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Sample records for polyethylene oxide copolymer

  1. Microviscosity in Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer micelles

    SciTech Connect

    Nivaggioli, T.; Tsao, B.; Alexandridis, P.; Hatton, T.A. )

    1995-01-01

    The micellar microviscosity afforded by Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer aqueous solutions has been investigated by fluorescence and NMR spectroscopy. Comparison is made with bulk poly(propylene oxide) (PPO) samples of different molecular weights. The microviscosity in Pluronic PEO-PPO-PEO copolymer micelles is much larger than that observed in conventional surfactant micelles and depends strongly on the size of the hydrophobic PPO block: the larger this block, the higher the viscosity. Above the critical micellar temperature (CMT), as temperature increases, the microviscosity decreases. However, this decrease is not as important as that observed in bulk PPO. Hence, the relative microviscosity, defined as the ratio of the two observed phenomena, increases. This suggests structural transformation of the micelles resulting in a core becoming more and more compact as temperature increases. Such results have been confirmed by NMR studies that showed broadening of the PPO peak and relatively constant spin-lattice relaxation time, T[sub i], with increasing temperature while the PEO signal remained relatively sharp with an exponential increase in T[sub 1]. 30 refs., 9 figs., 1 tab.

  2. Surface activity of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers

    SciTech Connect

    Alexandridis, P.; Athanassiou, V.; Fukuda, Shinya; Hatton, T.A. )

    1994-08-01

    The surface tension of aqueous solutions of seven poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) Pluronic copolymers, covering a wide range of molecular weights (3400-14600) and PPO/PEO ratios (0.19-1.79), was determined over the 10[sup [minus]5]-10% w/v concentration range, at two temperatures (25 and 35[degree]C). Two breaks (changes in slope) were observed in the surface tension vs log concentration curve for most of the copolymers. The low-concentration break, occurring at bulk copolymer concentrations of approximately 10[sup [minus]3]%, is believed to originate from rearrangement of the copolymer molecules on the surface at complete coverage of the air/water interface. The breaks at the high-concentration part of the surface tension curve occurred at concentrations that correspond to the critical micellization concentration values as determined by a dye solubilization technique. The surface area per copolymer molecule, A, increased as a function of the number of EO segments, N[sub EO], obeying a scaling law (A [approx] N[sub EO][sup 1/2]) similar to that of lower molecular weight C[sub i]E[sub j] nonionic surfactants. 56 refs., 6 figs., 2 tabs.

  3. Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association

    SciTech Connect

    Alexandridis, P.; Hatton, T.A. . Dept. of Chemical Engineering); Holzwarth, J.F. )

    1994-04-25

    The critical micellization temperature (cmt) and critical micellization concentration (cmc) values of 12 Pluronic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, covering a wide range of molecular weights (2,900--14,600) and PPO/PEO ratios (0.19--1.79), were determined employing a dye solubilization method. A closed association model was found to describe adequately the copolymer micellization process for the majority of the Pluronics and used to obtain the standard free energies ([Delta]G[degree]), enthalpies ([Delta]H[degree]), and entropies ([Delta]S[degree]) of micellization. It was determined that the micellization process is entropy-driven and has an endothermic micellization enthalpy. The hydrophobic part of the Pluronics, PPO, was responsible for the micellization, apparently due to diminishing hydrogen bonding between water and PPO with increasing temperature. The cmc dependence on temperature and size of headgroup (PEO) of Pluronics follows a similar trend with lower molecular weight C[sub i]E[sub j] nonionic surfactants, the effect of temperature being more pronounced with the Pluronics. The PEO-PPO-PEO block copolymers were compared to PPO-PEO-PPO block and PEO-PPO random copolymers, in an attempt to probe the effect of molecular architecture in the formation of micelles. No micelles were observed in aqueous PPO-PEO-PPO block copolymer solutions with increasing temperature, up to the cloud point.

  4. Ionic Conductivity of Poly(ethylene oxide)-Containing Block Copolymers at Order-Disorder and Order-Order Transitions

    NASA Astrophysics Data System (ADS)

    Wanakule, Nisita; Panday, Ashoutosh; Mullin, Scott; Balsara, Nitash

    2009-03-01

    The order-disorder transition (ODT) and order-order transition (OOT) of block copolymers with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salts are measured with a combination of small-angle x-ray scattering (SAXS) and birefringence. The block copolymers comprise of polyethylene oxide (PEO), a polymer with a higher dielectric constant that dissolves LiTFSI, and polystyrene (PS), a polymer with a lower dielectric constant that does not dissolve LiTFSI. Ionic conductivity of the block copolymers are measured through the observed ODT and OOT. The effect of morphology on the ionic conductivity will be presented and compared with literature results.

  5. Local Structure and Ion Transport in Glassy Poly(ethylene oxide styrene) Copolymers

    NASA Astrophysics Data System (ADS)

    Yang, Han-Chang; Mays, Jimmy; Sokolov, Alexei P.; Winey, Karen I.

    2014-03-01

    Polymer electrolytes have attracted attention for a wide variety of applications in energy production such as lithium-ion batteries and fuel cells. The concept of free volume provides important information about ion mobility and chain dynamics in the polymer matrix. Researchers have recently demonstrated that ion transport in glassy polymer can be improved by designing a system with high free volume. We have studied the effect of temperature and humidity on the intermolecular correlations of poly(ethylene oxide styrene-block-styrene) (PEOSt- b-St) block copolymer and poly(ethylene oxide styrene) (PEOSt) homopolymer using in situ multi-angle x-ray scattering across a wide range of scattering angles (q = 0.007-1.5 Å-1) . An increase in backbone-to-backbone distance is observed, indicating an increase in free volume between different polymer main chains. Structural characterization of the polymer segments will be discussed together with conductivity and dielectric results to better understand the ion transport mechanism in the local environment of the polymer system. Department of Chemistry, University of Tennessee.

  6. Lithium-Salt-Containing High-Molecular-Weight Polystyrene-block-Polyethylene Oxide Block Copolymer Films.

    PubMed

    Metwalli, Ezzeldin; Rasool, Majid; Brunner, Simon; Müller-Buschbaum, Peter

    2015-08-10

    Ionic conductivity in relation to the morphology of lithium-doped high-molecular-weight polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymer films was investigated as solid-state membranes for lithium-ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt-doping level and the temperature. The PEO crystallites completely vanished at a salt-doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS-b-PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded-like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt-doping level.

  7. Mesoscopic simulation of a micellar poly(N-isopropyl acrylamide)-b-(polyethylene oxide) copolymer system

    NASA Astrophysics Data System (ADS)

    Bautista-Reyes, Rubén; Soto-Figueroa, César; Vicente, Luis

    2016-05-01

    In this article we studied the micellar formation of poly(N-isopropyl acrylamide)-b-polyethylene oxide (PNIPAM-b-PEO) copolymers in an aqueous system. From molecular simulations the dependence on temperature of the Flory-Huggins interaction parameter χ for PNIPAM and PEO in water is obtained and compared with available experimental results and values from other theoretical calculations. By means of dissipative particle dynamics (DPD) we then simulated the coil-globule transition for PNIPAM chains in water with a transition temperature of around 305 K. The simulations for PNIPAM-b-PEO copolymers showed that at room temperature the chains are miscible in an aqueous phase but with a temperature increase the system turns into micelles at T  =  305 K. The change in micelle anisotropy due to a different ratio PNIPAM/PEO of chains is also analyzed. What is observed is that for large PEO the large number of dissolved PEO chains gives a large corona size and the micelle is not spherical but obloide and as the number of PNIPAM is increased the micelle acquires a spherical shape. As an important application we considered the system micelle-water/anionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]+[PF6]-). By increasing the temperature of the system from 306 K it is shown that at T  =  345 K there is a transfer of the micelle from water to the ionic liquid phase and this was due to the change in the relative affinity of PEO to water and ionic liquid expressed by the change in χ. All the simulation outcomes are qualitatively consistent with experimental results and thus to our knowledge we give the first set of χ values for the interaction between PNIPAM and water in a wide range of temperature values.

  8. Multiple phase transition and scaling law for poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in aqueous solution.

    PubMed

    Liu, Sijun; Li, Lin

    2015-02-04

    The multiple phase transition and the scaling behavior of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic F127, PEO100-PPO65-PEO100) have been studied by micro-differential scanning calorimetry and rheology. The scaling behavior of the triblock copolymer was examined using the Winter-Chambon criterion to obtain the critical gel temperature Tgel and the scaling exponent n. n was found to decrease linearly with increasing copolymer concentration. A stable hard gel was formed, but the hard gel was transformed into a soft gel upon further heating. Increasing copolymer concentration led to the increase in the temperature of hard-soft gel transition, while the sol-gel transition temperature decreased with increasing copolymer concentration. A phase diagram has been determined, which is able to classify unimers, micelles, hard gel, and soft gel regions upon heating. In addition, the scaling relation of the plateau modulus Ge with copolymer concentration was also obtained as Ge ≈ c(3.0) for both soft gel and hard gel.

  9. Effects of Salts and Ionic Liquids on the Thermodynamics of Poly(ethylene oxide)-Containing Block Copolymers

    NASA Astrophysics Data System (ADS)

    Wanakule, Nisita; Virgili, Justin; Teran, Alexander; Balsara, Nitash

    2010-03-01

    We explore the thermodynamics of block copolymers doped with the salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the ionic liquid, imidazolium bis(trifluoromethanesulfonyl) imide ([Im][TFSI]). The block copolymers comprise of polyethylene oxide (PEO), a polymer with a higher dielectric constant, and polystyrene (PS), a polymer with a lower dielectric constant. A combination of small-angle x-ray scattering (SAXS) and birefringence was used to determine morphology and order-to-disorder transition temperatures (ODT). Leibler's theory for microphase separation was employed to determine the effective Flory-Huggins interaction parameter. These values are compared to theoretically-determined values of the effective interaction parameter which were calculated with no adjustable parameters using a theory developed by Zhen-Gang Wang.

  10. Coarse-graining poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers using the MARTINI force field.

    PubMed

    Nawaz, Selina; Carbone, Paola

    2014-02-13

    The MARTINI coarse-grain (CG) force field is extended for a class of triblock block copolymers known as Pluronics. Existing MARTINI bead types are used to model the non-bonded part of the potential while single chain properties for both homopolymers, poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), are used to develop the bonded interactions. The new set of force field parameters reproduces structural and dynamical properties of high molecular weight homo- and copolymers. The CG model is moderately transferable in solvents of different polarity and concentration; however, the PEO homopolymer model presents a reduced thermodynamic transferability especially in water probably due to the lack of hydrogen bonds with the solvent. Our simulations of a monolayer of Pluronic L44 show polymer-brush-like characteristics for the PEO segments which protrude into the aqueous phase. Other membrane properties not easily accessible using experimental techniques such as its membrane thickness are also calculated.

  11. Hyperbranched double hydrophilic block copolymer micelles of poly(ethylene oxide) and polyglycerol for pH-responsive drug delivery.

    PubMed

    Lee, Sueun; Saito, Kyohei; Lee, Hye-Ra; Lee, Min Jae; Shibasaki, Yuji; Oishi, Yoshiyuki; Kim, Byeong-Su

    2012-04-09

    We report the synthesis of a well-defined hyperbranched double hydrophilic block copolymer of poly(ethylene oxide)-hyperbranched-polyglycerol (PEO-hb-PG) to develop an efficient drug delivery system. In specific, we demonstrate the hyperbranched PEO-hb-PG can form a self-assembled micellar structure on conjugation with the hydrophobic anticancer agent doxorubicin, which is linked to the polymer by pH-sensitive hydrazone bonds, resulting in a pH-responsive controlled release of doxorubicin. Dynamic light scattering, atomic force microscopy, and transmission electron microscopy demonstrated successful formation of the spherical core-shell type micelles with an average size of about 200 nm. Moreover, the pH-responsive release of doxorubicin and in vitro cytotoxicity studies revealed the controlled stimuli-responsive drug delivery system desirable for enhanced efficiency. Benefiting from many desirable features of hyperbranched double hydrophilic block copolymers such as enhanced biocompatibility, increased water solubility, and drug loading efficiency as well as improved clearance of the polymer after drug release, we believe that double hydrophilic block copolymer will provide a versatile platform to develop excellent drug delivery systems for effective treatment of cancer.

  12. Effect of cosolvents on the self-assembly of a non-ionic polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer in the protic ionic liquid ethylammonium nitrate.

    PubMed

    Chen, Zhengfei; Greaves, Tamar L; Caruso, Rachel A; Drummond, Calum J

    2015-03-01

    The effect of water and methanol on the self-assembled structures formed by the polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer Pluronic P123 in ethylammonium nitrate was investigated by small angle X-ray scattering (SAXS). Two ternary phase diagrams were established. The addition of water had only a minor effect on the liquid crystal structures, however methanol had a significant effect, which was attributed to methanol being a good solvent for both the PEO and PPO blocks of the polymer. No lyotropic liquid crystal phases were retained when methanol reached 25 wt%. The phase behaviour did not change significantly over the temperature range from 25 to 45°C.

  13. Novel poly(ethylene oxide)-b-poly(propylene oxide) copolymer-glucose conjugate by the microwave-assisted ring opening of a sugar lactone.

    PubMed

    Glisoni, Romina J; Sosnik, Alejandro

    2014-11-01

    In this work, we investigated for the first time the conjugation of gluconolactone to a poly(ethylene oxide)-poly(propylene oxide) block copolymer by a microwave-assisted ring opening reaction. The glucosylated copolymer was obtained with high yield (90%). A conjugation extent of approximately 100% was achieved within 15 min. The modification reduced the critical micellar concentration and increased the size of the micelles. The agglutination of the modified polymeric micelles by a soluble lectin that binds glucose confirmed the recognizability of the modified nanocarrier. Finally, the solubilization of darunavir, an anti-HIV protease inhibitor, showed a sharp increase of the aqueous solubility from 91 microgram/mL to 14.2 and 18.9 mg/mL for 10% w/v pristine and glucosylated polymeric micelles, respectively.

  14. Organic-inorganic random copolymers from methacrylate-terminated poly(ethylene oxide) with 3-methacryloxypropylheptaphenyl polyhedral oligomeric silsesquioxane: synthesis via RAFT polymerization and self-assembly behavior.

    PubMed

    Wei, Kun; Li, Lei; Zheng, Sixun; Wang, Ge; Liang, Qi

    2014-01-14

    In this contribution, we report the synthesis of organic-inorganic random polymers from methacrylate-terminated poly(ethylene oxide) (MAPEO) (Mn = 950) and 3-methacryloxypropylheptaphenyl polyhedral oligomeric silsesquioxane (MAPOSS) macromers via reversible addition-fragmentation chain transfer (RAFT) polymerization with 4-cyano-4-(thiobenzoylthio) valeric acid (CTBTVA) as the chain transfer agent. The organic-inorganic random copolymers were characterized by means of (1)H NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results of GPC indicate that the polymerizations were carried out in a controlled fashion. Transmission electron microscopy (TEM) showed that the organic-inorganic random copolymers in bulk were microphase-separated and the POSS microdomains were formed via POSS-POSS interactions. In aqueous solutions the organic-inorganic random copolymers were capable of self-assembling into spherical nanoobjects as evidenced by transmission electron microscopy (TEM) and dynamic laser scattering (DLS). The self-assembly behavior of the organic-inorganic random copolymers was also found to occur in the mixtures with the precursors of epoxy. The nanostructures were further fixed via subsequent curing reaction and thus the organic-inorganic nanocomposites were obtained. The formation of nanophases in epoxy thermosets was confirmed by transmission electron microscopy (TEM) and dynamic mechanical thermal analysis (DMTA). The organic-inorganic nanocomposites displayed the enhanced surface hydrophobicity as evidenced by surface contact angle measurements.

  15. Influence of poly(ethylene oxide)-based copolymer on protein adsorption and bacterial adhesion on stainless steel: modulation by surface hydrophobicity.

    PubMed

    Yang, Yi; Rouxhet, Paul G; Chudziak, Dorota; Telegdi, Judit; Dupont-Gillain, Christine C

    2014-06-01

    The aim of the present work is to study the adhesion of Pseudomonas NCIMB 2021, a typical aerobic marine microorganism, on stainless steel (SS) substrate. More particularly, the potential effect on adhesion of adsorbed poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer is investigated. Bacterial attachment experiments were carried out using a modified parallel plate flow chamber, allowing different surface treatments to be compared in a single experiment. The amount of adhering bacteria was determined via DAPI staining and fluorescence microscopy. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface chemical composition of SS and hydrophobized SS before and after PEO-PPO-PEO adsorption. The adsorption of bovine serum albumin (BSA), a model protein, was investigated to test the resistance of PEO-PPO-PEO layers to protein adsorption. The results show that BSA adsorption and Pseudomonas 2021 adhesion are significantly reduced on hydrophobized SS conditioned with PEO-PPO-PEO. Although PEO-PPO-PEO is also found to adsorb on SS, it does not prevent BSA adsorption nor bacterial adhesion, which is attributed to different PEO-PPO-PEO adlayer structures on hydrophobic and hydrophilic surfaces. The obtained results open the way to a new strategy to reduce biofouling on metal oxide surfaces using PEO-PPO-PEO triblock copolymer.

  16. Preparation and solution behavior of a thermoresponsive diblock copolymer of poly(ethyl glycidyl ether) and poly(ethylene oxide).

    PubMed

    Ogura, Michihiro; Tokuda, Hiroyuki; Imabayashi, Shin-ichiro; Watanabe, Masayoshi

    2007-08-28

    A thermoresponsive diblock copolymer, poly(ethyl glycidyl ether)-block-poly(ethylene oxide) (PEGE-b-PEO), is synthesized by successive anionic ring-opening polymerization of ethyl glycidyl ether and ethylene oxide using 2-phenoxyethanol as a starting material, and its solution behavior is elucidated in water. In a dilute 1 wt % solution, the temperature-dependent alteration in the polymer hydrodynamic radius (RH) is measured in the temperature range between 5 and 45 degrees C by pulse-gradient spin-echo NMR and dynamic light scattering. The RH value increased with temperature in two steps, where the first step at 15 degrees C corresponds to the core-shell micelle formation and the second step at 40 degrees C corresponds to the aggregation of the core-shell micelles. The formation of the core-shell micelles is supported by the solubilization of a dye (1,6-diphenyl-1,3,5-hexatriene) in the hydrophobic core, which is recognized for a copolymer solution in the temperature range between 20 and 40 degrees C. In this temperature range, the core-shell micelles and the unimers coexist and the fraction of the former gradually increases with increasing temperature, suggesting equilibrium between the micelles and the unimers. In the concentrated regime (40 wt % solution), the solution forms a gel and the small-angle X-ray scattering measurements reveal the successive formation of hexagonal and lamellar liquid crystal phases with increasing temperature.

  17. Lactosylated poly(ethylene oxide)-poly(propylene oxide) block copolymers for potential active targeting: synthesis and physicochemical and self-aggregation characterization

    NASA Astrophysics Data System (ADS)

    Cuestas, María L.; Glisoni, Romina J.; Mathet, Verónica L.; Sosnik, Alejandro

    2013-01-01

    Aiming to develop polymeric self-assembly nanocarriers with potential applications in active drug targeting to the liver, linear and branched poly(ethylene oxide)-poly(propylene oxide) amphiphiles were conjugated to lactobionic acid (LA), a disaccharide of galactose and gluconic acid, by the conventional Steglich esterification reaction. The conjugation was confirmed by ATR/FT-IR, 1H-NMR, and 13C-NMR spectroscopy. Elemental analysis and MALDI-TOF mass spectrometry were employed to elucidate the conjugation extent and the final molecular weight, respectively. The critical micellar concentration (CMC), the size and size distribution and zeta potential of the pristine and modified polymeric micelles under different conditions of pH and temperature were characterized by dynamic light scattering (DLS). Conjugation with LA favored the micellization process, leading to a decrease of the CMC with respect to the pristine counterpart, this phenomenon being independent of the pH and the temperature. At 37 °C, micelles made of pristine copolymers showed a monomodal size distribution between 12.8 and 24.4 nm. Conversely, LA-conjugated micelles showed a bimodal size pattern that comprised a main fraction of relatively small size (11.6-22.2 nm) and a second one with remarkably larger sizes of up to 941.4 nm. The former corresponded to single micelles, while the latter would indicate a secondary aggregation phenomenon. The spherical morphology of LA-micelles was visualized by transmission electron microscopy (TEM). Finally, to assess the ability of the LA-conjugated micelles to interact with lectin-like receptors, samples were incubated with concanavalin A at 37 °C and the size and size distribution were monitored by DLS. Findings indicated that regardless of the relatively weak affinity of this vegetal lectin for galactose, micelles underwent agglutination probably through the interaction of a secondary site in the lectin with the gluconic acid unit of LA.

  18. Small angle x-ray scattering study of the interaction of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers with lipid bilayers.

    SciTech Connect

    Firestone, M. A.; Wolf, A. C.; Seifert, S.; Univ. Chicago

    2003-11-01

    The relationship between molecular architecture and the nature of interactions with lipid bilayers has been studied for a series of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers using small-angle X-ray scattering (SAXS) and thermal analysis (differential scanning calorimetry, DSC). The number of molecular repeat units in the hydrophobic poly(propylene oxide), PPO, block has been found to be a critical determinant of the nature of triblock copolymer-lipid bilayer association. For dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-based biomembrane structures, polymers possessing a PPO chain length commensurate with the acyl chain dimensions of the lipid bilayer yield highly ordered, swollen lamellar structures consistent with well-integrated (into the lipid bilayer) PPO blocks. Triblock copolymers of lesser PPO chain length yield materials with structural characteristics similar to a simple dispersion of DMPC in water. Increasing the concentration (from 4 to 12 mol %) of well-integrated triblock copolymers enhances the structural ordering of the lamellar phase, while concentrations exceeding 16 mol % result in the formation of a hexagonal phase. Examination of temperature-induced changes in the structure of these mesophases (complex fluids) reveals that if the temperature is reduced sufficiently, all compositions exclude polymer and thus exhibit the characteristic SAXS pattern for hydrated DMPC bilayers. Increasing the temperature promotes better insertion of the polymers possessing PPO chain lengths sufficient for membrane insertion. No temperature-induced structural changes are observed in compositions prepared with PEO-PPO-PEO polymers that feature PPO length insufficient to permit full incorporation into the lipid bilayer.

  19. Crystallization studies of polyethylene -poly(ethylene glycol) graft copolymers

    NASA Astrophysics Data System (ADS)

    Mark, P. R.; Hovey, G. E.; Murthy, N. S.; Breitenkamp, K.; Kade, M.; Emerick, T.

    2006-03-01

    Structure and crystallization behavior of three copolymers obtained by grafting poly (ethylene glycol) (PEG) chains to polyethylene (PE) main chain was investigated by variable temperature x-ray diffraction and thermal analysis. The results show that PEG side chains and PE main chains crystallize into separate domains. This is especially true when grafted chains are long (50 and 100 repeat units), in which the PEG domains are same as in PEG homopolymer both in structure and in melting behavior. In the copolymer with shorter chains (25 repeat units), the PEG crystals are not distinct and melting is broad. The PEG domains can be dissolved in water or ethanol without altering the mechanical integrity of the film. PE crystallites in both samples are similar to that in PE homopolymer. For instance, the thermal expansion of the basal cell plane (a- and b-axes) of the PE domains agrees well with that of PE homopolymer over the entire temperature range from ambient to melt. However, the chain-axis dimension PE-lattice in the copolymer is shorter by ˜ 0.05 å and the basal dimensions are larger by ˜ 0.05 å. The changes in these dimensions due to the changes in the length of the grafted PEG chains were investigated.

  20. Phase structures and morphologies determined by competitions among self-organization, crystallization, and vitrification in a disordered poly(ethylene oxide)-b-polystyrene diblock copolymer

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Chen, Yan; Zhang, Anqiu; Calhoun, Bret H.; Chun, Moonseok; Quirk, Roderic P.; Cheng, Stephen Z. D.; Hsiao, Benjamin S.; Yeh, Fengji; Hashimoto, Takeji

    1999-10-01

    A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer having a number-average molecular weight (M¯n) of 11 000 g/mol in the PEO blocks and an M¯n of 5200 g/mol in the PS blocks has been synthesized (with a volume fraction of the PEO blocks of 0.66 in the molten state). Differential scanning calorimetry results show that this copolymer possesses a single endotherm, which is attributed to the melting of the PEO-block crystals. Based on real-time resolved synchrotron small-angle x-ray scattering (SAXS) observations, the diblock copolymer is in a disordered state above the glass transition temperature of the PS-rich phase (TPSg), which has been determined to be 44.0 °C during cooling using dilatometer mode in thermomechanical measurements. The order-disorder transition temperature (TODT) for this diblock copolymer is thus experimentally inaccessible. Depending upon different isothermal crystallization temperatures quenched from the disordered state (Tqs), four cases can be investigated in order to understand the phase relationships among self-organization, crystallization of the PEO blocks, and vitrification of the PS-rich phase: the region where the Tq is above the TPSg, the regions where the Tq is near but slightly higher or lower than the TPSg; and the region where the Tq is below the TPSg. Utilizing simultaneous SAXS and wide angle x-ray-diffraction experiments, it can be seen that lamellar crystals of the PEO blocks in the first case grow with little morphological constraint due to initial disordered phase morphology. As the Tq approaches but is still slightly higher than the TPSg, as in the second case, the PEO-block crystals with a greater long period (L) than that of the disordered state start to grow. The initial disordered phase morphology is gradually destroyed, at least to a major extent. When the Tq is near but slightly lower than the TPSg, the crystallization takes place largely within the existing phase morphology. Only a gradual shift of

  1. Synthesis, characterization, and self-assembly of linear poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ε-caprolactone) (PEO-PPO-PCL) copolymers.

    PubMed

    Xu, Lifang; Zhang, Zhiqing; Wang, Fang; Xie, Dongdong; Yang, Shan; Wang, Tao; Feng, Lijuan; Chu, Chengchai

    2013-03-01

    Amphiphilic triblock copolymers of PEO-PPO-PCL with various block compositions have been synthesized by ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) initiated by the OH group of methoxy-poly(ethylene oxide)-poly(propylene oxide) (Me-PEO-PPO). Their structures were confirmed by Fourier transform infrared (FT-IR) measurements, and their self-assembly in aqueous solution was studied using fluorescence spectroscopy, transmission electron microscopy (TEM), UV-vis spectra, differential scanning calorimetry (DSC), and surface tension. For the copolymers studied in this paper, the critical aggregation concentrations (CAC) ranged from 5×10(3) to 2 mg/L. The critical micelle concentrations (CMC) decreased with increasing PCL block length, and the downtrend was more significant in the short PCL block length. All of the three copolymers were capable of solubilizing hydrophobic molecules (pyrene) in aqueous solution and copolymers with a longer PCL block exhibited a stronger solubilizing ability. The TEM images showed that the size and morphology of the aggregations could be tuned by varying the compositions or the concentration.

  2. Mesoscale simulation of the formation and dynamics of lipid-structured poly(ethylene oxide)-block-poly(methyl methacrylate) diblock copolymers.

    PubMed

    Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

    2015-05-21

    Twelve poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) copolymers with lipid-like structures were designed and investigated by MesoDyn simulation. Spherical and worm-like micelles as well as bicontinuous, lamellar and defected lamellar phases were obtained. A special structure, designated B2412, with two lipid structures connected by their heads, was found to undergo four stages prior to forming a spherical micelle phase. Two possible assembly mechanisms were found via thermodynamic and dynamic process analyses; namely, the fusion and fission of micelles in dynamic equilibrium during the adjustment stage. Water can be encapsulated into these micelles, which can affect their size, particularly in low concentration aqueous solutions. The assignment of weak negative charges to the hydrophilic EO blocks resulted in a clear effect on micelle size. Surprisingly, the largest effect was observed with EO blocks with -0.5 e, wherein an ordered perfect hexagonal phase was formed. The obtained results can be applied in numerous fields of study, including adsorption, catalysis, controlled release and drug delivery.

  3. Phase structures and morphologies determined by competitions among self-organization, crystallization, and vitrification in a disordered poly(ethylene oxide)-{ital b}-polystyrene diblock copolymer

    SciTech Connect

    Zhu, L.; Chen, Y.; Zhang, A.; Calhoun, B.H.; Chun, M.; Quirk, R.P.; Cheng, S.Z.; Hsiao, B.S.; Yeh, F.; Hashimoto, T.

    1999-10-01

    A poly(ethylene oxide)-{ital b}-polystyrene (PEO-{ital b}-PS) diblock copolymer having a number-average molecular weight ({bar M}{sub n}) of 11&hthinsp;000 g/mol in the PEO blocks and an {bar M}{sub n} of 5200 g/mol in the PS blocks has been synthesized (with a volume fraction of the PEO blocks of 0.66 in the molten state). Differential scanning calorimetry results show that this copolymer possesses a single endotherm, which is attributed to the melting of the PEO-block crystals. Based on real-time resolved synchrotron small-angle x-ray scattering (SAXS) observations, the diblock copolymer is in a disordered state above the glass transition temperature of the PS-rich phase (T{sub g}{sup PS}), which has been determined to be 44.0&hthinsp;{degree}C during cooling using dilatometer mode in thermomechanical measurements. The order-disorder transition temperature (T{sub ODT}) for this diblock copolymer is thus experimentally inaccessible. Depending upon different isothermal crystallization temperatures quenched from the disordered state (T{sub q}s), four cases can be investigated in order to understand the phase relationships among self-organization, crystallization of the PEO blocks, and vitrification of the PS-rich phase: the region where the T{sub q} is above the T{sub g}{sup PS}, the regions where the T{sub q} is near but slightly higher or lower than the T{sub g}{sup PS}; and the region where the T{sub q} is below the T{sub g}{sup PS}. Utilizing simultaneous SAXS and wide angle x-ray-diffraction experiments, it can be seen that lamellar crystals of the PEO blocks in the first case grow with little morphological constraint due to initial disordered phase morphology. As the T{sub q} approaches but is still slightly higher than the T{sub g}{sup PS}, as in the second case, the PEO-block crystals with a greater long period ({ital L}) than that of the disordered state start to grow. The initial disordered phase morphology is gradually destroyed, at least to a major

  4. 21 CFR 172.260 - Oxidized polyethylene.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Oxidized polyethylene. 172.260 Section 172.260... CONSUMPTION Coatings, Films and Related Substances § 172.260 Oxidized polyethylene. Oxidized polyethylene may... polyethylene is the basic resin produced by the mild air oxidation of polyethylene. The polyethylene used...

  5. 21 CFR 172.260 - Oxidized polyethylene.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Oxidized polyethylene. 172.260 Section 172.260... CONSUMPTION Coatings, Films and Related Substances § 172.260 Oxidized polyethylene. Oxidized polyethylene may... polyethylene is the basic resin produced by the mild air oxidation of polyethylene. The polyethylene used...

  6. 21 CFR 172.260 - Oxidized polyethylene.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Oxidized polyethylene. 172.260 Section 172.260... CONSUMPTION Coatings, Films and Related Substances § 172.260 Oxidized polyethylene. Oxidized polyethylene may... polyethylene is the basic resin produced by the mild air oxidation of polyethylene. The polyethylene used...

  7. Molecular arrangement of symmetric and non-symmetric triblock copolymers of poly(ethylene oxide) and poly(isobutylene) at the air/water interface.

    PubMed

    Fuchs, Christian; Hussain, Hazrat; Schwieger, Christian; Schulz, Matthias; Binder, Wolfgang H; Kressler, Jörg

    2015-01-01

    The behavior of a series of amphiphilic triblock copolymers of poly(ethylene oxide) (PEO) and poly(isobutylene) (PIB); including both symmetric (same degree of polymerization (DP) of the terminal PEO blocks) PEOm-b-PIBn-b-PEOm and non-symmetric (different DP of the terminal PEO blocks) PEOm-b-PIBn-b-PEOz, is investigated at the air/water interface by measuring surface pressure vs mean molecular area isotherms (π vs mmA), Langmuir-Blodgett (LB) technique, and infrared reflection-absorption spectroscopy (IRRAS). The block copolymer (PEO32-b-PIB160-b-PEO32) with longer PEO segments forms a stable monolayer and the isotherm reveals a pseudo-plateau starting at π∼5.7 mN/m, also observed in the IRRAS, which is assigned to the pancake-to-brush transition related to the PEO dissolution into the subphase and subsequent PEO brush dehydration. Another plateau is observed at π∼40 mN/m, which is attributed to the film collapse due to multilayer formation. The pancake-to-brush transition could not be observed for samples with smaller PEO chains. The isotherms for block copolymers, with short PEO chains, both symmetric (PEO3-b-PIBn-b-PEO3) and non-symmetric (PEO12-b-PIBn-b-PEO3), reveal another transition at π∼20-25 mN/m. This is interpreted to be due to the conformational transition from a folded state where the middle PIB block is anchored to the water surface at both ends by the terminal hydrophilic segments to an unfolded state with PIB anchored to the water surface at one end. It is assumed that this transition involves the removal of PEO3 chains from the water surface in case of non-symmetric PEO12-b-PIB85-b-PEO3 and in case of symmetric, probably one PEO3 of each PEO3-b-PIB85-b-PEO3 chain. Because of the weaker interaction of the short PEO3 chains with the water surface as compared with the relatively longer PEO12 chains, the film of PEO3-b-PIB85-b-PEO3 collapses at much lower surface pressure after the transition as compared with the PEO12-b-PIB85-b-PEO3. The

  8. Prediction of the solubility of cucurbitacin drugs in self-associating poly(ethylene oxide)-b-poly(alpha-benzyl carboxylate epsilon-caprolactone) block copolymer with different tacticities using molecular dynamics simulation.

    PubMed

    Patel, Sarthak K; Lavasanifar, Afsaneh; Choi, Phillip

    2010-01-01

    Molecular dynamics (MD) simulation was used to investigate the solubility of two hydrophobic drugs Cucurbitacin B (CuB) and Cucurbitacin I (CuI) in poly(ethylene oxide)-b-poly(alpha-benzyl carboxylate epsilon-caprolactone) (PEO-b-PBCL) block copolymers with different tacticities. In particular, di-block copolymer with three different tacticities viz. PEO-b-iPBCL, PEO-b-sPBCL, and PEO-b-aPBCL were used. The solubility was quantified by calculating the corresponding Flory-Huggins interaction parameters (chi) using random binary mixture models with 10wt% of drug. The tacticity of the di-block copolymer was found to influence significantly the solubility of two drugs in it. In particular, based on MD simulation results, only PEO-b-sPBCL exhibited solubility while the other two did not. Given the fact that the drugs were shown to be soluble in PEO-b-PBCL experimentally, it is predicted that the tacticity of the di-block copolymer synthesized in experiment is syndiotactic. This predication matches well with the dominant ring opening polymerization of cyclic lactones to syndiotactic polymers by stannous octoate as catalyst used to prepare PEO-b-PBCL block copolymers in our previous experiments. The simulation results showed that the solubility of the drugs in PEO-b-sPBCL is attributed to the favorable intra-molecular interaction of the di-block copolymer and favorable intermolecular interaction between the di-block copolymer and the drugs. Radial distribution function analysis provides useful insights into the nature and type of the intermolecular interactions.

  9. Mean-field coarse-grained model for poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer systems.

    PubMed

    García Daza, Fabián A; Colville, Alexander J; Mackie, Allan D

    2015-03-31

    The microscopic modeling of surfactant systems is of the utmost importance in understanding the mechanisms related to the micellization process because it allows for prediction and comparison with experimental data of diverse equilibrium system properties. In this work, we present a coarse-grained model for Pluronics, a trademarked type of triblock copolymer, from simulations based on a single-chain mean-field theory (SCMF). This microscopic model is used to quantify the micellization process of these nonionic surfactants at 37 °C and has been shown to be able to quantitatively reproduce experimental data of the critical micelle concentration (CMC) along with other equilibrium properties. In particular, these results correctly capture the experimental behavior with respect to the lengths of the hydrophobic and hydrophilic moieties of the surfactants for low and medium hydrophobicities. However, for the more highly hydrophobic systems with low CMCs, a deviation is found which has been previously attributed to nonequilibrium effects in the experimental data (Garcı́a Daza, F. A.; Mackie, A. D. Low Critical Micelle Concentration Discrepancy between Theory and Experiment. J. Phys. Chem. Lett. 2014, 5, 2027-2032).

  10. 21 CFR 172.260 - Oxidized polyethylene.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Oxidized polyethylene. 172.260 Section 172.260... § 172.260 Oxidized polyethylene. Oxidized polyethylene may be safely used as a component of food, subject to the following restrictions: (a) Oxidized polyethylene is the basic resin produced by the...

  11. 21 CFR 177.1620 - Polyethylene, oxidized.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Polyethylene, oxidized. 177.1620 Section 177.1620... Contact Surfaces § 177.1620 Polyethylene, oxidized. Oxidized polyethylene identified in paragraph (a) of... following prescribed conditions: (a) Oxidized polyethylene is the basic resin produced by the mild...

  12. 21 CFR 172.260 - Oxidized polyethylene.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Oxidized polyethylene. 172.260 Section 172.260 Food... Coatings, Films and Related Substances § 172.260 Oxidized polyethylene. Oxidized polyethylene may be safely used as a component of food, subject to the following restrictions: (a) Oxidized polyethylene is...

  13. Multidimensional chromatographic techniques for hydrophilic copolymers II. Analysis of poly(ethylene glycol)-poly(vinyl acetate) graft copolymers.

    PubMed

    Knecht, Daniela; Rittig, Frank; Lange, Ronald F M; Pasch, Harald

    2006-10-13

    A large variety of hydrophilic copolymers is applied in different fields of chemical industry including bio, pharma and pharmaceutical applications. For example, poly(ethylene glycol)-poly(vinyl alcohol) graft copolymers that are used as tablet coatings are responsible for the controlled release of the active compounds. These copolymers are produced by grafting of vinyl acetate onto polyethylene glycol (PEG) and subsequent hydrolysis of the poly(ethylene glycol)-poly(vinyl acetate) graft copolymers. The poly(ethylene glycol)-poly(vinyl acetate) copolymers are distributed with regard to molar mass and chemical composition. In addition, they frequently contain the homopolymers polyethylene glycol and polyvinyl acetate. The comprehensive analysis of such complex systems requires hyphenated analytical techniques, including two-dimensional liquid chromatography and combined LC and nuclear magnetic resonance spectroscopy. The development and application of these techniques are discussed in the present paper.

  14. Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by liquid chromatography under limiting conditions of desorption-3. Study of barrier efficiency according to block copolymers' chemical composition.

    PubMed

    Rollet, Marion; Pelletier, Bérengère; Berek, Dušan; Maria, Sébastien; Phan, Trang N T; Gigmes, Didier

    2016-09-02

    Liquid Chromatography under Limiting Conditions of Desorption (LC LCD) is a powerful separation tool for multicomponent polymer systems. This technique is based on a barrier effect of an appropriate solvent, which is injected in front of the sample, and which decelerates the elution of selected macromolecules. In this study, the barrier effects have been evaluated for triblock copolymers polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) according to the content of polystyrene (wt% PS) and PEO-block molar mass. PS-b-PEO-b-PS samples were prepared by Atom Transfer Radical Polymerization (ATRP). The presence of respective parent homopolymers was investigated by applying optimized LC LCD conditions. It was found that the barrier composition largely affects the efficiency of separation and it ought to be adjusted for particular composition range of block copolymers.

  15. 21 CFR 177.1620 - Polyethylene, oxidized.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Polyethylene, oxidized. 177.1620 Section 177.1620... Components of Single and Repeated Use Food Contact Surfaces § 177.1620 Polyethylene, oxidized. Oxidized polyethylene identified in paragraph (a) of this section may be safely used as a component of...

  16. 21 CFR 177.1620 - Polyethylene, oxidized.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Polyethylene, oxidized. 177.1620 Section 177.1620... Components of Single and Repeated Use Food Contact Surfaces § 177.1620 Polyethylene, oxidized. Oxidized polyethylene identified in paragraph (a) of this section may be safely used as a component of...

  17. 21 CFR 177.1620 - Polyethylene, oxidized.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyethylene, oxidized. 177.1620 Section 177.1620... Components of Single and Repeated Use Food Contact Surfaces § 177.1620 Polyethylene, oxidized. Oxidized polyethylene identified in paragraph (a) of this section may be safely used as a component of...

  18. 21 CFR 177.1620 - Polyethylene, oxidized.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Polyethylene, oxidized. 177.1620 Section 177.1620... Components of Single and Repeated Use Food Contact Surfaces § 177.1620 Polyethylene, oxidized. Oxidized polyethylene identified in paragraph (a) of this section may be safely used as a component of...

  19. Yield Stress Enhancement in Glassy-Polyethylene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Polyethylene (PE) has the highest annual production volume of all synthetic polymers worldwide, and is valuable across many applications due to its low cost, toughness, processability, and chemical resistance. However, PE is not well suited to certain applications due to its modest yield stress and Young's modulus (approximately 30 MPa and 1 GPa, respectively for linear, high-density PE). Irreversible deformation of PE results from dislocation of crystal stems and eventual crystal fragmentation under applied stress. The liquid-like amorphous fraction provides no useful mechanical support to the crystal fold surface in a PE homopolymer, so the only method to enhance the force required for crystal slip, and hence the yield stress, is crystal thickening via thermal treatment. An alternative route towards modifying the mechanical properties of PE involves copolymerization of a minority high-glass transition temperature block into a majority-PE block copolymer. In this work, we investigate a system of glassy/linear-PE block copolymers prepared via ring-opening metathesis polymerization of cyclopentene and substituted norbornene monomers followed by hydrogenation. We demonstrate that a large change in mechanical properties can be achieved with the addition of a short glassy block (e.g. a doubling of the yield stress and Young's modulus versus PE homopolymer with the addition of 25 percent glassy block). Furthermore, owing to the low interaction energy between PE and the substituted polynorbornene blocks employed, these high-yield PE block copolymers can exhibit single-phase melts for ease of processability.

  20. ESCA Study of Poly (Vinylidene Fluoride) Tetrafluoroethylene - Ethylene Copolymer and Polyethylene Exposed to Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Cormia, Robert D.

    1989-01-01

    The ESCA (electron spectroscopy for chemical analysis) spectra of films of poly(vinylidene fluoride) (PVDF), tetrafluoroethylene-ethylene copolymer (TFE/ET) and polyethylene (PE) exposed to atomic oxygen (O(P-3)), in or out of the glow of a radio-frequency O2 plasma, were compared. ESCA spectra of PE films exposed to (O(P-3)) in low Earth orbit (LEO) on the STS-8 Space Shuttle were also examined. Apart from O(P-3)-induced surface recession (etching), the various polymer films exhibited surface oxidation, which proceeded towards equilibrium saturation oxygen levels. The maximum surface oxygen uptakes for in-glow or out-of-glow exposures were in the order: PE greater than TFE/ET greater than PVDF; for PE itself, the oxygen uptakes were in the order: in glow greater than out of glow greater than LEO. Given prior ESCA data on poly(vinyl fluoride) and polytetrafluoroethylene films exposed to O(P-3), the extent of surface oxidation is seen to decrease regularly with increase in fluorine substitution in a family of ethylene-type polymers. (Keywords: ESCA; poly(vinylidene fluoride); tetrafluoroethylene ethylene copolymer; polyethylene; atomic oxygen; radio-frequency oxygen plasma; low Earth orbit)

  1. Poly(ethylene oxide) functionalization

    DOEpatents

    Pratt, Russell Clayton

    2014-04-08

    A simple procedure is provided by which the hydroxyl termini of poly(ethylene oxide) can be appended with functional groups to a useful extent by reaction and precipitation. The polymer is dissolved in warmed toluene, treated with an excess of organic base and somewhat less of an excess of a reactive acylating reagent, reacted for several hours, then precipitated in isopropanol so that the product can be isolated as a solid, and salt byproducts are washed away. This procedure enables functionalization of the polymer while not requiring laborious purification steps such as solvent-solvent extraction or dialysis to remove undesirable side products.

  2. Aggregation behavior of poly(ethylene glycol-bl-propylene sulfide) di- and triblock copolymers in aqueous solution.

    PubMed

    Cerritelli, Simona; O'Neil, Conlin P; Velluto, Diana; Fontana, Antonella; Adrian, Marc; Dubochet, Jacques; Hubbell, Jeffrey A

    2009-10-06

    Block copolymers of poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS) have recently emerged as a new macromolecular amphiphile capable of forming a wide range of morphologies when dispersed in water. To understand better the relationship between stability and morphology in terms of the relative and absolute block compositions, we have synthesized a collection of PEG-PPS block copolymers and quantified their critical aggregation concentration and observed their morphology using cryogenic transmission electron microscopy after thin film hydration with extrusion and after solvent dispersion from tetrahydrofuran, a solvent for both blocks. By understanding the relationship between aggregate character and block copolymer architecture, we have observed that whereas the relative block lengths control morphology, the stability of the aggregates upon dilution is determined by the absolute block length of the hydrophobic PPS block. We have compared results obtained with PEG-PPS to those obtained with poly(ethylene glycol)-bl-poly(propylene oxide)-bl-poly(ethylene glycol) block copolymers (Pluronics). The results reveal that the PEG-PPS aggregates are substantially more stable than Pluronic aggregates, by more than an order of magnitude. PEG-PPS can form a wide variety of stable or metastable morphologies in dilute solution within normal time and temperature ranges, whereas Pluronics can generally form only spherical micelles under the same conditions. On the basis of these results, block copolymers of PEG with poly(propylene sulfide) may present distinct advantages over those with poly(propylene glycol) for a number of applications.

  3. Poly(ethylene oxide)-b-poly(L-lactide) diblock copolymer/carbon nanotube-based nanocomposites: LiCl as supramolecular structure-directing agent.

    PubMed

    Meyer, Franck; Raquez, Jean-Marie; Verge, Pierre; Martínez de Arenaza, Inger; Coto, Borja; Van Der Voort, Pascal; Meaurio, Emilio; Dervaux, Bart; Sarasua, Jose-Ramon; Du Prez, Filip; Dubois, Philippe

    2011-11-14

    This work relies on the CNT dispersion in either solution or a polymer matrix through the formation of a three-component supramolecular system composed of PEO-b-PLLA diblock copolymer, carbon nanotubes (CNTs), and lithium chloride. According to a one-pot procedure in solution, the "self-assembly" concept has demonstrated its efficiency using suspension tests of CNTs. Characterizations of the supramolecular system by photon correlation spectroscopy, Raman spectroscopy, and molecular dynamics simulations highlight the charge transfer interaction from the CNTs toward the PEO-b-PLLA/LiCl complex. Finally, this concept was successfully extended in bulk (absence of solvent) via melt-processing techniques by dispersing these complexes in a commercial polylactide (PLA) matrix. Electrical conductivity measurements and transmission electron microscopy attested for the remarkable dispersion of CNTs, confirming the design of high-performance PLA-based materials.

  4. Mesoscopic simulation of the self-assembly of the weak polyelectrolyte poly(ethylene oxide)-block-poly(methyl methacrylate) diblock copolymers.

