01-01

    Photolysis of an aryl sulfide containing 5,6-dihydropyrimidine (1) at 350 nm produces high yields of thymidine and products resulting from trapping of 5,6-dihydrothymidin-5-yl radical by O2 or thiols. Thymidine is believed to result from disproportionation of the radical pair originally generated from C-S bond homolysis in 1 on the microsecond timescale, which is significantly shorter than other photochemical transformations of modified nucleotides into their native forms. Duplex DNA containing 1 is destabilized, presumably due to disruption of π-stacking. Incorporation of 1 within the binding site of the restriction endonuclease EcoRV, provides a photochemical switch for turning on the enzyme's activity. In contrast, 1 is a substrate for endonuclease VIII and serves as a photochemical off switch for this base excision repair enzyme. Modification 1 also modulates the activity of the 10–23 DNAzyme despite its incorporation into a non-duplex region. Overall, dihydropyrimidine 1 shows promise as a tool that provides spatiotemporal control over DNA structure on the miscrosecond tiimescale. PMID:23940105

  8. Use of a Reliable Homemade Dilatometer To Study the Kinetics of the Radical Chain Polymerization of PMMA: An Undergraduate Polymer Chemistry Laboratory Kinetics Experiment

    NASA Astrophysics Data System (ADS)

    Mendicuti, Francisco; Martín, Olga; Tarazona, Maria Pilar

    1998-11-01

    In this laboratory experiment, a simple, reliable homemade dilatometer was used to study the kinetics of the radical chain polymerization of PMMA. The reaction was carried out in toluene with benzoyl peroxide as the initiator at a temperature of 80 °C. Each student studied the kinetics at a different initiator concentration constant. Pseudo-first-order plots permit students to obtain kapp and to demonstrate order 1 with respect to the monomer concentration. Finally, a log-log plot of kapp versus the initiator concentration from the data collected by each student demonstrates order 0.5 with respect to the initiator concentration. Results also agree with the rate constants of the process implicated in this type of polymerization.

  9. Stable polymeric carbon radicals. Part 2: Attempts at the preparation of polyradicals of the triphenylmethyl type linked by P-phenylene units

    NASA Technical Reports Server (NTRS)

    Braun, D.; Lehmann, P.

    1985-01-01

    As starting materials for the preparation of polyradicals of triphenylmethyl type linked by p-phenylene units bis(4-iodophenylmethane) and bis(4-iodo-2,5-dimethyl-phenylmethane) were synthesized by a Sandmeyer reaction from the corresponding diamino compounds and subsequently transformed into the corresponding polymeric hydrocarbons 6a and 6b by an Ullmann condensation. In the following step 6a and 6b were brominated at the tert. carbon atom by means of N-bromosuccinimide. The reaction of the resulting poly (4,4'-biphenylylen-alpha-bromobenzylidene)s (7a and 7b) with mercury afforded the corresponding radicals, the ESR spectra of which were recorded. From the methyl substituted polymer 7b poly (2,2'5,5-tetramethyl-4,4'-bi-phenylylen)phenylmethylidyne was formed, whereas the unsubstituted product 7a was transformed into a para-quinoide polymer with radical properties.

  10. Facile synthesis of ZnO-poly(2-hydroxyethyl methacrylate) nanocomposites by surface-initiated ARGET atom transfer radical polymerization.

    PubMed

    Mai, Thanh Binh; Tran, Thi Nga; Bach, Long Giang; Kim, Dong Woo; Park, Jong Myung; Lim, Kwon Taek

    2014-11-01

    The covalent attachment of poly(2-hydroxyethyl methacrylate) on ZnO nanoparticles (NPs) has been achieved by ARGET ATRP. The polymer chains were grown from the surface of ATRP-initiator modified ZnO NPs with a copper (II) catalyst under activation of zerovalent copper as a reducing agent. FT-IR, FE-SEM, TEM and TGA were employed for the characterization of the nanocomposites. GPC was used to determine the molecular weight and PDI of the cleaved polymer. The covalent attachment of polymer chains onto the surface of ZnO NPs was sufficiently confirmed by FT-IR. In addition, the formation of the polymer encapsulating ZnO cores was demonstrated from TEM and SEM images. It was found that the growing of polymer brushes from the ZnO surface could be induced even though the catalyst amount was reduced to 10 ppm without loss of inherent control manner. This report contributed to demonstrate the versatility and feasibility of ATRP-based surface-initiated polymerization for the preparation of inorganic/polymer nanocomposites. PMID:25958609

  11. Role of Radical Species in Salicylaldiminato Ni(II) Mediated Polymer Chain Growth: A Case Study for the Migratory Insertion Polymerization of Ethylene in the Presence of Methyl Methacrylate.

    PubMed

    Ölscher, Franz; Göttker-Schnetmann, Inigo; Monteil, Vincent; Mecking, Stefan

    2015-11-25

    To date, an inconclusive and partially contradictive picture exists on the behavior of neutral Ni(II) insertion polymerization catalysts toward methyl methacrylate (MMA). We shed light on this issue by a combination of comprehensive mechanistic NMR and EPR studies, isolation of a key Ni(I) intermediate, and pressure reactor studies with ethylene and MMA, followed by detailed polymer analysis. An interlocking mechanistic picture of an insertion and a free radical polymerization is revealed. Both polymerizations run simultaneously (25 bar ethylene, neat MMA, 70 °C); however, the chain growth cycles are independent of each other, and therefore exclusively a physical mixture of homo-PE and homo-PMMA is obtained. A Ni-C bond cleavage was excluded as a free radical source. Rather a homolytic P-C bond cleavage in the labile aryl phosphine ligand and the reaction of low-valent Ni(0/I) species with specific iodo substituted N^O (Ar-I) ligands were shown to initiate radical MMA polymerizations. Several reductive elimination decomposition pathways of catalyst precursor or active intermediates were shown to form low-valent Ni species. One of those pathways is a bimolecular reductive coupling via intermediate (N^O)Ni(I) formation. These intermediate Ni(I) species can be prevented from ultimate decomposition by capturing with organic radical sources, forming insertion polymerization active [(N^O)Ni(II)-R] species and prolonging the ethylene polymerization activity. PMID:26571229

  12. Polymeric barrier membranes for device packaging, diffusive control and biocompatibility

    NASA Astrophysics Data System (ADS)

    Wasikiewicz, J. M.; Roohpour, N.; Paul, D.; Grahn, M.; Ateh, D.; Rehman, I.; Vadgama, P.

    2008-11-01

    Current state-of-the-art implantable micron feature electronic devices are capable of monitoring and stimulating functions in vivo. Within an EU Framework VI project a further step was taken in developing key microsystem technologies and communication methods that could bring intelligence directly to the human interface, in the form of reactive medical implants and ambulatory measurement systems. Information from these devices is planned to be transmitted out into the wider environment for remote processing. However, the packaging of such state-of-the-art devices to enhance tissue biocompatibility, and to protect conducting elements from in vivo corrosion during extended use, along with protecting the body from toxins leaching from implant components, remains a concern. Candidate polymeric barriers as hydration resistant and solute impermeable interfaces to mitigate such major problems of chronic implantation were investigated. Materials studied included silicone rubber, PVC, polyurethane, and diamond-like carbon (DLC). Polymer permeability to water solutes was marginally improved through incorporation of lipid into these structures. Surface biocompatibility was assessed on the basis of protein film deposition in vitro and by cell viability studies in tissue culture. Short-term toxicity was not observed for any of the tested materials, though there were substantial differences in hydration. Additionally, polypyrrole over active electrodes shows feasibility for controlled tissue interfacing whilst retaining electrical conductivity.

  13. Polymeric surfaces exhibiting photocatalytic activity and controlled anisotropic wettability

    NASA Astrophysics Data System (ADS)

    Anastasiadis, Spiros H.; Frysali, Melani A.; Papoutsakis, Lampros; Kenanakis, George; Stratakis, Emmanuel; Vamvakaki, Maria; Mountrichas, Grigoris; Pispas, Stergios

    2015-03-01

    In this work we focus on surfaces, which exhibit controlled, switchable wettability in response to one or more external stimuli as well as photocatalytic activity. For this we are inspired from nature to produce surfaces with a dual-scale hierarchical roughness and combine them with the appropriate inorganic and/or polymer coating. The combination of the hierarchical surface with a ZnO coating and a pH- or temperature-responsive polymer results in efficient photo-active properties as well as reversible superhydrophobic / superhydrophilic surfaces. Furthermore, we fabricate surfaces with unidirectional wettability variation. Overall, such complex surfaces require advanced design, combining hierarchically structured surfaces with suitable polymeric materials. Acknowledgment: This research was partially supported by the European Union (European Social Fund, ESF) and Greek national funds through the ``ARISTEIA II'' Action (SMART-SURF) of the Operational Programme ``Education and Lifelong Learning,'' NSRF 2007-2013, via the General Secretariat for Research & Technology, Ministry of Education and Religious Affairs, Greece.

  14. Dynamic Polymeric Microtubes for the Remote-Controlled Capture, Guidance, and Release of Sperm Cells.

    PubMed

    Magdanz, Veronika; Guix, Maria; Hebenstreit, Franziska; Schmidt, Oliver G

    2016-06-01

    Remote-controlled release of single sperm cells is demonstrated by the use of polymeric microtubes that unfold upon temperature increase to 38 °C. Thermoresponsive, ferromagnetic multilayers are tailored to catch sperm cells and remotely control them by external magnetic fields. These polymeric spermbots are propelled by the sperm flagella. When the temperature is increased, the tubes unfold and the cell is set free. PMID:27003908

  15. A General Approach to Sequence-Controlled Polymers Using Macrocyclic Ring Opening Metathesis Polymerization

    PubMed Central

    2015-01-01

    A new and general strategy for the synthesis of sequence-defined polymers is described that employs relay metathesis to promote the ring opening polymerization of unstrained macrocyclic structures. Central to this approach is the development of a small molecule “polymerization trigger” which when coupled with a diverse range of sequence-defined units allows for the controlled, directional synthesis of sequence controlled polymers. PMID:26053158

  16. Fabrication of contrast agents for magnetic resonance imaging from polymer-brush-afforded iron oxide magnetic nanoparticles prepared by surface-initiated living radical polymerization.

    PubMed

    Ohno, Kohji; Mori, Chizuru; Akashi, Tatsuki; Yoshida, Shinichi; Tago, Yoshiyuki; Tsujii, Yoshinobu; Tabata, Yasuhiko

    2013-10-14

    The aim of this study is to fabricate a contrast agent for magnetic resonance imaging (MRI) by using hybrid particles composed of a core of iron oxide magnetite (Fe3O4) nanoparticles and a shell of hydrophilic polymer brush synthesized by surface-initiated (SI) living radical polymerization. To achieve this, Fe3O4 nanoparticles were surface-modified with initiating groups for atom transfer radical polymerization (ATRP) via a ligand-exchange reaction in the presence of a triethoxysilane derivative having an ATRP initiation site. The ATRP-initiator-functionalized Fe3O4 nanoparticles were used for performing the SI-ATRP of methyl methacrylate to demonstrate the ability of the synthesized nanoparticles to produce well-defined polymer brushes on their surfaces. The polymerization proceeded in a living fashion so as to produce graft polymers with targeted molecular weights and narrow molecular weight distribution. The average graft density was estimated to be as high as 0.7 chains/nm(2), which indicates the formation of so-called concentrated polymer brushes on the Fe3O4 nanoparticles. Dynamic light scattering and transmission electron microscope observations of the hybrid nanoparticles revealed their uniformity and dispersibility in solvents to be excellent. A similar polymerization process was conducted using a hydrophilic monomer, poly(ethylene glycol) methyl ether methacrylate (PEGMA), to prepare Fe3O4 nanoparticles grafted with poly(PEGMA) brushes. The resultant hybrid nanoparticles showed excellent dispersibility in aqueous media including physiological conditions without causing any aggregations. The blood clearance and biodistribution of the hybrid particles were investigated by intravenously injecting particles labeled with a radio isotope, (125)I, into mice. It was found that some hybrid particles exhibited an excellently prolonged circulation lifetime in the blood with a half-life of about 24 h. When such hybrid particles were injected intravenously into a

  17. Quality control of residual solvent content in polymeric microparticles.

    PubMed

    Dixit, Kalpana; Athawale, Rajani B; Singh, Sarabjit

    2015-01-01

    Organic solvents are the innate part of pharmaceutical industry, playing vital role in the bulk drug substance as well as finished product manufacturing. Even though they are used for various crucial purposes, they still lack therapeutic beneficial effect and can be toxic if present in unacceptable limits in final product. Hence, their concentration must be regulated in the final pharmaceutical formulation. With the major development in the market of polymeric microparticles in past few decades, drug product manufacturers are paying more attention towards the development of new techniques for reducing residual solvent content of microparticles. This article sheds light on the importance of removal of organic volatile impurities from the formulation and its regulatory aspects. It also highlights how residual solvent affects various physicochemical characteristics of polymeric microparticles and suggests certain solutions as per the current state of art for limiting organic solvent content in the final product. PMID:25560934

  18. pH- and Temperature-Responsive P(DMAEMA-GMA)-Alginate Semi-IPN Hydrogels Formed by Radical and Ring-Opening Polymerization for Aminophylline Release.

    PubMed

    Gao, Chunmei; Liu, Mingzhu; Chen, Jun; Chen, Chen

    2012-01-01

    A novel poly((2-dimethylamino) ethyl methacrylate-glycidyl methacrylate)-alginate (P(DMAEMA-GMA)alginate) semi-IPN hydrogel was synthesized via radical polymerization of the double bonds and ring-opening of the epoxy groups without using catalyst and cross-linker. (1)H-NMR, FT-IR and DSC data were consistent with the expected structures for the hydrogels. The interior morphology of the hydrogels was also investigated by SEM. The swelling ratio and compressive strength of the hydrogels were measured. The semi-IPN hydrogel had pH and temperature sensitivity, and pH-sensitive points of all hydrogels were found to be at pH 5.0. The release behavior of the model drug, aminophylline, was found to be dependent on the hydrogel composition and environment pH, which manifests that these materials have potential applications as intelligent drug carriers. PMID:21513583

  19. Preparation of Mg(OH)2 hybrid pigment by direct precipitation and graft onto cellulose fiber via surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Zhang, Yue; Lv, Lihua; Cui, Yongzhu; Wei, Chunyan; Pang, Guibing

    2016-02-01

    Mg(OH)2 flame retardant hybrid pigment is synthesized through simultaneous solution precipitation and adsorption of anionic dyes (C.I. Acid Red 6). The Mg(OH)2 hybrid pigment bearing vinyl groups after surface silane modification is immobilized onto the surface of bromo end-functional cellulose fiber by atom transfer radical polymerization (ATRP). The morphology and structure of Mg(OH)2 pigments and cellulose fibers grafted with modified pigments are characterized. The thermal properties, flammability and color fastness of cellulose fibers grafted with modified pigments are measured. The results reveal that anionic dye molecules are adsorbed onto Mg(OH)2 crystals and affect the formation of lamella-like Mg(OH)2 crystals. The cellulose fiber grafted with modified Mg(OH)2 hybrid pigment absorbs about four times heat more than original cellulose fiber with about 4% immobilization ratio of pigment, which shortens nearly half of afterflame time and afterglow time.

  20. Fabrication of an ionic liquid-based macroporous polymer monolithic column via atom transfer radical polymerization for the separation of small molecules.

    PubMed

    Zhang, Hang; Bai, Ligai; Wei, Zhen; Liu, Sha; Liu, Haiyan; Yan, Hongyuan

    2016-03-01

    A polymer monolithic column was prepared in a stainless steel column (50×4.6mm i.d.) via atom transfer radical polymerization technique using triallyl isocyanurate and ionic liquid (1-allyl-3-methylimidazolium chloride) as co-monomers, ethylene dimethacrylate as cross linking agent, polyethylene glycol 200, 1,4-butanediol, and N, N- dimethylformamide as porogen system, CCl4 as initiator, and FeCl2 as catalyst. The optimized polymer columns were characterized by scanning electron microscope, nitrogen adsorption-desorption instrument, mercury intrusion porosimetry, infrared spectrometer, and thermogravimetric analysis technique. Respectively, all of these factors above could illustrate that the optimized columns had relative uniform macroporous structure and high thermal stability. A series of basic and acidic small molecules, isomers, and homologues were used to evaluate the performance of these monoliths and enhanced column efficiency was obtained. PMID:26717814

  1. Cu(II)-mediated atom transfer radical polymerization of methyl methacrylate via a strategy of thermo-regulated phase-separable catalysis in a liquid/liquid biphasic system: homogeneous catalysis, facile heterogeneous separation, and recycling.

    PubMed

    Pan, Jinlong; Zhang, Bingjie; Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

    2014-09-01

    A strategy of thermo-regulated phase-separable catalysis (TPSC) is applied to the Cu(II)-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in a p-xylene/PEG-200 biphasic system. Initiators for continuous activator regeneration ATRP (ICAR ATRP) are used to establish the TPSC-based ICAR ATRP system using water-soluble TPMA as a ligand, EBPA as an initiator, CuBr2 as a catalyst, and AIBN as a reducing agent. By heating to 70 °C, unlimited miscibility of both solvents is achieved and the polymerization can be carried out under homogeneous conditions; then on cooling to 25 °C, the mixture separates into two phases again. As a result, the catalyst complex remains in the PEG-200 phase while the obtained polymers stay in the p-xylene phase. The catalyst can therefore be removed from the resultant polymers by easily separating the two different layers and can be reused again. It is important that well-defined PMMA with a controlled molecular weight and narrow molecular weight distribution could be obtained using this TPSC-based ICAR ATRP system. PMID:25155655

  2. Well-defined azlactone-functionalized (co)polymers on a solid support: synthesis via supported living radical polymerization and application as nucleophile scavengers.

    PubMed

    Fournier, David; Pascual, Sagrario; Montembault, Véronique; Haddleton, David M; Fontaine, Laurent

    2006-01-01

    Wang resin has been converted to a supported initiator for transition metal-mediated living radical polymerization often called atom-transfer radical polymerization (ATRP) of 2-vinyl-4,4-dimethyl-5-oxazolone (VDM) and styrene (S). Several "Rasta" resins with well-defined macromolecular architectures, including homopolymers PVDM, PS, statistical P(S-stat-VDM), block P(S-b-VDM), and P[S-b-(S-stat-VDM)] copolymers, have been elaborated. For the homopolymerization of VDM and S, a sacrificial initiator, benzyl 2-bromoisobutyrate (BBI), has been introduced to monitor the evolution of molar masses and polydispersity indexes (PDIs) of PS and PVDM onto the Wang resin support without cleavage. After 6 h, 86.7% conversion of VDM is reached, with the isolated PVDM chains having a molar mass of 18 000 g mol(-1) and a PDI value of 1.22. Block copolymers have been synthesized in two steps, involving the synthesis of the PS block isolated at low conversions (<15%) to maintain the bromine end-chain functionality and the subsequent synthesis of the second PVDM or P(S-stat-VDM) block. Polydispersity indexes of the cleaved (co)polymers were low (PDI = 1.11-1.44), and high azlactone loadings have been reached (loading = 6.0 mmol g(-1)). Such azlactone-functionalized Wang resins have shown high efficiency during the scavenging process of benzylamine as monitored by HPLC. Moreover, grafted statistical copolymers have shown the best behavior for removing benzylamine because of an improvement of the accessibility of azlactone rings by the dilution with styrene units. PMID:16827564

  3. Cysteine Methylation Controls Radical Generation in the Cfr Radical AdoMet rRNA Methyltransferase

    PubMed Central

    Challand, Martin R.; Salvadori, Enrico; Driesener, Rebecca C.; Kay, Christopher W. M.; Roach, Peter L.; Spencer, James

    2013-01-01

    The ‘radical S-adenosyl-L-methionine (AdoMet)’ enzyme Cfr methylates adenosine 2503 of the 23S rRNA in the peptidyltransferase centre (P-site) of the bacterial ribosome. This modification protects host bacteria, notably methicillin-resistant Staphylococcus aureus (MRSA), from numerous antibiotics, including agents (e.g. linezolid, retapamulin) that were developed to treat such organisms. Cfr contains a single [4Fe-4S] cluster that binds two separate molecules of AdoMet during the reaction cycle. These are used sequentially to first methylate a cysteine residue, Cys338; and subsequently generate an oxidative radical intermediate that facilitates methyl transfer to the unreactive C8 (and/or C2) carbon centres of adenosine 2503. How the Cfr active site, with its single [4Fe-4S] cluster, catalyses these two distinct activities that each utilise AdoMet as a substrate remains to be established. Here, we use absorbance and electron paramagnetic resonance (EPR) spectroscopy to investigate the interactions of AdoMet with the [4Fe-4S] clusters of wild-type Cfr and a Cys338 Ala mutant, which is unable to accept a methyl group. Cfr binds AdoMet with high (∼ 10 µM) affinity notwithstanding the absence of the RNA cosubstrate. In wild-type Cfr, where Cys338 is methylated, AdoMet binding leads to rapid oxidation of the [4Fe-4S] cluster and production of 5'-deoxyadenosine (DOA). In contrast, while Cys338 Ala Cfr binds AdoMet with equivalent affinity, oxidation of the [4Fe-4S] cluster is not observed. Our results indicate that the presence of a methyl group on Cfr Cys338 is a key determinant of the activity of the enzyme towards AdoMet, thus enabling a single active site to support two distinct modes of AdoMet cleavage. PMID:23861844

  4. Improving the drug delivery characteristics of graphene oxide based polymer nanocomposites through the "one-pot" synthetic approach of single-electron-transfer living radical polymerization

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Liu, Meiying; Tian, Jianwen; Deng, Fengjie; Wang, Ke; Xu, Dazhuang; Liu, Liangji; Zhang, Xiaoyong; Wei, Yen

    2016-08-01

    Graphene oxide (GO) based polymer nanocomposites have attracted extensive research interest recently for their outstanding physicochemical properties and potential applications. However, surface modification of GO with synthetic polymers has demonstrated to be trouble for most polymerization procedures are occurred under non-aqueous solution, which will in turn lead to the restacking of GO. In this work, a facile and efficient "one-pot" strategy has been developed for surface modification of GO with synthetic polymers through single-electron-transfer living radical polymerization (SET-LRP). The GO based polymer nanocomposites were obtained via SET-LRP in aqueous solution using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the monomer and 11-bromoundecanoic acid as the initiator, which could be effectively adsorbed on GO through hydrophobic interaction. The successful preparation of GO based polymer nanocomposites was confirmed by a series of characterization techniques such as 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The resultant products exhibit high water disperisibility, excellent biocompatibility and high efficient drug loading capability, making these PEGylated GO nanocomposites promising candidates for biomedical applications.

  5. Preparation of high-capacity, weak anion-exchange membranes by surface-initiated atom transfer radical polymerization of poly(glycidyl methacrylate) and subsequent derivatization with diethylamine

    NASA Astrophysics Data System (ADS)

    Qian, Xiaolei; Fan, Hua; Wang, Chaozhan; Wei, Yinmao

    2013-04-01

    Ion-exchange membrane is of importance for the development of membrane chromatography. In this work, a high-capacity anion-exchange membrane was prepared by grafting of glycidyl methacrylate (GMA) onto the surface of regenerated cellulose (RC) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequent derivatization with diethylamine. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize changes in the chemical functionality, surface topography and pore morphology of the modified membranes. The static capacity of the prepared anion-exchange membrane was evaluated with bovine serum albumin (BSA) as a model protein. The results indicated that the anion-exchange membrane which could reach a maximum capacity of 96 mg/mL for static adsorption possesses a higher adsorption capacity, and the adsorption capacity increases with the polymerization time. The effect of pH and salt concentration confirmed that the adsorption of BSA followed ion-exchange mechanism. The established method would have potential application in the preparation of anion-exchange membrane.

  6. Preparation of (Ba,Sr)TiO3@polystrene core-shell nanoparticles by solvent-free surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Xiaowei, Yang; Yanwei, Zeng; Tongxiang, Cai; Zhenxing, Hu

    2012-07-01

    The polystyrene shells have been successfully grown on the barium strontium titanate (BST) nanocrystals, which were synthesized by microwave-activated glycothermal method, via a solvent-free surface-initiated atom transfer radical polymerization (SI-ATRP) after the 2-bromo-2-methylpropionic acid molecules (Br-MPA) were anchored at the surface of BST nanocrystals through ligand exchange with hydroxyl groups on their surfaces. These surface modified BST nanocrystals can then be perfectly dispersed in styrene monomer and act as macroinitiators for ATRP to yield BST@PS core-shell structured nanoparticles, which endow the BST nanocrystals with exceptionally good dispersibility and stability in hydrophobic solvents. The BST@PS core-shell structures were characterized by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), differential scanning calorimetry (DSC) and gel permeation chromatography were also employed to probe the Br-MPA and PS on the BST nanocrystals. It has been shown that after the BST nanocrystals are surface-modified with Br-MPA, the polymerization of styrene can steadily occur at the surface of BST nanocrystals to form a uniform polystyrene shell and its thickness can reach ∼10 nm when the polymerization reaction is extended to 36 h, while no changes are found to take place with the BST nanocrystals. Compared with typical high molecular weight PS (Mn = 6700), the as-obtained PS possess a relatively low molecular weight (Mn = 5473) and a lower glass transition temperature (Tg ∼ 93 °C). The research results demonstrate a viable strategy for the preparation of polymer-coated functional metal oxides nanocrystals, potentially useful in biological and nanoelectronic applications.

  7. Glucose-sensitive polymeric matrices for controlled drug delivery.

    PubMed

    Goldraich, M; Kost, J

    1993-01-01

    Hydrogel matrices were prepared by chemical polymerization of solutions containing 2-hydroxyethyl methacrylate, N,N-dimethyl-aminoethyl methacrylate, tetraethylene glycol dimethacrylate, ethylene glycol and water solutions containing glucose oxidase, bacitracin or insulin. The hydrogels displayed faster and higher swelling and release rates at lower pH or at higher glucose concentrations. Swelling and release kinetics were also responsive to step changes in glucose concentration in the physiological range. The kinetics of the soluble and immobilized enzyme followed Michaelis Menten's kinetics. In the soluble state the enzyme was more active than the immobilized one due to mass transfer limitations, which may be overcome by preparation of microbead configuration. PMID:10146247

  8. Light activation of transcription: photocaging of nucleotides for control over RNA polymerization

    PubMed Central

    Pinheiro, André Vidal; Baptista, Pedro; Lima, João Carlos

    2008-01-01

    We describe the use of ATP caged with [7-(diethylamino)coumarin-4-yl]methyl (DEACM) for light-controlled in vitro transcription reactions. Polymerization is blocked when DEACM is bonded to the gamma phosphate group of the ATP molecule. Controlled light irradiation releases ATP and transcription is initiated. In order to provide full control over the process, conditions involved in substrate release, nucleotide availability after release and the effect of the released coumarin in RNA polymerization were assessed in further detail. Together, our data provide the first direct evidence of control over enzymatic polymerization of nucleic acids through light. This approach may provide researchers with a unique tool for the study of biological processes at a molecular level. PMID:18586819

  9. Polymerization of ionized acetylene clusters into covalent bonded ions: evidence for the formation of benzene radical cation.

    PubMed

    Momoh, Paul O; Abrash, Samuel A; Mabrouki, Ridha; El-Shall, M Samy

    2006-09-27

    Since the discovery of acetylene and benzene in protoplanetary nebulae under powerful ultraviolet ionizing radiation, efforts have been made to investigate the polymerization of ionized acetylene. Here we report the efficient formation of benzene ions within gas-phase ionized acetylene clusters (C2H2)n+ with n = 3-60. The results from experiments, which use mass-selected ion mobility techniques, indicate that the (C2H2)3+ ion has unusual stability similar to that of the benzene cation; its primary fragment ions are similar to those reported from the benzene cation, and it has a collision cross section of 47.4 A2 in helium at 300 K, similar to the value of 47.9 A2 reported for the benzene cation. In other words, (C2H2)3+ structurally looks like benzene, it has stability similar to that of benzene, it fragments such as benzene, therefore, it must be benzene! PMID:16984178

  10. Phase separation of lipid microdomains controlled by polymerized lipid bilayer matrices.

    PubMed

    Okazaki, Takashi; Tatsu, Yoshiro; Morigaki, Kenichi

    2010-03-16

    We developed a micropatterned model biological membrane on a solid substrate that can induce phase separation of lipid microdomains in a designed geometry. Micropatterned lipid bilayers were generated by the photolithographic polymerization of a diacetylene phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC). By changing the UV dose for the photopolymerization, we could modulate the coverage of the surface by the polymeric bilayer domains. After removing nonpolymerized DiynePC, natural phospholipid membranes were incorporated into the micropatterned polymeric bilayer matrix by a self-assembly process (vesicle fusion). As we incorporated a ternary lipid mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), sphingomyelin (SM), and cholesterol (Chol) (1:1:1), liquid ordered domains (Lo: rich in SM and Chol) were accumulated in the polymer free regions, whereas liquid disordered domains (Ld: rich in DOPC) preferentially participated into the partially polymeric bilayer regions. It was postulated that Ld domains preferentially came in contact with the polymeric bilayer boundaries because of their lower elastic moduli and a smaller thickness mismatch at the boundary. The effect of polymeric bilayer matrix to hinder the size growth of Lo domains should also be playing an important role. The controlled phase separation should open new possibilities to locally concentrate membrane proteins and other nanometer-sized materials on the substrate by associating them with the lipid microdomains. PMID:20020734

  11. Controllable synthesis of new polymerizable macrosurfactants via CCTP and RAFT techniques and investigation of their performance in emulsion polymerization.

    PubMed

    Chen, Li; Yan, Lili; Li, Qing; Wang, Caifeng; Chen, Su

    2010-02-01

    We reported herein the synthesis of poly(methacrylic acid)-b-poly(butyl acrylate) (PMAA-b-PBA) block copolymers (surfmers) and their performance as novel polymerizable macrosurfactants in emulsion polymerization. The surfmers bearing terminal unsaturated carbon-carbon double bonds were first successfully designed and sythesized via catalytic chain transfer polymerization (CCTP) and radical addition-fragmentation polymerization (RAFT) techniques. The structures of surfmers were characterized by Raman spectra, nuclear magnetic resonance ((1)H NMR), and gel permeation chromatography (GPC). The critical micelle concentration of surfmers was determined. Subsequently, the surfmers were used as emulsifier to prepare polyacrylate latexes (PA-surf). The influence of the surfmer concentration as well as PMAA and PBA chain segment ratios of surfmer on their performance in emulsion polymerization was discussed thoroughly. The particle size, amount of coagulum, and stability against electrolyte solutions of the latexes were evaluated. Also, the relations between monomer conversion in emulsion polymerization, polymerization rate, emulsion particle size, surface tension, and reaction time were investigated, which showed some interesting information for the probable mechanism underlying this emulsion polymerization system. Atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectra (ATR FT-IR) were performed to investigate the surface morphology and component distribution of the latex films. The results show high efficiency of these surfmers in emulsion polymerization, suggesting that the resultant PMAA-b-PBA block copolymers act not only as the emulsifier but also as the stabilizer of monomer droplets as well as the so-called comonomer. PMID:19928970

  12. Chromatographic assessment of two hybrid monoliths prepared via epoxy-amine ring-opening polymerization and methacrylate-based free radical polymerization using methacrylate epoxy cyclosiloxane as functional monomer.

    PubMed

    Wang, Hongwei; Ou, Junjie; Lin, Hui; Liu, Zhongshan; Huang, Guang; Dong, Jing; Zou, Hanfa

    2014-11-01

    Two kinds of hybrid monolithic columns were prepared by using methacrylate epoxy cyclosiloxane (epoxy-MA) as functional monomer, containing three epoxy moieties and one methacrylate group. One column was in situ fabricated by ring-opening polymerization of epoxy-MA and 1,10-diaminodecane (DAD) using a porogenic system consisting of isopropanol (IPA), H2O and ethanol at 65°C for 12h. The other was prepared by free radical polymerization of epoxy-MA and ethylene dimethacrylate (EDMA) using 1-propanol and 1,4-butanediol as the porogenic solvents at 60°C for 12h. Two hybrid monoliths were investigated on the morphology and chromatographic assessment. Although two kinds of monolithic columns were prepared with epoxy-MA, their morphologies looked rather different. It could be found that the epoxy-MA-DAD monolith possessed higher column efficiencies (25,000-34,000plates/m) for the separation of alkylbenzenes than the epoxy-MA-EDMA monolith (12,000-13,000plates/m) in reversed-phase nano-liquid chromatography (nano-LC). Depending on the remaining epoxy or methacrylate groups on the surface of two pristine monoliths, the epoxy-MA-EDMA monolith could be easily modified with 1-octadecylamine (ODA) via ring-opening reaction, while the epoxy-MA-DAD monolith could be modified with stearyl methacrylate (SMA) via free radical reaction. The chromatographic performance for the separation of alkylbenzenes on SMA-modified epoxy-MA-DAD monolith was remarkably improved (42,000-54,000 plates/m) when compared with that on pristine epoxy-MA-DAD monolith, while it was not obviously enhanced on ODA-modified epoxy-MA-EDMA monolith when compared with that on pristine epoxy-MA-EDMA monolith. The enhancement of the column efficiency of epoxy-MA-DAD monolith after modification might be ascribed to the decreased mass-transfer resistence. The two kinds of hybrid monoliths were also applied for separations of six phenols and seven basic compounds in nano-LC. PMID:25311483

  13. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

    DOE PAGESBeta

    Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung; Mehio, Nada; Li, Meijun; Gill, Gary; Tsouris, Costas; Mayes, Richard T.; Saito, Tomonori; Dai, Sheng

    2016-03-11

    The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly-(vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligandsmore » (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42 3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Lastly, adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.« less

  14. Controllable surface morphology and properties via mist polymerization on a plasma-treated polymethyl methacrylate surface.

    PubMed

    Wan, S J; Wang, L; Xu, X J; Zhao, C H; Liu, X D

    2014-02-14

    Surface modification by grafting polymers on solid materials is an important strategy used to improve surface properties. This article reports that under appropriate conditions, very thin layers with desired morphologies may be constructed on a plasma-treated substrate by feeding a small quantity of a monomer with a mist stream carrying droplets produced from monomer solutions. We investigate the effects of process parameters that affect layer morphology, including exposure time to the mist stream, concentration of the monomer solution, and solvent selectivity. For a methyl methacrylate solution in ethanol, nanoparticles are uniformly grown with increasing monomer concentration or exposure time and finally form a porous layer at 3.65 mol L(-1) for 30 min. Decreasing solvent polarity not only affects surface morphology, but also increases hydrophobicity of the resulting surface. With 2,2,3,4,4,4-hexafluorobutyl methacrylate as the monomer, SEM and AFM micrographs indicated that mist polymerization results in numerous microspheres on the activated surface. These experimental results were interpreted by a mechanism in terms of an in situ polymerization accompanied by a phase transformation of the resulting polymer. Specifically, plasma treatment provides highly active cations and radicals to initiate very rapid polymerization, and the resulting polymers are consequently deposited from the liquid onto the surface under phase transition mechanisms. PMID:24835436

  15. Accessing conjugated polymers with precisely controlled heterobisfunctional chain ends via post-polymerization modification of the OTf group and controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization

    SciTech Connect

    Hu, Qiao -Sheng; Hong, Kunlun; Zhang, Hong -Hai

    2015-08-12

    In this study, a general strategy toward the synthesis of well-defined conjugated polymers with controlled heterobisfunctional chain ends via combination of controlled Pd(0)/t-Bu3P Suzuki cross-coupling polymerization with the post-polymerization modification of the triflate (OTf) group was disclosed.

  16. Accessing conjugated polymers with precisely controlled heterobisfunctional chain ends via post-polymerization modification of the OTf group and controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization

    DOE PAGESBeta

    Hu, Qiao -Sheng; Hong, Kunlun; Zhang, Hong -Hai

    2015-08-12

    In this study, a general strategy toward the synthesis of well-defined conjugated polymers with controlled heterobisfunctional chain ends via combination of controlled Pd(0)/t-Bu3P Suzuki cross-coupling polymerization with the post-polymerization modification of the triflate (OTf) group was disclosed.

  17. Drug-Initiated, Controlled Ring-Opening Polymerization for the Synthesis of Polymer-Drug Conjugates

    PubMed Central

    Tong, Rong; Cheng, Jianjun

    2012-01-01

    Paclitaxel, a polyol chemotherapeutic agent, was covalently conjugated through its 2′-OH to polylactide with 100% regioselectivity via controlled polymerization of lactide mediated by paclitaxel/(BDI-II)ZnN(TMS)2 (BDI-II = 2-((2,6-diisopropylphenyl)amino)-4-((2,6-diisopropylphenyl)imino)-2-pentene). The steric bulk of the substituents on the N-aryl groups of the BDI ligand drastically affected the regiochemistry of coordination of the metal catalysts to paclitaxel and the subsequent ring-opening polymerization of lactide. The drug-initiated, controlled polymerization of lactide was extended, again with 100% regioselectivity, to docetaxel, a chemotherapeutic agent that is even more structurally complex than paclitaxel. Regioselective incorporation of paclitaxel (or docetaxel) to other biopolymers (i.e., poly(δ-valerolactone), poly(trimethylene carbonate), and poly(ε-caprolactone)), was also achieved through drug/(BDI-II)ZnN(TMS)2-mediated controlled polymerization. These drug-polylactide conjugates with precisely controlled structures are expected to be excellent building blocks for drug delivery, coating, and controlled-release applications. PMID:23357880

  18. Preparation of methacrylamide-functionalized crosslinked chitosan by free radical polymerization for the removal of lead ions.

    PubMed

    Sutirman, Zetty Azalea; Sanagi, Mohd Marsin; Abd Karim, Khairil Juhanni; Wan Ibrahim, Wan Aini

    2016-10-20

    A new poly(methacrylamide) grafted crosslinked chitosan was prepared for removal of lead, Pb(II) ion from aqueous solution. Crosslinked chitosan, in beads form, was grafted with methacrylamide (MAm) using ammonium persulfate (APS) as free radical initiator. Evidence of grafting was determined by comparing FTIR, TGA, SEM and (13)C NMR analyses of chitosan and graft copolymer. The optimal conditions for grafting reaction were as follow: crosslinked chitosan beads (1g), MAm (17.62×10(-1)M), APS (2.63×10(-1)M), reaction time (3h) and temperature (60°C). The modified chitosan bead was then used in laboratory batch experiments to evaluate the removal of Pb(II) ion from water samples. The Langmuir and Freundlich adsorption models were also applied to describe the equilibrium isotherms. The results revealed that the adsorption of Pb(II) ions onto the beads fitted very well with the Langmuir model with the maximum capacity (qmax) of 250mgg(-1). PMID:27474659

  19. Volume holographic recording in photopolymerizable nanocomposite materials based on radical-mediated thiol-yne step-growth polymerizations

    NASA Astrophysics Data System (ADS)

    Mitsube, Ken; Nishimura, Yuki; Takayama, Shingo; Nagaya, Kohta; Tomita, Yasuo

    2013-05-01

    We propose the use of radical-mediated thiol-yne step-growth photopolymerizations for volume holographic recording in NPC films to overcome the drawback of low crosslinking densities but retain the advantage of low shrinkage in the thiol-ene photopolymerizations. The thiol-yne photopolymerization mechanism is different from the thiol-ene photopolymeriztions in the sense that each alkyne functional group can react consecutively with two thiol functional groups. We show that thiol-yne based NPC films dispersed with silica nanoparticles give the saturated refractive index change as large as 0.008 and the material recording sensitivity as high as 2005 cm/J at a wavelength of 532 nm, larger than the minimum acceptable values of 0.005 and 500 cm/J, respectively, for holographic data storage. We also show that the shrinkage of a recorded hologram can be as low as that of thiol-ene based NPC films and that the thermal stability is improved better. In addition, we demonstrate digital data page recording in thiol-yne based NPC films, showing a low symbol error rate and a high signal-to-noise ratio to be 2.8×10-4 and 8, respectively.

  20. Sterically controlled azomethine ylide cycloaddition polymerization of phenyl-C61-butyric acid methyl ester.

    PubMed

    Stephen, Meera; Ramanitra, Hasina H; Santos Silva, Hugo; Dowland, Simon; Bégué, Didier; Genevičius, Kristijonas; Arlauskas, Kęstutis; Juška, Gytis; Morse, Graham E; Distler, Andreas; Hiorns, Roger C

    2016-05-01

    Phenyl-C61-butyric acid methyl ester (PCBM) is polymerized simply using a one-pot reaction to yield soluble, high molecular weight polymers. The sterically controlled azomethine ylide cycloaddition polymerization (SACAP) is demonstrated to be highly adaptable and yields polymers with probable Mn≈ 24 600 g mol(-1) and Mw≈ 73 800 g mol(-1). Products are metal-free and of possible benefit to organic and hybrid photovoltaics and electronics as they form thin films from solution and have raised LUMOs. The promising electronic properties of this new polymer are discussed. PMID:27066898

  1. Inorganic-organic hybrid coatings on stainless steel by layer-by-layer deposition and surface-initiated atom-transfer-radical polymerization for combating biocorrosion.

    PubMed

    Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

    2009-03-01

    To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements. PMID:20355986

  2. A poly(acrylonitrile)-functionalized porous aromatic framework synthesized by atom-transfer radical polymerization for the extraction of uranium from seawater

    DOE PAGESBeta

    Yue, Yanfeng; Zhang, Chenxi; Tang, Qing; Mayes, Richard T.; Liao, Wei -Po; Liao, Chen; Tsouris, Costas; Stankovich, Joseph J.; Chen, Jihua; Hensley, Dale K.; et al

    2015-10-30

    In order to ensure a sustainable reserve of fuel for nuclear power generation, tremendous research efforts have been devoted to developing advanced sorbent materials for extracting uranium from seawater. In this work, a porous aromatic framework (PAF) was surface-functionalized with poly(acrylonitrile) through atom-transfer radical polymerization (ATRP). Batches of this adsorbent were conditioned with potassium hydroxide (KOH) at room temperature or 80 °C prior to contact with a uranium-spiked seawater simulant, with minimal differences in uptake observed as a function of conditioning temperature. A maximum capacity of 4.81 g-U/kg-ads was obtained following 42 days contact with uranium-spiked filtered environmental seawater, whichmore » demonstrates a comparable adsorption rate. A kinetic investigation revealed extremely rapid uranyl uptake, with more than 80% saturation reached within 14 days. Furthermore, relying on the semiordered structure of the PAF adsorbent, density functional theory (DFT) calculations reveal cooperative interactions between multiple adsorbent groups yield a strong driving force for uranium binding.« less

  3. A poly(acrylonitrile)-functionalized porous aromatic framework synthesized by atom-transfer radical polymerization for the extraction of uranium from seawater

    SciTech Connect

    Yue, Yanfeng; Zhang, Chenxi; Tang, Qing; Mayes, Richard T.; Liao, Wei -Po; Liao, Chen; Tsouris, Costas; Stankovich, Joseph J.; Chen, Jihua; Hensley, Dale K.; Abney, Carter W.; Jiang, De-en; Brown, Suree; Dai, Sheng

    2015-10-30

    In order to ensure a sustainable reserve of fuel for nuclear power generation, tremendous research efforts have been devoted to developing advanced sorbent materials for extracting uranium from seawater. In this work, a porous aromatic framework (PAF) was surface-functionalized with poly(acrylonitrile) through atom-transfer radical polymerization (ATRP). Batches of this adsorbent were conditioned with potassium hydroxide (KOH) at room temperature or 80 °C prior to contact with a uranium-spiked seawater simulant, with minimal differences in uptake observed as a function of conditioning temperature. A maximum capacity of 4.81 g-U/kg-ads was obtained following 42 days contact with uranium-spiked filtered environmental seawater, which demonstrates a comparable adsorption rate. A kinetic investigation revealed extremely rapid uranyl uptake, with more than 80% saturation reached within 14 days. Furthermore, relying on the semiordered structure of the PAF adsorbent, density functional theory (DFT) calculations reveal cooperative interactions between multiple adsorbent groups yield a strong driving force for uranium binding.

  4. Preparation of a magnetic molecularly imprinted polymer by atom-transfer radical polymerization for the extraction of parabens from fruit juices.

    PubMed

    You, Xiaoxiao; Piao, Chungying; Chen, Ligang

    2016-07-01

    A silica-based surface magnetic molecularly imprinted polymer for the selective recognition of parabens was prepared using a facile and general method that combined atom-transfer radical polymerization with surface imprinting technique. The prepared magnetic molecularly imprinted polymer was characterized by transmission electron microscopy, Fourier transform infrared spectrometry and physical property measurement. The isothermal adsorption experiment and kinetics adsorption experiment investigated the adsorption property of magnetic molecularly imprinted polymer to template molecule. The four parabens including methylparaben, ethylparaben, propylparaben, and butylparaben were used to assess the rebinding selectivity. An extraction method, which used magnetic molecularly imprinted polymer as adsorbents coupled with high-performance liquid chromatography for the determination of the four parabens in fruit juice samples was developed. Under the optimal conditions, the limits of detections of the four parabens were 0.028, 0.026, 0.021, and 0.026 mg/L, respectively. The precision expressed as relative standard deviation ranging from 2.6 to 8.9% was obtained. In all three fortified levels, recoveries of parabens were in the range of 72.5-89.4%. The proposed method has been applied to different fruit juice samples including orange juice, grape juice, apple juice and peach juice, and satisfactory results were obtained. PMID:27214157

  5. Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

    PubMed Central

    Lin, Jing; Kong, Tao; Ye, Lin; Zhang, Ai-ying

    2015-01-01

    Summary Pentablock copolymers PMA-PPO-PEO-PPO-PMA synthesized via atom transfer radical polymerization (ATRP) were self-assembled with varying amounts of γ-CDs to prepare poly(pseudorotaxanes) (PPRs). When the concentration of γ-CDs was lower, the central PEO segment served as a shell of the micelles and was preferentially bent to pass through the γ-CD cavity to construct double-chain-stranded tight-fit PPRs characterized by a channel-like crystal structure. With an increase in the amount of γ-CDs added, they began to accommodate the poly(methyl acrylate) (PMA) segments dissociated from the core of the micelles. When more γ-CDs were threaded and slipped over the segments, the γ-CDs were randomly distributed along the pentablock copolymer chain to generate single-chain-stranded loose-fit PPRs and showed no characteristic channel-like crystal structure. All the self-assembly processes of the pentablock copolymers resulted in the formation of hydrogels. After endcapping via in situ ATRP of 2-methacryloyloxyethyl phosphorylcholine (MPC), these single-chain-stranded loose-fit PPRs were transformed into conformational identical polyrotaxanes (PRs). The structures of the PPRs and PRs were characterized by means of 1H NMR, GPC, 13C CP/MAS NMR, 2D 1H NOESY NMR, FTIR, WXRD, TGA and DSC analyses. PMID:26732122

  6. Green polymer chemistry: investigating the mechanism of radical ring-opening redox polymerization (R3P) of 3,6-dioxa-1,8-octanedithiol (DODT).

    PubMed

    Rosenthal-Kim, Emily Q; Puskas, Judit E

    2015-01-01

    The mechanism of the new Radical Ring-opening Redox Polymerization (R3P) of 3,6-dioxa-1,8-octanedithiol (DODT) by triethylamine (TEA) and dilute H2O2 was investigated. Scouting studies showed that the formation of high molecular weight polymers required a 1:2 molar ratio of DODT to TEA and of DODT to H2O2. Further investigation into the chemical composition of the organic and aqueous phases by 1H-NMR spectroscopy and mass spectrometry demonstrated that DODT is ionized by two TEA molecules (one for each thiol group) and thus transferred into the aqueous phase. The organic phase was found to have cyclic disulfide dimers, trimers and tetramers. Dissolving DODT and TEA in water before the addition of H2O2 yielded a polymer with Mn = 55,000 g/mol, in comparison with Mn = 92,000 g/mol when aqueous H2O2 was added to a DODT/TEA mixture. After polymer removal, MALDI-ToF MS analysis of the residual reaction mixtures showed only cyclic oligomers remaining. Below the LCST for TEA in water, 18.7 °C, the system yielded a stable emulsion, and only cyclic oligomers were found. Below DODT/TEA and H2O2 1:2 molar ratio mostly linear oligomers were formed, with <20% cyclic oligomers. The findings support the proposed mechanism of R3P. PMID:25871370

  7. Using the Interior Cavity of the P22 Capsid for Site Specific Initiation of Atom Transfer Radical Polymerization with Tremendously Increased Cargo Loading

    PubMed Central

    Lucon, Janice; Qazi, Shefah; Uchida, Masaki; Bedwel, Gregory J.; LaFrance, Ben; Prevelige, Peter E.; Douglas, Trevor

    2013-01-01

    Virus-like particles (VLPs) have emerged as important and versatile architectures for chemical manipulation in the development of functional hybrid nanostructures. Here we have successfully demonstrated the site selective initiation of atom transfer radical polymerization (ATRP) reactions to form an addressable polymer constrained within the interior cavity of a VLP. This protein-polymer hybrid, of P22 and crosslinked poly(2-aminoethyl methacrylate), is potentially useful as a new high-density delivery vehicle for encapsulation and delivery of small molecule cargos. In particular, the encapsulated polymer can act as a scaffold for the attachment of primary amine reactive molecules of interest, such as a fluorescein dye or a Gd-DTPA MRI contrast agent. Using this approach, a significant increase in labeling density of the VLP, compared to previous modifications of VLPs, can be achieved. These results highlight the use of multimeric protein-polymer conjugates for their potential utility in the development of VLP-based MRI contrast agents with the possibility of loading other cargos. PMID:23000990

  8. Synthesis and Characterization of Surface Grafted Poly(N-isopropylacrylamide) and Poly(Carboxylic Acid)– Iron Particles via Atom Transfer Radical Polymerization for Biomedical Applications

    PubMed Central

    Sutrisno, Joko; Fuchs, Alan; Evrensel, Cahit

    2014-01-01

    This research relates to the preparation and characterization of surface grafted poly(N-isopropylacrylamide) and poly(carboxylic acid)–micron-size iron particles via atom transfer radical polymerization (ATRP). The surface grafted polymers–iron particles result in multifunctional materials which can be used in biomedical applications. The functionalities consist of cell targeting, imaging, drug delivery, and immunological response. The multifunctional materials are synthesized in two steps. First, surface grafting is used to place polymer molecules on the iron particles surface. The second step, is conjugation of the bio-molecules onto the polymer backbone. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy were used to confirm the presence of polymers on the iron particles. The thickness of the grafted polymers and glass transition temperature of the surface grafted polymers were determined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The covalent bond between grafted polymers and iron particles caused higher glass transition temperature as compared with non-grafted polymers. The ability to target the bio-molecule and provide fluorescent imaging was simulated by conjugation of rat immunoglobulin and fluorescein isothiocyanate (FITC) labeled anti-rat. The fluorescence intensity was determined using flow cytometry and conjugated IgG-FITC anti-rat on iron particles which was imaged using a fluorescence microscopy. PMID:25382869

  9. Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)

    PubMed Central

    2008-01-01

    Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

  10. Kinetics of nucleation-controlled polymerization. A perturbation treatment for use with a secondary pathway.

    PubMed Central

    Bishop, M F; Ferrone, F A

    1984-01-01

    We present a perturbation method for analyzing nucleation-controlled polymerization augmented by a secondary pathway for polymer growth. With this method, the solution to the kinetic equations assumes a simple analytic closed form that can easily be used in fitting data. So long as the formation of polymers by the secondary pathway depends linearly on the concentration of monomers polymerized, the form of the solutions is the same. This permits the analysis of augmented growth models with a minimum number of modeling assumptions, and thus makes it readily possible to distinguish between a variety of secondary processes (heterogeneous nucleation, lateral growth, and fragmentation). In addition, the parameters of the homogeneous process, such as the homogeneous nucleus size, can be determined independent of the nature of the secondary mechanism. We describe applications of this method to the polymerization of actin, collagen, and sickle hemoglobin. We present an extensive analysis of data on actin polymerization (Wegner, A., and P. Savko, 1982, Biochemistry, 21:1909-1913) to illustrate the use of the method. Although our conclusions generally agree with theirs, we find that lateral growth describes the secondary pathway better than the fragmentation model originally proposed. We also show how this method can be used to study the degree of polymerization, the parentage of polymers, and the behavior of polymers in cycling experiments. PMID:6498276

  11. CONTROLLED/LIVING RADICAL POLYMERIZATION: THE NEXT FRONTIER IN POLYMER SCIENCE? (R826735)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. CONTROLLED/LIVING RADICAL POLYMERIZATION APPLIED TO WATER-BORNE SYSTEMS. (R826735)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. STATISTICAL, GRADIENT, BLOCK AND GRAFT COPOLYMERS BY CONTROLLED/LIVING RADICAL POLYMERIZATIONS. (R829580)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Multi input single output model predictive control of non-linear bio-polymerization process

    NASA Astrophysics Data System (ADS)

    Arumugasamy, Senthil Kumar; Ahmad, Z.

    2015-05-01

    This paper focuses on Multi Input Single Output (MISO) Model Predictive Control of bio-polymerization process in which mechanistic model is developed and linked with the feedforward neural network model to obtain a hybrid model (Mechanistic-FANN) of lipase-catalyzed ring-opening polymerization of ɛ-caprolactone (ɛ-CL) for Poly (ɛ-caprolactone) production. In this research, state space model was used, in which the input to the model were the reactor temperatures and reactor impeller speeds and the output were the molecular weight of polymer (Mn) and polymer polydispersity index. State space model for MISO created using System identification tool box of Matlab™. This state space model is used in MISO MPC. Model predictive control (MPC) has been applied to predict the molecular weight of the biopolymer and consequently control the molecular weight of biopolymer. The result shows that MPC is able to track reference trajectory and give optimum movement of manipulated variable.

  15. Multi input single output model predictive control of non-linear bio-polymerization process

    SciTech Connect

    Arumugasamy, Senthil Kumar; Ahmad, Z.

    2015-05-15

    This paper focuses on Multi Input Single Output (MISO) Model Predictive Control of bio-polymerization process in which mechanistic model is developed and linked with the feedforward neural network model to obtain a hybrid model (Mechanistic-FANN) of lipase-catalyzed ring-opening polymerization of ε-caprolactone (ε-CL) for Poly (ε-caprolactone) production. In this research, state space model was used, in which the input to the model were the reactor temperatures and reactor impeller speeds and the output were the molecular weight of polymer (M{sub n}) and polymer polydispersity index. State space model for MISO created using System identification tool box of Matlab™. This state space model is used in MISO MPC. Model predictive control (MPC) has been applied to predict the molecular weight of the biopolymer and consequently control the molecular weight of biopolymer. The result shows that MPC is able to track reference trajectory and give optimum movement of manipulated variable.

  16. Fabrication of Polymeric Coatings with Controlled Microtopographies Using an Electrospraying Technique.

    PubMed

    Guo, Qiongyu; Mather, Jason P; Yang, Pine; Boden, Mark; Mather, Patrick T

    2015-01-01

    Surface topography of medical implants provides an important biophysical cue on guiding cellular functions at the cell-implant interface. However, few techniques are available to produce polymeric coatings with controlled microtopographies onto surgical implants, especially onto implant devices of small dimension and with complex structures such as drug-eluting stents. Therefore, the main objective of this study was to develop a new strategy to fabricate polymeric coatings using an electrospraying technique based on the uniqueness of this technique in that it can be used to produce a mist of charged droplets with a precise control of their shape and dimension. We hypothesized that this technique would allow facile manipulation of coating morphology by controlling the shape and dimension of electrosprayed droplets. More specifically, we employed the electrospraying technique to coat a layer of biodegradable polyurethane with tailored microtopographies onto commercial coronary stents. The topography of such stent coatings was modulated by controlling the ratio of round to stretched droplets or the ratio of round to crumped droplets under high electric field before deposition. The shape of electrosprayed droplets was governed by the stability of these charged droplets right after ejection or during their flight in the air. Using the electrospraying technique, we achieved conformal polymeric coatings with tailored microtopographies onto conductive surgical implants. The approach offers potential for controlling the surface topography of surgical implant devices to modulate their integration with surrounding tissues. PMID:26090663

  17. Fabrication of Polymeric Coatings with Controlled Microtopographies Using an Electrospraying Technique

    PubMed Central

    Guo, Qiongyu; Mather, Jason P.; Yang, Pine; Boden, Mark; Mather, Patrick T.

    2015-01-01

    Surface topography of medical implants provides an important biophysical cue on guiding cellular functions at the cell-implant interface. However, few techniques are available to produce polymeric coatings with controlled microtopographies onto surgical implants, especially onto implant devices of small dimension and with complex structures such as drug-eluting stents. Therefore, the main objective of this study was to develop a new strategy to fabricate polymeric coatings using an electrospraying technique based on the uniqueness of this technique in that it can be used to produce a mist of charged droplets with a precise control of their shape and dimension. We hypothesized that this technique would allow facile manipulation of coating morphology by controlling the shape and dimension of electrosprayed droplets. More specifically, we employed the electrospraying technique to coat a layer of biodegradable polyurethane with tailored microtopographies onto commercial coronary stents. The topography of such stent coatings was modulated by controlling the ratio of round to stretched droplets or the ratio of round to crumped droplets under high electric field before deposition. The shape of electrosprayed droplets was governed by the stability of these charged droplets right after ejection or during their flight in the air. Using the electrospraying technique, we achieved conformal polymeric coatings with tailored microtopographies onto conductive surgical implants. The approach offers potential for controlling the surface topography of surgical implant devices to modulate their integration with surrounding tissues. PMID:26090663

  18. L-Arabinose (pyranose and furanose rings)-branched poly (vinylalcohol): enzymatic synthesis of the sugar esters followed by free radical polymerization.

    PubMed

    Rodrigues Borges, Maurício; Balaban, Rosangela de Carvalho

    2014-12-20

    Herein this study reports the successful synthesis of a new poly(vinyl alcohol) (PVA), containing L-arabinose (L-arabinopyranose and arabinofuranose isomers) branched in only two steps: (1) production of polymerizable monomers of L-arabinose isomers (pyranose and furanose forms) through enzymatic synthesis using alkaline protease from Bacillus subtilis as catalyst and two substrates: L-arabinose and Divinyl Adipate (DVA) in N,N-dimethylformamide (DMF); (2) radical polymerization of the monomers, using an initiator system consisting of potassium persulfate and hydrogen peroxide in water. The transesterification of DVA with L-arabinose was monitored via qualitative analysis by TLC, confirming the formation of the vinyl sugar ester. The acylation occurred on the two different cyclic conformations of the L-arabinose which coexist in equilibrium: (α/β) arabinofuranose and (α/β) arabinopyranose. The acylation positions and the chemical structure of the 5-O-vinyl adipoyl L-arabinofuranose and 4-O-vinyl adipolyl L-arabinopyranose formed were determined by 13C NMR. The surface activity of the L-arabinose esters mixture (monomers) was compared with a commercial product based on phenol formaldehyde polyoxyalkylene polyamine, largely used as surfactant in many industries. FTIR spectroscopy of the sugar ester monomers and the respective polymer were compared revealing the disappearance of the vinyl group in the polymer spectrum. The polymer number-average molar mass (Mn) and the weight-average molar mass (Mw) were determined by gel permeation chromatography (GPC) presenting the following results: 2.9 × 10(4) Da and 7.2 × 10(4) Da, respectively, and polydispersity (Mw/Mn) equal to 2.48. PMID:25450639

  19. Impact of Alkyl Spacer Length on Aggregation Pathways in Kinetically Controlled Supramolecular Polymerization.

    PubMed

    Ogi, Soichiro; Stepanenko, Vladimir; Thein, Johannes; Würthner, Frank

    2016-01-20

    We have investigated the kinetic and thermodynamic supramolecular polymerizations of a series of amide-functionalized perylene bisimide (PBI) organogelator molecules bearing alkyl spacers of varied lengths (ethylene to pentylene chains, PBI-1-C2 to PBI-1-C5) between the amide and PBI imide groups. These amide-functionalized PBIs form one-dimensional fibrous nanostructures as the thermodynamically favored states in solvents of low polarity. Our in-depth studies revealed, however, that the kinetic behavior of their supramolecular polymerization is dependent on the spacer length. Propylene- and pentylene-tethered PBIs follow a similar polymerization process as previously observed for the ethylene-tethered PBI. Thus, the monomers of these PBIs are kinetically trapped in conformationally restricted states through intramolecular hydrogen bonding between the amide and imide groups. In contrast, the intramolecularly hydrogen-bonded monomers of butylene-tethered PBI spontaneously self-assemble into nanoparticles, which constitute an off-pathway aggregate state with regard to the thermodynamically stable fibrous supramolecular polymers obtained. Thus, for this class of π-conjugated system, an unprecedented off-pathway aggregate with high kinetic stability could be realized for the first time by introducing an alkyl linker of optimum length (C4 chain) between the amide and imide groups. Our current system with an energy landscape of two competing nucleated aggregation pathways is applicable to the kinetic control over the supramolecular polymerization by the seeding approach. PMID:26699283

  20. Of Radicals and DREAMers: Harnessing Exceptionality to Challenge Immigration Control

    ERIC Educational Resources Information Center

    Heredia, Luisa Laura

    2015-01-01

    This article contributes to the literature on undocumented youth activism and citizenship by assessing undocumented youth's challenges to a growing regime of migration control in the US. It uses Doug McAdam's tactical interaction as an analytical lens to explore two consecutive high-risk campaigns, ICE infiltrations and expulsion/re-entry. In this…

  1. Biodegradable polymeric microcarriers with controllable porous structure for tissue engineering.

    PubMed

    Shi, Xudong; Sun, Lei; Jiang, Jian; Zhang, Xiaolin; Ding, Wenjun; Gan, Zhihua

    2009-12-01

    Porous microspheres fabricated by biodegradable polymers show great potential as microcarriers for cell cultivation in tissue engineering. Herein biodegradable poly(DL-lactide) (PLA) was used to fabricate porous microspheres through a modified double emulsion solvent evaporation method. The influence of fabrication parameters, such as the stirring speed of the primary and secondary emulsion, the polymer concentration of the oil phase, and solvent type, as well as the post-hydrolysis treatment of the porous structure of the PLA microspheres are discussed. Good attachment and an active spread of MG-63 cells on the microspheres is observed, which indicates that the PLA microspheres with controllable porous structure are of great potential as cell delivery carriers for tissue engineering. PMID:19821453

  2. Fabrication and control of CT number through polymeric composites based on coronary plaque CT phantom applications.

    PubMed

    Hoy, Carlton F O; Naguib, Hani E; Paul, Narinder

    2016-01-01

    Biomedical phantoms are commonly used for various medical imaging modalities to improve imaging quality and procedures. Current biomedical phantoms fabricated commercially are high in cost and limited in the specificity of human environments and structures that can be mimicked. This study aimed to control the measurable computed tomography (CT) number in Hounsfield units through polymeric biomedical phantom materials using controlled amounts of hydroxyapatite (hA). The purpose was to fabricate CT phantoms capable of mimicking various coronary plaque types while introducing a fabrication technique and basis for a numerical model to which the technique may be applied. The CT number is tunable based on the controlled material properties of electron density and atomic numbers. Three different polymeric matrices of polyethylene (PE), thermoplastic polyurethane (TPU), and polyvinylidene fluoride (PVDF) were selected due to their varied specific densities and ease of fabrication acting as integral properties for CT phantom fabrication. These polymers were processed together with additions of hA in mass percentages of 2.5, 5, 10, and 20% hA as well as a 0% hA as a control for each polymeric material. By adding hA to PE, TPU, and PVDF an increasing trend was exhibited between CT number and weight percent of hA. PMID:26958580

  3. Wettability control by laser texturing process generating localized gold nanoparticles on polymeric thin films.

    PubMed

    Spano, F; Castellano, A; Massaro, A; Fragouli, D; Cingolani, R; Athanassiou, A

    2012-06-01

    In this work a new approach is introduced for surface properties control by laser texturing process. By UV laser irradiation, we are able to control the surface wettability of a chitosan polymeric film in which is introduced a chloroauric acid salt by immersion. Specifically the UV irradiation is responsible for the creation of gold nanoparticles at the irradiated surface of the polymeric film. This photolytic process allows us to localize and design accurately surface patterns and moreover to tune metallic particle size in the range of nanoscale. After the characterization of our gold textured surfaces by atomic force and scanning electron microscopies, we demonstrate the link between wettability surface properties and gold nanoparticles size. The experimental results indicate the influence of the laser intensity, the irradiation time and the polymer film thickness (by increasing the gold concentration) on the gold nanoparticle density and size. PMID:22905535

  4. Radical prostatectomy

    MedlinePlus

    Prostatectomy - radical; Radical retropubic prostatectomy; Radical perineal prostatectomy; Laparoscopic radical prostatectomy; LRP; Robotic-assisted laparoscopic prostatectomy; RALP; Pelvic lymphadenectomy; ...

  5. Polymeric nanostructures with pH-labile core for controlled drug release.

    PubMed

    Banerjee, Rakesh; Maiti, Saikat; Dey, Debabrata; Dhara, Dibakar

    2016-01-15

    Efficient and stimuli-triggered controlled delivery of therapeutics is one of the important issues in modern advanced therapy. In the present work, a versatile route for the synthesis of core cross-linked polymeric nanostructures (CLPN) through thiol-acrylate Michael addition reaction via the formation of β-thiopropionate has been described. The acid groups of the poly(acrylic acid) block of poly(ethylene glycol)-b-poly(N-isopropylacrylamide)-b-poly(acrylic acid) triblock copolymer were reacted with 2-hydroxyethyl acrylate (HEA) to yield the corresponding acrylate-functionalized copolymer (P1). Following this, P1 was reacted with a thiol functionalized cross-linker (CL) resulting in the formation of core cross-linked polymeric nanoparticles through acrylate-thiol Michael reaction. The ability of these nanoparticles to encapsulate drug molecules inside their core and their effective release following a pH-triggered controlled degradation of the core were demonstrated. The temperature sensitive release behaviour of the system was also studied. The non-toxic nature of the precursor polymers and the core cross-linked polymeric nanoparticles was also established, that further substantiated their potential as carriers for controlled release of drugs. PMID:26454376

  6. Polymethyl methacrylate-co-methacrylic acid coatings with controllable concentration of surface carboxyl groups: A novel approach in fabrication of polymeric platforms for potential bio-diagnostic devices

    NASA Astrophysics Data System (ADS)

    Hosseini, Samira; Ibrahim, Fatimah; Djordjevic, Ivan; Koole, Leo H.

    2014-05-01

    The generally accepted strategy in development of bio-diagnostic devices is to immobilize proteins on polymeric surfaces as a part of detection process for diseases and viruses through antibody/antigen coupling. In that perspective, polymer surface properties such as concentration of functional groups must be closely controlled in order to preserve the protein activity. In order to improve the surface characteristics of transparent polymethacrylate plastics that are used for diagnostic devices, we have developed an effective fabrication procedure of polymethylmetacrylate-co-metacrylic acid (PMMA-co-MAA) coatings with controlled number of surface carboxyl groups. The polymers were processed effectively with the spin-coating technique and the detailed control over surface properties is here by demonstrated through the variation of a single synthesis reaction parameter. The chemical structure of synthesized and processed co-polymers has been investigated with nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS). The surface morphology of polymer coatings have been analyzed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). We demonstrate that the surface morphology and the concentration of surface -COOH groups (determined with UV-vis surface titration) on the processed PMMA-co-MAA coatings can be precisely controlled by variation of initial molar ratio of reactants in the free-radical polymerization reaction. The wettability of developed polymer surfaces also varies with macromolecular structure.

  7. Controlling and understanding the polymerization shrinkage-induced stresses in light-cured composites.

    PubMed

    Suh, B I

    1999-01-01

    The shrinkage of composites induces stress in the final restoration when the composite is bonded to the tooth surface. The amount of stress can be controlled by the method of pulse-delay cure used. The development of new composites has changed the energy requirements for obtaining polymerization. The total energy required for optimal polymerization has been reduced and the rate at which the energy is delivered can have a strong effect on the final properties of the restoration. Newer composites may employ different photoinitiators, making the spectral emission from the curing light an important factor for properties of the final restoration. It is proposed that labels for composites carry: (1) indications for the total energy required; (2) specification of the pulse-delay cure if applicable; and (3) the required spectral bandwidth of the curing lamp light emission. PMID:11908394

  8. Anchoring energy enhancement and pretilt angle control of liquid crystal alignment on polymerized surfaces

    NASA Astrophysics Data System (ADS)

    Weng, Libo; Liao, Pei-Chun; Lin, Chen-Chun; Ting, Tien-Lun; Hsu, Wen-Hao; Su, Jenn-Jia; Chien, Liang-Chy

    2015-09-01

    We demonstrate enhanced surface anchoring energy and control of pretilt angle in a nematic liquid crystal cell with vertical alignment and polymerized surfaces (PS-VA). The polymerized surfaces are formed by ultraviolet (UV) irradiation-induced phase separation of a minute amount of a reactive monomer in the vertical-aligned nematic liquid crystal. By introducing a bias voltage during UV curing, surface-localized polymer protrusions with a dimension of 100nm and a field-induced pretilt angle are observed. Experimental evidences and theoretical analyses validate that PS-VA has increased surface anchoring strength by two folds and pretilt angle has been changed from 89° to 86° compared to those of a VA cell. The enabling PS-VA cell technique with excel electro-optical properties such as very good dark state, high optical contrast, and fast rise and decay times may lead to development of a wide range of applications.

  9. Anchoring energy enhancement and pretilt angle control of liquid crystal alignment on polymerized surfaces

    SciTech Connect

    Weng, Libo; Chien, Liang-Chy; Liao, Pei-Chun; Lin, Chen-Chun; Ting, Tien-Lun; Hsu, Wen-Hao; Su, Jenn-Jia

    2015-09-15

    We demonstrate enhanced surface anchoring energy and control of pretilt angle in a nematic liquid crystal cell with vertical alignment and polymerized surfaces (PS-VA). The polymerized surfaces are formed by ultraviolet (UV) irradiation-induced phase separation of a minute amount of a reactive monomer in the vertical-aligned nematic liquid crystal. By introducing a bias voltage during UV curing, surface-localized polymer protrusions with a dimension of 100nm and a field-induced pretilt angle are observed. Experimental evidences and theoretical analyses validate that PS-VA has increased surface anchoring strength by two folds and pretilt angle has been changed from 89° to 86° compared to those of a VA cell. The enabling PS-VA cell technique with excel electro-optical properties such as very good dark state, high optical contrast, and fast rise and decay times may lead to development of a wide range of applications.

  10. Radical Decisions in Cancer: Redox Control of Cell Growth and Death

    PubMed Central

    Sainz, Rosa M.; Lombo, Felipe; Mayo, Juan C.

    2012-01-01

    Free radicals play a key role in many physiological decisions in cells. Since free radicals are toxic to cellular components, it is known that they cause DNA damage, contribute to DNA instability and mutation and thus favor carcinogenesis. However, nowadays it is assumed that free radicals play a further complex role in cancer. Low levels of free radicals and steady state levels of antioxidant enzymes are responsible for the fine tuning of redox status inside cells. A change in redox state is a way to modify the physiological status of the cell, in fact, a more reduced status is found in resting cells while a more oxidative status is associated with proliferative cells. The mechanisms by which redox status can change the proliferative activity of cancer cells are related to transcriptional and posttranscriptional modifications of proteins that play a critical role in cell cycle control. Since cancer cells show higher levels of free radicals compared with their normal counterparts, it is believed that the anti-oxidative stress mechanism is also increased in cancer cells. In fact, the levels of some of the most important antioxidant enzymes are elevated in advanced status of some types of tumors. Anti-cancer treatment is compromised by survival mechanisms in cancer cells and collateral damage in normal non-pathological tissues. Though some resistance mechanisms have been described, they do not yet explain why treatment of cancer fails in several tumors. Given that some antitumoral treatments are based on the generation of free radicals, we will discuss in this review the possible role of antioxidant enzymes in the survival mechanism in cancer cells and then, its participation in the failure of cancer treatments. PMID:24213319

  11. Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

    PubMed

    Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

    2014-12-10

    In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be

  12. Automatic, continuous online monitoring of polymerization reactions (ACOMP): Progress in characterization of polymers and polymerization reactions

    NASA Astrophysics Data System (ADS)

    Alb, Alina M.

    An original method is presented as an efficient technique for characterizing polymers, and understanding the kinetics of the polymerization reactions. The Automatic Continuous Online Monitoring of Polymerization Reactions (ACOMP) method developed at Tulane University involves following one or more characteristics of a polymerization reaction: monomer conversion, different molecular weight averages, intrinsic viscosity, etc. By performing an automatic withdrawal and dilution of the polymer solution to create a small stream which flows through a detector train, including light scattering, viscometer, refractive index, Ultraviolet/Visible detectors, a continuum of data points can be obtained, allowing powerful analysis methods to be developed. The goal of this work is to expand ACOMP to new polymerization reactions, such as free radical copolymerization, controlled radical polymerization, inverse emulsion polymerization, both to achieve a complete physical characterization of the polymers synthesized and a better understanding of the reaction mechanisms. For each of the reactions ACOMP brings significant innovations in the analysis of the kinetics. Other new methods, such as Automatic Continuous Mixing (ACM) and Simultaneous Multiple Sample Light Scattering (SMSLS) are also used, as well as traditional multi-detector Size Exclusion Chromatography (SEC). As an immediate consequence it is hoped that the information on reaction kinetics and mechanisms offer a better fundamental knowledge, control and ability to optimize reactions. At the industrial scale, online monitoring should allow a more efficient use of resources, energy, reactor and personnel time as well as a higher product quality.

  13. Surface morphology control of cross-linked polymer particles via dispersion polymerization.

    PubMed

    Peng, Bo; Imhof, Arnout

    2015-05-14

    Cross-linked polymer colloids (poly(methyl methacrylate) and polystyrene) with diverse shapes were prepared in polar solvents (ethanol, methanol and water) via dispersion polymerization, in which a linear addition of the cross-linker was used during reaction. Apart from spherical particles we found dented spheres or particles covered with nodules, or a combination of both. A comprehensive investigation was carried out, mainly concentrating on the effect of the experimental conditions (e.g., the addition start time and total addition time, cross-linker density and the solvency of the solvents) on particle morphologies. Consequently, we suggest a number of effective ways for the synthesis of regular (spherical) colloidal particles through maintaining a relatively low concentration of the cross-linker during the entire reaction, or forcing the co-polymerization (of monomer and cross-linker) locus to the continuous medium, or using a high quality or quantity of the stabilizer. Moreover, the size of the particles was also precisely manipulated by varying the polarity of the solvents, the concentration of the cross-linker, and the amount and average molecular weight of the stabilizer. In addition, the formation of the heavily dented particles with a very rough surface prepared under a pure or oxygen-'contaminated' nitrogen environment was monitored over time. The results accumulated in this article are of use for a better understanding of the mechanism of the polymerization and control over the structure and property of polymer particles. PMID:25793973

  14. Preparations and properties of a tunable void with shell thickness SiO2@SiO2 core-shell structures via activators generated by electron transfer for atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Ren, Yi-xian; Zhou, Guo-wei; Cao, Pei

    2016-02-01

    Core-shell structure nanoparticles are attracting considerable attention because of their applications in drug delivery, catalysis carrier, and nanomedicine. In this study, SiO2@SiO2 core-shell structure with tunable void and shell thickness was successfully prepared for the first time using SiO2-poly(buty acrylate) (PBA)-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) (SiO2-PBA-b-PDMAEMA) as the template and tetraethoxysilane (TEOS) as the silica source. An amphiphilic copolymer PBA-b-PDMAEMA was first grafted onto the SiO2 nanosphere surface through activators regenerated by electron transfer for atom transfer radical polymerization. TEOS was hydrolyzed along with the PDMAEMA chain through hydrogen bonding, and the core-shell structure of SiO2@SiO2 was obtained through calcination to remove the copolymer. The gradient hydrophilicity of the PBA-b-PDMAEMA copolymer template facilitated the hydrolysis of TEOS molecules along the PDMAEMA to PBA segments, thereby tuning the voids between the SiO2 core and SiO2 shell, as well as the SiO2 shell thickness. The voids were about 10-15 nm and the shell thicknesses were about 4-11 nm when adding different amounts of DMAEMA monomer. SiO2@SiO2 core-shell structures with tunable void and shell thickness were employed as supports for the loading and release of doxorubicin hydrochloride (DOX) in PBS (pH 4.0). The samples demonstrated good loading capacity and controlled release rate of DOX.

  15. Supramolecular polymerization of a prebiotic nucleoside provides insights into the creation of sequence-controlled polymers

    DOE PAGESBeta

    Wang, Jun; Bonnesen, Peter V; Rangel, E.; Vallejo, E.; Sanchez-Castillo, Ariadna; Cleaves, II, H. James; Baddorf, Arthur P; Sumpter, Bobby G; Pan, Minghu; Maksymovych, Petro; et al

    2016-01-04

    The self-assembly of a nucleoside on Au(111) was studied to ascertain whether polymerization on well-defined substrates constitutes a promising approach for making sequence-controlled polymers. Scanning tunneling microscopy and density functional theory were used to investigate the self-assembly on Au(111) of (RS)-N9-(2,3-dihydroxypropyl)adenine (DHPA), a plausibly prebiotic nucleoside analog of adenosine. It is found that DHPA molecules self-assemble into a hydrogen-bonded polymer that grows almost exclusively along the herringbone reconstruction pattern, has a two component sequence that is repeated over hundreds of nanometers, and is erasable with electron-induced excitation. Although the sequence is simple, more complicated ones are envisioned if two ormore » more nucleoside types are combined. Because polymerization occurs on a substrate in a dry environment, the success of each combination can be gauged with high-resolution imaging and accurate modeling techniques. The resulting characteristics make nucleoside self-assembly on a substrate an attractive approach for designing sequence-controlled polymers. Moreover, by choosing plausibly prebiotic nucleosides, insights may be provided into how nature created the first sequence-controlled polymers capable of storing information. Such insights, in turn, can inspire new ways of synthesizing sequence-controlled polymers.« less

  16. Supramolecular polymerization of a prebiotic nucleoside provides insights into the creation of sequence-controlled polymers

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Bonnesen, Peter V.; Rangel, E.; Vallejo, E.; Sanchez-Castillo, Ariadna; James Cleaves, H., II; Baddorf, Arthur P.; Sumpter, Bobby G.; Pan, Minghu; Maksymovych, Petro; Fuentes-Cabrera, Miguel

    2016-01-01

    Self-assembly of a nucleoside on Au(111) was studied to ascertain whether polymerization on well-defined substrates constitutes a promising approach for making sequence-controlled polymers. Scanning tunneling microscopy and density functional theory were used to investigate the self-assembly on Au(111) of (RS)-N9-(2,3-dihydroxypropyl)adenine (DHPA), a plausibly prebiotic nucleoside analog of adenosine. It is found that DHPA molecules self-assemble into a hydrogen-bonded polymer that grows almost exclusively along the herringbone reconstruction pattern, has a two component sequence that is repeated over hundreds of nanometers, and is erasable with electron-induced excitation. Although the sequence is simple, more complicated ones are envisioned if two or more nucleoside types are combined. Because polymerization occurs on a substrate in a dry environment, the success of each combination can be gauged with high-resolution imaging and accurate modeling techniques. These characteristics make nucleoside self-assembly on a substrate an attractive approach for designing sequence-controlled polymers. Further, by choosing plausibly prebiotic nucleosides, insights may be provided into how nature created the first sequence-controlled polymers capable of storing information. Such insights, in turn, can inspire new ways of synthesizing sequence-controlled polymers.

  17. Supramolecular polymerization of a prebiotic nucleoside provides insights into the creation of sequence-controlled polymers

    PubMed Central

    Wang, Jun; Bonnesen, Peter V.; Rangel, E.; Vallejo, E.; Sanchez-Castillo, Ariadna; James Cleaves II, H.; Baddorf, Arthur P.; Sumpter, Bobby G.; Pan, Minghu; Maksymovych, Petro; Fuentes-Cabrera, Miguel

    2016-01-01

    Self-assembly of a nucleoside on Au(111) was studied to ascertain whether polymerization on well-defined substrates constitutes a promising approach for making sequence-controlled polymers. Scanning tunneling microscopy and density functional theory were used to investigate the self-assembly on Au(111) of (RS)-N9-(2,3-dihydroxypropyl)adenine (DHPA), a plausibly prebiotic nucleoside analog of adenosine. It is found that DHPA molecules self-assemble into a hydrogen-bonded polymer that grows almost exclusively along the herringbone reconstruction pattern, has a two component sequence that is repeated over hundreds of nanometers, and is erasable with electron-induced excitation. Although the sequence is simple, more complicated ones are envisioned if two or more nucleoside types are combined. Because polymerization occurs on a substrate in a dry environment, the success of each combination can be gauged with high-resolution imaging and accurate modeling techniques. These characteristics make nucleoside self-assembly on a substrate an attractive approach for designing sequence-controlled polymers. Further, by choosing plausibly prebiotic nucleosides, insights may be provided into how nature created the first sequence-controlled polymers capable of storing information. Such insights, in turn, can inspire new ways of synthesizing sequence-controlled polymers. PMID:26725380

  18. Supramolecular polymerization of a prebiotic nucleoside provides insights into the creation of sequence-controlled polymers.

    PubMed

    Wang, Jun; Bonnesen, Peter V; Rangel, E; Vallejo, E; Sanchez-Castillo, Ariadna; James Cleaves Ii, H; Baddorf, Arthur P; Sumpter, Bobby G; Pan, Minghu; Maksymovych, Petro; Fuentes-Cabrera, Miguel

    2016-01-01

    Self-assembly of a nucleoside on Au(111) was studied to ascertain whether polymerization on well-defined substrates constitutes a promising approach for making sequence-controlled polymers. Scanning tunneling microscopy and density functional theory were used to investigate the self-assembly on Au(111) of (RS)-N(9)-(2,3-dihydroxypropyl)adenine (DHPA), a plausibly prebiotic nucleoside analog of adenosine. It is found that DHPA molecules self-assemble into a hydrogen-bonded polymer that grows almost exclusively along the herringbone reconstruction pattern, has a two component sequence that is repeated over hundreds of nanometers, and is erasable with electron-induced excitation. Although the sequence is simple, more complicated ones are envisioned if two or more nucleoside types are combined. Because polymerization occurs on a substrate in a dry environment, the success of each combination can be gauged with high-resolution imaging and accurate modeling techniques. These characteristics make nucleoside self-assembly on a substrate an attractive approach for designing sequence-controlled polymers. Further, by choosing plausibly prebiotic nucleosides, insights may be provided into how nature created the first sequence-controlled polymers capable of storing information. Such insights, in turn, can inspire new ways of synthesizing sequence-controlled polymers. PMID:26725380

  19. Polymeric Nanoparticles with Precise Ratiometric Control over Drug Loading for Combination Therapy

    PubMed Central

    Aryal, Santosh; Hu, Che-Ming Jack; Zhang, Liangfang

    2011-01-01

    We report a novel approach for nanoparticle-based combination chemotherapy by concurrently incorporating two different types of drugs into a single polymeric nanoparticle with ratiometric control over the loading of the two drugs. By adapting metal alkoxide chemistry, we synthesize highly hydrophobic drug-poly-l-lactide (drug-PLA) conjugates, of which the polymer has the same chain length while the drug may differ. These drug-polymer conjugates are then encapsulated into lipid-coated polymeric nanoparticles through a single-step nanoprecipication method. Using doxorubicin (DOX) and camptothecin (CPT) as two model chemotherapy drugs, various ratios of DOX-PLA and CPT-PLA conjugates are loaded into the nanoparticles with over 90% loading efficiency. The resulting nanoparticles are uniform in size, size distribution and surface charge. The loading yield of DOX and CPT in the particles can be precisely controlled by simply adjusting the DOX-PLA:CPT-PLA molar ratio. Cellular cytotoxicity results show that the dual-drug loaded nanoparticles are superior to the corresponding cocktail mixtures of single-drug loaded nanoparticles. This dual-drug delivery approach offers a solution to the long-standing challenge in ratiometric control over the loading of different types of drugs onto the same drug delivery vehicle. We expect that this approach can be exploited for many types of chemotherapeutic agents containing hydroxyl groups and thus enable co-delivery of various drug combinations for combinatorial treatments of diseases. PMID:21696189

  20. Sustainable polymerizations in recoverable microemulsions.

    PubMed

    Chen, Zhenzhen; Yan, Feng; Qiu, Lihua; Lu, Jianmei; Zhou, Yinxia; Chen, Jiaxin; Tang, Yishan; Texter, John

    2010-03-16

    Free radical and atom-transfer radical polymerizations were conducted in monomer/ionic liquid microemulsions. After the polymerization and isolation of the resultant polymers, the mixture of the catalyst and ionic liquids (surfactant and continuous phase) can be recovered and reused, thereby dramatically improving the environmental sustainability of such chemical processing. The addition of monomer to recovered ionic liquid mixtures regenerates transparent, stable microemulsions that are ready for the next polymerization cycle upon addition of initiator. The method combines the advantages of IL recycling and microemulsion polymerization and minimizes environmental disposable effects from surfactants and heavy metal ions. PMID:20170175

  1. Correlating Thin-Film Radical Density with Charge Transport in Open-Shell Conducting Macromolecules

    NASA Astrophysics Data System (ADS)

    Hay, Martha; Jergens, Elizabeth; Boudouris, Bryan

    Within the class of radical polymers, stable open-shell species serve as the medium for charge transport by undergoing oxidation-reduction (redox) reactions. The kinetics of these reactions are rapid enough that they are not considered rate-limiting in the electronic interactions of these materials. Rather, the proximity of these radical sites is paramount as a synthetic handle. Unfortunately, controlling the density of radicals has proven challenging in radical polymer systems. Often radical functionality is imparted to a polymer, rather than polymerizing a radical-containing monomer unit. This can prove troublesome as longer reaction times, in the interest of higher radical functionality, can lead to the elimination of radicals. Thus, the consequential altering of the radical electronic interactions is not well understood. We have synthesized a series of polynorbornene-based radical monomers at controlled radical loadings such that the radical density was preserved from monomer to polymer synthesis. As such, we attribute any change in the macroscopic transport properties to a change in the spacing between radical sites. These results elucidate the role of radical site distribution on the electronic performance of nitroxide-based radical polymers.