    PubMed

    Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

    2015-06-14

    We designed twelve types of weak polyelectrolytes (i.e., PEO-b-PMMA copolymers (BCP) in multi-arm structures, where six include EO blocks as joint points and the other six have MMA blocks as joint points). All of the BCPs with EO as the joint points form disordered phases with the exception of long-chained and four-armed BCP. The main mesophases of all of the BCPs with MMA as joint points are micelle-like and bicontinuous phases. In particular, the short-chained BCP with four-arms and EO segments outside form a new phase type (i.e., crossed lamellar phase). Using MesoDyn, we provide a comprehensive representation of the micelle and crossed lamellar phase formation mechanisms based on both thermodynamic and dynamic analyses. A shear force on a micelle-like phase could promote a hexagonal columnar phase, which is a good technique for generating an ordered arrangement of nanotube arrays. Blending homopolymers with the same constituents could promote uniformity of the micelle size and decrease the polydispersity, especially for blends with a high BCP concentration, which may provide a new approach for regulating the properties of materials.

  5. Morphology of lipid-like structured weak polyelectrolyte poly(ethylene oxide)-block-poly(methyl methacrylate) diblock copolymers induced by confinements.

    PubMed

    Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

    2015-06-14

    Combined with quantum calculations and mesoscale simulations, the self-assembly of twelve lipid-structured PEO-b-PMMA copolymers (BCPs) with six types of molecular topologies was investigated. The BCPs with MMA species as the connecting center of the other arms present ample mesoscale structures, such as micelles and lamellae or curved lamellar phases, and even macrophase separation occurs for the long-chained BCPs. The excluded volume effect of confinements helps form vesicle-like structures, which proved to be a possible method of confinement to regulate phase morphologies or segment distributions and, ultimately, the properties of materials. An analysis of the phase formation process of short-chained BCP with two hydrophilic EO segments and one hydrophobic MMA segment indicated that four stages were found in both neutral and non-neutral wall confinement, all of which present a hexagonal columnar phase. Surprisingly, when the repulsion effect of the wall to the EO segment is greater than that of the MMA segment, such BCP self assembles into a crossed columnar phase, and the intersection angle of the orientation of these two sets of cylinder arrays is 75 degrees, which can be used to produce heterogeneous nanotube arrays. For the short-chained BCP with four arms joined at MMA species and EO segments in the outer region, we found a novel method of exchanging the repulsive preference of the wall to the EO or MMA species that can control the adsorption or desorption of the lamellar phase with the interval of EO or MMA segments.

  6. Preparation and characterization of polyethylene based graft copolymers. Applications in the immobilization of enzymes

    NASA Astrophysics Data System (ADS)

    Ferreira, L. M.; Rocha, J. M. S.; Andrade, M. E.; Gil, M. H.

    1998-06-01

    In the last few years new copolymeric supports for the immobilization of biological compounds have been developed. The graft copolymer polyethylene-g.co-hydroxyethyl methacrylate, partially hydrolyzed, has shown to be a very promising support for this purpose. The more recent work in the preparation and characterization of this copolymer, as well as the immobilization of a lipase, is reported in this paper. Branches of poly(hydroxyethyl methacrylate) were grafted onto low density polyethylene by using gamma radiation. The influence of the presence and absence of air, as well as the monomer concentration on the yield of grafting were evaluated. The obtained copolymers were characterized by DSC and FTIR. The influence of the support properties on the synthesis biocatalytic activity was detected.

  7. Permselective properties for aqueous ethanol solutions through copolymer membranes from benzyl methacrylate and polyethylene glycol dimethacrylate

    SciTech Connect

    Okuno, Hiroshi; Okado, Takashi; Matsumoto, Akira; Oiwa, Masayoshi; Uragami, Tadashi )

    1992-10-01

    Copolymer membranes prepared by bulk copolymerization of polyethylene glycol dimethacrylates of three different degrees of polymerization as macromonomer and benzyl methacrylate as comonomer were used for the separation of aqueous ethanol solutions in both pervaporation and evapomeation. The copolymer membranes preferentially permeated water from an aqueous ethanol solutions in both pervaporation and evapomeation. The copolymer membranes preferentially permeated water from an aqueous ethanol solution in evapomeation. In pervaporation, ethanol was predominantly permeated from an aqueous ethanol solution through the copolymer membranes containing a long polyethylene glycol (PEG) chain above about 20 wt% PEG content in a copolymer. This result was attributed to a remarkable swelling of the copolymer membrane containing a long PEG chain by the aqueous ethanol solution in pervaporation. In evapomeation, both the separation factors and the permeation rates through these membranes are not much affected by the ethanol concentration in the feed vapor. In pervaporation, they were significantly dependent on the ethanol concentration in the feed solution. The above results are discussed from the viewpoint of the physical structure of the membrane in evapomeation and pervaporation.

  8. 1H-NMR characterization of poly(ethylene glycol) and polydimethylsiloxane copolymer

    NASA Astrophysics Data System (ADS)

    Zainuddin, Ain Athirah; Othaman, Rizafizah; Noor, Wan Syaidatul Aqma Wan Mohd; Anuar, Farah Hannan

    2016-11-01

    This paper describes the synthesis and characterization of poly(ethylene glycol) (PEG) and polydimethylsiloxane (PDMS) copolymers. The copolymers were synthesized by reacting hydroxyl group (-OH) of poly(ethylene glycol) (PEG) and polydimetylsiloxane (PDMS) with isocyanate group (R-N=C=O) of 1,6-hexamethylene diisocyanate (HMDI). The reaction was carried out at room temperature. The copolymers were synthesized in three different compositions which differ in molar ratios of PEG to PDMS. The ratios (PEG:PDMS) used were 2:6. 3:5 and 4:4. The formation of the copolymers was characterized by 1H Nuclear Magnetic Resonance (1H-NMR) for structural determination. The presence of proton signal at 4.80 ppm which belongs to the proton of urethane group indicates the formation of urethane links. The formation of urethane links showed that two homopolymers were linked together by HMDI to form longer copolymer chains. It is worth to note that the sequence of PEG and PDMS along the copolymer chain is random.

  9. Synthesis of polycarbonate-r-polyethylene glycol copolymer for templated synthesis of mesoporous TiO2 films.

    PubMed

    Patel, Rajkumar; Kim, Jinkyu; Lee, Chang Soo; Kim, Jong Hak

    2014-12-01

    We synthesized a novel polycarbonate Z-r-polyethylene glycol (PCZ-r-PEG) copolymer by solution polycondensation. Successful synthesis of PCZ-r-PEG copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), and transmission electron microscopy (TEM). PCZ-r-PEG copolymer was used as a structure-directing agent for fabrication of mesoporous thin film containing a titanium dioxide (TiO2) layer. To control the porosity of the resultant inorganic layer, the ratio of titanium(IV) isopropoxide (TTIP) to PCZ-r-PEG copolymer was varied. The structure and porosity of the resulting mesoporous films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Mesoporous TiO2 films fabricated on an F-doped tin oxide (FTO) surface were used as photoanodes for quasi-solid-state dye-sensitized solar cells (qssDSSCs). The highest efficiency achieved was 3.3% at 100 mW/cm2 for a film thickness of 750 nm, which is high considering the thickness of TiO2 film, indicating the importance of the structure-directing agent.

  10. A thermosensitive hydrogel based on biodegradable amphiphilic poly(ethylene glycol) polycaprolactone poly(ethylene glycol) block copolymers

    NASA Astrophysics Data System (ADS)

    Gong, Chang Yang; Qian, Zhi Yong; Liu, Cai Bing; Juan Huang, Mei; Gu, Ying Chun; Wen, Yan Jun; Kan, Bing; Wang, Ke; Dai, Mei; Li, Xing Yi; Gou, Ma Ling; Tu, Ming Jing; Wei, Yu Quan

    2007-06-01

    A series of low molecular weight poly(ethylene glycol)-polycaprolactone-poly(ethylene glycol) (PEG-PCL-PEG) biodegradable block copolymers were successfully synthesized using isophorone diisocyanate (IPDI) as the coupling agent, and were characterized using 1H NMR and Fourier transform infrared spectroscopy. The aqueous solutions of the PEG-PCL-PEG copolymers displayed a special thermosensitive gel-sol transition when the concentration was above the corresponding critical gel concentration. Gel-sol phase diagrams were recorded using the test-tube-inversion method; they depended on the hydrophilic/hydrophobic balance in the macromolecular structure, as well as some other factors, including the heating history, volume, and the ageing time of the copolymer aqueous solutions and dissolution temperature of the copolymers. As a result, the gel-sol transition temperature range could be altered, which might be very useful for application in injectable drug delivery systems. This work was financially supported by the Chinese Key Basic Research Program (2004CB518800 and 2004CB518807), and the Sichuan Key Project of Science and Technology (06(05SG022-021-02)).

  11. A polymer gel electrolyte composed of a poly(ethylene oxide) copolymer and the influence of its composition on the dynamics and performance of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Benedetti, João E.; Gonçalves, Agnaldo D.; Formiga, André L. B.; De Paoli, Marco-A.; Li, X.; Durrant, James R.; Nogueira, Ana F.

    A polymer gel electrolyte composed of a poly(ethylene oxide) derivative, poly(ethylene oxide-co-2-(2-methoxyethoxy) ethyl glycidyl ether), mixed with gamma-butyrolactone (GBL), LiI and I 2 is employed in dye sensitized solar cells (DSSC). The electrolyte is characterized by conductivity experiments, Raman spectroscopy and thermal analysis. The influence of the electrolyte composition on the kinetics of DSSC is also investigated by transient absorption spectroscopy (TAS). The electrolyte containing 70 wt.% of GBL and 20 wt.% of LiI presents the highest conductivity (1.9 × 10 -3 S cm -1). An efficiency of 4.4% is achieved using this composition. The increase in I SC as a function of GBL can be attributed an increase in the mobility of the iodide (polyiodide) species. The increase in the yield of the intermediate species, I 2 -, originating in the regeneration reaction, is confirmed by TAS. However, the charge recombination process is faster at this composition and a decrease in the V oc is observed. Photovoltage decay experiments confirm an acceleration in charge recombination for the DSSC assembled with the electrolyte containing more GBL. Raman investigations show that in this electrolyte the I 5 -/I 3 - ratio is higher. Theoretical calculations also indicate that the I 5 - species is a better electron acceptor.

  12. 21 CFR 172.808 - Copolymer condensates of ethylene oxide and propylene oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Copolymer condensates of ethylene oxide and... CONSUMPTION Multipurpose Additives § 172.808 Copolymer condensates of ethylene oxide and propylene oxide. Copolymer condensates of ethylene oxide and propylene oxide may be safely used in food under the...

  13. Amphiphilic copolymers reduce aggregation of unfolded lysozyme more effectively than polyethylene glycol

    NASA Astrophysics Data System (ADS)

    Chin, Jaemin; Mustafi, Devkumar; Poellmann, Michael J.; Lee, Raphael C.

    2017-02-01

    Certain amphiphilic block copolymers are known to prevent aggregation of unfolded proteins. To better understand the mechanism of this effect, the optical properties of heat-denatured and dithiothreitol reduced lysozyme were evaluated with respect to controls using UV–Vis spectroscopy, transmission electron microscopy (TEM) and circular dichroism (CD) measurements. Then, the effects of adding Polyethylene Glycol (8000 Da), the triblock surfactant Poloxamer 188 (P188), and the tetrablock copolymer Tetronic 1107 (T1107) to the lysozyme solution were compared. Overall, T1107 was found to be more effective than P188 in inhibiting aggregation, while PEG exhibited no efficacy. TEM imaging of heat-denatured and reduced lysozymes revealed spherical aggregates with on average 250–450 nm diameter. Using CD, more soluble lysozyme was recovered with T1107 than P188 with β-sheet secondary structure. The greater effectiveness of the larger T1107 in preventing aggregation of unfolded lysozyme than the smaller P188 and PEG points to steric hindrance at play; signifying the importance of size match between the hydrophobic region of denatured protein and that of amphiphilic copolymers. Thus, our results corroborate that certain multi-block copolymers are effective in preventing heat-induced aggregation of reduced lysozymes and future studies warrant more detailed focus on specific applications of these copolymers.

  14. Anisotropic charge transport in ion-conductive photoresponsive polyethylene oxide-based mesomorphic materials

    NASA Astrophysics Data System (ADS)

    Binet, Corinne; Allart, Alexandre; Judeinstein, Patrick; Roussel, Frédérick

    2017-01-01

    The mechanism of charge motion in conductive and photosensitive mesogenic block copolymers containing polyethylene oxide (PEO) segments is investigated over a wide frequency and temperature range with the broadband dielectric spectroscopy technique. It is found that the ultraviolet (UV) irradiation, the UV intensity, and the anchoring conditions of mesogenic unit in the cells produce changes in conductivity properties and in the molecular arrangement. The anisotropic nature of the conductivity is established.

  15. Anisotropic charge transport in ion-conductive photoresponsive polyethylene oxide-based mesomorphic materials.

    PubMed

    Binet, Corinne; Allart, Alexandre; Judeinstein, Patrick; Roussel, Frédérick

    2017-01-01

    The mechanism of charge motion in conductive and photosensitive mesogenic block copolymers containing polyethylene oxide (PEO) segments is investigated over a wide frequency and temperature range with the broadband dielectric spectroscopy technique. It is found that the ultraviolet (UV) irradiation, the UV intensity, and the anchoring conditions of mesogenic unit in the cells produce changes in conductivity properties and in the molecular arrangement. The anisotropic nature of the conductivity is established.

  16. Controlling Miscibility in Polyethylene-Polynorbornene Block Copolymers via Side-Group Chemistry

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Block copolymers containing a crystallizable block, such as polyethylene (PE), and an amorphous block with high glass transition temperature (Tg) are an interesting class of materials since the rigid glassy block can improve the mechanical response of the article under strain by reinforcing the crystal fold surface. However, to prepare an easily processable PE-containing block copolymer it is necessary to avoid microphase separation in the melt by selection of amorphous blocks with weak repulsive interactions against PE (low Flory interaction parameter χ or interaction energy density X) . Most such low- χ polymers are chemically similar to PE, such as copolymers of ethylene and a small amount of an α-olefin, and therefore exhibit similarly low glass transition temperatures. This work investigates a series of low- and high-Tg polymers based on substituted norbornene monomers, polymerized via ring-opening metathesis polymerization (ROMP). Hydrogenated polynorbornene derivatives possess a wide range of glass transition temperatures, and miscibility with PE can be readily tuned by the choice of substituents on the monomers (e.g. aromatic vs. aliphatic groups). Two species investigated, hydrogenated poly(cyclohexyl norbornene) and hydrogenated poly(norbornyl norbornene), have high Tg and also remain miscible with polyethylene to high molecular weight. Furthermore, we develop a set of mixing rules to qualitatively predict the solubility behavior of substituted ROMP polynorbornenes as a function of their side-groups.

  17. Ultrasound responsive block copolymer micelle of poly(ethylene glycol)-poly(propylene glycol) obtained through click reaction.

    PubMed

    Li, Fayong; Xie, Chuan; Cheng, Zhengang; Xia, Hesheng

    2016-05-01

    The well-defined amphiphilic poly(ethylene glycol)-block-poly(propylene glycol) copolymer containing 1, 2, 3-triazole moiety and multiple ester bonds (PEG-click-PPG) was prepared by click reaction strategy. The PEG-click-PPG copolymer can self-assemble into spherical micelles in aqueous solution. It is found that high intensity focused ultrasound (HIFU) can open the copolymer PEG-click-PPG micelles and trigger the release of the payload in the micelle. The multiple ester bonds introduced in the junction point of the copolymer chain through click reactions were cleaved under HIFU, and leads to the disruption of the copolymer micelle and fast release of loaded cargo. The click reaction provides a convenient way to construct ultrasound responsive copolymer micelles with weak bonds.

  18. Effect of clays on the fire-retardant properties of a polyethylenic copolymer containing intumescent formulation.

    PubMed

    Ribeiro, Simone P S; Estevão, Luciana R M; Nascimento, Regina S V

    2008-04-01

    Organophilic clay particles were added to a standard intumescent formulation and, since the role of clay expansion or intercalation is still a matter of much controversy, several clays with varying degrees of interlayer distances were evaluated. The composites were obtained by blending the nanostructured clay and the intumescent system with a polyethylenic copolymer. The flame-retardant properties of the materials were evaluated by the limiting oxygen index (LOI), the UL-94 rating and thermogravimetric analysis (TGA). The results showed that the addition of highly expanded clays to the ammonium polyphosphate and pentaerythritol formulation does not significantly increase the flame retardancy of the mixture, when measured by the LOI and UL-94. However, when clays with smaller basal distances were added to the intumescent formulation, a synergistic effect was observed. In contrast, the simple addition of clays to the copolymer, without the intumescent formulation, did not increase the fire retardance of the materials.

  19. Effect of clays on the fire-retardant properties of a polyethylenic copolymer containing intumescent formulation

    PubMed Central

    Ribeiro, Simone P S; Estevão, Luciana R M; Nascimento, Regina S V

    2008-01-01

    Organophilic clay particles were added to a standard intumescent formulation and, since the role of clay expansion or intercalation is still a matter of much controversy, several clays with varying degrees of interlayer distances were evaluated. The composites were obtained by blending the nanostructured clay and the intumescent system with a polyethylenic copolymer. The flame-retardant properties of the materials were evaluated by the limiting oxygen index (LOI), the UL-94 rating and thermogravimetric analysis (TGA). The results showed that the addition of highly expanded clays to the ammonium polyphosphate and pentaerythritol formulation does not significantly increase the flame retardancy of the mixture, when measured by the LOI and UL-94. However, when clays with smaller basal distances were added to the intumescent formulation, a synergistic effect was observed. In contrast, the simple addition of clays to the copolymer, without the intumescent formulation, did not increase the fire retardance of the materials. PMID:27877975

  20. Space charge behaviour in maleic anhydride grafted polyethylene/ethylene - vinyl - acetate copolymer laminates

    NASA Astrophysics Data System (ADS)

    Lee, Seung Hyung; Park, Jung Ki; Han, Jae Hong; Suh, Kwang S.

    1997-01-01

    Charge distributions in maleic anhydride (MAH) grafted polyethylene (g-PE)/ethylene - vinyl - acetate (EVA) copolymer laminates have been measured with materials of different composition. All laminates showed interfacial charge, the polarity and the magnitude of which are explained by interfacial polarization. It was found that the interfacial charge increased with the increase of MAH content in the g-PE, whereas it decreased with the increase of vinyl - acetate content in the EVA. This feature was attributed to the differences in electrical conductivity of the materials. Details of the experimental results are described.

  1. Synthesis and characterization of injectable, water-soluble copolymers of tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates.

    PubMed

    Anderson, Brian C; Mallapragada, Surya K

    2002-11-01

    Several homopolymers and copolymers of 2-(diethylamino)ethyl methacrylate (DEAEM) and poly(ethylene glycol) methyl ether methacrylate (PEGMEM) were synthesized using anionic polymerization initiated by potassium t-butoxide. The polymers were characterized by average molecular weight, polydispersity and monomeric unit composition. A very narrow molecular weight distribution was achieved with a well-controlled composition. The glass transition temperatures and compositions of the copolymers followed a Gordon-Taylor relationship. The water solubility and biocompatibility of the copolymers was compared to their parent homopolymers to determine if the addition of a poly(ethylene glycol) group was sufficient to solubilize the polymers in aqueous buffer solutions and to increase the biocompatibility of the polymers. These water-soluble, injectable cationic copolymers have potential applications in gene delivery as well as other biomaterial applications.

  2. 40 CFR 721.10375 - Hydroxypropyl methacrylate, reaction products with propylene oxide and ethylene oxide, copolymer...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... products with propylene oxide and ethylene oxide, copolymer with N-vinyl caprolactam (generic). 721.10375... Substances § 721.10375 Hydroxypropyl methacrylate, reaction products with propylene oxide and ethylene oxide... products with propylene oxide and ethylene oxide, copolymer with N-vinyl caprolactam (PMN P-10-200)...

  3. 40 CFR 721.10375 - Hydroxypropyl methacrylate, reaction products with propylene oxide and ethylene oxide, copolymer...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... products with propylene oxide and ethylene oxide, copolymer with N-vinyl caprolactam (generic). 721.10375... Substances § 721.10375 Hydroxypropyl methacrylate, reaction products with propylene oxide and ethylene oxide... products with propylene oxide and ethylene oxide, copolymer with N-vinyl caprolactam (PMN P-10-200)...

  4. 40 CFR 721.10375 - Hydroxypropyl methacrylate, reaction products with propylene oxide and ethylene oxide, copolymer...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... products with propylene oxide and ethylene oxide, copolymer with N-vinyl caprolactam (generic). 721.10375... Substances § 721.10375 Hydroxypropyl methacrylate, reaction products with propylene oxide and ethylene oxide... products with propylene oxide and ethylene oxide, copolymer with N-vinyl caprolactam (PMN P-10-200)...

  5. Blood compatibility evaluations of poly(ethylene glycol)-poly(lactic acid) copolymers.

    PubMed

    Li, Chenghua; Ma, Chengyan; Zhang, Yi; Liu, Zonghua; Xue, Wei

    2016-05-01

    Poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) copolymers have been widely used for various biomedical applications. However, their hemocompatibility has not been clarified, which would lag their developments and clinical applications. In this work, we studied the effect of PEG-PLA copolymers on key human blood components in terms of their structure and bio-functions, including morphology and lysis of red blood cells, fibrinogen structure and conformation, and plasma and blood coagulation. To elucidate a structure-activity relationship, we used diblock PEG-PLA copolymers with different molecular weight, PEG(5 kDa)-PLA(25 kDa) and PEG(2 kDa)-PLA(2 kDa), abbreviated as PEG5k-PLA25k and PEG2k-PLA2k, respectively. The results show that the PEG-PLA copolymers at the concentration range studied in this work neither caused morphological alteration and lysis of red blood cells nor affected the oxygen delivery function and fibrinogen conformation. PEG5k-PLA25k from 10 to 100 mg/mL and PEG2k-PLA2k from 1.5 to 5 mg/mL disturbed the local microenvironments of fibrinogen molecules. PEG5k-PLA25k at up to 0.1 mg/mL did not interfere in the coagulation process of plasma or whole blood, while PEG2k-PLA2k from 0.1 mg/mL significantly interfered in the intrinsic plasma coagulation pathway and impaired whole blood coagulation. The results provide important information for the molecular design and clinical applications of PEG-PLA copolymers.

  6. Self-Healing of Polyethylene Oxide

    NASA Astrophysics Data System (ADS)

    Chipara, Dorina Magdalena; Flores, Maritza; Puente, Nancy; Lozano, Karen

    2011-03-01

    Autonomic self-healing is expected to enhance the lifetime of polymeric materials, resins, and composites subjected to long term mechanical stresses. The self-healing process is initiated by the rupture of some polyurea-formaldehyde microcapsules filled with monomer. The self-healing polymer is actually a compound containing microcapsules filled with monomer and catalyst particles. The monomer released from these broken microcapsules is diffusing within the polymer, reacting with the catalyst and starting a polymerization reaction. This new polymer, growing within the propagating crack, stops the mechanical failure. While the process is pretty slow (timescale of the order of 10 to 100 s), there are many important technological applications that would benefit from the availability of self-healing polymers. We report about the addition of self-healing capabilities to polyethylene oxide by using polyurea formaldehyde microcapsules filled with dicyclopentadiene and first generation Grubbs catalysts. Details regarding the physical and chemical steps used to add self-healing capabilities to polyethylene oxide will be presented. Self-healing efficiency was assessed by fatigues tests.

  7. Synthesis and characterization of triblock copolymers of methoxy poly(ethylene glycol) and poly(propylene fumarate).

    PubMed

    Behravesh, Esfandiar; Shung, Albert K; Jo, Seongbong; Mikos, Antonios G

    2002-01-01

    Amphiphilic block copolymers were synthesized by transesterification of hydrophilic methoxy poly(ethylene glycol) (mPEG) and hydrophobic poly(propylene fumarate) (PPF) and characterized. Four block copolymers were synthesized with a 2:1 mPEG:PPF molar ratio and mPEGs of molecular weights 570, 800, 1960, and 5190 and PPF of molecular weight 1570 as determined by NMR. The copolymers synthesized with mPEG of molecular weights 570 and 800 had 1.9 and 1.8 mPEG blocks per copolymer, respectively, as measured by NMR, representing an ABA-type block copolymer. The number of mPEG blocks of the copolymer decreased with increasing mPEG block length to as low as 1.5 mPEG blocks for copolymer synthesized with mPEG of molecular weight 5190. At a concentration range of 5-25 wt % in phosphate-buffered saline, copolymers synthesized with mPEG molecular weights of 570 and 800 possessed lower critical solution temperatures (LCST) between 40 and 45 degrees C and between 55 and 60 degrees C, respectively. Aqueous solutions of copolymer synthesized with mPEG 570 and 800 also experienced thermoreversible gelation. The sol-gel transition temperature was dependent on the sodium chloride concentration as well as the mPEG block length. The copolymer synthesized from mPEG 570 had a transition temperature between 40 and 20 degrees C with salt concentrations between 1 and 10 wt %, while the sol-gel transition temperatures of the copolymer synthesized from mPEG molecular weight 800 were higher in the range 75-30 degrees C with salt concentrations between 1 and 15 wt %. These novel thermoreversible copolymers are the first biodegradable copolymers with unsaturated double bonds along their macromolecular chain that can undergo both physical and chemical gelation and hold great promise for drug delivery and tissue engineering applications.

  8. Interfacial Properties of Polyethylene Glycol/Vinyltriethoxysilane (PEG/VTES) Copolymers and their Application to Stain Resistance.

    PubMed

    Chao, Yin-Chun; Su, Shuenn-Kung; Lin, Ya-Wun; Hsu, Wan-Ting; Huang, Kuo-Shien

    2012-05-01

    In this study, polyethylene glycol (PEG) and vinyltriethoxysilane (VTES) were used in different proportions to produce a series of PEG-VTES copolymers. The copolymer molecular structures were confirmed by FTIR spectroscopy. In addition, their surface activities were evaluated by evaluating the surface tension, contact angle, and foaming properties. The results showed that these surfactants exhibited excellent surface activities and wetting power, as well as low foaming. Consequently, the application of a series of PEG/VTES copolymers can make cotton fabrics stain resistant.

  9. 21 CFR 172.808 - Copolymer condensates of ethylene oxide and propylene oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Copolymer condensates of ethylene oxide and... ethylene oxide and propylene oxide. Copolymer condensates of ethylene oxide and propylene oxide may be... percent aqueous solution. (2) α-Hydro-omega-hydroxy-poly (oxy-ethylene)poly(oxypropylene)-(53-59...

  10. 21 CFR 172.808 - Copolymer condensates of ethylene oxide and propylene oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Copolymer condensates of ethylene oxide and... ethylene oxide and propylene oxide. Copolymer condensates of ethylene oxide and propylene oxide may be... percent aqueous solution. (2) α-Hydro-omega-hydroxy-poly (oxy-ethylene)poly(oxypropylene)-(53-59...

  11. 21 CFR 172.808 - Copolymer condensates of ethylene oxide and propylene oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Copolymer condensates of ethylene oxide and... ethylene oxide and propylene oxide. Copolymer condensates of ethylene oxide and propylene oxide may be... percent aqueous solution. (2) α-Hydro-omega-hydroxy-poly (oxy-ethylene)poly(oxypropylene)-(53-59...

  12. 21 CFR 172.808 - Copolymer condensates of ethylene oxide and propylene oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Copolymer condensates of ethylene oxide and... ethylene oxide and propylene oxide. Copolymer condensates of ethylene oxide and propylene oxide may be... percent aqueous solution. (2) α-Hydro-omega-hydroxy-poly (oxy-ethylene)poly(oxypropylene)-(53-59...

  13. Developmental toxicity of polyethylene glycol-g-polyvinyl alcohol grafted copolymer in rats and rabbits.

    PubMed

    Heuschmid, Franziska F; Schneider, Steffen; Schuster, Paul; Lauer, Birthe; van Ravenzwaay, Bennard

    2013-07-01

    Polyethylene glycol-g-polyvinyl alcohol (PEG-PVA) grafted copolymer was evaluated in developmental toxicity studies with Wistar rats and Himalayan rabbits. Pregnant Wistar rats were gavaged with 0 (vehicle control), 100, 300, or 1000 mg PEG-PVA grafted copolymer/kg bw/day from gestation day (GD) 6-15. Pregnant Himalayan rabbits received the same treatment from GD 6 to 19. On GD 20 and 29 for rats and rabbits, respectively, the animals were euthanized and were examined grossly. For each dam, corpora lutea were counted and number and distribution of implantation sites were determined. The fetuses were removed, sexed, weighed, and evaluated for any external, soft tissue, and skeletal findings. No significant findings were found that could be attributed to administration of PEG-PVA grafted copolymer. Under the conditions of these studies, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity in both species was the highest dose tested of 1000 mg/kg bw/day.

  14. Polyethylene glycol-g-polyvinyl alcohol grafted copolymer: reproductive toxicity study in Wistar rats.

    PubMed

    Heuschmid, Franziska F; Schneider, Steffen; Schuster, Paul; Lauer, Birthe; van Ravenzwaay, Bennard

    2013-07-01

    Polyethylene glycol-g-polyvinyl alcohol (PEG-PVA) grafted copolymer was administered by gavage to groups of 25 male and 25 female young Wistar rats at doses of 0 (vehicle control), 100, 300, or 1000 mg/kg bw/day for one generation (F0). The study followed the treated F0 generation through mating, gestation, lactation, and weaning of the F1 generation. F1 animals were mated and followed to gestation day (GD) 15-17 at which time F2 implants were evaluated. There were no indications from the various clinical and gross pathological examinations that the oral administration of PEG-PVA grafted copolymer to the F0-parental rats produced any signs of general, reproductive, or developmental toxicity in the F0 or F1 animals or F2 implants. Based on the lack of any dose-related or biologically relevant effects on fertility, reproduction, development, and overall health of rats gavaged with PEG-PVA grafted copolymer and their progeny, the no-observed-adverse effect level (NOAEL) was determined to be the highest dose tested of 1000 mg/kg bw/day.

  15. Subchronic toxicity of polyethylene glycol-g-polyvinyl alcohol grafted copolymer.

    PubMed

    Heuschmid, Franziska F; Schuster, Paul; Lauer, Birthe; Buesen, Roland; Mellert, Werner; Groeters, Sibylle; van Ravenzwaay, Bennard

    2013-07-01

    The safety of polyethylene glycol-g-polyvinyl alcohol (PEG-PVA) grafted copolymer was evaluated in a 13-week oral toxicity study in rats and in a 9-month oral toxicity study in dogs. Wistar rats were administered 600, 3000, or 15,000 ppm PEG-PVA grafted copolymer in their drinking water whereas beagle dogs were fed 3000, 10,000, or 30,000 ppm PEG-PVA grafted copolymer in the diet. There were no mortalities, no adverse clinical signs, no toxicologically adverse effects on body weight or body weight gain, feed consumption, hematological, clinical chemistry or urinary parameters, or histopathology in either species. In rats, no treatment-related effects were observed in the functional observational battery (FOB) or related measurements of motor activity. Increased water consumption observed in rats at the highest dose was the only test substance-induced effect noted. The no-observed-adverse-effect level (NOAEL) was the highest concentration tested in both species: 15,000 ppm in rats (corresponding to a daily intake of 1611 mg/kg bw for males and 2191 mg/kg bw for females) and 30,000 ppm in dogs (corresponding to a mean daily intake of 783 mg/kg bw for males and 811 mg/kg bw for females).

  16. Synthesis and Characterization of a Poly(ethylene glycol)-Poly(simvastatin) Diblock Copolymer

    PubMed Central

    Asafo-Adjei, Theodora A.; Dziubla, Thomas D.; Puleo, David A.

    2014-01-01

    Biodegradable polyesters are commonly used as drug delivery vehicles, but their role is typically passive, and encapsulation approaches have limited drug payload. An alternative drug delivery method is to polymerize the active agent or its precursor into a degradable polymer. The prodrug simvastatin contains a lactone ring that lends itself to ring-opening polymerization (ROP). Consequently, simvastatin polymerization was initiated with 5 kDa monomethyl ether poly(ethylene glycol) (mPEG) and catalyzed via stannous octoate. Melt condensation reactions produced a 9.5 kDa copolymer with a polydispersity index of 1.1 at 150 °C up to a 75 kDa copolymer with an index of 6.9 at 250 °C. Kinetic analysis revealed first-order propagation rates. Infrared spectroscopy of the copolymer showed carboxylic and methyl ether stretches unique to simvastatin and mPEG, respectively. Slow degradation was demonstrated in neutral and alkaline conditions. Lastly, simvastatin, simvastatin-incorporated molecules, and mPEG were identified as the degradation products released. The present results show the potential of using ROP to polymerize lactone-containing drugs such as simvastatin. PMID:25431653

  17. Polyethylene oxide hydration in grafted layers

    NASA Astrophysics Data System (ADS)

    Dormidontova, Elena; Wang, Zilu

    Hydration of water soluble polymers is one of the key-factors defining their conformation and properties, similar to biopolymers. Polyethylene oxide (PEO) is one of the most important biomedical-applications polymers and is known for its reverse temperature solubility due to hydrogen bonding with water. As in many practical applications PEO chains are grafted to surfaces, e.g. of nanoparticles or planar surfaces, it is important to understand PEO hydration in such grafted layers. Using atomistic molecular dynamic simulations we investigate the details of molecular conformation and hydration of PEO end-grafted to gold surfaces. We analyze polymer and water density distribution as a function of distance from the surface for different grafting densities. Based on a detailed analysis of hydrogen bonding between polymer and water in grafted PEO layers, we will discuss the extent of PEO hydration and its implication for polymer conformation, mobility and layer properties. This research is supported by NSF (DMR-1410928).

  18. Location of Varying Hydrophobicity Zinc(II) Phthalocyanine-Type Photosensitizers in Methoxy Poly(ethylene oxide) and Poly(l-lactide) Block Copolymer Micelles Using (1)H NMR and XPS Techniques.

    PubMed

    Lamch, Łukasz; Tylus, Włodzimierz; Jewgiński, Michał; Latajka, Rafał; Wilk, Kazimiera A

    2016-12-15

    Hydrophobic zinc(II) phthalocyanine-type derivatives, solubilized in polymeric micelles (PMs), provide a befitting group of so-called nanophotosensitizers, suitable for a variety of photodynamic therapy (PDT) protocols. The factors that influence the success of such products in PDT are the location of the active cargo in the PMs and the nanocarrier-enhanced ability to safely interact with biological systems and fulfill their therapeutic functions. Therefore, the aim of this work was to determine the solubilization loci of three phthalocyanines of varying hydrophobicity, i.e., zinc(II) phthalocyanine (ZnPc), along with its tetrasulfonic acid (ZnPc-sulfo4) and perfluorinated (ZnPcF16) derivatives, loaded in polymeric micelles of methoxy poly(ethylene oxide)-b-poly(l-lactide) (mPEG-b-PLLA), by means of (1)H nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) combined with ion sputtering. Furthermore, the microenvironment influence upon the chemical and physical status of the solubilized cargo in PMs, expressed by photobleaching and reactive oxygen species (ROS) generation comparing to the same properties of native cargoes in solution, was also evaluated and discussed in regards to the probing location data. The studied phthalocyanine-loaded PMs exhibited good physical stability, high drug-loading efficiency, and a size of less than ca. 150 nm with low polydispersity indices. The formation of polymeric micelles and the solubilization locus were investigated by (1)H NMR and XPS. ZnPc localized within the PM core, whereas both ZnPcF16 and ZnPc-sulfo4 - in the corona of PMs. We proved that the cargo locus is crucial for the photochemical properties of the studied phthalocyanines; the increase in photostability and ability to generate ROS in micellar solution compared to free photosensitizer was most significant for the photosensitizer in the PM core. Our results indicate the role of the cargo location in the PM microenvironment and demonstrate that

  19. Mechanical properties and heat shrinkability of electron beam crosslinked polyethylene octene copolymer

    NASA Astrophysics Data System (ADS)

    Mishra, Joy K.; Chang, Young-Wook; Lee, Byung Chul; Ryu, Sung Hun

    2008-05-01

    The mechanical properties and heat shrinkability of electron beam crosslinked polyethylene-octene copolymer were studied. It was found that gel content increases with increased radiation dose. The analysis of results by the Charlesby-Pinner equation revealed that crosslinking was dominant over chain scission upon irradiation. Formation of a crosslinked structure in the electron beam irradiated sample was confirmed by the presence of a plateau of dynamic storage modulus above the melting point of the polymer. Wide-angle X-ray diffraction revealed that there was little change in crystallinity for the irradiated samples, indicating that radiation crosslinking occurs in the amorphous region of the polymer. The tensile modulus increases, whereas the elongation at break decreases with increased radiation dose. The heat shrinkability of the material increased with an increased radiation dose because the radiation-induced crosslinks serve as memory points during the shrinking process.

  20. Polyethylene glycol-polyvinyl alcohol grafted copolymer: study of the bioavailability after oral administration to rats.

    PubMed

    Heuschmid, Franziska F; Schuster, Paul; Lauer, Birthe; Fabian, Eric; Leibold, Edgar; van Ravenzwaay, Bennard

    2013-07-01

    The absorption, urinary excretion, and the biliary excretion of a single oral dose of 10 or 1000 mg/kg bw of (14)C-polyethylene glycol-polyvinyl alcohol (PEG-PVA) grafted copolymer were studied in adult male and female rats. In a balance/excretion experiment, the total excretion of ingested radioactivity was determined over a period of 168 h and residual radioactivity was detected in selected tissues and the carcass. In a biliary excretion experiment, excretion of radioactivity via the bile duct was determined over a period of 48 h after administration of the substance to cannulated rats. Most, if not all, of the radioactivity (>100%) was excreted within 48 h via the feces regardless of sex or dose. Urinary excretion was very limited: 0.45-0.50% of dose at the low dose and 0.22-0.27% of dose at the high dose. At both dose levels, residual radioactivity in the carcass and all organs and tissues after 168 h was ≤ 0.02% of dose. Biliary excretion was 0.01-0.02% of dose. Based on these findings, the bioavailability of PEG-PVA grafted copolymer was determined to be <1% demonstrating that absorption was virtually negligible following a single oral administration to male and female rats.

  1. Unexpected Temperature Behavior of Polyethylene Glycol Spacers in Copolymer Dendrimers in Chloroform

    PubMed Central

    Markelov, Denis A.; Matveev, Vladimir V.; Ingman, Petri; Nikolaeva, Marianna N.; Penkova, Anastasia V.; Lahderanta, Erkki; Boiko, Natalia I.; Chizhik, Vladimir I.

    2016-01-01

    We have studied copolymer dendrimer structure: carbosilane dendrimers with terminal phenylbenzoate mesogenic groups attached by poly(ethylene) glycol (PEG) spacers. In this system PEG spacers are additional tuning to usual copolymer structure: dendrimer with terminal mesogenic groups. The dendrimer macromolecules were investigated in a dilute chloroform solution by 1H NMR methods (spectra and relaxations). It was found that the PEG layer in G = 5 generations dendrimer is “frozen” at high temperatures (above 260 K), but it unexpectedly becomes “unfrozen” at temperatures below 250 K (i.e., melting when cooling). The transition between these two states occurs within a small temperature range (~10 K). Such a behavior is not observed for smaller dendrimer generations (G = 1 and 3). This effect is likely related to the low critical solution temperature (LCST) of PEG and is caused by dendrimer conformations, in which the PEG group concentration in the layer increases with growing G. We suppose that the unusual behavior of PEG fragments in dendrimers will be interesting for practical applications such as nanocontainers or nanoreactors. PMID:27052599

  2. Injectable and Photopolymerizable Tissue-Engineered Auricular Cartilage Using Poly(Ethylene Glycol) Dimethacrylate Copolymer Hydrogels

    PubMed Central

    Papadopoulos, Anestis; Bichara, David A.; Zhao, Xing; Ibusuki, Shinichi; Anseth, Kristi S.; Yaremchuk, Michael J.

    2011-01-01

    In this study we investigated the histological, biochemical, and integrative features of the neocartilage using swine auricular chondrocytes photoencapsulated into two poly(ethylene glycol) dimethacrylate (PEGDM) copolymer hydrogels of a different degradation profile: degradable (PEG-4,5LA-DM) and nondegradable (PEGDM) macromers in molar ratios of 60:40 and 70:30. Integration of the engineered tissue with existing native cartilage was examined using an articular cartilaginous ring model. Experimental group samples (total n = 96) were implanted subcutaneously into nude mice and harvested at 6, 12, and 18 weeks. Nonimplanted constructs (total n = 16) were used as controls for quantification of DNA, glycosaminoglycan, and hydroxyproline. Histologically, neocartilage resembled both the cellular population and composition of the extracellular matrix of the native swine auricular cartilage. DNA content demonstrated that the photoencapsulated chondrocytes were capable of survival and proliferation over time. Both glycosaminoglycan and hydroxyproline contents appeared higher in the neotissue, which was supported by less degradable PEGDM hydrogel. Integration of neocartilage with surrounding native cartilage improved with time, resulting in the development of tight integration interface. PEGDM copolymer hydrogels can support in vivo chondrogenesis by photoencapsulating auricular chondrocytes. PMID:20695772

  3. Study of cross-linking process in grafted polyethylene and ethylene based copolymer using a phase resolved photoacoustic method

    NASA Astrophysics Data System (ADS)

    Dias, D. T.; Medina, A. N.; Baesso, M. L.; Bento, A. C.; Porto, M. F.; Muniz, E. C.; Rubira, A. F.

    2003-01-01

    In this work, the phase resolved photoacoustic method has been employed to monitor water saturated vapor cross linking in both copolymer and grafted polyethylene. The overtone bands and stretching frequencies combinations of the -Si-OH, =CH2, -CH3, and -CH2-CH3 were monitored and analyzed accordingly to a 32 factorial design with nine samples. The results showed that the cross-linking processes were more efficient when the samples were prepared at 80 °C with the catalyst in the concentration range between 3% and 5% for grafted PE, while 70 °C was the best temperature to obtain copolymer.

  4. Block copolymers of the type poly(caprolactone)-b-poly(ethylene oxide) for the preparation and stabilization of nanoemulsions.

    PubMed

    Chausson, Mickael; Fluchère, Ann-Sophie; Landreau, Emmanuel; Aguni, Youssef; Chevalier, Yves; Hamaide, Thierry; Abdul-Malak, Nabil; Bonnet, Isabelle

    2008-10-01

    Block copolymers poly(caprolactone)-block-poly(ethylene oxide) are promising non-ionic macromolecular surfactants for the stabilization of emulsions because they display a stronger adsorption and provide an increased long-term stability. But such amphiphilic copolymers should also allow the fabrication of the suspensions according to the emulsification process used. An evaluation of such block copolymers was done regarding the nanoprecipitation and the miniemulsion polymerization processes that both afford aqueous suspensions of nanoparticles. Both the fabrication and the long-term stability were investigated. It was found that the emulsification by means of the nanoprecipitation process was successful when the amphiphilic block copolymer was added into the organic phase. The studies on the structure-activity relationships have shown that a minimum length of the poly(ethylene oxide) block was necessary in order to ensure both the long-term colloidal stability of the suspensions and the instantaneous stability during the preparation process. The length of the hydrophobic block was a parameter of less relevance, but a minimum length was required for the copolymers to be soluble in the organic phase. The miniemulsion polymerization process using block copolymer emulsifiers could be adapted to the incorporation of large loads of vitamin E acetate used as a hydrophobe stabilizer.

  5. Nanoparticles of Poly(Lactide-Co-Glycolide)-d-a-Tocopheryl Polyethylene Glycol 1000 Succinate Random Copolymer for Cancer Treatment

    NASA Astrophysics Data System (ADS)

    Ma, Yuandong; Zheng, Yi; Liu, Kexin; Tian, Ge; Tian, Yan; Xu, Lei; Yan, Fei; Huang, Laiqiang; Mei, Lin

    2010-07-01

    Cancer is the leading cause of death worldwide. Nanomaterials and nanotechnologies could provide potential solutions. In this research, a novel biodegradable poly(lactide-co-glycolide)-d-a-tocopheryl polyethylene glycol 1000 succinate (PLGA-TPGS) random copolymer was synthesized from lactide, glycolide and d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) by ring-opening polymerization using stannous octoate as catalyst. The obtained random copolymers were characterized by 1H NMR, FTIR, GPC and TGA. The docetaxel-loaded nanoparticles made of PLGA-TPGS copolymer were prepared by a modified solvent extraction/evaporation method. The nanoparticles were then characterized by various state-of-the-art techniques. The results revealed that the size of PLGA-TPGS nanoparticles was around 250 nm. The docetaxel-loaded PLGA-TPGS nanoparticles could achieve much faster drug release in comparison with PLGA nanoparticles. In vitro cellular uptakes of such nanoparticles were investigated by CLSM, demonstrating the fluorescence PLGA-TPGS nanoparticles could be internalized by human cervix carcinoma cells (HeLa). The results also indicated that PLGA-TPGS-based nanoparticles were biocompatible, and the docetaxel-loaded PLGA-TPGS nanoparticles had significant cytotoxicity against Hela cells. The cytotoxicity against HeLa cells for PLGA-TPGS nanoparticles was in time- and concentration-dependent manner. In conclusion, PLGA-TPGS random copolymer could be acted as a novel and promising biocompatible polymeric matrix material applicable to nanoparticle-based drug delivery system for cancer chemotherapy.

  6. Application of poly(ethylene glycol)-b-poly(epsilon-caprolactone) copolymers with different Poly(ethylene glycol) contents for the preparation of PEG-coated nanoparticles.

    PubMed

    Hou, Jingwen; Qian, Changyun; Zhang, Yanting; Guo, Shengrong

    2013-02-01

    This work used one poly(ethylene glycol)-b-poly(epsilon-caprolactone) (PEG-b-PCL) copolymer with low PEG content as matrix material and the copolymers with high PEG content as emulsifier to prepare PEG-coated nanoparticles for controlled release of paclitaxel by solvent evaporation technique. The copolymers were synthesized by ring-opening polymerization and characterized by 1H NMR and gel permeation chromatography (GPC). The effects of the composition and concentration of the copolymers used as emulsifier on the diameters and encapsulation efficiency of nanoparticles were investigated. The mean hydrodynamic diameters of the nanoparticles measured by dynamic light scattering ranged from 70 to 160 nm. The higher PEG content of emulsifier led to bigger diameter of nanoparticles and the emulsifier concentration (0.1%-1.0%) had no obvious influence on the diameters. The paclitaxel-loaded nanoparticles could achieve a sustained drug release for 7 days. When 2%-30% (w/v) of inulin was used as cryoprotectant during freeze drying process, the lyophilized nanoparticles could be well reconstituted into aqueous solution and the hydrodynamic diameter was not obviously changed.