  2. Supramolecular Architectures Based no Dehydro[24]annulenes: Toward the Controlled Synthesis of pi-Conjugated Nanotubular Materials via Topochemical Polymerization

    NASA Astrophysics Data System (ADS)

    Suzuki, Mitsuharu

    Chapter 1 overviews currently available synthetic methodologies of carbon nanomaterials. Conventional syntheses, stepwise chemical syntheses, and seeding/cloning approaches are described. Problems associated with each methodology are pointed out. Chapter 2 begins with introductions to the dehydroannulene-based synthesis of carbon nanomaterials and topochemical polymerization of butadiynes. This chapter then describes a new approach to achieve the controlled synthesis of tubular nanocarbon materials, namely multifold topochemical polymerization of dehydroannulenes. An extensive crystal-engineering study leads to successful formation of supramolecular nanotubes based on dehydro[24]annulenes. The obtained structures possess preferable packing parameters for the intended multifold topochemical polymerization. Chapter 3 explores on-surface self-assemblies of dehydro[24]annulenes. The relationship between the molecular structure and self-assembling behavior of is examined with the aid of scanning tunnel microscopy. This study paves the way for the topochemical polymerization of these compounds within surface-confined self-assemblies.

  3. Designing materials for advanced microelectronic patterning applications using controlled polymerization RAFT technology

    NASA Astrophysics Data System (ADS)

    Sheehan, Michael T.; Farnham, William B.; Chambers, Charles R.; Tran, Hoang V.; Okazaki, Hiroshi; Brun, Yefim; Romberger, Matthew L.; Sounik, James R.

    2011-04-01

    Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization technology enables the production of polymers possessing low polydispersity (PD) in high yield for many applications. RAFT technology also enables control over polymer architecture. With synthetic control over these polymer characteristics, a variety of polymers can be designed and manufactured for use in advanced electronic applications. By matching the specific RAFT reagent and monomer combinations, we can accommodate monomer reactivity and optimize acrylate or methacrylate polymerizations (193 and 193i photoresist polymers) or optimize styrenic monomer systems (248 nm photoresist polymers) to yield polymers with PD as low as 1.05. For 193i lithography, we have used RAFT technology to produce block copolymers comprising of a random "resist" block with composition and size based on conventional dry photoresist materials and a "low surface energy" block The relative block lengths and compositions may be varied to tune solution migration behavior, surface energy, contact angles, and solubility in developer. Directed self assembly is proving to be an interesting and innovative method to make 2- and even 3-dimensional periodic, uniform patterns. Two keys to acceptable performance of directed self assembly from block copolymers are the uniformity and the purity of the materials will be discussed.

  4. Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization

    PubMed Central

    Wang, Wei; Lester, John M.; Amorosa, Anthony E.; Chance, Deborah L.; Mossine, Valeri V.; Mawhinney, Thomas P.

    2015-01-01

    Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of β-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal β-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (≤1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired. PMID:26132587

  5. Control of polymerization shrinkage and stress in nanogel-modified monomer and composite materials

    PubMed Central

    Moraes, Rafael R.; Garcia, Jeffrey W.; Barros, Matthew D.; Lewis, Steven H.; Pfeifer, Carmem S.; Liu, JianCheng; Stansbury, Jeffrey W.

    2011-01-01

    Objectives This study demonstrates the effects of nano-scale prepolymer particles as additives to model dental monomer and composite formulations. Methods Discrete nanogel particles were prepared by solution photopolymerization of isobornyl methacrylate and urethane dimethacrylate in the presence of a chain transfer agent, which also provided a means to attach reactive groups to the prepolymer. Nanogel was added to triethylene glycol dimethacrylate (TEGDMA) in increments between 5 and 40 wt% with resin viscosity, reaction kinetics, shrinkage, mechanical properties, stress and optical properties evaluated. Maximum loading of barium glass filler was determined as a function of nanogel content and composites with varied nanogel content but uniform filler loading were compared in terms of consistency, conversion, shrinkage and mechanical properties. Results High conversion, high molecular weight internally crosslinked and cyclized nanogel prepolymer was efficiently prepared and redispersed into TEGDMA with an exponential rise in viscosity accompanying nanogel content. Nanogel addition at any level produced no deleterious effects on reaction kinetics, conversion or mechanical properties, as long as reactive nanogels were used. A reduction in polymerization shrinkage and stress was achieved in proportion to nanogel content. Even at high nanogel concentrations, the maximum loading of glass filler was only marginally reduced relative to the control and high strength composite materials with low shrinkage were obtained. Significance The use of reactive nanogels offers a versatile platform from which resin and composite handling properties can be adjusted while the polymerization shrinkage and stress development that challenge the adhesive bonding of dental restoratives are controllably reduced. PMID:21388669

  6. Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization.

    PubMed

    Wang, Wei; Lester, John M; Amorosa, Anthony E; Chance, Deborah L; Mossine, Valeri V; Mawhinney, Thomas P

    2015-01-01

    Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of β-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal β-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (≤1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired. PMID:26132587

  7. Study of mass loss of spacecraft polymeric thermal control coatings under electron and proton radiations

    NASA Astrophysics Data System (ADS)

    Khasanshin, Rashid; Novikov, Lev; Galygin, Alexander

    Polymeric composites have a number of properties that give a possibility to apply them as spacecraft external coatings. In space environment, however, such materials become one of the main sources of volatile products that form the outer spacecraft atmosphere and are able to con-dense on contamination-sensitive surfaces of onboard equipment. Thermal control coatings oc-cupy a considerable part of a satellite surface and are mostly subjected to ionizing radiations ac-companying by outgassing. The main stages of the process are the following: formation of vola-tile radiolysis products, diffusion of the products to free material surface, and desorption. Radia-tion-induced destruction and outgassing of material increase its permeability and accelerate mi-gration processes in it. Experimental data of effect of radiation on mass loss of polymeric composites used as thermal control coatings was analyzed and interpreted in the work. As a particular case, it was shown that mass loss of a polymeric composite irradiated by protons is greater than by electrons if energies and flux densities of the particles are the same. It can be explained that volatile products, in the first case, generate within a thin near-surface layer of material which permeability increases together with the absorbed dose, and quickly escape in vacuum. In the second case, a bulk of volatile products emerges far enough from the free surface of material which permeability increases slower as compared with proton radiation. Therefore, migration time of volatile products to the free surface grows and quantity of chemical reactions which they are involved in increases. To analyze and interpret experimental data, a mathematical model describing mass loss of polymeric composites subject to its growth of permeability under radiation is proposed. Based upon analysis of experiments and numerical simulation results, thresholds of fluen-cies and flux densities of electron and proton were determined. Exceeding these

  8. Cationic RAFT polymerization using ppm concentrations of organic acid.

    PubMed

    Uchiyama, Mineto; Satoh, Kotaro; Kamigaito, Masami

    2015-02-01

    A metal-free, cationic, reversible addition-fragmentation chain-transfer (RAFT) polymerization was proposed and realized. A series of thiocarbonylthio compounds were used in the presence of a small amount of triflic acid for isobutyl vinyl ether to give polymers with controlled molecular weight of up to 1×10(5) and narrow molecular-weight distributions (Mw /Mn <1.1). This "living" or controlled cationic polymerization is applicable to various electron-rich monomers including vinyl ethers, p-methoxystyrene, and even p-hydroxystyrene that possesses an unprotected phenol group. A transformation from cationic to radical RAFT polymerization enables the synthesis of block copolymers between cationically and radically polymerizable monomers, such as vinyl ether and vinyl acetate or methyl acrylate. PMID:25511364

  9. Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

    PubMed Central

    Jee, Elizabeth; Bánsági, Tamás

    2016-01-01

    Abstract Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease‐catalyzed hydrolysis of urea was used to trigger the base‐catalyzed Michael addition of a water‐soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min−1). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel. PMID:26732469

  10. The physicodynamic properties of mucoadhesive polymeric films developed as female controlled drug delivery system.

    PubMed

    Yoo, Jin-Wook; Dharmala, Kiran; Lee, Chi H

    2006-02-17

    To develop an efficient female controlled drug delivery system (FcDDS) against sexually transmitted diseases (STDs), the polymeric films containing sodium dodecyl sulfate (SDS) were prepared with various compositions of Carbopol 934P, hydroxypropyl methylcellulose (HPMC) and polyethylene glycol (PEG). The physicochemical properties of mucoadhesive polymeric films, such as tensile strength, contact angle, swelling ratio and erosion rate in a vaginal fluid stimulant (VFS), were characterized. In addition, the drug release profile of SDS from the films and mucosal residence time were evaluated using a simulated dynamic vaginal system. It was demonstrated that the films made of Carbopol, HPMC and PEG were colorless, thin and soft and had proper physicodynamic properties for FcDDS. An increase in Carbopol content elevated tensile strength and swelling ratio but decreased the contact angle, erosion rate and the SDS release rate from the films. The films containing 0.25% (w/v) PEG as well as 0.75% (w/v) of combining Carbopol and HPMC remained on the vaginal tissue for up to 6h. The films containing the ratio of Carbopol:HPMC:PEG=1.5:1.5:1 and 1:2:1 seem to be optimal compositions for FcDDS, as they showed good peelability, relatively high swelling index and moderate tensile strength, and achieved the target release rate of SDS for 6h. PMID:16376036

  11. Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

    PubMed Central

    Jee, Elizabeth; Bánsági, Tamás

    2016-01-01

    Abstract Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease‐catalyzed hydrolysis of urea was used to trigger the base‐catalyzed Michael addition of a water‐soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min−1). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel.

  12. Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction.

    PubMed

    Jee, Elizabeth; Bánsági, Tamás; Taylor, Annette F; Pojman, John A

    2016-02-01

    Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease-catalyzed hydrolysis of urea was used to trigger the base-catalyzed Michael addition of a water-soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min(-1)). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel. PMID:26732469

  13. Non-polymeric coatings to control drug release from metallic coronary stents

    NASA Astrophysics Data System (ADS)

    Gupta, Celia Edith Macias

    Percutaneous transluminal coronary angiography (PTCA) is a procedure used to re-open narrowed coronary arteries. During PTCA, a coronary stent is expanded inside a diseased vessel and serves as a scaffold to keep the artery open. The major drawback of stenting is restenosis---a re-narrowing of the vessel resulting from the hyperproliferation of smooth muscle cells. Drug eluting stents (DES) reduce the rate of restenosis compared to bare metal stents. Paclitaxel (PAT) is commonly used in DES for its ability to prevent restenosis. However, DES have been associated with thrombosis due to the polymer carrier that controls drug delivery. Therefore, there is a need to change the drug delivery mechanisms to eliminate the need of polymers. The goal of this dissertation is to develop a novel polymer-free drug eluting stent that controls drug release using nanoscale metal coatings. The coating was designed to release PAT as the metal slowly degrades in biological conditions. Once all the Paclitaxel has eluted from the surface, the coating will continue to degrade until the final result is a bare metal stent. The results of this study include a novel non-polymeric drug delivery system using nanoscale coatings that release Paclitaxel at a rate similar to commercial stents, as well as the biocompatibility and efficacy of these coatings. The non-polymeric drug delivery system described here achieved a Paclitaxel release profile equivalent to clinically available Paclitaxel-eluting stents and effectively inhibits smooth muscle cell proliferation, thereby completely eliminating the need for polymers to control drug release from coronary stents.

  14. Novel Diblock Copolymer-Grafted Multiwalled Carbon Nanotubes via a combination of Living and Controlled/Living Surface Polymerizations

    SciTech Connect

    Priftis, Dimitrios; Sakellariou, Georgios; Mays, Jimmy; Hadjichristidis, Nikos

    2010-01-01

    Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The OH-end groups were transformed to isopropylbromide groups by reaction with 2-bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2-dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs.

  15. Comparison of Perioperative Outcomes for Epidural versus Intravenous Patient-Controlled Analgesia after Radical Cystectomy

    PubMed Central

    Winer, Andrew G.; Sfakianos, John P.; Puttanniah, Vinay G.; Bochner, Bernard H.

    2016-01-01

    Background and Objectives Use of patient-controlled epidural analgesia after various operations has been associated with earlier return of bowel function and thus decrease the length of stay (LOS). The primary aim of this study was to compare LOS after radical cystectomy between patients who received epidural analgesia versus those who received intravenous patient controlled analgesia. Our secondary analysis included the assessment of other metrics such as total opioid requirements, pain scores, return of bowel function and complication rates between the two groups. Methods We conducted a retrospective review using the electronic medical records of 308 patients who underwent radical cystectomies at Memorial Sloan Kettering between 2006 and 2011. We aimed to understand if epidural analgesia was associated with a reduced length of stay compared to patient controlled intravenous opioid analgesia. We also aimed to identify performance improvements as a function of epidural analgesia status using various metrics such as pain management, bowel function return, and complication rates. We used both univariate and multivariable analyses to identify if epidural analgesia was associated with meaningful differences in the aforementioned metrics. Results Median age at radical cystectomy, body mass index, sex, ASA score, and T stage were similar for both groups. For our primary objective of LOS, we found no significant difference between the two cohorts (8 vs 7 days, p=0.2). Analysis of our secondary outcome measures revealed that epidural analgesia use was associated with less total opioid requirement for the first three post-operative days (p=0.0001). Additionally, epidural analgesia was found to be associated with improved post-operative pain scores compared to intravenous patient-controlled analgesia on post-operative days 1 (p=0.0001) and 2 (p=0.004), and there was a slight improvement on post-operative day 3, but this was not significant (p=0.77). In contrast, we found no

  16. Regulation of actin polymerization by tropomodulin-3 controls megakaryocyte actin organization and platelet biogenesis.

    PubMed

    Sui, Zhenhua; Nowak, Roberta B; Sanada, Chad; Halene, Stephanie; Krause, Diane S; Fowler, Velia M

    2015-07-23

    The actin cytoskeleton is important for platelet biogenesis. Tropomodulin-3 (Tmod3), the only Tmod isoform detected in platelets and megakaryocytes (MKs), caps actin filament (F-actin) pointed ends and binds tropomyosins (TMs), regulating actin polymerization and stability. To determine the function of Tmod3 in platelet biogenesis, we studied Tmod3(-/-) embryos, which are embryonic lethal by E18.5. Tmod3(-/-) embryos often show hemorrhaging at E14.5 with fewer and larger platelets, indicating impaired platelet biogenesis. MK numbers are moderately increased in Tmod3(-/-) fetal livers, with only a slight increase in the 8N population, suggesting that MK differentiation is not significantly affected. However, Tmod3(-/-) MKs fail to develop a normal demarcation membrane system (DMS), and cytoplasmic organelle distribution is abnormal. Moreover, cultured Tmod3(-/-) MKs exhibit impaired proplatelet formation with a wide range of proplatelet bud sizes, including abnormally large proplatelet buds containing incorrect numbers of von Willebrand factor-positive granules. Tmod3(-/-) MKs exhibit F-actin disturbances, and Tmod3(-/-) MKs spreading on collagen fail to polymerize F-actin into actomyosin contractile bundles. Tmod3 associates with TM4 and the F-actin cytoskeleton in wild-type MKs, and confocal microscopy reveals that Tmod3, TM4, and F-actin partially colocalize near the membrane of proplatelet buds. In contrast, the abnormally large proplatelets from Tmod3(-/-) MKs show increased F-actin and redistribution of F-actin and TM4 from the cortex to the cytoplasm, but normal microtubule coil organization. We conclude that F-actin capping by Tmod3 regulates F-actin organization in mouse fetal liver-derived MKs, thereby controlling MK cytoplasmic morphogenesis, including DMS formation and organelle distribution, as well as proplatelet formation and sizing. PMID:25964668

  17. Control of molecular weight of polystyrene using the reverse iodine transfer polymerization (RITP)-emulsion technique.

    PubMed

    Oh, Hyeong Geun; Shin, Hongcheol; Jung, Hyejun; Lee, Byung Hyung; Choe, Soonja

    2011-01-15

    The RITP-emulsion polymerization of styrene in the presence of molecular iodine has been successfully performed using potassium persulfate (KPS) as an initiator and 1-hexadecanesulfonate as an emulsifier under argon atmosphere at 80°C for 7 hrs in the absence of light. The effects of the iodine concentration, molar ratio between KPS and iodine, and solid contents on the molecular weight of polystyrene (PS) were studied. As the iodine concentration increased from 0.05 to 0.504 mmol under the fixed [KPS]/[I(2)] ratio at 4.5, the weight-average molecular weight of PS substantially decreased from 126,120 to 35,690 g/mol, the conversion increased from 85.0% to 95.2%, and the weight-average particle diameter decreased from 159 to 103 nm. In addition, as the ratio of [KPS]/[I(2)] increased from 0.5 to 6.0 at the fixed [I(2)] of 0.504 mmol, the weight-average molecular weight of PS decreased from 72,170 to 30,640 g/mol with high conversion between 81.7% and 96.5%. Moreover, when the styrene solid content increased from 10 to 40 wt.% at the fixed [KPS]/[I(2)] ratio of 4.5, the weight-average molecular weight of PS varied between 33,500 and 37,200 g/mol, the conversion varied between 94.9% and 89.7% and the weight-average diameter varied from 122 to 205 nm. Thus, the control of molecular weight of PS less than 100,000g/mol with high conversion (95%) and particle stability of up to 40 wt.% solid content were easily achieved through the usage of iodine with suitable ratio of [KPS]/[I(2)] in the RITP-emulsion polymerization technique, which is of great industrial importance. PMID:20950818

  18. Formation of size-controlled, denaturation-resistant lipid nanodiscs by an amphiphilic self-polymerizing peptide.

    PubMed

    Kondo, Hiroaki; Ikeda, Keisuke; Nakano, Minoru

    2016-10-01

    Nanodiscs are discoidal particles with a planar phospholipid bilayer enwrapped by proteins such as apolipoprotein A-I. Nanodiscs have been widely used for analyzing structures and functions of membrane proteins by dispersing them in solution. They are expected to be used as drug carriers and therapeutic agents. Amphiphilic peptides are known to form nanodiscs. However, the lipid-peptide nanodiscs are relatively unstable in solution, making them unsuitable for many applications. Here, we report the synthesis of an amphiphilic self-polymerizing peptide termed ASPP1, which polymerizes by intermolecular native chemical ligation reactions. ASPP1 spontaneously formed nanodiscs when added to phospholipid vesicles without using detergents. The diameter of the planar lipid bilayer in the nanodiscs was controlled by the lipid:peptide molar ratio. ASPP1-nanodiscs exhibited greater stability at high temperatures or in the presence of urea than nanodiscs formed by the non-polymerizing amphiphilic peptide or apolipoprotein A-I. Average and maximal degrees of ASPP1 polymerization were 2.4 and 12, respectively. Self-polymerization of the peptide appears to be responsible for stabilization of the nanodiscs. Our results open a new avenue for the development of nanodisc technology. PMID:27393815

  19. Evaluation of microwave assisted grafted sago starch as controlled release polymeric carrier.

    PubMed

    Singh, Akhilesh Vikram; Nath, Lila Kanta

    2013-09-01

    In the present investigation an attempt has been made to develop a new co-polymeric material for controlled release tablet formulations. The acrylamide grafting was successfully performed on the backbone of sago starch. The modified starch was tested for acute toxicity and drug-excipient compatibility study. The grafted material was used in making of controlled release tablets of lamivudine. The formulations were evaluated for physical characteristics such as hardness, friability, %drug content and weight variations. The in vitro release study showed that the optimized formulation exhibited highest correlation (R) value in case of Higuchi model and the release mechanism of the optimized formulation predominantly exhibited combination of diffusion and erosion process. There was a significant difference in the pharmacokinetic parameters (T(max), C(max), AUC, V(d), T(1/2) and MDT) of the optimized formulation as compared to the marketed conventional tablet Lamivir(®) was observed. The pharmacokinetics parameters were showed controlled pattern and better bioavailability. The optimized formulation exhibited good stability and release profile at the accelerated stability conditions. PMID:23707750

  20. Control of Interfacial Properties of Al2O3/Ge Gate Stack Structure Using Radical Nitridation Technique

    NASA Astrophysics Data System (ADS)

    Kato, Kimihiko; Kyogoku, Shinya; Sakashita, Mitsuo; Takeuchi, Wakana; Kondo, Hiroki; Takeuchi, Shotaro; Nakatsuka, Osamu; Zaima, Shigeaki

    2011-10-01

    We have investigated the control of the interfacial properties of Al2O3/Ge gate stack structures by the radical nitridation technique. In the Al2O3/Ge structures formed by the atomic layer deposition method, the interface state density increases with the deposition temperature due to the decrease in the thickness of the Ge oxide interlayer. On the other hand, the hysteresis width of the capacitance-voltage (C-V) characteristics decreases with increasing deposition temperature, which indicates a decrease in the oxide trap density near the interface. We also investigated the control of the interfacial structure by the radical nitridation of Al2O3/Ge to form an interfacial structure after the deposition of a high-k dielectric layer. The results of X-ray photoelectron spectroscopy reveal that an Al2O3/Ge3N4/GeO2/Ge stack structure is formed after the radical nitridation owing to the minimal oxygen diffusion into the Al2O3/Ge interface. Furthermore, the interfacial mixing is suppressed after radical nitridation at less than 300 °C. As a result, we can decrease the interface state density of the Al2O3/Ge sample after the radical nitridation by more than one order of magnitude compared with that without radical nitridation.

  1. Controlling the thickness of hollow polymeric microspheres prepared by electrohydrodynamic atomization.

    PubMed

    Chang, Ming-Wei; Stride, Eleanor; Edirisinghe, Mohan

    2010-08-01

    In this study, the ability to control the shell thickness of hollow polymeric microspheres prepared using electrohydrodynamic processing at ambient temperature was investigated. Polymethylsilsesquioxane (PMSQ) was used as a model material for the microsphere shell encapsulating a core of liquid perfluorohexane (PFH). The microspheres were characterized by Fourier transform infrared spectroscopy and optical and electron microscopy, and the effects of the processing parameters (flow-rate ratio, polymer concentration and applied voltage) on the mean microsphere diameter (D) and shell thickness (t) were determined. It was found that the mean diameters of the hollow microspheres could be controlled in the range from 310 to 1000 nm while the corresponding mean shell thickness varied from 40 to 95 nm. The results indicate that the ratio D : t varied with polymer concentration, with the largest value of approximately 10 achieved with a solution containing 18 wt% of the polymer, while the smallest value (6.6) was obtained at 36 wt%. For polymer concentrations above 63 wt%, hollow microspheres could not be generated, but instead PMSQ fibres encapsulating PFH liquid were obtained. PMID:20519216

  2. Controlled nanopatterning of a polymerized ionic liquid in a strong electric field

    DOE PAGESBeta

    Bocharova, Vera; Agapov, Alexander L.; Tselev, Alexander; Kumar, Rajeev; Berdzinski, Stefan; Strehmel, Veronika; Kisliuk, Alexander; Kravchenko, Ivan I.; Sumpter, Bobby G.; Sokolov, Alexei P.; et al

    2014-12-17

    Nanolithography has become a driving force in advancements of the modern day's electronics, allowing for miniaturization of devices and a steady increase of the calculation, power, and storage densities. Among various nanofabrication approaches, scanning probe techniques, including atomic force microscopy (AFM), are versatile tools for creating nanoscale patterns utilizing a range of physical stimuli such as force, heat, or electric field confined to the nanoscale. In this study, the potential of using the electric field localized at the apex of an AFM tip to induce and control changes in the mechanical properties of an ion containing polymer—a polymerized ionic liquidmore » (PolyIL)—on a very localized scale is explored. In particular, it is demonstrated that by means of AFM, one can form topographical features on the surface of PolyIL-based thin films with a significantly lower electric potential and power consumption as compared to nonconductive polymer materials. Lastly,, by tuning the applied voltage and ambient air humidity, control over dimensions of the formed structures is reproducibly achieved.« less

  3. Controlled nanopatterning of a polymerized ionic liquid in a strong electric field

    SciTech Connect

    Bocharova, Vera; Agapov, Alexander L.; Tselev, Alexander; Kumar, Rajeev; Berdzinski, Stefan; Strehmel, Veronika; Kisliuk, Alexander; Kravchenko, Ivan I.; Sumpter, Bobby G.; Sokolov, Alexei P.; Kalinin, Sergei V.; Strelcov, Evgheni; Collins, Liam

    2014-12-17

    Nanolithography has become a driving force in advancements of the modern day's electronics, allowing for miniaturization of devices and a steady increase of the calculation, power, and storage densities. Among various nanofabrication approaches, scanning probe techniques, including atomic force microscopy (AFM), are versatile tools for creating nanoscale patterns utilizing a range of physical stimuli such as force, heat, or electric field confined to the nanoscale. In this study, the potential of using the electric field localized at the apex of an AFM tip to induce and control changes in the mechanical properties of an ion containing polymer—a polymerized ionic liquid (PolyIL)—on a very localized scale is explored. In particular, it is demonstrated that by means of AFM, one can form topographical features on the surface of PolyIL-based thin films with a significantly lower electric potential and power consumption as compared to nonconductive polymer materials. Lastly,, by tuning the applied voltage and ambient air humidity, control over dimensions of the formed structures is reproducibly achieved.

  4. Controlling the thickness of hollow polymeric microspheres prepared by electrohydrodynamic atomization

    PubMed Central

    Chang, Ming-Wei; Stride, Eleanor; Edirisinghe, Mohan

    2010-01-01

    In this study, the ability to control the shell thickness of hollow polymeric microspheres prepared using electrohydrodynamic processing at ambient temperature was investigated. Polymethylsilsesquioxane (PMSQ) was used as a model material for the microsphere shell encapsulating a core of liquid perfluorohexane (PFH). The microspheres were characterized by Fourier transform infrared spectroscopy and optical and electron microscopy, and the effects of the processing parameters (flow-rate ratio, polymer concentration and applied voltage) on the mean microsphere diameter (D) and shell thickness (t) were determined. It was found that the mean diameters of the hollow microspheres could be controlled in the range from 310 to 1000 nm while the corresponding mean shell thickness varied from 40 to 95 nm. The results indicate that the ratio D : t varied with polymer concentration, with the largest value of approximately 10 achieved with a solution containing 18 wt% of the polymer, while the smallest value (6.6) was obtained at 36 wt%. For polymer concentrations above 63 wt%, hollow microspheres could not be generated, but instead PMSQ fibres encapsulating PFH liquid were obtained. PMID:20519216

  5. Microtransfer printing of metal ink patterns onto plastic substrates utilizing an adhesion-controlled polymeric donor layer

    NASA Astrophysics Data System (ADS)

    Park, Ji-Sub; Choi, Jun-Chan; Park, Min-Kyu; Bae, Jeong Min; Bae, Jin-Hyuk; Kim, Hak-Rin

    2016-06-01

    We propose a method for transfer-printed electrode patterns onto flexible/plastic substrates, specifically intended for metal ink that requires a high sintering temperature. Typically, metal-ink-based electrodes cannot be picked up for microtransfer printing because the adhesion between the electrodes and the donor substrate greatly increases after the sintering process due to the binding materials. We introduced a polymeric donor layer between the printed electrodes and the donor substrate and effectively reduced the adhesion between the Ag pattern and the polymeric donor layer by controlling the interfacial contact area. After completing a wet-etching process for the polymeric donor layer, we obtained Ag patterns supported on the fine polymeric anchor structures; the Ag patterns could be picked up onto the stamp surface even after the sintering process by utilizing the viscoelastic properties of the elastomeric stamp with a pick-up velocity control. The proposed method enables highly conductive metal-ink-based electrode patterns to be applied on thermally weak plastic substrates via an all-solution process. Metal electrodes transferred onto a film showed superior electrical and mechanical stability under the bending stress test required for use in printed flexible electronics.

  6. Simulation and Experiments To Identify Factors Allowing Synthetic Control of Structural Features of Polymeric Nanoparticles.

    PubMed

    Swope, William C; Rice, Julia E; Piunova, Victoria A; Carr, Amber C; Miller, Robert D; Sly, Joseph

    2016-08-01

    To develop a detailed picture of the microscopic structure of gelcore star polymers and to elucidate parameters of the synthetic process that might be exploited to control this structure, simulations of their synthesis were performed that were based on a particular synthetic approach. A range of results was observed from gelation at high reactant concentrations to the formation of various sizes and compositions of star polymers. Contrary to the prevailing experimental viewpoint, the simulations always suggest the production of a broad distribution of star polymer sizes. However, the GPC traces computed from simulation results are in good qualitative agreement with experiment. Topologically, the gelcore star polymers produced by simulation are not compact but, rather, sparse blobs loosely connected by filaments of linker when modeled in a good solvent. This is reflected in scaling relationships that relate polymer size (e.g., radius of gyration) and degree of polymerization. The arm-core composition is observed to be stoichiometric, strongly reflecting relative reactant concentrations during the synthesis. Reactions within star polymers that result in greater intramolecular cross-linking compete with those between star polymers that result in the production of larger star polymers from the joining of smaller ones. The balance in this competition can be controlled through the overall reactant concentration to limit and control resulting star polymer size. Therefore, the mean size, as well as the mean number of arms, can be controlled during synthesis by careful tuning of the overall ratio of the arm and linker reactant concentrations and the total reactant concentration. PMID:27385087

  7. SYNTHESIS AND IN VITRO CHARACTERIZATION OF HYDROXYPROPYL METHYLCELLULOSE-GRAFT-POLY (ACRYLIC ACID/2-ACRYLAMIDO-2-METHYL-1-PROPANESULFONIC ACID) POLYMERIC NETWORK FOR CONTROLLED RELEASE OF CAPTOPRIL.

    PubMed

    Furqan Muhammad, Iqbal; Mahmood, Ahmad; Aysha, Rashid

    2016-01-01

    A super-absorbent hydrogel was developed by crosslinking of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and acrylic acid with hydroxypropyl methylcellulose (HPMC) for controlled release drug delivery of captopril, a well known antihypertensive drug. Acrylic acid and AMPS were polymerized and crosslinked with HPMC by free radical polymerization, a widely used chemical crosslinking method. N,N'-methylenebisacrylamide (MBA) and potassium persulfate (KPS) were added as cross-linker and initiator, respectively. The hydrogel formulation was loaded with captopril (as model drug). The concentration of captopril was monitored at 205 nm using UV spectrophotometer. Equilibrium swelling ratio was determined at pH 2, 4.5 and 7.4 to evaluate the pH responsiveness of the formed hydrogel. The super-absorbent hydrogels were evaluated by FTIR, SEM, XRD, and thermal analysis (DSC and TGA). The formation of new copolymeric network was determined by FTIR, XRD, TGA and DSC analysis. The hydrogel formulations with acrylic acid and AMPS ratio of 4: 1 and lower amounts of crosslinker had shown maximum swelling. Moreover, higher release rate of captopril was observed at pH 7.4 than at pH 2, because of more swelling capacity of copolymer with increasing pH of the aqueous medium. The present research work confirms the development of a stable hydrogel comprising of HPMC with acrylic acid and AMPS. The prepared hydrogels exhibited pH sensitive behav-ior. This superabsorbent composite prepared could be a successful drug carrier for treating hypertension. PMID:27008813

  8. Supercritical fluid extraction-liquid chromatography method development for a polymeric controlled-release drug formulation.

    PubMed

    Roston, D A; Sun, J J; Collins, P W; Perkins, W E; Tremont, S J

    1995-11-01

    We have recently been involved in the development of a method for assaying the active component in a controlled-release drug formulation, which is composed of a drug substance covalently bonded to polymer matrix. The drug substance in the formulation is the active enantiomer of misoprostol, a synthetic analog of natural prostaglandins and the active ingredient in Cytotec. Our method development consisted of a systematic evaluation of dynamic, off-line supercritical fluid extraction (SFE) as sample preparation for the formulation assay. Extracts were analyzed with normal phase and reversed-phase HPLC methods. The reversed-phase system utilized postcolumn reaction to provide selective detection of the extracted prostaglandin sample components. Several SFE parameters were investigated to optimize the recovery of the drug substance from the formulation, including sample quantity, extraction cell volume, extraction duration, supercritical carbon dioxide modifier, temperature, pressure, and collection solvent. The SFE experiments were completed with a commercially available multicell extractor. Preliminary validation studies utilized a formulation made with radiolabeled drug to determine the recovery achieved under the optimized SFE conditions and assessed the precision of replicate determinations. Analysis was completed under the optimized conditions to quantitate levels of the active component and related compounds in lots of the experimental polymeric formulation and to determine the total weight per cent extracted. PMID:8788137

  9. Polymer nanostructures synthesized by controlled living polymerization for tumor-targeted drug delivery.

    PubMed

    Wang, Christine E; Stayton, Patrick S; Pun, Suzie H; Convertine, Anthony J

    2015-12-10

    The development of drug delivery systems based on well-defined polymer nanostructures could lead to significant improvements in the treatment of cancer. The design of these therapeutic nanosystems must account for numerous systemic and circulation obstacles as well as the specific pathophysiology of the tumor. Nanoparticle size and surface charge must also be carefully selected in order to maintain long circulation times, allow tumor penetration, and avoid clearance by the reticuloendothelial system (RES). Targeting ligands such as vitamins, peptides, and antibodies can improve the accumulation of nanoparticle-based therapies in tumor tissue but must be optimized to allow for intratumoral penetration. In this review, we will highlight factors influencing the design of nanoparticle therapies as well as the development of modern controlled "living" polymerization techniques (e.g. ATRP, RAFT, ROMP) that are leading to the creation of sophisticated new polymer architectures with discrete spatially-defined functional modules. These innovative materials (e.g. star polymers, polymer brushes, macrocyclic polymers, and hyperbranched polymers) combine many of the desirable properties of traditional nanoparticle therapies while substantially reducing or eliminating the need for complex formulations. PMID:26342661

  10. Anti-inflammatory drug incorporation into polymeric nano-hybrids for local controlled release.

    PubMed

    Sammartino, G; Marenzi, G; Tammaro, L; Bolognese, A; Calignano, A; Costantino, U; Califano, L; Mastrangelo, F; Tetè, S; Vittoria, V

    2005-01-01

    In this paper we present the formulation, preparation and characterization of new polymeric composite materials containing a nano-hybrid to be used for the controlled molecular delivery of an anti-inflammatory molecule, Diclofenac. The nano-hybrid consists of a layer of double hydroxide of an Mg-Al hydrotalcite type, in which we replaced the chloride anions present in the host galleries with Diclofenac anions by a simple ion-exchange reaction. Different amounts of the hybrid material were incorporated in polycaprolactone and processed as films of 0.15 mm thickness. The composite materials were analyzed by X-ray diffractometry, thermogravimetry and for their mechanical properties, and showed properties even better than those for the pristine polymer. The release process of the anti-inflammatory molecules was very interesting and promising for tuneable drug delivery. It consists of two stages: a first stage, very rapid as a burst in which a small fraction of the drug is released, and of a second stage that is much slower, extending for longer and longer periods. The parameters influencing the drug release were individuated and discussed. PMID:16848988

  11. Radically Open-Dialectical Behavior Therapy for Disorders of Over-Control: Signaling Matters.

    PubMed

    Lynch, Thomas R; Hempel, Roelie J; Dunkley, Christine

    2015-01-01

    Radically Open-Dialectical Behavior Therapy (RO-DBT) is a transdiagnostic treatment designed to address a spectrum of difficult-to-treat disorders sharing similar phenotypic and genotypic features associated with maladaptive over-control-such as anorexia nervosa, chronic depression, and obsessive compulsive personality disorder. Over-control has been linked to social isolation, aloof and distant relationships, cognitive rigidity, high detailedfocused processing, risk aversion, strong needs for structure, inhibited emotional expression, and hyper-perfectionism. While resting on the dialectical underpinnings of standard DBT, the therapeutic strategies, core skills, and theoretical perspectives in RO-DBT often substantially differ. For example, RO-DBT contends that emotional loneliness secondary to low openness and social-signaling deficits represents the core problem of over-control, not emotion dysregulation. RO-DBT also significantly differs from other treatment approaches, most notably by linking the communicative functions of emotional expression to the formation of close social bonds and via skills targeting social-signaling and changing neurophysiological arousal. The aim of this paper is to provide a brief overview of the core theoretical principles and unique treatment strategies underlying RO-DBT. PMID:26160620

  12. Snowballing radical generation leads to ultrahigh molecular weight polymers.

    PubMed

    Laurino, Paola; Hernandez, Hugo F; Bräuer, Judith; Krüger, Kathleen; Grützmacher, Hansjörg; Tauer, Klaus; Seeberger, Peter H

    2012-10-26

    Styrene is the classical monomer obeying zero-one kinetics in radical emulsion polymerization. Accordingly, particles that are less than 100 nm in diameter contain either one or no growing radical(s). We describe a unique photoinitiated polymerization reaction accelerated by snowballing radical generation in a continuous flow reactor. Even in comparison to classical emulsion polymerization, these unprecedented snowballing reactions are rapid and high-yielding, with each particle simultaneously containing more than one growing radical. This is a consequence of photoinitiator incorporation into the nascent polymer backbone and repeated radical generation upon photo-irradiation. PMID:22837041

  13. Polymerization Initiated at the Sidewalls of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Tour, James M.; Hudson, Jared L.

    2011-01-01

    A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

  14. Control of polyaniline deposition on microporous cellulose ester membranes by in situ chemical polymerization.

    PubMed

    Qaiser, Asif A; Hyland, Margaret M; Patterson, Darrell A

    2009-11-12

    Polyaniline (PANI) can be deposited either on the surface or in the bulk of a microporous membrane by various chemical oxidative polymerization techniques. Each technique has distinctive effects on the PANI site and extent of deposition on the base membrane. In the present study, mixed cellulose ester (ME) membranes with tortuous pore morphology were used as base membranes. The chemical oxidative polymerization techniques employed, included polymerization using an in-house-built two-compartment permeation cell. The resultant composite membranes have been characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR-ATR), and electrical conductivity measurements. The results showed that PANI was layered on the pore walls of the membrane using two-compartment permeation cell. Vapor-phase polymerization yielded a surface layer of PANI with little deposition in the bulk. A distorted PANI surface layer was achieved by solution-phase (dip) polymerization. Moreover, asymmetric PANI deposition within the membrane bulk was evidenced using two-compartment permeation cell. Composite membranes synthesized using two-compartment cell showed highest levels of conductivity (approximately 10(-2) S/cm) as compared to the membranes modified by single-step solution-phase polymerization. FTIR-ATR results indicated the extent of PANI coating and its oxidation state which was identified as doped emeraldine PANI, from all the employed techniques. Asymmetric deposition and extent have been explained in terms of the physical and chemical reaction steps involved in the heterogeneous aniline polymerization reactions in the two-compartment cell technique. PMID:19888765

  15. Development and characterization of a novel, antimicrobial, sterile hydrogel dressing for burn wounds: single-step production with gamma irradiation creates silver nanoparticles and radical polymerization.

    PubMed

    Boonkaew, Benjawan; Barber, Philip M; Rengpipat, Sirirat; Supaphol, Pitt; Kempf, Margit; He, Jibao; John, Vijay T; Cuttle, Leila

    2014-10-01

    Patients with burn wounds are susceptible to wound infection and sepsis. This research introduces a novel burn wound dressing that contains silver nanoparticles (SNPs) to treat infection in a 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS-Na(+) ) hydrogel. Silver nitrate was dissolved in AMPS-Na(+) solution and then exposed to gamma irradiation to form SNP-infused hydrogels. The gamma irradiation results in a cross-linked polymeric network of sterile hydrogel dressing and a reduction of silver ions to form SNPs infused in the hydrogel in a one-step process. About 80% of the total silver was released from the hydrogels after 72 h immersion in simulated body fluid solution; therefore, they could be used on wounds for up to 3 days. All the hydrogels were found to be nontoxic to normal human dermal fibroblast cells. The silver-loaded hydrogels had good inhibitory action against Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus. Results from a pilot study on a porcine burn model showed that the 5-mM silver hydrogel was efficient at preventing bacterial colonization of wounds, and the results were comparable to the commercially available silver dressings (Acticoat(TM) , PolyMem Silver(®) ). These results support its use as a potential burn wound dressing. PMID:25079080

  16. Synthesis and optimization of fluorescent poly(N-isopropyl acrylamide)-coated surfaces by atom transfer radical polymerization for cell culture and detachment.

    PubMed

    Cooperstein, Marta A; Bluestein, Blake M; Canavan, Heather E

    2015-01-01

    Although there are many stimulus-responsive polymers, poly(N-isopropyl acrylamide) (pNIPAM) is of special interest due to the phase change it undergoes in a physiologically relevant temperature range that leads to the release of cells and proteins. The nondestructive release of cells opens up a wide range of applications, including the use of pNIPAM for cell sheet and tissue engineering. In this work, pNIPAM surfaces were generated that can be distinguished from the extracellular matrix. A polymerization technique was adapted that was previously used by Mendez, and the existing protocol was optimized for the culture of mammalian cells. The resulting surfaces were characterized with X-ray photoelectron spectroscopy and goniometry. The developed pNIPAM surfaces were further adapted by incorporation of 5-acrylamidofluorescein to generate fluorescent pNIPAM-coated surfaces. Both types of surfaces (fluorescent and nonfluorescent) sustained cellular attachment and produced cellular detachment of ∼90%, and are therefore suitable for the generation of cell sheets for engineered tissues and other purposes. These surfaces will be useful tools for experiments investigating cellular detachment from pNIPAM and the pNIPAM/cell interface. PMID:25708629

  17. The preparation of size-controlled functionalized polymeric nanoparticles in micelles

    NASA Astrophysics Data System (ADS)

    Vakurov, Alexander; Pchelintsev, Nikolay A.; Forde, Jessica; Ó'Fágáin, Ciaran; Gibson, Tim; Millner, Paul

    2009-07-01

    The reverse micellar system of dioctyl-sulfosuccinate (AOT)/octane and toluene have been used as a template for polymerization of acrylamide (AA)/bisacrylamide (BAA)-based functionalized polymeric nanoparticles. Such nanoparticles are typically sized between 20 and 90 nm. They can be synthesized with different functional groups according to the monomers added to the polymerization mixture. In our experiments the nanoparticles carried amino and carboxyl groups following incorporation of allylamine (AAm) or methacrylic acid (MAA) monomers, respectively. The available amine or carboxyl groups can then be used for immobilization of enzymes or other biomolecules. These enzymes, subtilisin, laccase and lipase, were immobilized onto polyAA/BAA/MAA nanoparticles covalently after activating the MAA carboxylic groups with Woodward's K reagent. Non-covalent immobilization via electrostatic interaction was also performed.

  18. Polymerization of a Photocleavable Monomer Using Visible Light.

    PubMed

    Bagheri, Ali; Yeow, Jonathan; Arandiyan, Hamidreza; Xu, Jiangtao; Boyer, Cyrille; Lim, May

    2016-06-01

    The polymerization of the photocleavable monomer, o-nitrobenzyl methacrylate (NBMA), is investigated using photoinduced electron/energy transfer reversible addition-fragmentation chain transfer polymerization. The polymerizations under visible red (λ max = 635 nm, 0.7 mW cm(-2) ) and yellow (λ max = 560 nm, 9.7 mW cm(-2) ) light are performed and demonstrate rational evidence of a controlled/living radical polymerization process. Well-defined poly(o-nitrobenzyl methacrylate) (PNBMA) homopolymers with good control over the molecular weight and polymer dispersity are successfully synthesized by varying the irradiation time and/or targeted degree of polymerization. Chain extension of a poly(oligo(ethylene glycol) methyl ether methacrylate) macro-chain transfer agent with NBMA is carried out to fabricate photocleavable amphiphilic block copolymers (BCP). Finally, these self-assembled BCP rapidly dissemble under UV light suggesting the photoresponsive character of NBMA is not altered during the polymerization under yellow or red light. Such photoresponsive polymers can be potentially used for the remote-controlled delivery of therapeutic compounds. PMID:27121222

  19. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

    PubMed Central

    Mark, Stefan; Wadepohl, Hubert

    2016-01-01

    Summary A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. PMID:27559387

  20. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand-metal interactions.

    PubMed

    Mark, Stefan; Wadepohl, Hubert; Enders, Markus

    2016-01-01

    A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. PMID:27559387

  1. Control of asymmetry in the radical addition approach to chiral amine synthesis.

    PubMed

    Friestad, Gregory K

    2014-01-01

    The state-of-the-science in asymmetric free radical additions to imino compounds is presented, beginning with an overview of methods involving stereocontrol by various chiral auxiliary approaches. Chiral N-acylhydrazones are discussed with respect to their use as radical acceptors for Mn-mediated intermolecular additions, from design to scope surveys to applications to biologically active targets. A variety of aldehydes and ketones serve as viable precursors for the chiral hydrazones, and a variety of alkyl iodides may be employed as radical precursors, as discussed in a critical review of the functional group compatibility of the reaction. Applications to amino acid and alkaloid synthesis are presented to illustrate the synthetic potential of these versatile stereocontrolled carbon-carbon bond construction reactions. Asymmetric catalysis is discussed, from seminal work on the stereocontrol of radical addition to imino compounds by non-covalent interactions with stoichiometric amounts of catalysts, to more recent examples demonstrating catalyst turnover. PMID:24085561

  2. Control of Asymmetry in the Radical Addition Approach to Chiral Amine Synthesis

    PubMed Central

    Friestad, Gregory K.

    2014-01-01

    The state-of-the-science in asymmetric free radical additions to imino compounds is presented, beginning with an overview of methods involving stereocontrol by various chiral auxiliary approaches. Chiral N-acylhydrazones are discussed with respect to their use as radical acceptors for Mn-mediated intermolecular additions, from design to scope surveys to applications to biologically active targets. A variety of aldehydes and ketones serve as viable precursors for the chiral hydrazones, and a variety of alkyl iodides may be employed as radical precursors, as discussed in a critical review of the functional group compatibility of the reaction. Applications to amino acid and alkaloid synthesis are presented to illustrate the synthetic potential of these versatile stereocontrolled carbon–carbon bond construction reactions. Asymmetric catalysis is discussed, from seminal work on the stereocontrol of radical addition to imino compounds by non-covalent interactions with stoichiometric amounts of catalysts, to more recent examples demonstrating catalyst turnover. PMID:24085561

  3. Characterization of pH-Responsive Hydrogels of Poly(Itaconic acid-g-Ethylene Glycol) Prepared by UV-Initiated Free Radical Polymerization as Biomaterials for Oral Delivery of Bioactive Agents

    PubMed Central

    Betancourt, Tania; Pardo, Juan; Soo, Ken; Peppas, Nicholas A.

    2009-01-01

    Effective oral delivery of proteins is impeded by steep pH gradients and proteolytic enzymes in the gastrointestinal tract, as well as low absorption of the proteins into the bloodstream due to their size, charge or solubility. In the present work, pH-responsive complexation hydrogels of poly(itaconic acid) with poly(ethylene glycol) grafts were synthesized for applications in oral drug delivery. These hydrogels were expected to be in collapsed configuration at low pH due to hydrogen bonding between poly(itaconic acid) carboxyl groups and poly(ethylene glycol), and to swell with increasing pH because of charge repulsion between deprotonated carboxylic acid groups. Hydrogels were prepared by UV-initiated free radical polymerization using tetraethylene glycol as the crosslinking agent and Irgacure® 2959 as the initiator. The effect of monomer ratios, crosslinking ratio and solvent amount on the properties of the hydrogels were investigated. The composition of the hydrogels was confirmed by FTIR. Equilibrium swelling studies in the pH range of 1.2 to 7 revealed that the extent of swelling increased with increasing pH up to a pH of about 6, when no further carboxylic acid deprotonation occurred. Studies in Caco-2 colorectal carcinoma cells confirmed the cytocompatibility of these materials at concentrations of up to 5 mg/ml. PMID:19536838

  4. Polymerization topochemistry of cellulose nanocrystals: a function of surface dehydration control.

    PubMed

    Tian, Chen; Fu, Shiyu; Habibi, Youssef; Lucia, Lucian A

    2014-12-01

    The activation (dehydration) of cellulose nanocrystals (CNCs) toward surface "brush" polymerization is accomplished either by freeze drying or solvent exchange. However, the question of which one of these protocols to choose over the other is generally open-ended. The current study attempts to shed light on this question by installing a standard polymer, polycaprolactone (PCL), onto the surface of both freeze-dried and solvent-exchanged CNCs by ring-opening polymerization (ROP) and examining the differences in polymerization and final product properties. The work is the first to demonstrate that the efficiency of surface polymerization and final product properties are in fact influenced by the protocols. The differences between the two sample PCL-grafted CNCs were investigated by X-ray photoelectron spectroscopy (XPS), elemental analysis, gel permeation chromatography (GPC), and contact-angle measurements. The freeze-dried samples had a significantly reduced PCL surface density. The crystallinity of the solvent-exchanged PCL-grafted CNCs (SECNC-g-PCL), however, was lower than that of either pure CNCs or freeze-dried PCL-grafted CNCs (FDCNC-g-PCL). It was determined that solvent exchange sufficiently modified the CNC surface to provide enhanced reactivity, an effect that was not as apparent for FDCNC-g-PCL. The solvent-exchanged CNCs tended to have more porous, nanotextured surfaces that were tended to be more responsive toward brush polymerization. In addition to the physical dissimilarities in surface morphology and surface accessibility contributing to topochemical differences between the two species, it was also found that the dispersibility, aggregation, and thermal stability were different. PMID:25387043

  5. In vitro, in vivo and pharmacokinetic assessment of amikacin sulphate laden polymeric nanoparticles meant for controlled ocular drug delivery

    NASA Astrophysics Data System (ADS)

    Sharma, Upendra Kumar; Verma, Amita; Prajapati, Sunil Kuamr; Pandey, Himanshu; Pandey, Avinash C.

    2015-02-01

    The rationale of current exploration was to formulate positively charged amikacin-loaded polymeric nanoparticles providing a controlled release attribute. Amikacin sulphate-loaded nanoparticles were prepared by w/o/w emulsification solvent evaporation approach succeeded by high-pressure homogenization. Two bioadhesive positively charged polymers, Eudragit® RS 100 and Eudragit® RL 100, were used in the blend, with variable ratios of drug and polymer. The formulations were assessed in terms of particle size and zeta potential. Thermal gravimetric analysis was brought out on the samples of drug, polymer and drug polymer complex. Drug loading and release attributes of the nanoparticles were scrutinized and antimicrobial activity in contrast to Staphylococcus aureus was appraised. Ocular irritation test, in vivo ocular retention study, in vivo release profile (permeation study) and in vivo antibacterial activity of polymeric nanosuspensions were executed. No rupture consequence but a lengthened drug release was contemplated from all formulations. Amikacin sulphate release from the polymeric nanoparticles reflected a better fit with Korsmeyer-Peppas model. In the course of the antibacterial activity of nanoparticles against S. aureus, formulation AE1 displays the most prominent inhibitory effect as compared with marketed formulation of amikacin sulphate.

  6. Size controlled synthesis of sub-100 nm monodisperse poly(methylmethacrylate) nanoparticles using surfactant-free emulsion polymerization.

    PubMed

    Camli, Sevket Tolga; Buyukserin, Fatih; Balci, Oguz; Budak, Gurer Guven

    2010-04-15

    Surfactant-free emulsion polymerization (SFEP) is a well-known technique for the production of polymeric nanoparticles that does not require post-synthetic cleaning steps. Obtaining hydrophobic particles at sub-100 nm scale, however, is quite challenging with this polymerization method. Here, we demonstrate a single step synthetic approach that yields poly(methylmethacrylate) (PMMA) nanoparticles with controlled sub-100 nm size and relatively high resultant solid content. Dynamic light scattering (DLS) was used for the particle characterization. Spherical and uniformly sized nanoparticles were confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Acetone was used as a cosolvent in order to obtain monodisperse sub-100 nm diameter particles. Stable PMMA nanoparticle dispersions were obtained for all formulations where the persulfate initiator causes the negative charges on the particle surface. The effects of acetone, monomer and initiator concentration were studied to optimize average particle hydrodynamic diameter and polydispersity index of the final particles. Non-crosslinked monodisperse PMMA nanoparticles (polydispersity index less than 0.05) with diameters from 32 nm to 72 nm were synthesized by using this method. PMID:20138293

  7. Evaluation of Thermal Control Coatings and Polymeric Materials Exposed to Ground Simulated Atomic Oxygen and Vacuum Ultraviolet Radiation

    NASA Technical Reports Server (NTRS)

    Kamenetzky, R. R.; Vaughn, J. A.; Finckenor, M. M.; Linton, R. C.

    1995-01-01

    Numerous thermal control and polymeric samples with potential International Space Station applications were evaluated for atomic oxygen and vacuum ultraviolet radiation effects in the Princeton Plasma Physics Laboratory 5 eV Neutral Atomic Oxygen Facility and in the MSFC Atomic Oxygen Drift Tube System. Included in this study were samples of various anodized aluminum samples, ceramic paints, polymeric materials, and beta cloth, a Teflon-impregnated fiberglass cloth. Aluminum anodizations tested were black duranodic, chromic acid anodize, and sulfuric acid anodize. Paint samples consisted of an inorganic glassy black paint and Z-93 white paint made with the original PS7 binder and the new K2130 binder. Polymeric samples evaluated included bulk Halar, bulk PEEK, and silverized FEP Teflon. Aluminized and nonaluminized Chemfab 250 beta cloth were also exposed. Samples were evaluated for changes in mass, thickness, solar absorptance, and infrared emittance. In addition to material effects, an investigation was made comparing diffuse reflectance/solar absorptance measurements made using a Beckman DK2 spectroreflectometer and like measurements made using an AZ Technology-developed laboratory portable spectroreflectometer.

  8. Effects of music therapy on pain among female breast cancer patients after radical mastectomy: results from a randomized controlled trial.

    PubMed

    Li, Xiao-Mei; Yan, Hong; Zhou, Kai-Na; Dang, Shao-Nong; Wang, Duo-Lao; Zhang, Yin-Ping

    2011-07-01

    Music therapy has been used in multiple health care settings to reduce patient pain, anxiety, and stress. However, few available studies have investigated its effect on pain among breast cancer patients after radical mastectomy. The aim of this study was to explore the effects of music therapy on pain reduction in patients with breast cancer after radical mastectomy. This randomized controlled trial was conducted at the Surgical Department of Oncology Center, First Affiliated Hospital of Xi'an Jiaotong University from March to November 2009. A total of 120 breast cancer patients who received Personal Controlled Analgesia (PCA) following surgery (mastectomy) were randomly allocated to two groups, an intervention group and a control group (60 patients in each group). The intervention group accepted music therapy from the first day after radical mastectomy to the third admission to hospital for chemotherapy in addition to the routine nursing care, while the control group received only routine nursing care. Pain scores were measured at baseline and three post-tests using the General Questionnaire and Chinese version of Short-Form of McGill Pain Questionnaire. The primary endpoint was the change in the Pain Rating Index (PRI-total) score from baseline. Music therapy was found to reduce the PRI-total score in the intervention group significantly compared with the control group with a mean difference (95% CI) of -2.38 (-2.80, -1.95), -2.41 (-2.85, -1.96), and -1.87 (-2.33, -1.42) for the 1st, 2nd, and 3rd post-tests, respectively. Similar results were found for Visual Analogue Scale (VAS) and Present Pain Intensity (PPI) scores. The findings of the study provide some evidence that music therapy has both short- and long-term positive effects on alleviating pain in breast cancer patients following radical mastectomy. PMID:21537935

  9. Polymeric microspheres

    DOEpatents

    Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

    2004-04-13

    The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

  10. Control of 3-dimensional collagen matrix polymerization for reproducible human mammary fibroblast cell culture in microfluidic devices.

    PubMed

    Sung, Kyung Eun; Su, Gui; Pehlke, Carolyn; Trier, Steven M; Eliceiri, Kevin W; Keely, Patricia J; Friedl, Andreas; Beebe, David J

    2009-09-01

    Interest in constructing a reliable 3-dimensional (3D) collagen culture platform in microfabricated systems is increasing as researchers strive to investigate reciprocal interaction between extracellular matrix (ECM) and cells under various conditions. However, in comparison to conventional 2-dimensional (2D) cell culture research, relatively little work has been reported about the polymerization of collagen type I matrix in microsystems. We, thus, present a study of 3D collagen polymerization to achieve reproducible 3D cell culture in microfluidic devices. Array-based microchannels are employed to efficiently examine various polymerization conditions, providing more replicates with less sample volume than conventional means. Collagen fibers assembled in microchannels were almost two-times thinner than those in conventional gels prepared under similar conditions, and the fiber thickness difference influenced viability and morphology of embedded human mammary fibroblast (HMF) cells. HMF cells contained more actin stress fibers and showed increased viability in 3D collagen matrix composed of thicker collagen fibers. Relatively low pH of the collagen solution within a physiological pH range (6.5-8.5) and pre-incubation at low temperature (approximately 4 degrees C) before polymerization at 37 degrees C allow sufficient time for molecular assembly, generating thicker collagen fibers and enhancing HMF cell viability. The results provide the basis for improved process control and reproducibility of 3D collagen matrix culture in microchannels, allowing predictable modifications to provide optimum conditions for specific cell types. In addition, the presented method lays the foundation for high throughput 3D cellular screening. PMID:19540580

  11. Controlled trial of polymeric versus elemental diet in treatment of active Crohn's disease.

    PubMed

    Giaffer, M H; North, G; Holdsworth, C D

    1990-04-01

    30 patients with active Crohn's disease, mean Crohn's Disease Activity Index 301 (SE 32), who would otherwise have been treated with steroids, were randomised to receive for 4 weeks either an elemental diet ('Vivonex') (n = 16) or a polymeric diet ('Fortison') (n = 14). Assessment on days 10 and 28 showed that clinical remission occurred in 5 (36%) of the 14 patients on fortison compared with 12 (75%) of the 16 patients assigned to vivonex. The difference in remission rate was significant (p less than 0.03). Dietary treatment resulted in little change in the nutritional state and various laboratory indices of activity over a 4 week period despite clinical improvement. Polymeric diets do not seem to offer an effective therapeutic alternative to elemental diets in patients with acute exacerbations of Crohn's disease. PMID:1969560

  12. Polymerization as a Model Chain Reaction

    ERIC Educational Resources Information Center

    Morton, Maurice

    1973-01-01

    Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

  13. Novel approach to produce polymerized hydrocarbon coatings using dielectric barrier controlled atmospheric pressure glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Mishra, K. K.; Khardekar, R. K.; Singh, Rashmi; Pant, H. C.

    2002-09-01

    Conventionally, low-pressure (<1 Torr) electrical discharges are used for material processing and thin-film deposition. These schemes suffer mainly due to the high cost of equipment and the complexity of operations. The atmospheric pressure glow discharge plasma is developed using a threaded styled electrode in different configurations, and these reactors are used to produce plasma polymerized coatings, required on plane substrates as self-supporting films to obtain membranes for blocking holes in cavities, and on microballoon targets, which are used as fuel containers for inertial confinement fusion, to avoid DT gas permeation. Helium gas is used as the supporting gas for formation and stabilization of atmospheric pressure glow discharge plasma reactors. Ethylene and acetylene gases are used as monomers to produce plasma polymerized hydrocarbon films. These films are characterized using scanning electron microscopy. Plasma polymerized coatings of thickness 100 nm-10 μm with a smooth surface finish (rms<100 nm) are deposited successfully. The surface finish is further improved using a postdischarge configuration. Preliminary results are very encouraging but further progress is to be made in this area. We are also planning to extend this technique for C:H coating of microballoons, which are used as fuel containers in inertial confinement fusion.

  14. Structure Control of Nitrogen-Rich Graphene Nanosheets Using Hydrothermal Treatment and Formaldehyde Polymerization for Supercapacitors.

    PubMed

    Wen, Yangyang; Rufford, Thomas E; Hulicova-Jurcakova, Denisa; Zhu, Xiaobo; Wang, Lianzhou

    2016-07-20

    Nitrogen-rich graphene nanosheets (NGN) with intentionally crumpled, stacked, and cross-linked sheet structures were developed using hydrothermal and/or formaldehyde polymerization processes. It is revealed that the hydrothermal treatment produced crumpled NGN (6.0 at% N) with a high surface area of 383 m(2)·g(-1). In contrast, the formaldehyde polymerization process yielded stacked NGN (11.3 at% N) with very low surface area. The combination of formaldehyde polymerization synthesis with hydrothermal treatment led to NGN (14.7 at% N) with a cross-linked structure and a moderate surface area of 88 m(2)·g(-1). Interestingly, this cross-linked NGN exhibited the best electrochemical performance compared with other NGN, with a remarkable specific capacitance of 201 F·g(-1) at 0.05 A·g(-1) in 1 M H2SO4 electrolyte, and an excellent retention rate of 96.2% of the initial capacitance after 10 000 charge-discharge cycles at a current density of 5 A·g(-1) was achieved. PMID:27341589

  15. Electron-beam induced RAFT-graft polymerization of poly(acrylic acid) onto PVDF

    NASA Astrophysics Data System (ADS)

    Grasselli, M.; Betz, N.

    2005-07-01

    This paper explores for the first time the post-radiation-induced-graft polymerization on solid substrate using reversible addition-fragmentation transfer (RAFT) mechanism. Radiation-induced graft polymerization onto polymers is a potentially interesting technique to create easily new materials from highly resistant polymers, e.g. surface graft polymerization of acrylic acid (AA) onto poly(vinylidene difluoride) (PVDF) improves its surface properties without losing its excellent mechanical properties. As a consequence of the radical nature of the polymerization processes it is difficult to control molecular weight of grafted chains, and therefore design and standardize the properties of the final product. RAFT polymerization is a suitable method to obtain monodisperse polymers. The ability of the RAFT agents to control the polymer chain length could be an interesting approach to improve the grafted polymers obtained by post-radiation-induced-graft polymerization technique. In this way, graft polymerization of AA onto electron-beam irradiated α-PVDF was performed using trithiocarbonic acid bis(1-phenylethyl) ester as a RAFT agent to control the radical polymerization. We studied several grafting parameters such as solvent, monomer concentration and grafting time in order to achieve a poly(acrylic acid) (PAA) layer onto PVDF surface. Acetic acid was found to be the best solvent for many reasons, as to drive graft polymerization mainly to the polymer surface, complete solubility and stability of all reactants. Hydrolysis of PAA chains was also studied in order to remove the trithiocarbonate functionality from the grafted polymer. A mild chemical condition was achieved in order to have thiol groups that were detected onto the modified PVDF by specific enzymatic reaction.

  16. Voltage-responsive reversible self-assembly and controlled drug release of ferrocene-containing polymeric superamphiphiles.

    PubMed

    Chang, Xueyi; Cheng, Zhiyu; Ren, Biye; Dong, Renfeng; Peng, Jun; Fu, Shiyu; Tong, Zhen

    2015-10-14

    A new type of voltage-responsive comb-like superamphiphilic block polymer PEG113-b-PAA30/FTMA was prepared by the electrostatic interactions of an ionic ferrocenyl surfactant (FTMA) and an oppositely charged double-hydrophilic block polyelectrolyte poly-(ethylene glycol)-b-poly(acrylic acid) (PEG113-b-PAA30) in aqueous solution. An in situ electrochemical redox system was designed to research its electrochemical activity in aqueous solution. The polymeric superamphiphile PEG113-b-PAA30/FTMA could reversibly aggregate to form spherical micelles of 20-30 nm diameter in aqueous solution, and also disaggregate into irregular fragments by an electrochemical redox reaction when its concentration is in the range of the critical aggregation concentration (cacred) of the reduction state to its cacox of the oxidation state. Interestingly, above cacox, the superamphiphile can aggregate into spherical micelles of 20-30 nm diameter, which can be transformed into larger spherical micelles of 40-120 nm diameter after electrochemical oxidation, and reversibly recover initial sizes after electrochemical reduction. Moreover, this reversible self-assembly process can be electrochemically controlled just by changing its electrochemical redox extent without adding any other chemical reagent. Further, rhodamine 6G (R6G)-loaded polymeric superamphiphile aggregates have been successfully used for the voltage-controlled release of loaded molecules based on their voltage-responsive self-assembly, and the release rate of R6G could be mediated by changing electrochemical redox potentials and the concentrations of polymeric superamphiphiles. Our observations witness a new strategy to construct a voltage-responsive reversible self-assembly system. PMID:26268718

  17. ACD toxin-produced actin oligomers poison formin-controlled actin polymerization

    PubMed Central

    Heisler, David B.; Kudryashova, Elena; Grinevich, Dmitry O.; Suarez, Cristian; Winkelman, Jonathan D.; Birukov, Konstantin G.; Kotha, Sainath R.; Parinandi, Narasimham L.; Vavylonis, Dimitrios; Kovar, David R.; Kudryashov, Dmitri S.

    2015-01-01

    The actin crosslinking domain (ACD) is an actin-specific toxin produced by several pathogens, including life-threatening spp. of Vibrio cholerae, Vibrio vulnificus, and Aeromonas hydrophila. Actin crosslinking by ACD is thought to lead to slow cytoskeleton failure owing to a gradual sequestration of actin in the form of nonfunctional oligomers. Here we found that ACD converted cytoplasmic actin into highly toxic oligomers that potently “poisoned” the ability of major actin assembly proteins, formins, to sustain actin polymerization. Thus, ACD can target the most abundant cellular protein by employing actin oligomers as secondary toxins to efficiently subvert cellular functions of actin while functioning at very low doses. PMID:26228148

  18. Hydroxyl radicals in indoor environments

    NASA Astrophysics Data System (ADS)

    Sarwar, Golam; Corsi, Richard; Kimura, Yosuke; Allen, David; Weschler, Charles J.

    Indoor hydroxyl radical concentrations were estimated using a new indoor air quality model which employs the SAPRC-99 atmospheric chemistry model to simulate indoor homogenous reactions. Model results indicate that typical indoor hydroxyl radical concentrations are lower than typical outdoor summertime urban hydroxyl radical levels of 5-10×10 6 molecules cm -3; however, indoor levels can be similar to or greater than typical nighttime outdoor hydroxyl radical levels of approximately 5×10 4 molecules cm -3. Effects of selected parameters on indoor hydroxyl radical concentrations are presented herein. Indoor hydroxyl radical concentrations are predicted to increase non-linearly with increasing outdoor ozone concentrations, indoor alkene emission rates, and air exchange rates. Indoor hydroxyl radical concentrations decrease with increasing outdoor nitric oxide concentrations. Indoor temperature and indoor light intensity have moderate impacts on indoor hydroxyl radical concentrations. Outdoor hydroxyl radical concentrations, outdoor nitrate (NO 3rad ) radical concentrations, outdoor hydroperoxy radical concentrations, and hydroxyl radical removal by indoor surfaces are predicted to have no appreciable impact on indoor hydroxyl radical concentrations. Production of hydroxyl radicals in indoor environments appears to be controlled primarily by reactions of alkenes with ozone, and nitric oxide with hydroperoxy radical. Estimated indoor hydroxyl radical levels may potentially affect indoor air quality. Two examples are presented in which reactions of d-limonene and α-pinene with indoor hydroxyl radicals produce aldehydes, which may be of greater concern than the original compounds.

  19. Encapsulation of the synthetic retinoids Am80 and LE540 into polymeric micelles and the retinoids' release control.

    PubMed

    Satoh, Taku; Higuchi, Yuriko; Kawakami, Shigeru; Hashida, Mitsuru; Kagechika, Hiroyuki; Shudo, Koichi; Yokoyama, Masayuki

    2009-06-19

    The objective of this study was to encapsulate two synthetic retinoids Am80 and LE540 into polymeric micelles and to control the retinoids' release rate in vitro. Highly efficient encapsulation yields of these retinoids were obtained for micelles forming from PEG-poly(benzyl aspartate) block copolymers in the wide range of the benzyl substitution degree. The in vitro release examination for LE540 indicated very stable encapsulation of this retinoid owing to its strongly hydrophobic nature. On the other hand, Am80 exhibited a rapid release in Dulbecco's phosphate buffer saline. An addition of a hydrophobic alkyl amine in the Am80-encapsulation process successfully led to significant retardation of the Am80 release rate. A mechanism of the retardation was considered an increase of Am80 hydrophobicity due to an ion-pairing with the alkyl amine. This paper is the first report on release control in the polymeric micelle carrier system through the ion-pairing between an encapsulated drug and an additive. PMID:19289148

  20. Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals.

    PubMed

    Kirste, Moritz; Wang, Xingan; Schewe, H Christian; Meijer, Gerard; Liu, Kopin; van der Avoird, Ad; Janssen, Liesbeth M C; Gubbels, Koos B; Groenenboom, Gerrit C; van de Meerakker, Sebastiaan Y T

    2012-11-23

    Whereas atom-molecule collisions have been studied with complete quantum-state resolution, interactions between two state-selected molecules have proven much harder to probe. Here, we report the measurement of state-resolved inelastic scattering cross sections for collisions between two open-shell molecules that are both prepared in a single quantum state. Stark-decelerated hydroxyl (OH) radicals were scattered with hexapole-focused nitric oxide (NO) radicals in a crossed-beam configuration. Rotationally and spin-orbit inelastic scattering cross sections were measured on an absolute scale for collision energies between 70 and 300 cm(-1). These cross sections show fair agreement with quantum coupled-channels calculations using a set of coupled model potential energy surfaces based on ab initio calculations for the long-range nonadiabatic interactions and a simplistic short-range interaction. This comparison reveals the crucial role of electrostatic forces in complex molecular collision processes. PMID:23180857

  1. Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes

    PubMed Central

    Gugliuzza, Annarosa; Perrotta, Maria Luisa; Drioli, Enrico

    2016-01-01

    This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly. PMID:27196938

  2. Initiator Control of Conjugated Polymer Topology in Ring-Opening Alkyne Metathesis Polymerization.

    PubMed

    von Kugelgen, Stephen; Bellone, Donatela E; Cloke, Ryan R; Perkins, Wade S; Fischer, Felix R

    2016-05-18

    Molybdenum carbyne complexes [RC≡Mo(OC(CH3)(CF3)2)3] featuring a mesityl (R = Mes) or an ethyl (R = Et) substituent initiate the living ring-opening alkyne metathesis polymerization of the strained cyclic alkyne, 5,6,11,12-tetradehydrobenzo[a,e][8]annulene, to yield fully conjugated poly(o-phenylene ethynylene). The difference in the steric demand of the polymer end-group (Mes vs Et) transferred during the initiation step determines the topology of the resulting polymer chain. While [MesC≡Mo(OC(CH3)(CF3)2)3] exclusively yields linear poly(o-phenylene ethynylene), polymerization initiated by [EtC≡Mo(OC(CH3)(CF3)2)3] results in cyclic polymers ranging in size from n = 5 to 20 monomer units. Kinetic studies reveal that the propagating species emerging from [EtC≡Mo(OC(CH3)(CF3)2)3] undergoes a highly selective intramolecular backbiting into the butynyl end-group. PMID:27120088

  3. Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes.

    PubMed

    Gugliuzza, Annarosa; Perrotta, Maria Luisa; Drioli, Enrico

    2016-01-01

    This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly. PMID:27196938

  4. Polymerization Kinetics: Monitoring Monomer Conversion Using an Internal Standard and the Key Role of Sample "t[subscript 0]"

    ERIC Educational Resources Information Center

    Colombani, Olivier; Langelier, Ophelie; Martwong, Ekkachai; Castignolles, Patrice

    2011-01-01

    The use of an internal standard is a conventional and convenient way to monitor the conversion of one or several monomers during a controlled radical polymerization. However, the validity of this technique relies on an accurate determination of the initial monomer-to-internal standard ratio, A[subscript 0], because all subsequent calculations of…

  5. Cavity ring-down spectroscopy with an automated control feedback system for investigating nitrate radical surface chemistry reactions

    NASA Astrophysics Data System (ADS)

    Flemmer, Michael M.; Ham, Jason E.

    2012-08-01

    Nitrate radical (NO3•) surface chemistry of indoor environments has not been well studied due to the difficulty in generating and maintaining NO3• at low concentrations for long term exposures. This article presents the Surface Chemistry Reactant Air Delivery and Experiment System (SCRADES), a novel feedback controlled system developed to deliver nitrate radicals at specified concentrations (50-500 ppt, ±30 ppt) and flow rates (500-2000 ml min-1) to a variety of indoor surfaces to initiate reaction chemistry for periods of up to 72 h. The system uses a cavity ring-down spectrometer (CRDS), with a detection limit of 1.7 ppt, to measure the concentration of NO3• supplied to a 24 l experiment chamber. Nitrate radicals are introduced via thermal decomposition of N2O5 and diluted with clean dry air until the desired concentration is achieved. Additionally, this article addresses details concerning NO3• loss through the system, consistency of the NO3• concentration delivered, and stability of the CRDS cavity over long exposure durations (72 h).

  6. Development of an in situ controllable polymerization tool and process for hydrogel used to replace nucleus pulposus

    NASA Astrophysics Data System (ADS)

    Schmocker, Andreas M.; Khoushabi, Azadeh; Bourban, Pierre-Etienne; Schizas, Constantin; Pioletti, Dominique P.; Moser, Christophe

    2015-06-01

    Currently implants or tissue replacements are inserted either as a whole implant or by injecting a liquid which polymerizes to form a solid implant at the appropriate location. This is either highly invasive or not controllable. We developed a tool to perform such surgeries in a minimally invasive and controllable way. It combines photopolymerization and fluorescence spectroscopy in a surgical apparatus. However, to successfully replace tissue such as cartilage or an intervertebral disc, photopolymerizable materials do not only need to be photoactive. They should also be able to withstand the environmental loading conditions after implantation. Therefore we developed a set of in situ and in vitro tests adapted to the evaluation of photopolymerized tissue replacements and implants. In particular in this article, we report on a method, which combines photopolymerization and photorheology to track the current state of polymer during photopolymerization.

  7. Contemporary Radical Prostatectomy

    PubMed Central

    Fu, Qiang; Moul, Judd W.; Sun, Leon

    2011-01-01

    Purpose. Patients diagnosed with clinically localized prostate cancer have more surgical treatment options than in the past. This paper focuses on the procedures' oncological or functional outcomes and perioperative morbidities of radical retropubic prostatectomy, radical perineal prostatectomy, and robotic-assisted laparoscopic radical prostatectomy. Materials and Methods. A MEDLINE/PubMed search of the literature on radical prostatectomy and other new management options was performed. Results. Compared to the open procedures, robotic-assisted radical prostatectomy has no confirmed significant difference in most literatures besides less blood loss and blood transfusion. Nerve sparing is a safe means of preserving potency on well-selected patients undergoing radical prostatectomy. Positive surgical margin rates of radical prostatectomy affect the recurrence and survival of prostate cancer. The urinary and sexual function outcomes have been vastly improved. Neoadjuvant treatment only affects the rate of positive surgical margin. Adjuvant therapy can delay and reduce the risk of recurrence and improve the survival of the high risk prostate cancer. Conclusions. For the majority of patients with organ-confined prostate cancer, radical prostatectomy remains a most effective approach. Radical perineal prostatectomy remains a viable approach for patients with morbid obesity, prior pelvic surgery, or prior pelvic radiation. Robot-assisted laparoscopic prostatectomy (RALP) has become popular among surgeons but has not yet become the firmly established standard of care. Long-term data have confirmed the efficacy of radical retropubic prostatectomy with disease control rates and cancer-specific survival rates. PMID:22110994

  8. Radical Coupling Mechanisms in Lignification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mechansim by which lignification, the polymerization process by which lignins are formed, is via combinatorial radical coupling reactions. Understanding such reactions allows the range of structures in lignins to be understood, and the ability of lignins to accommodate various phenolic precursor...

  9. Fundamentals of Atom Transfer Radical Polymerization

    ERIC Educational Resources Information Center

    Coessens, Veerle M. C.; Matyjaszewski, Krzysztof

    2010-01-01

    Today's market increasingly demands sophisticated materials for advanced technologies and high-value applications, such as nanocomposites, optoelectronic, or biomedical materials. Therefore, the demand for well-defined polymers with very specific molecular architecture and properties increases. Until recently, these kinds of polymers could only be…

  10. Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane

    NASA Astrophysics Data System (ADS)

    Tanaka, Hidenori; Iwasaki, Isao; Kunai, Yuichiro; Sato, Nobuhiro; Matsuyama, Tomochika

    2011-08-01

    The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through γ-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of 1H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of γ-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.

  11. Radical-mediated step-growth: Preparation of hybrid polymer monolithic columns with fine control of nanostructural and chromatographic characteristics.

    PubMed

    Alves, Filipa; Nischang, Ivo

    2015-09-18

    The currently most successful type of porous polymer monoliths utilized in chromatography is prepared by free-radical cross-linking (co)polymerization in porogenic solvents and a single-step molding process. Though such types of materials are well-recognized in the scientific community, they suffer from their multi-scale heterogeneity originating from the nanoscale through to their microscale and ultimately limited performance on their macroscale. This is in particular true when estimating their performance under equilibrium (i.e. isocratic) elution conditions for retained compounds. In this contribution, we study a new concept in the preparation of porous monolithic hybrid materials based on polyhedral oligomeric vinylsilsesquioxanes which undergo radical mediated step-growth cross-linking with thiol-linkers. Fundamental characterization of this new entry of materials is performed via a variety of characterization approaches including infrared and Raman spectroscopies, thermogravimetric analysis, gel fraction, dry-state surface area analysis, and visualization of the capillary-scale porous structure by scanning electron microscopy. This characterization identifies that a rational choice of experimental conditions in monolith preparation leads to destined and desirable materials' properties, in particular with experimentally accessible near-ideal nanoscale network structures. With the obtained structural informations at hand, we finally evidence the monoliths' tailored chromatographic performance by isocratic elution experiments of structurally similar small molecules under reversed-phase type of chromatographic conditions. This validates the fundamental origin for an improved performance of these types of monolithic materials under solvated conditions that has its foundation established in the creation of near-ideal nanoscale networks of material. This identified ideality is manifested in an enhanced and almost retention-insensitive performance in liquid

  12. Free-radical-mediated DNA binding.

    PubMed Central

    O'Brien, P J

    1985-01-01

    Free-radical metabolites can be generated metabolically by a one-electron reductase-catalyzed reaction or a "peroxidase" catalyzed oxidation or by photoactivation of a wide variety of aromatic xenobiotics. Radicals may also be generated during lipid peroxidation. Some radicals can react with DNA or bind covalently or noncovalently as a dismutation product or as a dimer, trimer or polymeric product. Modification to the DNA can result in single-strand breaks, loss of template activity, and crosslinking. The binding can prevent enzymic digestion. In some cases, the radicals react with oxygen, resulting before conversion to DNA reactive oxygen species. Most radicals probably do not interact with DNA. PMID:3007090

  13. Improved Livingness and Control over Branching in RAFT Polymerization of Acrylates: Could Microflow Synthesis Make the Difference?

    PubMed

    Derboven, Pieter; Van Steenberge, Paul H M; Vandenbergh, Joke; Reyniers, Marie-Francoise; Junkers, Thomas; D'hooge, Dagmar R; Marin, Guy B

    2015-12-01

    The superior capabilities of structured microreactors over batch reactors are demonstrated for reversible addition-fragmentation chain transfer (RAFT) solution polymerization of n-butyl acrylate with the aid of simulations, explicitly accounting for the chain length distribution of all macrospecies types. Since perfect isothermicity can be established in a microreactor, less side products due to backbiting and β-scission are formed compared to the batch operation in which ineffective heat removal leads to an undesirable temperature spike. For a given RAFT chain transfer agent (CTA), additional microstructural control results under microflow conditions by optimizing the reaction temperature, lowering the dilution degree, or decreasing the initial molar ratio of monomer to RAFT CTA. PMID:26400634

  14. Admicellar polymerization of precipated silica

    SciTech Connect

    Reynolds, J.L.; Grady, B.P.; Harwell, J.H.

    1996-10-01

    The tendency of a surfactant molecule to adsorb at a solid-liquid interface is the basis for an in situ surface modification process, termed admicellar polymerization. The four-step admicellar polymerization process includes: (1) adsorption of surfactant at the solid-liquid interface, (2) adsolubilization of monomer into the surfactant bilayer, (3) polymerization using free-radical initiators and heat, (4) removal of excess surfactant to expose the polymer modified surface. The process is used to apply polymer to precipitated silica to enhance the compatibility of the silica when added to filled rubber. The adsorption isotherms were first determined for particular surfactant/silica combinations to find the surfactant concentration that would sufficiently adsolubilize the monomer, while remaining below the critical micelle concentration. A series of experiments were then devised for the polymerization reactions in which the surfactant and monomer amounts were varied over three levels to establish the optimal combination.

  15. Stimuli-Responsive Polymeric Systems for Controlled Protein and Peptide Delivery: Future Implications for Ocular Delivery.

    PubMed

    Mahlumba, Pakama; Choonara, Yahya E; Kumar, Pradeep; du Toit, Lisa C; Pillay, Viness

    2016-01-01

    Therapeutic proteins and peptides have become notable in the drug delivery arena for their compatibility with the human body as well as their high potency. However, their biocompatibility and high potency does not negate the existence of challenges resulting from physicochemical properties of proteins and peptides, including large size, short half-life, capability to provoke immune responses and susceptibility to degradation. Various delivery routes and delivery systems have been utilized to improve bioavailability, patient acceptability and reduce biodegradation. The ocular route remains of great interest, particularly for responsive delivery of macromolecules due to the anatomy and physiology of the eye that makes it a sensitive and complex environment. Research in this field is slowly gaining attention as this could be the breakthrough in ocular drug delivery of macromolecules. This work reviews stimuli-responsive polymeric delivery systems, their use in the delivery of therapeutic proteins and peptides as well as examples of proteins and peptides used in the treatment of ocular disorders. Stimuli reviewed include pH, temperature, enzymes, light, ultrasound and magnetic field. In addition, it discusses the current progress in responsive ocular drug delivery. Furthermore, it explores future prospects in the use of stimuli-responsive polymers for ocular delivery of proteins and peptides. Stimuli-responsive polymers offer great potential in improving the delivery of ocular therapeutics, therefore there is a need to consider them in order to guarantee a local, sustained and ideal delivery of ocular proteins and peptides, evading tissue invasion and systemic side-effects. PMID:27483234

  16. Redox Initiation of Bulk Thiol-Ene Polymerizations

    PubMed Central

    Cole, Megan A.; Jankousky, Katherine C.; Bowman, Christopher N.