  7. Synthesis and characterization of a Hyaluronan-polyethylene copolymer for biomedical applications.

    PubMed

    Oldinski, Rachael A; Cranson, Cody N; James, Susan P

    2010-08-01

    Hyaluronan (HA)-based biomaterials are of interest for bone and cartilage tissue engineering because HA plays an important role in orthopedic tissue development, function, and repair. The goal of this project was to develop a biomaterial that incorporated the constituents of both a hydrogel and a hydrophobic polymer for biomedical applications. A series of amphiphilic graft copolymers consisting of HA, a glycosaminoglycan, and high-density polyethylene (HDPE), that is, HA-co-HDPE, were fabricated. The chemical characteristics, physical and viscoelastic properties, and cytocompatibility of novel HA-co-HDPE materials were characterized via Fourier Transform infrared (FTIR) spectroscopy, solid state nuclear magnetic resonance (ssNMR) spectroscopy, differential scanning calorimetry (DSC), dynamic shear testing, and an in vitro human osteoblast cell study. The esterification reaction between HA and functionalized HDPE resulted in semicrystalline, insoluble powder. The dynamic shear properties of HA-co-HDPE concentrated solutions were more like natural proteoglycans than the HA control. HA-co-HDPE was successfully compression molded into disks that swelled upon hydration. Osteoblasts were viable and expressed the osteoblast phenotype after 7 days of culture on HA-co-HDPE materials. These HA-co-HDPE materials may have several biomaterial applications in saline suspension or molded form, including orthopedic tissue repair.

  8. Experiments on Charge Generation in Cross-linked Polyethylene and Ethylene-Propylene Copolymer

    NASA Astrophysics Data System (ADS)

    Sekii, Yasuo; Taya, Atsushi; Suzuki, Hirokazu; Maeno, Takashi

    To study the space charge generation in cross-linked polyethylene (XLPE) and ethylene propylene copolymer (EPR), space charge profiles in both materials are measured using PEA method. The experimental results demonstrated that a big difference was discovered in the detected charge profiles between XLPE and EPR. We discovered that the diffusion of charge is significantly faster in EPR than in XLPE. The authors confirmed that the negative hetero-charge is generated near the positive electrode in EPR when moisture are coexisting with acetophenone. The effects of antioxidants on the generation of hetero-space charges in XLPE and EPR are also studied using XLPE and EPR samples containing different kinds of phenolic and sulfur type antioxidant. The authors discovered that hetero-charge is generated in XLPE and EPR containing sulfur type, or sulfur-containing phenolic, antioxidant when acetophenone are existing in the material. The hetero-charge generation is inferred to be caused by the combined effect between acetophenone and the component containing sulfur atoms of the antioxidants.

  9. Ethylene oxide-block-butylene oxide copolymer uptake by silicone hydrogel contact lens materials

    NASA Astrophysics Data System (ADS)

    Huo, Yuchen; Ketelson, Howard; Perry, Scott S.

    2013-05-01

    Four major types of silicone hydrogel contact lens material have been investigated following treatments in aqueous solutions containing poly(ethylene oxide) and poly(butylenes oxide) block copolymer (EO-BO). The extent of lens surface modification by EO-BO and the degree of bulk uptake were studied using X-ray photoelectron spectroscopy (XPS) and ultra-performance liquid chromatography (UPLC), respectively. The experimental results suggest that different interaction models exist for the lenses, highlighting the influence of both surface and bulk composition, which greatly differs between the lenses examined. Specifically, lenses with hydrophilic surface treatments, i.e., PureVision® (balafilcon A) and O2OPTIX (lotrafilcon B), demonstrated strong evidence of preferential surface adsorption within the near-surface region. In comparison, surface adsorption on ACUVUE® Oasys® (senofilcon A) and Biofinity® (comfilcon A) was limited. As for bulk absorption, the amount of EO-BO uptake was the greatest for balafilcon A and comfilcon A, and least for lotrafilcon B. These findings confirm the presence of molecular concentration gradients within the silicone hydrogel lenses following exposure to EO-BO solutions, with the nature of such concentration gradients found to be lens-specific. Together, the results suggest opportunities for compositional modifications of lenses for improved performance via solution treatments containing surface-active agents.

  10. Injectible bodily prosthetics employing methacrylic copolymer gels

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-02-27

    The present invention provides novel block copolymers as structural supplements for injectible bodily prosthetics employed in medical or cosmetic procedures. The invention also includes the use of such block copolymers as nucleus pulposus replacement materials for the treatment of degenerative disc disorders and spinal injuries. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol) methyl ether polymer.

  11. Anomalous diffusion of poly(ethylene oxide) in agarose gels.

    PubMed

    Brenner, Tom; Matsukawa, Shingo

    2016-11-01

    We report on the effect of probe size and diffusion time of poly(ethylene) oxide in agarose gels. Time-dependence of the diffusion coefficient, reflecting anomalous diffusion, was observed for poly(ethylene) oxide chains with hydrodynamic radii exceeding about 20nm at an agarose concentration of 2%. The main conclusion is that the pore distribution includes pores that are only several nm across, in agreement with scattering reports in the literature. Interpretation of the diffusion coefficient dependence on the probe size based on a model of entangled rigid rods yielded a rod length of 72nm.

  12. Polyethylene oxide additive-entrapped polyvinyl chloride as a new blood bag material.

    PubMed

    Lee, J H; Kim, K O; Ju, Y M

    1999-01-01

    Until now, most widely used blood bag material has been a plasticized polyvinyl chloride (PVC) because it has many desirable properties as a blood bag material. One of main concerns of using plasticized PVC as a blood bag material is the toxicity of the plasticizers that are leached out of the material. We tried to solve this problem by the addition of polyethylene oxide (PEO)-containing amphiphilic block copolymers as additives in the PVC. The PEO additives may play two roles: they can act as nontoxic plasticizers to PVC, and they can also act as blood-compatible surface modifiers. In this study, PEO additive-entrapped PVC films were prepared by the addition (up to 30 wt%) of PEO-alkyl carbon block copolymers or PEO-polypropylene oxide (PPO)-PEO triblock copolymers with different PEO chain lengths in the PVC. The prepared PEO additive-containing PVC films were characterized by the measurements of water contact angle, Fourier transform IR spectroscopy in the attenuated total reflectance mode, mechanical properties (tensile strength and elongation at break), water absorption, and stability of the PEO additives entrapped in the films. It was observed that the PEO additive-entrapped PVC films were flexible and transparent. It seems that the PEO additives are surface active, resulting in the considerable change of surface characteristics without a significant change of the mechanical properties of the films compared to the control PVC without any additives or a commercial blood bag. The adhesion of platelets on the film surfaces was significantly reduced by the addition of PEO additives. It seems that 10% addition of PEO additives is enough for the suppression of platelet adhesion on the surfaces. This study demonstrated that the use of PEO-containing block copolymers as additives to the PVC can be a feasible approach to prepare a new type of blood bag.

  13. Separation of parent homopolymers from polystyrene-b-poly(ethylene oxide)-b-polystyrene triblock copolymers by means of liquid chromatography: 1. comparison of different methods.

    PubMed

    Rollet, Marion; Pelletier, Bérengère; Altounian, Anaïs; Berek, Dusan; Maria, Sébastien; Beaudoin, Emmanuel; Gigmes, Didier

    2014-03-04

    Separation of parent homopolymers, polystyrene and poly(ethylene oxide), from the triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene was investigated by means of liquid chromatography techniques. Overall suitability was evaluated and compared for size exclusion chromatography, (SEC), liquid chromatography under critical conditions of enthalpic interactions (LC CC), and liquid chromatography under limiting conditions of desorption (LC LCD). Among these techniques, LC LCD was the only one able to fully separate block copolymers from both their parent homopolymers in one single run. The efficiency of the separation was proven by (1)H NMR analysis of previously collected fractions.

  14. Time-resolved SAXS studies of morphological changes in a blend of linear polyethylene with homogeneous ethylene-1-octene copolymer

    NASA Astrophysics Data System (ADS)

    Ślusarczyk, Czesław

    2015-12-01

    Isothermal melt crystallization in the 15/85 (m/m) blend of a high density polyethylene (HDPE) and a homogeneous ethylene copolymer with 5.5 mol% 1-octene was studied by time-resolved SAXS method with synchrotron radiation over a wide-range of crystallization temperatures. The SAXS profile was analyzed by means of the correlation function which allows to elucidate the evolution of the morphological parameters of polyethylene lamellar structure (long period (LP), thicknesses of crystalline (LC) and amorphous (LA) layers) during a crystallization process. It was found that for the samples crystallized at 100 °C, 120 °C and 122 °C LC increases with time. The lamellar thickening rate strongly depends on crystallization temperature. At 40 °C thickening of the crystalline layers does not occur. The time evolution of the lamellar structure in the blend studied confirms the role of hexyl branches of homogeneous copolymer in the crystallization process of polyethylene. The branches introduce steric constraints which hinder the crystallization of HDPE, thus decreasing the size of the HDPE lamellar crystals.

  15. Biodegradable hyperbranched amphiphilic polyurethane multiblock copolymers consisting of poly(propylene glycol), poly(ethylene glycol), and polycaprolactone as in situ thermogels.

    PubMed

    Li, Zibiao; Zhang, Zhongxing; Liu, Kerh Li; Ni, Xiping; Li, Jun

    2012-12-10

    This paper reports the synthesis and characterization of new hyperbranched amphiphilic polyurethane multiblock copolymers consisting of poly(propylene glycol) (PPG), poly(ethylene glycol) (PEG), and polycaprolactone (PCL) segments as in situ thermogels. The hyperbranched poly(PPG/PEG/PCL urethane)s, termed as HBPEC copolymers, were synthesized from PPG-diol, PEG-diol, and PCL-triol by using 1,6-hexamethylene diisocyanate (HMDI) as a coupling agent. The compositions and structures of HBPEC copolymers were determined by GPC and 1H NMR spectroscopy. We carried out comparative studies of the new hyperbranched copolymers with their linear counterparts, the linear poly(PPG/PEG/PCL urethane) (LPEC) copolymer and Pluronic F127 PEG-PPG-PEG block copolymer, in terms of their self-assembly and aggregation behaviors and thermoresponsive properties. HBPEC copolymers were found to show thermoresponsive micelle formation and aggregation behaviors. Particularly, the lower critical solution temperature (LCST) of the copolymers was significantly affected by the copolymer architecture. HBPEC copolymers showed much lower LCST than LPEC, the linear counterpart. Our studies revealed that the effect of hyperbranch architecture was more prominent in the gelation of the copolymers. The aqueous solutions of HBPEC copolymers exhibited thermogelling behaviors at critical gelation concentrations (CGCs) ranging from 4.3 to 7.4 wt %. These values are much lower than those reported on other PCL-contained linear thermogelling copolymers and Pluronic F127 copolymer. In addition, the CGC of HBPEC copolymers is much lower than the control LPEC copolymer. More interestingly, at high temperatures, while LPEC and other linear thermogelling copolymers formed turbid sol, HBPEC formed a dehydrated gel. Our data suggest that these phenomena are caused by the hyperbranched structure of HBPEC copolymers, which could increase the interaction of copolymer branches and enhance the chain association through

  16. Multifunctional copolymer coating of polyethylene glycol, glycidyl methacrylate, and REDV to enhance the selectivity of endothelial cells.

    PubMed

    Wei, Yu; Zhang, Jingxun; Li, Haolie; Zhang, Li; Bi, Hong

    2015-01-01

    Multifunctional polymer coatings have potential applications in biomaterials. These coatings possess reactive functional groups for the immobilization of specific biological factors that can influence cellular behavior. These coatings also display low nonspecific protein adsorption. In this study, we prepared a multifunctional polymer coating through the deposition of random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and glycidyl methacrylate (GMA) to prevent nonspecific attachment and enable the covalence of Arg-Glu-Asp-Val (REDV) peptide with endothelial cells (ECs) selectivity. Coatings were characterized by X-ray photoelectron spectroscopy (XPS). The adhesion and proliferation of ECs and smooth muscle cells (SMCs) onto the REDV-modified surface were investigated to understand the synergistic action of antifouling PEG and EC selective REDV peptide conjugated GMA. The copolymers containing GMA and PEG groups are very useful as a multifunctional coating material with anti-fouling and ECs specific adhesion for implant materials surface modification.

  17. Poly(ethylene glycol)-polyacrylate copolymers modified to control adherent monocyte-macrophage physiology: interactions with attaching Staphylococcus epidermidis or Pseudomonas aeruginosa bacteria.

    PubMed

    Wagner, Victoria E; Bryers, James D

    2004-04-01

    The ability of various surface modifications of poly(ethylene glycol)-graft-polyacrylate (PEG-g-PA) copolymers (tethered adhesion peptides and fragments of monoclonal antibodies) to modulate monocyte-macrophage cell interactions with surface colonizing bacteria is reported. The PEG-g-PA copolymers were made to inhibit nonspecific protein and cellular adhesion. The copolymers were then covalently modified with either cell adhesion peptides (YRGDS, YEILDV, or YRGES) or fragments of antibodies to monocyte-macrophage integrin receptors (anti-VLA4, anti-beta(1), anti-beta(2), and anti-CD64), which are known to enhance macrophage adhesion and perhaps modulate their activation. Cytokine expression and phagocytosis response by surface adherent monocyte-macrophages to Staphylococcus epidermidis and Pseudomonas aeruginosa bacteria were quantified. The cytokine expression (interleukins 6 and 1 beta) of adherent macrophages in response to the modified polymers only and to bacterial challenges were quantified by dynamic ELISA assays. The adherent macrophage phagocytic response (oxidative burst) to various materials is compared to oxidative responses to both opsonized and nonopsonized S. epidermidis and P. aeruginosa bacteria. The efficiency of adherent macrophages to ingest and kill both species was determined using radiolabeled and fluorescent labeled bacterial cell ingestion studies as a function of the PEG-g-PA surface modification. Materials modified with adhesion peptides marginally enhanced (2x) macrophage attachment versus controls but, upon bacterial challenges, these materials predisposed adherent macrophages to overexpress proinflammatory cytokines and to exhibit a significant phagocytic response. Conversely, PEG-g-PA materials modified by fragments of monoclonal antibodies significantly enhanced (7x) macrophage adhesion but, upon bacterial challenge, "per cell" cytokine expression levels were reduced compared to peptide modified materials. Macrophages adhering to

  18. Polyethylene Oxidation in Total Hip Arthroplasty: Evolution and New Advances

    PubMed Central

    Gómez-Barrena, Enrique; Medel, Francisco; Puértolas, José Antonio

    2009-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) remains the gold standard acetabular bearing material for hip arthroplasty. Its successful performance has shown consistent results and survivorship in total hip replacement (THR) above 85% after 15 years, with different patients, surgeons, or designs. As THR results have been challenged by wear, oxidation, and liner fracture, relevant research on the material properties in the past decade has led to the development and clinical introduction of highly crosslinked polyethylenes (HXLPE). More stress on the bearing (more active, overweighted, younger patients), and more variability in the implantation technique in different small and large Hospitals may further compromise the clinical performance for many patients. The long-term in vivo performance of these materials remains to be proven. Clinical and retrieval studies after more than 5 years of in vivo use with HXLPE in THR are reviewed and consistently show a substantial decrease in wear rate. Moreover, a second generation of improved polyethylenes is backed by in vitro data and awaits more clinical experience to confirm the experimental improvements. Also, new antioxidant, free radical scavengers, candidates and the reinforcement of polyethylene through composites are currently under basic research. Oxidation of polyethylene is today significantly reduced by present formulations, and this forgiving, affordable, and wellknown material is still reliable to meet today’s higher requirements in total hip replacement. PMID:20111694

  19. On the mechanical and thermomechanical properties of low-density polyethylene/ethylene-α-octene copolymer blends

    NASA Astrophysics Data System (ADS)

    Pizele, D.; Kalkis, V.; Merijs Meri, R.; Ivanova, T.; Zicans, J.

    2008-03-01

    Blends of low-density polyethylene (LDPE) and ethylene-octene copolymer (EOC) were obtained. The effect of EOC content and absorbed radiation dose on the mechanical and thermomechanical properties of LDPE/EOC blends are investigated. Particular attention is given to a tensile stress-strain analysis and the "form-memory" effect of the blends. With growing LDPE content, the elastic modulus, the yield stress, and the thermorelaxation and residual stresses of the blends increase, but the ultimate elongation at break decreases, which is caused by the higher crystallinity of polyethylene. As a result of radiation-induced cross-linking, the elastic modulus, the yield stress (at a 1% strain), the ultimate yield strength, and the thermorelaxation and residual stresses increase, while the ultimate elongation at break and the melt flow-behavior index decrease, which is confirmed by the growing gel fraction in the blend.

  20. Targeted drug delivery nanosystems based on copolymer poly(lactide)-tocopheryl polyethylene glycol succinate for cancer treatment

    NASA Astrophysics Data System (ADS)

    Thu Ha, Phuong; Nguyen, Hoai Nam; Doan Do, Hai; Thong Phan, Quoc; Nguyet Tran Thi, Minh; Phuc Nguyen, Xuan; Nhung Hoang Thi, My; Huong Le, Mai; Nguyen, Linh Toan; Quang Bui, Thuc; Hieu Phan, Van

    2016-03-01

    Along with the development of nanotechnology, drug delivery nanosystems (DDNSs) have attracted a great deal of concern among scientists over the world, especially in cancer treatment. DDNSs not only improve water solubility of anticancer drugs but also increase therapeutic efficacy and minimize the side effects of treatment methods through targeting mechanisms including passive and active targeting. Passive targeting is based on the nano-size of drug delivery systems while active targeting is based on the specific bindings between targeting ligands attached on the drug delivery systems and the unique receptors on the cancer cell surface. In this article we present some of our results in the synthesis and testing of DDNSs prepared from copolymer poly(lactide)-tocopheryl polyethylene glycol succinate (PLA-TPGS), which carry anticancer drugs including curcumin, paclitaxel and doxorubicin. In order to increase the targeting effect to cancer cells, active targeting ligand folate was attached to the DDNSs. The results showed copolymer PLA-TPGS to be an excellent carrier for loading hydrophobic drugs (curcumin and paclitaxel). The fabricated DDNSs had a very small size (50-100 nm) and enhanced the cellular uptake and cytotoxicity of drugs. Most notably, folate-decorated paclitaxel-loaded copolymer PLA-TPGS nanoparticles (Fol/PTX/PLA-TPGS NPs) were tested on tumor-bearing nude mice. During the treatment time, Fol/PTX/PLA-TPGS NPs always exhibited the best tumor growth inhibition compared to free paclitaxel and paclitaxel-loaded copolymer PLA-TPGS nanoparticles. All results evidenced the promising potential of copolymer PLA-TPGS in fabricating targeted DDNSs for cancer treatment.

  1. Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

    SciTech Connect

    Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Besson, M.; Descorme, C.; Khrouz, L.

    2015-01-15

    Manganese oxides supported on mesoporous titanium oxides were synthesized via a sol–gel route using block copolymer self-assembly. The oxides were characterized by X-ray diffraction, infrared spectroscopy, thermal analyses, nitrogen adsorption/desorption, electron microscopy and electronic paramagnetic resonance. A mesoporous anatase containing amorphous manganese oxide particles could be obtained with a 0.2 Mn:Ti molar ratio. At higher manganese loading (0.5 Mn:Ti molar ratio), segregation of crystalline manganese oxide occurred. The influence of block copolymer and manganese salt on the oxide structure was discussed. The evolution of the textural and structural characteristics of the materials upon hydrothermal treatment was also investigated. - Graphical abstract: One-pot amorphous MnO{sub 2} supported on mesoporous anataseTiO{sub 2}. - Highlights: • Mesoporous manganese titanium oxides were synthesized using block copolymer. • Block copolymers form complexes with Mn{sup 2+} from MnCl{sub 2}. • With block copolymer, manganese oxide can be dispersed around the titania crystallites. • With Mn(acac){sub 2}, manganese is dispersed inside titania. • MnOOH crystallizes outside mesoporous titania during hydrothermal treatment.

  2. Fabrication and study of properties of magnetite nanoparticles in hybrid micelles of polystyrene-block-polyethylene oxide and sodium dodecyl sulfate

    SciTech Connect

    Loginova, T. P. Timofeeva, G. I.; Lependina, O. L.; Shandintsev, V. A.; Matyushin, A. A.; Khotina, I. A.; Shtykova, E. V.

    2016-01-15

    Magnetite nanoparticles have been formed for the first time in hybrid micelles of polystyrene-block-polyethylene oxide and sodium dodecyl sulfate in water by ultrasonic treatment at room temperature. An analysis by small-angle X-ray scattering and transmission electron microscopy (TEM) showed that magnetite nanoparticles in hybrid micelles of block copolymer and sodium dodecyl sulfate are polydesperse (have sizes from 0.5 to 20 nm). The specific magnetization of solid samples has been measured.

  3. Influence of different factors on the destruction of films based on polylactic acid and oxidized polyethylene

    NASA Astrophysics Data System (ADS)

    Podzorova, M. V.; Tertyshnaya, Yu. V.; Pantyukhov, P. V.; Shibryaeva, L. S.; Popov, A. A.; Nikolaeva, S.

    2016-11-01

    Influence of different environmental factors on the degradation of film samples based on polylactic acid and low density polyethylene with the addition of oxidized polyethylene was studied in this work. Different methods were used to find the relationship between degradation and ultraviolet, moisture, oxygen. It was found that the addition of oxidized polyethylene, used as a model of recycled polyethylene, promotes the degradation of blends.

  4. Oxidation-Responsive and "Clickable" Poly(ethylene glycol) via Copolymerization of 2-(Methylthio)ethyl Glycidyl Ether.

    PubMed

    Herzberger, Jana; Fischer, Karl; Leibig, Daniel; Bros, Matthias; Thiermann, Raphael; Frey, Holger

    2016-07-27

    Poly(ethylene glycol) (PEG) is a widely used biocompatible polymer. We describe a novel epoxide monomer with methyl-thioether moiety, 2-(methylthio)ethyl glycidyl ether (MTEGE), which enables the synthesis of well-defined thioether-functional poly(ethylene glycol). Random and block mPEG-b-PMTEGE copolymers (Mw/Mn = 1.05-1.17) were obtained via anionic ring opening polymerization (AROP) with molecular weights ranging from 5 600 to 12 000 g·mol(-1). The statistical copolymerization of MTEGE with ethylene oxide results in a random microstructure (rEO = 0.92 ± 0.02 and rMTEG E = 1.06 ± 0.02), which was confirmed by in situ (1)H NMR kinetic studies. The random copolymers are thermoresponsive in aqueous solution, with a wide range of tunable transition temperatures of 88 to 28 °C. In contrast, mPEG-b-PMTEGE block copolymers formed well-defined micelles (Rh ≈ 9-15 nm) in water, studied by detailed light scattering (DLS and SLS). Intriguingly, the thioether moieties of MTEGE can be selectively oxidized into sulfoxide units, leading to full disassembly of the micelles, as confirmed by detection of pure unimers (DLS and SLS). Oxidation-responsive release of encapsulated Nile Red demonstrates the potential of these micelles as redox-responsive nanocarriers. MTT assays showed only minor effects of the thioethers and their oxidized derivatives on the cellular metabolism of WEHI-164 and HEK-293T cell lines (1-1000 μg·mL(-1)). Further, sulfonium PEG polyelectrolytes can be obtained via alkylation or alkoxylation of MTEGE, providing access to a large variety of functional groups at the charged sulfur atom.

  5. Wear Analysis in THA Utilizing Oxidized Zirconium and Crosslinked Polyethylene

    PubMed Central

    Garvin, Kevin L.; Mangla, Jimmi; Murdoch, Nathan; Martell, John M.

    2008-01-01

    Oxidized zirconium, a material with a ceramic surface on a metal substrate, and highly cross-linked polyethylene are two materials developed to reduce wear. We measured in vivo femoral head penetration in patients with these advanced bearings. We hypothesized the linear wear rates would be lower than those published for cobalt-chrome and standard polyethylene. We retrospectively reviewed a select series of 56 THAs in a relatively young, active patient population utilizing oxidized zirconium femoral heads and highly cross-linked polyethylene acetabular liners. Femoral head penetration was determined using the Martell computerized edge-detection method. All patients were available for 2-year clinical and radiographic followup. True linear wear was 4 μm/year (95% confidence intervals, ± 59 μm/year). The early wear rates in this cohort of relatively young, active patients were low and we believe justify the continued study of these alternative bearing surfaces. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18946711

  6. Ordering of lamellar block copolymers on oxidized silane coatings

    DOE PAGES

    Mahadevapuram, Nikhila; Mitra, Indranil; Sridhar, Shyam; ...

    2016-01-02

    Thin films of lamellar poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers are widely investigated for surface patterning. These materials can generate dense arrays of nanoscale lines when the lamellar domains are oriented perpendicular to the substrate. To stabilize this preferred domain orientation, we tuned the substrate surface energy using oxidation of hydrophobic silane coatings. This simple approach is effective for a broad range of PS-PMMA film thicknesses when the oxidation time is optimized, which demonstrates that the substrate coating is energetically neutral with respect to PS and PMMA segments. The lamellar films are characterized by high densities of defects that exhibit amore » strong dependence on film thickness: in-plane topological defects disrupt the lateral order in ultrathin films, while lamellar domains in thick films can bend and tilt to large misorientation angles. As a result, the types and densities of these defects are similar to those observed with other classes of neutral substrate coatings, such as random copolymer brushes, which demonstrates that oxidized silanes can be used to control PS-PMMA self assembly in thin films.« less

  7. Ordering of lamellar block copolymers on oxidized silane coatings

    SciTech Connect

    Mahadevapuram, Nikhila; Mitra, Indranil; Sridhar, Shyam; Strzalka, Joseph; Stein, Gila E.

    2016-01-02

    Thin films of lamellar poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers are widely investigated for surface patterning. These materials can generate dense arrays of nanoscale lines when the lamellar domains are oriented perpendicular to the substrate. To stabilize this preferred domain orientation, we tuned the substrate surface energy using oxidation of hydrophobic silane coatings. This simple approach is effective for a broad range of PS-PMMA film thicknesses when the oxidation time is optimized, which demonstrates that the substrate coating is energetically neutral with respect to PS and PMMA segments. The lamellar films are characterized by high densities of defects that exhibit a strong dependence on film thickness: in-plane topological defects disrupt the lateral order in ultrathin films, while lamellar domains in thick films can bend and tilt to large misorientation angles. As a result, the types and densities of these defects are similar to those observed with other classes of neutral substrate coatings, such as random copolymer brushes, which demonstrates that oxidized silanes can be used to control PS-PMMA self assembly in thin films.

  8. Effect of chemical oxidation on the self-assembly of organometallic block copolymers.

    PubMed

    Eitouni, Hany B; Balsara, Nitash P

    2004-06-23

    The thermodynamic interactions in poly(styrene-block-ferrocenyldimethylsilane) and poly(isoprene-block-ferrocenyldimethylsilane) copolymers were systematically tuned by oxidation of the ferrocene moieties with silver nitrate. Small-angle X-ray scattering experiments show that oxidizing 8% of the ferrocene moieties lowers the order-disorder transition temperature of the copolymers by as much as 40 degrees C.

  9. Adsorption and association of a symmetric PEO-PPO-PEO triblock copolymer on polypropylene, polyethylene, and cellulose surfaces.

    PubMed

    Li, Yan; Liu, Hongyi; Song, Junlong; Rojas, Orlando J; Hinestroza, Juan P

    2011-07-01

    The association of a symmetric polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO(19)-PPO(29)-PEO(19)) triblock copolymer adsorbed from aqueous solutions onto polypropylene (PP), polyethylene (PE), and cellulose surfaces was probed using Atomic Force Microscopy (AFM). Significant morphological differences between the polyolefin substrates (PP and PE) and the cellulose surfaces were observed after immersion of the films in the PEO(19)-PPO(29)-PEO(19) solutions. When the samples were scanned, while immersed in solutions of the triblock copolymer, it was revealed that the structures adsorbed on the polyolefin surfaces were smoothed by the adsorbed PEO(19)-PPO(29)-PEO(19). In contrast, those structures on the hydrophilic cellulose surfaces were sharpened. These observations were related to the roughness of the substrate and the energy of interaction between the surfaces and the PEO and PPO polymer segments. The interaction energy between each of the blocks and the surface was calculated using molecular dynamics simulations. It is speculated that the associative structures amply reported in aqueous solution at concentrations above the critical micelle concentration, CMC, are not necessarily preserved upon adsorption; instead, it appears that molecular arrangements of the anchor-buoy type and hemimicelles prevail. The reported data suggests that the roughness of the surface, as well as its degree of hydrophobicity, have a large influence on the nature of the resulting adsorbed layer. The reported observations are valuable in explaining the behavior of finishing additives and lubricants commonly used in textile and fiber processing, as well as the effect of the morphology of the boundary layers on friction and wear, especially in the case of symmetric triblock copolymers, which are commonly used as antifriction, antiwear additives.

  10. Raman structural study of reactor blends of ultrahigh molecular weight polyethylene and random ethylene/1-hexene copolymers

    NASA Astrophysics Data System (ADS)

    Zavgorodnev, Yu V.; Prokhorov, K. A.; Nikolaeva, G. Yu; Sagitova, E. A.; Pashinin, P. P.; Ushakova, T. M.; Novokshonova, L. A.; Starchak, E. E.; Krasheninnikov, V. G.

    2013-02-01

    For the first time we carried out a detailed Raman study of reactor blends of high-density ultrahigh molecular weight polyethylene (UHMW PE) with random ethylene/1-hexene copolymers (CEHs). The blends were produced by consecutive two-step polymerization in the presence of rac-Me2Si(Ind)2ZrCl2/methylaluminoxane catalyst. The blends differed significantly in the CEH content as well as in the 1-hexene content in the CEH. We revealed a strong dependence of the Raman spectra of the blends on their structure. We found out that an increase in both the CEH content in the blend and the 1-hexene content in the CEH causes a reduction of the blend crystallinity and the total content of trans-conformers, while an increase in the content of gauche-conformers is observed. To investigate the effect of molecular weight on the neat polyethylene (PE) structure and Raman spectrum, we analyzed three neat PE samples with molecular weights of 34 000, 750 000, and 1 000 000. In order to better understand general regularities in the spectra, Raman spectra of solid n-alkanes C18H38 and C36H74 were also studied.

  11. Biodegradable amphiphilic block-graft copolymers based on methoxy poly(ethylene glycol)-b-(polycarbonates-g-polycarbonates) for controlled release of doxorubicin.

    PubMed

    Jiang, Tao; Li, Youmei; Lv, Yin; Cheng, Yinjia; He, Feng; Zhuo, Renxi

    2014-01-01

    In this paper, novel biodegradable amphiphilic block-graft copolymers based on methoxy poly(ethylene glycol)-b-(polycarbonates-g-polycarbonates) (mPEG-b-(PATMC-g-PATMC)) were synthesized successfully for controlled release of doxorubicin (DOX). Backbone block copolymer, methoxy poly(ethylene glycol)-b-poly(5-allyloxy-1,3-dioxan-2-one) (mPEG-b-PATMC) was synthesized in bulk catalyzed by immobilized porcine pancreas lipase (IPPL). Then, mPEG-b-PATMC-O, the allyl epoxidation product of mPEG-b-PATMC, was further grafted by PATMC itself also using IPPL as the catalyst. The copolymers were characterized by (1)N HMR and gel permeation chromatography results showed narrow molecular weight distributions. Stable micelle solutions could be prepared by dialysis method, while a monomodal and narrow size distribution could be obtained. Transmission electron microscopy (TEM) observation showed the micelles dispersed in spherical shape with nano-size before and after DOX loading. Compared with the block copolymers, the grafted structure could enhance the interaction of polymer chains with drug molecules and improve the drug-loading capacity and entrapment efficiency. Furthermore, the amphiphilic block-graft copolymers mPEG-b-(PATMC-g-PATMC) had low cytotoxicity and more sustained drug release behavior.

  12. Steric stabilization of microspheres with grafted polyethylene oxide reduces phagocytosis by rat Kupffer cells in vitro.

    PubMed

    Harper, G R; Davies, M C; Davis, S S; Tadros, T F; Taylor, D C; Irving, M P; Waters, J A

    1991-09-01

    Sterically stabilized polyethylene oxide-polystyrene copolymer microspheres, (PS-PEO) and charge stabilized polystyrene (PS) microspheres of similar size (1 micron) were prepared in order to compare their uptake by cultured rat Kupffer cells isolated by centrifugal elutriation. The uptake of the sterically stabilized particles was found to be much less than that for the charge stabilized control. The uptake of microspheres stabilized with covalently grafted PEO was lower or equivalent to that of control microspheres stabilized by the adsorption of the non-ionic PEO-polypropylene oxide (PPO-PEO) surfactant Poloxamer 238 or Methoxy-PEO. Phagocytic uptake by Kupffer cells at low and body temperature (8 degrees C and 37 degrees C) demonstrated that PS-PEO particles showed both low adherence and low metabolic uptake. The adsorption of PEO, as Poloxamer 238, to particles with covalently attached or grafted PEO resulted in a synergistic reduction in uptake that was greater than the individual effects of grafting and adsorption alone (P less than or equal to 0.001). It is suggested that this combination produces a more effective steric barrier on the particle surface with the Poloxamer adsorbing to the surface between the grafted PEO chains. The relevance to drug targeting/carrier systems is discussed.

  13. Application of Linear and Branched Poly(Ethylene Glycol)-Poly(Lactide) Block Copolymers for the Preparation of Films and Solution Electrospun Meshes.

    PubMed

    Kessler, Martina; Groll, Juergen; Tessmar, Joerg

    2016-03-01

    Poly(ethylene glycol)-poly(lactide) (PEG-PLA) block copolymers are processed to solvent cast films and solution electrospun meshes. The effect of polymer composition, architecture, and number of anchoring points for the plasticizer on swelling, degradation, and mechanical properties of these films and meshes is investigated as potential barrier device for the prevention of peritoneal adhesions. As a result, adequate properties are achieved for the massive films with a longer retention of the plasticizer PEG for star-shaped block copolymers than for the linear triblock copolymers and consequently more endurable mechanical properties during degradation. For electrospun meshes fabricated using the same polymers, similar trends are observed, but with an earlier start of fragmentation and lower tensile strengths. To overcome the poor mechanical strengths and an occurring shrinkage during incubation, which may impair the coverage of the wound, further adaptions of the meshes and the fabrication process are necessary.

  14. Electrospun Polyaniline/Polyethylene Oxide Nanofiber Field Effect Transistor

    NASA Technical Reports Server (NTRS)

    Pinto, N. J.; Johnson, A. T.; MacDiarmid, A. G.; Mueller, C. H.; Theofylaktos, N.; Robinson, D. C.; Miranda, F. A.

    2003-01-01

    We report on the observation of field effect transistor (FET) behavior in electrospun camphorsulfonic acid doped polyaniline(PANi)/polyethylene oxide(PE0) nanofibers. Saturation channel currents are observed at surprisingly low source/drain voltages. The hole mobility in the depletion regime is 1.4 x 10(exp -4) sq cm/V s while the 1-D charge density (at zero gate bias) is calculated to be approximately 1 hole per 50 two-ring repeat units of polyaniline, consistent with the rather high channel conductivity (approx. 10(exp -3) S/cm). Reducing or eliminating the PEO content in the fiber is expected to enhance device parameters. Electrospinning is thus proposed as a simple method of fabricating 1-D polymer FET's.

  15. Poly(ethylene oxide) star polymer adsorption at the silica/aqueous interface and displacement by linear poly(ethylene oxide).

    PubMed

    Saigal, Trishna; Riley, John K; Golas, Patricia Lynn; Bodvik, Rasmus; Claesson, Per M; Matyjaszewski, Krzysztof; Tilton, Robert D

    2013-03-26

    Multiarm star copolymers with approximately 460 poly(ethylene oxide) (PEO) arms that have a degree of polymerization N = 45 were synthesized via atom transfer radical polymerization (ATRP) of PEO-methacrylate macromonomers in the presence of divinyl benzene cross-linkers. These are an example of molecular or nanoparticulate brushes that are of interest as steric stabilizers or boundary lubrication agents when adsorbed from solution to a solid/aqueous interface. We use ellipsometry to measure adsorption isotherms at the silica/aqueous interface for PEO star polymers and linear PEO chains having molecular weights comparable either to the star polymer or to the individual arms. The compactness of the PEO star polymers (molecular weight 1.2 × 10(6)) yields a saturation surface excess concentration that is approximately 3.5 times greater than that of the high molecular weight (1 × 10(6)) linear PEO. Adsorption of low molecular weight (6000) linear PEO was below the detection limit. Competitive adsorption experiments were conducted with ellipsometry, complemented by independent quartz crystal microbalance with dissipation (QCM-D) measurements. Linear PEO (high molecular weight) displaced preadsorbed PEO star polymers over the course of approximately 1.5 h, to form a mixed adsorbed layer having not only a significantly lower overall polymer surface excess concentration, but also a significantly greater amount of hydrodynamically entrapped water. Challenging a preadsorbed linear PEO (high molecular weight) layer with PEO star polymers produced no measurable change in the overall polymer surface excess concentration, but changes in the QCM-D energy dissipation and resonance frequency suggested that the introduction of PEO star polymers caused a slight swelling of the layer with a correspondingly small increase in entrapped water content.

  16. Olefin-maleic-anhydride copolymer based additives: a novel approach for compatibilizing blends of waste polyethylene and crumb rubber.

    PubMed

    Tóth, Balázs; Varga, Csilla; Bartha, László

    2015-04-01

    In our work processing conditions and mechanical properties of waste polyethylene (PE)/crumb rubber (CR) blends have been improved by new types of compatibilizing additives synthesized from experimental olefin-maleic-anhydride copolymers at our laboratory. Compatibilizing additives have been introduced into the PE/CR blends in 0.2 wt% while CR concentration has been varied between 10 and 50 wt%. For comparison of the effects commercially available MA-g-PO type compatibilizing additives have also been applied. Tensile and Charpy impact tests of the compression moulded samples have been carried out. Several experimental additives have enhanced properties of the PE/CR blends either from the point of view of tensile or Charpy impact strength while commercial additives have had improving effects only on one of the abovementioned mechanical properties but not for both of them simultaneously. Since good mechanical properties could be achieved by our experimental compatibilizers good adhesion in the waste PE/CR samples have been considered and was proven by SEM graphs either.

  17. Heat shrinkability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Chaki, T. K.; Bhowmick, Anil K.

    2000-11-01

    The heat shrinkability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0-500 kGy), multifunctional sensitizer levels (ditrimethylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrinkability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrinkability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

  18. Flocculation with poly(ethylene oxide)/tyrosine-rich polypeptide complexes.

    PubMed

    Lu, Chen; Pelton, Robert

    2005-04-26

    New insights into the mechanism for the flocculation of aqueous colloids by the sequential addition of a water-borne phenolic polymer, called cofactor, followed by very high molecular poly(ethylene oxide) (PEO) are presented. It is proposed that PEO/cofactor complexes form in the aqueous phase and adsorb onto the surfaces of the target colloidal particles. Flocculation will occur if PEO/cofactor complex on one particle will bind to adsorbed complex on a second particle; i.e., if the complexes are sticky. The proposed mechanism was illustrated by flocculation experiments with precipitated calcium carbonate, very high molecular weight PEO, and a polypeptide cofactor called PEY1 which was a 1:1 random copolymer of l-glycine and l-tyrosine. Independent measurements of the PEO/PEY1 complex properties, in the absence of calcium carbonate, were used to support the mechanism. In order for PEO/PEY1 complexes to be sticky, they must simultaneously have unbound PEY1 and polymer segments. With time the complexes deactivate (i.e., lose their stickiness) by a reconfiguration process which results in elimination of either unbound PEY1 or PEO segments.

  19. Shape and Mechanical Control of Poly(ethylene oxide) Based Polymersome with Polyoxometalates via Hydrogen Bond.

    PubMed

    Jing, Benxin; Wang, Xiaofeng; Wang, Haitao; Qiu, Jie; Shi, Yi; Gao, Haifeng; Zhu, Yingxi

    2017-02-23

    Polymersomes are self-assembled vesicles of amphiphilic block copolymers and have been explored for wide applications from drug delivery to micro/nanoreactors. As polymersomes are soft and highly deformable, their shape instability due to osmolarity difference across polymer membranes and low elasticity could conversely limit their practical use. Instead of selecting particular polymer chemical reactions to enhance the mechanical properties, we have employed inorganic polyoxometalate (POM) clusters as simple physical cross-linkers to control the shape and mechanical stability of polymersomes in aqueous suspensions. Robust spherical shape with enhanced elastic and bending moduli of POM-dressed poly(ethylene oxide) (PEO) based polymersomes is achieved. We have accounted for the hydrogen bonding between POM and PEO blocks for the adsorption and stabilization of POMS on polymersomes, whose interaction strength could also be tuned by mixing solvents of hydrogen bond donors or receptors with water. The stimuli-responsive properties of POMs are introduced in POM-dressed polymersomes upon the interaction of POMs with PEO blocks in aqueous media. As POM can be used as nanomedicines, catalysts, and other functional nanomaterials, POM-dressed polymersomes with significant shape and mechanical reinforcement could broaden the applications of PEO-based polymersomes and other PEO-tethered nanocolloids.

  20. Surface characterization of poly(L-lactic acid)-methoxy poly(ethylene glycol) diblock copolymers by static and dynamic contact angle measurements, FTIR, and ATR-FTIR.

    PubMed

    Mert, O; Doganci, E; Erbil, H Y; Demir, A S

    2008-02-05

    The surface composition and surface free energy properties of two types of amphiphilic and semicrystalline diblock copolymers consisting of poly(L-lactic acid) coupled to (methoxy poly(ethylene glycol) (PLLA-MePEG) having differing block lengths of PEG were investigated by using static and dynamic contact angle measurements, transmission Fourier infrared spectroscopy (FTIR), and attenuated total reflection spectroscopy (ATR-FTIR) and compared with results obtained from PLLA and MePEG homopolymers. The contact angle results were evaluated by using the van Oss-Good method (acid-base method), and it was determined that the Lewis base surface tension coefficient (gamma-) of the copolymers increased with an increase of the PEG molar content at the copolymer surface. This result is in good agreement with the transmission FTIR and ATR-FTIR results but not proportional to them, indicating that the surfaces of the copolymers are highly mobile and that the molecular rearrangement takes place upon contact with a polar liquid drop. The dynamic contact angle measurements showed that the strong acid-base interaction between the oxygen atoms in the copolymer backbone of the relatively more hydrophilic PEG segments with the Lewis acidic groups of the polar and hydrogen-bonding water molecules enabled the surface molecules to restructure (conformational change) at the contact area, so that the PEG segments moved upward, whereas the apolar methyl pendant groups of PLLA segments buried downward.

  1. Ion-Conductive Properties of a Polymer Electrolyte Based on Ethylene Carbonate/Ethylene Oxide Random Copolymer.

    PubMed

    Morioka, Takashi; Nakano, Koji; Tominaga, Yoichi

    2017-02-21

    A random copolymer of ethylene oxide with CO2 , namely, poly(ethylene carbonate/ethylene oxide) (P(EC/EO)), has been synthesized as a novel candidate for polymer electrolytes. Electrolyte composed of P(EC/EO) and lithium bis(fluorosulfonyl)imide has an ionic conductivity of 0.48 mS cm(-1) and a Li transference number (t + ) of 0.66 at 60 °C. To study ion-conductive behavior of P(EC/EO)-based electrolytes, the Fourier transform infrared (FT-IR) technique is used to analyze the interactions between Li(+) and functional groups of the copolymer. The carbonate groups may interact preferentially with Li(+) rather than the ether groups in P(EC/EO). This study suggests that copolymerization of carbonate and flexible ether units can realize both high conductivity and t + for polymer electrolytes. High-performance P(EC/EO) electrolyte is expected to be a candidate material for use in all-solid-state batteries.

  2. Branched Rod-Coil Polyimide-Poly(Alkylene Oxide) Copolymers and Electrolyte Compositions

    NASA Technical Reports Server (NTRS)

    Meador, Maryann B. (Inventor); Tigelaar, Dean M. (Inventor)

    2014-01-01

    Crosslinked polyimide-poly(alkylene oxide) copolymers capable of holding large volumes of liquid while maintaining good dimensional stability. Copolymers are derived at ambient temperatures from amine endcapped amic-acid oligomers subsequently imidized in solution at increased temperatures, followed by reaction with trifunctional compounds in the presence of various additives. Films of these copolymers hold over four times their weight at room temperature of liquids such as ionic liquids (RTIL) and/or carbonate solvents. These rod-coil polyimide copolymers are used to prepare polymeric electrolytes by adding to the copolymers various amounts of compounds such as ionic liquids (RTIL), lithium trifluoromethane-sulfonimide (LiTFSi) or other lithium salts, and alumina.

  3. Facile and Quantitative Synthesis of a Poly(ethylene glycol)-b-Poly(l-arginine) Block Copolymer and Its Use for the Preparation of Polyion Complex Micelles with Polyanions for Biomedical Applications.

    PubMed

    Kudo, Shinpei; Nagasaki, Yukio

    2015-07-28

    Though l-arginine-containing polymers show versatile biological functions, a precisely controlled synthesis of poly(ethylene glycol)-b-poly(l-arginine) (PEG-b-PArg) block copolymers has not been reported. Here, an effective method for the synthesis of PEG-b-PArg block copolymers is developed. In order to obtain PEG-b-PArg, a two-step reaction, i.e., synthesis of PEG-b-poly(l-ornithine) is employed, followed by guanidinylation with N,N'-bis(tert-butoxycarbonyl)-1H-pyrazole-1-carboxamidine. This procedure quantitatively converts amino groups to guanidium groups at the side chains of peptide segments under mild conditions. Polyion complex (PIC) micelles are prepared by mixing the positively charged PEG-b-PArg with negatively charged homo-polyelectrolytes such as hyaluronic acid (HA) or chondroitin sulfate C (CS). PIC micelles prepared with CS show a higher stability than those prepared with HA, probably due to strong interactions between guanidium cations in PEG-b-PArg and carboxylate/sulfate in CS. Thus, PIC micelles containing PArg are a potentially effective arginine carrier for the development of in vivo therapeutic applications for various diseases related to nitric oxide, which is generated from inducible nitric oxide synthase in macrophages using l-arginine as a substrate.

  4. Thermosensitive block copolymer hydrogels based on poly(ɛ-caprolactone) and polyethylene glycol for biomedical applications: state of the art and future perspectives.

    PubMed

    Boffito, Monica; Sirianni, Paolo; Di Rienzo, Anna Maria; Chiono, Valeria

    2015-03-01

    This review focuses on the challenges associated with the design and development of injectable hydrogels of synthetic origin based on FDA approved blocks, such as polyethylene glycol (PEG) and poly(ɛ-caprolactone) (PCL). An overview of recent studies on inverse thermosensitive PEG/PCL hydrogels is provided. These systems have been proposed to overcome the limitations of previously introduced degradable thermosensitive hydrogels [e.g., PEG/poly(lactide-co-glycolic acid) hydrogels]. PEG/PCL hydrogels are advantageous due to their higher gel strength, slower degradation rate and availability in powder form. Particularly, triblock PEG/PCL copolymers have been widely investigated, with PCL-PEG-PCL (PCEC) hydrogels showing superior gel strength and slower degradation kinetics than PEG-PCL-PEG (PECE) hydrogels. Compared to triblock PEG/PCL copolymers, concentrated solutions of multiblock PEG/PCL copolymers were stable due to their slower crystallization rate. However, the resulting hydrogel gel strength was low. Inverse thermosensitive triblock PEG/PCL hydrogels have been mainly applied in tissue engineering, to decrease tissue adherence or, in combination with bioactive molecules, to promote tissue regeneration. They have also found application as in situ drug delivery carriers. On the other hand, the wide potentialities of multiblock PEG/PCL hydrogels, associated with the stability of their water-based solutions under storage, their higher degradation time compared to triblock copolymer hydrogels and the possibility to insert bioactive building blocks along the copolymer chains, have not been fully exploited yet. A critical discussion is provided to highlight advantages and limitations of currently developed themosensitive PEG/PCL hydrogels, suggesting future strategies for the realization of PEG/PCL-based copolymers with improved performance in the different application fields.