    2013-01-01

    The unique formation-structure-property attributes and reaction behavior of the thiol-ene “click” reaction have been explored extensively for photochemically and thermally initiated reactions but have been much less explored for redox initiation. Therefore, the objective of this work is to characterize fully the impact of the initiation system, monomer structure, degree of functionalization, and inhibitor level on the redox-mediated thiol-ene polymerization rate and behavior. Moreover, this study confirms the ability of redox initiation to achieve full conversion of desired thiol-ene “click” products for small molecules in solution. For the multifunctional thiol-ene systems, polymerization rate was shown to be comparable to photo- and thermally initiated systems, but with the additional advantages of unlimited depth of cure and mild reaction conditions. Additionally, the network properties of the redox-initiated thiol-ene systems were on par with a photocured material formulated with identical monomers and radical initiating potential. Lastly, control over the polymerization rate and preceding induction period was garnered from the concentration of inhibitor included in the reaction mixture. The mechanism of action of quinone inhibition in redox-mediated thiol-ene polymerizations is shown to depend on both the presence of an aniline reducing agent and the concentration of inhibitor, with quinone concentrations in great excess of oxidizing agent concentrations actually leading to heightened polymerization rates when aniline is present. PMID:23565125

  17. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1987-05-12

    A process is described for polymerizing at least one alpha olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst system which comprises: a supported catalyst prepared under anhydrous conditions by the sequential steps of: preparing a slurry of inert particulate support material; adding to the slurry a solution of an organomagnesium compound; adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; adding to the slurry and reacting a halogenator; adding to the slurry and reacting a tetravalent titanium halide compound; and recovering solid catalyst.

  18. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1986-10-21

    A process is described for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst comprising: a supported catalyst prepared under anhydrous conditions by the steps of: (1) sequentially; (a) preparing a slurry of inert particulate support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of zirconium compound; and (2) thereafter; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium compound; (f) recovering solid catalyst; and an organoaluminum compound.

  19. Efficacy and oncologic safety of nerve-sparing radical hysterectomy for cervical cancer: a randomized controlled trial

    PubMed Central

    Roh, Ju-Won; Lee, Dong Ock; Lim, Myong Cheol; Seo, Sang-Soo; Chung, Jinsoo; Lee, Sun

    2015-01-01

    Objective A prospective, randomized controlled trial was conducted to evaluate the efficacy of nerve-sparing radical hysterectomy (NSRH) in preserving bladder function and its oncologic safety in the treatment of cervical cancer. Methods From March 2003 to November 2005, 92 patients with cervical cancer stage IA2 to IIA were randomly assigned for surgical treatment with conventional radical hysterectomy (CRH) or NSRH, and 86 patients finally included in the analysis. Adequacy of nerve sparing, radicality, bladder function, and oncologic safety were assessed by quantifying the nerve fibers in the paracervix, measuring the extent of paracervix and harvested lymph nodes (LNs), urodynamic study (UDS) with International Prostate Symptom Score (IPSS), and 10-year disease-free survival (DFS), respectively. Results There were no differences in clinicopathologic characteristics between two groups. The median number of nerve fiber was 12 (range, 6 to 21) and 30 (range, 17 to 45) in the NSRH and CRH, respectively (p<0.001). The extent of resected paracervix and number of LNs were not different between the two groups. Volume of residual urine and bladder compliance were significantly deteriorated at 12 months after CRH. On the contrary, all parameters of UDS were recovered no later than 3 months after NSRH. Evaluation of the IPSS showed that the frequency of long-term urinary symptom was higher in CRH than in the NSRH group. The median duration before the postvoid residual urine volume became less than 50 mL was 11 days (range, 7 to 26 days) in NSRH group and was 18 days (range, 10 to 85 days) in CRH group (p<0.001). No significant difference was observed in the 10-year DFS between two groups. Conclusion NSRH appears to be effective in preserving bladder function without sacrificing oncologic safety. PMID:25872890

  20. Hydration-controlled X-band EPR spectroscopy: a tool for unravelling the complexities of the solid-state free radical in eumelanin.

    PubMed

    Mostert, A Bernardus; Hanson, Graeme R; Sarna, Tadeusz; Gentle, Ian R; Powell, Benjamin J; Meredith, Paul

    2013-05-01

    Melanin, the human skin pigment, is found everywhere in nature. Recently it has gained significant attention for its potential bioelectronic properties. However, there remain significant obstacles in realizing its electronic potential, in particular, the identity of the solid-state free radical in eumelanin, which has been implicated in charge transport. We have therefore undertaken a hydration-controlled continuous-wave electron paramagnetic resonance study on solid-state eumelanin. Herein we show that the EPR signal from solid-state eumelanin arises predominantly from a carbon-centered radical but with an additional semiquinone free radical component. Furthermore, the spin densities of both of these radicals can be manipulated using water and pH. In the case of the semiquinone radical, the comproportionation reaction governs the pH- and hydration-dependent behavior. In contrast, the mechanism underlying the carbon-centered radical's pH- and hydration-dependent behavior is not clear; consequently, we have proposed a new destacking model in which the intermolecular structure of melanin is disordered due to π-π destacking, brought about by the addition of water or increased pH, which increases the proportion of semiquinone radicals via the comproportionation reaction. PMID:23600769

  1. Assembly-Controlled Permeability of Layer-by-Layer Polymeric Microcapsules Using a Tapered Fluidized Bed.

    PubMed

    Noi, Ka Fung; Roozmand, Ali; Björnmalm, Mattias; Richardson, Joseph J; Franks, George V; Caruso, Frank

    2015-12-23

    Nano- and microcapsules engineered through layer-by-layer (LbL) assembly are finding an increasingly large number of applications as catalysts, electrochemical biosensors, bioreactors, artificial cells and drug delivery vehicles. While centrifugation-based LbL assembly is the most common method for coating template particles and preparing capsules, it is a batch process and requires frequent intervention that renders the system challenging to automate and scale up. Here, we report the use of a tapered fluidized bed (TFB) for the preparation of multilayered polymer capsules. This is a significant improvement over our recent approach of fluidizing particles in cylindrical fluidized beds (CFB) for LbL assembly. We demonstrate that TFB is compatible with particles <3 μm in diameter (an order-of-magnitude improvement compared with CFB), which can be fluidized with minimal entrainment. Additionally, layering materials were expanded to include both electrostatic and hydrogen-bonding polymer pairs (e.g., poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS), and thiol-modified poly(methacrylic acid) (PMASH) and poly(N-vinylpyrrolidone) (PVPON), respectively). Finally, differences between capsules prepared via centrifugation-based and TFB LbL assembly were investigated. The obtained TFB microcapsules demonstrate increased film thickness and roughness compared with those prepared using centrifugation-based LbL assembly. Furthermore, PMASH microcapsules exhibit lower swelling and permeability when prepared via TFB LbL assembly compared with centrifugation-based LbL assembly due to enhanced multilayer deposition, entanglement, and cross-linking. Therefore, polymeric capsules fabricated via TFB LbL assembly may be useful for encapsulation and retention of relatively low molecular weight (∼20 kDa) hydrophilic biomacromolecules to passively or responsively release the payload for drug delivery applications. PMID:26651354

  2. Metal–insulator transition of valence-controlled VO2 thin film prepared by RF magnetron sputtering using oxygen radical

    NASA Astrophysics Data System (ADS)

    Suetsugu, Takaaki; Shimazu, Yuichi; Tsuchiya, Takashi; Kobayashi, Masaki; Minohara, Makoto; Sakai, Enju; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru

    2016-06-01

    We have prepared b-axis-oriented VO2 thin films by RF magnetron sputtering using oxygen radicals as the reactive gas. The VO2 thin films consist of a mixed-valence V3+/V4+ state formed by oxygen vacancies. The V3+ ratio strongly depends on the film thickness and the oxygen partial pressure of the radical gun during deposition. The lattice constant of the b-axis increases and the metal–insulator transition (MIT) temperature decreases with decreasing V3+ ratio, although the VO2 thin films with a high V3+ ratio of 42% do not exhibit MIT. The bandwidths and spectral weights of V 3d a1g and \\text{e}\\text{g}σ bands at around the Fermi level, which correspond to the insulating phase at 300 K, are smaller in the VO2 thin films with a low V3+ ratio. These results indicate that the control of the mixed-valence V3+/V4+ state is important for the MIT of b-axis-oriented VO2 thin films.

  3. Metal-free ring-opening metathesis polymerization.

    PubMed

    Ogawa, Kelli A; Goetz, Adam E; Boydston, Andrew J

    2015-02-01

    We have developed a method to achieve ring-opening metathesis polymerization (ROMP) mediated by oxidation of organic initiators in the absence of any transition metals. Radical cations, generated via one-electron oxidation of vinyl ethers, were found to react with norbornene to give polymeric species with microstructures essentially identical to those traditionally obtained via metal-mediated ROMP. We found that vinyl ether oxidation could be accomplished under mild conditions using an organic photoredox mediator. This led to high yields of polymer and generally good correlation between M(n) values and initial monomer to catalyst loadings. Moreover, temporal control over reinitiation of polymer growth was achieved during on/off cycles of light exposure. This method demonstrates the first metal-free method for controlled ROMP. PMID:25573294

  4. Effective integrative supramolecular polymerization.

    PubMed

    Zhang, Qiwei; Tian, He

    2014-09-26

    Exercise control: By taking advantage of self-sorting processes among host-guest components, a controlled supramolecular polymerization can be realized, as demonstrated recently with the preparation of a cucurbit[n]uril-based supramolecular polymer. This method may be used for the design of more ordered supramolecular polymers from complex and discrete components. PMID:25080388

  5. Restricted access chiral stationary phase synthesized via reversible addition-fragmentation chain-transfer polymerization for direct analysis of biological samples by high performance liquid chromatography.

    PubMed

    Song, Wen-Jun; Wei, Ji-Ping; Wang, Su-Ying; Wang, Huai-Song

    2014-06-17

    Novel hydrophilic microparticles containing β-cyclodextrin (β-CD) were prepared via one-pot synthesis using reversible addition-fragmentation chain-transfer (RAFT) precipitation polymerization, a "controlled/living" radical polymerization technique. The polymerization was initiated by hydrophilic macromolecular chain-transfer agent [poly(2-hydroxyethyl methacrylate), PHEMA]. The hydrophilic PHEMA on the surface of microparticles can well improve their surface hydrophilicity and lead to their biological compatibility. As chiral restricted access material (RAM), the hydrophilic microparticles can be used for determination of enantiomers in biological samples with direct injection via HPLC analysis. PMID:24890695

  6. Aqueous Copper(II) Photoinduced Polymerization of Acrylates: Low Copper Concentration and the Importance of Sodium Halide Salts.

    PubMed

    Jones, Glen R; Whitfield, Richard; Anastasaki, Athina; Haddleton, David M

    2016-06-15

    Photoinduced metal-mediated radical polymerization is a rapidly developing technique which allows for the synthesis of macromolecules with defined molecular weight and narrow molecular weight distributions, although typically exhibiting significant limitations in aqueous media. Herein we demonstrate that the presence of alkali metal halide salts, in conjunction with low copper concentration and UV irradiation, allows for the controlled polymerization of water-soluble acrylates in aqueous media, yielding narrow molecular weight distributions and high conversions. Despite the aqueous environment which typically compromises polymer end group fidelity, chain extensions have also been successfully performed and different degrees of polymerization were targeted. Importantly, no conversion was observed in the absence of UV light and the polymerization could be switched "on" and "off" upon demand, as demonstrated by intermittent light and dark periods and thus allowing access to spatiotemporal control. PMID:27184213

  7. CO2-responsive polymeric materials: synthesis, self-assembly, and functional applications.

    PubMed

    Darabi, Ali; Jessop, Philip G; Cunningham, Michael F

    2016-08-01

    CO2 is an ideal trigger for switchable or stimuli-responsive materials because it is benign, inexpensive, green, abundant, and does not accumulate in the system. Many different CO2-responsive materials including polymers, latexes, solvents, solutes, gels, surfactants, and catalysts have been prepared. This review focuses on the preparation, self-assembly, and functional applications of CO2-responsive polymers. Detailed discussion is provided on the synthesis of CO2-responsive polymers, in particular using reversible deactivation radical polymerization (RDRP), formerly known as controlled/living radical polymerization (CLRP), a powerful technique for the preparation of well-defined (co)polymers with precise control over molecular weight distribution, chain-end functional groups, and polymer architectural design. Self-assembly in aqueous dispersed media is highlighted as well as emerging potential applications. PMID:27284587

  8. Nanostructured and Surface Polymerized Iron Particles for Magnetorheological Fluids

    NASA Astrophysics Data System (ADS)

    Hu, Ben; Fuchs, Alan; Gordaninejad, Faramarz; Evrensel, Cahit

    A novel magnetorheological fluid, in which the surface of iron particles is coated with poly (butyl acrylate) by surface initiated atom transfer radical polymerization (ATRP), is investigated. The polymer coating procedure includes two steps, which are immobilization of initiator: 2-4(-chlorosulfonylphenyl)-ethytrichlorosilane (CTCS) on the iron particles surface and graft polymerization of butyl acrylate from the surface. The surface coating is characterized by FTIR and SEM. This magnetorheological fluid has controllable off-state viscosity and high shear yield stress. Coating polymer on the iron particles surface by ATRP can significantly reduce iron particles settling and improve stability of the MR fluid. Polymerization kinetics of bulk butyl acrylate are investigated using differential scanning calorimetry (DSC). Glass transition temperature is obtained using the step-scan DSC method. The molecular weight and conversion can be controlled by the molar ratio of monomer to initiator, reaction temperature and time. The reaction is first order determined by the plot of In (M/M0) against polymerization time. The overall activation energy is found to be 126kJ/mol by Kissinger's Method.

  9. Polymeric nanoparticles

    PubMed Central

    Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

    2014-01-01

    Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

  10. Dual-color control of nucleotide polymerization sensed by a fluorescence actuator.

    PubMed

    Reimão-Pinto, Madalena M; Cordeiro, Ana; Almeida, Carina; Pinheiro, André V; Moro, Artur; Lima, João C; Baptista, Pedro V

    2014-05-01

    Spatial and temporal control of molecular mechanisms can be achieved using photolabile bonds that connect biomolecules to protective caging groups, which can be cleaved upon irradiation of a specific wavelength, releasing the biomolecule ready-to-use. Here we apply and improve a previously reported strategy to tightly control in vitro transcription reactions. The strategy involves two caging molecules that block both ATP and GTP nucleotides. Additionally, we designed a molecular beacon complementary to the synthesized mRNA to infer its presence through a light signal. Upon release of both nucleotides through a specific monochromatic light (390 and 325 nm) we attain a light signal indicative of a successful in vitro transcription reaction. Similarly, in the absence of irradiation, no intense fluorescence signal was obtained. We believe this strategy could further be applied to DNA synthesis or the development of logic gates. PMID:24604475

  11. High temperature structural, polymeric foams from high internal emulsion polymerization

    SciTech Connect

    Hoisington, M.A.; Duke, J.R.; Apen, P.G.

    1996-02-01

    In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

  12. Kinetically Controlling the Polymerization of Microgels for Synthesis of Silver Nanoparticles in a Confined Space.

    PubMed

    Li, Xianshuai; Ji, Zhen

    2016-06-01

    Controllable synthesis of materials is a dream of scientists, which is closing to the reality after the advancement of fundamental studies. It is generally believed that the structure of materials is controlled by thermodynamics and kinetics. When the materials are formed in a condition far away from equilibrium, the kinetic factors play an important role in shaping materials. The aim of this paper is to evaluate whether the diffusion and reaction also influence the structure of organic materials. We take the preparation of poly(N-isopropylamide) microgels as an example. The diffusion of chemicals is regulated by changing the viscosity of solvents while the reaction is regulated by changing the amount of initiators. It is found that slow diffusion and reaction are in favor of propagation reaction, which leads to the formation of long polymer chains. The microgels composed of these long chains have high swelling ratio. On the other hand, the microgels formed in the high diffusion and reaction consists of shorts chains and demonstrates low swelling ratio. In the followings, we used the microgels as reactor to synthesize silver particles. It is found that the size and the density of silver particles are dependent on the swelling ratio of microgels. This study indicates that controlling chemical diffusion and reaction is a general approach to regulate the structure of materials. PMID:27427622

  13. Preparation and characterization of size-controlled polymeric micelle containing cis-dichlorodiammineplatinum(II) in the core.

    PubMed

    Nishiyama, N; Kataoka, K

    2001-07-01

    Polymeric micelles of varying size in the range of 20 to 100 nm entrapping an antitumor drug, cis-dichlorodiammineplatinum(II) (cisplatin, CDDP), were prepared through the polymer-metal complex formation of CDDP with a mixture of poly(ethylene glycol)-poly(alpha,beta-aspartic acid) block copolymer (PEG-P(Asp)) and poly(alpha,beta-aspartic acid) homopolymer (P(Asp)) with the different feed ratio in distilled water. An increased ratio of P(Asp) to PEG-P(Asp) led to an increase in the micellar size in a controllable manner as well as prolongation in the induction period of the micellar decay accompanied by a sustained release of CDDP in physiological saline at 37 degrees C. All of the CDDP-loaded micelles with a different incorporation ratio of P(Asp) exhibited appreciable in vitro cytotoxicity due to CDDP release from the micelles by prolonged incubation. These CDDP-loaded micelles are expected to have potential utility in tumor-directed delivery system of CDDP through the modulated in vivo biodisposition based on the EPR effect. PMID:11489486

  14. Polymeric hollow spheres assembled from ALG-g-PNIPAM and β-cyclodextrin for controlled drug release.

    PubMed

    Li, Guiying; Yu, Nana; Gao, Yurong; Tao, Qian; Liu, Xunyong

    2016-01-01

    In this paper, thermo-sensitive polymeric hollow spheres assembled from sodium alginate-graft-poly(N-isopropylacrylamide) (ALG-g-PNIPAM) and β-cyclodextrin (β-CD) were prepared for controlled release of 5-fluorouracil (5-FU). In aqueous solutions, β-CD and PNIPAM formed rod-like segments through inclusion complexation interactions and sodium alginate acted as coil segments, which resulted in the formation of hollow structures. The size and wall thickness of assemblies increased with the increase of β-CD in mixtures. The lower critical solution temperature (LCST) of hollow spheres varied in the range of 35-37°C. The hollow spheres exhibited high drug loading efficiency for 5-FU due to the hydrophilic cavities. The initial composition of mixtures, temperature and pH had a significant effect on the inclusion ability and drug release. Increasing temperatures above the LCST or decreasing pH to acidic conditions, a more rapid release rate was observed. PMID:26562555

  15. From the N-Heterocyclic Carbene-Catalyzed Conjugate Addition of Alcohols to the Controlled Polymerization of (Meth)acrylates.

    PubMed

    Ottou, Winnie Nzahou; Bourichon, Damien; Vignolle, Joan; Wirotius, Anne-Laure; Robert, Fredéric; Landais, Yannick; Sotiropoulos, Jean-Marc; Miqueu, Karinne; Taton, Daniel

    2015-06-22

    Among various N-heterocyclic carbenes (NHCs) tested, only 1,3-bis(tert-butyl)imidazol-2-ylidene (NHC(tBu) ) proved to selectively promote the catalytic conjugate addition of alcohols onto (meth)acrylate substrates. This rather rare example of NHC-catalyzed 1,4-addition of alcohols was investigated as a simple means to trigger the polymerization of both methyl methacrylate and methyl acrylate (MMA and MA, respectively). Well-defined α-alkoxy poly(methyl (meth)acrylate) (PM(M)A) chains, the molar masses of which could be controlled by the initial [(meth)acrylate]0/[ROH]0 molar ratio, were ultimately obtained in N,N-dimethylformamide at 25 °C. A hydroxyl-terminated poly(ethylene oxide) (PEO-OH) macro-initiator was also employed to directly access PEO-b-PMMA amphiphilic block copolymers. Investigations into the reaction mechanism by DFT calculations revealed the occurrence of two competitive concerted pathways, involving either the activation of the alcohol or that of the monomer by NHC(tBu) . PMID:26013759

  16. Containerless polymeric microsphere production for biomedical applications

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Hyson, M. T.; Chung, S. K.; Colvin, M.; Chang, M.

    1987-01-01

    A containerless method that produces highly uniform microspheres (greater than 50 microns in diameter) from many materials has been developed for biomedical applications. A piezoelectrically vibrated drop generator forms uniform (monodisperse) monomer droplets that are either electrostatistically levitated and polymerized using UV irradiation, or free-radical polymerized. Spheres of 2-hydroxyethyl methacrylate polymer have been produced with diameters of 155 microns + or - 1.57 percent.

  17. Radical Hysterectomy

    MedlinePlus

    ... the base of her partner’s penis during intercourse. Orgasm after radical hysterectomy Women who have had a ... the surgery will affect their ability to have orgasms. This has not been studied a great deal, ...

  18. Design of polymeric stabilizers for size-controlled synthesis of monodisperse gold nanoparticles in water.

    PubMed

    Wang, Zhenxin; Tan, Bien; Hussain, Irshad; Schaeffer, Nicolas; Wyatt, Mark F; Brust, Mathias; Cooper, Andrew I

    2007-01-16

    A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (approximately 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM. PMID:17209648

  19. Programmable Supramolecular Polymerizations.

    PubMed

    van der Zwaag, Daan; de Greef, Tom F A; Meijer, E W

    2015-07-13

    Living large: Rational design of self-assembly pathways has been demonstrated in supramolecular polymers. By controlling the concentration of an aggregation-competent monomer through intramolecular interactions, living supramolecular polymerization conditions were achieved. This universal approach can be used to obtain aggregates of well-defined length and narrow dispersity, and allows access to new supramolecular polymer architectures. PMID:26095705

  20. Prevention of calcification of glutaraldehyde pretreated bovine pericardium through controlled release polymeric implants: studies of Fe3+, Al3+, protamine sulphate and levamisole.

    PubMed

    Pathak, Y V; Boyd, J; Levy, R J; Schoen, F J

    1990-11-01

    Calcification is the principal cause of the clinical failure of bioprosthetic heart valves fabricated from glutaraldehyde pretreated porcine aortic valves or bovine pericardium. The present study investigated controlled-release implants for prevention of the calcification of glutaraldehyde pretreated bovine pericardium in a rat subdermal model. Either Al3+ and Fe3+ (inhibitors of the growth and dissolution rate of hydroxyapatite crystals), levamisole (alkaline phosphatase inhibitor) or protamine sulphate (charge modifier) were individually incorporated into various polymeric carriers (either silicone rubber, polyurethane or silicone rubber-polyurethane copolymer). Polymeric implants were evaluated for in vitro release kinetics, which revealed that sustained drug release was obtained from 21 d to more than 90 d from various drug matrices. In vivo efficacy was studied by co-implanting the polymeric delivery systems with glutaraldehyde pretreated bovine pericardium for 21 d using a subdermal rat model; glutaraldehyde pretreated bovine pericardium calcium levels were quantitated by atomic absorption spectroscopy in the explanted tissues. Fe3+ and Al3+ polymeric implants were the most effective for inhibiting deposition of calcium mineral. Al3+ demonstrated 82% inhibition of calcification compared to controls and Fe3+ resulted in 80% inhibition of calcification. Specific histologic staining methods showed that Fe3+ and Al3+ were localized within the devitalized cells of the explanted glutaraldehyde pretreated bovine pericardium. No adverse effects on somatic growth or recipient bone morphology were noted following controlled-release drug administration. Controlled release of protamine sulphate or levamisole did not significantly inhibit glutaraldehyde pretreated bovine pericardium calcification. It is concluded that regional controlled release of Fe3+ or Al3+ inhibits glutaraldehyde pretreated bovine pericardium calcification in the rat subdermal model without adverse

  1. Inorganic nanoparticles for the spatial and temporal control of organic reactions: Applications to radical degradation of biopolymer networks

    NASA Astrophysics Data System (ADS)

    Walker, Joan Marie

    Nanoparticles of gold and iron oxide not only possess remarkable optical and magnetic properties, respectively, but are also capable of influencing their local environment with an astounding degree of precision. Using nanoparticles to direct the reactivity of organic molecules near their surface provides a unique method of spatial and temporal control. Enediynes represent an exceptional class of compounds that are thermally reactive to produce a diradical intermediate via Bergman cycloaromatization. While natural product enediynes are famously cytotoxic, a rich chemistry of synthetic enediynes has developed utilizing creative means to control this reactivity through structure, electronics, metal chelation, and external triggering mechanisms. In a heretofore unexplored arena for Bergman cyclization, we have investigated the reactivity of enediynes in connection with inorganic nanoparticles in which the physical properties of the nanomaterial are directly excited to thermally promote aromatization. As the first example of this methodology, gold nanoparticles conjugated with (Z)-octa-4-en-2,6-diyne-1,8-dithiol were excited with 514 nm laser irradiation. The formation of aromatic and polymeric products was confirmed through Raman spectroscopy and electron microscopy. Water soluble analogues Au-PEG-EDDA and Fe3O4-PEG-EDDA (EDDA = (Z)-octa-4-en-2,6-diyne-1,8-diamine) show similar reactivity under laser irradiation or alternating magnetic field excitation, respectively. Furthermore, we have used these functionalized nanoparticles to attack proteinaceous substrates including fibrin and extracellular matrix proteins, capitalizing on the ability of diradicals to disrupt peptidic bonds. By delivering a locally high payload of reactive molecules and thermal energy to the large biopolymer, network restructuring and collapse is achieved. As a synthetic extension towards multifunctional nanoparticles, noble metal seed-decorated iron oxides have also been prepared and assessed for

  2. Pattern formation and control in polymeric systems: From Minkowski measures to in situ AFM imaging

    NASA Astrophysics Data System (ADS)

    Jacobs, Karin

    2014-03-01

    Thin liquid polymer films are not only of great technical importance, they also exhibit a variety of dynamical instabilities. Some of them may be desired, some rather not. To analyze and finally control pattern formation, modern thin film theories are as vital as techniques to characterize the morphologies and structures in and on the films. Examples for the latter are atomic force microscopy (AFM) as well as scattering techniques. The talk will introduce into the practical applications of Minkowski measures to characterize patterns and explain what thin film properties (e.g. capillary number, solid/liquid boundary condition, glass transition temperature, chain mobility) can further be extracted including new technical possibilities by AFM and scattering techniques.

  3. A microfluidic tubing method and its application for controlled synthesis of polymeric nanoparticles.

    PubMed

    Wang, Jidong; Chen, Wenwen; Sun, Jiashu; Liu, Chao; Yin, Qifang; Zhang, Lu; Xianyu, Yunlei; Shi, Xinghua; Hu, Guoqing; Jiang, Xingyu

    2014-05-21

    This report describes a straightforward but robust tubing method for connecting polydimethylsiloxane (PDMS) microfluidic devices to external equipment. The interconnection is irreversible and can sustain a pressure of up to 4.5 MPa that is characterized experimentally and theoretically. To demonstrate applications of this high-pressure tubing technique, we fabricate a semicircular microfluidic channel to implement a high-throughput, size-controlled synthesis of poly(lactic-co-glycolic acid) (PLGA) nanoparticles ranging from 55 to 135 nm in diameter. This microfluidic device allows for a total flow rate of 410 mL h(-1), resulting in enhanced convective mixing which can be utilized to precipitate small size nanoparticles with a good dispersion. We expect that this tubing technique would be widely used in microfluidic chips for nanoparticle synthesis, cell manipulation, and potentially nanofluidic applications. PMID:24675980

  4. Organocatalyzed Group Transfer Polymerization.

    PubMed

    Chen, Yougen; Kakuchi, Toyoji

    2016-08-01

    In contrast to the conventional group transfer polymerization (GTP) using a catalyst of either an anionic nucleophile or a transition-metal compound, the organocatalyzed GTP has to a great extent improved the living characteristics of the polymerization from the viewpoints of synthesizing structurally well-defined acrylic polymers and constructing defect-free polymer architectures. In this article, we describe the organocatalyzed GTP from a relatively personal perspective to provide our colleagues with a perspicuous and systematic overview on its recent progress as well as a reply to the curiosity of how excellently the organocatalysts have performed in this field. The stated perspectives of this review mainly cover five aspects, in terms of the assessment of the livingness of the polymerization, limit and scope of applicable monomers, mechanistic studies, control of the polymer structure, and a new GTP methodology involving the use of tris(pentafluorophenyl)borane and hydrosilane. PMID:27427399

  5. Radiation-induced free radical reactions in polymer/drug systems for controlled release: an EPR investigation

    NASA Astrophysics Data System (ADS)

    Faucitano, A.; Buttafava, A.; Montanari, L.; Cilurzo, F.; Conti, B.; Genta, I.; Valvo, L.

    2003-05-01

    The primary and secondary free radical intermediates in the gamma radiolysis of poly(D,L-lactide-co-glycolide) (PLGA) and clonazepam loaded PLGA microspheres were investigated by matrix EPR spectroscopy in the temperature range 77-298 K. Drug-polymer interactions were found to be important leading to significant deviations of the G(radicals) from the additivity law. In particular, in the mixed system a stabilization of the polymer matrix with respect to the radiation damage was detected, witnessed by a decrease of the overall polymer radicals yield which is accompanied by an increase of the drug radicals yield. These effects have been attributed to the scavenging properties of the nitro group with respect to electrons and polymer radicals. It is conceivable that such conclusions be of general application for all pharmaceutical formulations containing drugs bearing nitro groups in their chemical structure.

  6. Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study

    NASA Technical Reports Server (NTRS)

    Kim, S.; Westmoreland, D.

    1994-01-01

    The propagating radical in the emulsion polymerization reaction of butyl acrylate was detected by Electron Paramagnetic Resonance spectroscopy using two spin trapping agents, 2-methyl-2nitrosopropane and alpha -N-tert-butylnitrone.

  7. Transscleral Controlled Delivery of Geranylgeranylaceton Using a Polymeric Device Protects Rat Retina Against Light Injury.

    PubMed

    Nagai, Nobuhiro; Kaji, Hirokazu; Nishizawa, Matsuhiko; Nakazawa, Toru; Abe, Toshiaki

    2016-01-01

    We evaluated the effects of a transscleral drug delivery device, consisting of a reservoir and controlled-release cover, which were made of photopolymerized polyethylene glycol dimethacrylate and triethylene glycol dimethacrylate, combined at different ratios. Geranylgeranylacetone (GGA), a heat-shock protein (HSP) inducer, was loaded into the device. The GGA was released from the device under zero-order kinetics. At both 1 week and 4 weeks after device implantation on rat sclera, HSP70 gene and protein expression were up-regulated in the sclera-choroid-retinal pigment epithelium fraction of rat eyes treated with the GGA-loaded device compared with rat eyes treated with saline-loaded devices or eyes of non-treated rats. Flash electroretinograms were recorded 4 days after white light exposure (8000 lx for 18 h). Electroretinographic amplitudes of the a- and b-waves were preserved significantly in rats treated with GGA-loaded devices compared with rats treated with saline-loaded devices. Histological examination showed that the outer nuclear layer thickness was preserved in rats that had the GGA-loaded device. These results may show that transscleral GGA delivery using our device may offer an alternative method to treat retinal diseases. PMID:26427448

  8. Polymeric Colloidal Nanostructures Fabricated via Highly Controlled Convective Assembly and Their Use for Molecular Imprinting.

    PubMed

    Yang, Jin Chul; Park, Jin Young

    2016-03-23

    In this work, the formation of various polystyrene (PS) colloidal structures on striped PS patterns is demonstrated based on a simple and novel convective assembly method that controls the electrostatic interactions between the PS colloidal particles and sodium dodecyl sulfate (SDS). Under the optimal conditions (different withdrawal speeds, channel dimensions, suspension concentrations, etc.), highly ordered structures such as highly close-packed, zigzag, and linear colloidal aggregates are observed. In addition, these colloidal arrangements are used for development of molecularly imprinted polymer (MIP) sensors with highly improved sensing properties. Using PDMS replicas, three hemispherical poly(methacrylic acid-ethylene glycol dimethacrylate) (poly(MAA-EGDMA)) MIP films, including planar MIP and non-imprinted polymer (NIP) films, are photopolymerized for detection of trace atrazine in an aqueous solution. From gravimetric quartz crystal microbalance (QCM) measurements, a non-close-packed MIP film exhibits highest sensing response (Δf = 932 Hz) to atrazine detection among hemispherical MIP films and shows 6.5-fold higher sensing response than the planar MIP film. In addition, the sensitivity of the MIP sensor is equivalent to -119 Hz/(mol L(-1)). From the ratio of slopes of the calibration curves for the hemispherical MIP and NIP films, the imprinting factor (If) is as high as 11.0. The hemispherical MIP film also shows excellent selectivity in comparison with the sensing responses of other analogous herbicides. As a result, this molecular surface imprinting using PS colloidal arrays is highly efficient for herbicide detection. PMID:26938141

  9. Endothelial GRK2 regulates vascular homeostasis through the control of free radical oxygen species

    PubMed Central

    Ciccarelli, Michele; Sorriento, Daniela; Franco, Antonietta; Fusco, Anna; Giudice, Carmine Del; Annunziata, Roberto; Cipolletta, Ersilia; Monti, Maria Gaia; Dorn, Gerald W; Trimarco, Bruno; Iaccarino, Guido

    2014-01-01

    Objective The role of endothelial GRK2 was investigated in mice with selective deletion of the kinase in the endothelium (Tie2-CRE/GRK2fl/fl). Approach and Results Aortas from Tie2-CRE/GRK2fl/fl presented functional and structural alterations as compared to control GRK2fl/fl mice. In particular, vasoconstriction was blunted to different agonists, and collagen and elastic rearrangement and macrophage infiltration were observed. In primary cultured endothelial cells deficient for GRK2, mitochondrial reactive oxygen species (ROS) was increased, leading to expression of cytokines. Chronic treatment with a ROS scavenger in mice corrected the vascular phenotype by recovering vasoconstriction, structural abnormalities and reducing macrophage infiltration. Conclusions These results demonstrate that GRK2 removal compromises vascular phenotype and integrity by increasing endothelial ROS production. PMID:23950144

  10. Controle de la morphologie d'hydrogels poreux a partir de structures polymeres

    NASA Astrophysics Data System (ADS)

    Esquirol, Anne-Laure

    This master thesis presents a new fabrication method to prepare hydrogels with fully interconnected and tunable macropore networks prepared with co-continuous polymer blends. The main contributions are: (1) a hydrogel fabrication process providing a high control over the average pore size diameter, their volume fraction and their interconnectivity; (2) the microstructural characterization of porous hydrogels with new techniques such as X-ray microtomography and (3) the preparation of porous gels with industrial equipment such as extruders and injection molding presses. The development and improvement of methods and techniques to prepare porous polymers and porous gels have been intensive areas of research in materials science over the past 20 years because of their potential use in fields as diverse as high performance membranes and filtration devices, supports for catalysis and biochemical reactions, encapsulating devices for drug release, and scaffolds for cells seeding and proliferation. For this last application, in tissue engineering, some typical parameters related to porosity must be rigorously controlled: (1) the average pore size diameter; (2) the pore volume fraction; (3) the pore interconnectivity. Porous hydrogels are excellent candidates due to their similarities with the extracellular matrix (composition, mechanical properties and diffusion properties). A certain number of methods and techniques have been developed and studied to prepare gels comprising microstructured 3-D networks of (more or less) interconnected pores (also called sometimes microfluidic gels or (macro)porous gels). Poly(L-lactide) (PLA) porous materials were realized from immiscible and co-continuous binary blends of polystyrene/poly(L-lactide) (PS/PLA) at 50/50 %vol prepared by different methods : (1) internal mixer (cubic samples with 0.8 mm sides) and (2) extrusion followed by injection molding which allows the fabrication of bars with superior dimensions (0.95 cm x 1.25 cm x 6

  11. Admicellar polymerization and characterization of thin poly(2,2,2-trifluoroethyl acrylate) film on aluminum alloys for in-crevice corrosion control.

    PubMed

    Le, Duc V; Kendrick, Melissa M; O'Rear, Edgar A

    2004-08-31

    Corrosion control of aluminum alloys in the aerospace industry has been of great interest in recent years, especially the aging of certain fleets in the United States Air Force. A thin film of poly(2,2,2-trifluoroethyl acrylate) (PTFEA) has been deposited on aluminum alloy coupons by admicellar polymerization for the purpose of in situ control of corrosion in narrow gaps. Polymerization conditions were chosen based on contact angle measurements, and the final product film was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Surface characterization studies have shown that the polymeric film is approximately 10 nm thick with nonuniform deposition at this scale. The modified surface is highly hydrophobic and able to delay salt solution uptake (3.5 wt % NaCl) for a period of up to 6 h in crevice corrosion tests. PTFEA films reduced the corroded area to 20% compared to 65% for a bare aluminum control and to 33% for poly(methyl methacrylate) (PMMA) film in a 24 h crevice test. PTFEA film exhibits better corrosion protection than PMMA film because it has higher hydrophobicity than a PMMA-modified surface and comparable properties as a corrosion barrier. PMID:15323534

  12. Autoregulation of Free Radicals via Uncoupling Protein Control in Pancreatic β-Cell Mitochondria

    PubMed Central

    Heuett, William J.; Periwal, Vipul

    2010-01-01

    Pancreatic β-cells sense the ambient blood-glucose concentration and secrete insulin to signal other tissues to take up glucose. Mitochondria play a key role in this response as they metabolize nutrients to produce ATP and reactive oxygen species (ROS), both of which are involved in insulin secretion signaling. Based on data available in the literature and previously developed mathematical models, we present a model of glucose-stimulated mitochondrial respiration, ATP synthesis, and ROS production and control in β-cells. The model is consistent with a number of experimental observations reported in the literature. Most notably, it captures the nonlinear rise in the proton leak rate at high membrane potential and the increase in this leak due to uncoupling protein (UCP) activation by ROS. The functional forms used to model ROS production and UCP regulation yield insight into these mechanisms, as many details have not yet been unraveled in the experimental literature. We examine short- and long-term effects of UCP activation inhibition and changes in the mitochondrial density on mitochondrial responses to glucose. Results suggest increasing mitochondrial density while decreasing UCP activity may be an effective way to increase glucose-stimulated insulin secretion while decreasing oxidative stress. PMID:20338842

  13. Controlled trial comparing two types of enteral nutrition in treatment of active Crohn's disease: elemental versus polymeric diet.

    PubMed Central

    Rigaud, D; Cosnes, J; Le Quintrec, Y; René, E; Gendre, J P; Mignon, M

    1991-01-01

    To determine whether an elemental diet or a polymeric defined formula diet would be more effective for treating active Crohn's disease, we conducted a prospective randomised clinical trial in 30 patients with active Crohn's disease unresponsive to steroids and/or complicated by malnutrition. They received a four to six week enteral nutrition course with either an elemental diet or a polymeric diet. Clinical remission occurred in 10 of the 15 patients on elemental diet compared with 11 of the 15 patients assigned to polymeric diet. Both groups showed similar improvements in nutritional status, biological inflammation, alpha 1 antitrypsin clearance, and colonoscopic lesions (diminished in 17 out of 24 patients). Most patients relapsed during the year after discharge. We conclude that enteral nutrition, whatever the diet, is an efficient primary therapy for active Crohn's disease but does not influence the long term outcome. PMID:1773955

  14. Polymerization Simulator for Introductory Polymer and Material Science Courses

    ERIC Educational Resources Information Center

    Chirdon, William M.

    2010-01-01

    This work describes how molecular simulation of polymerization reactions can be used to enrich introductory polymer or material science courses to give students a deeper understanding of free-radical chain and stepwise growth polymerization reactions. These simulations have proven to be effective media for instruction that do not require material…

  15. Surfactant-controlled polymerization of semiconductor clusters to quantum dots through competing step-growth and living chain-growth mechanisms.

    PubMed

    Evans, Christopher M; Love, Alyssa M; Weiss, Emily A

    2012-10-17

    This article reports control of the competition between step-growth and living chain-growth polymerization mechanisms in the formation of cadmium chalcogenide colloidal quantum dots (QDs) from CdSe(S) clusters by varying the concentration of anionic surfactant in the synthetic reaction mixture. The growth of the particles proceeds by step-addition from initially nucleated clusters in the absence of excess phosphinic or carboxylic acids, which adsorb as their anionic conjugate bases, and proceeds indirectly by dissolution of clusters, and subsequent chain-addition of monomers to stable clusters (Ostwald ripening) in the presence of excess phosphinic or carboxylic acid. Fusion of clusters by step-growth polymerization is an explanation for the consistent observation of so-called "magic-sized" clusters in QD growth reactions. Living chain-addition (chain addition with no explicit termination step) produces QDs over a larger range of sizes with better size dispersity than step-addition. Tuning the molar ratio of surfactant to Se(2-)(S(2-)), the limiting ionic reagent, within the living chain-addition polymerization allows for stoichiometric control of QD radius without relying on reaction time. PMID:23009216

  16. Polymerization-Induced Phase Separation in Vinyl Ester Resins

    NASA Astrophysics Data System (ADS)

    Ganglani, Manisha; Torkelson, John; Carr, Stephen

    2000-03-01

    In certain multi-component, crosslinking polymer systems, phase separation is induced by polymerization, a process call polymerization-induced phase separation (PIPS) in which there exists a competition between reaction rate and phase separation rate. The final morphology and properties of a system that experiences PIPS depend on the outcome of this competition. Thus, by controlling these rates, it would be possible to control end properties. In fact, this theory has been applied for the creation of polymer-dispersed liquid crystals (PDLCs) where cure occurs via condensation reactions or via free radical polymerization initiated by UV light. This research examines PIPS in the vinyl ester (VE) resins, which are popular as matrix materials in polymer composites. Cure of the VE resins is more complicated because it uses initiators and therefore requires more time and offers less control than cure by photopolymerization. To better understand the PIPS process in the VE resins, this research separates the two competitive effects and examines each one in turn. Initial experiments use a model system to focus on the effect of PIPS in the absence of crosslinking.

  17. Study of the effect of external heating and internal temperature build-up during polymerization on the morphology of porous polymethacrylate adsorbent

    SciTech Connect

    Wei, Chan Yi Ongkudon, Clarence M. Kansil, Tamar

    2015-07-22

    Modern day synthesis protocols of methacrylate monolithic polymer adsorbent are based on existing polymerization blueprint without a thorough understanding of the dynamics of pore structure and formation. This has resulted in unproductiveness of polymer adsorbent consequently affecting purity and recovery of final product, productivity, retention time and cost effectiveness of the whole process. The problems magnified in monolith scaling-up where internal heat buildup resulting from external heating and high exothermic polymerization reaction was reflected in cracking of the adsorbent. We believe that through careful and precise control of the polymerization kinetics and parameters, it is possible to prepare macroporous methacrylate monolithic adsorbents with controlled pore structures despite being carried out in an unstirred mould. This research involved the study of the effect of scaling-up on pore morphology of monolith, in other words, porous polymethacrylate adsorbents that were prepared via bulk free radical polymerization process by imaging the porous morphology of polymethacrylate with scanning electron microscope.