  5. Ostene, a New Alkylene Oxide Copolymer Bone Hemostatic Material, Does Not Inhibit Bone Healing

    PubMed Central

    Magyar, Clara E.; Aghaloo, Tara L.; Atti, Elisa; Tetradis, Sotirios

    2009-01-01

    OBJECTIVE In this study, we investigate the effects of a soft bone hemostatic wax comprised of water-soluble alkylene oxide copolymers (Ostene; Ceremed, Inc., Los Angeles, CA) on bone healing in a rat calvaria defect model. We compared the effects with a control (no hemostatic agent) and bone wax, an insoluble and nonresorbable material commonly used for bone hemostasis. METHODS Two bilateral 3-mm circular noncritical-sized defects were made in the calvariae of 30 rats. Alkylene oxide copolymer or bone wax was applied or no hemostatic material was used (control). After 3, 6, and 12 weeks, rats were sacrificed and the calvariae excised. Bone healing, expressed as fractional bone volume (± standard error of the mean), was measured by microcomputed tomography. RESULTS Immediate hemostasis was achieved equally with bone wax and alkylene oxide copolymer. Bone wax-filled defects remained unchanged at all time points with negligible healing observed. At 3 weeks, no evidence of alkylene oxide copolymer was observed at the application site, with fractional bone volume significantly greater than bone wax-treated defects (0.20 ± 0.03 versus 0.02 ± 0.01; P = 0.0003). At 6 and 12-weeks, alkylene oxide copolymer-treated defects continued to show significantly greater healing versus bone wax (0.18 ± 0.04 versus 0.05 ± 0.01 and 0.31 ± 0.04 versus 0.06 ± 0.02, respectively). At all time points, alkylene oxide copolymer-treated and control defects showed good healing with no significant difference. CONCLUSION Alkylene oxide copolymer is an effective hemostatic agent that does not inhibit osteogenesis or bone healing. PMID:18981846

  6. RGD-grafted poly-L-lysine-graft-(polyethylene glycol) copolymers block non-specific protein adsorption while promoting cell adhesion.

    PubMed

    VandeVondele, Stephanie; Vörös, Janos; Hubbell, Jeffrey A

    2003-06-30

    A novel class of surface-active copolymers is described, designed to protect surfaces from nonspecific protein adsorption while still inducing specific cell attachment and spreading. A graft copolymer was synthesized, containing poly-(L-lysine) (PLL) as the backbone and substrate binding and poly(ethylene glycol) (PEG) as protein adsorption-resistant pendant side chains. A fraction of the grafted PEG was pendantly functionalized by covalent conjugation to the peptide motif RGD to induce cell binding. The graft copolymer spontaneously adsorbs from dilute aqueous solution onto negatively charged surfaces. The performance of RGD-modified PLL-g-PEG copolymers was analyzed in protein adsorption and cell culture assays. These coatings efficiently blocked the adsorption of serum proteins to Nb(2)O(5) and tissue culture polystyrene while specifically supporting attachment and spreading of human dermal fibroblasts. This surface functionalization technology is expected to be valuable in both the biomaterial and biosensor fields, because different signals can easily be combined, and sterilization and application are straightforward and cost-effective.

  7. Room temperature aqueous self-assembly of poly(ethylene glycol)-poly(4-vinyl pyridine) block copolymers: From spherical to worm-like micelles.

    PubMed

    Rodrigues, Daniela P; Costa, João R C; Rocha, Nuno; Góis, Joana R; Serra, Arménio C; Coelho, Jorge F J

    2016-09-01

    The solution self-assembly and the formation, at room temperature, of a wide range of nanostructures based on monomethyl ether poly(ethylene glycol)-b-poly(4-vinyl pyridine) (mPEG-b-P4VP) block copolymer is reported. Copolymers with different compositions and molecular weights were synthesized through Atom Transfer Radical Polymerization (ATRP) method. The solution self-assembly of the block copolymers was studied by transmission electron microscopy (TEM) for different solution pHs. It was found that the formation of non-spherical nanostructures, such as rod- and worm-like micelles can be easily achieved, at room temperature, by simply varying the molecular weight of the different segments as well as the mPEG to P4VP ratio in the block copolymer structure. Because P4VP segments are known to form strong complexes with metals, the nanostructures prepared in this manuscript can find innovative applications in the biomedical field and be used as nano-templates for inorganic materials.

  8. Stability of β-carotene in polyethylene oxide electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Peinado, I.; Mason, M.; Romano, A.; Biasioli, F.; Scampicchio, M.

    2016-05-01

    β-carotene (βc) was successfully incorporated into electrospun nanofibers of poly-(ethylene oxide) (PEO) with the aim of prolonging its shelf life and thermal stability. The physical and thermal properties of the βc-PEO-nanofibers were determined by scanning electron microscopy (SEM), color analysis, and differential scanning calorimetry (DSC). The nanofibers of PEO and βc-PEO exhibited average fiber diameters of 320 ± 46 and 230 ± 21 nm, with colorimetric coordinates L* = 95.7 ± 2.4 and 89.4 ± 4.6 and b* = -0.5 ± 0.1 and 6.2 ± 3.0 respectively. Thermogravimetric analysis coupled with Proton Transfer-Mass Spectroscopy (TGA/PTR-ms) demonstrated that coated βc inside PEO nanofibers increased thermal stability when compared to standard βc in powder form. In addition, β-carotene in the membranes showed higher stability during storage when compared with β-carotene in solution with a decrease in concentration of 57 ± 4% and 70 ± 2% respectively, thus should extend the shelf life of this compound. Also, TGA coupled with PTR-MS resulted in a promising technique to online-monitoring thermal degradation.

  9. Dual-responsive polypseudorotaxanes based on block-selected inclusion between polyethylene-block-poly(ethylene glycol) diblock copolymers and 1,4-diethoxypillar[5]arene.

    PubMed

    Chen, Jianzhuang; Li, Nan; Gao, Yongping; Sun, Fugen; He, Jianping; Li, Yongsheng

    2015-10-21

    Based on the selective recognition of the polyethylene (PE) block of polyethylene-block-poly(ethylene glycol) (PE-b-PEG) by 1,4-diethoxypillar[5]arene (DEP5A), two novel thermo and competitive guest (1,4-dibromobutane or hexanedinitrile) responsive polypseudorotaxanes (PPRs) have been successfully constructed. The formation of PPRs both in solution and in the solid state was demonstrated by (1)H NMR, 2D NOESY, and WAXD analyses. TGA data illustrate that PPRs exhibit higher thermal stability than their precursor diblock copolymers. Moreover, intriguing porous disk-like aggregates are produced by electrospraying of PPRs in CHCl3 and the self-assembled structures of PPRs are totally changed by the addition of 1,4-dibromobutane or hexanedinitrile, demonstrating their competitive guest stimuli-responsiveness.

  10. FETs Based on Doped Polyaniline/Polyethylene Oxide Fibers

    NASA Technical Reports Server (NTRS)

    Theofylaktos, Noulie; Robinson, Daryl; Miranda, Felix; Pinto, Nicholas; Johnson, Alan, Jr.; MacDiarmid, Alan; Mueller, Carl

    2006-01-01

    A family of experimental highly miniaturized field-effect transistors (FETs) is based on exploitation of the electrical properties of nanofibers of polyaniline/ polyethylene oxide (PANi/PEO) doped with camphorsulfonic acid. These polymer-based FETs have the potential for becoming building blocks of relatively inexpensive, low-voltage, highspeed logic circuits that could supplant complementary metal oxide/semiconductor (CMOS) logic circuits. The development of these polymerbased FETs offers advantages over the competing development of FETs based on carbon nanotubes. Whereas it is difficult to control the molecular structures and, hence, the electrical properties of carbon nanotubes, it is easy to tailor the electrical properties of these polymerbased FETs, throughout the range from insulating through semiconducting to metallic, through choices of doping levels and chemical manipulation of polymer side chains. A further advantage of doped PANi/PEO nanofibers is that they can be made to draw very small currents and operate at low voltage levels, and thus are promising for applications in which there are requirements to use many FETs to obtain large computational capabilities while minimizing power demands. Fabrication of an experimental FET in this family begins with the preparation of a substrate as follows: A layer of silicon dioxide between 50 and 200 nm thick is deposited on a highly doped (resistivity 0.01 W.cm) silicon substrate, then gold electrodes/contact stripes are deposited on the oxide. Next, one or more fibers of camphorsulphonic acid-doped PANi/PEO having diameters of the order of 100 nm are electrospun onto the substrate so as to span the gap between the gold electrodes (see Figure 1). Figure 2 depicts measured current-versus-voltage characteristics of the device of Figure 1, showing that saturation channel currents occur at source-todrain potentials that are surprisingly low, relative to those of CMOS FETs. The hole mobility in the depletion regime in

  11. Various-sourced pectin and polyethylene oxide electrospun fibers.

    PubMed

    Rockwell, Pamela L; Kiechel, Marjorie A; Atchison, Jennifer S; Toth, Laura J; Schauer, Caroline L

    2014-07-17

    Pectin, a naturally occurring and biorenewable polysaccharide, is derived from plant cell wall tissue and used in applications ranging from food processing to biomedical engineering. Due to extraction methods and source variation, there is currently no consensus in literature as to the exact structure of pectin. Here, we have studied key material properties of electrospun pectin blends with polyethylene oxide (PEO) (1:1, v/v) in order to demonstrate the fabrication of a fibrous and less toxic material system, as well as to understand the effects of source variability on the resulting fibrous mats. The bulk pectin degree of esterification (DE) estimated using FTIR (bulk apple pomace (AP)=28%, bulk citrus peel (CP)=86% and bulk sugar beet pulp (SBP)=91%) was shown to inversely correlate with electrospun fiber crystallinity determined using XRD (PEO-AP=37%, PEO-CP=28% and PEO-SBP=23%). This in turn affected the trend observed for the mean fiber diameter (n=50) (PEO-AP=124 ± 26 nm, PEO-CP=493 ± 254 nm and PEO-SBP=581 ± 178 nm) and elastic tensile moduli (1.6 ± 0.2 MPa, 4.37 ± 0.64 MPa and 2.49 ± 1.46 MPa, respectively) of the fibrous mats. Electrospun fibers containing bulk AP had the lowest DE, highest crystallinity, smallest mean fiber diameter, and lowest tensile modulus compared to either the bulk CP or bulk SBP. Bound water in PEO-CP fiber and bulk pectin impurities in PEO-SPB were observed to influence fiber branching and mean diameter distributions, which in turn influenced the fiber tensile properties. These results indicate that pectin, when blended with PEO in water, produces submicron fibrous mats with pectin influencing the blend fiber properties. Moreover, the source of pectin is an important variable in creating electrospun blend fibrous mats with desired material properties.

  12. Block Copolymer Cross-linked Nanoassemblies Improve Particle Stability and Biocompatibility of Superparamagnetic Iron Oxide Nanoparticles

    PubMed Central

    Dan, Mo; Scott, Daniel F.; Hardy, Peter A.; Wydra, Robert J.; Hilt, J. Zach; Yokel, Robert A.; Bae, Younsoo

    2014-01-01

    Purpose To develop cross-linked nanoassemblies (CNAs) as carriers for superparamagnetic iron oxide nanoparticles (IONPs). Methods Ferric and ferrous ions were co-precipitated inside core-shell type nanoparticles prepared by cross-linking poly(ethylene glycol)-poly(aspartate) block copolymers to prepare CNAs entrapping Fe3O4 IONPs (CNA-IONPs). Particle stability and biocompatibility of CNA-IONPs were characterized in comparison to citrate-coated Fe3O4 IONPs (Citrate-IONPs). Results CNA-IONPs, approximately 30 nm in diameter, showed no precipitation in water, PBS, or a cell culture medium after 3 or 30 h, at 22, 37, and 43 °C, and 1, 2.5, and 5 mg/mL, whereas Citrate-IONPs agglomerated rapidly (> 400 nm) in all aqueous media tested. No cytotoxicity was observed in a mouse brain endothelial-derived cell line (bEnd.3) exposed to CNA-IONPs up to 10 mg/mL for 30 h. Citrate-IONPs (> 0.05 mg/mL) reduced cell viability after 3 h. CNA-IONPs retained the superparamagnetic properties of entrapped IONPs, enhancing T2-weighted magnetic resonance images (MRI) at 0.02 mg/mL, and generating heat at a mild hyperthermic level (40 ~ 42 °C) with an alternating magnetic field (AMF). Conclusion Compared to citric acid coating, CNAs with a cross-linked anionic core improved particle stability and biocompatibility of IONPs, which would be beneficial for future MRI and AMF-induced remote hyperthermia applications. PMID:23080062

  13. The effect of insulin-loaded linear poly(ethylene glycol)-brush-like poly(l-lysine) block copolymer on renal ischemia/reperfusion-induced lung injury through downregulating hypoxia-inducible factor.

    PubMed

    Tong, Fei; Tang, Xiangyuan; Li, Xin; Xia, Wenquan; Liu, Daojun

    2016-01-01

    The aim of this study was to observe the therapeutic effect of insulin-loaded linear poly(ethylene glycol)-brush-like poly(l-lysine) block copolymer poly(ethylene glycol)-b-(poly(ethylenediamine l-glutamate)-g-poly(l-lysine)) (PEG-b-(PELG-g-PLL) on renal ischemia/reperfusion-induced lung injury through downregulating hypoxia-inducible factor (HIF) as compared to free insulin. Sprague Dawley rats were pretreated with 30 U/kg insulin or insulin/PEG-b-(PELG-g-PLL) complex, and then subjected to 45 minutes of ischemia and 24 hours of reperfusion. The blood and lungs were collected, the level of serum creatinine and blood urea nitrogen were measured, and the dry/wet lung ratios, the activity of superoxide dismutase and myeloperoxidase, the content of methane dicarboxylic aldehyde and tumor necrosis factor-α, and the expression of HIF-1α and vascular endothelial growth factor (VEGF) were measured in pulmonary tissues. Both insulin and insulin/PEG-b-(PELG-g-PLL) preconditioning improved the recovery of renal function, reduced pulmonary oxidative stress injury, restrained inflammatory damage, and downregulated the expression of HIF-1α and VEGF as compared to ischemia/reperfusion group, while insulin/PEG-b-(PELG-g-PLL) significantly improved this effect.

  14. 2,1,3-Benzothiadiazole (BTD)-moiety-containing red emitter conjugated amphiphilic poly(ethylene glycol)-block-poly(ε-caprolactone) copolymers for bioimaging

    PubMed Central

    Tian, Yanqing; Wu, Wen-Chung; Chen, Ching-Yi; Strovas, Tim; Li, Yongzhong; Jin, Yuguang; Su, Fengyu; Meldrum, Deirdre R.; Jen, Alex K.-Y.

    2010-01-01

    Summary 2,1,3-Benzothiadiazole (BTD)-containing red emitter was chemically conjugated onto amphiphilic poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) copolymers to form two new fluorophore-conjugated block copolymers (P5 and P7). P5 is a cationic amino group-containing polymer, whereas, P7 is a neutral polymer. The polymers formed micelles in aqueous solution with average diameters of 45 nm (P7) and 78 nm (P5), which were characterized using dynamic light scattering (DLS) and atomic force microscopy (AFM). Cell internalization of the micelles using mouse macrophage RAW 264.7 was investigated. The micelles formed from P5 were endocytosed into the cell's cytoplasm through a non-specific endocytosis process, which was affected by temperature and calcium ions. Micelles formed from P7 could not be endocytosed. The dramatic difference of cell uptake between P5 and P7 indicated the cationic amino groups had a strong influence on the cell internalization to enhance the endocytosis pathway. 3-(4,5-Dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay was used to evaluate the cytotoxicity of the P5 micelle and no significant toxicity was observed. This study is the first report regarding the synthesis of BTD-conjugated block copolymers and the application of the biomacromolecules for bioimaging. PMID:20454543

  15. Synthesis of a new potential biodegradable disulfide containing poly(ethylene imine)-poly(ethylene glycol) copolymer cross-linked with click cluster for gene delivery.

    PubMed

    Zhao, Nan; Roesler, Susanne; Kissel, Thomas

    2011-06-15

    Poly(ethylene glycol)-grafted-polyethylenimine (PEG-PEI) are promising non-viral gene delivery systems. Herein, we aimed to synthesize a biodegradable disulfide containing PEGylated PEI to attempt to reduce its cytotoxicity and enhance the gene transfer activity. Using click chemistry, low Mw PEI (br. 2 kDa) and short chain length PEG (tetraethylene glycol, TEG) were cross-linked to a high Mw PEG-PEI copolymer (∼ 22 kDa). The chemical structure of the copolymer was characterized using (1)H NMR and GPC. The degradation behavior was investigated under in vitro conditions in the presence of 1,4-dithiothreitol (DTT). The gel retardation assay, dynamic light scattering and atomic force microscopy showed good DNA condensation ability by forming polyplexes with small particle size and positive zeta potential. In particular, MTT assay indicated that this PEG-PEI polymer is about 22-fold less toxic than PEI 25k and only 2-fold more toxic than PEI 2k in L929 cell line. After coupling of small PEG chains and cross-linking by disulfide bridges, the transfection efficiency is increased approximately 6-fold in comparison to PEI 2k and still reaches approximately 17% of PEI 25k. Hence, this click cluster cross-linked disulfide containing PEG-PEI copolymer could be an attractive cationic polymer for non-viral gene delivery.

  16. Copolymer of poly(ethylene glycol) and poly(l-lysine) grafting polyethylenimine through a reducible disulfide linkage for siRNA delivery

    NASA Astrophysics Data System (ADS)

    Li, Jingguo; Cheng, Du; Yin, Tinghui; Chen, Weicai; Lin, Yujie; Chen, Jifeng; Li, Ruitang; Shuai, Xintao

    2014-01-01

    siRNA therapy research has primarily focused on the synthesis and development of effective siRNA delivery vectors with easy biodegradability and low toxicity. In the present study, we synthesized a ternary copolymer mPEG-b-PLL-g-(ss-lPEI), denoted as PLI, by introducing disulfide bond linkages to graft low molecular weight linear polyethylenimine (lPEI) to the block copolymer of poly(l-lysine) (PLL) and poly(ethylene glycol) (PEG) for siRNA delivery. The PLL block and disulfide linkage rendered the carrier biodegradability, while lPEI grafting brought about the proton buffering capacity for lysosomal siRNA release and low cationic toxicity. Conjugation of a single chain monoclonal antibody (Herceptin) to the carrier as a targeting ligand for the Her2/neu receptor significantly increased the transfection activity of the copolymer/siRNA nanocomplex (i.e. the polyplex) in Skov-3, a human ovarian cancer cell line. Determination of gene expression at both the mRNA and protein levels demonstrated that Her2-targeted delivery of siRNA (XIAP siRNA) effectively downregulated the targeted XIAP (X-linked inhibitor of apoptosis protein) gene, resulting in enhanced cancer cell apoptosis and improved therapeutic efficacy in vitro and in vivo. The distinct features of low cytotoxicity, easy degradability, and high siRNA transfection efficiency make the copolymer a promising candidate for siRNA therapy in tumors.siRNA therapy research has primarily focused on the synthesis and development of effective siRNA delivery vectors with easy biodegradability and low toxicity. In the present study, we synthesized a ternary copolymer mPEG-b-PLL-g-(ss-lPEI), denoted as PLI, by introducing disulfide bond linkages to graft low molecular weight linear polyethylenimine (lPEI) to the block copolymer of poly(l-lysine) (PLL) and poly(ethylene glycol) (PEG) for siRNA delivery. The PLL block and disulfide linkage rendered the carrier biodegradability, while lPEI grafting brought about the proton

  17. Synthesis and Characterization of Silicate Ester Prodrugs and Poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) Block Copolymers for Formulation into Prodrug-Loaded Nanoparticles

    NASA Astrophysics Data System (ADS)

    Wohl, Adam Richard

    Fine control of the physical and chemical properties of customized materials is a field that is rapidly advancing. This is especially critical in pursuits to develop and optimize novel nanoparticle drug delivery. Specifically, I aim to apply chemistry concepts to test the hypothesis "Silicate ester prodrugs of paclitaxel, customized to have the proper hydrophobicity and hydrolytic lability, can be formulated with well-defined, biocompatible, amphiphilic block copolymers into nanoparticles that are effective drugs." Chapter 1 briefly describes the context and motivation of the scientific pursuits described in this thesis. In Chapter 2, a family of model silicate esters is synthesized, the hydrolysis rate of each compound is benchmarked, and trends are established based upon the steric bulk and leaving group ability of the silicate substituents. These trends are then applied to the synthesis of labile silicate ester prodrugs in Chapter 3. The bulk of this chapter focuses on the synthesis, hydrolysis, and cytotoxicity of prodrugs based on paclitaxel, a widely used chemotherapeutic agent. In Chapter 4, a new methodology for the synthesis of narrowly dispersed, "random" poly(lactic-co-glycolic acid) polymers by a constant infusion of the glycolide monomer is detailed. Using poly(ethylene glycol) as a macroinitiator, amphiphilic block copolymers were synthesized. Co-formulating a paclitaxel silicate and an amphiphilic block copolymer via flash nanoprecipitation led to highly prodrug-loaded, kinetically trapped nanoparticles. Studies to determine the structure, morphology, behavior, and efficacy of these nanoparticles are described in Chapter 5. Efforts to develop a general strategy for the selective end-functionalization of the polyether block of these amphiphilic block copolymers are discussed in Chapter 6. Examples of this strategy include functionalization of the polyether with an azide or a maleimide. Finally, Chapter 7 provides an outlook for future development of

  18. Poly(ethylene glycol) grafted polylactide based copolymers for the preparation of PLA-based nanocarriers and hybrid hydrogels.

    PubMed

    Riva, Raphaël; Schmeits, Stéphanie; Croisier, Florence; Lecomte, Philippe; Jérôme, Christine

    2015-01-01

    In previous works, poly(D,L-lactide-co-ɛCL-poly(ethylene glycol) (poly(D,L-La-co-αPEGɛCL) amphiphilic graft-copolymers were successfully synthesized according to a copper azide-alkyne cycloaddition (CuAAC) strategy. This paper aims at reporting on the behavior of this amphiphilic copolymer in water, which was not studied in the previous paper. Moreover, the ability of the copolymer to stabilize a PLA nanoparticles aqueous suspension is presented. For this purpose, dynamic light scattering (DLS) and transmission electron microscopy (TEM) are proposed to characterize the nanoparticles in solution. Otherwise, the strategy developed for the synthesis of the amphiphilic copolymers was adapted and extended to the synthesis of PLA-based degradable hydrogel, potentially applicable as drug-loaded degradable polymer implant.

  19. Adsorption of a PEO-PPO-PEO triblock copolymer on metal oxide surfaces with a view to reducing protein adsorption and further biofouling.

    PubMed

    Yang, Y; Poleunis, C; Románszki, L; Telegdi, J; Dupont-Gillain, C C

    2013-01-01

    Abstract Biomolecule adsorption is the first stage of biofouling. The aim of this work was to reduce the adsorption of proteins on stainless steel (SS) and titanium surfaces by modifying them with a poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO triblock copolymer. Anchoring of the central PPO block of the copolymer is known to be favoured by hydrophobic interaction with the substratum. Therefore, the surfaces of metal oxides were first modified by self-assembly of octadecylphosphonic acid. PEO-PPO-PEO preadsorbed on the hydrophobized surfaces of titanium or SS was shown to prevent the adsorption of bovine serum albumin (BSA), fibrinogen and cytochrome C, as monitored by quartz crystal microbalance (QCM). Moreover, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry were used to characterize the surfaces of the SS and titanium after competitive adsorption of PEO-PPO-PEO and BSA. The results show that the adsorption of BSA is well prevented on hydrophobized surfaces, in contrast to the surfaces of native metal oxides.

  20. Effect of ultraviolet radiation in the photo-oxidation of High Density Polyethylene and Biodegradable Polyethylene films

    NASA Astrophysics Data System (ADS)

    Martínez-Romo, A.; González Mota, R.; Bernal, J. J. Soto; Frausto Reyes, C.; Rosales Candelas, I.

    2015-01-01

    One of the most widely used plastics in the world is the High density polyethylene (HDPE), it is a stable material due to its carbon-carbon bonds, causing their slow degradation; which is why we are looking for alternative ways to accelerate the degradation process of this polymer. An alternative is the addition of oxidized groups in its molecular structure, which results in the development of polymers susceptible to biodegradation (PE-BIO). In this paper, HDPE and PE-BIO films were exposed to UV-B radiation (320-280 nm) at different exposure times, 0-60 days. The effects of UV radiation in samples of HDPE and PE-BIO were characterized using infrared spectroscopy with attenuated total reflectance (ATR). The results show that the exposed materials undergo changes in their molecular structure, due to the infrared bands formed which corresponds to the photo-oxidation of HDPE and PE films when submitted to UV-B radiation.

  1. Oxidation-Resistant Coating For Bipolar Lead/Acid Battery

    NASA Technical Reports Server (NTRS)

    Bolstad, James J.

    1993-01-01

    Cathode side of bipolar substrate coated with nonoxidizable conductive layer. Coating prepared as water slurry of aqueous dispersion of polyethylene copolymer plus such conductive fillers as tin oxide, titanium, tantalum, or tungsten oxide. Applied easily to substrate of polyethylene carbon plastic. As slurry dries, conductive, oxidation-resistant coating forms on positive side of substrate.

  2. Facile Synthesis of Novel Polyethylene-Based A-B-C Block Copolymers Containing Poly(methyl methacrylate) Using a Living Polymerization System.

    PubMed

    Song, Xiangyang; Ma, Qiong; Cai, Zhengguo; Tanaka, Ryo; Shiono, Takeshi; Grubbs, Robert B

    2016-02-01

    Ethylene-propylene-methyl methacrylate (MMA) and ethylene-hexene-MMA A-B-C block copolymers with high molecular weight (>100,000) are synthesized using fluorenylamide-ligated titanium complex activated by modified methylaluminoxane and 2,6-di-tert-butyl-4-methylphenol for the first time. After diblock copolymerization of olefin is conducted completely, MMA is added and activated by aluminum Lewis acid to promote anionic polymerization. The length of polyolefin and poly (methyl methacrylate) (PMMA) is controllable precisely by the change of the additive amount of olefin and polymerization time, respectively. A soft amorphous polypropylene or polyhexene segment is located between two hard segments of semicrystalline polyethylene and glassy PMMA blocks.

  3. Poly(dimethyl siloxane) (PDMS) network blends of amphiphilic acrylic copolymers with poly(ethylene glycol)-fluoroalkyl side chains for fouling-release coatings. II. Laboratory assays and field immersion trials.

    PubMed

    Martinelli, Elisa; Sarvothaman, Mahesh K; Galli, Giancarlo; Pettitt, Michala E; Callow, Maureen E; Callow, James A; Conlan, Sheelagh L; Clare, Anthony S; Sugiharto, Albert B; Davies, Cait; Williams, David

    2012-01-01

    Amphiphilic copolymers containing different amounts of poly(ethylene glycol)-fluoroalkyl acrylate and polysiloxane methacrylate units were blended with a poly(dimethyl siloxane) (PDMS) matrix in different proportions to investigate the effect of both copolymer composition and loading on the biological performance of the coatings. Laboratory bioassays revealed optimal compositions for the release of sporelings of Ulva linza, and the settlement of cypris larvae of Balanus amphitrite. The best-performing coatings were subjected to field immersion tests. Experimental coatings containing copolymer showed significantly reduced levels of hard fouling compared to the control coatings (PDMS without copolymer), their performance being equivalent to a coating based on Intersleek 700™. XPS analysis showed that only small amounts of fluorine at the coating surface were sufficient for good antifouling/fouling-release properties. AFM analyses of coatings under immersion showed that the presence of a regular surface structure with nanosized domains correlated with biological performance.

  4. pH-sensitive methacrylic copolymer gels and the production thereof

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-05-15

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

  5. Cross-linked nanoassemblies from poly(ethylene glycol)-poly(aspartate) block copolymers as stable supramolecular templates for particulate drug delivery.

    PubMed

    Lee, Hyun Jin; Bae, Younsoo

    2011-07-11

    Block copolymer cross-linked nanoassemblies (CNAs) were developed as stable supramolecular templates for particulate drug delivery. Poly(ethylene glycol)-poly(aspartate) [PEG-p(Asp)] block copolymers, consisting of PEG (5 or 12 kDa) and Asp (5, 14, 25, 33, and 37 repeating units), were used as scaffolds and grafts in combination to prepare a nanoassembly library of grafted nanoassemblies (GNAs) and CNAs. Four synthesis routes were tested to maximize the number of drug-binding Asp units per nanoassembly. Grafting-onto-scaffold and grafting-from-scaffold methods were used for GNA synthesis. Either partially or completely deprotected PEG-p(Asp) was cross-linked with diamine compounds to prepare CNAs. (1)H NMR and GPC measurements showed that GNAs and CNAs contained the maximum 183 and 253 Asp units, respectively. Initial screening of the nanoassemblies revealed that GNAs would be impractical for further development as drug carriers due to variable grafting efficiency and low product yields. CNAs were obtained in high yields and identified as a promising supramolecular template that can entrap and release ionizable drugs (doxorubicin), enhancing the particle stability of nanoassemblies in the pharmaceutically relevant pH ranges between 4 and 9. Light scattering measurements demonstrated that the particle size of CNAs remained uniform before and after drug entrapment, causing neither aggregation nor dissociation (<5 mg/mL).

  6. A new formulation of curcumin using poly (lactic-co-glycolic acid)—polyethylene glycol diblock copolymer as carrier material

    NASA Astrophysics Data System (ADS)

    Phuong Tuyen Dao, Thi; Hoai Nguyen, To; To, Van Vinh; Ho, Thanh Ha; Nguyen, Tuan Anh; Chien Dang, Mau

    2014-09-01

    The aim of this study is to fabricate a nanoparticle formulation of curcumin using a relatively new vehicle as the matrix polymer: poly(lactic-co-glycolic acid) (PLGA)- polyethylene glycol (PEG) diblock copolymer, and to investigate the effects of the various processing parameters on the characteristics of nanoparticles (NPs). We successfully synthesized the matrix polymer of PLGA-PEG by conjugation of PLGA copolymer with a carboxylate end group to a heterobifunctional amine-PEG-methoxy using N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide as conjugation crosslinkers. The composition of the formed product (PLGA-PEG) was characterized with 500 MHz 1H nuclear magnetic resonance (NMR). The conjugation of PLGA-PEG was confirmed using Fourier transform infrared (FTIR) spectrum study. This diblock copolymer was then used to prepare the curcumin-loaded NPs through nanoprecipitation technique. With this method, we found that the size distribution depends on the type of solvent, the concentration of polymer and the concentration of surfactant. The particle size and size distribution were measured by dynamic light scattering (DLS). Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to confirm the size, structure and morphology of the successfully prepared NPs. All of our results showed that they are spherical and quite homologous with mean diameter around of 100-300 nm. Further, we evaluated encapsulation efficiency and some characteristics of NPs through high performance liquid chromatography (HPLC) analyses, zeta-potential measurements and x-ray diffraction studies. The HPLC analyses were performed to determine the amount of curcumin entrapped in NPs. The zeta-potential measurements confirmed the stability of NPs and the successful encapsulation of curcumin within NPs and the x-ray diffraction patterns showed the disordered-crystalline phase of curcumin inside the polymeric matrix.

  7. Effect of Chemical Oxidation on the Self-Assembly of Organometallic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Eitouni, Hany

    2005-03-01

    The thermodynamic interactions in ferrocenyldimethylsilane diblock copolymers were systematically adjusted by oxidation of the ferrocene moiety with silver nitrate and examined using small angle x-ray scattering and depolarized light scattering. The polymers retained microphase separated ordered structures upon oxidation and showed systematic changes in the location of the order-disorder transition as a function of ferrocenium nitrate content. The extent of oxidation can be controlled locally through electrochemical techniques and hence ordered and disordered regions can be maintained within a sample. By controlling the redox properties of the ferrocene moiety in the backbone of the polymer, we have provided a novel method of controlling microstructure and hence bulk properties.

  8. Conduction mechanisms in concentrated LiI-polyethylene oxide-Al{sub 2}O{sub 3}-based solid electrolytes

    SciTech Connect

    Golodnitsky, D.; Ardel, G.; Strauss, E.; Peled, E.; Lareah, Y.; Rosenberg, Y.

    1997-10-01

    The ionic conductivity of concentrated LiI-polyethylene oxide P(EO){sub n} high surface area oxide composite polymer electrolytes has been investigated. Two different Arrhenius dependences for concentrated composite polymer electrolytes (CPEs) have been identified. The first one is characterized by an inflection point at about 80 C, and the second, by a conductivity jump. The authors have suggested that in CPEs, where 3oxide matrix, Li salt to ethylene oxide ratio, copolymers, and solvents on polymer electrolyte conductivity (especially at T >T{sub k}orT{sub jump}) and on Ea have been studied (T{sub jump}=temperature of the conductivity jump). The addition of small quantities of ethylene carbonate, poly(methyl methacrylate), and polyacrylonitrile were found to be beneficial while poly(methyl acrylate), poly(butyl acrylate), and poly(vinylidene fluoride) additions made the polymer electrolyte stiffer and less conductive. MgO, Al{sub 2}O{sub 3}, and potassium aluminosilicate muscovite mica based CSEs have similar conductivity. Results clearly demonstrated the depression of CPE crystallinity by addition of fine Al{sub 2}O{sub 3} powder, ethylene carbonate, and poly(ethylene glycol) dimethyl ether, in agreement with the conductivity enhancement of the CPE.

  9. Extrusion of polysaccharide nanocrystal reinforced polymer nanocomposites through compatibilization with poly(ethylene oxide).

    PubMed

    Pereda, Mariana; El Kissi, Nadia; Dufresne, Alain

    2014-06-25

    Polysaccharide nanocrystals with a rodlike shape but with different dimensions and specific surface area were prepared from cotton and capim dourado cellulose, and with a plateletlike morphology from waxy maize starch granules. The rheological behavior of aqueous solutions of poly(ethylene oxide) (PEO) with different molecular weights when adding these nanoparticles was investigated evidencing specific interactions between PEO chains and nanocrystals. Because PEO also bears hydrophobic moieties, it was employed as a compatibilizing agent for the melt processing of polymer nanocomposites. The freeze-dried mixtures were used to prepare nanocomposite materials with a low density polyethylene matrix by extrusion. The thermal and mechanical behavior of ensuing nanocomposites was studied.

  10. New Applications of Ring-Opening Metathesis Polymerization for Grafting Alkylene Oxide-Based Copolymers

    NASA Astrophysics Data System (ADS)

    Spurcaciu, Bogdan; Buzdugan, Emil; Nicolae, Cristian; Ghioca, Paul; Iancu, Lorena; Dragutan, Valerian; Dragutan, Ileana

    This research tackles the challenges of innovative modification of poly(allyl alkylene oxides) by ROMP to produce new materials. Firstly, binary and ternary copolymers, poly(epichlorohydrin-allyl glycidyl ether) (ECH-AGE) and poly (epichlorohydrin-propylene oxide-allyl glycidyl ether) (ECH-PO-AGE), have been prepared using as initiator a catalytic system consisting of an alkyl aluminium, controlled amounts of water and different compounds (ethers, diols, phosphines, salicylic acid derivatives, organozincs) acting as cocatalysts. Among catalysts explored in these copolymerizations most productive showed to be the systems triisobutylaluminium (TIBA), water and Zn(DIPS)2 or Zn(acac)2. Copolymers which have become thus available were subsequently grafted onto the pendent allylic groups by ROMP with cycloolefins (cyclooctene, norbornene, cyclododecene) involving ruthenium based catalysts.

  11. Preparation, characterization and anticancer activity of norcantharidin-loaded poly(ethylene glycol)-poly(caprolactone) amphiphilic block copolymer micelles.

    PubMed

    Chen, Shui-Fang; Lu, Wen-Fen; Wen, Zhi-Yong; Li, Qiang; Chen, Jian-Hai

    2012-09-01

    In this study, a novel amphiphilic block copolymer biomaterial - poly (ethylene glycol)-poly (caprolactone) (PEG-PCL), was used to entrap norcantharidin (NCTD), taking advantage of self-assembly theory. Dialysis and volatilization dialysis were used to prepare copolymer micelles. Drug-loaded micelles were compared with blank micelles in terms of their particle diameter, morphology and IR spectral characteristics. The results revealed that there was no significant difference in respect of morphology and IR spectrum, but particle size differed. Drug-loaded micelles had a smaller particle size than blank micelles. Three important factors influencing particle size, the drug loading content (LC) and the drug entrapment efficiency (EE) of the NCTD-loaded micelles, were studied. The results indicated that the method of preparation and the type of organic solvent had a significant influence on the size of the micelles. LC and EE were greatly affected by the ratio of NCTD to copolymer. In vitro release of NCTD from the conjugate micelles showed that its release rate depended on the pH of the phosphate buffer solution (PBS). The amount released was higher at lower pH than under neutral conditions. In vitro antitumor activity of the NCTD conjugate against human hepatoma (HepG2) cell line and human lung cancer (A549) cell line was evaluated by the MTT method. Micelles loaded with NCTD demonstrated greater and more satisfactory cell viability inhibition than the free drug. In vivo antitumor activity of drug-loaded micelles was investigated in mice bearing S180 mouse sarcoma. NCTD-loaded micelles displayed tumor inhibition effects, better than the free drug. As a new drug delivery system, copolymer micelles present many advantages including easy formulation, good water solubility, low toxicity and high treatment efficacy, and show great potential as carriers of hydrophobic drugs.

  12. Thermal stability of polyacetal/ethylene-octene copolymer/zinc oxide nanocomposites

    NASA Astrophysics Data System (ADS)

    Grigalovica, A.; Merijs Meri, R.; Zicans, J.; Ivanova, T.; Grabis, J.

    2013-12-01

    In this work we investigate binary blends of polyoxymethylene and ethylene octene copolymer (EOC) and their composites with nanostructured zinc oxide (ZnO). EOC content in the composites varies from 0 to 50 wt. %. The amount of ZnO filler in the composites is changed in the interval from 0 to 5 wt. %. Thermal properties of composites are investigated with thermogravimetric analysis and differential scanning calorimetry. It is observed that ZnO addition increases thermal stability of the investigated composites.

  13. Ethylene/propylene oxide block copolymer interfacial phenomena in relation to coal cleaning by advanced flotation methods

    SciTech Connect

    McCloy, J.L.; Chander, S.

    1995-12-01

    Surface tension of aqueous ethylene/propylene oxide (EO/PO) block copolymer reagents were measured to understand their role in advanced coal flotation. Coal flotation is one of the most promising methods for separating the combustible matter in coal from ash forming minerals. The use of EO/PO block copolymer reagents enhances the rejection of ash minerals during coal flotation procedures. Since the mechanism whereby this enhancement is achieved is not known very well, an investigation of the surface tension characteristics of EO/PO block copolymer reagents was performed at various concentrations. Data obtained were used to compute adsorption densities at the liquid/gas interface. The adsorption characteristics of nine different EO/PO block copolymers were determined to examine the effect of percent ethylene oxide and formula weight. These studies predict that flotation experiments are most efficient when surfactants with low ethylene oxide percentages are utilized.

  14. A free-standing, sheet-shaped, "hydrophobic" biomaterial containing polymeric micelles formed from poly(ethylene glycol)-poly(lactic acid) block copolymer for possible incorporation/release of "hydrophilic" compounds.

    PubMed

    Moroishi, Hitomi; Yoshida, Chikara; Murakami, Yoshihiko

    2013-02-01

    Sheet-shaped materials with a large contact area relative to the drug targeting site lead to advantages over conventional particle-shaped drug carriers and have several advantages for their biomedical applications. The present study proposes a methodology for preparing a novel sheet-shaped "hydrophobic" and biocompatible biomaterial in which polymeric micelles are uniformly dispersed for the incorporation of "hydrophilic" compounds into the sheet. The methoxy-terminated poly(ethylene glycol)-block-poly(lactic acid) block copolymer (CH(3)O-PEG-b-PLA) was successfully synthesized by means of the anionic ring-opening polymerization of both ethylene oxide and dl-lactide. CH(3)O-PEG-b-PLA was self-assembled and formed stable micelle-like w/o emulsion with a hydrophilic inner core in organic solvents. A sheet-shaped material containing a hydrophilic inner space for incorporating hydrophilic compounds was obtained by spin-coating both the micelle solution and a sheet-forming polymer. Fluorescent images of the sheet proved that polymeric micelles providing hydrophilic spaces were uniformly dispersed in the hydrophobic sheet. The facile technique presented in this paper can be a tool for fabricating sheet-shaped biomaterials that have a hydrophilic inner core and, consequently, that are suitable for the sustained release of hydrophilic compounds.

  15. Non-invasive topical drug delivery to spinal cord with carboxyl-modified trifunctional copolymer of ethylene oxide and propylene oxide.

    PubMed

    Kamalov, Marat I; Lavrov, Igor A; Yergeshov, Abdulla A; Siraeva, Zulfira Y; Baltin, Maxim E; Rizvanov, Albert A; Kuznetcova, Svetlana V; Petrova, Natalia V; Savina, Irina N; Abdullin, Timur I

    2016-04-01

    In this study the effect of oxidative modification on micellar and drug delivery properties of copolymers of ethylene oxide (EO) and propylene oxide (PO) was investigated. Carboxylated trifunctional copolymers were synthesized in the reaction with chromium(VI) oxide. We found that carboxylation significantly improved the uniformity and stability of polymeric micelles by inhibiting the microphase transition. The cytotoxicity of copolymers was studied in relation to their aggregative state on two cell types (cancer line vs. primary fibroblasts). The accumulation of rhodamine 123 in neuroblastoma SH-SY5Y cells was dramatically increased in the presence of the oxidized block copolymer with the number of PO and EO units of 83.5 and 24.2, respectively. The copolymer was also tested as an enhancer for topical drug delivery to the spinal cord when applied subdurally. The oxidized copolymer facilitated the penetration of rhodamine 123 across spinal cord tissues and increased its intraspinal accumulation. These results show the potential of using oxidized EO/PO based polymers for non-invasive delivery of protective drugs after spinal cord injury.

  16. FhuA deletion variant Δ1-159 overexpression in inclusion bodies and refolding with Polyethylene-Poly(ethylene glycol) diblock copolymer.

    PubMed

    Dworeck, Tamara; Petri, Anne-Kathrin; Muhammad, Noor; Fioroni, Marco; Schwaneberg, Ulrich

    2011-05-01

    Membrane protein isolation is a challenging problem. In fact especially their extraction from the respective membrane is difficult and often goes along with losses in yield. Usually expensive detergents are needed to extract the target protein from the membrane. Therefore finding an efficient overexpression and extraction method and an alternative to detergents is desirable. In this study we describe a new and fast method to express, extract and purify an engineered variant of the FhuA protein (FhuA Δ1-159) that acts as passive diffusion channel, using a diblock copolymer as an alternative to detergents like octyl-POE (n-octylpolyoxyethylene). The N-terminal leader sequence, facilitating the protein's transport to the outer membrane was deleted (FhuA Δ1-159 Δsignal), resulting in protein accumulation in easy to isolate inclusion bodies. Urea was used to solubilise the unfolded protein and dialysis against phosphate-buffer containing the commercially available diblock copolymer PE-PEG[Polyethylene-Poly(ethyleneglycol)] lead to protein refolding. Circular dichroism spectroscopy revealed a high β-sheet percentage within the refolded protein secondary structure indicating the successful reconstitution of FhuA Δ1-159 Δsignal native state. Furthermore the channel functionality of FhuA Δ1-159 Δsignal was verified by measuring the in and out-flux through the protein when inserted into liposome membrane, using the HRP/TMB (HRP=Horse Radish Peroxidase, TMB=3,3',5,5'-tetramethylbenzidine) assay system.

  17. Enhancement of Airway Gene Transfer by DNA Nanoparticles Using a pH-Responsive Block Copolymer of Polyethylene Glycol and Poly-L-lysine

    PubMed Central

    Boylan, Nicholas J.; Kim, Anthony J.; Suk, Jung Soo; Adstamongkonkul, Pichet; Simons, Brian W.; Lai, Samuel K.; Cooper, Mark J.; Hanes, Justin

    2011-01-01

    Highly compacted DNA nanoparticles, composed of single molecules of plasmid DNA compacted with block copolymers of polyethylene glycol and poly-L-lysine (PEG-CK30), have shown considerable promise in human gene therapy clinical trials in the nares, but may be less capable of transfecting cells that lack surface nucleolin. To address this potential shortcoming, we formulated pH-responsive DNA nanoparticles that mediate gene transfer via a nucleolin-independent pathway. Poly-L-histidine was inserted between PEG and poly-L-lysine to form a triblock copolymer system, PEG-CH12K18. Inclusion of poly-L-histidine increased the buffering capacity of PEG-CH12K18 to levels comparable with branched polyethyleneimine. PEG-CH12K18 compacted DNA into rod-shaped DNA nanoparticles with similar morphology and colloidal stability as PEG-CK30 DNA nanoparticles. PEG-CH12K18 DNA nanoparticles entered human bronchial epithelial cells (BEAS-2B) that lack surface nucleolin by a clathrin-dependent endocytic mechanism followed by endo-lysosomal processing. Despite trafficking through the degradative endo-lysosomal pathway, PEG-CH12K18 DNA nanoparticles improved the in vitro gene transfer by ~ 20-fold over PEG-CK30 DNA nanoparticles, and in vivo gene transfer to lung airways in BALB/c mice by ~ 3-fold, while maintaining a favorable toxicity profile. These results represent an important step toward the rational development of an efficient gene delivery platform for the lungs based on highly compacted DNA nanoparticles. PMID:22182747

  18. Novel 4-arm poly(ethylene glycol)-block-poly(anhydride-esters) amphiphilic copolymer micelles loading curcumin: preparation, characterization, and in vitro evaluation.