  18. Study of the effect of external heating and internal temperature build-up during polymerization on the morphology of porous polymethacrylate adsorbent

    NASA Astrophysics Data System (ADS)

    Wei, Chan Yi; Ongkudon, Clarence M.; Kansil, Tamar

    2015-07-01

    Modern day synthesis protocols of methacrylate monolithic polymer adsorbent are based on existing polymerization blueprint without a thorough understanding of the dynamics of pore structure and formation. This has resulted in unproductiveness of polymer adsorbent consequently affecting purity and recovery of final product, productivity, retention time and cost effectiveness of the whole process. The problems magnified in monolith scaling-up where internal heat buildup resulting from external heating and high exothermic polymerization reaction was reflected in cracking of the adsorbent. We believe that through careful and precise control of the polymerization kinetics and parameters, it is possible to prepare macroporous methacrylate monolithic adsorbents with controlled pore structures despite being carried out in an unstirred mould. This research involved the study of the effect of scaling-up on pore morphology of monolith, in other words, porous polymethacrylate adsorbents that were prepared via bulk free radical polymerization process by imaging the porous morphology of polymethacrylate with scanning electron microscope.

  19. Smart Polymeric Nanocarriers of Met-enkephalin.

    PubMed

    Szweda, Roza; Trzebicka, Barbara; Dworak, Andrzej; Otulakowski, Lukasz; Kosowski, Dominik; Hertlein, Justyna; Haladjova, Emi; Rangelov, Stanislav; Szweda, Dawid

    2016-08-01

    This study describes a novel approach to polymeric nanocarriers of the therapeutic peptide met-enkephalin based on the aggregation of thermoresponsive polymers. Thermoresponsive bioconjugate poly((di(ethylene glycol) monomethyl ether methacrylate)-ran-(oligo(ethylene glycol) monomethyl ether methacrylate) is synthesized by AGET ATRP using modified met-enkephalin as a macroinitiator. The abrupt heating of bioconjugate water solution leads to the self-assembly of bioconjugate chains and the formation of mesoglobules of controlled sizes. Mesoglobules formed by bioconjugates are stabilized by coating with cross-linked two-layer shell via nucleated radical polymerization of N-isopropylacrylamide using a degradable cross-linker. The targeting peptide RGD, containing the fluorescence marker carboxyfluorescein, is linked to a nanocarrier during the formation of the outer shell layer. In the presence of glutathione, the whole shell is completely degradable and the met-enkephalin conjugate is released. It is anticipated that precisely engineered nanoparticles protecting their cargo will emerge as the next-generation platform for cancer therapy and many other biomedical applications. PMID:27409457

  20. Core functionalization of semi-crystalline polymeric cylindrical nanoparticles using photo-initiated thiol–ene radical reactions† †Electronic supplementary information (ESI) available: Further methods, polymer and nanostructure characterization. See DOI: 10.1039/c5py01970b Click here for additional data file.

    PubMed Central

    Sun, Liang; Pitto-Barry, Anaïs; Thomas, Anthony W.; Inam, Maria; Doncom, Kay

    2016-01-01

    Sequential ring-opening and reversible addition–fragmentation chain transfer (RAFT) polymerization was used to form a triblock copolymer of tetrahydropyran acrylate (THPA), 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) and l-lactide. Concurrent deprotection of the THPA block and crystallization-driven self-assembly (CDSA) was undertaken and allowed for the formation of cylindrical micelles bearing allyl handles in a short outer core segment. These handles were further functionalized by different thiols using photo-initiated thiol–ene radical reactions to demonstrate that the incorporation of an amorphous PMAC block within the core does not disrupt CDSA and can be used to load the cylindrical nanoparticles with cargo.

  1. Bimorphic polymeric photomechanical actuator

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

    2006-01-01

    A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

  2. High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction

    NASA Astrophysics Data System (ADS)

    Flyunt, Roman; Knolle, Wolfgang; Kahnt, Axel; Halbig, Christian E.; Lotnyk, Andriy; Häupl, Tilmann; Prager, Andrea; Eigler, Siegfried; Abel, Bernd

    2016-03-01

    This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the GO is not excited directly. While the direct photoexcitation of aqueous GO (when GO is the only light-absorbing component) takes several hours of reaction time at ambient temperature (4 h) leading only to a partial GO reduction, the addition of small amounts of isopropanol and acetone (2% and 1%) leads to a dramatically shortened reaction time by more than two orders of magnitude (2 min) and a very efficient and soft reduction of graphene oxide. This method avoids the formation of non-volatile species and in turn contamination of the produced rGO and it is based on the highly efficient generation of reducing carbon centered isopropanol radicals via the reaction of triplet acetone with isopropanol. While the direct photolysis of GO dispersions easily leads to degradation of the carbon lattice of GO and thus to a relatively low electric conductivity of the films of flakes, our indirect photoreduction of GO instead largely avoids the formation of defects, keeping the carbon lattice intact. Mechanisms of the direct and indirect photoreduction of GO have been elucidated and compared. Raman spectroscopy, XPS and conductivity measurements prove the efficiency of the indirect photoreduction in comparison with the state-of-the-art reduction method for GO (hydriodic acid/trifluoroacetic acid). The rapid reduction times and water solvent containing only small amounts of isopropanol and acetone may allow easy process up-scaling for technical applications and low-energy consumption.This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the

  3. High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction.

    PubMed

    Flyunt, Roman; Knolle, Wolfgang; Kahnt, Axel; Halbig, Christian E; Lotnyk, Andriy; Häupl, Tilmann; Prager, Andrea; Eigler, Siegfried; Abel, Bernd

    2016-04-14

    This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the GO is not excited directly. While the direct photoexcitation of aqueous GO (when GO is the only light-absorbing component) takes several hours of reaction time at ambient temperature (4 h) leading only to a partial GO reduction, the addition of small amounts of isopropanol and acetone (2% and 1%) leads to a dramatically shortened reaction time by more than two orders of magnitude (2 min) and a very efficient and soft reduction of graphene oxide. This method avoids the formation of non-volatile species and in turn contamination of the produced rGO and it is based on the highly efficient generation of reducing carbon centered isopropanol radicals via the reaction of triplet acetone with isopropanol. While the direct photolysis of GO dispersions easily leads to degradation of the carbon lattice of GO and thus to a relatively low electric conductivity of the films of flakes, our indirect photoreduction of GO instead largely avoids the formation of defects, keeping the carbon lattice intact. Mechanisms of the direct and indirect photoreduction of GO have been elucidated and compared. Raman spectroscopy, XPS and conductivity measurements prove the efficiency of the indirect photoreduction in comparison with the state-of-the-art reduction method for GO (hydriodic acid/trifluoroacetic acid). The rapid reduction times and water solvent containing only small amounts of isopropanol and acetone may allow easy process up-scaling for technical applications and low-energy consumption. PMID:26984451

  4. [Free oxygen radicals in the pathogenesis of ischemic-reperfusion heart damage and possibilities of its pharmacologic control].

    PubMed

    Jadronová, O; Kuzelová, M; Seginko, J; Svec, P

    1995-10-01

    Due to their molecular configuration, most free radicals are highly reactive and can cause cell injury. The present review deals with the role of oxygen-free radicals (OFR) in the pathogenesis of the heart disease and reperfusion injury. Cellular protection against deleterious effects of OFR is organized at multiple levels. Regulation of the antioxidant capacity includes not only the maintenance of adequate levels of antioxidants but the localisation of antioxidant compounds and enzymes as well. Synthetic antioxidants may mimic biological defence mechanisms. PMID:8520925

  5. ESR study of MMA polymerization by a peroxide/amine system: bone cement formation.

    PubMed

    Oldfield, F F; Yasuda, H K

    1999-03-15

    Electron spin resonance (ESR) spectroscopy was used to gain insight at the molecular level into the curing of bone cement. Methyl methacrylate was polymerized using a N,N-dimethyl-p-toluidine (TD)/benzoyl peroxide (BPO) redox system in the presence of polymethyl methacrylate (PMMA) powder. The conventional nine-line ESR spectrum for the growing polymer radical was detected at the gel stage of polymerization. While the optimum free radical concentration was observed near the equimolar amine/BPO concentration, excess amine led to a change in the chemical structure of the trapped radical and inhibited the polymerization process. At a high amine/BPO ratio the nine-line signal disappeared and a three-line nitroxide-based radical appeared. The appearance of this nitroxide signal seems to depend on the amine/BPO molar ratio and on the presence of PMMA. An excess amount of amine with respect to BPO was found to inhibit the polymerization process. When BPO was removed, the system still polymerized but with a longer gelation time and a lower radical concentration. These results demonstrate that trapped free radicals in the bulk polymerization of MMA convert to polymeric peroxides that act as initiators in bone cement. When the accelerator 4-dimethylamino phenethyl alcohol (TDOH) was used, a higher radical concentration was observed in the polymerizing system. TDOH shows potential for being a more effective accelerator than TD for bone cement curing. PMID:10397948

  6. Flexible particle array structures by controlling polymer graft architecture.

    PubMed

    Choi, Jihoon; Dong, Hongchen; Matyjaszewski, Krzysztof; Bockstaller, Michael R

    2010-09-15

    Surface-initiated atom-transfer radical polymerization is used to synthesize particle brushes with controlled fraction of extended and relaxed conformations of surface-grafted chains. In the semidilute brush limit, the grafting of polymeric ligands is shown to facilitate the formation of ordered yet plastic-compliant particle array structures in which chain entanglements give rise to fracture through a polymer-like crazing process that dramatically increases the toughness and flexibility of the particle assembly. PMID:20726581

  7. Roaming Radicals

    NASA Astrophysics Data System (ADS)

    Bowman, Joel M.; Shepler, Benjamin C.

    2011-05-01

    Roaming is a recently verified unusual pathway to molecular products from unimolecular dissociation of an energized molecule. Here we present the evidence for this pathway for H2CO and CH3CHO. Theoretical analysis shows that this path visits the plateau region of the potential energy surface near dissociation to radical products. It is not clear whether roaming is a distinct isolated pathway, in addition to the conventional one via the well-known molecular saddle-point transition state. Evidence is presented to suggest that the two pathways may originate from a single, but highly complicated, dividing surface. Other examples of unusual reaction dynamics are also reviewed.

  8. Utilizing advanced polymerization techniques for simplifying polymer grafting from silica colloidal crystal substrates

    NASA Astrophysics Data System (ADS)

    Yerneni, Charu K.

    Polyacrylamide has been well established as a biocompatible material when Polyacrylamide gel electrophoresis (PAGE) came into existence in the 1960s. Under aqueous buffer conditions it becomes non-adsorptive to proteins and due to its molecular level pore forming nature could be used in size based biomolecule separations. Since then considerable research has been done to explore the non-adsorptive nature of polyacrylamide on a platform or substrate. Attempts were made to grow polyacrylamide chains from silica as a substrate which can then be used in various protein separation techniques. Based on an ionic polymerization method which was used for gel casting in PAGE, polymers were grown on silica gel. Though considerable thickness could be achieved, polymerization was not just confined to the surface. Therefore a rigid polymer brush layer could not be achieved. Atom transfer radical polymerization (ATRP) method showed the solution to this problem. Polymer brush layers with acceptable thickness could now be achieved for growing polyacrylamide from silica gel. Yet it still suffered from several disadvantages such as the need of an inert atmosphere for polymerization and limited thickness. Many developments have taken place in the past decade which led to improvements in substrate and polymerization methods. This research used non porous sub-micron silica as the substrate and AGET ATRP (Activator generated electron transfer atom transfer radical polymerization) for surface grafting polyacrylamide. Non porous submicron silica has been shown to be a better stationary phase substrate for protein separations than conventional substrates. AGET ATRP enables polymerization to be performed under ambient conditions and in water based solutions which gives thicknesses much higher than conventional ATRP. Data from various analytical techniques showed that within the experimental range the polymerization is linear and has decent control. This means silica nanoparticles coated with

  9. Differences in porous characteristics of styrenic monoliths prepared by controlled thermal polymerization in molds of varying dimensions.

    PubMed

    Byström, Emil; Viklund, Camilla; Irgum, Knut

    2010-02-01

    Nitroxide-mediated polymerization was used as a model system for preparing styrenic monolithic materials with significant mesopore contents in different mold formats, with the aim of assessing the validity of pore characterization of capillary monoliths by analysis of parallel bulk polymerized precursor solution. Capillary monoliths were prepared in 250 microm id fused silica tubes (quadruplicate samples, in total 17 m), and the batch polymerizations were carried out in parallel in 100 microL microvials and regular 2 mL glass vials, both in quintuplicate. The monoliths recovered from the molds were characterized for their meso- and macroporous properties by nitrogen sorptiometry (three repeated runs on each sample), followed by a single analysis by mercury intrusion porosimetry. A total of 14 monolith samples were thus analyzed. A Grubbs' test identified one regular vial sample as an outlier in the sorptiometric surface area measurements, and data from this sample were consequently excluded from the pore size calculations, which are based on the same nitrogen sorption data, and also from the mercury intrusion data set. The remaining data were subjected to single factor analyses of variance analyses to test if the porous properties of the capillary monoliths were different from those of the bulk monoliths prepared in parallel. Significant differences were found between all three formats both in their meso- and macroporous properties. When the dimension was shrunk from conventional vial to capillary size, the specific surface area decreased from 52.2+/-4.7 to 34.6+/-1.7 m(2)/g. This decrease in specific surface area was accompanied by a significant shift in median diameter of the through-pores, from 310+/-3.9 to 544+/-13 nm. None of these differences were obvious from the scanning electron micrographs that were acquired for each sample type. The common practice of determining the mesopore characteristics from analysis of samples prepared by parallel bulk

  10. Role of radiolytically generated species in radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution: Steady state and pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Y. K.; Mohan, H.; Sabharwal, S.; Majali, A. B.

    2000-06-01

    Radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution has been investigated by steady state and pulse radiolysis techniques. Effect of dose, dose rate, monomer concentration, pH and ambient conditions on polymerization was investigated. The reactions of primary radicals of water radiolysis such as OH radical, e -aq, H atom, O rad - and some oxidizing radicals like N rad 3, Cl rad -2,Br rad -2, and reducing specie like CO rad -2 with SSS have also been investigated. SSS reacts with OH radical with a rate constant of 5.9×10 9 dm 3 mol -1s -1 at pH 6.3. The results indicate that ˜83% of OH radicals undergo electron transfer reaction resulting in a cation radical species while remaining ˜17% react via addition reaction. The hydrated electron reacts with SSS with a rate constant 1.3×10 10 dm 3 mol -1 s -1 to form an anion that undergoes fast protonation to form H-adduct at pH 6.3. At high pH (>10) the anion is able to transfer electron to methyl vilogen and p-nitro aceto phenone ( p-NAP) where as H-adduct is unable to transfer electron. At pH ˜1 H atom reaction with SSS is diffusion controlled with a rate constant of 5×10 9 dm 3 mol -1 s -1 and results in formation of H adduct. It was seen that anion reacts with solute an order faster than cation generated radiolytically indicating anionic initiation of polymerization of SSS. Molecular weight of the polymer formed by radiation polymerization, determined by viscosity measurement, are of the order of 10 7 and higher molecular weight polymers are obtained at lower dose rates. In presence of a crosslinking agent gelation of polymer is much faster than the monomer and a polymer concentration ˜20% is most efficiently crosslinked.

  11. Polymerization in the gas phase, in clusters, and on nanoparticle surfaces.

    PubMed

    El-Shall, M Samy

    2008-07-01

    Gas phase and cluster experiments provide unique opportunities to quantitatively study the effects of initiators, solvents, chain transfer agents, and inhibitors on the mechanisms of polymerization. Furthermore, a number of important phenomena, unique structures, and novel properties may exist during gas-phase and cluster polymerization. In this regime, the structure of the growing polymer may change dramatically and the rate coefficient may vary significantly upon the addition of a single molecule of the monomer. These changes would be reflected in the properties of the oligomers deposited from the gas phase. At low pressures, cationic and radical cationic polymerizations may proceed in the gas phase through elimination reactions. In the same systems at high pressure, however, the ionic intermediates may be stabilized, and addition without elimination may occur. In isolated van der Waals clusters of monomer molecules, sequential polymerization with several condensation steps can occur on a time scale of a few microseconds following the ionization of the gas-phase cluster. The cluster reactions, which bridge gas-phase and condensed-phase chemistry, allow examination of the effects of controlled states of aggregation. This Account describes several examples of gas-phase and cluster polymerization studies where the most significant results can be summarized as follows: (1) The carbocation polymerization of isobutene shows slower rates with increasing polymerization steps resulting from entropy barriers, which could explain the need for low temperatures for the efficient propagation of high molecular weight polymers. (2) Radical cation polymerization of propene can be initiated by partial charge transfer from an ionized aromatic molecule such as benzene coupled with covalent condensation of the associated propene molecules. This novel mechanism leads exclusively to the formation of propene oligomer ions and avoids other competitive products. (3) Structural information

  12. Polymeric amphiphilic nanoparticles via intramolecular chain collapse using 1-functionalized vinylbenzocyclobutenes

    NASA Astrophysics Data System (ADS)

    Storms, William Kenneth

    Synthetic routes to 1-functionalized 4-vinylbenzocyclobutenes were developed with cyano, ester, amide and acetoxy 1-functional groups. The synthesis of a high molecular weight diblock quaterpolymer (i.e. two block, with two monomers in each block), where the blocks were highly immiscible (hydrocarbon / aliphatic fluorocarbon) and each contained a thermal crosslinker with a distinct curing temperature range, i.e. a "low" temperature crosslinker and a "high" temperature crosslinker by sequential polymerization using controlled radical polymerization was investigated. The synthesis of the desired diblock quaterpolymer was difficult or impossible due to radical chain transfer to 1-ethoxybenzocylcobutene. Fast chain-transfer to 1-ethoxybenzocyclobutene caused the polymerization to be inefficient and poorly controlled. Using a combination of ATRP and post-polymerization functionalization via the nucleophilic aromatic substitution of poly(pentafluorostyrene), a modular route to a strongly phase segregating benzocyclobutene functional diblock quaterpolymer was established. A linear diblock quaterpolymer was collapsed in two steps under pseudo-high dilution conditions into an amphiphilic single chain nanoparticle. Characterization of the soft organic particles by GPC, 1H- and 19F-NMR spectroscopy, atomic force microscopy, and transmission electron microscopy confirmed that they were single-chain particles. As part of a plan to possibly prepare the desired strongly phase segregating diblock copolymers by polymer-polymer conjugation using copper catalyzed azide-alkyne cycloaddition, the ATRP of styrene initiated from the popular alkyne functional initiator, prop-2-yn-1-yl 2-brom-2-methylpropanoate (PBiB), was systematically investigated. Using polymerization studies of PBiB a non-degenerative chain coupling side reaction was shown to be occurring. By repeating this study with similar protected alkyne functional ATRP initiators the side reaction was shown to be occurring due

  13. Novel hybrid polymeric materials for barrier coatings

    NASA Astrophysics Data System (ADS)

    Pavlacky, Erin Christine

    . The novel preparation of hybrid films coupling the advantageous properties of organic-inorganic hybrids formed through sol-gel chemistry with polymer-clay nanocomposite technology was also explored. Alkoxysilane-functional copolymer-clay nanocomposites were first synthesized, followed by crosslinking via simultaneous hydrolysis and condensation reactions to create the novel hybrid barrier films. By dispersing organomodified clay throughout the hybrid network, dramatic improvements in several film properties were observed, particularly regarding the viscoelastic properties. Additional studies with the same organic-inorganic preparation technique were performed to incorporate amine-functionality into the hybrid film for potential applications as protective membranes in carbon dioxide capture and separation technologies. Finally, controlled free-radical polymerization techniques were combined with the preparation of the organic-inorganic hybrids.

  14. Clinical comparison of laparoscopy vs open surgery in a radical operation for rectal cancer: A retrospective case-control study

    PubMed Central

    Huang, Chen; Shen, Jia-Cheng; Zhang, Jing; Jiang, Tao; Wu, Wei-Dong; Cao, Jun; Huang, Ke-Jian; Qiu, Zheng-Jun

    2015-01-01

    AIM: To assess the diverse immediate and long-term clinical outcomes, a retrospective comparison between laparoscopic and conventional operation was performed. METHODS: A total number of 916 clinical cases, from January 2006 to December 2013 in our hospital, were analyzed which covered 492 patients underwent the laparoscopy in radical resection (LRR) and 424 cases in open radical resection (ORR). A retrospective analysis was proceeded by comparing the general information, surgery performance, pathologic data, postoperative recovery and complications as well as long-term survival to investigate the diversity of immediate and long-term clinical outcomes of laparoscopic radical operation. RESULTS: There were no statistically significance differences between gender, age, height, weight, body mass index (BMI), tumor loci, tumor node metastasis stages, cell differentiation degree or American Society of Anesthesiologists scores of the patients (P > 0.05). In contrast to the ORR group, the LRR group experienced less operating time (P < 0.001), a lower blood loss (P < 0.001), and had a 2.44% probability of conversion to open surgery. Postoperative bowel function recovered more quickly, analgesic usage and the average hospital stay (P < 0.001) were reduced after LRR. Lymph node dissection during LRR appeared to be slightly more than in ORR (P = 0.338). There were no obvious differences in the lengths and margins (P = 0.182). And the occurrence rate in the two groups was similar (P = 0.081). Overall survival rate of ORR and LRR for 1, 3 and 5 years were 94.0% and 93.6% (P = 0.534), 78.1% and 80.9% (P = 0.284) and 75.2% and 77.0% (P = 0.416), respectively. CONCLUSION: Laparoscopy as a radical operation for rectal cancer was safe, produced better immediate outcomes. Long-term survival of laparoscopy revealed that it was similar to the open operation. PMID:26730165

  15. Development of mechano-responsive polymeric scaffolds using functionalized silica nano-fillers for the control of cellular functions.

    PubMed

    Griffin, Michelle; Nayyer, Leila; Butler, Peter E; Palgrave, Robert G; Seifalian, Alexander M; Kalaskar, Deepak M

    2016-08-01

    We demonstrate an efficient method to produce mechano-responsive polymeric scaffolds which can alter cellular functions using two different functionalized (OH and NH2) silica nano-fillers. Fumed silica-hydroxyl and fumed silica-amine nano-fillers were mixed with a biocompatible polymer (POSS-PCU) at various wt% to produce scaffolds. XPS and mechanical testing demonstrate that bulk mechanical properties are modified without changing the scaffold's surface chemistry. Mechanical testing showed significant change in bulk properties of POSS-PCU scaffolds with an addition of silica nanofillers as low as 1% (P<0.01). Scaffolds modified with NH2 silica showed significantly higher bulk mechanical properties compared to the one modified with the OH group. Enhanced cell adhesion, proliferation and collagen production over 14days were observed on scaffolds with higher bulk mechanical properties (NH2) compared to those with lower ones (unmodified and OH modified) (P<0.05) during in vitro analysis. This study provides an effective method of manufacturing mechano-responsive polymeric scaffolds, which can help to customize cellular responses for biomaterial applications. PMID:27013128

  16. Observation of steric hindrance effect controlling crystal packing structures and physical properties in three new isomeric nitronyl nitroxide radicals

    NASA Astrophysics Data System (ADS)

    Zhao, Hai-Rong; Sun, Jia-Sen; Sui, Yun-Xia; Ren, Xiao-Ming; Yao, Bin-Qian; Shen, Lin-Jiang; Meng, Qing-Jin

    2009-07-01

    Three isomeric nitronyl nitroxide radical compounds, 2-[ n-( N-benzyl)pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide bromide ( n = 2, 3 and 4 for 1, 2 and 3, respectively), have been synthesized and structurally characterized. The influence of steric hindrance on the molecular packing structures and physical properties has been observed. In the radical 1, such steric hindrance leads to a folding conformation of the imidazoline and benzene rings and the intramolecular C-H…π interaction between the methyl group and the benzene ring. There is no such effect in 2 and 3. In crystal of 2, there are the intermolecular C-H…π between methyl groups and benzene ring and intermolecular π…π stacking interaction between pyridine and benzene rings. Crystal of 2 with a chiral space group P2 12 12 1 shows the SHG response about 0.4 times as that of urea. In crystal of 3, there are three symmetry-independent radical molecules, which form an unusually six-membered supramolecular ring via intermolecular O…π interactions. For the solid sample of 3, the X-band EPR exhibits an axially symmetric signal and magnetic susceptibility data suggest intermolecular antiferromagnetic (AFM) coupling interactions and very weak intermolecular ferromagnetic (FM) coupling interactions which is more likely caused by magnetic anisotropy, while measurements of both 1 and 2 show isotropic X-band EPR signals and simple Currie-Weiss magnetic behavior.

  17. A fluorescent immunosensor for high-sensitivity cardiac troponin I using a spatially-controlled polymeric, nano-scale tracer to prevent quenching.

    PubMed

    Seo, Sung-Min; Kim, Seung-Wan; Park, Ji-Na; Cho, Jung-Hwan; Kim, Hee-Soo; Paek, Se-Hwan

    2016-09-15

    For detection of high-sensitivity cardiac troponin I (hs-cTnI<0.01ng/mL), signal amplification was attained using a rapid immunosensor with a fluorescently-labeled, polymeric detection antibody. As fluorescent molecules tend to quench when they are less than 10nm apart, a synthetic scheme for the labeled antibody was devised to control the molecular distance and so minimize the quenching effect in a single conjugate unit. To this end, we first performed novel polymerization of fluorophore-coupled streptavidin (FL-SA) with biotinylated detection antibody (b-Ab) in a stepwise manner by adding FL-SA to b-Ab five times sequentially. Relative spatial positions of the fluorophore molecules in the polymer were then distally fixed using di-biotinylated oligonucleotides and passed through a 0.45µm filter to obtain a polymer of uniform size (i.e., ~400nm in diameter). We produced polymeric tracers using two different inexpensive fluorophores, Dylight 650 and Alexa 647, and applied it to the detection of hs-cTnI spiked in human serum using a two-dimensional chromatography-based immunosensor. The tracers showed a limit of detection of 0.002ng/mL for Dylight 650 and 0.007ng/mL for Alexa 647. The standard curves linearized via log-logit transformation exhibited regression lines with correlation coefficients (R(2))>0.97. The total coefficient of variation for the overall standard curve was 3.4±3.3% for the Dylight fluorophore and 5.9±1.5% for the Alexa dye. Such performances were comparable to those of the reference systems employing sophisticated technologies, Pathfast (Mitsubishi, Japan) and i-STAT (Abbott, US), with a strong correlation (R(2)>0.91) for the concentration range <100pg/mL. PMID:27093486

  18. A prospective randomised controlled trial of laparoscopic vs open radical cystectomy for bladder cancer: perioperative and oncologic outcomes with 5-year follow-upT Lin et al

    PubMed Central

    Lin, T; Fan, X; Zhang, C; Xu, K; Liu, H; Zhang, J; Jiang, C; Huang, H; Han, J; Yao, Y; Xie, W; Dong, W; Bi, L; Huang, J

    2014-01-01

    Background: Laparoscopic radical cystectomy (LRC) is increasingly being used for muscle-invasive bladder cancer. However, high levels of clinical evidence comparing laparoscopic vs open radical cystectomy (ORC) are lacking. Methods: A prospective randomised controlled clinical trial comparing LRC vs ORC in patients undergoing radical cystectomy for bladder cancer. Thirty-five patients were eligible for final analysis in each group. Results: The median follow-up was 26 months (range, 4–59 months) for laparoscopic vs 32 months (range, 6–60 months) for ORC. Significant differences were noted in operative time, estimated blood loss (EBL), blood transfusion rate, analgesic requirement, and time to resumption of oral intake. No significant differences were noted in the length of hospital stay, complication rate, lymph node yield (14.1±6.3 for LRC and 15.2±5.9 for ORC), positive surgical margin rate, postoperative pathology, or recurrence rate (7 for LRC and 8 for ORC). The 5-year recurrence-free survival with laparoscopic vs ORC was 78.5% vs 70.9%, respectively (P=0.773). The overall survival with laparoscopic vs ORC was 73.8% vs 67.4%, respectively (P=0.511). Conclusion: Our study demonstrated that LRC is superior to ORC in perioperative outcomes, including EBL, blood transfusion rate, and analgesic requirement. We found no major difference in oncologic outcomes. The number of patients is too small to allow for a final conclusion. PMID:24407192

  19. A new redox-dependent mechanism of MMP-1 activity control comprising reduced low-molecular-weight thiols and oxidizing radicals.

    PubMed

    Koch, Sabine; Volkmar, Christine M; Kolb-Bachofen, Victoria; Korth, Hans-Gert; Kirsch, Michael; Horn, Anselm H C; Sticht, Heinrich; Pallua, Norbert; Suschek, Christoph V

    2009-03-01

    Matrix metalloproteinases (MMPs), a family of zinc-dependent proteinases, participate in remodeling and degradation of the extracellular matrix proteins. The activity of MMPs is thought to be predominately posttranslationally regulated via proteolytic activation of precursor zymogens or via their naturally occurring endogenous inhibitors. Here, using recombinant MMP-1, we investigated new redox-dependent mechanisms of proteinase activity regulation by low-molecular-weight thiols. We find that glutathione (GSH), cysteine, homocysteine, and N-acetylcysteine at physiological concentrations competitively reduce MMP-1 activity up to 75% with an efficiency of cysteine > or = GSH > homocysteine > N-acetylcysteine. In contrast, S-derivatized thiols completely lack this inhibitory activity. Interestingly, the competitive GSH-mediated inhibition of MMP-1-activity can be fully reversed abrogated by oxidizing radicals like (*)NO(2) or Trolox radicals, here generated by UVA irradiation of nitrite or Trolox, two relevant agents in human skin physiology. This redox-dependent reactivation of the inactive GSH-MMP-1-complex comprises GSH oxidation and is significantly inhibited in the presence of ascorbic acid, an effective (*)NO(2) and Trolox radical scavenger. We here offer a new concept of redox-sensitive control of MMP-1 activity based on the inhibitory effect of reduced thiols and reactivation by a mechanism comprising derivatization or oxidation of the MMP-1-bound inhibitory-acting thiol. PMID:19034402

  20. PEG based hyperbranched polymeric hollow nanospheres

    NASA Astrophysics Data System (ADS)

    Cao, Hongliang; Dong, Yixiao; O'Rorke, Suzanne; Wang, Wenxin; Pandit, Abhay

    2011-02-01

    The synthesis of a new PEG based hyperbranched copolymer of poly(ethylene glycol) methyl ether methacrylate-co-ethylene glycol dimethacrylate (PEGMEMA-co-EGDMA) was achieved via a one-step in situ deactivation enhanced atom transfer radical polymerization (DE-ATRP). Then, hollow PEG based nanospheres were fabricated from this polymer using a solvent evaporation method and post-stabilisation strategy. Furthermore, the analysis using a cellular metabolic activity assay proved that the copolymer did not affect cellular metabolism, indicating that this PEG based polymeric nanosphere has potential for use in drug delivery applications.

  1. Controlled release of dual drug-loaded hydroxypropyl methylcellulose matrix tablet using drug-containing polymeric coatings.

    PubMed

    Lee, B J; Ryu, S G; Cui, J H

    1999-10-15

    A dual drug-loaded hydroxypropylmethylcellulose (HPMC) matrix tablet simultaneously containing drug in inner tablet core and outer coated layer was formulated using drug-containing aqueous-based polymeric Eudragit RS30D dispersions. Effects of coating levels, drug loadings in outer layers, amount and type of five plasticizers and talc concentration on the release characteristics were evaluated on the characteristics in simulated gastric fluid for 2 h followed by a study in intestinal fluids. Melatonin (MT) was selected as a model drug. The surface morphology of dual drug-loaded HPMC tablets using scanning electron microscope (SEM) was smooth, showing the distinct coated layer with about 75-microm coating thickness at the 15% coating level. Unlike the uncoated and conventionally coated HPMC tablet, the dual drug-loaded HPMC matrix tablet gave a biphasic linear release, showing a zero-order for 4 h (first) followed by another zero-order release when fitted using linear regression (r(2) = 0.99). As the coating levels (15, 25%) increased, the release rate was further decreased. The biphasic release profiles of dual drug-loaded HPMC matrix tablet was unchanged except when 25% coating level containing 0.5% drug concentration was applied. As the drug concentration in polymeric coating dispersion increased (0.25-1.0%), the amount of drug released increased. The time for the first linear release was also advanced. However, the biphasic release pattern was not changed. The biphasic release profiles of dual drug-loaded HPMC matrix tablet were highly modified, depending on the amount and type of five plasticizers. Talc (10-30%) in coating dispersion as an anti-sticking material did not affect the release profiles. The current dual drug-loaded HPMC matrix tablet, showing biphasic release profiles may provide an alternative to deliver drugs with circadian rhythmic behaviors in the body but needs to be further validated in future in human studies. The dual drug-loaded coating

  2. Synthesis of temperature-responsive poly(N-isopropyl acrylamide)/poly(methyl methacrylate)/silica hybrid capsules from inverse pickering emulsion polymerization and their application in controlled drug release.

    PubMed

    Zhang, Kui; Wu, Wei; Guo, Kai; Chen, Jianfeng; Zhang, Pengyuan

    2010-06-01

    Poly(N-isopropylacrylamide)/poly(methyl methacrylate)/silica hybrid capsules were prepared from inverse Pickering emulsion polymerization. A N-isopropylacrylamide aqueous solution was emulsified into an oil phase containing methyl methacrylate and divinyl benzene by sonication to obtain a W/O Pickering emulsion using modified silica nanoparticles as stabilizers. After the emulsion was polymerized, the hybrid capsules were obtained. The capsule wall contained two layers--a solid particle monolayer and a polymer layer--and the wall thickness could be controlled by adjusting the methyl methacrylate and divinyl benzene concentrations in the continuous oil phase before polymerization. The as-synthesized capsules exhibited temperature-responsive properties. The controlled release experiments showed that the release rate of a model drug from the hybrid capsules could be controlled by adjusting the wall thickness of the capsule or the temperature of the release medium. PMID:20178344

  3. A material’s point of view on recent developments of polymeric biomaterials: control of mechanical and biochemical properties

    PubMed Central

    Gribova, Varvara; Crouzier, Thomas; Picart, Catherine

    2014-01-01

    Cells respond to a variety of stimuli, including biochemical, topographical and mechanical signals originating from their micro-environment. Cell responses to the mechanical properties of their substrates have been increasingly studied for about 14 years. To this end, several types of materials based on synthetic and natural polymers have been developed. Presentation of biochemical ligands to the cells is also important to provide additional functionalities or more selectivity in the details of cell/material interaction. In this review article, we will emphasize the development of synthetic and natural polymeric materials with well-characterized and tunable mechanical properties. We will also highlight how biochemical signals can be presented to the cells by combining them with these biomaterials. Such developments in materials science are not only important for fundamental biophysical studies on cell/material interactions but also for the design of a new generation of advanced and highly functional biomaterials. PMID:25067892

  4. Superabsorbent hydrogels via graft polymerization of acrylic acid from chitosan-cellulose hybrid and their potential in controlled release of soil nutrients.

    PubMed

    Essawy, Hisham A; Ghazy, Mohamed B M; El-Hai, Farag Abd; Mohamed, Magdy F

    2016-08-01

    Superabsorbent polymers fabricated via grafting polymerization of acrylic acid from chitosan (CTS) yields materials that suffer from poor mechanical strength. Hybridization of chitosan with cellulose (Cell) via chemical bonding using thiourea formaldehyde resin increases the flexibility of the produced hybrid (CTS/Cell). The hybridization process and post graft polymerization of acrylic acid was followed using Fourier transform infrared (FTIR). Also, the obtained structures were homogeneous and exhibited uniform surface as could be shown from imaging with scanning electron microscopy (SEM). Thus, the polymers derived from the grafting of polyacrylic acid from (CTS/Cell) gave rise to much more mechanically robust structures ((CTS/Cell)-g-PAA) that bear wide range of pH response due to presence of chitosan and polyacrylic acid in one homogeneous entity. Additionally, the obtained structures possessed greater water absorbency 390, 39.5g/g in distilled water and saline (0.9wt.% NaCl solution), respectively, and enhanced retention potential even at elevated temperatures as revealed by thermogravimetric analysis (TGA). This could be explained by the high grafting efficiency (GE%), 86.4%, and grafting yield (GY%), 750%. The new superabsorbent polymers proved to be very efficient devices for controlled release of fertilizers into the soil which expands their use in agriculture and horticultural applications. PMID:27126169

  5. Laser-ignited frontal polymerization of shape-controllable poly(VI-co-AM) hydrogels based on 3D templates toward adsorption of heavy metal ions

    NASA Astrophysics Data System (ADS)

    Fan, Suzhen; Liu, Sisi; Wang, Xiao-Qiao; Wang, Cai-Feng; Chen, Su

    2016-06-01

    Given the increasing heavy metal pollution issue, fast preparation of polymeric hydrogels with excellent adsorption property toward heavy metal ions is very attractive. In this work, a series of poly( N-vinylimidazole-co-acrylamide) (poly(VI-co-AM)) hydrogels were synthesized via laser-ignited frontal polymerization (LIFP) for the first time. The dependence of frontal velocity and temperature on two factors monomer ratios and initiator concentrations was systematically investigated. Poly(VI-co-AM) hydrogels with any self-supporting shapes can be synthesized by a one-step LIFP in seconds through the application of 3D templates. These shape-persistent hydrogels are pH-responsive and exhibit excellent adsorption/desorption characteristics toward Mn(II), Zn(II), Cd(II), Ni(II), Cu(II) and Co(II) ions, and the adsorption conformed to the pseudo-second-order kinetic model. The reusability of the hydrogels toward mental ions adsorption was further researched, which suggested that the hydrogels can be reused without serious decrease in adsorption capacity. This work might open a promising strategy to facilely prepare shape-controllable hydrogels and expand the application of LIFP.

  6. Ultrasound-Mediated Polymeric Micelle Drug Delivery.

    PubMed

    Xia, Hesheng; Zhao, Yue; Tong, Rui

    2016-01-01

    The synthesis of multi-functional nanocarriers and the design of new stimuli-responsive means are equally important for drug delivery. Ultrasound can be used as a remote, non-invasive and controllable trigger for the stimuli-responsive release of nanocarriers. Polymeric micelles are one kind of potential drug nanocarrier. By combining ultrasound and polymeric micelles, a new modality (i.e., ultrasound-mediated polymeric micelle drug delivery) has been developed and has recently received increasing attention. A major challenge remaining in developing ultrasound-responsive polymeric micelles is the improvement of the sensitivity or responsiveness of polymeric micelles to ultrasound. This chapter reviews the recent advance in this field. In order to understand the interaction mechanism between ultrasound stimulus and polymeric micelles, ultrasound effects, such as thermal effect, cavitation effect, ultrasound sonochemistry (including ultrasonic degradation, ultrasound-initiated polymerization, ultrasonic in-situ polymerization and ultrasound site-specific degradation), as well as basic micellar knowledge are introduced. Ultrasound-mediated polymeric micelle drug delivery has been classified into two main streams based on the different interaction mechanism between ultrasound and polymeric micelles; one is based on the ultrasound-induced physical disruption of the micelle and reversible release of payload. The other is based on micellar ultrasound mechanochemical disruption and irreversible release of payload. PMID:26486348

  7. Smart pH-sensitive and temporal-controlled polymeric micelles for effective combination therapy of doxorubicin and disulfiram.

    PubMed

    Duan, Xiaopin; Xiao, Jisheng; Yin, Qi; Zhang, Zhiwen; Yu, Haijun; Mao, Shirui; Li, Yaping

    2013-07-23

    The combination of a chemotherapeutic drug with a multidrug resistance (MDR) modulator has emerged as a promising strategy for treating MDR cancer. To ensure two drugs could be simultaneously delivered to tumor region at the optimum ratio, and the MDR modulator could be released earlier and faster than the chemotherapeutic drug to inactivate P-glycoprotein (P-gp) and subsequently inhibit the pumping out of the chemotherapeutic drug, a smart pH-sensitive polymeric micelles system with high drug loading and precise drug ratio was designed and prepared by conjugating doxorubicin (DOX) to poly(styrene-co-maleic anhydride) (SMA) derivative with adipic dihydrazide (ADH) through a acid-cleavable hydrazone bond, and then encapsulating disulfiram (DSF), a P-gp inhibitor as well as an apoptosis inducer, into the micelles formed by the self-assembly of SMA-ADH-DOX (SAD) conjugate. The pH-sensitive polymeric micelles system enabled a temporal release of two drugs: encapsulated DSF was released fast to inhibit the activity of P-gp and restore cell apoptotic signaling pathways, while conjugated DOX was released in a sustained and pH-dependent manner and highly accumulated in drug resistant cells to exert therapeutic effect, due to the inactivation of P-gp by DSF. The smart co-delivery system was very effective in enhancing the cytotoxicity by increasing the intracellular accumulation of DOX and promoting the apoptotic response, and showed the most effective inhibitory effect on the growth of drug-resistant breast cancer xenografts as compared to other combinations of both drugs. In a word, this smart co-delivery system has significant promise for the clinical therapy of MDR cancer. PMID:23734880

  8. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

  9. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen

    1995-01-01

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

  10. Precision synthesis of functional materials via RAFT polymerization and click-type chemical reactions

    NASA Astrophysics Data System (ADS)

    Flores, Joel Diez

    2011-12-01

    The need to tailor polymeric architectures with specific physico-chemical properties via the simplest, cleanest, and most efficient synthetic route possible has become the ultimate goal in polymer synthesis. Recent progress in macromolecular science, such as the discoveries of controlled/"living" free radical polymerization (CRP) methods, has brought about synthetic capabilities to prepare (co)polymers with advanced topologies, predetermined molecular weights, narrow molecular weight distributions, and precisely located functional groups. In addition, the establishment of click chemistry has redefined the selected few highly efficient chemical reactions that become highly useful in post-polymerization modification strategies. Hence, the ability to make well-defined topologies afforded by controlled polymerization techniques and the facile incorporation of functionalities along the chain via click-type reactions have yielded complex architectures, allowing the investigation of physical phenomena which otherwise could not be studied with systems prepared via conventional methods. The overarching theme of the research work described in this dissertation is the fusion of the excellent attributes of reversible addition-fragmentation chain transfer (RAFT) polymerization method, which is one of the CRP techniques, and click-type chemical reactions in the precision of synthesis of advanced functional materials. Chapter IV is divided into three sections. In Section I, the direct RAFT homopolymerization of 2-(acryloyloxy)ethyl isocyanate (AOI) and subsequent post-polymerization modifications are described. The polymerization conditions were optimized in terms of the choice of RAFT chain transfer agent (CTA), polymerization temperature and the reaction medium. Direct RAFT polymerization of AOI requires a neutral CTA, and relatively low reaction temperature to yield AOI homopolymers with low polydispersities. Efficient side-chain functionalization of PAOI homopolymers was

  11. Secondary Interaction Interfaces with PCNA Control Conformational Switching of DNA Polymerase PolB from Polymerization to Editing.