    PubMed

    Lv, Li; Shen, Yuanyuan; Li, Min; Xu, Xiaofen; Li, Mingna; Guo, Shengrong; Huang, Shengtang

    2013-01-01

    A novel 4-arm poly(ethylene glycol)-block-poly(anhydride-esters) amphiphilic copolymer (4-arm PEG-b-PAE) was synthesized by esterization of 4-arm poly(ethylene glycol) and poly(anhydride-esters) which was obtained by melt polycondensation of α -, ω -acetic anhydride terminated poly(L-lactic acid). The obtained 4-arm PEG-b-PAE was characterized by (1)H-NMR and gel permeation chromatography. The critical micelle concentration of 4-arm PEG-b-PAE was 2.38 μg/mL. The curcumin-loaded 4-arm PEG-b-PAE micelles were prepared by a solid dispersion method and the drug loading content and encapsulation efficiency of the micelles were 7.0% and 85.2%, respectively. The curcumin-loaded micelles were spherical with a hydrodynamic diameter of 151.9 nm. Curcumin was encapsulated within 4-arm PEG-b-PAE micelles amorphously and released from the micelles, faster in pH 5.0 than pH 7.4, presenting one biphasic drug release pattern with rapid release at the initial stage and slow release later. The hemolysis rate of the curcumin-loaded 4-arm PEG-b-PAE micelles was 3.18%, which was below 5%. The IC50 value of the curcumin-loaded micelles against Hela cells was 10.21 μg/mL, lower than the one of free curcumin (25.90 μg/mL). The cellular uptake of the curcumin-loaded micelles in Hela cell increased in a time-dependent manner. The curcumin-loaded micelles could induce G2/M phase cell cycle arrest and apoptosis of Hela cells.

  19. Application of the aqueous two-phase systems of ethylene and propylene oxide copolymer-maltodextrin for protein purification.

    PubMed

    Bolognese, Belén; Nerli, Bibiana; Picó, Guillermo

    2005-01-25

    In this study, the effect of several factors that govern the partitioning behaviour of three model proteins, such as bovine serum albumin, lysozyme and trypsin was analysed in a two-phase system formed by maltodextrin and a copolymer of ethylene and propylene oxides. The protein partition coefficient (K(r)) showed to be very sensitive to temperature changes, protein molecular weight, pH medium and the lyotropic ion presence. The phase diagram obtained for these novel polymer-polymer two-phase systems shows two phases with high polymer concentrations. The maltodextrin is enriched in the bottom phase while the copolymer of ethylene and propylene oxides is found in the upper phase. Since this copolymer is thermoreactive, the upper phase can be removed and heated above the copolymer's cloud point resulting in the formation of a new two-phase system with a lower water phase, containing the target protein and an upper copolymer-rich phase. Our results show that systems formed by maltodextrin and a copolymer of ethylene and propylene oxides may be considered as an interesting alternative to be used in protein purification due to their low cost, and also because they offer a viable solution to problems of polymer removal and recycling.

  20. Antibacterial wound dressing from chitosan/polyethylene oxide nanofibers mats embedded with silver nanoparticles.

    PubMed

    Wang, Xiaoli; Cheng, Feng; Gao, Jing; Wang, Lu

    2015-03-01

    Novel antibacterial nanomaterials have been developed for biomedical applications. The present study involves the preparation and properties of antibacterial nanofibers from chitosan/polyethylene oxide electrospun nanofibers incorporated with silver nanoparticles. Silver nanoparticles were efficiently synthesized in situ after ultra violet (UV) with AgNO3 as precursor and chitosan/polyethylene oxide as reducing agent and protecting agent, respectively. Then the resultant solutions were electrospun into nanofibers. The formation of silver nanoparticles was confirmed with ultraviolet visible (UV-vis) and transmission electron microscopy (TEM), and the electrospun nanofibers were characterized by scanning electron microscopy and energy dispersive X-ray. The resultant fibers exhibited uniform morphology with silver nanoparticles distributed throughout the fiber. Also, the fibers showed certain tensile strength and excellent antibacterial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Sustained release of silver nanoparticles from fibers could last for over 72 h. The silver-containing chitosan/polyethylene oxide nanofibers showed excellent cytocompatibility.

  1. The stimulation of postdermabrasion wound healing with stabilized aloe vera gel-polyethylene oxide dressing.

    PubMed

    Fulton, J E

    1990-05-01

    Full-face dermabrasion provided an ideal opportunity to document the effects of dressings on wound healing management. Following the procedure, the abraded face was divided in half. One side was treated with the standard polyethylene oxide gel wound dressings. The other side was treated with a polyethylene oxide gel dressing saturated with stabilized aloe vera. The polyethylene oxide dressing provided an excellent matrix for the release of aloe vera gel during the initial 5 days of wound healing. By 24-48 hours there was dramatic vasoconstriction and accompanying reduction in edema on the aloe-treated side. By the third to fourth day there was less exudate and crusting at the aloe site, and by the fifth to sixth day the reepithelialization at the aloe site was complete. Overall, wound healing was approximately 72 hours faster at the aloe site. This acceleration in wound healing is important to reduce bacterial contamination, subsequent keloid formation, and/or pigmentary changes. The exact mechanism of acceleration of wound healing by aloe vera is unknown.

  2. Efficient anti-tumor effect of photodynamic treatment with polymeric nanoparticles composed of polyethylene glycol and polylactic acid block copolymer encapsulating hydrophobic porphyrin derivative.

    PubMed

    Ogawara, Ken-ichi; Shiraishi, Taro; Araki, Tomoya; Watanabe, Taka-ichi; Ono, Tsutomu; Higaki, Kazutaka

    2016-01-20

    To develop potent and safer formulation of photosensitizer for cancer photodynamic therapy (PDT), we tried to formulate hydrophobic porphyrin derivative, photoprotoporphyrin IX dimethyl ester (PppIX-DME), into polymeric nanoparticles composed of polyethylene glycol and polylactic acid block copolymer (PN-Por). The mean particle size of PN-Por prepared was around 80nm and the zeta potential was determined to be weakly negative. In vitro phototoxicity study for PN-Por clearly indicated the significant phototoxicity of PN-Por for three types of tumor cells tested (Colon-26 carcinoma (C26), B16BL6 melanoma and Lewis lung cancer cells) in the PppIX-DME concentration-dependent fashion. Furthermore, it was suggested that the release of PppIX-DME from PN-Por would gradually occur to provide the sustained release of PppIX-DME. In vivo pharmacokinetics of PN-Por after intravenous administration was evaluated in C26 tumor-bearing mice, and PN-Por exhibited low affinity to the liver and spleen and was therefore retained in the blood circulation for a long time, leading to the efficient tumor disposition of PN-Por. Furthermore, significant and highly effective anti-tumor effect was confirmed in C26 tumor-bearing mice with the local light irradiation onto C26 tumor tissues after PN-Por injection. These findings indicate the potency of PN-Por for the development of more efficient PDT-based cancer treatments.

  3. Formulation and in vitro characterization of novel sildenafil citrate-loaded polyvinyl alcohol-polyethylene glycol graft copolymer-based orally dissolving films.

    PubMed

    Xu, Li-Li; Shi, Li-Li; Cao, Qing-Ri; Xu, Wei-Juan; Cao, Yue; Zhu, Xiao-Yin; Cui, Jing-Hao

    2014-10-01

    This work was aimed to develop novel sildenafil citrate (SC)-loaded polyvinyl alcohol (PVA)-polyethylene glycol (PEG) graft copolymer (Kollicoat(®) IR)-based orally dissolving films (ODFs) using a solvent casting method. Formulation factors such as plasticizers and disintegrants were optimized on the basis of characteristics of blank ODFs. The SC-loaded ODF with a loading capacity up to 6.25mg in an area of 6 cm(2) was prepared and evaluated in terms of mechanical properties, disintegration time and dissolution rate. The physicochemical properties of drug-loaded ODF were also investigated using the scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The blank ODF composed of Kollicoat(®) IR, sodium alginate (ALG-Na) and glycerol (10:2:1.5, w/w) had a remarkably short disintegration time of about 20s. The SC-loaded ODF showed a delayed disintegration time (about 25s), but exhibited improved mechanical properties when compared to the blank ODF. SC was homogeneously dispersed throughout the ODF and the crystalline form of drug had been partly changed, existing strong hydrogen bonding between the drug and carriers. The Kollicoat(®) IR/ALG-Na based ODFs containing SC might be an alternative to conventional tablet for the treatment of male erectile dysfunction.

  4. Radiation induced graft copolymerization of n-butyl acrylate onto poly(ethylene terephthalate) (PET) films and thermal properties of the obtained graft copolymer

    NASA Astrophysics Data System (ADS)

    Ping, Xiang; Wang, Mozhen; Ge, Xuewu

    2011-05-01

    n-Butyl acrylate (BA) was successfully grafted onto poly(ethylene terephthalate) (PET) film using simultaneous radiation induced graft copolymerization with gamma rays. When BA concentration ranges from 20% to 30%, the Degree of Grafting (DG), measured by gravimetry and 1H NMR, increases with the monomer concentration and absorbed dose, but decreases with dose rate from 0.83 to 2.53 kGy/h. The maximum DG can reach up to 22.1%. The thermal transition temperatures such as glass-transition temperature ( Tg) and cold-crystallization temperature ( Tcc) of PET in grafted films were little different from those in original PET film, indicating that microphase separation occurred between PBA side chains and PET backbone. This work implied that if PET/elastomers (e.g., acrylate rubber) blends are radiated by high energy gamma rays under a certain condition, PET-g-polyacrylate copolymer may be produced in-situ, which will improve the compatibility between PET and the elastomers so as to improve the integral mechanical properties of PET based engineering plastic.

  5. Synthesis and self-assembly of four-armed star copolymer based on poly(ethylene brassylate) hydrophobic block as potential drug carries

    NASA Astrophysics Data System (ADS)

    Chen, Jiucun; Li, Junzhi; Liu, Jianhua; Weng, Bo; Xu, Liqun

    2016-05-01

    A novel well-defined four-armed star poly(ethylene brassylate)- b-poly(poly(ethylene glycol)methyl ether methacrylate) (s-PEB- b-P(PEGMA)) was synthesized and self-assembled via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization (RAFT) in this work. It proceeded firstly with the synthesis of hydrophobic four-armed star homopolymer of ethylene brassylate (EB) via ROP with organic catalyst, followed by the esterification reaction of s-PEB with chain transfer agent. Afterward, RAFT polymerization of PEGMA monomer was initialed using PEB-based macro-RAFT agent, resulting in the target amphiphilic four-armed star copolymer. The obtained s-PEB- b-P(PEGMA) can assemble into micelles with PEB segments as core and P(PEGMA) segments as shell in aqueous solution. The self-assembly behavior was studied by dynamic light scattering and transmission electron microscope. The micelles of s-PEB- b-P(PEGMA) exhibited higher loading capacity of the anticancer drug doxorubicin (DOX). The investigation of DOX release from the micelles demonstrated that the release rate of the hydrophobic drug could be effectively controlled.

  6. Thermal oxidative degradation of ethylene tetrafluoroethylene copolymer systems

    NASA Astrophysics Data System (ADS)

    Elders, Jonathan Patrick

    Thermo-oxidative degradation of ethylene tetrafluoroethylene (ETFE) was investigated to determine how modifications for use in an electrical wire system affected its thermal stability. Modifications included electron irradiation and subsequent cross-linking during manufacture and contact with a metal surface. Samples with irradiation histories between 0 and 48 MRads were investigated. Degradation of ETFE was enhanced by contact with a metal "conductor" surface: silver - coated copper. Polymer degradation was analyzed by weight loss kinetics (thermogravimetric analysis (TGA)), changes in polymer morphology (differential scanning calorimetry (DSC)), optical microscopy, attenuated total reflectance (ATR) infrared spectroscopy, and gas chromatography - mass spectroscopy (GC/MS). Conductor aging (copper permeation through silver with subsequent oxidation) was investigated using scanning Auger Electron Spectroscopy (AES). Conductor aging is enhanced in the presence of the polymer surface. Interactions between conductor and polymer were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The rate of polymer degradation from 220°C to 280°C was independent of time and extent of degradation, and rate was proportional to irradiation dose. The activation energy for degradation of unirradiated ETFE was 227 kJ/mol and decreased from 150 to 138 kJ/mol for ETFE irradiated to doses between 6 and 48 MRads. Rates of degradation at 300°C to 320°C were dependent on the extent of degradation. Rates of degradation at temperatures between 230°C and 310°C were an order of magnitude larger in the presence of a conductor than in its absence, and activation energies for degradation in the presence of conductor were reduced to 120 kJ/mol. Degradation was modeled as the combination of bulk polymer degradation and catalytic degradation at the polymer-metal interface. ETFE aged at 250°C in the presence or absence of a conductor

  7. All-atom molecular dynamics study of a spherical micelle composed of N-acetylated poly(ethylene glycol)-poly(gamma-benzyl L-glutamate) block copolymers: a potential carrier of drug delivery systems for cancer.

    PubMed

    Kuramochi, Hiroshi; Andoh, Yoshimichi; Yoshii, Noriyuki; Okazaki, Susumu

    2009-11-19

    An all-atom molecular dynamics simulation of a spherical micelle composed of amphiphilic N-acetylated poly(ethylene glycol)-poly(gamma-benzyl L-glutamate) (PEG-PBLG-Ac) block copolymers was performed in aqueous solution at 298.15 K and 1 atm. Such copolymers have received considerable attention as carriers in drug delivery systems. In this study, we used copolymers consisting of 11 EG units and 9 BLG units as models. Starting from the copolymers arranged spherically, the calculation predicted an equilibrium state consisting of a slightly elliptical micelle structure with a hydrophobic PBLG inner core and a hydrophilic PEG outer shell. The micelle structure was dynamically stable during the simulation, with the PEG blocks showing a compact helical conformation and the PBLG blocks an alpha-helix form. Multiple hydrogen bonds with solvent water molecules stabilized the helical conformation of the PEG blocks, leading to their hydration as shown by longer residence times of water molecules near the PEG ether oxygen atoms compared with that of bulk water. Some water molecules have also been found distributed within the hydrophobic core; they showed continuous exchange with bulk water during the simulation. Those molecules existed mostly as a cluster in spaces between the copolymers, forming hydrogen bonds among themselves as well as with the hydrophobic core through hydrophilic groups such as esters and amides. The water molecules forming hydrogen bonds with the micelle may play an important role in the stabilization of the micelle structure.

  8. Janus-Type Dendrimer-like Poly(ethylene oxide)s

    PubMed Central

    Feng, Xiaoshuang; Taton, Daniel; Ibarboure, Emmanuel; Chaikof, Elliot L.; Gnanou, Yves

    2009-01-01

    A straightforward and original methodology allowing the synthesis of Janus-type dendrimer-like poly(ethylene oxide)s (PEOs) carrying orthogonal functional groups on their surface is described. The use of 3-allyloxy-1,2-propanediol (1) as a latent AB2-type heterofunctional initiator of anionic ring-opening polymerization (AROP) of ethylene oxide (EO) and of selective branching agents of PEO chain ends served to construct the two dendrons of these dendrimer-like PEOs, following a divergent pathway. Thus, the first PEO generation of the first dendron was grown by AROP from 1 followed by the reaction of the corresponding α-allyl,ω,ω′-bishydroxy- heterofunctional PEO derivative with 2-(3′-chloromethybenzyloxymethyl)-2-methyl-5,5-dimethyl-1,3-dioxane (2) used as a branching agent. This afforded the dendron A with four latent peripheral hydroxyls protected in the form of two ketal rings. The remaining α-allylic double bond of the PEO thus prepared was transformed into two hydroxyl groups using OsO4 in order to create the first PEO generation of the dendron B by AROP of EO. Allyl chloride (3) was then used as another (latent) branching agent to react with the terminal hydroxyl of the corresponding PEO chains. Deprotection under acidic conditions of the ketal groups of dendron A, followed by AROP of EO, afforded the second PEO generation on this face. This alternate and divergent procedure, combining AROP of EO and selective branching of PEO branches, could be readily iterated, one dendron after the other up to the generation six, leading to a Janus-type dendrimer-like PEO exhibiting a total mass of around 300 kg/mol and possessing 64 peripheral groups on each face. The possibility of orthogonal functionalization of the surfaces of such Janus-type dendritic PEOs was exploited. Indeed, a dendron of generation 4 was functionalized with hydroxyl functions at its periphery, whereas the other was end-capped with either tertiary amino or disulfide groups. In a variant of

  9. Oxidation in ultrahigh molecular weight polyethylene and cross-linked polyethylene acetabular cups tested against roughened femoral heads in a hip joint simulator.

    PubMed

    Taddei, Paola; Affatato, Saverio; Fagnano, Concezio; Toni, Aldo

    2006-06-01

    This study was aimed at comparing the oxidative degradation of commercial acetabular cups made of cross-linked polyethylene (XLPE) and conventional ultrahigh molecular weight polyethylene (UHMWPE). After testing against deliberately scratched CoCrMo femoral heads in a hip joint simulator, the cups, microtomed parallel to the articulating surface, were analyzed by IR spectroscopy. Due to the potential for artifacts caused by absorbed contaminants, the IR spectra were compared only after hexane extraction; actually, XLPE was found to absorb more serum than UHMWPE. The two sets of unworn acetabular cups showed different oxidation patterns with consequently different distributions of carbonyl species; unworn XLPE was characterized by lower contents of carbonyl species and hydrogen-bonded alcohols and higher contents of trans-vinylene species than unworn UHMWPE. Upon simulator testing, UHMWPE showed more significant changes in oxidation indexes and distribution of carbonyl compounds than XLPE, confirming a better wear behavior for XLPE under the adopted testing conditions.

  10. Polyethylene encapsulation of molten salt oxidation mixed low-level radioactive salt residues

    SciTech Connect

    Lageraaen, P.R.; Kalb, P.D.; Grimmett, D.L.; Gay, R.L.; Newman, C.D.

    1995-10-01

    A limited scope treatability study was conducted for polyethylene encapsulation of salt residues generated by a Molten Salt Oxidation (MSO) technology demonstration at the Energy Technology Engineering Center (ETEC), operated by Rockwell International for the US Department of Energy (DOE). During 1992 and 1993, ETEC performed a demonstration with a prototype MSO unit and treated approximately 50 gallons of mixed waste comprised of radioactively contaminated oils produced by hot cell operations. A sample of the mixed waste contaminated spent salt was used during the BNL polyethylene encapsulation treatability study. A nominal waste loading of 50 wt % was successfully processed and waste form test specimens were made for Toxicity Characteristic Leaching Procedure (TCLP) testing. The encapsulated product was compared with base-line TCLP results for total chromium and was found to be well within allowable EPA guidelines.

  11. Synthesis of cobalt stearate as oxidant additive for oxo-biodegradable polyethylene

    SciTech Connect

    Asriza, Ristika O.; Arcana, I Made

    2015-09-30

    Cobalt stearate is an oxidant additives that can initiate a process of degradation in high density polyethylene (HDPE). To determine the effect of cobalt stearate in HDPE, oxo-biodegradable polyethylene film was given an irradiation with UV light or heating at various temperature. After given a heating, the FTIR spectra showed a new absorption peak at wave number 1712 cm{sup −1} indicating the presence of carbonyl groups in polymers, whereas after irradiation with UV light is not visible the presence of this absorption peak. The increase concentration of cobalt stearate added in HDPE and the higher heating temperature, the intensity of the absorption peak of the carbonyl group increased. The increasing intensity of the carbonyl group absorption is caused the presence of damage in the film surface after heating, and this result is supported by analysis the surface properties of the film with using SEM. Biodegradation tests were performed on oxo-biodegradable polyethylene film which has been given heating or UV light with using activated sludge under optimal conditions the growth of microorganisms. After biodegradation, the maximum weight decreased by 23% in the oxo-biodegradable polyethylene film with a cobalt stearate concentration of 0.2% and after heating at a temperature of 75 °C for 10 days, and only 0.69% in the same film after irradiation UV light for 10 days. Based on the results above, cobalt stearate additive is more effective to initiate the oxidative degradation of HDPE when it is initiated by heating compared to irradiation with UV light.

  12. Improved oral absorption of doxorubicin by amphiphilic copolymer of lysine-linked ditocopherol polyethylene glycol 2000 succinate: in vitro characterization and in vivo evaluation.

    PubMed

    Wang, Jinling; Li, Lin; Du, Yuqian; Sun, Jin; Han, Xiaopeng; Luo, Cong; Ai, Xiaoyu; Zhang, Qi; Wang, Yongjun; Fu, Qiang; Yang, Zhifu; He, Zhonggui

    2015-02-02

    In the previous study, we have synthesized an amphiphilic copolymer of nanostructure-forming material and P-glycoprotein (P-gp) inhibitor, lysine-linked ditocopherol polyethylene glycol 2000 succinate (PLV2K). The cytotoxicty in vitro and anticancer efficacy in vivo after intravenous administration of DOX-loaded PLV2K micelles (PLV2K-DOX) was found more effective than DOX solution (DOX-Sol). However, its performance and mechanism on oral absorption of doxorubicin are not well understood yet. PLV2K-DOX are spherical micelles with a narrow size distribution of 20.53 ± 2.44 nm. With an in situ intestinal perfusion model, the intestinal absorption potential of PLV2K-DOX was evaluated in comparison with DOX-Sol. PLV2K-DOX was specifically absorbed in duodenum and ileum sites of rats after oral administration. The intestinal absorption rate (Ka) of PLV2K-DOX is 3.19-, 1.61-, and 1.80-fold higher than that of DOX-Sol in duodenum, jejunum, and ileum, respectively. In Caco-2 uptake studies, PLV2K-DOX micelles significantly improve the internalized amount of DOX by P-gp inhibition of free PLV2K copolymer and endocytosis of DOX-loaded nanoparticles. Moreover, PLV2K-DOX micelles improve the membrane permeability of DOX by multiple transcytosis mechanisms, including caveolin-, clathrin-dependent, and caveolin-/clathrin-independent transcytosis in Caco-2 transport studies. However, the transepithelia electrical resistance (TEER) of Caco-2 cellular monolayer is not changed, suggesting no involvement of paracellular transport of PLV2K-DOX. In vivo pharmacokinetics in rats following oral administration demonstrated that PLV2K-DOX demonstrates higher AUC (5.6-fold) and longer t1/2 (1.2-fold) than DOX-Sol. The findings suggest the new PLV2K micelles might provide an effective nanoplatform for oral delivery of anticancer drugs with poor membrane permeability and low oral bioavailability.

  13. Fabrication of Ordered Mesoporous Silica with Encapsulated Iron Oxide Particles using Ferritin-Doped Block Copolymer Templates

    NASA Astrophysics Data System (ADS)

    Hess, D.; Watkins, J.; Naik, R.

    2006-03-01

    Recently, two-dimensional arrays of iron oxide clusters were fabricated by dip-coating a silica substrate into an aqueous solution. Here we report the encapsulation of ferritin in 3D mesoporous silica structures by the replication of block copolymer templates in supercritical CO2. In our approach, preparation of the highly ordered, doped template via spincasting and microphase separation and silica network formation occur in discreet steps. A solution of an amphiphilic PEO-PPO-PEO triblock copolymer (Pluronic) template, horse spleen ferritin and a low concentration of PTSA acid was prepared and spin-coated onto a Si wafer. Upon drying the block copolymer microphase separates resulting in partitioning of the acid catalyst and ferritin to the hydrophilic domain. The polymer template was then exposed to a solution of supercritical carbon dioxide and tetraethyl orthosilicate (TEOS) at 125 bar and 40^oC. Equilibrium limited CO2 sorption in the block copolymer template resulted in modest dialation of the microphase segregated structure. Under these conditions, the precursor was readily infused into the copolymer and reacted within the hydrophilic domain containing the acid catalyst. The resultant film was calcined in air at 400^oC for 6 hours producing a well-ordered iron oxide-doped mesoporous silica film. TEM and XRD revealed crystalline iron oxide structures within the mesoporous silica supports. Magnetic properties were analyzed using a superconducting quantum intereference device (SQUID).

  14. Synthesis of hybrid gold/iron oxide nanoparticles in block copolymer micelles for imaging, drug delivery and magnetic hyperthermia.

    SciTech Connect

    Kim, D.-H.; Rozhkova, E. A.; Rajh, T.; Bader, S. D.; Novosad, V.

    2009-10-01

    In our study, hybrid gold/iron oxide loaded thermoresponsive micelles were synthesized for combined hyperthermia and chemotherapy, and optical imaging. Polymeric micelles made of amphiphilic block copolymer of poly(N-isopropylacrylamide-co-acrylamide)-block-poly({var_epsilon}-caprolactone) were conjugated with gold/iron oxide particles which are self-assembled at the hydrophobic polymer core. Thermal sensitivity and magnetic and optical properties of the hybrid gold/iron oxide micelles were investigated for the combined therapy and optical imaging.

  15. Custom-made morphologies of ZnO nanostructured films templated by a poly(styrene-block-ethylene oxide) diblock copolymer obtained by a sol-gel technique.

    PubMed

    Sarkar, Kuhu; Rawolle, Monika; Herzig, Eva M; Wang, Weijia; Buffet, Adeline; Roth, Stephan V; Müller-Buschbaum, Peter

    2013-08-01

    Zinc oxide (ZnO) nanostructured films are synthesized on silicon substrates to form different morphologies that consist of foamlike structures, wormlike aggregates, circular vesicles, and spherical granules. The synthesis involves a sol-gel mechanism coupled with an amphiphilic diblock copolymer poly(styrene-block-ethylene oxide), P(S-b-EO), which acts as a structure-directing template. The ZnO precursor zinc acetate dihydrate (ZAD) is incorporated into the poly(ethylene oxide) block. Different morphologies are obtained by adjusting the weight fractions of the solvents and ZAD. The sizes of the structure in solution for different sol-gels are probed by means of dynamic light scattering. Thin-film samples with ZnO nanostructures are prepared by spin coating and solution casting followed by a calcination step. On the basis of various selected combinations of weight fractions of the ingredients used, a ternary phase diagram is constructed to show the compositional boundaries of the investigated morphologies. The evolution and formation mechanisms of the morphologies are addressed in brief. The surface morphologies of the ZnO nanostructures are studied with SEM. The inner structures of the samples are probed by means of grazing incidence small-angle X-ray scattering to complement the SEM investigations. XRD measurements confirm the crystallization of the ZnO in the wurtzite phase upon calcination of the nanocomposite film in air. The optical properties of ZnO are analyzed by FTIR and UV/Vis spectroscopy.

  16. Effect of Oxidation on Localized Heat Generation and Dielectric Breakdown of Low-Density Polyethylene Film

    NASA Astrophysics Data System (ADS)

    Tsurimoto, Takao; Nagao, Masayuki; Kosaki, Masamitsu

    1995-12-01

    The effect of oxidation on localized heat generation and dielectric breakdown in low-density polyethylene (LDPE) film was studied by thermography. In the non-McKeown-type epoxy-free electrode system, localized heat generation of LDPE film leading to dielectric breakdown increased and breakdown strength decreased upon oxidation. In the McKeown-type specimen, however, the breakdown strength of oxidized LDPE film is higher than that of an unoxidized one. It is considered that enhancement of the thermal process is a major factor of breakdown in the epoxy-free electrode system and that homo-space charge and/or electron scattering effect is dominant in the McKeown type specimen.

  17. Effect of polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer on bioadhesion and release rate property of eplerenone pellets.

    PubMed

    Kendre, Prakash Namdeo; Chaudhari, Pravin Digambar

    2017-05-01

    The present study involved the design and development of oral bioadhesive pellets of eplerenone. A solid dispersion of eplerenone was developed with a hydrophilic carrier, polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus(®)). Bioadhesive pellets were prepared from this solid dispersion using a combination of HPMC K4M and Carbopol 934P. Both the solid dispersion and the pellets were evaluated for various physicochemical properties such as solubility, entrapment efficiency, drug content, surface morphology, mucoadhesion and swelling behavior. Analysis carried out using FT-IR, DSC and XRD found no interaction between the eplerenone and excipients. The solid dispersion had irregular-shaped smooth-surfaced particles of diameter 265 ± 105.5 μm. In TEM analysis, eplerenone particles of size 79-120 nm were found. The solubility and dissolution of eplerenone in the Soluplus(®)-based solid dispersion were 5.26 and 2.50 times greater, respectively. Investigation of the swelling behavior of the pellets showed that the thickness of the gel layer increased continuously over the duration of the study. Moreover, a correlation was observed between the thickness and strength of the gel layer and the percentage release. The mechanism of drug release was found to be non-Fickian (anomalous), with the release kinetics approaching first-order kinetics. The bioavailability of the eplerenone bioadhesive pellet formulation was studied using Wistar rats and was found to be improved. An in vivo mucoadhesion study showed that the pellets are retained for 24 h in rabbits. It was concluded that Soluplus(®) had a positive effect on the solubility and dissolution of pellets without affecting the bioadhesion.

  18. Electrochemically oxidized electronic and ionic conducting nanostructured block copolymers for lithium battery electrodes.

    PubMed

    Patel, Shrayesh N; Javier, Anna E; Balsara, Nitash P

    2013-07-23

    Block copolymers that can simultaneously conduct electronic and ionic charges on the nanometer length scale can serve as innovative conductive binder material for solid-state battery electrodes. The purpose of this work is to study the electronic charge transport of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-PEO) copolymers electrochemically oxidized with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in the context of a lithium battery charge/discharge cycle. We use a solid-state three-terminal electrochemical cell that enables simultaneous conductivity measurements and control over electrochemical doping of P3HT. At low oxidation levels (ratio of moles of electrons removed to moles of 3-hexylthiophene moieties in the electrode), the electronic conductivity (σe,ox) increases from 10(-7) S/cm to 10(-4) S/cm. At high oxidation levels, σe,ox approaches 10(-2) S/cm. When P3HT-PEO is used as a conductive binder in a positive electrode with LiFePO4 active material, P3HT is electrochemically active within the voltage window of a charge/discharge cycle. The electronic conductivity of the P3HT-PEO binder is in the 10(-4) to 10(-2) S/cm range over most of the potential window of the charge/discharge cycle. This allows for efficient electronic conduction, and observed charge/discharge capacities approach the theoretical limit of LiFePO4. However, at the end of the discharge cycle, the electronic conductivity decreases sharply to 10(-7) S/cm, which means the "conductive" binder is now electronically insulating. The ability of our conductive binder to switch between electronically conducting and insulating states in the positive electrode provides an unprecedented route for automatic overdischarge protection in rechargeable batteries.

  19. Field Effect Transistor Behavior in Electrospun Polyaniline/Polyethylene Oxide Nanofibers

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Theofylaktos, Noulle; Robinson, Daryl C.; Mueller, Carl H.; Pinto, Nicholas J.

    2004-01-01

    Novel translators and logic devices based on nanotechnology concepts are under intense development. The potential for ultra-low power circuitry makes nanotechnology attractive for applications such as digital electronics and sensors. Furthermore, the ability to form devices on flexible substrates expands the range of applications where electronic circuitry can be introduced. For NASA, nonotechndogy offers opportunities for increased onboard data processing and thus autonomous decision-making ability, ad novel sensors that detect and respond to external stimuli with few oversight requirements. The goat of this work is to demonstrate transistor behavior in polyaniline/ polyethylene oxide nanofibers, thus creating a foundation for future logic devices.

  20. The impact of four ethylene oxide-propylene oxide block copolymers on the surface tension of dispersions of soils and minerals in water

    NASA Astrophysics Data System (ADS)

    Hagenhoff, Kerstin; Dong, Jingfeng; Chowdhry, Babur; Torres, Luis; Leharne, Stephen

    A comprehensive series of aqueous solutions of four ethylene oxide-propylene oxide-ethylene oxide block copolymers (EPE) of varying concentrations have been prepared. The EPE molecules are amphiphilic with the P blocks providing the hydrophobic segment of the molecules and the E blocks providing the hydrophilic parts. The surface tension of these solutions has been measured and compared with the surface tension of dispersions of soils (a clay soil and a sandy soil) and minerals (quartz-silica sand, bentonite and kaolinite) in the same aqueous solutions. It is observed that all the block copolymers reduce the surface tension of water; the extent to which it is reduced is determined by the surface activity of the EPE block copolymer, which in turn is related to the balance between the sizes of the P and E blocks. It is further observed that the in the presence of soil the surface tension increases as a result of block copolymer adsorption to the soil/water interface. The extent of adsorption appears to be related to the texture of the soil - the clay soil used in this investigation adsorbs more block copolymer than the sandy soil. In the presence of the mineral phases the surface tension reductions are variable. With bentonite the EPE block copolymers are completely adsorbed at low EPE concentrations as shown by surface tension values that are the same as those measured for pure water. Adsorption to kaolinite is limited and once the adsorption sites have been filled the surface tension of the aqueous phase is approaches the surface tension of the same solution without the presence of bentonite. On the other hand the silica sand is a poor adsorbent. Adsorption to the mineral phases is also dependent upon the relative hydrophobicity of the block copolymer. The more hydrophobic (as inferred by the critical micelle concentration) the copolymer the less readily it is adsorbed by the mineral phases. Thus relatively hydrophobic EPE block copolymers produce a relatively

  1. Self-assembly of well-defined ferrocene triblock copolymers and their template synthesis of ordered iron oxide nanoparticles.

    PubMed

    Hardy, Christopher G; Ren, Lixia; Ma, Shuguo; Tang, Chuanbing

    2013-05-14

    Well-defined ferrocene-containing triblock copolymers were synthesized by atom transfer radical polymerization and self-assembled into highly ordered hexagonal arrays of cylinders via solvent annealing. The thin films were further used as a template and converted into highly ordered iron oxide nanoparticles (α-Fe2O3) by UV/ozonolysis and thermal pyrolysis.

  2. Chitin-incorporated poly(ethylene oxide)-based nanocomposite electrolytes for lithium batteries.

    PubMed

    Stephan, A Manuel; Kumar, T Prem; Kulandainathan, M Anbu; Lakshmi, N Angu

    2009-02-19

    Nanocomposite polymer electrolytes (NCPE), with different proportions of poly(ethylene oxide)/LiClO(4)/chitin were prepared by a hot press method. Nanochitin, a biopolymer, poly(beta-(1-->4)-N acetyl-d-glucosamine) was incorporated as a filler in poly(ethylene oxide) (PEO). The ionic conductivity of the composite polymer electrolytes was enhanced by one order upon addition of nanochitin. The lithium transference number, t(Li)(+), was increased from 0.24 to 0.51 upon chitin addition. The membranes were subjected to scanning electron microscopy, thermogravimetric-differential thermal analysis, differential scanning calorimetry, ionic conductivity, and Fourier transform infrared (FTIR) spectroscopy analysis. The free volume V(f) was probed by positron annihilation lifetime spectroscopy studies at 30 degrees C. Li/NCPE/Li symmetric cells were assembled, and the thickness of the solid electrolyte interface as a function of time was analyzed. This paper also describes FTIR spectroscopic studies of the interface between lithium metal and NCPE, which suggests that the surface chemistry of lithium electrodes in contact with NCPE is dominated by compounds with C-N-Li and C-O-Li bonding.

  3. Stability of polyethylene oxide in matrix tablets prepared by hot-melt extrusion.

    PubMed

    Crowley, Michael M; Zhang, Feng; Koleng, John J; McGinity, James W

    2002-11-01

    The thermal stability of polyethylene oxide (PEO) in sustained release tablets prepared by hot-melt extrusion was investigated. The weight average molecular weight of the polymer was studied using gel permeation chromatography. The chemical stability of PEO was found to be dependent on both the storage and processing temperature, and the molecular weight of the polymer. Storage of the polymer above its melting point significantly increased polymer degradation, and the degradation process was accelerated as the molecular weight was reduced. The thermal stability of PEO MW = 1,000,000 (PEO 1 M) in sustained release chlropheniramine maleate (CPM) tablets prepared by hot-melt extrusion was found to depend on the processing temperature and screw speed. Lower molecular weight PEO MW = 100,000 (PEO 100 K) was demonstrated to be a suitable processing aid for PEO 1 M. Incorporation of PEO 100 K reduced degradation of PEO 1 M and did not alter the release rate of CPM. Vitamin E, Vitamin E Succinate and Vitamin E TPGS were found to be suitable stabilizers for PEO, however, ascorbic acid was shown to degrade the polymer in solution. Thermal analysis demonstrated that Vitamin E Succinate and Vitamin E TPGS were dispersed at the molecular level in hot-melt extruded tablets. Solubilized Vitamin E Succinate and Vitamin E TPGS suppressed the melting point of the polyethylene oxide. Drug release rates from hot-melt extruded tablets stabilized with antioxidants were found to be dependent on the hydrophilic nature of the antioxidant.

  4. Polyethylene oxide-polytetrahydrofurane-PEDOT conducting interpenetrating polymer networks for high speed actuators

    NASA Astrophysics Data System (ADS)

    Plesse, C.; Khaldi, A.; Wang, Q.; Cattan, E.; Teyssié, D.; Chevrot, C.; Vidal, F.

    2011-12-01

    In recent years, numerous studies on electro-active polymer (EAP) actuators have been reported. One promising technology is the elaboration of electronic conducting polymer-based actuators with interpenetrating polymer network (IPNs) architecture. In this study, the synthesis and characterisation of conducting IPNs for actuator applications is described. The IPNs are synthesised from polyethylene oxide (PEO) and polytetrahydrofurane (PTHF) networks in which the conducting polymer (poly(3,4-ethylenedioxythiophene)) is incorporated. In a first step, PEO/PTHF IPNs were prepared via an 'in situ' process using poly(ethylene glycol) methacrylate and dimethacrylate and hydroxytelechelic PTHF as starting materials. The IPN mechanical properties were examined by DMA and tensile strength tests. N-ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) swollen PEO/PTHF IPNs show ionic conductivities up to 10-3 S cm-1 at 30 °C. In a second step, the conducting IPN actuators were prepared by oxidative polymerisation of 3,4-ethylenedioxithiophene (EDOT) using FeCl3 as an oxidising agent within the PEO/PTHF IPN host matrix. The frequency response performance of the bending conducting IPN actuator was then evaluated. The resulting actuator exhibits a mechanical resonance frequency of up to 125 Hz with 0.75% strain for an applied potential of ± 5 V.

  5. Atomistic simulation of CO2 solubility in poly(ethylene oxide) oligomers

    NASA Astrophysics Data System (ADS)

    Hong, Bingbing; Panagiotopoulos, Athanassios Z.

    2014-06-01

    We have performed atomistic molecular dynamics simulations coupled with thermodynamic integration to obtain the excess chemical potential and pressure-composition phase diagrams for CO2 in poly(ethylene oxide) oligomers. Poly(ethylene oxide) dimethyl ether, CH3O(CH2CH2O)nCH3 (PEO for short) is a widely applied physical solvent that forms the major organic constituent of a class of novel nanoparticle-based absorbents. Good predictions were obtained for pressure-composition-density relations for CO2 + PEO oligomers (2 ≤ n ≤ 12), using the Potoff force field for PEO [J. Chem. Phys. 136, 044514 (2012)] together with the TraPPE model for CO2 [AIChE J. 47, 1676 (2001)]. Water effects on Henry's constant of CO2 in PEO have also been investigated. Addition of modest amounts of water in PEO produces a relatively small increase in Henry's constant. Dependence of the calculated Henry's constant on the weight percentage of water falls on a temperature-dependent master curve, irrespective of PEO chain length.

  6. A study on optical absorption and constants of doped poly(ethylene oxide)

    NASA Astrophysics Data System (ADS)

    Al-Faleh, R. S.; Zihlif, A. M.

    2011-05-01

    Thin films of polymer electrolyte based on poly(ethylene oxide) doped with sodium iodide (NaI) were prepared using the solution cast method. The films obtained have average thickness of 70 μm and different NaI concentrations. Absorption and reflectance spectra of UV-radiation were studied in the wavelength range 300-800 nm. The optical results were analyzed in terms of absorption formula for non-crystalline materials. The optical energy gap and the basic optical constants, refractive index, and dielectric constants of the prepared films have been investigated and showed a clear dependence on the NaI concentration. The interpreted absorption mechanism is a direct electron transition. The observed optical energy gap for neat poly(ethylene oxide) is about 2.6 eV, and decreases to a value 2.36 eV for the film of 15 wt% NaI content. It was found that the calculated refractive index and the dielectric constants of the polymer electrolyte thin films increase with NaI content. Models were used to describe the dependences of the dielectric constant on the NaI concentration, and the refractive index on the incident photon energy.

  7. Electrical Characterization of Polyaniline/polyethylene Oxide Nanofibers for Field Effect Transistors

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; Theofylaktos, Noulie; Pinto, Nicholas J.; Robinson, Daryl C.; Miranda, Felix A.

    2002-01-01

    Nanofibers comprised of polyaniline/polyethylene oxide (PANI/PEO) are being developed for novel logic devices. We report the electrical conductivity of PANI/PEO nanofibers with diameters in the 100 to 200 nm range. We measured conductivity values of approx. 0.3 to 1.0 S/cm, which is higher than the values reported for thicker nanofibers, but less than the bulk value of PANI. The electrical measurements were performed by depositing the fibers on pre-electroded, oxidized silicon (Si) substrates. The excellent adherence of the nanofibers to the SiO2 as well as the gold (Au) electrodes may be useful in the design of future devices.

  8. Adsorption and functionality of fibrinogen on triblock copolymer-coated surfaces

    NASA Astrophysics Data System (ADS)

    O'Connor, Stephen Moss

    To assess the influence of the surface microenvironment on the adsorption and biologic activity of fibrinogen, a series of poly(ethylene oxide)/poly(propylene oxide) triblock copolymers were adsorbed to solid, hydrophobic polystyrene-divinylbenzene beads. The copolymers, which were of the form PEOsb{b}PPOsb{a}PEOsb{b}, varied in their hydrophile/lipophile balances (HLB) due only to differences in their PEO chain length (5 to 129 EO units) as the hydrophobic PPO core segment was of fixed length (56 or 69 PO units). The surface coverage of copolymers was determined first and after exposing the beads to fibrinogen or to human plasma, the total amount of protein adsorbed to their surface was measured. The functionality of fibrinogen bound to copolymer-modified beads was assessed in terms of fibrin clot formation and by the adherence of macrophages (THP-1 tumor cells). Enzymatic processing was used to probe the surface orientation of fibrinogen. The copolymers appear to adsorb in an expanded fashion, a conclusion supported by surface pressure-area isotherms of the copolymers spread at the air-water interface. As compared to copolymer-free surfaces, protein adsorption decreases by up to 90% as the PEO chain length of the copolymers increases. The copolymer coatings appear to lower fibrinogen adsorption by limiting the available surface area. On surfaces coated with the hydrophobic versions of the copolymers, the biologic assays demonstrate that fibrinogen is as reactive/coagulable as for surfaces with saturated coverages of fibrin despite that these copolymer-coated surfaces have 60% less fibrinogen adsorbed to them. When adsorbed at the same low surface concentration in the absence of copolymer, fibrinogen is not active. Enzymatic processing of bound fibrinogen suggests that the presence of the copolymers promote the adsorption of the protein in end-on fashion. It is proposed here, that when adsorbed end-on, fibrinogen is functional because its reactive sites are

  9. ZPPR-20 phase D : a cylindrical assembly of polyethylene moderated U metal reflected by beryllium oxide and polyethylene.

    SciTech Connect

    Lell, R.; Grimm, K.; McKnight, R.; Shaefer, R.; Nuclear Engineering Division; INL

    2006-09-30

    The Zero Power Physics Reactor (ZPPR) fast critical facility was built at the Argonne National Laboratory-West (ANL-W) site in Idaho in 1969 to obtain neutron physics information necessary for the design of fast breeder reactors. The ZPPR-20D Benchmark Assembly was part of a series of cores built in Assembly 20 (References 1 through 3) of the ZPPR facility to provide data for developing a nuclear power source for space applications (SP-100). The assemblies were beryllium oxide reflected and had core fuel compositions containing enriched uranium fuel, niobium and rhenium. ZPPR-20 Phase C (HEU-MET-FAST-075) was built as the reference flight configuration. Two other configurations, Phases D and E, simulated accident scenarios. Phase D modeled the water immersion scenario during a launch accident, and Phase E (SUB-HEU-MET-FAST-001) modeled the earth burial scenario during a launch accident. Two configurations were recorded for the simulated water immersion accident scenario (Phase D); the critical configuration, documented here, and the subcritical configuration (SUB-HEU-MET-MIXED-001). Experiments in Assembly 20 Phases 20A through 20F were performed in 1988. The reference water immersion configuration for the ZPPR-20D assembly was obtained as reactor loading 129 on October 7, 1988 with a fissile mass of 167.477 kg and a reactivity of -4.626 {+-} 0.044{cents} (k {approx} 0.9997). The SP-100 core was to be constructed of highly enriched uranium nitride, niobium, rhenium and depleted lithium. The core design called for two enrichment zones with niobium-1% zirconium alloy fuel cladding and core structure. Rhenium was to be used as a fuel pin liner to provide shut down in the event of water immersion and flooding. The core coolant was to be depleted lithium metal ({sup 7}Li). The core was to be surrounded radially with a niobium reactor vessel and bypass which would carry the lithium coolant to the forward inlet plenum. Immediately inside the reactor vessel was a rhenium

  10. Graphene oxide-enhanced sol-gel transition sensitivity and drug release performance of an amphiphilic copolymer-based nanocomposite

    PubMed Central

    Hu, Huawen; Wang, Xiaowen; Lee, Ka I; Ma, Kaikai; Hu, Hong; Xin, John H.

    2016-01-01

    We report the fabrication of a highly sensitive amphiphilic copolymer-based nanocomposite incorporating with graphene oxide (GO), which exhibited a low-intensity UV light-triggered sol-gel transition. Non-cytotoxicity was observed for the composite gels after the GO incorporation. Of particular interest were the microchannels that were formed spontaneously within the GO-incorporated UV-gel, which expedited sustained drug release. Therefore, the present highly UV-sensitive, non-cytotoxic amphiphilic copolymer-based composites is expected to provide enhanced photothermal therapy and chemotherapy by means of GO’s unique photothermal properties, as well as through efficient passive targeting resulting from the sol-gel transition characteristic of the copolymer-based system with improved sensitivity, which thus promises the enhanced treatment of patients with cancer and other diseases. PMID:27539298

  11. Graphene oxide-enhanced sol-gel transition sensitivity and drug release performance of an amphiphilic copolymer-based nanocomposite

    NASA Astrophysics Data System (ADS)

    Hu, Huawen; Wang, Xiaowen; Lee, Ka I.; Ma, Kaikai; Hu, Hong; Xin, John H.

    2016-08-01

    We report the fabrication of a highly sensitive amphiphilic copolymer-based nanocomposite incorporating with graphene oxide (GO), which exhibited a low-intensity UV light-triggered sol-gel transition. Non-cytotoxicity was observed for the composite gels after the GO incorporation. Of particular interest were the microchannels that were formed spontaneously within the GO-incorporated UV-gel, which expedited sustained drug release. Therefore, the present highly UV-sensitive, non-cytotoxic amphiphilic copolymer-based composites is expected to provide enhanced photothermal therapy and chemotherapy by means of GO’s unique photothermal properties, as well as through efficient passive targeting resulting from the sol-gel transition characteristic of the copolymer-based system with improved sensitivity, which thus promises the enhanced treatment of patients with cancer and other diseases.

  12. Three-dimensional block copolymer nanostructures by the solvent-annealing-induced wetting in anodic aluminum oxide templates.

    PubMed

    Chu, Chiang-Jui; Chung, Pei-Yun; Chi, Mu-Huan; Kao, Yi-Huei; Chen, Jiun-Tai

    2014-09-01

    Block copolymers have been extensively studied over the last few decades because they can self-assemble into well-ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this work, the fabrication and morphologies of three-dimensional polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanostructures confined in the nanopores of anodic aluminum oxide (AAO) templates are studied. It is discovered that the block copolymers can wet the nanopores using a novel solvent-annealing-induced nanowetting in templates (SAINT) method. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS-b-PDMS nanostructures can be controlled by changing the wetting conditions. Different solvents are used as the annealing solvent, including toluene, hexane, and a co-solvent of toluene and hexane. When the block copolymer wets the nanopores in toluene vapors, a perpendicular morphology is observed. When the block copolymer wets the nanopores in co-solvent vapors (toluene/hexane = 3:2), unusual circular and helical morphologies are obtained. These three-dimensional nanostructures can serve as naontemplates for refilling with other functional materials, such as Au, Ag, ZnO, and TiO2 .

  13. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... blended with polyethylene or with one or more olefin copolymers complying with § 177.1520 or with a mixture of polyethylene and one or more olefin copolymers, in such proportions that the ethyl acrylate... prescribed in paragraph (c)(2) of this section, when tested by the methods prescribed for polyethylene...

  14. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... percent by weight unless it is blended with polyethylene or with one or more olefin copolymers complying with § 177.1520 or with a mixture of polyethylene and one or more olefin copolymers, in such... prescribed for polyethylene in § 177.1520. (1) Specifications—(i) Infrared identification....

  15. Interaction of poloxamine block copolymers with lipid membranes: Role of copolymer structure and membrane cholesterol content.

    PubMed

    Sandez-Macho, Isabel; Casas, Matilde; Lage, Emilio V; Rial-Hermida, M Isabel; Concheiro, Angel; Alvarez-Lorenzo, Carmen

    2015-09-01

    Interactions of X-shaped poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers with cell membranes were investigated recording the π-A isotherms of monolayer systems of dipalmitoylphosphatidylcholine (DPPC):cholesterol 100:0; 80:20 and 60:40 mol ratio and evaluating the capability of the copolymers to trigger haemolysis or to protect from haemolytic agents. Four varieties of poloxamine (Tetronic 904, 908, 1107 and 1307) were chosen in order to cover a wide range of EO and PO units contents and molecular weights, and compared to a variety of poloxamer (Pluronic P85). The π-A isotherms revealed that the greater the content in cholesterol, the stronger the interaction of the block copolymers with the lipids monolayer. The interactions were particularly relevant at low pressures and low lipid proportions, mimicking the conditions of damaged membranes. Relatively hydrophobic copolymers bearing short PEO blocks (e.g., T904 and P85) intercalated among the lipids expanding the surface area (ΔGexc) but not effectively sealing the pores. These varieties showed haemolytic behavior. Oppositely, highly hydrophilic copolymers bearing long PEO blocks (e.g., T908, T1107 and T1307) caused membrane contraction and outer leaflet sealing due to strong interactions of PEO with cholesterol and diamine core with phospholipids. These later varieties were not haemolytic and exerted a certain protective effect against spontaneous haemolysis for both intact erythrocytes and cholesterol-depleted erythrocytes.

  16. New Aptes Cross-linked Polymers from Poly(ethylene oxide)s and Cyanuric Chloride for Lithium Batteries

    NASA Technical Reports Server (NTRS)

    Tigelaar, Dean M.; Meador, Mary Ann B.; Kinder, James D.; Bennett, William R.

    2005-01-01

    A new series of polymer electrolytes for use as membranes for lithium batteries are described. Electrolytes were made by polymerization between cyanuric chloride and diamino-terminated poly(ethylene oxide)s, followed by cross-linking via a sol-gel process. Thermal analysis and lithium conductivity of freestanding polymer films were studied. The effects of several variables on conductivity were investigated, such as length of backbone PEO chain, length of branching PEO chain, extent of branching, extent of cross-linking, salt content, and salt counterion. Polymer films with the highest percentage of PEO were found to be the most conductive, with a maximum lithium conductivity of 3.9 x 10(exp -5) S/cm at 25 C. Addition of plasticizer to the dry polymers increased conductivity by an order of magnitude.

  17. Characterization of Lithium Polysulfide Salts in Homopolymers and Block Copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Dunyang; Wujcik, Kevin; Balsara, Nitash

    Ion-conducting polymers are important for solid-state batteries due to the promise of better safety and the potential to produce higher energy density batteries. Nanostructured block copolymer electrolytes can provide high ionic conductivity and mechanical strength through microphase separation. One of the potential use of block copolymer electrolytes is in lithium-sulfur batteries, a system that has high theoretical energy density wherein the reduction of sulfur leads to the formation of lithium polysulfide intermediates. In this study we investigate the effect of block copolymer morphology on the speciation and transport properties of the polysulfides. The morphology and conductivities of polystyrene-b-poly(ethylene oxide) (SEO) containing lithium polysulfides were studies using small-angle X-ray scattering and ac impedance spectroscopy. UV-vis spectroscopy is being used to determine nature of the polysulfide species in poly(ethylene oxide) and SEO. Department of Energy, Soft Matter Electron Microscopy Program and Battery Materials Research Program.

  18. Poly(ethylene oxide)-co-poly(propylene oxide)-based gel electrolyte with high ionic conductivity and mechanical integrity for lithium-ion batteries.

    PubMed

    Wang, Shih-Hong; Hou, Sheng-Shu; Kuo, Ping-Lin; Teng, Hsisheng

    2013-09-11

    Using gel polymer electrolytes (GPEs) for lithium-ion batteries usually encounters the drawback of poor mechanical integrity of the GPEs. This study demonstrates the outstanding performance of a GPE consisting of a commercial membrane (Celgard) incorporated with a poly(ethylene oxide)-co-poly(propylene oxide) copolymer (P(EO-co-PO)) swelled by a liquid electrolyte (LE) of 1 M LiPF6 in carbonate solvents. The proposed GPE stably holds LE with an amount that is three times that of the Celgard-P(EO-co-PO) composite. This GPE has a higher ionic conductivity (2.8×10(-3) and 5.1×10(-4) S cm(-1) at 30 and -20 °C, respectively) and a wider electrochemical voltage range (5.1 V) than the LE-swelled Celgard because of the strong ion-solvation power of P(EO-co-PO). The active ion-solvation role of P(EO-co-PO) also suppresses the formation of the solid-electrolyte interphase layer. When assembling the GPE in a Li/LiFePO4 battery, the P(EO-co-PO) network hinders anionic transport, producing a high Li+ transference number of 0.5 and decreased the polarization overpotential. The Li/GPE/LiFePO4 battery delivers a discharge capacity of 156-135 mAh g(-1) between 0.1 and 1 C-rates, which is approximately 5% higher than that of the Li/LE/LiFePO4 battery. The IR drop of the Li/GPE/LiFePO4 battery was 44% smaller than that of the Li/LE/LiFePO4. The Li/GPE/LiFePO4 battery is more stable, with only a 1.2% capacity decay for 150 galvanostatic charge-discharge cycles. The advantages of the proposed GPE are its high stability, conductivity, Li+ transference number, and mechanical integrity, which allow for the assembly of GPE-based batteries readily scalable to industrial levels.

  19. Accumulation of magnetic iron oxide nanoparticles coated with variably sized polyethylene glycol in murine tumors.

    PubMed

    Larsen, Esben Kjær Unmack; Nielsen, Thomas; Wittenborn, Thomas; Rydtoft, Louise Munk; Lokanathan, Arcot R; Hansen, Line; Østergaard, Leif; Kingshott, Peter; Howard, Kenneth A; Besenbacher, Flemming; Nielsen, Niels Chr; Kjems, Jørgen

    2012-04-07

    Iron oxide nanoparticles have found widespread applications in different areas including cell separation, drug delivery and as contrast agents. Due to water insolubility and stability issues, nanoparticles utilized for biological applications require coatings such as the commonly employed polyethylene glycol (PEG). Despite its frequent use, the influence of PEG coatings on the physicochemical and biological properties of iron nanoparticles has hitherto not been studied in detail. To address this, we studied the effect of 333-20,000 Da PEG coatings that resulted in larger hydrodynamic size, lower surface charge, longer circulation half-life, and lower uptake in macrophage cells when the particles were coated with high molecular weight (M(w)) PEG molecules. By use of magnetic resonance imaging, we show coating-dependent in vivo uptake in murine tumors with an optimal coating M(w) of 10,000 Da.

  20. Friction and wear of polyethylene oxide polymer having a range of molecular weights

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Sliding friction and wear experiments were conducted at light loads (25 to 250 g) with various molecular weights of the polyethylene oxide polymer sliding on itself and iron. Results of the experimental investigation indicate that: (1) the coefficient of friction for the polymer decreases with increasing molecular weight; (2) friction coefficient is higher for the polymer sliding on itself than it is for the polymer sliding on iron; (3) at sufficiently high loads localized surface melting occurs and the friction coefficient is the same for the polymer sliding on itself and iron; (4) fracture cracks develop in the sliding wear track at higher but not lower sliding velocities, reflecting a strain rate sensitivity to crack initiation, and (5) the friction coefficient for the polymer sliding on iron increases with the formation of a polymer film on the iron surface.

  1. Field Effect Transistor Behavior in Electrospun Polyaniline/Polyethylene Oxide Nanofibers

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Theofylaktos, Noulie; Mueller, Carl H.; Pinto, Nicholas J.

    2004-01-01

    Novel transistors and logic devices based on nanotechnology concepts are under intense development. The potential for ultra-low-power circuitry makes nanotechnology attractive for applications such as digital electronics and sensors. For NASA applications, nanotechnology offers tremendous opportunities for increased onboard data processing, and thus autonomous decision-making ability, and novel sensors that detect and respond to environmental stimuli with little oversight requirements. Polyaniline (PANi) is an intriguing material because its electrical conductivity can be changed from insulating to metallic by varying the doping levels and conformations of the polymer chain, and when combined with polyethylene oxide (PEO), can be formed into nanofibers with diameters ranging from approximately 50 to 500 nm (depending on the deposition conditions). The initial goal of this work was to demonstrate transistor behavior in these nanofibers, thus creating a foundation for future logic devices.

  2. Conformation and hydration of surface grafted and free polyethylene oxide chains in solutions

    NASA Astrophysics Data System (ADS)

    Dahal, Udaya; Wang, Zilu; Dormidontova, Elena

    Due to the wide application of polyethylene oxide (PEO), ranging from biomedicine to fuel cells, it is one of the most studied polymers in the scientific world. In order to elucidate detailed molecular-level insights on the impact of surface grafting on PEO conformation, we performed atomistic molecular dynamics simulations of PEO chains in solution and grafted to a flat gold surface in different solvents. We examined the hydration as well as conformation of the free chain compared to the grafted polymer in pure water and mixed solvents. We find that grafted chains are stiffer and have a stronger tendency to form helical structures in isobutyric acid or mixture of isobutyric acid and water solution than the free chains in corresponding solutions. For grafted chains exposed to pure water the random coil conformation is retained at low grafting density, but becomes stretched and more dehydrated as the grafting density or temperature increases. This research is supported by NSF (DMR-1410928).

  3. Gelation, swelling and water vapor permeability behavior of radiation synthesized poly(ethylene oxide) hydrogels

    NASA Astrophysics Data System (ADS)

    Savaş, Hülya; Güven, Olgun

    2002-04-01

    In this study, gamma ray induced gelation of aqueous solutions of poly(ethylene oxide), (PEO) with 73.300 Da average molecular weight has been studied. Percent of conversion of polymer into gel as well as swelling behavior were investigated gravimetrically. The effect of the dose rate on these properties was studied. Within the dose rate range studied, it is observed that low dose rate irradiation favors chain scission and although the dominant effect is still crosslinking, %gelation at a given dose decreases. Water vapor permeability (Wvp) of PEO hydrogels has been studied with regard to crosslink density changes and temperature. The water vapor permeability of hydrogels obtained at high dose rate was found to be lower than those obtained at low dose rate which was related to higher crosslink density achieved under higher dose rate irradiations.

  4. In situ preparation of poly(ethylene oxide)-SiO 2 composite polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Lee, J. Y.; Hong, L.

    Amorphous poly(ethylene oxide) (PEO)-SiO 2 composites are prepared by in situ reactions that involve the simultaneous formation of the polymer network and inorganic nanoparticles. The polymer matrix is formed by ultraviolet irradiation of a PEO macromer, and silica is produced in situ by the sol-gel method. The PEO-SiO 2 composite mixed with LiBF 4 is used as a lithium-ion conducting solid electrolyte and electrochemical transport properties such as ionic conductivity and Li + transference number are measured. A significant increase in the Li + transference number, up to 0.56, is found together with a slight decrease in the ionic conductivity. The results are interpreted in terms of interactions between the surface OH groups of the inorganic particles, the cations, the anions, and the ether oxygen atoms on the PEO backbone.

  5. Collective motion in Poly(ethylene oxide)/poly(methylmethacrylate) blends

    SciTech Connect

    Farago, Bela; Chen Chunxia; Maranas, Janna K.; Kamath, Sudesh; Colby, Ralph H.; Pasquale, Anthony J.; Long, Timothy E.

    2005-09-01

    We present neutron spin echo and structural measurements on a perdeutereted miscible polymer blend: poly(ethylene oxide)[PEO]/poly(methyl methacrylate)[PMMA], characterized by a large difference in component glass transition temperatures and minimal interactions. The measurements cover the q range 0.35 to 1.66 A{sup -1} and the temperature range T{sub g}-75 to T{sub g}+89 K, where T{sub g} is the blend glass transition. The spectra, obtained directly in the time domain, are very broad with stretching parameters {beta}{approx}0.30. The relaxation times vary considerably over the spatial range considered however at none of the q values do we see two distinct relaxation times. At small spatial scales relaxations are still detectable at temperatures far below T{sub g}. The temperature dependence of these relaxation times strongly resembles the {beta}-relaxation process observed in pure PMMA.

  6. Block copolymer blend phase behavior: Binary diblock blends and amphiphilic block copolymer/epoxy mixtures

    NASA Astrophysics Data System (ADS)

    Lipic, Paul Martin

    The phase behavior of block copolymers and block copolymer blends has provided an extensive amount of exciting research and industrial applications for over thirty years. However, the unique nanoscale morphologies of microphase separated block copolymer systems is still not completely understood. This thesis examines the phase behavior of diblock copolymers and binary diblock copolymer blends in the strong segregation limit (SSL), and blends of an amphiphilic diblock copolymer with an epoxy resin. Studies of high molecular weight (˜84,000 g/mole) poly(ethylene)-poly(ethyl ethylene) (PE-PEE) diblock copolymers probed the ability of block copolymers to reach equilibrium in the SSL. Samples of pure diblocks or binary diblock blends prepared using different preparation techniques (solvent casting or precipitation) had different phase behaviors, as identified with transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS), confirming non-equilibrium phase behavior. This non-equilibrium behavior was metastable, and these results identify the caution that should be used when claiming equilibrium phase behavior in the SSL. Blends of an amphiphilic diblock copolymer, poly(ethylene oxide)-poly(ethylene-alt-propylene) (PEO-PEP) with a polymerizable epoxy resin selectively miscible with PEO, poly(Bisphenol-A-co-epichlorohydrin), supported theoretical calculations and increased the understanding of block copolymer/homopolymer blends. These blends formed different ordered structures (lamellae, bicontinuous cubic gyroid, hexagonally packed cylinders, cubic and hexagonally packed spheres) as well as a disordered spherical micellar structure, identified with SAXS and rheological measurements. Addition of hardener, methylene dianiline, to the system resulted in cross-linking of the epoxy resin and formation of a thermoset material. Macrophase separation between the epoxy and block copolymer did not occur, but local expulsion of the PEO from the epoxy was

  7. Lithium Metal-Copper Vanadium Oxide Battery with a Block Copolymer Electrolyte

    SciTech Connect

    Devaux, Didier; Wang, Xiaoya; Thelen, Jacob L.; Parkinson, Dilworth Y.; Cabana, Jordi; Wang, Feng; Balsara, Nitash P.

    2016-09-08

    Lithium (Li) batteries comprising multivalent positive active materials such as copper vanadium oxide have high theoretical capacity. These batteries with a conventional liquid electrolyte exhibit limited cycle life because of copper dissolution into the electrolyte. In this paper, we report here on the characterization of solid-state Li metal batteries with a positive electrode based on α-Cu6.9V6O18.9 (α-CuVO3). We replaced the liquid electrolyte by a nanostructured solid block copolymer electrolyte comprising of a mixture of polystyrene-b-poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. In situ X-ray diffraction was used to follow the Li insertion/de-insertion mechanism into the α-CuVO3 host material and its reversibility. In situ X-ray scattering revealed that the multistep electrochemical reactions involved are similar in the presence of liquid or solid electrolyte. The capacity fade of the solid-state batteries is less rapid than that of α-CuVO3–Li metal batteries with a conventional liquid electrolyte. Hard X-ray microtomography revealed that upon cycling, voids and Cu-rich agglomerates were formed at the interface between the Li metal and the SEO electrolyte. Finally, the void volume and the volume occupied by the Cu-rich agglomerates were independent of C-rate and cycle number.

  8. Lithium Metal-Copper Vanadium Oxide Battery with a Block Copolymer Electrolyte

    DOE PAGES

    Devaux, Didier; Wang, Xiaoya; Thelen, Jacob L.; ...

    2016-09-08

    Lithium (Li) batteries comprising multivalent positive active materials such as copper vanadium oxide have high theoretical capacity. These batteries with a conventional liquid electrolyte exhibit limited cycle life because of copper dissolution into the electrolyte. In this paper, we report here on the characterization of solid-state Li metal batteries with a positive electrode based on α-Cu6.9V6O18.9 (α-CuVO3). We replaced the liquid electrolyte by a nanostructured solid block copolymer electrolyte comprising of a mixture of polystyrene-b-poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. In situ X-ray diffraction was used to follow the Li insertion/de-insertion mechanism into the α-CuVO3 host material andmore » its reversibility. In situ X-ray scattering revealed that the multistep electrochemical reactions involved are similar in the presence of liquid or solid electrolyte. The capacity fade of the solid-state batteries is less rapid than that of α-CuVO3–Li metal batteries with a conventional liquid electrolyte. Hard X-ray microtomography revealed that upon cycling, voids and Cu-rich agglomerates were formed at the interface between the Li metal and the SEO electrolyte. Finally, the void volume and the volume occupied by the Cu-rich agglomerates were independent of C-rate and cycle number.« less

  9. The Role of Hard Segment Content on the Molecular Dynamics of Poly(tetramethylene oxide)-Based Polyurethane Copolymers

    DTIC Science & Technology

    2011-01-01

    Hard Segment Content on the Molecular Dynamics of Poly(tetramethylene oxide)-Based Polyurethane Copolymers Alicia M. Castagna,† Daniel Fragiadakis... Hernandez et al.11 Their key microstructural characteristics are summarized in the initial portion of the Results and Discussion section. Although some...temperature DSC endo- therm by Hernandez et al. (indicated by the dotted lines in Figure 5b).11 This temperature shift is what is expected for higher

  10. Complement activation on poly(ethylene oxide)-like RFGD-deposited surfaces

    PubMed Central

    Szott, Luisa Mayorga; Stein, M. Jeanette; Ratner, Buddy D.; Horbett, Thomas A.

    2010-01-01

    Non-specific protein adsorption, particularly fibrinogen (Fg), is thought to be an initiating step in the foreign body response (FBR) to biomaterials by promoting phagocyte attachment. In previous studies, we therefore prepared radio frequency glow discharge (RFGD) polyethylene oxide (PEO)-like tetraglyme coatings (CH3O(CH2CH2O)4CH3) adsorbing less than 10 ng/cm2 Fg and showed that they had the expected low monocyte adhesion in vitro. However, when these were implanted in vivo, many adherent inflammatory cells and a fibrous capsule were found, suggesting the role of alternative proteins, such as activated complement proteins, in the FBR to these materials. We therefore investigated complement interactions with the tetraglyme surfaces. First, because of its well known role in complement C3 activation, we measured the hydroxyl group (-OH) content of tetraglyme, but found it to be very low. Second, we measured C3 adsorption to tetraglyme from plasma. Low amounts of C3 adsorbed on tetraglyme, though it displayed higher binding strength than the control surfaces. Finally, complement activation was determined by measuring C3a and SC5b-9 levels in serum after incubating with tetraglyme, as well as other surfaces that served as positive and negative controls, namely poly(vinyl alcohol) hydrogels, Silastic sheeting, and poly(ethylene glycol) self-assembled monolayers with different end groups. Despite displaying low hydroxyl group concentration, relatively high C3a and SC5b-9 levels were found in serum exposed to tetraglyme, similar to the values due to our positive control, PVA. Our results support the conclusion that complement activation by tetraglyme is a possible mechanism involved in the FBR to these biomaterials. PMID:21105163

  11. Controlling block copolymer phase behavior using ionic surfactant

    NASA Astrophysics Data System (ADS)

    Ray, D.; Aswal, V. K.

    2016-05-01

    The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO26PO39EO26)] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle-surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

  12. Confinement effects on the crystallization of poly(ethylene oxide) nanotubes.

    PubMed

    Maiz, Jon; Martin, Jaime; Mijangos, Carmen

    2012-08-21

    In this work, we show the effects of nanoconfinement on the crystallization of poly(ethylene oxide) (PEO) nanotubes embedded in anodized aluminum oxide (AAO) templates. The morphological characteristics of the hollow 1D PEO nanostructures were evaluated by scanning electron microscopy (SEM). The crystallization of the PEO nanostructures and bulk was studied with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The crystallization of PEO nanotubes studied by DSC is strongly influenced by the confinement showing a strong reduction in the crystallization temperature of the polymer. X-ray diffraction (XRD) experiments confirmed the isothermal crystallization results obtained by DSC, and studies carried out at low temperatures showed the absence of crystallites oriented with the extended chains perpendicular to the pore wall within the PEO nanotubes, which has been shown to be the typical crystal orientation for one-dimensional polymer nanostructures. In contrast, only planes oriented 33, 45, and 90° with respect to the plane (120) are arranged parallel to the pore's main axis, indicating preferential crystal growth in the direction of the radial component. Calculations based on classical nucleation theory suggest that heterogeneous nucleation prevails in the bulk PEO whereas for the PEO nanotubes a surface nucleation mechanism is more consistent with the obtained results.

  13. Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode.

    PubMed

    Bejankiwar, Rajesh S; Basu, Abir; Cementi, Max

    2004-01-01

    Electrochemical oxidation of polyethylene glycol (PEG) in an acidic (pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified (PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon (TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.

  14. Low-cost flexible supercapacitors based on laser reduced graphene oxide supported on polyethylene terephthalate substrate

    NASA Astrophysics Data System (ADS)

    Ghoniem, Engy; Mori, Shinsuke; Abdel-Moniem, Ahmed

    2016-08-01

    A controlled high powered CO2 laser system is used to reduce and pattern graphene oxide (GO) film supported onto a flexible polyethylene terephthalate (PET) substrate. The laser reduced graphene oxide (rGO) film is characterized and evaluated electrochemically in the absence and presence of an overlying anodicaly deposited thin film of pseuodcapactive MnO2 as electrodes for supercapacitor applications using aqueous electrolyte. The laser treatment of the GO film leads to an overlapped structure of defective multi-layer rGO sheets with an electrical conductivity of 273 S m-1. The rGO and MnO2/rGO electrodes exhibit specific capacitance in the range of 82-107 and 172-368 Fg-1 at applied current range of 0.1-1.0 mA cm-2 and retain 98 and 95% of their initial capacitances after 2000 cycles at a current density of 1.0 mA cm-2, respectively. Also, the rGO is assigned as an electrode material for flexible conventionally stacked and interdigitated in-plane supercapacitor structures using gel electrolyte. Three electrode architectures of 2, 4, and 6 sub-electrodes are studied for the interdigital in-plane design. The device with interdigital 6 sub-electrodes architecture I-PS(6) delivers power density of 537.1 Wcm-3 and an energy density of 0.45 mWh cm-3.

  15. Reactive block copolymer vesicles with an epoxy wall.

    PubMed

    Zhu, Hui; Liu, Qingchun; Chen, Yongming

    2007-01-16

    Recently, block copolymer vesicles have attracted considerable attention because of their properties in encapsulation and release. To explore their applications in biorelated fields, functionalization of the polymer vesicle is necessary. Herein, a reactive unilamellar vesicle is reported by self-assembly of poly(ethylene oxide)-block-poly(glycidyl methacrylate) copolymer (PEO-b-PGMA) in solution. When water was added into the PEO-b-PGMA solution in THF, unilamellar vesicles were produced. If hydrophobic primary amine additives, such as hexamethylenediamine (HDA) and dodecylamine (DA), were introduced during block copolymer assembling, the vesicular morphology remained unchanged; instead, the amines reacted with the epoxys and the vesicles were fixed by cross-linking. Furthermore, when 3-aminopropyl trimethoxysilane (APS) was applied, the organic/inorganic hybrid vesicles were obtained, which were stable against the solvent change. Therefore, this research not only supplies a new way to fix the vesicular morphology but also a reactive vesicle scaffold for introducing functional species.

  16. Graphene oxide functionalized with silver@silica-polyethylene glycol hybrid nanoparticles for direct electrochemical detection of quercetin.

    PubMed

    Veerapandian, Murugan; Seo, Yeong-Tai; Yun, Kyusik; Lee, Min-Ho

    2014-08-15

    A direct electrochemical detection of quercetin based on functionalized graphene oxide modified on gold-printed circuit board chip was demonstrated in this study. Functionalized graphene oxide materials are prepared by the covalent reaction of graphene oxide with silver@silica-polyethylene glycol nanoparticles (~12.35nm). Functionalized graphene oxide electrode shows a well-defined voltammetric response in phosphate buffered saline and catalyzes the oxidation of quercetin to quinone without the need of an enzyme. Significantly, the functionalized graphene oxide modified electrode exhibited a higher sensitivity than pristine gold-printed circuit board and graphene oxide electrodes, a wide concentration range of 7.5 to 1040nM and detection limit of 3.57nM. Developed biosensor platform is selective toward quercetin in the presence of an interferent molecule.

  17. Study of Low Molecular Weight Impurities in Pluronic Triblock Copolymers using MALDI, Interaction Chromatography, and NMR

    NASA Astrophysics Data System (ADS)

    Helming, Z.; Zagorevski, D.; Ryu, C. Y.

    2014-03-01

    Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers are a group of commercial macromolecular amphiphilic surfactants that have been widely studied for their applications in polymer-based nanotechnology and drug-delivery. It has been well-established that the synthesis of commercial Pluronic triblocks results in low molecular weight ``impurities,'' which are generally disregarded in the applications and study of these polymers. These species have been shown to have significant effects on the rheological properties of the material, as well as altering the supramolecular ``micellar'' structures for which the polymers are most often used. We have isolated the impurities from the bulk Pluronic triblock using Interaction Chromatography (IC) techniques, and subjected them to analysis by H1 NMR and MALDI (Matrix-Assisted Laser Desorption Ionization) Mass Spectrometry to identify relative block composition and molecular weight information. We report significant evidence of at least two polymeric components: a low-molecular-weight homopolymer of poly(ethylene oxide) and a ``blocky'' copolymer of both poly(ethylene oxide) and poly(propylene oxide). This has significant implications, not only for the applied usage of Pluronic triblock copolymers, but for the general scientific acceptance of the impurities and their effects on Pluronic micelle and hydrogel formation.

  18. Synergism of Water Shock and a Biocompatible Block Copolymer Potentiates the Antibacterial Activity of Graphene Oxide.

    PubMed

    Karahan, H Enis; Wei, Li; Goh, Kunli; Wiraja, Christian; Liu, Zhe; Xu, Chenjie; Jiang, Rongrong; Wei, Jun; Chen, Yuan

    2016-02-17

    Graphene oxide (GO) is promising in the fight against pathogenic bacteria. However, the antibacterial activity of pristine GO is relatively low and concern over human cytotoxicity further limits its potential. This study demonstrates a general approach to address both issues. The developed approach synergistically combines the water shock treatment (i.e., a sudden decrease in environmental salinity) and the use of a biocompatible block copolymer (Pluronic F-127) as a synergist co-agent. Hypoosmotic stress induced by water shock makes gram-negative pathogens more susceptible to GO. Pluronic forms highly stable nanoassemblies with GO (Pluronic-GO) that can populate around bacterial envelopes favoring the interactions between GO and bacteria. The antibacterial activity of GO at a low concentration (50 μg mL(-1) ) increases from <30% to virtually complete killing (>99%) when complemented with water shock and Pluronic (5 mg mL(-1) ) at ≈2-2.5 h of exposure. Results suggest that the enhanced dispersion of GO and the osmotic pressure generated on bacterial envelopes by polymers together potentiate GO. Pluronic also significantly suppresses the toxicity of GO toward human fibroblast cells. Fundamentally, the results highlight the crucial role of physicochemical milieu in the antibacterial activity of GO. The demonstrated strategy has potentials for daily-life bacterial disinfection applications, as hypotonic Pluronic-GO mixture is both safe and effective.

  19. Anomalous Micellization of Pluronic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Leonardi, Amanda; Ryu, Chang Y.

    2014-03-01

    Poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, commercially known as Pluronics, are a unique family of amphiphilic triblock polymers, which self-assemble into micelles in aqueous solution. These copolymers have shown promise in therapeutic, biomedical, cosmetic, and nanotech applications. As-received samples of Pluronics contain low molecular weight impurities (introduced during the manufacturing and processing), that are ignored in most applications. It has been observed, however, that in semi-dilute aqueous solutions, at concentrations above 1 wt%, the temperature dependent micellization behavior of the Pluronics is altered. Anomalous behavior includes a shift of the critical micellization temperature and formation of large aggregates at intermediate temperatures before stable sized micelles form. We attribute this behavior to the low molecular weight impurities that are inherent to the Pluronics which interfere with the micellization process. Through the use of Dynamic Light Scattering and HPLC, we compared the anomalous behavior of different Pluronics of different impurity levels to their purified counterparts.

  20. Fabrication and anti-fouling properties of photochemically and thermally immobilized poly(ethylene oxide) and low molecular weight poly(ethylene glycol) thin films.

    PubMed

    Wang, Hui; Ren, Jin; Hlaing, Aye; Yan, Mingdi

    2011-02-01

    Poly(ethylene oxide) (PEO) and low molecular weight poly(ethylene glycol) (PEG) were covalently immobilized on silicon wafers and gold films by way of the CH insertion reaction of perfluorophenyl azides (PFPAs) by either photolysis or thermolysis. The immobilization does not require chemical derivatization of PEO or PEG, and polymers of different molecular weights were successfully attached to the substrate to give uniform films. Microarrays were also generated by printing polymer solutions on PFPA-functionalized wafer or Au slides followed by light activation. For low molecular weight PEG, the immobilization was highly dependent on the quality of the film deposited on the substrate. While the spin-coated and printed PEG showed poor immobilization efficiency, thermal treatment of the PEG melt on PFPA-functionalized surfaces resulted in excellent film quality, giving, for example, a grafting density of 9.2×10(-4)Å(-2) and an average distance between grafted chains of 33Å for PEG 20,000. The anti-fouling property of the films was evaluated by fluorescence microscopy and surface plasmon resonance imaging (SPRi). Low protein adsorption was observed on thermally-immobilized PEG whereas the photoimmobilized PEG showed increased protein adsorption. In addition, protein arrays were created using polystyrene (PS) and PEG based on the differential protein adsorption of the two polymers.

  1. Radical-cured block copolymer-modified thermosets

    SciTech Connect

    Redline, Erica M.; Francis, Lorraine F.; Bates, Frank S.

    2013-01-10

    Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP-PEO. The diblock copolymers self-assembled into well-dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer-modified epoxies, and an explanation is proposed.

  2. Biodegradable block copolymers as injectable drug-delivery systems

    NASA Astrophysics Data System (ADS)

    Jeong, Byeongmoon; Bae, You Han; Lee, Doo Sung; Kim, Sung Wan

    1997-08-01

    Polymers that display a physicochemical response to stimuli are widely explored as potential drug-delivery systems. Stimuli studied to date include chemical substances and changes in temperature, pH and electric field. Homopolymers or copolymers of N-isopropylacrylamide, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (known as poloxamers) are typical examples of thermosensitive polymers, but their use in drug delivery is problematic because they are toxic and non-biodegradable. Biodegradable polymers used for drug delivery to date have mostly been in the form of injectable microspheres or implant systems, which require complicated fabrication processes using organic solvents. Such systems have the disadvantage that the use of organic solvents can cause denaturation when protein drugs are to be encapsulated. Furthermore, the solid form requires surgical insertion, which often results in tissue irritation and damage. Here we report the synthesis of a thermosensitive, biodegradable hydrogel consisting of blocks of poly(ethylene oxide) and poly(L-lactic acid). Aqueous solutions of these copolymers exhibit temperature-dependent reversible gel-sol transitions. The hydrogel can be loaded with bioactive molecules in an aqueous phase at an elevated temperature (around 45 °C), where they form a sol. In this form, the polymer is injectable. On subcutaneous injection and subsequent rapid cooling to body temperature, the loaded copolymer forms a gel that can act as a sustained-release matrix for drugs.

  3. On the interactions between poly(ethylene oxide) and graphite oxide: A comparative study by different computational methods

    NASA Astrophysics Data System (ADS)

    Garcia-Yoldi, I.; Álvarez, F.; Colmenero, J.

    2013-03-01

    The aim of this work is to investigate polymer...substrate interactions for a polymer nanocomposite material: poly(ethylene oxide) (PEO) confined in graphite oxide (GO). Six discrete and simplified models (one for PEO and five for GO) have been chosen in order to reproduce the most likely PEO...GO interactions. Twelve potential interaction energy curves have been built using the models and curve minima have been optimized using the 2nd order Møller-Plesset perturbation theory (MP2)/6-31+G(d) method. The intermolecular interactions have been analyzed in terms of distances, stabilities, and bond critical points properties revealing several dispersion assisted π-interactions and the most stable hydrogen bond interaction between the hydrogen of the GO hydroxyl groups and the oxygen of the PEO. MP2 results have been compared with five density functionals developed by Truhlar and Zhao (M05, M05-2X, M05-2X, M06-HF, and M06-L).

  4. Polyion complex micelle MRI contrast agents from poly(ethylene glycol)-b-poly(l-lysine) block copolymers having Gd-DOTA; preparations and their control of T(1)-relaxivities and blood circulation characteristics.

    PubMed

    Shiraishi, Kouichi; Kawano, Kumi; Maitani, Yoshie; Yokoyama, Masayuki

    2010-12-01

    The current study synthesized macromolecular magnetic resonance imaging (MRI) contrast agents constituted of the poly(ethylene glycol)-b-poly(L-lysine) block copolymer (PEG-P(Lys)). A chelate group, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), was attached to the primary amino group of the block copolymer in desired contents. Gd-DOTA-based macromolecular contrast agents were prepared from PEG-P(Lys) having DOTA (PEG-P(Lys-DOTA) and Gd(III) ions. All of the PEG-P(Lys) block copolymers having gadolinium ions (PEG-P(Lys-DOTA-Gd)) showed higher T(1) relaxivity (per gadolinium), r(1)=5.6-7.3mM(-1)s(-1), than that of a low-molecular-weight gadolinium-chelate, diethylenetriaminepentaacetic acid-gadolinium(III) (Gd-DTPA) at 9.4T. The study prepared the polyion complex (PIC) micelles from the amino groups of the lysine units and an oppositely charged polyanion, poly(methacrylic acid) or dextran sulfate, in an aqueous medium. In contrast, the fully DOTA-attached PEG-P(Lys-DOTA-Gd) formed a PIC with a polycation. Compared with partially DOTA-attached cationic PEG-P(Lys-DOTA-Gd), this PIC micelle yielded a forty percent decrease of r(1). This r(1) decrease was considered to result from a change in the accessibility of water molecules to gadolinium ions in the micelles' inner core. The r(1) was decreased upon formation of the PIC micelle, and this change proved that our concept worked in vitro. Blood-circulation characteristics of PIC micelles were controlled by means of changing the molecular weight of the counter anion. The PIC micelles accumulated in tumor tissues, and MRI study showed T1W image of axial slice of tumor area was significantly enhanced at 24h after the injection.

  5. Isothermal Crystallization of Poly(ethylene oxide) / Single Walled Carbon Nanotube Nanocomposites

    NASA Astrophysics Data System (ADS)

    Lorenzo, Arnaldo; Chatterjee, Tirtha; Krishnamoorti, Ramanan

    2011-03-01

    The isothermal crystallization behavior of poly(ethylene oxide)/single walled carbon nanotubes (PEO/SWNT) nanocomposites were studied with a focus on the overall crystallization kinetics and the morphological evolution of PEO using differential scanning calorimetry and in-situ small angle x-ray scattering measurements, respectively. The overall crystallization process of the PEO was strongly affected by lithium dodecyl sulfate (LDS) stabilized carbon nanotubes. Further, analysis of the overall crystallization kinetics showed that the PEO chains were topologically constrained by the presence of LDS with an increased energy barrier associated with nucleation and crystal growth, and the nanotubes further act as a barrier to chain transport or enhance the LDS action on the PEO chains. The energy penalty and diffusional barrier to chain transport in the nanocomposites disrupt the PEO crystal helical conformation. This destabilization leads to formation of thinner crystal lamellae and suggests that the crystallization kinetics is primarily controlled by the growth process. This study is particularly interesting considering the suppression of the PEO crystallinity in presence of small amounts of Lithium ion based surfactant and carbon nanotubes.

  6. AC and DC electrospinning of hydroxypropylmethylcellulose with polyethylene oxides as secondary polymer for improved drug dissolution.

    PubMed

    Balogh, Attila; Farkas, Balázs; Verreck, Geert; Mensch, Jürgen; Borbás, Enikő; Nagy, Brigitta; Marosi, György; Nagy, Zsombor Kristóf

    2016-05-30

    Alternating current electrospinning (ACES) capable to reach multiple times higher specific productivities than widely used direct current electrospinning (DCES) was investigated and compared with DCES to prepare drug-loaded formulations based on one of the most widespread polymeric matrix used for commercialized pharmaceutical solid dispersions, hydroxypropylmethylcellulose 2910 (HPMC). In order to improve the insufficient spinnability of HPMC (both with ACES and DCES) polyethylene oxide (PEO) as secondary polymer with intense ACES activity was introduced into the electrospinning solution. Different grades of this polymer used at as low concentrations in the fibers as 0.1% or less enabled the production of high quality HPMC-based fibrous mats without altering its physicochemical properties remarkably. Increasing concentrations of higher molecular weight PEOs led to the thickening of fibers from submicronic diameters to several microns of thickness. ACES fibers loaded with the poorly water-soluble model drug spironolactone were several times thinner than drug-loaded fibers prepared with DCES in spite of the higher feeding rates applied. The amorphous HPMC-based fibers with large surface area enhanced the dissolution of spironolactone significantly, the presence of small amounts of PEO did not affect the dissolution rate. The presented results confirm the diverse applicability of ACES, a novel technique to prepare fibrous drug delivery systems.

  7. Effects of ionic liquids on cation dynamics in amorphous polyethylene oxide electrolytes

    SciTech Connect

    Chattoraj, Joyjit Diddens, Diddo; Heuer, Andreas

    2014-01-14

    We perform extensive molecular dynamics simulations of a poly(ethylene oxide)-based polymer electrolyte material containing lithium bis(trifluoromethanesulfonyl)imide salt for a wide temperature regime above and below the experimental crystallization temperature with and without N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid (IL). The impact of the IL-concentration on the cation dynamics is studied. The increase of the cation mobility upon addition of IL is significant but temperature-independent. This can be related to distinct variations of the underlying transport properties as expressed within the previously introduced transport model of polymer electrolytes. Even for the largest IL concentration the transport model perfectly predicts the non-trivial time-dependence of the cationic mean square displacement for all temperatures. Finally, we compare our numerical and theoretical findings with the results of recent nuclear magnetic resonance experiments. In this way we can exclusively relate the strong experimentally observed dependence of the low-temperature Li-diffusivity on the IL concentration to the impact of IL on crystallization.

  8. Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide

    SciTech Connect

    Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O.; Jalarvo, Niina H.; Hong, Kunlun; Han, Youngkyu; Smith, Gregory S.; Do, Changwoo

    2015-11-03

    We studied the dynamics of water in polyethylene oxide (PEO)/LiCl solution with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. Furthermore, the measured diffusion coefficient of interfacial water remained 5–10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li+. Detailed analysis of MD trajectories suggests that Li+ is favorably found at the surface of the hydration layer, and the probability to find the caged Li+ configuration formed by the PEO is lower than for the noncaged Li+-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li+ hydration complexes. Moreover, performing the MD simulation with different ions (Na+ and K+) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.

  9. In Situ Study of Strain-Dependent Ion Conductivity of Stretchable Polyethylene Oxide Electrolyte

    PubMed Central

    Kelly, Taylor; Ghadi, Bahar Moradi; Berg, Sean; Ardebili, Haleh

    2016-01-01

    There is a strong need in developing stretchable batteries that can accommodate stretchable or irregularly shaped applications including medical implants, wearable devices and stretchable electronics. Stretchable solid polymer electrolytes are ideal candidates for creating fully stretchable lithium ion batteries mainly due to their mechanical and electrochemical stability, thin-film manufacturability and enhanced safety. However, the characteristics of ion conductivity of polymer electrolytes during tensile deformation are not well understood. Here, we investigate the effects of tensile strain on the ion conductivity of thin-film polyethylene oxide (PEO) through an in situ study. The results of this investigation demonstrate that both in-plane and through-plane ion conductivities of PEO undergo steady and linear growths with respect to the tensile strain. The coefficients of strain-dependent ion conductivity enhancement (CSDICE) for in-plane and through-plane conduction were found to be 28.5 and 27.2, respectively. Tensile stress-strain curves and polarization light microscopy (PLM) of the polymer electrolyte film reveal critical insights on the microstructural transformation of stretched PEO and the potential consequences on ionic conductivity. PMID:26831948

  10. Photopolymerization-induced crystallization and phase separation in poly(ethylene oxide)/triacrylate blends

    SciTech Connect

    Park, Soo Jeoung; Kyu, Thein

    2008-12-28

    The present article describes experimental and theoretical investigations of miscibility and crystallization behavior of blends of poly(ethylene oxide) (PEO) and triacrylate monomer (TA) using differential scanning calorimetry and optical microscopy. The PEO/TA blends manifested a single T{sub g} varying systematically with composition suggestive of a miscible character in their amorphous states. Moreover, there occurs melting point depression of PEO crystals with increasing TA. A phase diagram was subsequently established that exhibited a solid+liquid coexistence region bound by the liquidus and solidus lines, followed by an upper critical solution temperature (UCST) at a lower temperature. The emerging phase morphology was investigated to verify the coexistence regions. Upon photopolymerization in the isotropic melt above the melting point depression curve, both the UCST and the melting temperatures move upward and eventually surpass the reaction temperature, resulting in phase separation as well as crystallization of PEO driven by the changing supercooling, i.e., the thermodynamic driving force. Of particular interest is the interplay between photopolymerization-induced phase separation and crystallization, which eventually determines the final phase morphology of the PEO/TA blend such as crystalline lamellae, sheaf, or spherulites in isotropic liquid, phase separated domains, and viscous fingering liquids.

  11. Photopolymerization-induced crystallization and phase separation in poly(ethylene oxide)/triacrylate blends.

    PubMed

    Park, Soo Jeoung; Kyu, Thein

    2008-12-28

    The present article describes experimental and theoretical investigations of miscibility and crystallization behavior of blends of poly(ethylene oxide) (PEO) and triacrylate monomer (TA) using differential scanning calorimetry and optical microscopy. The PEO/TA blends manifested a single T(g) varying systematically with composition suggestive of a miscible character in their amorphous states. Moreover, there occurs melting point depression of PEO crystals with increasing TA. A phase diagram was subsequently established that exhibited a solid+liquid coexistence region bound by the liquidus and solidus lines, followed by an upper critical solution temperature (UCST) at a lower temperature. The emerging phase morphology was investigated to verify the coexistence regions. Upon photopolymerization in the isotropic melt above the melting point depression curve, both the UCST and the melting temperatures move upward and eventually surpass the reaction temperature, resulting in phase separation as well as crystallization of PEO driven by the changing supercooling, i.e., the thermodynamic driving force. Of particular interest is the interplay between photopolymerization-induced phase separation and crystallization, which eventually determines the final phase morphology of the PEO/TA blend such as crystalline lamellae, sheaf, or spherulites in isotropic liquid, phase separated domains, and viscous fingering liquids.

  12. Metal adsorption of gamma-irradiated carboxymethyl cellulose/polyethylene oxide blend films

    NASA Astrophysics Data System (ADS)

    El-Naggar, Amal A.; Magida, M. M.; Ibrahim, Sayeda M.

    2016-03-01

    Blend films of different ratios of carboxymethyl cellulose (CMC)/polyethylene oxide (PEO) were prepared by the solution casting method. To investigate the effect of irradiation on all properties of prepared blend, it was exposed to different gamma irradiation doses (10, 20, and 30 kGy). Physical properties such as gel fraction (GF) (%) and swelling (SW) (%) were investigated. It was found that the GF (%) increases with increasing irradiation dose up to 20 kGy, while SW (%) decreases with an increase in the irradiation doses for all blend compositions. Moreover, the structural and mechanical properties of the prepared films were studied. The results of the mechanical properties obtained showed that there is an improvement in these properties with an increase in both CMC and irradiation dose up to 20 kGy. The efficiency of metal ions uptake was measured using a UV spectrophotometer. The prepared films showed good tendency to absorb and release metal ions from aqueous media. Thus, the CMC/PEO film can be used in agricultural domain.

  13. In Situ Study of Strain-Dependent Ion Conductivity of Stretchable Polyethylene Oxide Electrolyte

    NASA Astrophysics Data System (ADS)

    Kelly, Taylor; Ghadi, Bahar Moradi; Berg, Sean; Ardebili, Haleh

    2016-02-01

    There is a strong need in developing stretchable batteries that can accommodate stretchable or irregularly shaped applications including medical implants, wearable devices and stretchable electronics. Stretchable solid polymer electrolytes are ideal candidates for creating fully stretchable lithium ion batteries mainly due to their mechanical and electrochemical stability, thin-film manufacturability and enhanced safety. However, the characteristics of ion conductivity of polymer electrolytes during tensile deformation are not well understood. Here, we investigate the effects of tensile strain on the ion conductivity of thin-film polyethylene oxide (PEO) through an in situ study. The results of this investigation demonstrate that both in-plane and through-plane ion conductivities of PEO undergo steady and linear growths with respect to the tensile strain. The coefficients of strain-dependent ion conductivity enhancement (CSDICE) for in-plane and through-plane conduction were found to be 28.5 and 27.2, respectively. Tensile stress-strain curves and polarization light microscopy (PLM) of the polymer electrolyte film reveal critical insights on the microstructural transformation of stretched PEO and the potential consequences on ionic conductivity.