    PubMed

    Xu, Xiaojun; Yan, Chunli; Kossmann, Bradley R; Ivanov, Ivaylo

    2016-08-25

    Replicative DNA polymerases (Pols) frequently possess two distinct DNA processing activities: DNA synthesis (polymerization) and proofreading (3'-5' exonuclease activity). The polymerase and exonuclease reactions are performed alternately and are spatially separated in different protein domains. Thus, the growing DNA primer terminus has to undergo dynamic conformational switching between two distinct functional sites on the polymerase. Furthermore, the transition from polymerization (pol) mode to exonuclease (exo) mode must occur in the context of a DNA Pol holoenzyme, wherein the polymerase is physically associated with processivity factor proliferating cell nuclear antigen (PCNA) and primer-template DNA. The mechanism of this conformational switching and the role that PCNA plays in it have remained obscure, largely due to the dynamic nature of ternary Pol/PCNA/DNA assemblies. Here, we present computational models of ternary assemblies for archaeal polymerase PolB. We have combined all available structural information for the binary complexes with electron microscopy data and have refined atomistic models for ternary PolB/PCNA/DNA assemblies in pol and exo modes using molecular dynamics simulations. In addition to the canonical PIP-box/interdomain connector loop (IDCL) interface of PolB with PCNA, contact analysis of the simulation trajectories revealed new secondary binding interfaces, distinct between the pol and exo states. Using targeted molecular dynamics, we explored the conformational transition from pol to exo mode. We identified a hinge region between the thumb and palm domains of PolB that is critical for conformational switching. With the thumb domain anchored onto the PCNA surface, the neighboring palm domain executed rotational motion around the hinge, bringing the core of PolB down toward PCNA to form a new interface with the clamp. A helix from PolB containing a patch of arginine residues was involved in the binding, locking the complex in the exo

  12. The stability and controlled release of I-ascorbic acid encapsulated in poly (ethyl-2-cyanoacrylate) nanocapsules prepared by interfacial polymerization of water-in-oil microemulsions.

    PubMed

    Zhang, Su-Ning; Chen, Tao; Guo, Yi-Guang; Zhang, Jian; Song, Xiaoqiu; Zhou, Lei

    2015-01-01

    The L-ascorbic acid (AA) was encapsulated into biodegradable and biocompatible poly(ethyl-2-cyanoacrylate) (PECA) nanocapsules by interfacial polymerization of water-in-oil (W/O) microemulsions. The influences of surfactant concentration, pH value of the dispersed aqueous phase, and W/O ratio on nanocapsule size were discussed. The stability and in vitro release of encapsulated AA were also investigated. The results show that nanocapsules could be obtained under the conditions with low pH value, high fraction of aqueous phase, and appropriate surfactant concentration. The encapsulated AA was protected by nanocapsules from oxidation and presented superior storage stability in aqueous medium than pure AA. Releasing AA from the inner core of nanocapsules could be controlled by adjusting the enzyme hydrolysis extent of the PECA wall. PMID:26665980

  13. Learning Curve Assessment of Robot-Assisted Radical Prostatectomy Compared with Open-Surgery Controls from the Premier Perspective Database

    PubMed Central

    Kreaden, Usha S.; Gabbert, Jessica; Thomas, Raju

    2014-01-01

    Abstract Introduction: The primary aims of this study were to assess the learning curve effect of robot-assisted radical prostatectomy (RARP) in a large administrative database consisting of multiple U.S. hospitals and surgeons, and to compare the results of RARP with open radical prostatectomy (ORP) from the same settings. Materials and Methods: The patient population of study was from the Premier Perspective Database (Premier, Inc., Charlotte, NC) and consisted of 71,312 radical prostatectomies performed at more than 300 U.S. hospitals by up to 3739 surgeons by open or robotic techniques from 2004 to 2010. The key endpoints were surgery time, inpatient length of stay, and overall complications. We compared open versus robotic, results by year of procedures, results by case volume of specific surgeons, and results of open surgery in hospitals with and without a robotic system. Results: The mean surgery time was longer for RARP (4.4 hours, standard deviation [SD] 1.7) compared with ORP (3.4 hours, SD 1.5) in the same hospitals (p<0.0001). Inpatient stay was shorter for RARP (2.2 days, SD 1.9) compared with ORP (3.2 days, SD 2.7) in the same hospitals (p<0.0001). The overall complications were less for RARP (10.6%) compared with ORP (15.8%) in the same hospitals, as were transfusion rates. ORP results in hospitals without a robot were not better than ORP with a robot, and pretreatment co-morbidity profiles were similar in all cohorts. Trending of results by year of procedure showed no differences in the three cohorts, but trending of RARP results by surgeon experience showed improvements in surgery time, hospital stay, conversion rates, and complication rates. Conclusions: During the initial 7 years of RARP development, outcomes showed decreased hospital stay, complications, and transfusion rates. Learning curve trends for RARP were evident for these endpoints when grouped by surgeon experience, but not by year of surgery. PMID:24350787

  14. INHIBITING THE POLYMERIZATION OF NUCLEAR COOLANTS

    DOEpatents

    Colichman, E.L.

    1959-10-20

    >The formation of new reactor coolants which contain an additive tbat suppresses polymerization of the primary dissoclation free radical products of the pyrolytic and radiation decomposition of the organic coolants is described. The coolants consist of polyphenyls and condensed ring compounds having from two to about four carbon rings and from 0.1 to 5% of a powdered metal hydride chosen from the group consisting of the group IIA and IVA dispersed in the hydrocarbon.

  15. Polymerization of perfluorobutadiene

    NASA Technical Reports Server (NTRS)

    Newman, J.; Toy, M. S.

    1970-01-01

    Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

  16. Group transfer polymerization. Mechanism revisted

    SciTech Connect

    Sogah, D.Y.

    1993-12-31

    Group Transfer Polymerization (GTP) is a living polymerization technique that allows control of characteristics of vinyl polymers, especially those derived from methacrylate monomers. Several mechanistic pathways have been proposed by different research groups. This presentation will examine the most plausible mechanisms and the evidence supporting each one. The dependence of the reaction on the type, nature and concentrations of catalysts, other additives, initiators and monomers will be discussed. The crucial role that chiral organosilicon reagents may play will be examined using a novel cyclic initiator containing 2,2`-dialkylsilyl-1,1`-binaphthyl.

  17. Polymerization Reactor Engineering.

    ERIC Educational Resources Information Center

    Skaates, J. Michael

    1987-01-01

    Describes a polymerization reactor engineering course offered at Michigan Technological University which focuses on the design and operation of industrial polymerization reactors to achieve a desired degree of polymerization and molecular weight distribution. Provides a list of the course topics and assigned readings. (TW)

  18. Radical prostatectomy

    MedlinePlus

    ... Sometimes, laparoscopic surgery is performed using a robotic system. The surgeon moves the instruments and camera using robotic arms while sitting at a control console near the operating table. Not every hospital offers robotic surgery. Perineal : ...

  19. Nanoformulation of poly(ethylene glycol) polymerized organic insect repellent by PIT emulsification method and its application for Japanese encephalitis vector control.

    PubMed

    Balaji, A P B; Mishra, Prabhakar; Suresh Kumar, R S; Mukherjee, Amitava; Chandrasekaran, Natarajan

    2015-04-01

    The utilization of increased dosage of insect repellents to overcome mosquito resistance has raised environmental concerns globally. In accord to this, we have formulated an efficacious, water-dispersive, nanometric formulation of a poor water-soluble insect repellent, diethylphenylacetamide (DEPA) by poly(ethylene glycol) (PEG) polymerization followed by PIT emulsification method. The critical micelle concentration of PEG in the spontaneously emulsified conventional DEPA droplets was determined, based on the droplets physical stability. Subjecting them to PIT emulsification yielded monodispersed polymeric nanomicelles of DEPA (Nano DEPA) with hydrodynamic mean diameter of 153.74 nm. The high-resolution scanning and transmission electron microscopic studies revealed the characteristic core-shell structure of micelle. The comparative efficacy of Bulk DEPA and Nano DEPA was evaluated by larvicidal and WHO cone bioassay against the Japanese encephalitis vector Culex tritaeniorhynchus. The median lethal concentrations (48 h) for 3rd instars C. tritaeniorhynchus larvae were found to be 0.416 mg/L for Bulk DEPA and 0.052 mg/L for Nano DEPA, respectively. The median knockdown concentrations (60 min) for the two to three-day-old, sucrose-fed, female adult mosquitoes were 5.372% (v/v) and 3.471% (v/v) for Bulk and Nano DEPA, respectively. Further investigation by histopathological and biochemical studies propound that Nano DEPA exerted better bioefficacy as comparative to its bulk form even at minimal exposure concentrations. Hence, Nano DEPA will serve as an effective alternate in controlling the vector expansion with reduced dosage. PMID:25766922

  20. Determination of trace uranyl ion by thermoresponsive porphyrin-terminated polymeric sensor.

    PubMed

    Shu, Xiaowen; Wang, Yingjie; Zhang, Shuang; Huang, Li; Wang, Shuao; Hua, Daoben

    2015-01-01

    Uranyl ion exists at trace levels in the environment and can cause severe adverse effects to human health. Therefore, it is desirable to develop analytical methods that can determine the trace uranyl ion in aqueous medium. We report here a new method using a thermo-responsive polymeric fluorescent sensor. Specifically, 5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin terminated poly(N-isopropylacrylamide) (TCPP-PNIPAM) was synthesized by controlled free radical polymerization for the detection of uranyl ion. The maximum fluorescence intensity at ~ 658 nm of TCPP-PNIPAM increases with molecular weights and is also closely related to the temperature. The polymeric sensor is sensitive to pH (1.0 ~ 5.0) with a fast responsive time (~ 3 min). Under optimized experimental conditions, the sensor exhibits a stable response for uranyl ion with high selectivity over a concentration range from 1.0 × 10(-3) to 1.0 × 10(-7)mol/L. For the trace uranyl ion (such as 1.0 × 10(-8) or 10(-9)mol/L), the determination could be successfully achieved after concentrating 100 times by centrifugation above 32°C. The properties enable the polymeric sensor to have great potential for environmental application. PMID:25281093

  1. Well-Defined Protein/Peptide-Polymer Conjugates by Aqueous Cu-LRP: Synthesis and Controlled Self-Assembly.

    PubMed

    Zhang, Qiang; Li, Muxiu; Zhu, Chongyu; Nurumbetov, Gabit; Li, Zaidong; Wilson, Paul; Kempe, Kristian; Haddleton, David M

    2015-07-29

    The synthesis of well-defined protein/peptide-polymer conjugates with interesting self-assembly behavior via single electron transfer living radical polymerization in water is described. A range of protein/peptides with different physical and chemical properties have been modified to macroinitiators and optimized polymerization conditions ensure successful polymerization from soluble, insoluble, and dispersed protein/peptide molecules or protein aggregates. This powerful strategy tolerates a range of functional monomers and mediates efficient homo or block copolymerization to generate hydrophilic polymers with controlled molecular weight (MW) and narrow MW distribution. The polymerizations from bovine insulin macroinitiators follow surface-initiated "grafting from" polymerization mechanism and may involve a series of self-assembly and disassembly processes. Synthesized insulin-polymer conjugates form spheres in water, and the self-assembly behavior could be controlled via thermal control, carbohydrate-protein interaction, and protein denaturation. PMID:26149497

  2. Nitrate-induced photolysis in natural waters: Controls on concentrations of hydroxyl radical photo-intermediates by natural scavenging agents

    SciTech Connect

    Brezonik, P.L.; Fulkerson-Brekken, J.

    1998-10-01

    The importance of the principal natural scavenging agents for hydroxyl radicals ({sup {sm_bullet}}OH) was evaluated, and a general framework was developed to predict the significance of nitrate-induced, {sup {sm_bullet}}OH-mediated degradation of aquatic contaminants. Rate constants for *OH scavenging by dissolved organic matter (DOM) from five surface water sources were in a narrow range which is similar to previously reported values and suggests that the importance of DOM as a {sup {sm_bullet}}OH sink can be estimated simply from the dissolved organic carbon (DOC) concentration of a water. Scavenging of {sup {sm_bullet}}*OH by carbonate and bicarbonate is generally less important, but these ions can be the major cause of *OH scavenging in low DOC, high alkalinity waters. Use of the framework is illustrated by predicting levels of {sup {sm_bullet}}OH and half-lives of the corn herbicide acetochlor in waters ranging from pristine to highly influenced by agricultural activities.

  3. Clinical application of sartorius tendon transposition during radical vulvectomy: a case control study of 58 cases at a single institution

    PubMed Central

    Kou, Xinxin; Feng, Xiaojie; Liu, Fenghua; Chao, Hongtu; Wang, Liying

    2015-01-01

    Objective The aim of this study was to investigate the clinical effects of sartorius tendon transposition versus sartorius transposition during bilateral inguinal lymphadenectomy of radical vulvectomy. Methods A total of 58 vulvar cancer patients who had surgery from May 2007 to October 2013, in which 30 patients received sartorius transposition and 28 patients received sartorius tendon transposition. All patients were matched by age, body mass index, stage, histology, and grade. Intraoperative variables and postoperative complications, recurrence, progression-free survival (PFS), and overall survival (OS) and postoperative life quality were compared and analyzed. Results No significant differences were found at median surgical times and amounts of bleeding (p=0.316 and p=0.249, respectively), neither at the incidences of groin cellulitis and lymphocele (p=0.673 and p=0.473, respectively), but the recovery times of the inguinal wounds were shorter (p=0.026) and the incidences of wound break and chronic lymphedema were significantly decreased in the tendon transposition group (p=0.012 and p=0.022, respectively). Postoperative quality of life in tendon transposition group was significantly improved as indicated by the EORTC QLQ-C30 questionnaire. Recurrences were similar (p=0.346) and no significant differences were found at PFS and OS (p=0.990 and p=0.683, respectively). Conclusion Compared to sartorius transposition, sartorius tendon transposition during inguinal lymphadenectomy led to improved patient recovery, reduced postoperative complications, and improved life quality without compromising the outcomes. PMID:26404124

  4. Thermally and photoinduced polymerization of ultrathin sexithiophene films

    SciTech Connect

    Sander, Anke; Hammer, Rene; Duncker, Klaus; Förster, Stefan; Widdra, Wolf

    2014-09-14

    The thermally-induced polymerization of α-sexithiophene (6T) molecules on Ag(001) and Au(001) gives rise to long unbranched polymer chains or branched polymer networks depending on the annealing parameters. There, the onset temperature for polymerization depends on the strength of interaction with the underlying substrate. Similar polymerization processes are also induced by ultraviolet radiation with photon energies between 3.0 and 4.2 eV. Radical formation by an electronic excitation in the 6T molecule is proposed as the driving mechanism that necessitates the interplay with the metallic substrate.

  5. Development of polymeric coatings for control of electro-osmotic flow in ASTP MA-011 electrophoresis technology experiment

    NASA Technical Reports Server (NTRS)

    Patterson, W. J.

    1976-01-01

    The development of a methyl cellulose based coating system for control of electro-osmotic flow at the walls of electrophoresis cells is described. Flight electrophoresis columns were coated with this system, resulting in a flight set of six columns. In flight photography of MA-011 electrophoretic separations verified control of electro-osmotic flow.

  6. Fast-track surgery protocol in elderly patients undergoing laparoscopic radical gastrectomy for gastric cancer: a randomized controlled trial

    PubMed Central

    Liu, Guozheng; Jian, Fengguo; Wang, Xiuqin; Chen, Lin

    2016-01-01

    Aim To study the efficacy of the fast-track surgery (FTS) program combined with laparoscopic radical gastrectomy for elderly gastric cancer (GC) patients. Methods Eighty-four elderly patients diagnosed with GC between September 2014 and August 2015 were recruited to participate in this study and were divided into four groups randomly based on the random number table as follows: FTS + laparoscopic group (Group A, n=21), FTS + laparotomy group (Group B, n=21), conventional perioperative care (CC) + laparoscopic group (Group C, n=21), and CC + laparotomy group (Group D, n=21). Observation indicators include intrasurgery indicators, postoperative recovery indicators, nutritional status indicators, and systemic stress response indicators. Results Preoperative and intraoperative baseline characteristics showed no significant differences between patients in each group (P>0.05). There were no significant differences between each group in nausea and vomiting, intestinal obstruction, urinary retention, incision infection, pulmonary infection, and urinary tract infection after operation (P>0.05). Time of first flatus and postoperative hospital stay time of FTS Group A were the shortest, and total medical cost of this group was the lowest. For all groups, serum albumin, prealbumin, and transferrin significantly decreased, while CRP and interleukin 6 were significantly increased postoperative day 1. From postoperative day 4–7, all indicators of the four groups gradually recovered, but compared with other three groups, those of Group A recovered fastest. Conclusion FTS combined with laparoscopic surgery can promote faster postoperative recovery, improve early postoperative nutritional status, and more effectively reduce postoperative stress reaction, and hence is safe and effective for elderly GC patients. PMID:27330314

  7. Surface-initiated polymerizations on initiator anchored substrates: Synthesis and characterization of nanometer thick functional polymer films

    NASA Astrophysics Data System (ADS)

    Bao, Zhiyi

    -stranded DNA or antibodies. We report the remarkably rapid synthesis of polymer brushes under mild conditions (50°C) using surface-initiated polymerization. The use of the highly active atom transfer radical polymerization catalyst Cu(1)1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane allows synthesis of 100 ran thick poly(tert-butyl acrylate) brushes from initiator-modified Au surfaces in just 5 minutes. Using the same catalyst, polymerization of hydroxyethyl methacrylate and methyl methacrylate yielded 100 nm thick films in 10 and 60 minutes, respectively. Such polymerization rates are an order of magnitude greater than those for traditional free-radical polymerizations initiated from surfaces. It is important to note that though these rapid polymerizations from surfaces are not "living", they retain some features of controlled radical polymerizations such as the ability to form block copolymer brushes. Such rapid polymerization from a surface will be very important in potential applications of polymer brushes as skin layers in separation membranes and as substrate coatings for probe immobilization in gene and protein chips.

  8. Polymeric Ionic Networks with High Charge Density: Solid-like Electrolytes in Lithium Metal Batteries

    DOE PAGESBeta

    Zhang, Pengfei; Li, Mingtao; Jiang, Xueguang; Fang, Youxing; Veith, Gabriel M.; Sun, Xiao-Guang; Dai, Sheng

    2015-11-02

    Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10-3 S cm-1 at 22 °C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

  9. Polymeric Ionic Networks with High Charge Density: Solid-like Electrolytes in Lithium Metal Batteries

    SciTech Connect

    Zhang, Pengfei; Li, Mingtao; Jiang, Xueguang; Fang, Youxing; Veith, Gabriel M.; Sun, Xiao-Guang; Dai, Sheng

    2015-11-02

    Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10-3 S cm-1 at 22 °C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

  10. Polymerized Ionic Networks with High Charge Density: Quasi-Solid Electrolytes in Lithium-Metal Batteries.

    PubMed

    Zhang, Pengfei; Li, Mingtao; Yang, Bolun; Fang, Youxing; Jiang, Xueguang; Veith, Gabriel M; Sun, Xiao-Guang; Dai, Sheng

    2015-12-22

    Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10(-3) S cm(-1) at 22°C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes. PMID:26523468

  11. Participation of cationic intermediates in radical-induced homopolymerization of maleic anhydride

    SciTech Connect

    Gaylord, N.G.; Koo, J.Y.

    1981-03-01

    Since the failure to promote MAH polymerization in the presence of amine-containing redox catalyst systems suggested the presence of cationic intermediates, the radical-induced polymerization of MAH was carried out in the absence and in the presence of N,N-dimethylformamide (DMF) and N, N-dimethylaniline (DMA).

  12. Sterically and electrosterically stabilized emulsion polymerization. Kinetics and preparation.

    PubMed

    Capek, Ignác

    2002-10-21

    The principal subject discussed in the current paper is the radical polymerization in the aqueous emulsions of unsaturated monomers (styrene, alkyl (meth)acrylates, etc.) stabilized by non-ionic and ionic/non-ionic emulsifiers. The sterically and electrosterically stabilized emulsion polymerization is a classical method which allows to prepare polymer lattices with large particles and a narrow particle size distribution. In spite of the similarities between electrostatically and sterically stabilized emulsion polymerizations, there are large differences in the polymerization rate, particle size and nucleation mode due to varying solubility of emulsifiers in oil and water phases, micelle sizes and thickness of the interfacial layer at the particle surface. The well-known Smith-Ewart theory mostly applicable for ionic emulsifier, predicts that the number of particles nucleated is proportional to the concentration of emulsifier up to 0.6. The thin interfacial layer at the particle surface, the large surface area of relatively small polymer particles and high stability of small particles lead to rapid polymerization. In the sterically stabilized emulsion polymerization the reaction order is significantly above 0.6. This was ascribed to limited flocculation of polymer particles at low concentration of emulsifier, due to preferential location of emulsifier in the monomer phase. Polymerization in the large particles deviates from the zero-one approach but the pseudo-bulk kinetics can be operative. The thick interfacial layer can act as a barrier for entering radicals due to which the radical entry efficiency and also the rate of polymerization are depressed. The high oil-solubility of non-ionic emulsifier decreases the initial micellar amount of emulsifier available for particle nucleation, which induces non-stationary state polymerization. The continuous release of emulsifier from the monomer phase and dismantling of the non-micellar aggregates maintained a high level of

  13. Effects of high energy simulated space radiation on polymeric second-surface mirrors. [thermal control coatings - performance tests

    NASA Technical Reports Server (NTRS)

    Eogdall, L. B.; Cannaday, S. S.

    1975-01-01

    A radiation effects experimental program was performed, in which second surface mirror type thermal control coatings were exposed to ultraviolet radiation, electrons, and protons simultaneously. Stability was assessed by making periodic spectral reflectance measurements in situ (and in air after testing for comparison). Solar absorption coefficients were derived by computer. Many of the exposed materials showed large amounts of degradation in reflectance absorptance, principally due to the electron exposure. A series of tests was conducted, leading to the identification of a modified second surface mirror that shows considerable improvement and promise for stability during thermal control applications in a charged particle space radiation environment.

  14. Size-controlled synthesis of near-monodisperse gold nanoparticles in the 1-4 nm range using polymeric stabilizers.

    PubMed

    Hussain, Irshad; Graham, Susan; Wang, Zhenxin; Tan, Bien; Sherrington, David C; Rannard, Steven P; Cooper, Andrew I; Brust, Mathias

    2005-11-30

    We report here a simple one-step protocol for the preparation of near-monodisperse gold hydrosols in the small size regime (<5 nm). The particle size can be controlled by varying the concentration of the stabilizing polymer, which can be readily displaced by thiol ligands to yield monolayer protected clusters of the usual type. PMID:16305218

  15. Controlled architecture for improved macromolecular memory within polymer networks.

    PubMed

    DiPasquale, Stephen A; Byrne, Mark E

    2016-08-01

    This brief review analyzes recent developments in the field of living/controlled polymerization and the potential of this technique for creating imprinted polymers with highly structured architecture with macromolecular memory. As a result, it is possible to engineer polymers at the molecular level with increased homogeneity relating to enhanced template binding and transport. Only recently has living/controlled polymerization been exploited to decrease heterogeneity and substantially improve the efficiency of the imprinting process for both highly and weakly crosslinked imprinted polymers. Living polymerization can be utilized to create imprinted networks that are vastly more efficient than similar polymers produced using conventional free radical polymerization, and these improvements increase the role that macromolecular memory can play in the design and engineering of new drug delivery and sensing platforms. PMID:27322505

  16. A new metal-organic polymeric system capable of stimuli-responsive controlled release of the drug ibuprofen.

    PubMed

    Lago, Ana Belén; Pino-Cuevas, Arantxa; Carballo, Rosa; Vázquez-López, Ezequiel M

    2016-01-28

    A series of new zinc compounds has been prepared easily under mild synthetic conditions with the drug ibuprofen incorporated as a ligand to form different coordination polymers. The host materials have a high drug content and exhibit high stability, low cytotoxicity, good biodegradability and high biocompatibility. The ion exchange mechanism involved in the ibuprofen release process and the pH-controlled drug release have been studied. PMID:26692254

  17. Thiol-Mediated Controlled Ring-Opening Polymerization of Cysteine-Derived β-Thiolactone and Unique Features of Product Polythioester.

    PubMed

    Suzuki, Masato; Makimura, Kazumasa; Matsuoka, Shin-ichi

    2016-03-14

    The controlled ring-opening polymerization of the β-thiolactone derived from N-Boc cysteine was achieved using N-Boc-L-cysteine methyl ester as the initiator in NMP at room temperature. The propagating end is the thiol group, which attacks the carbonyl to open the monomer ring by the C(═O)-S bond scission. A thiol-ene click reaction demonstrated the utility of the thiol group at the propagating terminal. The block copolymer was efficiently produced by the terminal coupling of the polythioester with the norbornene terminated PEG. As another interesting reaction, the polythioester underwent the main chain transformation to polycysteine through the intramolecular S-to-N acyl migration, triggered by the deprotection of the pendant Boc groups. The polythioester from L-cysteine showed Cotton effects between 200 and 300 nm in the circular dichroism (CD) spectrum. Although the CD pattern resembled that produced by the α-helix of polypeptide, it was ascribable not to the second structure but to the relative orientation of the thioester and carbamate carbonyls in the repeating unit. PMID:26845398

  18. Growth of PbTe nanorods controlled by polymerized tellurium anions and metal(II) amides via composite-hydroxide-mediated approach

    SciTech Connect

    Wan Buyong; Hu Chenguo; Liu Hong; Xiong Yufeng; Li Feiyun; Xi Yi; He Xiaoshan

    2009-09-15

    The pure face-centered-cubic PbTe nanorods have been synthesized by the composite-hydroxide-mediated approach using hydrazine as a reducing agent. The method is based on reaction among reactants in the melts of potassium hydroxide and sodium hydroxide eutectic at 170-220 deg. C and normal atmosphere without using any organic dispersant or surface-capping agent. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy were used to characterize the structure, morphology and composition of the samples. The diameters of nanorods are almost fixed, while the lengths can be tunable under different growth time and temperatures. The growth mechanism of PbTe nanorods is investigated via UV-vis absorption, demonstrating that polymerized tellurium anions and metal(II) amides in the hydrazine hydroxide melts could control the crystallization and growth process of PbTe nanostructures. The band gap of as-synthesized PbTe nanorods has been calculated based on UV-vis-NIR optical diffuse reflectance spectra data.

  19. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, T.J.; Eisen, M.S.; Giardello, M.A.

    1994-07-19

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C[sub 5]R[prime][sub 4[minus]x]R*[sub x])-A-(C[sub 5]R[double prime][sub 4[minus]y]R[prime][double prime][sub y])-M-Q[sub p], where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R[prime], R[double prime], R[prime][double prime], and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3 [<=] p [<=] 0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form cation-like'' species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other [alpha]-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

  20. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1994-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R'".sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R'", and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  1. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1995-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R"'.sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R"', and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  2. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, T.J.; Eisen, M.S.; Giardello, M.A.

    1995-10-03

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C{sub 5}R{prime}{sub 4{minus}x}R*{sub x})A(C{sub 5}R{double_prime}{sub 4{minus}y}R{double_prime}{prime}{sub y})MQ{sub p}, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R{prime}, R{double_prime}, R{double_prime}{prime}, and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3{>=}p{>=}0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form ``cation-like`` species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other {alpha}-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

  3. Radical prostatectomy - discharge

    MedlinePlus

    ... prostatectomy - discharge; Laparoscopic radical prostatectomy - discharge; LRP - discharge; Robotic-assisted laparoscopic prostatectomy - discharge ; RALP - discharge; Pelvic lymphadenectomy - ...

  4. A short review of radiation-induced raft-mediated graft copolymerization: A powerful combination for modifying the surface properties of polymers in a controlled manner

    NASA Astrophysics Data System (ADS)

    Barsbay, Murat; Güven, Olgun

    2009-12-01

    Surface grafting of polymeric materials is attracting increasing attention as it enables the preparation of new materials from known and commercially available polymers having desirable bulk properties such as thermal stability, elasticity, permeability, etc., in conjunction with advantageous newly tailored surface properties such as biocompatibility, biomimicry, adhesion, etc. Ionizing radiation, particularly γ radiation is one of the most powerful tools for preparing graft copolymers as it generates radicals on most substrates. With the advent of living free-radical polymerization techniques, application of γ radiation has been extended to a new era of grafting; grafting in a controlled manner to achieve surfaces with tailored and well-defined properties. This report presents the current use of γ radiation in living free-radical polymerization and highlights the use of both techniques together as a combination to present an advance in the ability to prepare surfaces with desired, tunable and well-defined properties.

  5. Sunlight and free radicals

    NASA Astrophysics Data System (ADS)

    Tidwell, Thomas

    2013-08-01

    Thomas Tidwell reflects on the overlooked -- but prescient -- proposal by the British chemists Arthur Downes and Thomas Blunt for photochemical free-radical formation, decades before Moses Gomberg launched the field of radical chemistry by preparing triphenylmethyl, the first stable organic radical.

  6. Selective in vitro anticancer effect of superparamagnetic iron oxide nanoparticles loaded in hyaluronan polymeric micelles.

    PubMed

    Smejkalová, Daniela; Nešporová, Kristina; Huerta-Angeles, Gloria; Syrovátka, Jakub; Jirák, Daniel; Gálisová, Andrea; Velebný, Vladimír

    2014-11-10

    Due to its native origin, excellent biocompatibility and biodegradability, hyaluronan (HA) represents an attractive polymer for superparamagnetic iron oxide nanoparticles (SPION) coating. Herein, we report HA polymeric micelles encapsulating oleic acid coated SPIONs, having a hydrodynamic size of about 100 nm and SPION loading capacity of 1-2 wt %. The HA-SPION polymeric micelles were found to be selectively cytotoxic toward a number of human cancer cell lines, mainly those of colon adenocarcinoma (HT-29). The selective inhibition of cell growth was even observed when the SPION loaded HA polymeric micelles were incubated with a mixture of control and cancer cells. The selective in vitro inhibition could not be connected with an enhanced CD44 uptake or radical oxygen species formation and was rather connected with a different way of SPION intracellular release. While aggregated iron particles were visualized in control cells, nonaggregated solubilized iron oxide particles were detected in cancer cells. In vivo SPION accumulation in intramuscular tumor following an intravenous micelle administration was confirmed by magnetic resonance (MR) imaging and histological analysis. Having a suitable hydrodynamic size, high magnetic relaxivity, and being cancer specific and able to accumulate in vivo in tumors, SPION-loaded HA micelles represent a promising platform for theranostic applications. PMID:25268047

  7. Precision synthesis of bio-based acrylic thermoplastic elastomer by RAFT polymerization of itaconic acid derivatives.

    PubMed

    Satoh, Kotaro; Lee, Dong-Hyung; Nagai, Kanji; Kamigaito, Masami

    2014-01-01

    Bio-based polymer materials from renewable resources have recently become a growing research focus. Herein, a novel thermoplastic elastomer is developed via controlled/living radical polymerization of plant-derived itaconic acid derivatives, which are some of the most abundant renewable acrylic monomers obtained via the fermentation of starch. The reversible addition-fragmentation chain-transfer (RAFT) polymerizations of itaconic acid imides, such as N-phenylitaconimide and N-(p-tolyl)itaconimide, and itaconic acid esters, such as di-n-butyl itaconate and bis(2-ethylhexyl) itaconate, are examined using a series of RAFT agents to afford well-defined polymers. The number-average molecular weights of these polymers increase with the monomer conversion while retaining relatively narrow molecular weight distributions. Based on the successful controlled/living polymerization, sequential block copolymerization is subsequently investigated using mono- and di-functional RAFT agents to produce block copolymers with soft poly(itaconate) and hard poly(itaconimide) segments. The properties of the obtained triblock copolymer are evaluated as bio-based acrylic thermoplastic elastomers. PMID:24243816

  8. COPPER(I)-CATALYZED ATOM TRANSFER RADICAL POLYMERIZATIONS. (R826735)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. ATOM TRANSFER RADICAL POLYMERIZATION IN SUPERCRITICAL CARBON DIOXIDE. (R826735)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  10. TRANSITION METAL CATALYZED ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  11. Robot-assisted radical cystectomy.

    PubMed

    Kurpad, Raj; Woods, Michael

    2015-12-01

    Robot-assisted radical cystectomy (RARC) has rapidly penetrated the field of urology since its inception in 2003. Several observational studies, retrospective reports, and three randomized controlled trials (RCT) have preliminarily demonstrated the safety and efficacy of (RARC). Additionally, results from the RAZOR RCT will be available in 2016-2017 to better substantiate the use of (RARC). PMID:26310514

  12. Embedded MicroHeating Elements in Polymeric MicroChannels for Temperature Control and Fluid Flow Sensing

    PubMed Central

    Gaitan, Michael; Locascio, Laurie E.

    2004-01-01

    This paper describes the first demonstration of temperature control and flow sensing of fluids using integrated circuit (IC)-based microheating elements embedded in microchannels molded in polydimethylsiloxane (PDMS). Fluid channels and connections to capillary tubing are molded in PDMS using a silicon wafer template. The PDMS film is then bonded to an IC that contains the micromachined microheating elements. Capillary tubes are inserted and fluids are externally pumped through the channels. Heating of the fluid is observed by the formation of bubbles on the microheating element. Sensing of fluid flow is demonstrated by measuring a change in the large signal resistance of the microheater analogous to a hot wire anemometer with a detection limit of ± 320 pL/s. PMID:27366617

  13. Formulation development and evaluation of metronidazole magnetic nanosuspension as a magnetic-targeted and polymeric-controlled drug delivery system

    NASA Astrophysics Data System (ADS)

    Latha, Subbiah; Selvamani, Palanisamy; Kumar, Chelladurai Senthil; Sharavanan, Palaniappan; Suganya, Govindan; Beniwal, Vijender Singh; Rao, Poduri Rama

    2009-05-01

    A nanosuspension of magnetically tagged metronidazole was developed by the solvent displacement method coupled with ultrasonication and was evaluated for its physicochemical properties. The drug release from metronidazole magnetic nanosuspension at pH 1.2 and 7.0 shows maximum correlation coefficient for zero order and Higuchi model, respectively. The anthelmintic activity of the formulated metronidazole magnetic nanosuspension was evaluated on Indian earthworms (Pheretima poi). Metronidazole magnetic nanosuspension at a dose of 10 and 50 mg/ml shortened by 31% and 34%, respectively, the mean time to death of the earthworms when compared against a non-magnetic metronidazole suspension. Thus, the developed metronidazole magnetic nanosuspension showed potent, controlled and targeted drug action and might be a good therapeutic avenue in combating infectious GI disorders.

  14. Self-Propagating Frontal Polymerization in Water at Ambient Pressure

    NASA Technical Reports Server (NTRS)

    Olten, Nesrin; Kraigsley, Alison; Ronney, Paul D.

    2003-01-01

    Advances in polymer chemistry have led to the development of monomers and initiation agents that enable propagating free-radical polymerization fronts to exist. These fronts are driven by the exothermicity of the polymerization reaction and the transport of heat from the polymerized product to the reactant monomer/solvent/initiator solution. The thermal energy transported to the reactant solution causes the initiator to decompose, yielding free radicals, which start the free radical polymerization process as discussed in recent reviews. The use of polymerization processes based on propagating fronts has numerous applications. Perhaps the most important of these is that it enables rapid curing of polymers without external heating since the polymerization process itself provides the high temperatures necessary to initiate and sustain polymerization. This process also enables more uniform curing of arbitrarily thick samples since it does not rely on heat transfer from an external source, which will necessarily cause the temperature history of the sample to vary with distance from the surface according to a diffusion-like process. Frontal polymerization also enables filling and sealing of structures having cavities of arbitrary shape without having to externally heat the structure. Water at atmospheric pressure is most convenient solvent to employ and the most important for practical applications (because of the cost and environmental issues associated with DMSO and other solvents). Nevertheless, to our knowledge, steady, self-propagating polymerization fronts have not been reported in water at atmospheric pressure. Currently, polymerization fronts require a high boiling point solvent (either water at high pressures or an alternative solvent such as dimethyl sulfoxide (DMSO) (boiling point 189 C at atmospheric pressure.) Early work on frontal polymerization, employed pressures up to 5000 atm in order to avoid boiling of the monomer/solvent/initiator solution. High

  15. Electrochemical polymerization of pyrrole derivatives

    SciTech Connect

    Inagaki, T.; Hunter, M.; Yang, X.Q.; Skotheim, T.A.; Lee, H.S.; Okamoto, Y.

    1988-01-01

    Electrochemical copolymerization of pyrrole and 3-(6-ferrocenyl-6-hydroxyhexyl)pyrrole (P-Fc) yields a ferrocene functionalized polypyrrole with a controlled amount of ferrocene functionalization. Similarly, copolymers of pyrrole and 3-(4-(2,5- dimethoxyphenyl)butyl)pyrrole (P-MP) can be made by electrochemical polymerization and converted to the copolymers containing pH dependent electroactive hydroquinone moieties. 16 refs., 6 figs.

  16. Oligorotaxane Radicals under Orders.

    PubMed

    Wang, Yuping; Frasconi, Marco; Liu, Wei-Guang; Sun, Junling; Wu, Yilei; Nassar, Majed S; Botros, Youssry Y; Goddard, William A; Wasielewski, Michael R; Stoddart, J Fraser

    2016-02-24

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components-namely oligoviologens-in which different numbers of 4,4'-bipyridinium (BIPY(2+)) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT(4+)) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY(•+) radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne-azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers. PMID:27163033

  17. Oligorotaxane Radicals under Orders

    PubMed Central

    2016-01-01

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components—namely oligoviologens—in which different numbers of 4,4′-bipyridinium (BIPY2+) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT4+) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY•+ radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne–azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers. PMID:27163033

  18. A new method for the production of gelatin microparticles for controlled protein release from porous polymeric scaffolds.

    PubMed

    Ozkizilcik, Asya; Tuzlakoglu, Kadriye

    2014-03-01

    Tissue engineering using scaffolds and growth factors is a crucial approach in bone regeneration and repair. The combination of bioactive agents carrying microparticles with porous scaffolds can be an efficient solution when controlled release of bio-signalling molecules is required. The present study was based on a recent approach using a biodegradable scaffold and protein-loaded microparticles produced in an innovative manner in which protein loss is minimized during the loading process. Bovine serum albumin (BSA)-loaded gelatin microparticles were obtained by grinding freeze-dried membranes of gelatin and BSA. Porous scaffolds (250-355 µm pore size) produced from a polyactide (PLLA) and polycaprolactone (PCL) blend by salt leaching/supercritical CO₂ methods were used for the experiments. Gelatin microparticles containing three different BSA amounts were incorporated into the porous scaffolds by using a surfactant. In vitro release profiles showed up to 90% protein loading efficiency. This novel method appears to be an effective approach for producing particles that can minimize protein loss during the loading process. PMID:22499408

  19. Fluorescent polymeric assemblies as stimuli-responsive vehicles for drug controlled release and cell/tissue imaging

    NASA Astrophysics Data System (ADS)

    Chang, Ying; Li, Yang; Yu, Shirong; Mao, Jie; Liu, Cheng; Li, Qi; Yuan, Conghui; He, Ning; Luo, Weiang; Dai, Lizong

    2015-01-01

    Polymer assemblies with good biocompatibility, stimuli-responsive properties and clinical imaging capability are desirable carriers for future biomedical applications. Herein, we report on the synthesis of a novel anthracenecarboxaldehyde-decorated poly(N-(4-aminophenyl) methacryl amide-oligoethyleneglycolmonomethylether methacrylate) (P(MAAPAC-MAAP-MAPEG)) copolymer, comprising fluorescent chromophore and acid-labile moiety. This copolymer can assemble into micelles in aqueous solution and shows a spherical shape with well-defined particle size and narrow particle size distribution. The pH-responsive property of the micelles has been evaluated by the change of particle size and the controlled release of guest molecules. The intrinsic fluorescence property endows the micelles with excellent cell/tissue imaging capability. Cell viability evaluation with human hepatocellular carcinoma BEL-7402 cells demonstrates that the micelles are nontoxic. The cellular uptake of the micelles indicates a time-dependent behavior. The H22-tumor bearing mice treated with the micelles clearly exhibits the tumor accumulation. These multi-functional nanocarriers may be of great interest in the application of drug delivery.

  20. Tranexamic acid loaded gellan gum-based polymeric microbeads for controlled release: in vitro and in vivo assessment.