  14. Poly(propylene fumarate)/Polyethylene Glycol-Modified Graphene Oxide Nanocomposites for Tissue Engineering.

    PubMed

    Díez-Pascual, Ana M; Díez-Vicente, Angel L

    2016-07-20

    Poly(propylene fumarate) (PPF)-based nanocomposites incorporating different amounts of polyethylene glycol-functionalized graphene oxide (PEG-GO) have been prepared via sonication and thermal curing, and their surface morphology, structure, thermal stability, hydrophilicity, water absorption, biodegradation, cytotoxicity, mechanical, viscoelastic and antibacterial properties have been investigated. SEM and TEM images corroborated that the noncovalent functionalization with PEG caused the exfoliation of GO into thinner flakes. IR spectra suggested the presence of strong hydrogen-bonding interactions between the nanocomposite components. A gradual rise in the level of hydrophilicity, water uptake, biodegradation rate, surface roughness, protein absorption capability and thermal stability was found upon increasing GO concentration in the composites. Tensile tests revealed improved stiffness, strength and toughness for the composites compared to unfilled PPF, ascribed to a homogeneous GO dispersion within the matrix along with a strong PPF/PEG-GO interfacial adhesion via polar and hydrogen bonding interactions. Further, the nanocomposites retained enough stiffness and strength under a biological state to provide effective support for bone tissue formation. The antibacterial activity was investigated against Gram-positive Staphylococcus aureus and Staphylococcus epidermidis as well as Gram-negative Pseudomonas aeruginosa and Escherichia coli microorganisms, and it rose sharply upon increasing GO concentration; systematically, the biocide effect was stronger versus Gram-positive bacteria. Cell viability data demonstrated that PPF/PEG-GO composites do not induce toxicity over human dermal fibroblasts. These novel materials show great potential to be applied in the bone tissue engineering field.

  15. Polyethylene oxide (PEO)-hyaluronic acid (HA) nanofibers with kanamycin inhibits the growth of Listeria monocytogenes.

    PubMed

    Ahire, J J; Robertson, D D; van Reenen, A J; Dicks, L M T

    2017-02-01

    Listeria monocytogenes is well known to cause prosthetic joint infections in immunocompromised patients. In this study, polyethylene oxide (PEO) nanofibers, containing kanamycin and hyaluronic acid (HA), were prepared by electrospinning at a constant electric field of 10kV. PEO nanofibers spun with 0.2% (w/v) HA and 1% (w/v) kanamycin had a smooth, bead-free structure at 30-35% relative humidity. The average diameter of the nanofibers was 83±20nm. Attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy indicated that kanamycin was successfully incorporated into PEO/HA matrix. The presence of kanamycin affects the thermal properties of PEO/HA nanofibers, as shown by differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The kanamycin-PEO-HA nanofibers (1mg; 47±3μg kanamycin) inhibited the growth of L. monocytogenes EDGe by 62%, as compared with PEO-HA nanofibers, suggesting that it may be used to coat prosthetic implants to prevent secondary infections.

  16. Lithium Ion Pathway within Li7 La3 Zr2 O12 -Polyethylene Oxide Composite Electrolytes.

    PubMed

    Zheng, Jin; Tang, Mingxue; Hu, Yan-Yan

    2016-09-26

    Polymer-ceramic composite electrolytes are emerging as a promising solution to deliver high ionic conductivity, optimal mechanical properties, and good safety for developing high-performance all-solid-state rechargeable batteries. Composite electrolytes have been prepared with cubic-phase Li7 La3 Zr2 O12 (LLZO) garnet and polyethylene oxide (PEO) and employed in symmetric lithium battery cells. By combining selective isotope labeling and high-resolution solid-state Li NMR, we are able to track Li ion pathways within LLZO-PEO composite electrolytes by monitoring the replacement of (7) Li in the composite electrolyte by (6) Li from the (6) Li metal electrodes during battery cycling. We have provided the first experimental evidence to show that Li ions favor the pathway through the LLZO ceramic phase instead of the PEO-LLZO interface or PEO. This approach can be widely applied to study ion pathways in ionic conductors and to provide useful insights for developing composite materials for energy storage and harvesting.

  17. Encapsulation of T4 bacteriophage in electrospun poly(ethylene oxide)/cellulose diacetate fibers.

    PubMed

    Korehei, Reza; Kadla, John F

    2014-01-16

    Phage therapy is a potentially beneficial approach to food preservation and storage. Sustained delivery of bacteriophage can prevent bacterial growth on contaminated food surfaces. Using coaxial electrospinning bacteriophage can be encapsulated in electrospun fibers with high viability. The resulting bio-based electrospun fibers may have potential as a food packaging material. In the present work, T4 bacteriophage (T4 phage) was incorporated into core/shell electrospun fibers made from poly(ethylene oxide) (PEO), cellulose diacetate (CDA), and their blends. Fibers prepared using PEO as the shell polymer showed an immediate burst release of T4 phage upon submersion in buffer. The blending of CDA with PEO significantly decreased the rate of phage release, with no released T4 phage being detected from the solely CDA fibers. Increasing the PEO molecular weight increased the electrospun fiber diameter and viscosity of the releasing medium, which resulted in a relatively slower T4 phage release profile. SEM analyses of the electrospun fiber morphologies were in good agreement with the T4 phage release profiles. Depending on the PEO/CDA ratio, the post-release electrospun fiber morphologies varied from discontinuous fibers to minimally swollen fibers. From these results it is suggested that the T4 phage release mechanism is through solvent activation/polymer dissolution in the case of the PEO fibers and/or by diffusion control from the PEO/CDA blend fibers.

  18. Effects of ionic liquids on cation dynamics in amorphous polyethylene oxide electrolytes.

    PubMed

    Chattoraj, Joyjit; Diddens, Diddo; Heuer, Andreas

    2014-01-14

    We perform extensive molecular dynamics simulations of a poly(ethylene oxide)-based polymer electrolyte material containing lithium bis(trifluoromethanesulfonyl)imide salt for a wide temperature regime above and below the experimental crystallization temperature with and without N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid (IL). The impact of the IL-concentration on the cation dynamics is studied. The increase of the cation mobility upon addition of IL is significant but temperature-independent. This can be related to distinct variations of the underlying transport properties as expressed within the previously introduced transport model of polymer electrolytes. Even for the largest IL concentration the transport model perfectly predicts the non-trivial time-dependence of the cationic mean square displacement for all temperatures. Finally, we compare our numerical and theoretical findings with the results of recent nuclear magnetic resonance experiments. In this way we can exclusively relate the strong experimentally observed dependence of the low-temperature Li-diffusivity on the IL concentration to the impact of IL on crystallization.

  19. Effects of ionic liquids on cation dynamics in amorphous polyethylene oxide electrolytes

    NASA Astrophysics Data System (ADS)

    Chattoraj, Joyjit; Diddens, Diddo; Heuer, Andreas

    2014-01-01

    We perform extensive molecular dynamics simulations of a poly(ethylene oxide)-based polymer electrolyte material containing lithium bis(trifluoromethanesulfonyl)imide salt for a wide temperature regime above and below the experimental crystallization temperature with and without N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid (IL). The impact of the IL-concentration on the cation dynamics is studied. The increase of the cation mobility upon addition of IL is significant but temperature-independent. This can be related to distinct variations of the underlying transport properties as expressed within the previously introduced transport model of polymer electrolytes. Even for the largest IL concentration the transport model perfectly predicts the non-trivial time-dependence of the cationic mean square displacement for all temperatures. Finally, we compare our numerical and theoretical findings with the results of recent nuclear magnetic resonance experiments. In this way we can exclusively relate the strong experimentally observed dependence of the low-temperature Li-diffusivity on the IL concentration to the impact of IL on crystallization.

  20. The diffusion and conduction of lithium in poly(ethylene oxide)-based sulfonate ionomers

    NASA Astrophysics Data System (ADS)

    LaFemina, Nikki H.; Chen, Quan; Colby, Ralph H.; Mueller, Karl T.

    2016-09-01

    Pulsed field gradient nuclear magnetic resonance spectroscopy and dielectric relaxation spectroscopy have been utilized to investigate lithium dynamics within poly(ethylene oxide) (PEO)-based lithium sulfonate ionomers of varying ion content. The ion content is set by the fraction of sulfonated phthalates and the molecular weight of the PEO spacer, both of which can be varied independently. The molecular level dynamics of the ionomers are dominated by either Vogel-Fulcher-Tammann or Arrhenius behavior depending on ion content, spacer length, temperature, and degree of ionic aggregation. In these ionomers the main determinants of the self-diffusion of lithium and the observed conductivities are the ion content and ionic states of the lithium ion, which are profoundly affected by the interactions of the lithium ions with the ether oxygens of the polymer. Since many lithium ions move by segmental polymer motion in the ion pair state, their diffusion is significantly larger than that estimated from conductivity using the Nernst-Einstein equation.

  1. High efficiency solid state dye sensitized solar cells with graphene-polyethylene oxide composite electrolytes.

    PubMed

    Akhtar, M Shaheer; Kwon, Soonji; Stadler, Florian J; Yang, O Bong

    2013-06-21

    Novel and highly effective composite electrolytes were prepared by combining the two dimensional graphene (Gra) and polyethylene oxide (PEO) for the solid electrolyte of dye sensitized solar cells (DSSCs). Gra sheets were uniformly coated by the polymer layer through the ester carboxylate bonding between oxygenated species on Gra sheets and PEO. The Gra-PEO composite electrolyte showed the large scale generation of iodide ions in a redox couple. From rheological analysis, the decrease in viscosity after the addition of LiI and I2 in the Gra-PEO electrolyte might be explained by the dipolar interactions being severely disrupted by the ionic interactions of Li(+), I(-), and I3(-) ions. A composite electrolyte with 0.5 wt% Gra presented a higher ionic conductivity (3.32 mS cm(-1)) than those of PEO and other composite electrolytes at room temperature. A high overall conversion efficiency (∼5.23%) with a very high short circuit current (JSC) of 18.32 mA cm(-2), open circuit voltage (VOC) of 0.592 V and fill factor (FF) of 0.48 was achieved in DSSCs fabricated with the 0.5 wt% Gra-PEO composite electrolyte. This enhanced photovoltaic performance might be attributed to the large scale formation of iodide ions in the redox electrolyte and the relatively high ionic conductivity.

  2. Ultrahigh molecular weight polyethylene/graphene oxide nanocomposites: wear characterization and biological response to wear particles.

    PubMed

    Suñer, S; Gowland, N; Craven, R; Joffe, R; Emami, N; Tipper, J L

    2016-12-09

    In the field of total joint replacements, polymer nanocomposites are being investigated as alternatives to ultrahigh molecular weight polyethylene (UHMWPE) for acetabular cup bearings. The objective of this study was to investigate the wear performance and biocompatibility of UHMWPE/graphene oxide (GO) nanocomposites. This study revealed that low concentrations of GO nanoparticles (0.5 wt %) do not significantly alter the wear performance of UHMWPE. In contrast, the addition of higher concentrations (2 wt %) led to a significant reduction in wear. In terms of biocompatibility, UHMWPE/GO wear particles did not show any adverse effects on L929 fibroblast and PBMNC viability at any of the concentrations tested over time. Moreover, the addition of GO to a UHMWPE matrix did not significantly affect the inflammatory response to wear particles. Further work is required to optimize the manufacturing processes to improve the mechanical properties of the nanocomposites and additional biocompatibility testing should be performed to understand the potential clinical application of these materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  3. Scaling law of poly(ethylene oxide) chain permeation through a nanoporous wall.

    PubMed

    Choudhury, Rudra Prosad; Galvosas, Petrik; Schönhoff, Monika

    2008-10-23

    This paper presents a study of the permeation of poly(ethylene oxide) (PEO) chains through the nanoporous wall of hollow polymeric capsules prepared by self-assembly of polyelectrolytes. We employ the method of pulsed field gradient (PFG) NMR diffusion to distinguish chains in different sites, i.e., in the capsule interior and free chains in the dispersion, by their respective diffusion coefficient. From a variation of the observation time, the time scale of the molecular exchange between both sites and thus the permeation rate constant is extracted from a two-site exchange model. Permeation rate constants show two different regimes with a different dependence on chain length. This suggests a transition between two different mechanisms of permeation as the molecular weight is increased. In either regime, the permeation time can be described by a scaling law tau approximately N (b) , with b = (4)/ 3 for short chains and b = (1)/ 3 for long chains. We discuss these exponents, which clearly differ from the theoretical predictions for chain translocation.

  4. Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

    NASA Astrophysics Data System (ADS)

    Porras, R.; Bavykin, D. V.; Zekonyte, J.; Walsh, F. C.; Wood, R. J.

    2016-05-01

    Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

  5. Influence of chain topology on polymer crystallization: poly(ethylene oxide) (PEO) rings vs. linear chains.

    PubMed

    Zardalidis, George; Mars, Julian; Allgaier, Jürgen; Mezger, Markus; Richter, Dieter; Floudas, George

    2016-10-04

    The absence of entanglements, the more compact structure and the faster diffusion in melts of cyclic poly(ethylene oxide) (PEO) chains have consequences on their crystallization behavior at the lamellar and spherulitic length scales. Rings with molecular weight below the entanglement molecular weight (M < Me), attain the equilibrium configuration composed from twice-folded chains with a lamellar periodicity that is half of the corresponding linear chains. Rings with M > Me undergo distinct step-like conformational changes to a crystalline lamellar with the equilibrium configuration. Rings melt from this configuration in the absence of crystal thickening in sharp contrast to linear chains. In general, rings more easily attain their extended equilibrium configuration due to strained segments and the absence of entanglements. In addition, rings have a higher equilibrium melting temperature. At the level of the spherulitic superstructure, growth rates are much faster for rings reflecting the faster diffusion and more compact structure. With respect to the segmental dynamics in their semi-crystalline state, ring PEOs with a steepness index of ∼34 form some of the "strongest" glasses.

  6. Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide

    DOE PAGES

    Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O.; ...

    2015-11-03

    We studied the dynamics of water in polyethylene oxide (PEO)/LiCl solution with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. Furthermore, the measured diffusion coefficient of interfacial water remained 5–10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li+. Detailed analysis of MD trajectories suggests that Li+ is favorably found at the surface of the hydration layer, and the probability to find the caged Li+ configuration formed by the PEO is lowermore » than for the noncaged Li+-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li+ hydration complexes. Moreover, performing the MD simulation with different ions (Na+ and K+) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.« less

  7. Amperometric Biosensor Based on Zirconium Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of Phenolic Compounds

    PubMed Central

    Ahmad, Nor Monica; Abdullah, Jaafar; Yusof, Nor Azah; Ab Rashid, Ahmad Hazri; Abd Rahman, Samsulida; Hasan, Md. Rakibul

    2016-01-01

    A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE). Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and Cyclic voltamogram (CV). The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075–10 µM and 10–55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days. PMID:27367738

  8. Amperometric Biosensor Based on Zirconium Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of Phenolic Compounds.

    PubMed

    Ahmad, Nor Monica; Abdullah, Jaafar; Yusof, Nor Azah; Ab Rashid, Ahmad Hazri; Abd Rahman, Samsulida; Hasan, Md Rakibul

    2016-06-29

    A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE). Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and Cyclic voltamogram (CV). The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075-10 µM and 10-55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days.

  9. Field Effect Transistor Behavior in Electrospun Polyaniline/Polyethylene Oxide Demonstrated

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; Theofylaktos, Onoufrios; Robinson, Daryl C.; Miranda, Felix A.

    2004-01-01

    Novel transistors and logic devices based on nanotechnology concepts are under intense development. The potential for ultra-low-power circuitry makes nanotechnology attractive for applications such as digital electronics and sensors. For NASA applications, nanotechnology offers tremendous opportunities for increased onboard data processing, and thus autonomous decisionmaking ability, and novel sensors that detect and respond to environmental stimuli with little oversight requirements. Polyaniline/polyethylene oxide (PANi/PEO) nanofibers are of interest because they have electrical conductivities that can be changed from insulating to metallic by varying the doping levels and conformations of the polymer chain. At the NASA Glenn Research Center, we have observed field effect transistor (FET) behavior in electrospun PANi/PEO nanofibers doped with camphorsulfonic acid. The nanofibers were deposited onto Au electrodes, which had been prepatterned onto oxidized silicon substrates. The preceding scanning electron image shows the device used in the transistor measurements. Saturation channel currents are observed at surprisingly low source/drain voltages (see the following graph). The hole mobility in the depletion regime is 1.4x10(exp -4)sq cm/V sec, whereas the one-dimensional charge density (at zero gate bias) is calculated to be approximately 1 hole per 50 two-ring repeat units of polyaniline, consistent with the rather high channel conductivity (approx.10(exp -3) S/cm). Reducing or eliminating the PEO content in the fiber is expected to enhance device parameters. Electrospinning is thus proposed as a simple method of fabricating one-dimensional polymer FET's.

  10. Relationship between hydroperoxide concentration and average molar mass in thermo-oxidized polyethylene

    NASA Astrophysics Data System (ADS)

    Da Cruz, Manuela; Van Schoors, Laetitia; Colin, Xavier; Benzarti, Karim

    2014-05-01

    The aim of this research project is to investigate the oxidation mechanism of high density polyethylene (HDPE) used in outdoor applications, in order to establish in a near future, a non-empirical kinetic model for lifetime prediction. The present paper focuses on the changes in the hydroperoxide (POOH) concentration induced by thermo-oxidative ageing, and on their relationship with the evolution of the weight average molar mass (Mw) due both to chain scission and crosslinking processes. Thin HDPE films were aged at 110 and 140°C in air under atmospheric pressure. In a first part, changes in the POOH concentration versus ageing time were assessed by three different analytical methods previously reported in the literature: modulated differential scattering calorimetry (MDSC), Fourier transform Infra-Red spectrometry after chemical derivatization treatment with gaseous sulfur dioxide (SO2-FTIR), and iodometry. A comparison of experimental results revealed that these three methods provide very similar quantitative data on POOH accumulation, whereas iodometry tends to strongly underestimate the subsequent stage of POOH decomposition. It was thus suspected that iodometry does not only titrate POOH, but also other chemical species (presumably double bonds) formed when POOH decompose. Therefore, only MDSC and SO2-FTIR were considered as relevant methods for POOH titration. In a second part, changes in Mw versus ageing time were monitored by size exclusion chromatography (SEC). A sharp drop of Mw was first observed at the beginning of exposure, which was assigned to an intensive chain scission process. Then, in a second stage, a stabilization or even a substantial re-increase in Mw was observed, suggesting a competition between chain scission and crosslinking processes. As this second stage starts at the same time as POOH decomposition, it was concluded that there is a strong correlation between both phenomena, occurring respectively at the macromolecular and molecular

  11. Zwitterionic Iron Oxide (γ-Fe2 O3 ) Nanoparticles Based on P(2VP-grad-AA) Copolymers.

    PubMed

    Billing, Mark; Gräfe, Christine; Saal, Adrian; Biehl, Philip; Clement, Joachim H; Dutz, Silvio; Weidner, Steffen; Schacher, Felix H

    2017-02-01

    This study presents the synthesis and characterization of zwitterionic core-shell hybrid nanoparticles consisting of a core of iron oxide multicore nanoparticles (MCNPs, γ-Fe2 O3 ) and a shell of sultonated poly(2-vinylpyridine-grad-acrylic acid) copolymers. The gradient copolymers are prepared by reversible addition fragmentation chain transfer polymerization of 2-vinylpyridine (2VP), followed by the addition of tert-butyl acrylate and subsequent hydrolysis. Grafting of P(2VP-grad-AA) onto MCNP results in P(2VP-grad-AA)@MCNP, followed by quaternization using 1,3-propanesultone-leading to P(2VPS -grad-AA)@MCNP with a zwitterionic shell. The resulting particles are characterized by transmission electron microscopy, dynamic light scattering, and thermogravimetric analysis measurements, showing particle diameters of ≈70-90 nm and an overall content of the copolymer shell of ≈10%. Turbidity measurements indicate increased stability toward secondary aggregation after coating if compared to the pristine MCNP and additional cytotoxicity tests do not reveal any significant influence on cell viability.

  12. Phase Behavior and Ionic Conductivity of Concentrated Solutions of Polystyrene-Poly(ethylene oxide) Diblock Copolymers in an Ionic Liquid

    SciTech Connect

    Simone, Peter M.; Lodge, Timothy P.

    2010-03-16

    Concentrated solutions of poly(styrene-b-ethylene oxide) (PS-PEO) diblock copolymers were prepared using the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMI][TFSI] as the solvent. The self-assembled microstructures adopted by the copolymer solutions have been characterized using small-angle X-ray scattering. Lyotropic mesophase transitions were observed, with a progression from hexagonally packed cylinders of PEO, to lamellae, to hexagonally packed cylinders of PS upon increasing [EMI][TFSI] content. The change in lamellar domain spacing with ionic liquid concentration was found to be comparable to that reported for other block copolymers in strongly selective solvents. The ionic conductivity of the concentrated PS-PEO/[EMI][TFSI] solutions was measured via impedance spectroscopy, and ranged from 1 x 10{sup -7} to 1 x 10{sup -3} S/cm at temperatures from 25-100 C. Additionally, the ionic conductivity of the solutions was found to increase with both ionic liquid concentration and molecular weight of the PEO blocks. The ionic conductivity of PEO homopolymer/[EMI][TFSI] solutions was also measured in order to compare the conductivity of the PS-PEO solutions to the expected limit for a lamellar sample with randomly oriented microstructure grains.

  13. High-concentration graphene dispersion stabilized by block copolymers in ethanol.

    PubMed

    Perumal, Suguna; Lee, Hyang Moo; Cheong, In Woo

    2017-07-01

    This article describes a comprehensive study for the preparation of graphene dispersions by liquid-phase exfoliation using amphiphilic diblock copolymers; poly(ethylene oxide)-block-poly(styrene) (PEO-b-PS), poly(ethylene oxide)-block-poly(4-vinylpyridine) (PEO-b-PVP), and poly(ethylene oxide)-block-poly(pyrenemethyl methacrylate) (PEO-b-PPy) with similar block lengths. Block copolymers were prepared from PEO using the Steglich coupling reaction followed by reversible addition-fragmentation chain transfer (RAFT) polymerization. Graphite platelets (G) and reduced graphene oxide (rGO) were used as graphene sources. The dispersion stability of graphene in ethanol was comparatively investigated by on-line turbidity, and the graphene concentration in the dispersions was determined gravimetrically. Our results revealed that the graphene dispersions with PEO-b-PVP were much more stable and included graphene with fewer defects than that with PEO-b-PS or PEO-b-PPy, as confirmed by turbidity and Raman analyses. Gravimetry confirmed that graphene concentrations up to 1.7 and 1.8mg/mL could be obtained from G and rGO dispersions, respectively, using PEO-b-PVP after one week. Distinctions in adhesion forces of PS, VP, PPy block units with graphene surface and the variation in solubility of the block copolymers in ethanol medium significantly affected the stability of the graphene dispersion.

  14. Explaining the Cyclic Voltammetry of a Poly(1,4-phenylene-ethynylene)-alt-poly(1,4-phenylene-vinylene) Copolymer upon Oxidation by using Spectroscopic Techniques.

    PubMed

    Enengl, Christina; Enengl, Sandra; Bouguerra, Nassima; Havlicek, Marek; Neugebauer, Helmut; Egbe, Daniel A M

    2017-01-04

    Poly(1,4-phenylene-ethynylene)-alt-poly(1,4-phenylene-vinylene) (PPE-PPV) copolymers have attracted quite a lot of attention in the last few years for electronic device applications owing to their enhanced fluorescence. In this work, we focus on one particular PPE-PPV copolymer with dissymmetrically substituted 1,4-phenylene-ethynylene and symmetrically substituted 1,4-phenylene-vinylene building units. Six successively performed cyclic voltammograms are presented, measured during the oxidation reactions. As the oxidation onset of the electrochemical reaction shifts to lower potentials in each cycle, this behavior is elucidated by using spectroscopic techniques ranging from UV/Vis/near-IR to mid-IR including spin-resonance techniques. Hence, these findings help to explain some of the copolymer's most advantageous properties in terms of possible oxidation products.

  15. Controlled release of cefazolin sodium antibiotic drug from electrospun chitosan-polyethylene oxide nanofibrous Mats.

    PubMed

    Fazli, Yousef; Shariatinia, Zahra

    2017-02-01

    Antimicrobial electrospun chitosan-polyethylene oxide (CS-PEO) nanofibrous mats containing cefazolin, fumed silica (F. silica) and cefazolin-loaded fumed silica nanoparticles (NPs) were produced for biomedical applications. The FE-SEM images revealed that the F. silica and F. silica-cefazolin NPs had average diameters of 40±10 and 60±15nm, respectively. Also, the fibers diameters were approximately 160±30, 90±20 and 70±15nm for the pure CS-PEO, CS-PEO-1% F. silica and CS-PEO-1% F. silica-0.5% cefazolin nanofibrous mats, respectively indicating addition of F. silica and cefazolin loaded F. silica NPs to the CS-PEO mat led to decreasing the nanofiber diameter. Both of the CS-PEO mats containing 2.5% cefazolin and 1% F. silica-0.50% cefazolin showed 100% bactericidal activities against both S. aureus and E. coli bacteria. The cefazolin release from mats was sharply increased within first 24 and 6hours for the CS-PEO mats including 2.5% cefazolin and 1% F. silica-0.50% cefazolin but after that the drug was released very slowly. The improved hydrophilicity, higher tensile strength and sustained drug release for CS-PEO-1% F. silica-0.50% cefazolin suggested that it was the best nanocomposite tissue/device for biomedical applications among the mats CS-PEO-2.5% cefazolin and CS-PEO-1% F. silica. The wound healing ability of the CS-PEO-F. silica-cefazolin mat was evaluated on the wounded skins of the female Wistar rats and it was shown that the wounded skins of the rats were almost entirely healed after ten days using this mat as a wound dressing scaffold.

  16. Sustained release from hot-melt extruded matrices based on ethylene vinyl acetate and polyethylene oxide.

    PubMed

    Almeida, A; Brabant, L; Siepmann, F; De Beer, T; Bouquet, W; Van Hoorebeke, L; Siepmann, J; Remon, J P; Vervaet, C

    2012-11-01

    The aim of the present study was to evaluate the importance of matrix flexibility of hot-melt extruded (HME) ethylene vinyl acetate (EVA) matrices (with vinyl acetate (VA) contents of 9%, 15%, 28% and 40%), through the addition of hydrophilic polymers with distinct swelling capacity. Polyethylene oxide (PEO 100K, 1M and 7M) was used as swelling agent and metoprolol tartrate (MPT) as model drug. The processability via HME and drug release profiles of EVA/MPT/PEO formulations were assessed. Solid state characteristics, porosity and polymer miscibility of EVA/PEO matrices were evaluated by means of DSC, X-ray tomography and Raman spectroscopy. The processability via HME varied according to the VA content: EVA 40 and 28 were extruded at 90°C, whereas higher viscosity EVA grades (EVA 15 and 9) required a minimum extrusion temperature of 110°C to obtain high-quality extrudates. Drug release from EVA matrices depended on the VA content, PEO molecular weight and PEO content, matrix porosity as well as pore size distribution. Interestingly, the interplay of PEO leaching, matrix swelling, water influx and changes in matrix porosity influenced drug release: EVA 40- and 28-based matrices extruded with PEO of higher MW accelerated drug release, whereas for EVA 15- and 9-based matrices, drug release slowed down. These differences were related to the distinct polymer flexibility imposed by the VA content (lower VA content presents higher crystallinity and less free movement of the amorphous segments resulting in a higher rigidity). In all cases, diffusional mass transport seems to play a major role, as demonstrated by mathematical modeling using an analytical solution of Fick's second law. The bioavailability of EVA 40 and 28 matrices in dogs was not significantly different, independent of PEO 7M concentration.

  17. Nonfouling poly(ethylene oxide) layers end-tethered to polydopamine.

    PubMed

    Pop-Georgievski, Ognen; Verreault, Dominique; Diesner, Mark-Oliver; Proks, Vladimír; Heissler, Stefan; Rypáček, František; Koelsch, Patrick

    2012-10-09

    Nonfouling surfaces capable of reducing protein adsorption are highly desirable in a wide range of applications. Coating of surfaces with poly(ethylene oxide) (PEO), a water-soluble, nontoxic, and nonimmunogenic polymer, is most frequently used to reduce nonspecific protein adsorption. Here we show how to prepare dense PEO brushes on virtually any substrate by tethering PEO to polydopamine (PDA)-modified surfaces. The chain lengths of hetero-bifunctional PEOs were varied in the range of 45-500 oxyethylene units (M(n) = 2000-20,000). End-tethering of PEO chains was performed through amine and thiol headgroups from reactive polymer melts to minimize excluded volume effects. Surface plasmon resonance (SPR) was applied to investigate the adsorption of model protein solutions and complex biologic medium (human blood plasma) to the densely packed PEO brushes. The level of protein adsorption of human serum albumin and fibrinogen solutions was below the detection limit of the SPR measurements for all PEO chains end-tethered to PDA, thus exceeding the protein resistance of PEO layers tethered directly on gold. It was found that the surface resistance to adsorption of lysozyme and human blood plasma increased with increasing length and brush character of the PEO chains end-tethered to PDA with a similar or better resistance in comparison to PEO layers on gold. Furthermore, the chain density, thickness, swelling, and conformation of PEO layers were determined using spectroscopic ellipsometry (SE), dynamic water contact angle (DCA) measurements, infrared reflection-absorption spectroscopy (IRRAS), and vibrational sum-frequency-generation (VSFG) spectroscopy, the latter in air and water.

  18. Correlating self-assembly of block copolymers for their application in synthesis of gold nanoparticles.

    PubMed

    Ray, Debes; Aswall, Vinod Kumar; Srivastava, Dinesh

    2011-03-01

    We report the role of self-assembly of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) block copolymers for the synthesis of gold nanoparticles from hydrogen tetrachloroaureate (III) hydrate (HAuCl4 x 3H2O) in aqueous solution. The synthesis has been carried out using three different block copolymers P85 [EO26PO39EO26], F88 [EO103PO39EO103] and P105 [EO37PO56EO37], which not only have varying molecular weight but also differ in hydrophobicity to hydrophilicity ratio. The formation of gold nanoparticles is confirmed by the UV-Visible Spectroscopy. Transmission electron microscopy (TEM) provides the sizes of the nanoparticles formed in these systems. Small-Angle Neutron Scattering (SANS) and Dynamic Light Scattering (DLS) techniques are used to correlate the self-assembly of block copolymer to their propensity to form gold nanoparticles. The yield is found to be in the order P105 > P85 > F88 and is related to the higher tendency of block copolymer to self-assemble to give greater yield of gold nanoparticles. For all the block copolymers, SANS and DLS results suggests that the yield in the synthesis does not always increases with the salt concentration and is limited due to the fact that most of the block copolymers remain unassociated with the gold nanoparticles. By making use of these unassociated block copolymers, we propose two methods (i) step addition method and (ii) additional reductant method, where the synthesis yield of gold nanoparticles can be enhanced by manifold.

  19. Extraction of americium in different oxidation states in a two-phase aqueous system based on poly(ethylene glycol)

    SciTech Connect

    Molochnikova, N.P.; Frenkel', B.F.; Myasoedov, B.F.; Shkinev, V.M.; Spivakov, B.Ya.; Zolotov, Yu.A.

    1987-09-01

    The extraction of americium in different states of oxidation was studied in a two-phase aqueous system based on poly(ethylene glycol). Conditions were found for the quantitative extraction of americium (III) and americium (V) from solutions of ammonium sulfate in the pH range of 3-5 and in the presence of arsenazo III. The composition of the complexes of americium with the reagent was determined; americium (III) reacts with arsenazo III in solutions of ammonium sulfate to form complexes with the composition of MeR and Me/sub 2/R. Characteristics of the absorption spectra of complexes of americium (III) and (V) with arsenazo III in ammonium sulfate solutions and in extracts based on aqueous solutions of poly(ethylene glycol) were found. The molar extinction coefficients of complexes of americium with arsenazo III were determined in these solutions.

  20. Oxidation of Second Generation Sequentially Irradiated and Annealed Highly Cross-Linked X3™ Polyethylene Tibial Bearings.

    PubMed

    Kop, Alan M; Pabbruwe, Moreica B; Keogh, Catherine; Swarts, Eric

    2015-10-01

    Since the first use of ultra-high-molecular-weight polyethylene as a bearing material, research and development efforts have sought to improve wear resistance, increase longevity and lessen the potential for debris mediated adverse tissue responses. A series of second generation sequentially cross-linked and annealed tibial bearings were analysed after several bearings sent for routine retrieval analysis showed oxidative degradation including subsurface whitening, cracking and gross material loss. Evaluation incorporated visual and white banding assessment, mechanical testing and spectroscopy analysis. Whilst visual observation and white banding assessment confirmed oxidative changes, a decrease in mechanical properties and increasing ketone oxidation index as a function of time in vivo suggest time dependent oxidative degradation. Clinically relevant degradation of the sequentially cross-linked and annealed tibial bearings was observed.

  1. pH-sensitive methacrylic copolymers and the production thereof

    SciTech Connect

    Mallapragada, Surya K.; Anderson, Brian C.; Bloom, Paul D.; Sheares Ashby, Valerie V.

    2007-01-09

    The present invention provides novel multi-functional methacrylic copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility under acidic conditions. The copolymers are constructed from tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates. The copolymers are useful as gene vectors, pharmaceutical carriers, and in protein separation applications.

  2. pH-sensitive methacrylic copolymers and the production thereof

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.; Bloom, Paul D.; Sheares Ashby, Valerie V.

    2006-02-14

    The present invention provides novel multi-functional methacrylic copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility under acidic conditions. The copolymers are constructed from tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates. The copolymers are useful as gene vectors, pharmaceutical carriers, and in protein separation applications.

  3. Crystallization behaviour of poly(ethylene oxide) under confinement in the electrospun nanofibers of polystyrene/poly(ethylene oxide) blends.

    PubMed

    Samanta, Pratick; V, Thangapandian; Singh, Sajan; Srivastava, Rajiv; Nandan, Bhanu; Liu, Chien-Liang; Chen, Hsin-Lung

    2016-06-21

    We have studied the confined crystallization behaviour of poly(ethylene oxide) (PEO) in the electrospun nanofibers of the phase-separated blends of polystyrene (PS) and PEO, where PS was present as the major component. The size and shape of PEO domains in the nanofibers were considerably different from those in the cast films, presumably because of the nano-dimensions of the nanofibers and the extensional forces experienced by the polymer solution during electrospinning. The phase-separated morphology in turn influenced the crystallization behaviour of PEO in the blend nanofibers. At a PEO weight fraction of ≥0.3, crystallization occurred through a heterogeneous nucleation mechanism similar to that in cast blend films. However, as the PEO weight fraction in the blend nanofibers was reduced from 0.3 to 0.2, an abrupt transformation of the nucleation mechanism from the heterogeneous to predominantly homogenous type was observed. The change in the nucleation mechanism implied a drastic reduction of the spatial continuity of PEO domains in the nanofibers, which was not encountered in the cast film. The melting temperature and crystallinity of the PEO crystallites developed in the nanofibers were also significantly lower than those in the corresponding cast films. The phenomena observed were reconciled by the morphological observation, which revealed that the phase separation under the radial constraint of the nanofibers led to the formation of small-sized fibrillar PEO domains with limited spatial connectivity. The thermal treatment of the PS/PEO blend nanofibers above the glass transition temperature of PS induced an even stronger confinement effect on PEO crystallization.

  4. MMA/MPEOMA/VSA copolymer as a novel blood-compatible material: ex vivo platelet adhesion study.

    PubMed

    Lee, Jin Ho; Oh, Se Heang; Kim, Won Gon

    2004-02-01

    MMA/MPEOMA/VSA copolymers with both pendant polyethylene oxide (PEO) side chains and negatively chargeable side groups were synthesized by random copolymerization of methyl methacrylate (MMA), methoxy PEO monomethacrylate (MPEOMA; PEO mol. wt, 1000), and vinyl sulfonic acid sodium salt (VSA) monomers with different monomer composition to evaluate their blood compatibility. MMA/MPEOMA copolymer (with PEO side chains) and MMA/VSA copolymer (with negatively chargeable side groups) were also synthesized for the comparison purpose. The synthesized copolymers were coated onto polyurethane (PU) tubes (inner diameter, 4.6 mm) by a spin coating. The platelet adhesion of the MMA/MPEOMA/VSA copolymer-coated tube surfaces was compared with that of tube surface coated with MMA/MPEOMA or MMA/VSA copolymer with similar MPEOMA or VSA composition, using an ex vivo canine arterio-artery shunt method. The platelet adhesion was evaluated by radioactivity counting of technetium (99mTc)-labeled platelets adhered on the surfaces after 30 and 120 min of blood circulation. The MMA/MPEOMA/VSA copolymer (monomer molar ratio 9/0.5/0.5 or 8/1/1) was better in preventing platelet adhesion on the surface than the MMA/MPEOMA or MMA/VSA copolymer with similar MPEOMA or VSA composition, probably owing to the combined effects of highly mobile, hydrophilic PEO side chains and negatively charged VSA side groups.

  5. Preparation of gold microparticles using halide ions in bulk block copolymer phases via photoreduction

    SciTech Connect

    Cha, Sang-Ho; Kim, Ki-Hyun; Lee, Won-Ki; Lee, Jong-Chan

    2009-06-15

    Gold microparticles were prepared from the gold salt in the solid bulk phase of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer via a photoreduction process in the presence of halide ions. The shapes and sizes of the gold microparticles were found to be dependent on the types and amount of halide ions as well as the types of cations used due to the combined effects of the adsorption power and oxidative dissolution ability of the additives on gold surfaces. Gold nanorods were obtained when poly(ethylene oxide) was used instead of the block copolymer. This suggests that the poly(propylene oxide) (PPO) parts in the block copolymer are essential for the formation of gold microparticles, even though the degree of the direct interaction between the PPO blocks and gold salt is not significant. - Graphical abstract: Gold microparticles were successfully prepared using halide ions as additives in the polymeric bulk phase via photoreduction with the glow lamp irradiation.

  6. 12-crown-4 ether-assisted enhancement of ionic conductivity and interfacial kinetics in polyethylene oxide electrolytes

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.

    1990-01-01

    The electrical and electrochemical properties of thin films of polyethylene oxide electrolytes with and without 12-crown-4 ether (12Cr4) are studied as a function of temperature and in the frequency regime from 100 kHz to 0.1 Hz. These measurements were made on electrolytes containing LiCF3SO3, LiBF4, or LiClO4 salts. At a given temperature, the bulk conductivity for a particular salt depends on the 12Cr4 concentration, reaching a maximum for a ratio of 12Cr4 to Li of 0.003.

  7. Experimental analysis of stabilizing effects of carbon nanotubes (CNTs) on thermal oxidation of poly(ethylene glycol)-CNT composites

    NASA Astrophysics Data System (ADS)

    Yamane, Shogo; Ata, Seisuke; Chen, Liang; Sato, Hiroaki; Yamada, Takeo; Hata, Kenji; Mizukado, Junji

    2017-02-01

    In this work, the thermal stabilization of poly(ethylene glycol) (PEG) by super-growth carbon nanotubes (SGCNTs) is studied by analyzing degraded compounds via high-resolution matrix-assisted laser diffusion ionization time-of-flight mass spectroscopy and IR techniques. SGCNTs successfully suppress the thermal oxidation of PEG, and the components of the degraded compounds change upon addition of SGCNTs to PEG. The SGCNTs quench mainly the RO radical generated by the initial chain scission of the Csbnd O bond of PEG, resulting in the suppression of the intermolecular proton abstraction.

  8. Morphology of poly(ethylene oxide) dissolved in a room temperature ionic liquid: a small angle neutron scattering study.

    PubMed

    Triolo, Alessandro; Russina, Olga; Keiderling, Uwe; Kohlbrecher, Joachim

    2006-02-02

    Solutions of deuterated poly(ethylene oxide) (d-PEO) in 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF4]), a prototype room-temperature ionic liquid (RTIL), have been studied at room temperature over a range of polymer concentrations, using small angle neutron scattering (SANS), characterizing the conformation of PEO dissolved in RTILs. [bmim][BF4] behaves as a good solvent for d-PEO, which organizes in this solvent in non entangled random coils. These findings will help in optimizing the designing of microemulsions in these potentially environmentally friendly solvents.

  9. Synthesis of Diblock copolymer poly-3-hydroxybutyrate -block-poly-3-hydroxyhexanoate [PHB-b-PHHx] by a β-oxidation weakened Pseudomonas putida KT2442

    PubMed Central

    2012-01-01

    Background Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB) block covalently bonded with poly-3-hydroxyhexanoate (PHHx) block were for the first time produced successfully by a recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. Results The chloroform extracted polymers were characterized by nuclear magnetic resonance (NMR), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (Tg) at 2.7°C and −16.4°C, one melting temperature (Tm) at 172.1°C and one cool crystallization temperature (Tc) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. Conclusions It is possible to produce PHA block copolymers of various kinds using the recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. In comparison to a random copolymer poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P(HB-co-HHx)) and a blend sample of PHB and PHHx, the PHB-b-PHHx showed improved structural related mechanical properties. PMID:22480145

  10. Self-assembly in poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer template directed synthesis of Linde type A zeolite.

    PubMed

    Bonaccorsi, Lucio; Calandra, Pietro; Kiselev, Mikhail A; Amenitsch, Heinz; Proverbio, Edoardo; Lombardo, Domenico

    2013-06-11

    We describe the hydrothermal synthesis of zeolite Linde type A (LTA) submicrometer particles using a water-soluble amphiphilic block copolymer of poly(dimethylsiloxane)-b-poly(ethylene oxide) as a template. The formation and growth of the intermediate aggregates in the presence of the diblock copolymer have been monitored by small-angle X-ray scattering (SAXS) above the critical micellar concentration at a constant temperature of 45 °C. The early stage of the growth process was characterized by the incorporation of the zeolite LTA components into the surface of the block copolymer micellar aggregates with the formation of primary units of 4.8 nm with a core-shell morphology. During this period, restricted to an initial time of 1-3 h, the core-shell structure of the particles does not show significant changes, while a subsequent aggregation process among these primary units takes place. A shape transition of the SAXS profile at the late stage of the synthesis has been connected with an aggregation process among primary units that leads to the formation of large clusters with fractal characteristics. The formation of large supramolecular assemblies was finally verified by scanning electron microscopy, which evidenced the presence of submicrometer aggregates with size ranging between 100 and 300 nm, while X-ray diffraction confirmed the presence of crystalline zeolite LTA. The main finding of our results gives novel insight into the mechanism of formation of organic-inorganic mesoporous materials based on the use of a soft interacting nanotemplate as well as stimulates the investigation of alternative protocols for the synthesis of novel hybrid materials with new characteristics and properties.

  11. Mesoporous Silica Films with Long-Range Order Prepared from Strongly Segregated Block Copolymer/Homopolymer Blend Templates

    SciTech Connect

    Tirumala, Vijay R.; Pai, Rajaram A.; Agarwal, Sumit; Testa, Jason J.; Bhatnagar, Gaurav; Romang, Alvin H.; Chandler, Curran; Gorman, Brian P.; Jones, Ronald L.; Lin, Eric K.; Watkins, James J.

    2008-06-30

    Well-ordered mesoporous silica films were prepared by infusion and selective condensation of Si alkoxides within preorganized block copolymer/homopolymer blend templates using supercritical CO{sub 2} as the delivery medium. The morphologies of the mesoporous silica films reflect significant improvements in the strength of segregation and long-range order of template blends of poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymers with selectively associating homopolymers such as poly(acrylic acid) or poly(4-hydroxystyrene) prior as compared to templates comprised of the neat copolymer. Control over film porosity, pore ordering, and morphology of the films is achieved through simple variations in the homopolymer concentration. The films were characterized using X-ray reflectivity, small-angle X-ray scattering, and transmission electron microscopy.

  12. Diblock copolymers of polyethylene glycol and a polymethacrylamide with side-chains containing twin ortho ester rings: synthesis, characterization, and evaluation as potential pH-responsive micelles.

    PubMed

    Zhou, Xiaojing; Luo, Shi; Tang, Rupei; Wang, Rui; Wang, Jun

    2015-03-01

    The diblock copolymer, PEG-b-PMEA, was synthesized by reversible-addition fragmentation chain transfer polymerization (RAFT). The PMEA block contained a polymethacrylamide backbone and twin ortho ester rings in the side-chains. At neutral pH, PEG-b-PMEA self-assembled to form stable micelles. At pH 5, the twin ortho ester rings were quickly hydrolyzed to completion in 12 h, and releasing nearly 70% of the encapsulated Nile Red dye. The PEG-b-PMEA micelles were completely nontoxic to cultured cells as determined by the MTT assay. Paclitaxel (PTX)-loaded micelles showed toxicity toward lung cancer cells comparable to that of the free PTX at equivalent doses. These results suggest that the PEG-b-PMEA micelles could be useful nano-carriers for pH-responsive delivery of poorly soluble anticancer drugs.

  13. Star-shape redox-responsive PEG-sheddable copolymer of disulfide-linked polyethylene glycol-lysine-di-tocopherol succinate for tumor-triggering intracellular doxorubicin rapid release: head-to-head comparison.

    PubMed

    Ai, Xiaoyu; Sun, Jin; Zhong, Lu; Wu, Chunnuan; Niu, Handong; Xu, Tao; Lian, He; Han, Xiaopeng; Ren, Guolian; Ding, Wenya; Wang, Jia; Pu, Xiaohui; He, Zhonggui

    2014-10-01

    A redox-responsive poly(ethylene glycol) (PEG)-sheddable copolymer of disulfide-linked PEG 5000-lysine-di-tocopherol succinate (P(5k)SSLV) is developed which can self-assemble into nanomicelles in aqueous condition and trigger the rapid release of encapsulated drugs within tumor cells. The reduction-insensitive doxorubicin (DOX)-loaded P(5k)LV (P(5k)LV-DOX) nanomicelles are further prepared. Then head-to-head comparison of P(5k)SSLV-DOX, P(5k)LV-DOX and DOX-Sol is performed concerning in vitro release, cytotoxicity, cellular uptake and apoptosis. Results show that P(5k)SSLV-DOX nanomicelles have a faster DOX release, a higher anti-tumor activity and more DOX concentrating in the nucleus than P(5k)LV-DOX nanomicelles. In conclusion, the redox-responsive P(5k)SSLV nanomicelles might hold a great potential to improve chemotherapy by tumor-triggering intracellular rapid release. The outcomes of this study also address the significance of such head-to-head comparison studies in translational research of nanomedicine.

  14. High temperature proton exchange membranes with enhanced proton conductivities at low humidity and high temperature based on polymer blends and block copolymers of poly(1,3-cyclohexadiene) and poly(ethylene glycol)

    SciTech Connect

    Deng, Shawn; Hassan, Mohammad K.; Nalawade, Amol; Perry, Kelly A.; More, Karren L.; Mauritz, Kenneth A.; McDonnell, Marshall T.; Keffer, David J.; Mays, Jimmy W.

    2015-09-16

    Hot (at 120 °C) and dry (20% relative humidity) operating conditions benefit fuel cell designs based on proton exchange membranes (PEMs) and hydrogen due to simplified system design and increasing tolerance to fuel impurities. In this paper, presented are preparation, partial characterization, and multi-scale modeling of such PEMs based on cross-linked, sulfonated poly(1,3-cyclohexadiene) (xsPCHD) blends and block copolymers with poly(ethylene glycol) (PEG). These low cost materials have proton conductivities 18 times that of current industry standard Nafion at hot, dry operating conditions. Among the membranes studied, the blend xsPCHD-PEG PEM displayed the highest proton conductivity, which exhibits a morphology with higher connectivity of the hydrophilic domain throughout the membrane. Simulation and modeling provide a molecular level understanding of distribution of PEG within this hydrophilic domain and its relation to proton conductivities. Finally, this study demonstrates enhancement of proton conductivity at high temperature and low relative humidity by incorporation of PEG and optimized sulfonation conditions.