    PubMed

    Bhattacharya, Shiv Sankar; Banerjee, Subham; Chowdhury, Purojit; Ghosh, Amitava; Hegde, Rahul Rama; Mondal, Ranjit

    2013-12-01

    Gellan gum (GG) microbeads containing tranexamic acid (TA), an anti-fibrinolytic drug were prepared by a classic sol-gel transition induced by ionic crosslinking technique using aluminum chloride (AlCl3) as cross-linking agent. The influence of different formulation variables on in vitro physico-chemical parameters and drug release studies were performed systematically. The microbeads were evaluated by scanning electron microscopy (SEM), Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and high performance liquid chromatographic (HPLC) analysis. Particle size and swelling behavior of microbeads were also investigated. Microbeads showed improved drug encapsulation efficiency along with enhanced drug release. The in vivo studies exhibited sustained drug release in rabbits over a prolonged period after oral administration of these newly developed TA loaded GG microbeads. Based on the results of in vitro and in vivo studies in experimental animal model it was concluded that these microbeads provided intestinal specific controlled release of TA. PMID:24183265

  1. Mechanically Stabilized Tetrathiafulvalene Radical Dimers

    SciTech Connect

    Coskun, Ali; Spruell, Jason M.; Barin, Gokhan; Fahrenbach, Albert C.; Forgan, Ross S.; Colvin, Michael T.; Carmieli, Raanan; Benitez, Diego; Tkatchouk, Ekaterina; Friedman, Douglas C.; Sarjeant, Amy A.; Wasielewski, Michael R.; Goddard, William A.; Stoddart, J. Fraser

    2011-01-01

    Two donor-acceptor [3]catenanes—composed of a tetracationic molecular square, cyclobis(paraquat-4,4'-biphenylene), as the π-electron deficient ring and either two tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) containing macrocycles or two TTF-butadiyne-containing macrocycles as the π-electron rich components—have been investigated in order to study their ability to form TTF radical dimers. It has been proven that the mechanically interlocked nature of the [3]catenanes facilitates the formation of the TTF radical dimers under redox control, allowing an investigation to be performed on these intermolecular interactions in a so-called “molecular flask” under ambient conditions in considerable detail. In addition, it has also been shown that the stability of the TTF radical-cation dimers can be tuned by varying the secondary binding motifs in the [3]catenanes. By replacing the DNP station with a butadiyne group, the distribution of the TTF radical-cation dimer can be changed from 60% to 100%. These findings have been established by several techniques including cyclic voltammetry, spectroelectrochemistry and UV-vis-NIR and EPR spectroscopies, as well as with X-ray diffraction analysis which has provided a range of solid-state crystal structures. The experimental data are also supported by high-level DFT calculations. The results contribute significantly to our fundamental understanding of the interactions within the TTF radical dimers.

  2. Stereospecific olefin polymerization catalysts

    DOEpatents

    Bercaw, John E.; Herzog, Timothy A.

    1998-01-01

    A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

  3. Stereospecific olefin polymerization catalysts

    DOEpatents

    Bercaw, J.E.; Herzog, T.A.

    1998-01-13

    A metallocene catalyst system is described for the polymerization of {alpha}-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula shown wherein: R{sup 1}, R{sup 2}, and R{sup 3} are independently selected from the group consisting of hydrogen, C{sub 1} to C{sub 10} alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C{sub 1} to C{sub 10} alkyls as a substituent, C{sub 6} to C{sub 15} aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R{sup 8}){sub 3} where R{sup 8} is selected from the group consisting of C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; R{sup 4} and R{sup 6} are substituents both having van der Waals radii larger than the van der Waals radii of groups R{sup 1} and R{sup 3}; R{sup 5} is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E{sup 1}, E{sup 2} are independently selected from the group consisting of Si(R{sup 9}){sub 2}, Si(R{sup 9}){sub 2}--Si(R{sup 9}){sub 2}, Ge(R{sup 9}){sub 2}, Sn(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}--C(R{sup 9}){sub 2}, where R{sup 9} is C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; and the ligand may have C{sub S} or C{sub 1}-symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from {alpha}-olefin monomers.

  4. Polymeric Carbon Dioxide

    SciTech Connect

    Yoo, C-S.

    1999-11-02

    Synthesis of polymeric carbon dioxide has long been of interest to many chemists and materials scientists. Very recently we discovered the polymeric phase of carbon dioxide (called CO{sub 2}-V) at high pressures and temperatures. Our optical and x-ray results indicate that CO{sub 2}-V is optically non-linear, generating the second harmonic of Nd: YLF laser at 527 nm and is also likely superhard similar to cubic-boron nitride or diamond. CO{sub 2}-V is made of CO{sub 4} tetrahedra, analogous to SiO{sub 2} polymorphs, and is quenchable at ambient temperature at pressures above 1 GPa. In this paper, we describe the pressure-induced polymerization of carbon dioxide together with the stability, structure, and mechanical and optical properties of polymeric CO{sub 2}-V. We also present some implications of polymeric CO{sub 2} for high-pressure chemistry and new materials synthesis.

  5. Copper mediated controlled radical copolymerization of styrene and 2-ethylhexyl acrylate and determination of their reactivity ratios.

    NASA Astrophysics Data System (ADS)

    Koiry, Bishnu; Singha, Nikhil

    2014-10-01

    Copolymerization is an important synthetic tool to prepare polymers with desirable combination of properties which are difficult to achieve from the different homopolymers concerned. This investigation reports the copolymerization of 2-ethylhexyl acrylate (EHA) and styrene using copper bromide (CuBr) as catalyst in combination with N,N,N’,N”,N”- pentamethyldiethylenetriamine (PMDETA) as ligand and 1-phenylethyl bromide (PEBr) as initiator. Linear kinetic plot and linear increase in molecular weights versus conversion indicate that copolymerization reactions were controlled. The copolymer composition was calculated using 1H NMR studies. The reactivity ratio of styrene and EHA (r1 and r2) were determined using the Finemann-Ross (FR), inverted Finemann-Ross (FR) and Kelen-Tudos (KT) methods. Thermal properties of the copolymers were also studied by using TGA and DSC analysis.

  6. Copper mediated controlled radical copolymerization of styrene and 2-ethylhexyl acrylate and determination of their reactivity ratios.

    PubMed

    Koiry, Bishnu P; Singha, Nikhil K

    2014-01-01

    Copolymerization is an important synthetic tool to prepare polymers with desirable combination of properties which are difficult to achieve from the different homopolymers concerned. This investigation reports the copolymerization of 2-ethylhexyl acrylate (EHA) and styrene using copper bromide (CuBr) as catalyst in combination with N,N,N',N″,N″- pentamethyldiethylenetriamine (PMDETA) as ligand and 1-phenylethyl bromide (PEBr) as initiator. Linear kinetic plot and linear increase in molecular weights vs. conversion indicate that copolymerization reactions were controlled. The copolymer composition was calculated using (1)H NMR studies. The reactivity ratio of styrene and EHA (r1 and r2) were determined using the Finemann-Ross (FR), inverted Finemann-Ross (IFR), and Kelen-Tudos (KT) methods. Thermal properties of the copolymers were also studied by using TGA and DSC analysis. PMID:25368866

  7. Catalytic living ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

    Nagarkar, Amit A.; Kilbinger, Andreas F. M.

    2015-09-01

    In living ring-opening metathesis polymerization (ROMP), a transition-metal-carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well-defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst.

  8. Radical and Atom Transfer Halogenation (RATH): A Facile Route for Chemical and Polymer Functionalization.

    PubMed

    Han, Yi-Jen; Lin, Chia-Yu; Liang, Mong; Liu, Ying-Ling

    2016-05-01

    This work demonstrates a new halogenation reaction through sequential radical and halogen transfer reactions, named as "radical and atom transfer halogenation" (RATH). Both benzoxazine compounds and poly(2,6-dimethyl-1,4-phenylene oxide) have been demonstrated as active species for RATH. Consequently, the halogenated compound becomes an active initiator of atom transfer radical polymerization. Combination of RATH and sequential ATRP provides an convenient and effective approach to prepare reactive and crosslinkable polymers. The RATH reaction opens a new window both to chemical synthesis and molecular design and preparation of polymeric materials. PMID:27027639

  9. Latent and delayed action polymerization systems.

    PubMed

    Naumann, Stefan; Buchmeiser, Michael R

    2014-04-01

    Various approaches to latent polymerization processes are described. In order to highlight recent advances in this field, the discussion is subdivided into chapters dedicated to diverse classes of polymers, namely polyurethanes, polyamides, polyesters, polyacrylates, epoxy resins, and metathesis-derived polymers. The described latent initiating systems encompass metal-containing as well as purely organic compounds that are activated by external triggers such as light, heat, or mechanical force. Special emphasis is put on the different chemical venues that can be taken to achieve true latency, which include masked N-heterocyclic carbenes, latent metathesis catalysts, and photolatent radical initiators, among others. Scientific challenges and the advantageous application of latent polymerization processes are discussed. PMID:24519912

  10. Preparation of hydrogels via ultrasonic polymerization.

    PubMed

    Cass, Peter; Knower, Warren; Pereeia, Eliana; Holmes, Natalie P; Hughes, Tim

    2010-02-01

    Several acrylic hydrogels were prepared via ultrasonic polymerization of water soluble monomers and macromonomers. Ultrasound was used to create initiating radicals in viscous aqueous monomer solutions using the additives glycerol, sorbitol or glucose in an open system at 37 degrees C. The water soluble additives were essential for the hydrogel production, glycerol being the most effective. Hydrogels were prepared from the monomers 2-hydroxyethyl methacrylate, poly(ethylene glycol) dimethacrylate, dextran methacrylate, acrylic acid/ethylene glycol dimethacrylate and acrylamide/bis-acrylamide. For example a 5% w/w solution of dextran methacrylate formed a hydrogel in 6.5min in a 70% w/w solution of glycerol in water at 37 degrees C with 20kHz ultrasound, 56Wcm(-2). The ultrasonic polymerization method described here has a wide range of applications such a biomaterial synthesis where initiators are not desired. PMID:19762267

  11. Polymeric Nanofibers in Tissue Engineering

    PubMed Central

    Dahlin, Rebecca L.; Kasper, F. Kurtis

    2011-01-01

    Polymeric nanofibers can be produced using methods such as electrospinning, phase separation, and self-assembly, and the fiber composition, diameter, alignment, degradation, and mechanical properties can be tailored to the intended application. Nanofibers possess unique advantages for tissue engineering. The small diameter closely matches that of extracellular matrix fibers, and the relatively large surface area is beneficial for cell attachment and bioactive factor loading. This review will update the reader on the aspects of nanofiber fabrication and characterization important to tissue engineering, including control of porous structure, cell infiltration, and fiber degradation. Bioactive factor loading will be discussed with specific relevance to tissue engineering. Finally, applications of polymeric nanofibers in the fields of bone, cartilage, ligament and tendon, cardiovascular, and neural tissue engineering will be reviewed. PMID:21699434

  12. Radical-radical interactions among oxidized guanine bases including guanine radical cation and dehydrogenated guanine radicals.

    PubMed

    Zhao, Jing; Wang, Mei; Yang, Hongfang; Zhang, Meng; Liu, Ping; Bu, Yuxiang

    2013-09-19

    We present here a theoretical investigation of the structural and electronic properties of di-ionized GG base pairs (G(•+)G(•+),G(-H1)(•)G(•+), and G(-H1)(•)G(-H1)(•)) consisting of the guanine cation radical (G(•+)) and/or dehydrogenated guanine radical (G(-H1)(•)) using density functional theory calculations. Different coupling modes (Watson-Crick/WC, Hoogsteen/Hoog, and minor groove/min hydrogen bonding, and π-π stacking modes) are considered. We infer that a series of G(•+)G(•+) complexes can be formed by the high-energy radiation. On the basis of density functional theory and complete active space self-consistent (CASSCF) calculations, we reveal that in the H-bonded and N-N cross-linked modes, (G(•+)G(•+))WC, (G(-H1)(•)G(-H1)(•))WC, (G(-H1)(•)G(-H1)(•))minI, and (G(-H1)(•)G(-H1)(•))minIII have the triplet ground states; (G(•+)G(•+))HoogI, (G(-H1)(•)G(•+))WC, (G(-H1)(•)G(•+))HoogI, (G(-H1)(•)G(•+))minI, (G(-H1)(•)G(•+))minII, and (G(-H1)(•)G(-H1)(•))minII possess open-shell broken-symmetry diradical-characterized singlet ground states; and (G(•+)G(•+))HoogII, (G(•+)G(•+))minI, (G(•+)G(•+))minII, (G(•+)G(•+))minIII, (G(•+)G(•+))HoHo, (G(-H1)(•)G(•+))minIII, (G(-H1)(•)G(•+))HoHo, and (G(-H1)(•)G(-H1)(•))HoHo are the closed-shell systems. For these H-bonded diradical complexes, the magnetic interactions are weak, especially in the diradical G(•+)G(•+) series and G(-H1)(•)G(-H1)(•) series. The magnetic coupling interactions of the diradical systems are controlled by intermolecular interactions (H-bond, electrostatic repulsion, and radical coupling). The radical-radical interaction in the π-π stacked di-ionized GG base pairs ((G(•+)G(•+))ππ, (G(-H1)(•)G(•+))ππ, and (G(-H1)(•)G(-H1)(•))ππ) are also considered, and the magnetic coupling interactions in these π-π stacked base pairs are large. This is the first theoretical prediction that some di

  13. Hydrocarbon polymeric binder for advanced solid propellant

    NASA Technical Reports Server (NTRS)

    Potts, J. E. (Editor)

    1972-01-01

    A series of DEAB initiated isoprene polymerizations were run in the 5-gallon stirred autoclave reactor. Polymerization run parameters such as initiator concentration and feed rate were correlated with the molecular weight to provide a basis for molecular weight control in future runs. Synthetic methods were developed for the preparation of n-1,3-alkadienes. By these methods, 1,3-nonadiene was polymerized using DEAB initiator to give an ester-telechelic polynonadiene. This was subsequently hydrogenated with copper chromite catalyst to give a hydroxyl terminated saturated liquid hydrocarbon prepolymer having greatly improved viscosity characteristics and a Tg 18 degrees lower than that of the hydrogenated polyisoprenes. The hydroxyl-telechelic saturated polymers prepared by the hydrogenolysis of ester-telechelic polyisoprene were reached with diisocyanates under conditions favoring linear chain extension gel permeation chromatography was used to monitor this condensation polymerization. Fractions having molecular weights above one million were produced.

  14. Intriguing Morphology Evolution from Noncrosslinked Poly(tert-butyl acrylate) Seeds with Polar Functional Groups in Soap-Free Emulsion Polymerization of Styrene.

    PubMed

    Wang, Lu; Pan, Mingwang; Song, Shaofeng; Zhu, Lei; Yuan, Jinfeng; Liu, Gang

    2016-08-01

    Herein, we demonstrate a facile approach to prepare anisotropic poly(tert-butyl acrylate)/polystyrene (PtBA/PS) composite particles with controllable morphologies by soap-free seeded emulsion polymerization (SSEP). In the first step, noncrosslinked PtBA seeds with self-stabilizing polar functional groups (e.g., ester groups and radicals) are synthesized by soap-free emulsion polymerization. During the subsequent SSEP of styrene (St), PS bulges are nucleated on the PtBA seeds due to the microphase separation confined in the latex particles. The morphology evolution of PtBA/PS composite particles is tailored by varying the monomer/seed feed ratio, polymerization time, and polymerization temperature. Many intriguing morphologies, including hamburger-like, litchi-like, mushroom-like, strawberry-like, bowl-like, and snowman-like, have been acquired for PtBA/PS composite particles. The polar groups on the PtBA seed surface greatly influence the formation and further merging of PS/St bulges during the polymerization. A possible formation mechanism is proposed on the basis of experimental results. These complex composite particles are promising for applications in superhydrophobic coatings. PMID:27389855

  15. The Effect of Nanoconfinemnt on Methyl Methacrylate Polymerization: Reactivity and Resulting Properties

    NASA Astrophysics Data System (ADS)

    Zhao, Haoyu; Yu, Ziniu; Hedden, Ronald; Simon, Sindee

    2014-03-01

    The effect of nanoconfinement is well known to affect the properties of polymers. In this work, free radical polymerization of methyl methacrylate (MMA) is performed in hydrophilic or hydrophobic 13 nm diameter controlled pore glass (CPG). Changes in polymerization kinetics and the properties of the synthesized polymer are quantified. Reaction kinetics and glass transition temperatures are followed by differential scanning calorimetry (DSC). After polymerization, the changes in the molecular weights and tacticity are measured using gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (1H NMR). Nanoconfinement is found to result in earlier onset of autoacceleration leading to the increase in both number-average and weight-average molecular weights, whereas the polydispersity index at full conversion decreases relative to the bulk value. Moreover, for both pore surfaces, the glass transition temperature increases compared with the bulk, but the increase in hydrophilic pores is more pronounced at 20 °C. In addition to the changes in molecular weight and Tg, the tacticity changes from syndiotactic-rich triads for the bulk PMMA to a higher percentage of isotacticity under nanoconfinement. Funding from the National Science Foundation CMMI 0826437 and CRIF MU grant CHE-1048553 is gratefully acknowledged.

  16. Near-Infrared-Light-Assisted Photothermal Polymerization for Transdermal Hydrogelation and Cell Delivery.

    PubMed

    Lee, Hwangjae; Chung, Solchan; Kim, Min-Gon; Lee, Luke P; Lee, Jae Young

    2016-07-01

    Photopolymerization of hydrogels has been widely used to encapsulate cells and support their growth in 3D environments. However, common light sources (i.e., ultraviolet and visible light) strongly interact with biological systems and are therefore inappropriate for in vivo applications, such as transdermal polymerization. Using near infrared (NIR) light that minimally interacts with living tissues, this study investigates NIR light-assisted photothermal polymerization (NAPP) of diacrylated polyethylene glycol (PEGDA), in which interactions between NIR light and gold nanorods activate a thermal initiator (i.e., AIPH), resulting in generation of radicals for polymerization of PEGDA. Gelation parameters, including precursor concentrations and NIR power, are investigated to minimize the use of initiator and temperature increases (<43 °C) during NAPP. Cell viability is as high as 80% after NAPP-based encapsulation. Incorporation of polyethylene glycol (PEG) modified with a cell-adhesive peptide moiety (Arg-Gly-Asp) into the gel system further enables prolongation of cell viability during incubation up to 7 d. NAPP results in successful transdermal gelation and good viability of the transplanted cells. Thus, this new cell encapsulation approach, demonstrated for the first time in this study, will benefit various applications, including cell delivery and remote control over cellular environments. PMID:27109186

  17. Penile vibratory stimulation in the recovery of urinary continence and erectile function after nerve-sparing radical prostatectomy: a randomized, controlled trial

    PubMed Central

    Fode, Mikkel; Borre, Michael; Ohl, Dana A; Lichtbach, Jonas; Sønksen, Jens

    2014-01-01

    Objective To examine the effect of penile vibratory stimulation (PVS) in the preservation and restoration of erectile function and urinary continence in conjunction with nerve-sparing radical prostatectomy (RP). Patients and Methods The present study was conducted between July 2010 and March 2013 as a randomized prospective trial at two university hospitals. Eligible participants were continent men with an International Index of Erectile Function-5 (IIEF-5) score of at least 18, scheduled to undergo nerve-sparing RP. Patients were randomized to a PVS group or a control group. Patients in the PVS group were instructed in using a PVS device (FERTI CARE® vibrator). Stimulation was performed at the frenulum once daily by the patients in their own homes for at least 1 week before surgery. After catheter removal, daily PVS was re-initiated for a period of 6 weeks. Participants were evaluated at 3, 6 and 12 months after surgery with the IIEF-5 questionnaire and questions regarding urinary bother. Patients using up to one pad daily for security reasons only were considered continent. The study was registered at http://clinicaltrials.gov/ (NCT01067261). Results Data from 68 patients were available for analyses (30 patients randomized to PVS and 38 patients randomized to the control group). The IIEF-5 score was highest in the PVS group at all time points after surgery with a median score of 18 vs 7.5 in the control group at 12 months (P = 0.09), but the difference only reached borderline significance. At 12 months, 16/30 (53%) patients in the PVS group had reached an IIEF-5 score of at least 18, while this was the case for 12/38 (32%) patients in the control group (P = 0.07). There were no significant differences in the proportions of continent patients between groups at 3, 6 or 12 months. At 12 months 90% of the PVS patients were continent, while 94.7% of the control patients were continent (P = 0.46). Conclusion The present study did not document a significant effect of

  18. Modeling the chemistry of plasma polymerization using mass spectrometry.

    PubMed

    Ihrig, D F; Stockhaus, J; Scheide, F; Winkelhake, Oliver; Streuber, Oliver

    2003-04-01

    The goal of the project is a solvent free painting shop. The environmental technologies laboratory is developing processes of plasma etching and polymerization. Polymerized thin films are first-order corrosion protection and primer for painting. Using pure acetylene we get very nice thin films which were not bonded very well. By using air as bulk gas it is possible to polymerize, in an acetylene plasma, well bonded thin films which are stable first-order corrosion protections and good primers. UV/Vis spectroscopy shows nitrogen oxide radicals in the emission spectra of pure nitrogen and air. But nitrogen oxide is fully suppressed in the presence of acetylene. IR spectroscopy shows only C=O, CH(2) and CH(3) groups but no nitrogen species. With the aid of UV/Vis spectra and the chemistry of ozone formation it is possible to define reactive traps and steps, molecule depletion and processes of proton scavenging and proton loss. Using a numerical model it is possible to evaluate these processes and to calculate theoretical mass spectra. Adjustment of theoretical mass spectra to real measurements leads to specific channels of polymerization which are driven by radicals especially the acetyl radical. The estimated theoretical mass spectra show the specific channels of these chemical processes. It is possible to quantify these channels. This quantification represents the mass flow through this chemical system. With respect to these chemical processes it is possible to have an idea of pollutant production processes. PMID:12707764

  19. Molecularly Regulated Reversible DNA Polymerization.

    PubMed

    Chen, Niancao; Shi, Xuechen; Wang, Yong

    2016-06-01

    Natural polymers are synthesized and decomposed under physiological conditions. However, it is challenging to develop synthetic polymers whose formation and reversibility can be both controlled under physiological conditions. Here we show that both linear and branched DNA polymers can be synthesized via molecular hybridization in aqueous solutions, on the particle surface, and in the extracellular matrix (ECM) without the involvement of any harsh conditions. More importantly, these polymers can be effectively reversed to dissociate under the control of molecular triggers. Since nucleic acids can be conjugated with various molecules or materials, we anticipate that molecularly regulated reversible DNA polymerization holds potential for broad biological and biomedical applications. PMID:27100911

  20. Nitric oxide-releasing polymeric nanoparticles against Trypanosoma cruzi

    NASA Astrophysics Data System (ADS)

    Seabra, A. B.; Kitice, N. A.; Pelegrino, M. T.; Lancheros, C. A. C.; Yamauchi, L. M.; Pinge-Filho, P.; Yamada-Ogatta, S. F.

    2015-05-01

    Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite, Trypanosoma cruzi (T. cruzi), and the disease remains a major health problem in many Latin American countries. Several papers report that the killing of the parasite is dependent on the production of nitric oxide (NO). The endogenous free radical NO is an important cellular signalling molecule that plays a key role in the defense against pathogens, including T. cruzi. As T. cruzi is able to compromise host macrophages decreasing endogenous NO production, the administration of exogenous NO donors represents an interesting strategy to combat Chagas disease. Thus, the aims of this study were to prepare and evaluate the antimicrobial activity of NO-releasing polymeric nanoparticles against T. cruzi. Biocompatible polymeric nanoparticles composed of chitosan/sodium tripolyphosphate(TPP) were prepared and used to encapsulate mercaptosuccinic acid (MSA), which is a thiol-containing molecule. Nitrosation of free thiols (SH) groups of MSA were performed by the addition of equimolar amount of sodium nitrite (NaNO2), leading to the formation of S-nitroso-MSA-containing nanoparticles. These polymeric nanoparticles act as spontaneous NO donors, with free NO release. The results show the formation of nanoparticles with average hydrodynamic diameter ranging from 270 to 500 nm, average of polydispersity index of 0.35, and encapsulation efficiency in the range of 99%. The NO release kinetics from the S-nitroso-MSA-containing nanoparticles showed sustained and controlled NO release over several hours. The microbicidal activity of S-nitroso-MSA-containing nanoparticles was evaluated by incubating NO-releasing nanoparticles (200 - 600 μg/mL) with replicative and non-infective epimastigote, and non-replicative and infective trypomastigote forms of T. cruzi. In addition, a significant decrease in the percentage of macrophage-infected (with amastigotes) and

  1. Mechanism of plasma polymerization of methyl methacrylate

    SciTech Connect

    Denes, F.; Sarmadi, A.M.; Hop, C.E.C.A.; Young, R.A.

    1993-12-31

    Molecular fragments from radio-frequency plasma polymerization of methylmethacrylate (MMA) were cold-trapped and characterized by gas chromatography-mass spectroscopy (GC/MS). The gas phase and the liquid phase products from the cold trap were analyzed separately. The gas phase contained a predominance of the saturated aliphatic compounds butane, pentane, and isopentane and unsaturated l-butene, in addition to saturated MMA monomer (methyl isobutyrate); the liquid phase contained mainly isopropenyl alcohol, saturated MMA and a methylated form of the saturated MMA. Calculations of the predominant plasma-generated molecular clusters using the CG/MS data for both the gas and liquid phases indicated that saturated and unsaturated propyl radicals (molecular weight 41-43) were by far the predominant radical species in the plasma reactions and would lead to a hydrocarbon-type polymer with considerable unsaturation and crosslinking. The occurrence of other radical species containing methyl ester and hydroxyl groups accounts for the presence of these functional groups in the final polymer. Infrared and ultraviolet spectra confirmed the participation of the predominant aliphatic radicals in the formation of PPMMA. Clearly PPMA is a distinctly different polymer when compared to conventional PMMA.

  2. Polymerization catalyst system

    SciTech Connect

    Graves, V.

    1986-03-25

    This patent describes a catalyst system for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization. This system consists of: 1. a supported polymerization catalyst or mixture of polymerization catalysts prepared under anhydrous conditions by the sequential steps of: (a) preparing a slurry of inert particulate porous support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium halide compound; and (f) recovering solid catalyst component; 2. an organoaluminum compound; and 3. a promotor of chlorinated hydrocarbons having one to 20 carbon atoms.

  3. Ellipsometry and energy characterization of the electron impact polymerization in the range 0-20 eV

    NASA Astrophysics Data System (ADS)

    Zyn, V. I.

    2016-05-01

    The electron impact polymerization of adsorbed vapors of a hydrocarbon vacuum oil with molecular mass 450 Da (C32H66) has been studied in-situ in the range 0-20 eV using ellipsometry and a servo system with the Kelvin's vibrating probe. This allowed registering at the same time the two energy-dependent characteristics (spectra) of the process: the film growth rate and the electrical potential of the irradiated surface. The first spectrum has two resonance maxima near 2.5 and 9.5 eV while the surface potential has only one weak extremum near 9.5 eV. The first growth rate peak at 2.5 eV was connected with a creation of radicals through a resonant process of the dissociative electron attachment and beginning polymerization. The peaks at 9.5 eV in both the spectra mean accelerating polymerization and decreasing surface charge owing to simultaneous birth of highly active radicals and free electrons. The single resonant process controlling both the processes simultaneously is the dissociative attachment of an electron to an anti-bonding molecular orbital, almost the same as at the 2.5 eV but differing by deeper decomposition of the transient anion, among the products of which are now not the radicals only but also free electrons. The kinetic curves obtained in pulsed regimes of the electron bombardment were qualitatively identical for different precursors and were used for calculations of cross sections of these processes.

  4. Mechanism of Cyclic Dye Regeneration During Eosin-Sensitized Photoinitiation in the Presence of Polymerization Inhibitors

    PubMed Central

    Avens, Heather J.; Bowman, Christopher N.

    2009-01-01

    A visible light photoinitiator, eosin, in combination with a tertiary amine coinitiator is found to initiate polymerization despite the presence of at least 1000-fold excess dissolved oxygen which functions as an inhibitor of radical polymerizations. Additionally, 0.4 µM eosin is able to overcome 100-fold excess (40 µM) 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) inhibitor, initiating polymerization after only a 2 minute inhibition period. In contrast, 40 µM Irgacure-2959, a standard cleavage-type initiator, is unable to overcome even an equivalent amount of inhibitor (40 µM TEMPO). Through additional comparisons of these two initiation systems, a reaction mechanism is developed which is consistent with the kinetic data and provides an explanation for eosin’s relative insensitivity to oxygen, TEMPO and other inhibitors. A cyclic mechanism is proposed in which semi-reduced eosin radicals react by disproportionation with radical inhibitors and radical intermediates in the inhibition process to regenerate eosin and effectively consume inhibitor. In behavior similar to that of eosin, rose bengal, fluorescein, and riboflavin are also found to initiate polymerization despite the presence of excess TEMPO, indicating that cyclic regeneration likely enhances the photoinitiation kinetics of many dye photosensitizers. Selection of such dye initiation systems constitutes a valuable strategy for alleviating inhibitory effects in radical polymerizations. PMID:20098667

  5. FROM ATOM TRANSFER RADICAL ADDITION TO ATOM TRANSFER RADICAL POLYMERIZATION. (R829580)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  6. Polymeric materials for neovascularization

    NASA Astrophysics Data System (ADS)

    DeVolder, Ross John

    Revascularization therapies have emerged as a promising strategy to treat various acute and chronic wounds, cardiovascular diseases, and tissue defects. It is common to either administer proangiogenic growth factors, such as vascular endothelial growth factor (VEGF), or transplant cells that endogenously express multiple proangiogenic factors. Additionally, these strategies utilize a wide variety of polymeric systems, including hydrogels and biodegradable plastics, to deliver proangiogenic factors in a sophisticated manner to maintain a sustained proangiogenic environment. Despite some impressive results in rebuilding vascular networks, it is still a challenging task to engineer mature and functional neovessels in target tissues, because of the increasing complexities involved with neovascularization applications. To resolve these challenges, this work aims to design a wide variety of proangiogenic biomaterial systems with tunable properties used for neovascularization therapies. This thesis describes the design of several biomaterial systems used for the delivery of proangiogenic factors in neovascularization therapies, including: an electrospun/electrosprayed biodegradable plastic patch used for directional blood vessel growth (Chapter 2), an alginate-g-pyrrole hydrogel system that biochemically stimulates cellular endogenous proangiogenic factor expression (Chapter 3), an enzyme-catalyzed alginate-g-pyrrole hydrogel system for VEGF delivery (Chapter 4), an enzyme-activated alginate-g-pyrrole hydrogel system with systematically controllable electrical and mechanical properties (Chapter 5), and an alginate-g-pyrrole hydrogel that enables the decoupled control of electrical conductivity and mechanical rigidity and is use to electrically stimulate cellular endogenous proangiogenic factor expression (Chapter 6). Overall, the biomaterial systems developed in this thesis will be broadly useful for improving the quality of a wide array of molecular and cellular based

  7. Reassessing Radical Pedagogy.

    ERIC Educational Resources Information Center

    Sweet, Stephen

    1998-01-01

    Responds to comments about, and critiques of, his own article on radical pedagogy. Outlines major points of contention raised by other commentators and responds to them, including matters of definition, power relations in the classroom, and tempering radical theory with pragmatism. (DSK)

  8. [Alchemists' humid radical].

    PubMed

    Lafont, Olivier

    2007-01-01

    The term radical has been used by chemists since the beginnings and even when they still were alchemists. The term "humid radical" is present in numerous alchemists' texts. It was used to represent a kind of "humid", which was considered as different from what is nowadays called "humid", but was a sort of principle necessary for life. PMID:17575839

  9. Self-Organized and Cu-Coordinated Surface Linear Polymerization

    PubMed Central

    Li, Qing; Owens, Jonathan R.; Han, Chengbo; Sumpter, Bobby G.; Lu, Wenchang; Bernholc, Jerzy; Meunier, V.; Maksymovych, Peter; Fuentes-Cabrera, Miguel; Pan, Minghu

    2013-01-01

    We demonstrate a controllable surface-coordinated linear polymerization of long-chain poly(phenylacetylenyl)s that are self-organized into a “circuit-board” pattern on a Cu(100) surface. Scanning tunneling microscopy/spectroscopy (STM/S) corroborated by ab initio calculations, reveals the atomistic details of the molecular structure, and provides a clear signature of electronic and vibrational properties of the poly(phenylacetylene)s chains. Notably, the polymerization reaction is confined epitaxially to the copper lattice, despite a large strain along the polymerized chain that subsequently renders it metallic. Polymerization and depolymerization reactions can be controlled locally at the nanoscale by using a charged metal tip. This control demonstrates the possibility of precisely accessing and controlling conjugated chain-growth polymerization at low temperature. This finding may lead to the bottom-up design and realization of sophisticated architectures for molecular nano-devices. PMID:23811605

  10. Fiber optical beam shaping using polymeric structures

    NASA Astrophysics Data System (ADS)

    Rodrigues Ribeiro, R. S.; Queirós, R. B.; Guerreiro, A.; Ecoffet, C.; Soppera, O.; Jorge, P. A. S.

    2014-05-01

    A method to control the output intensity profile of optical fibers is presented. Using guided wave photopolymerization in multimode structures the fabrication with modal assisted shaping of polymeric micro lenses is demonstrated. Results showing that a given linear polarized mode can be selectively excited controlling the intensity distribution at the fiber tip are presented. This pattern is then reproduced in the polymeric micro structure fabricated at the fiber tip thus modulating its output intensity distribution. Such structures can therefore be used to obtain at the fiber tip predetermined intensity patterns for attaining optical trapping or patterned illumination.

  11. Effect of molecular oxygen on the UV-polymerization of methyl methacrylate initiated by 2,2-dimethoxy-2-phenylaceto-phenone and 1-hydroxycyclohexyl phenyl ketone in solution

    SciTech Connect

    Phan, X.T.

    1986-01-01

    The photopolymerization of methyl methacrylate (MMA) in a dilute benzene solution containing 2,2-dimethoxy-2-phenylacetophenone (DMPA) or 1-hydroxycyclohexyl phenyl ketone (HCPK) was investigated. Product analyses indicate that under a nitrogen atmosphere in the presence of MMA both radicals from HCPK are involved in polymerization of MMA whereas only 30% of the benzoyl radicals and 15% of the 1,1-dimethoxybenzyl radicals from DMPA are involved in radical polymerization. Under an oxygen atmosphere, products are formed in increased amounts, resulting in fewer radicals available for polymerization. The polymerization is inhibited by oxygen, as shown by a five-fold decrease in polymerization quantum efficiency, and lower yields of poly(methyl methacrylate). The addition of amines is not effective in relieving this effect.

  12. Evaluation of Multivalent, Functional Polymeric Nanoparticles for Imaging Applications

    PubMed Central

    Shokeen, Monica; Pressly, Eric D.; Hagooly, Aviv; Zheleznyak, Alexander; Ramos, Nicholas; Fiamengo, Ashley L.; Welch, Michael J.; Hawker, Craig J.; Anderson, Carolyn J.

    2011-01-01

    A series of multivalent, functional polymer nanoparticles with diagnostic/imaging units and targeting ligands for molecular targeting were synthesized with the loading of the chain end functionalized, GRGDS peptide targeting sequence (model system based on integrin αvβ3) ranging from 0 to 50%. Accurate structural and functional group control in these systems was achieved through a modular approach involving the use of multiple functionalized macromonomer/monomer units combined with living free radical polymerization. In cellulo results show an increase in uptake in αvβ3 integrin-positive U87MG glioblastoma cells with increasing RGD loading and a possible upper limit on the effectiveness of the number of RGD peptides for targeting αvβ3 integrin. Significantly, this increased targeting efficiency is coupled with in vivo biodistribution results which show decreased blood circulation and increased liver uptake with increasing RGD loading. The results demonstrate the importance of controlling ligand loading in order to achieve optimal performance for therapeutic and imaging applications for multivalent nanoparticle based systems. PMID:21275414

  13. [Robotic laparoscopic radical prostatectomy: update 2008].

    PubMed

    John, H

    2008-03-01

    Radical prostatectomy aims for optimal tumor control, minimal morbidity, and best functional outcomes of urinary continence and erection. With the introduction of the robotic daVinci surgical system an impressive shift from open radical to robotic laparoscopic prostatectomy (RLP) has occurred especially in the USA. Unfortunately, initial and instrumental costs and maintenance fees of the system are still very high. Compared with the open retropubic approach, RLP has a similar short-term outcome in oncological control, potency, and urinary continence but potentially distinctly favorable benefits in blood loss, transfusion rates, and minor complications. However, RLP is still in its infancy compared to open radical prostatectomy. Inter-institutional trials with the same validated questionnaires are necessary for the future to evaluate oncological and functional results conclusively. The individual surgeon's experience with his routinely preferred technique remains the crucial key for a successful oncological and functional outcome in radical prostatectomy, whatever technology is used. PMID:18231769

  14. Accelerated crystallization of zeolites via hydroxyl free radicals.

    PubMed

    Feng, Guodong; Cheng, Peng; Yan, Wenfu; Boronat, Mercedes; Li, Xu; Su, Ji-Hu; Wang, Jianyu; Li, Yi; Corma, Avelino; Xu, Ruren; Yu, Jihong

    2016-03-11

    In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH(-)) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al-O-Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al-O-Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites-such as Na-A, Na-X, NaZ-21, and silicalite-1-can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton's reagent. PMID:26965626

  15. Design and synthesis of pH-sensitive polymeric micelles for oral delivery of poorly water-soluble drugs.

    PubMed

    Yang, Xiaolan; Fan, Rongrong; Wang, Wenlong; Wang, Jiexin; Le, Yuan

    2016-09-01

    pH-sensitive polymer poly (polylactide-co-methacrylic acid)-b-poly (acrylic acid) was synthesized using atom transfer radical polymerization and ring-opening polymerization and characterized by gel permeation chromatography and (1)H NMR. The polymers can self-assemble to form micelles in aqueous medium, which respond rapidly to pH change within the gastrointestinal relevant pH range. Critical micelle concentrations and pH response behavior of the polymeric micelle were investigated. Water-insoluble drug nifedipine was loaded and the drug-loading content can be controlled by tuning the composition of the polymers. The in vitro release studies indicate pH sensitivity enabled rapid drug release at the environment of simulated intestinal fluid (pH 7.36), the cumulative released amount of NFD reached more than 80% within 24 h, while only 35% in the simulated gastric fluid (pH 1.35). All the results showed that the pH-sensitive P(PLAMA-co-MAA)-b-PAA micelle may be a prospective candidate as oral drug delivery carrier for hydrophobic drugs with controlled release behavior. PMID:27342342

  16. Evaluation of antibacterial activity of nitric oxide-releasing polymeric particles against Staphylococcus aureus and Escherichia coli from bovine mastitis.

    PubMed

    Cardozo, Viviane F; Lancheros, Cesar A C; Narciso, Adélia M; Valereto, Elaine C S; Kobayashi, Renata K T; Seabra, Amedea B; Nakazato, Gerson

    2014-10-01

    Bovine mastitis is a serious veterinary disease that causes great loss to the dairy industry worldwide. It is a major infectious disease and is difficult to manage and control. Furthermore, emerging multidrug resistant bacteria that cause mastitis have complicated such management. The free radical nitric oxide (NO) is a potent antimicrobial agent. Thus, the aims of this study were to prepare and evaluate the antibacterial activity of nitric oxide-releasing polymeric particles against Staphylococcus aureus (MBSA) and Escherichia coli (MBEC), which were isolated from bovine mastitis. Fifteen MBSA isolates and fifteen MBEC were collected from subclinical and clinical bovine mastitis. Biocompatible polymeric particles composed of alginate/chitosan or chitosan/sodium tripolyphosphate (TPP) were prepared and used to encapsulate mercaptosuccinic acid (MSA), which is a thiol-containing molecule. Nitrosation of thiol groups of MSA-containing particles formed S-nitroso-MSA particles, which are NO donors. The NO release kinetics from the S-nitroso-MSA particles showed sustained and controlled NO release over several hours. The antibacterial activity of NO-releasing particles was evaluated by incubating the particles with an MBSA multi-resistant strain, which is responsible for bovine mastitis. The minimum inhibitory concentration for S-nitroso-MSA-alginate/chitosan particles against MBSA ranged from 125 μg/mL to 250 μg/mL. The results indicate that NO-releasing polymeric particles are an interesting approach to combating bacteria resistance in bovine mastitis treatment and prevention. PMID:24979535

  17. Radical chemistry of artemisinin

    NASA Astrophysics Data System (ADS)

    Denisov, Evgenii T.; Solodova, S. L.; Denisova, Taisa G.

    2010-12-01

    The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

  18. Polymeric compositions, method for their preparation, and lubricants containing them

    SciTech Connect

    Coleman, L.E.

    1980-03-25

    Compositions useful as multi-purpose lubricant and functional fluid additives and as thickeners and antisag additives for resins, paints and the like are prepared by free radical polymerization of at least one ethylenically unsaturated monomer in the presence of an oil-soluble dispersant. The carboxylic dispersants are preferred, especially esters of hydrocarbonsubstituted succinic acids wherein the substituent contains at least about 30 carbon atoms and the reaction products of such acids or their derivatives with amines, usually polyalkylene polyamines.

  19. Hybrid polymeric hydrogels for ocular drug delivery: nanoparticulate systems from copolymers of acrylic acid-functionalized chitosan and N-isopropylacrylamide or 2-hydroxyethyl methacrylate

    NASA Astrophysics Data System (ADS)

    Barbu, Eugen; Verestiuc, Liliana; Iancu, Mihaela; Jatariu, Anca; Lungu, Adriana; Tsibouklis, John

    2009-06-01

    Nanoparticulate hybrid polymeric hydrogels (10-70 nm) have been obtained via the radical-induced co-polymerization of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate, and the materials have been investigated for their ability to act as controlled release vehicles in ophthalmic drug delivery. Studies on the effects of network structure upon swelling properties, adhesiveness to substrates that mimic mucosal surfaces and biodegradability, coupled with in vitro drug release investigations employing ophthalmic drugs with differing aqueous solubilities, have identified nanoparticle compositions for each of the candidate drug molecules. The hybrid nanoparticles combine the temperature sensitivity of N-isopropylacrylamide or the good swelling characteristics of 2-hydroxyethyl methacrylate with the susceptibility of chitosan to lysozyme-induced biodegradation.

  20. Polymerization process for carboxyl containing polymers utilizing oil soluble ionic surface active agents

    SciTech Connect

    Uebele, C.E.; Ball, L.E.; Jorkasky, R.J. II; Wardlow, E. Jr.

    1987-09-08

    This patent describes a method for polymerizing olefinically unsaturated carboxylic acid monomers containing at least one activated carbon to carbon olefinic double bond and at least one carboxyl group. The monomers are polymerized in an organic media consisting essentially of organic liquids, in the presence of free radical forming catalysts and at least one oil soluble ionic surface active agent selected from the group consisting of: (a) anionic surface active agents; (b) cationic surface active agents; and (c) amphoteric surface active agents.