  15. High temperature proton exchange membranes with enhanced proton conductivities at low humidity and high temperature based on polymer blends and block copolymers of poly(1,3-cyclohexadiene) and poly(ethylene glycol)

    DOE PAGES

    Deng, Shawn; Hassan, Mohammad K.; Nalawade, Amol; ...

    2015-09-16

    Hot (at 120 °C) and dry (20% relative humidity) operating conditions benefit fuel cell designs based on proton exchange membranes (PEMs) and hydrogen due to simplified system design and increasing tolerance to fuel impurities. In this paper, presented are preparation, partial characterization, and multi-scale modeling of such PEMs based on cross-linked, sulfonated poly(1,3-cyclohexadiene) (xsPCHD) blends and block copolymers with poly(ethylene glycol) (PEG). These low cost materials have proton conductivities 18 times that of current industry standard Nafion at hot, dry operating conditions. Among the membranes studied, the blend xsPCHD-PEG PEM displayed the highest proton conductivity, which exhibits a morphology withmore » higher connectivity of the hydrophilic domain throughout the membrane. Simulation and modeling provide a molecular level understanding of distribution of PEG within this hydrophilic domain and its relation to proton conductivities. Finally, this study demonstrates enhancement of proton conductivity at high temperature and low relative humidity by incorporation of PEG and optimized sulfonation conditions.« less

  16. A hydrated phospholipid polymer-grafted layer prevents lipid-related oxidative degradation of cross-linked polyethylene.

    PubMed

    Kyomoto, Masayuki; Moro, Toru; Yamane, Shihori; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko

    2017-01-01

    The surface and substrate of a cross-linked polyethylene (CLPE) liner are designed to achieve resistance against oxidative degradation in the construction of hip joint replacements. In this study, we aimed to evaluate the oxidative degradation caused by lipid absorption of a highly hydrophilic nanometer-scaled thickness layer prepared by grafting a poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer and a high-dose gamma-ray irradiated CLPE with vitamin E blending (HD-CLPE[VE]). The HD-CLPE(VE) and PMPC-grafted HD-CLPE(VE) exhibited extremely high oxidation resistance regardless of lipid absorption, even though residual-free radical levels were detectable. The water wettability of the PMPC-grafted CLPE and PMPC-grafted HD-CLPE(VE) surfaces was considerably greater than that of untreated surfaces. The hydrated PMPC-grafted layer also exhibited extremely low solubility for squalene. Lipids such as squalene and cholesterol esters diminished the oxidation resistance of CLPE despite the vitamin E improvement. Notably, the PMPC-grafted surface was resistant to lipid absorption and diffusion as well as subsequent lipid-related oxidative degradation, likely because of the presence of the hydrated PMPC-grafted layer. Together, these results provide preliminary evidence that the resistance against lipid absorption and diffusion of a hydrated PMPC-grafted layer might positively affect the extent of resistance to the in vivo oxidation of orthopedic implants.

  17. Indium tin oxide films deposited by thermionic-enhanced DC magnetron sputtering on unheated polyethylene terephthalate polymer substrate

    SciTech Connect

    Lan, Y.F.; Peng, W.C.; Lo, Y.H.; He, J.L.

    2009-08-05

    Indium tin oxide thin films were deposited onto polyethylene terephthalate substrates via thermionic enhanced DC magnetron sputtering at low substrate temperatures. The structural, optical and electrical properties of these films are methodically investigated. The results show that compared with traditional sputtering, the films deposited with thermionic emission exhibit higher crystallinity, and their optical and electrical properties are also improved. Indium tin oxide films deposited by utilizing thermionic emission exhibit an average visible transmittance of 80% and an electrical resistivity of 4.5 x 10{sup -4} {Omega} cm, while films made without thermionic emission present an average visible transmittance of 74% and an electrical resistivity of 1.7 x 10{sup -3} {Omega} cm.

  18. Synthesis of eight-shaped poly(ethylene oxide) by the combination of Glaser coupling with ring-opening polymerization.

    PubMed

    Wang, Guowei; Fan, Xiaoshan; Hu, Bin; Zhang, Yannan; Huang, Junlian

    2011-10-18

    The eight-shaped poly(ethylene oxide) (PEO) is synthesized by a combination of Glaser coupling with ring-opening polymerization (ROP). Firstly, the star-shaped (PEO-OH)(4) is synthesized by ROP of ethylene oxide (EO) using pentaerythritol as an initiator and diphenylmethyl potassium (DPMK) as a deprotonated agent, and then the alkyne group is introduced onto the PEO arm-end to give (PEO-Alkyne)(4) in a NaH/tetrahydrofuran (THF) system. The intramolecular cyclization is carried out by a Glaser coupling reaction in a pyridine/CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) system at room temperature in an air atmosphere, and eight-shaped PEO was formed with high efficiency (almost 100%). The target polymers and intermediates were well characterized by SEC, MALDI-TOF MS, (1)H NMR and FT-IR in detail.

  19. Pluronic-P105 PEO-PPO-PEO block copolymer in aqueous urea solutions. Micelle formation, structure, and microenvironment

    SciTech Connect

    Alexandridis, P.; Athanassiou, V.; Hatton, T.A.

    1995-07-01

    The effects of urea on the micellization properties of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer (commercially available as Pluronic P105) and on the structure and microenvironment of the micelles are reported. Urea increased the critical micelle concentration (cmc) and critical micelle temperature (cmt) of the PEO-PPO-PEO copolymer; the effect of urea on the cmt was more pronounced at low copolymer concentrations and diminished at concentrations of nearly 2.5%. The surface activity and the partial specific volume of the block copolymer decreased with an increase in the urea concentration, whereas the hydrodynamic radii of the copolymer micelles, determined using dynamic light scattering, remained unaffected by the presence of 4 M urea in the solution. The micropolarity in copolymer solutions in urea/water was probed as a function of temperature using the I{sub 1}/I{sub 3} intensity ratio of the pyrene vibrational fine structure recorded in fluorescence emission spectra; a small decrease in the micropolarity of the micelle core was observed in the presence of urea. The microviscosity in the micelle interior, estimated from the intramolecular excimer fluorescence of the hydrophobic probe bis(1-pyrenylmethyl) ether (dipyme), also exhibited a small decrease with an increase in the urea concentration. 80 refs., 8 figs.

  20. Room-Temperature-Cured Copolymers for Lithium Battery Gel Electrolytes

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Tigelaar, Dean M.

    2009-01-01

    Polyimide-PEO copolymers (PEO signifies polyethylene oxide) that have branched rod-coil molecular structures and that can be cured into film form at room temperature have been invented for use as gel electrolytes for lithium-ion electric-power cells. These copolymers offer an alternative to previously patented branched rod-coil polyimides that have been considered for use as polymer electrolytes and that must be cured at a temperature of 200 C. In order to obtain sufficient conductivity for lithium ions in practical applications at and below room temperature, it is necessary to imbibe such a polymer with a suitable carbonate solvent or ionic liquid, but the high-temperature cure makes it impossible to incorporate and retain such a liquid within the polymer molecular framework. By eliminating the high-temperature cure, the present invention makes it possible to incorporate the required liquid.

  1. Protein Conjugation with Amphiphilic Block Copolymers for Enhanced Cellular Delivery

    PubMed Central

    Yi, Xiang; Batrakova, Elena; Banks, William A.; Vinogradov, Serguei; Kabanov, Alexander V.

    2008-01-01

    Modification of a model protein, horseradish peroxidase (HRP), with amphiphilic block copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronic), was previously shown to enhance the transport of this protein across the blood—brain barrier in vivo and brain microvessel endothelial cells in vitro. This work develops procedures for synthesis and characterization of HRP with Pluronic copolymers, having different lengths of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) blocks. Four monoamine Pluronic derivatives (L81, P85, L121, P123) were synthesized and successfully conjugated to a model protein, HRP, via biodegradable or nondegradable linkers (dithiobis(succinimidyl propionate) (DSP), dimethyl 3,3′-dithiobispropionimidate (DTBP), and disuccinimidyl propionate (DSS)). The conjugation was confirmed by HRP amino group titration, matrix-assisted laser desorption/ionization-time of flight spectroscopy, and cation-exchange chromatography. HRP conjugates containing an average of one to two Pluronic moieties and retaining in most cases over 70% of the activity were synthesized. Increased cellular uptake of these conjugates was demonstrated using the Mardin-Derby canine kidney cell line and primary bovine brain microvessel endothelial cells. The optimal modifications included Pluronic L81 and P85. These copolymers have shorter PPO chains compared to Pluronic P123 and L121, which were less efficient. There was little if any dependence of the uptake on the length of the hydrophilic PEO block for the optimal modifications. The proposed modifications may be used to increase cellular uptake of other proteins. PMID:18447367

  2. Analysis of long-term degradation behaviour of polyethylene mulching films with pro-oxidants under real cultivation and soil burial conditions.

    PubMed

    Briassoulis, Demetres; Babou, Epifaneia; Hiskakis, Miltiadis; Kyrikou, Ioanna

    2015-02-01

    Apart from the conventional polyethylene and the bio-based or mainly bio-based biodegradable in soil mulching films, polyethylene mulching films of controlled degradation in soil are already used in agriculture. The use of special pro-oxidants as additives is expected to accelerate the abiotic oxidation and the subsequent chain scission of the polymer under specific UV radiation or thermal degradation conditions, according to the literature. The role of pro-oxidants in the possible biodegradation of polyethylene has been theoretically supported through the use of controlled laboratory conditions. However, results obtained in real soil conditions, but also several laboratory test results, are not supporting these claims and the issue remains disputed. Mulching films made of linear low-density polyethylene (LLDPE) with pro-oxidants, after being used for one cultivation period in an experimental field with watermelon cultivation, were buried in the soil under real field conditions. This work presents the analysis of the degradation of the mulching films during the cultivation period as compared to the corresponding changes after a long soil burial period of 8.5 years. The combined effects of critical factors on the photochemical degradation of the degradable mulching LLDPE films with pro-oxidants under the cultivation conditions and their subsequent further degradation behaviour in the soil are analysed by testing their mechanical properties and through spectroscopic and thermal analysis.

  3. Sulfate-based anionic diblock copolymer nanoparticles for efficient occlusion within zinc oxide

    NASA Astrophysics Data System (ADS)

    Ning, Y.; Fielding, L. A.; Andrews, T. S.; Growney, D. J.; Armes, S. P.

    2015-04-01

    Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel nanocomposite materials with emergent properties. In the present paper, a series of new well-defined anionic diblock copolymer nanoparticles are synthesised by polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation and then evaluated as crystal habit modifiers for the in situ formation of ZnO in aqueous solution. Systematic studies indicate that both the chemical nature (i.e. whether sulfate-based or carboxylate-based) and the mean degree of polymerisation (DP) of the anionic stabiliser block play vital roles in determining the crystal morphology. In particular, sulfate-functionalised nanoparticles are efficiently incorporated within the ZnO crystals whereas carboxylate-functionalised nanoparticles are excluded, thus anionic character is a necessary but not sufficient condition for successful occlusion. Moreover, the extent of nanoparticle occlusion within the ZnO phase can be as high as 23% by mass depending on the sulfate-based nanoparticle concentration. The optical properties, chemical composition and crystal structure of the resulting nanocomposite crystals are evaluated and an occlusion mechanism is proposed based on the observed evolution of the ZnO morphology in the presence of sulfate-based anionic nanoparticles. Finally, controlled deposition of a 5 nm gold sol onto porous ZnO particles (produced after calcination of the organic nanoparticles) significantly enhances the rate of photocatalytic decomposition of a model rhodamine B dye on exposure to a relatively weak UV source.Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel

  4. Block copolymers for alkaline fuel cell membrane materials

    NASA Astrophysics Data System (ADS)

    Li, Yifan

    Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC

  5. MesoDyn simulation study on the phase morphologies of Miktoarm PEO-b-PMMA copolymer doped by nanoparticles

    NASA Astrophysics Data System (ADS)

    Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

    2013-03-01

    The compatibility of six groups of 12 miktoarm poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) copolymers is studied at 270, 298 and 400 K via mesoscopic modeling. The values of the order parameters depend on both the architectures of the block copolymers and the simulation temperature, while the tendency to change of the order parameters at low temperature, such as 270 and 298 K, is nearly the same. However, the values of order parameters of the copolymer in the same group are the same at high temperature, i.e. 400 K. Obviously, temperature has a more obvious effect on long and PEO-rich chains. A study of plain copolymers doped with nanoparticles shows that the microscopic phase is influenced by not only the properties of the nanoparticles, such as the size, number and density, but also the composition and architecture of copolymers. Increasing the size and the number of the nanoparticles used as a dopant plays the most significant role on determining the phase morphologies of the copolymers at lower and higher temperature, respectively. In paricular, the 23141 and 23241-type copolymers, which are both of PEO-rich composition, presents microscopic phase separation as perforated lamallae phase morphologies at 400 K, alternated with PEO and PMMA components.

  6. Suppression of cell and platelet adhesion to star-shaped 8-armed poly(ethylene glycol)-poly(L-lactide) block copolymer films.

    PubMed

    Nagahama, Koji; Ohya, Yuichi; Ouchi, Tatsuro

    2006-06-16

    To explore the potential of a star-shaped 8-armed poly(ethylene glycol)35K-block-poly(L-lactide)37K (8-armed PEG35K-b-PLLA37K: M(n) of PEG = 35 000, M(n) of PLLA = 37 000) film as a novel bioabsorbable adhesion-prevention membrane, the water structure, surface contact angle, protein adsorption, and cell and platelet anti-adhesion properties of such a hydrated film are investigated. Based on the results, it is found that the 8-armed PEG35K-b-PLLA37K film exhibits a biologically inert surface, which is the result of a large number of PEG chains and a free water layer on the film surface. This leads to a reduction in protein absorption and cell and platelet adhesion onto the film surface. This implies that the star-shaped 8-armed PEG35K-b-PLLA37K film can be utilized as a novel bioabsorbable adhesion-prevention membrane.

  7. Effect of water-soluble polymers, polyethylene glycol and poly(vinylpyrrolidone), on the gelation of aqueous micellar solutions of Pluronic copolymer F127.

    PubMed

    Ricardo, Nágila M P S; Ricardo, Nadja M P S; Costa, Flávia de M L L; Bezerra, Francisco W A; Chaibundit, Chiraphon; Hermida-Merino, Daniel; Greenland, Barnaby W; Burattini, Stefano; Hamley, Ian W; Keith Nixon, S; Yeates, Stephen G

    2012-02-15

    The micellization of F127 (E(98)P(67)E(98)) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (r(h,app)) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30 wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (G(max)(')) of 30 wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30 wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale.

  8. Oxidation and haem loss kinetics of poly(ethylene glycol)-conjugated haemoglobin (MP4): dissociation between in vitro and in vivo oxidation rates.

    PubMed

    Vandegriff, Kim D; Malavalli, Ashok; Minn, Charles; Jiang, Eva; Lohman, Jeff; Young, Mark A; Samaja, Michele; Winslow, Robert M

    2006-11-01

    Haemoglobin-based oxygen carriers can undergo oxidation of ferrous haemoglobin into a non-functional ferric form with enhanced rates of haem loss. A recently developed human haemoglobin conjugated to maleimide-activated poly(ethylene glycol), termed MP4, has unique physicochemical properties (increased molecular radius, high oxygen affinity and low cooperativity) and lacks the typical hypertensive response observed with most cell-free haemoglobin solutions. The rate of in vitro MP4 autoxidation is higher compared with the rate for unmodified SFHb (stroma-free haemoglobin), both at room temperature (20-22 degrees C) and at 37 degrees C (P<0.001). This appears to be attributable to residual catalase activity in SFHb but not MP4. In contrast, MP4 and SFHb showed the same susceptibility to oxidation by reactive oxygen species generated by a xanthine-xanthine oxidase system. Once fully oxidized to methaemoglobin, the rate of in vitro haem loss was five times higher in MP4 compared with SFHb in the fast phase, which we assign to the beta subunits, whereas the slow phase (i.e. haem loss from alpha chains) showed similar rates for the two haemoglobins. Formation of MP4 methaemoglobin in vivo following transfusion in rats and humans was slower than predicted by its first-order in vitro autoxidation rate, and there was no appreciable accumulation of MP4 methaemoglobin in plasma before disappearing from the circulation. These results show that MP4 oxidation and haem loss characteristics observed in vitro provide information regarding the effect of poly(ethylene glycol) conjugation on the stability of the haemoglobin molecule, but do not correspond to the oxidation behaviour of MP4 in vivo.

  9. In Vivo Oxidative Stability Changes of Highly Cross-Linked Polyethylene Bearings: An Ex Vivo Investigation.

    PubMed

    Rowell, Shannon L; Reyes, Christopher R; Malchau, Henrik; Muratoglu, Orhun K

    2015-10-01

    The development of highly cross-linked UHMWPEs focused on stabilizing radiation-induced free radicals as the sole precursor to oxidative degradation. However, secondary in vivo oxidation mechanisms have been discovered. After a preliminary post-operative analysis, we subjected highly cross-linked retrievals with 1-4 years in vivo durations and never-implanted controls to accelerated aging to predict the extent to which their oxidative stability was compromised in vivo. Lipid absorption, oxidation, and hydroperoxides were measured using infrared spectroscopy. Gravimetric swelling was used to measure cross-link density. After aging, all retrievals, except vitamin E-stabilized components, regardless of initial lipid levels or oxidation, showed significant oxidative degradation, demonstrated by subsurface oxidative peaks, increased hydroperoxides and decreased cross-link density, compared to their post-operative material properties and never-implanted counterparts, confirming oxidative stability changes.

  10. Miscibility of poly(lactic acid) and poly(ethylene oxide) solvent polymer blends and nanofibers made by solution blow spinning

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The miscibility of blends of poly(lactic acid) (PLA) and poly(ethylene oxide) (PEO) was studied in polymer solutions by dilute solution viscometry and in solution blow spun nanofibers by microscopy (SEM, TEM) and by thermal and spectral analysis. Three blends of PLA and PEO were solution blended in...

  11. Temperature dependence of the dielectric properties of metal-polymer composites based on zinc oxide nanoparticles stabilized in low-density polyethylene matrix

    NASA Astrophysics Data System (ADS)

    Ul'Zutuev, A. N.; Ushakov, N. M.

    2008-10-01

    We have studied the temperature dependence of the dielectric constant of composites based on low-density polyethylene and zinc oxide nanoparticles. Features related to the appearance of metastable states in the course of sequential heating-cooling cycles are revealed and mechanisms explaining this behavior are proposed.

  12. Conductivity and optical band gaps of polyethylene oxide doped with Li{sub 2}SO{sub 4} salt

    SciTech Connect

    Chapi, Sharanappa Raghu, S. Subramanya, K. Archana, K. Mini, V. Devendrappa, H.

    2014-04-24

    The conductivity and optical properties of Li{sub 2}SO{sub 4} doped polyethylene oxide (PEO) films were studied. The polymer electrolyte films are prepared using solution casting technique. The material phase change was confirmed by X-ray diffraction (XRD) technique. Optical absorption study was conducted using UV- Vis. Spectroscopy in the wavelength range 190–1100nm on pure and doped PEO films. The direct and indirect optical band gaps were found decreased from 5.81–4.51eV and 4.84–3.43eV respectively with increasing the Li{sub 2}SO{sub 4}. The conductivity found to increases with increasing the dopant concentration due to strong hopping mechanism at room temperature.

  13. High-density polyethylene facial implants show surface oxidation in SEM and EDX examination: a pilot study.

    PubMed

    Draenert, G F; Doeblinger, M; Draenert, M; Gosau, M

    2009-05-01

    Previous histopathological studies on explanted Medpor high-density polyethylene (HDPE) facial implants indicated signs of material destruction and claimed to observe phagocytized HDPE particles within the tissue samples beside the usual type IV reaction with severe fibrosis. We examined new and explanted Medpor material with scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The implant surface of three patient-derived specimens showed significantly higher oxygenation in EDX analysis and morphological changes in SEM compared to the new unused material directly after opening of the package and after 1 year of exposure to air. Our preliminary findings indicate a possible oxidative biocorrosion in HDPE surgical implants. Further studies should confirm these pilot project results.

  14. Composite poly(ethylene oxide) electrolytes plasticized by N-alkyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide for lithium batteries.

    PubMed

    Wetjen, Morten; Navarra, Maria Assunta; Panero, Stefania; Passerini, Stefano; Scrosati, Bruno; Hassoun, Jusef

    2013-06-01

    We report a new class of quaternary polymer electrolyte membranes that comprise poly(ethylene oxide) (PEO), lithium trifluoromethanesulfonylimide (LiTFSI), N-alkyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PyrA,4 TFSI) as an ionic liquid, and a SiO₂ filler. The results of differential scanning calorimetry indicate that the addition of SiO₂ and different ionic liquids induces a decrease in the PEO melting enthalpy, which thereby increases the ionic conductivity and the Li transference number. The electrochemical stability is proved by using impedance spectroscopy and cyclic voltammetry. Galvanostatic cycling of Li/LiFePO₄ cells, which comprise the quaternary polymer electrolytes, revealed their superior performance compared to conventional PEO-Li salt electrolytes. In the course of this investigation, a synergistic effect of the combined ionic liquid-ceramic filler modification could be proved at temperatures close to 50 °C.

  15. Synthesis and morphological change in poly(ethylene oxide)-sodium chlorate based polymer electrolyte complex with polyaniline

    NASA Astrophysics Data System (ADS)

    Kunteppa, H.; Roy, Aashis S.; Koppalkar, Anil R.; Ambika Prasad, M. V. N.

    2011-11-01

    The composites of polyethylene oxide:polyaniline:sodium chlorate is prepared by stirring with anhydrous acetonitrile for 5-6 h to form homogeneous solutions/gels at different weight percentages. The composites are characterized by FTIR and SEM. The predominant peaks that appeared in FTIR spectra confirm the formation of PEO:PANI:NaClO 4 composites. It is found from the SEM studies that there is a significant change in the morphology of various weight percentages of NaClO 4 in PEO-PANI matrix, i.e. from ellipsoidal to square. DC conductivity behavior is seen due to hopping of polarons from one localized state to another that can be confirmed by Mott theory. It is observed from the DC conductivity and SEM studies that these composites can be promising candidates for solid state electrolytes.

  16. Interface-enforced complexation between copolymer blocks.

    PubMed

    Steinschulte, Alexander A; Xu, Weinan; Draber, Fabian; Hebbeker, Pascal; Jung, Andre; Bogdanovski, Dimitri; Schneider, Stefanie; Tsukruk, Vladimir V; Plamper, Felix A

    2015-05-14

    Binary diblock copolymers and corresponding ternary miktoarm stars are studied at oil-water interfaces. All polymers contain oil-soluble poly(propylene oxide) PPO, water-soluble poly(dimethylaminoethyl methacrylate) PDMAEMA and/or poly(ethylene oxide) PEO. The features of their Langmuir compression isotherms are well related to the ones of the corresponding homopolymers. Within the Langmuir-trough, PEO-b-PPO acts as the most effective amphiphile compared to the other PPO-containing copolymers. In contrast, the compression isotherms show a complexation of PPO and PDMAEMA for PPO-b-PDMAEMA and the star, reducing their overall amphiphilicity. Such complex formation between the blocks of PPO-b-PDMAEMA is prevented in bulk water but facilitated at the interface. The weakly-interacting blocks of PPO-b-PDMAEMA form a complex due to their enhanced proximity in such confined environments. Scanning force microscopy and Monte Carlo simulations with varying confinement support our results, which are regarded as compliant with the mathematical random walk theorem by Pólya. Finally, the results are expected to be of relevance for e.g. emulsion formulation and macromolecular engineering.

  17. Mid-term survivorship and clinical outcomes of cobalt-chrome and oxidized zirconium on highly crosslinked polyethylene

    PubMed Central

    Petis, Stephen M.; Vasarhelyi, Edward M.; Lanting, Brent A.; Howard, James L.; Naudie, Douglas D.R.; Somerville, Lyndsay E.; McCalden, Richard W.

    2016-01-01

    Background The choice of bearing articulation for total hip arthroplasty in younger patients is amenable to debate. We compared mid-term patient-reported outcomes and survivorship across 2 different bearing articulations in a young patient cohort. Methods We reviewed patients with cobalt-chrome or oxidized zirconium on highly crosslinked polyethylene who were followed prospectively between 2004 and 2012. Kaplan–Meier analysis was used to determine predicted cumulative survivorship at 5 years with all-cause and aseptic revisions as the outcome. We compared patient-reported outcomes, including the Harris hip score (HHS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and Short-form 12 (SF-12) scores. Results A total of 622 patients were followed during the study period. Mean follow-up was 8.2 (range 2.0–10.6) years for cobalt-chrome and 7.8 (range 2.1–10.7) years for oxidized zirconium. Mean age was 54.9 ± 10.6 years for cobalt-chrome and 54.8 ± 10.7 years for oxidized zirconium. Implant survivorship was 96.0% (95% confidence interval [CI] 94.9%–97.1%) for cobalt-chrome and 98.7% (95% CI 98.0%–99.4%) for oxidized zirconium on highly crosslinked polyethylene for all-cause revisions, and 97.2% (95% CI 96.2%–98.2%) for cobalt-chrome and 99.0% (95% CI 98.4%–99.6%) for oxidized zirconium for aseptic revisions. An age-, sex- and diagnosis-matched comparison of the HHS, WOMAC and SF-12 scores demonstrated no significant changes in clinical outcomes across the groups. Conclusion Both bearing surface couples demonstrated excellent mid-term survivorship and outcomes in young patient cohorts. Future analyses on wear and costs are warranted to elicit differences between the groups at long-term follow-up. PMID:26812409

  18. In vitro evaluation of poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether copolymer coating effects on cells adhesion and proliferation

    NASA Astrophysics Data System (ADS)

    Rusen, Laurentiu; Neacsu, Patricia; Cimpean, Anisoara; Valentin, Ion; Brajnicov, Simona; Dumitrescu, L. N.; Banita, Janina; Dinca, Valentina; Dinescu, Maria

    2016-06-01

    Understanding and controlling natural and synthetic biointerfaces is known to be the key to a wide variety of application within cell culture and tissue engineering field. As both material characteristics and methods are important in tailoring biointerfaces characteristics, in this work we explore the feasibility of using Matrix Assisted Pulsed Laser Evaporation technique for obtaining synthetic copolymeric biocoatings (i.e. poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether) for evaluating in vitro Vero and MC3T3-E1 pre-osteoblasts cell response. Characterization and evaluation of the coated substrates were carried out using different techniques. The Fourier transform infrared spectroscopy data demonstrated that the main functional groups in the MAPLE-deposited films remained intact. Atomic Force Microscopy images showed the coatings to be continuous, with the surface roughness depending on the deposition parameters. Moreover, the behaviour of the coatings in medium mimicking the pH and temperature of the human body was studied and corelated to degradation. Spectro-ellipsometry (SE) and AFM measurements revealed the degradation trend during immersion time by the changes in coating thickness and roughness. In vitro biocompatibility was studied by indirect contact tests on Vero cells in accordance with ISO 10993-5/2009. The results obtained in terms of cell morphology (phase contrast microscopy) and cytotoxicity (LDH and MTT assays) proved biocompatibility. Furthermore, direct contact assays on MC3T3-E1 pre-osteoblasts demonstrated the capacity of all analyzed specimens to support cell adhesion, normal cellular morphology and growth.

  19. Polyether/Polyester Graft Copolymers

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L., Jr.; Wakelyn, N.; Stoakley, D. M.; Proctor, K. M.

    1986-01-01

    Higher solvent resistance achieved along with lower melting temperature. New technique provides method of preparing copolymers with polypivalolactone segments grafted onto poly (2,6-dimethyl-phenylene oxide) backbone. Process makes strong materials with improved solvent resistance and crystalline, thermally-reversible crosslinks. Resulting graft copolymers easier to fabricate into useful articles, including thin films, sheets, fibers, foams, laminates, and moldings.

  20. Effects of UV Aging on the Cracking of Titanium Oxide Layer on Poly(ethylene terephthalate) Substrate: Preprint

    SciTech Connect

    Zhang, Chao; Gray, Matthew H.; Tirawat, Robert; Larsen, Ross E.; Chen, Fangliang

    2016-04-18

    Thin oxide and metal films deposited on polymer substrates is an emerging technology for advanced reflectors for concentrated solar power applications, due to their unique combination of light weight, flexibility and inexpensive manufacture. Thus far, there is little knowledge on the mechanical integrity or structural persistence of such multi-layer thin film systems under long-term environmental aging. In this paper, the cracking of a brittle titanium dioxide layer deposited onto elasto-plastic poly(ethylene terephthalate) (PET) substrate is studied through a combination of experiment and modeling. In-situ fragmentation tests have been conducted to monitor the onset and evolution of cracks both on pristine and on samples aged with ultraviolet (UV) light. An analytical model is presented to simulate the cracking behavior and to predict the effects of UV aging. Based on preliminary experimental observation, the effect of aging is divided into three aspects and analyzed independently: mechanical property degradation of the polymer substrate; degradation of the interlayer between substrate and oxide coating; and internal stress-induced cracks on the oxide coating.

  1. Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

    PubMed

    Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

    2014-03-03

    Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein-polymer double-stabilized SPIONs for improving contrast in MRI. We used a cationic-neutral double hydrophilic poly(N-methyl-2-vinyl pyridinium iodide-block-poly(ethylene oxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement.

  2. Highly Asymmetric Phase Diagram of a Poly(1,2-octylene oxide)-Poly(ethylene oxide) Diblock Copolymer System Comprising a Brush-Like Poly(1,2-octylene oxide) Block.

    PubMed

    Hamley, Ian W; O'Driscoll, Ben M D; Lotze, Gudrun; Moulton, Claire; Allgaier, Jürgen; Frielinghaus, Henrich

    2009-12-16

    The phase diagram of a series of poly(1,2-octylene oxide)-poly(ethylene oxide) (POO-PEO) diblock copolymers is determined by small-angle X-ray scattering. The Flory-Huggins interaction parameter was measured by small-angle neutron scattering. The phase diagram is highly asymmetric due to large conformational asymmetry that results from the hexyl side chains in the POO block. Non-lamellar phases (hexagonal and gyroid) are observed near f(PEO)  = 0.5, and the lamellar phase is observed for f(PEO)  ≥ 0.5.

  3. Design of block copolymer templated solid state batteries

    NASA Astrophysics Data System (ADS)

    Bullock, Steven Edward

    The advent of portable electronics has placed a great demand on the power requirements of battery systems. High power batteries for small devices, such as cell phones, laptop computers, and personal data assistants (PDA's) have focused primarily on lithium ion batteries. With the introduction of large flexible panel displays, the need for a flexible battery system is apparent. Ring Opening Metathesis Polymerization (ROMP) is a facile method for synthesizing block copolymers with polar functional groups. These functional groups allow the formation of metal oxide clusters via a template of the microphase separated block copolymer domains. In this thesis, the synthesis of a flexible polymer battery system is described. Diblock copolymers of an ionically conductive unsaturated polyethylene oxide block with a carboxylic acid functionalized block were synthesized and characterized with NMR, IR and Gel Permeation Chromatography (GPC). Characterization of polymer templated LiMn2O 4 clusters and nanocomposites synthesized for the study have a distributed cluster morphology within the polymer matrix. The nanocomposites were analyzed with transmission electron microscopy to determine the morphology of the nanocomposites. Battery performance was characterized with cyclic voltammetry and galvanostatic charge/discharge cycling for power capacity. The ionic conductivity was measured with impedance spectroscopy. The novel room temperature templating strategy used for the synthesis of these ionically conductive nanocomposites requires no thermal cycling steps. This makes it attractive for processing of sheet structures to power flexible displays.

  4. One-step sonochemical synthesis of a graphene oxide-manganese oxide nanocomposite for catalytic glycolysis of poly(ethylene terephthalate)

    NASA Astrophysics Data System (ADS)

    Park, Gle; Bartolome, Leian; Lee, Kyoung G.; Lee, Seok Jae; Kim, Do Hyun; Park, Tae Jung

    2012-06-01

    Ultrasound-assisted synthesis of a graphene oxide (GO)-manganese oxide nanocomposite (GO-Mn3O4) was conducted without further modification of GO or employing secondary materials. With the GO nanoplate as a support, potassium permanganate oxidizes the carbon atoms in the GO support and gets reduced to Mn3O4. An intensive ultrasound method could reduce the number of reaction steps and temperature, enhance the reaction rate and furthermore achieve a Mn3O4 phase. The composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The coverage and crystallinity of Mn3O4 were controlled by changing the ratio of permanganate to GO dispersion. The synthesized nanocomposite was used as a catalyst for poly(ethylene terephthalate) (PET) depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET). The highest monomer yield of 96.4% was obtained with the nanocomposite containing the lowest amount of Mn3O4, while PET glycolysis with the Mn3O4 without GO yielded 82.7% BHET.Ultrasound-assisted synthesis of a graphene oxide (GO)-manganese oxide nanocomposite (GO-Mn3O4) was conducted without further modification of GO or employing secondary materials. With the GO nanoplate as a support, potassium permanganate oxidizes the carbon atoms in the GO support and gets reduced to Mn3O4. An intensive ultrasound method could reduce the number of reaction steps and temperature, enhance the reaction rate and furthermore achieve a Mn3O4 phase. The composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The coverage and crystallinity of Mn3O4 were controlled by changing the ratio of permanganate to GO dispersion. The synthesized nanocomposite was used as a catalyst for poly(ethylene

  5. Nanostructure in block copolymer solutions: Rheology and small-angle neutron scattering

    SciTech Connect

    Habas, Jean-Pierre; Pavie, Emmanuel; Perreur, Christelle; Lapp, Alain; Peyrelasse, Jean

    2004-12-01

    Triblock copolymers composed of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) present an amphiphilic character in aqueous solutions. Since PPO is less hydrophilic than PEO and since their solubilities decrease when the temperature increases, the copolymers self-assemble spontaneously, forming micelles at moderate temperatures. For higher temperatures or concentrations, the copolymers or the micelles are ordered because of repulsive interactions and form lyotropic liquid crystalline phases. These are phases of very great viscosity with the aspect of gels, and transitions between different crystalline phases can occur at fixed concentration during an increase of temperature. We studied solutions of three different copolymers. The first two have a star structure. They are both composed of four branches (EO){sub x}(PO){sub y} fixed on an ethylene diamine, but differ by the values of x and y. Their commercial name is Tetronic 908 (x=114, y=21) and Tetronic 704 (x=16, y=18). The third copolymer (EO){sub 37}(PO){sub 56}(EO){sub 37} is linear and is known under the name of Pluronic P105. The measurements of the shear complex elastic modulus according to the temperature is used to determine the temperatures of the different transitions. Then, small-angle neutron scattering on samples under flow and true crystallographic arguments make it possible to identify the nature of the crystalline phases. For the systems studied, we show that the branched copolymers form only one type of liquid crystalline phase, which is bcc for the T908 and lamellar for the T704. For the linear copolymer, it is possible to identify three transitions: micellar solution to hexagonal phase, hexagonal phase to body-centered cubic phase, and finally body-centered cubic phase to lamellar phase.

  6. Self-oscillating AB diblock copolymer developed by post modification strategy

    SciTech Connect

    Ueki, Takeshi E-mail: ryo@cross.t.u-tokyo.ac.jp; Onoda, Michika; Tamate, Ryota; Yoshida, Ryo E-mail: ryo@cross.t.u-tokyo.ac.jp; Shibayama, Mitsuhiro

    2015-06-15

    We prepared AB diblock copolymer composed of hydrophilic poly(ethylene oxide) segment and self-oscillating polymer segment. In the latter segment, ruthenium tris(2,2′-bipyridine) (Ru(bpy){sub 3}), a catalyst of the Belousov-Zhabotinsky reaction, is introduced into the polymer architecture based on N-isopropylacrylamide (NIPAAm). The Ru(bpy){sub 3} was introduced into the polymer segment by two methods; (i) direct random copolymerization (DP) of NIPAAm and Ru(bpy){sub 3} vinyl monomer and (ii) post modification (PM) of Ru(bpy){sub 3} with random copolymer of NIPAAm and N-3-aminopropylmethacrylamide. For both the diblock copolymers, a bistable temperature region (the temperature range; ΔT{sub m}), where the block copolymer self-assembles into micelle at reduced Ru(bpy){sub 3}{sup 2+} state whereas it breaks-up into individual polymer chain at oxidized Ru(bpy){sub 3}{sup 3+} state, monotonically extends as the composition of the Ru(bpy){sub 3} increases. The ΔT{sub m} of the block copolymer prepared by PM is larger than that by DP. The difference in ΔT{sub m} is rationalized from the statistical analysis of the arrangement of the Ru(bpy){sub 3} moiety along the self-oscillating segments. By using the PM method, the well-defined AB diblock copolymer having ΔT{sub m} (ca. 25 °C) large enough to cause stable self-oscillation can be prepared. The periodic structural transition of the diblock copolymer in a dilute solution ([Polymer] = 0.1 wt. %) is closely investigated in terms of the time-resolved dynamic light scattering technique at constant temperature in the bistable region. A macroscopic viscosity oscillation of a concentrated polymer solution (15 wt. %) coupled with the periodic microphase separation is also demonstrated.

  7. Superoxide dismutase and catalase conjugated to polyethylene glycol increases endothelial enzyme activity and oxidant resistance

    SciTech Connect

    Beckman, J.S.; Minor, R.L. Jr.; White, C.W.; Repine, J.E.; Rosen, G.M.; Freeman, B.A.

    1988-05-15

    Covalent conjugation of superoxide dismutase and catalase with polyethylene glycol (PEG) increases the circulatory half-lives of these enzymes from <10 min to 40 h, reduced immunogenicity, and decreases sensitivity to proteolysis. Because PEG has surface active properties and can induce cell fusion, the authors hypothesized that PEG conjugation could enhance cell binding and association of normally membrane-impermeable enzymes. Incubation of cultured porcine aortic endothelial cells with /sup 125/I-PEG-catalase or /sup 125/I-PEG-superoxide dismutase produced a linear, concentration-dependent increase in cellular enzyme activity and radioactivity. Fluorescently labeled PEG-superoxide dismutase incubated with endothelial cells showed a vesicular localization. Mechanical injury to cell monolayers, which is known to stimulate endocytosis, further increased the uptake of fluorescent PEG-superoxide dismutase. Addition of PEG and PEG-conjugated enzymes perturbed the spin-label binding environment, indicative of producing an increase in plasma membrane fluidity. Thus, PEG conjugation to superoxide dismutase and catalase enhances cell association of these enzymes in a manner which increases cellular enzyme activities and provides prolonged protection from partially reduced oxygen species.

  8. Disorder-to-order transitions induced by alkyne/azide click chemistry in diblock copolymer thin films.

    SciTech Connect

    Wei, X.; Gu, W.; Chen, W.; Shen, X.; Liu, F.; Strzalka, J. W.; Jiang, Z.; Russell, T. P.

    2012-01-01

    We investigated thin film morphologies of binary blends of alkyne-functionalized diblock copolymer poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) and Rhodamine B azide, where the thermal alkyne/azide click reaction between the two components induced a disorder-to-order transition (DOT) of the copolymer. By controlling the composition of the neat copolymers and the mole ratio between the alkyne and azide groups, different microphase separated morphologies were achieved. At higher azide loading ratios, a perpendicular orientation of the microdomains was observed with wide accessible film thickness window. As less azide was incorporated, the microdomains have a stronger tendency to be parallel to the substrate, and the film thickness window for perpendicular orientation also became narrower.

  9. Characterization of PEO-b-P(STFSILi) as a Single-Ion Block Copolymer Electrolyte for Lithium Batteries

    NASA Astrophysics Data System (ADS)

    Rojas, Adriana; Inceoglu, Sebnem; Balsara, Nitash

    2014-03-01

    Block copolymers containing a poly(ethylene oxide) (PEO) ion-conducting block and a polystyrene (PS) structural block mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt have been studied in the past as solid electrolytes for lithium batteries. However, transport of these ionic species result in concentration gradients during battery operation, and the energy expended by this process is inefficient. In other words, these electrolyte systems have low cation transference numbers. A single-ion block copolymer electrolyte has been synthesized where the TFSI anion of LiTFSI is covalently bound to the PS backbone. Li can dissociate from the immobilized anion, enabling the conduction of Li ions with a theoretical transference number of unity. AC impedance spectroscopy and small angle X-ray scattering are used to determine charge transport and morphological properties of these PEO-b-P(STFSILi) block copolymers over a range of molecular weights.

  10. Synthetic strategy for preparing chiral double-semicrystalline polyether block copolymers

    SciTech Connect

    McGrath, Alaina J.; Shi, Weichao; Rodriguez, Christina G.; Kramer, Edward J.; Hawker, Craig J.; Lynd, Nathaniel A.

    2014-12-11

    Here, we report an effective strategy for the synthesis of semi-crystalline block copolyethers with well-defined architecture and stereochemistry. As an exemplary system, triblock copolymers containing either atactic (racemic) or isotactic (R or S) poly(propylene oxide) end blocks with a central poly(ethylene oxide) mid-block were prepared by anionic ring-opening procedures. Stereochemical control was achieved by an initial hydrolytic kinetic resolution of racemic terminal epoxides followed by anionic ring-opening polymerization of the enantiopure monomer feedstock. The resultant triblock copolymers were highly isotactic (meso triads [mm]% ~ 90%) with optical microscopy, differential scanning calorimetry, wide angle x-ray scattering and small angle x-ray scattering being used to probe the impact of the isotacticity on the resultant polymer and hydrogel properties.

  11. Synthetic Strategy for Preparing Chiral Double-semicrystalline Polyether Block Copolymers

    PubMed Central

    McGrath, Alaina J.; Shi, Weichao; Rodriguez, Christina G.; Kramer, Edward J.

    2014-01-01

    We report an effective strategy for the synthesis of semi-crystalline block copolyethers with well-defined architecture and stereochemistry. As an exemplary system, triblock copolymers containing either atactic (racemic) or isotactic (R or S) poly(propylene oxide) end blocks with a central poly(ethylene oxide) mid-block were prepared by anionic ring-opening procedures. Stereochemical control was achieved by an initial hydrolytic kinetic resolution of racemic terminal epoxides followed by anionic ring-opening polymerization of the enantiopure monomer feedstock. The resultant triblock copolymers were highly isotactic (meso triads [mm]% ~ 90%) with optical microscopy, differential scanning calorimetry, wide angle x-ray scattering and small angle x-ray scattering being used to probe the impact of the isotacticity on the resultant polymer and hydrogel properties. PMID:25914726

  12. Synthetic strategy for preparing chiral double-semicrystalline polyether block copolymers

    DOE PAGES

    McGrath, Alaina J.; Shi, Weichao; Rodriguez, Christina G.; ...

    2014-12-11

    Here, we report an effective strategy for the synthesis of semi-crystalline block copolyethers with well-defined architecture and stereochemistry. As an exemplary system, triblock copolymers containing either atactic (racemic) or isotactic (R or S) poly(propylene oxide) end blocks with a central poly(ethylene oxide) mid-block were prepared by anionic ring-opening procedures. Stereochemical control was achieved by an initial hydrolytic kinetic resolution of racemic terminal epoxides followed by anionic ring-opening polymerization of the enantiopure monomer feedstock. The resultant triblock copolymers were highly isotactic (meso triads [mm]% ~ 90%) with optical microscopy, differential scanning calorimetry, wide angle x-ray scattering and small angle x-ray scatteringmore » being used to probe the impact of the isotacticity on the resultant polymer and hydrogel properties.« less

  13. Cyclic block copolymers for controlling feature sizes in block copolymer lithography.

    PubMed

    Poelma, Justin E; Ono, Kosuke; Miyajima, Daigo; Aida, Takuzo; Satoh, Kotaro; Hawker, Craig J

    2012-12-21

    Block copolymer lithography holds promise as a next-generation technique to achieve the sub-20 nm feature sizes demanded by semiconductor roadmaps. While molecular weight and block immiscibility have traditionally been used to control feature size, this study demonstrates that macromolecular architecture is also a powerful tool for tuning domain spacing. To demonstrate this concept, a new synthetic strategy for cyclic block polymers based on highly efficient "click" coupling of difunctional linear chains is developed, and the thin film self-assembly of cyclic polystyrene-block-polyethylene oxide (cPS-b-PEO) is compared with the corresponding linear analogues. The reduced hydrodynamic radii of the cyclic systems result in ~30% decrease in domain spacing over the corresponding linear polymers.

  14. Polyethylene glycol modified, cross-linked starch-coated iron oxide nanoparticles for enhanced magnetic tumor targeting.

    PubMed

    Cole, Adam J; David, Allan E; Wang, Jianxin; Galbán, Craig J; Hill, Hannah L; Yang, Victor C

    2011-03-01

    While successful magnetic tumor targeting of iron oxide nanoparticles has been achieved in a number of models, the rapid blood clearance of magnetically suitable particles by the reticuloendothelial system (RES) limits their availability for targeting. This work aimed to develop a long-circulating magnetic iron oxide nanoparticle (MNP) platform capable of sustained tumor exposure via the circulation and, thus, potentially enhanced magnetic tumor targeting. Aminated, cross-linked starch (DN) and aminosilane (A) coated MNPs were successfully modified with 5 kDa (A5, D5) or 20 kDa (A20, D20) polyethylene glycol (PEG) chains using simple N-Hydroxysuccinimide (NHS) chemistry and characterized. Identical PEG-weight analogues between platforms (A5 & D5, A20 & D20) were similar in size (140-190 nm) and relative PEG labeling (1.5% of surface amines - A5/D5, 0.4% - A20/D20), with all PEG-MNPs possessing magnetization properties suitable for magnetic targeting. Candidate PEG-MNPs were studied in RES simulations in vitro to predict long-circulating character. D5 and D20 performed best showing sustained size stability in cell culture medium at 37 °C and 7 (D20) to 10 (D5) fold less uptake in RAW264.7 macrophages when compared to previously targeted, unmodified starch MNPs (D). Observations in vitro were validated in vivo, with D5 (7.29 h) and D20 (11.75 h) showing much longer half-lives than D (0.12 h). Improved plasma stability enhanced tumor MNP exposure 100 (D5) to 150 (D20) fold as measured by plasma AUC(0-∞). Sustained tumor exposure over 24 h was visually confirmed in a 9L-glioma rat model (12 mg Fe/kg) using magnetic resonance imaging (MRI). Findings indicate that a polyethylene glycol modified, cross-linked starch-coated MNP is a promising platform for enhanced magnetic tumor targeting, warranting further study in tumor models.

  15. Development of Iron-Chelating Poly(ethylene terephthalate) Packaging for Inhibiting Lipid Oxidation in Oil-in-Water Emulsions.

    PubMed

    Johnson, David R; Tian, Fang; Roman, Maxine J; Decker, Eric A; Goddard, Julie M

    2015-05-27

    Foods such as bulk oils, salad dressings, and nutritionally fortified beverages that are susceptible to oxidative degradation are often packaged in poly(ethylene terephthalate) (PET) bottles with metal chelators added to the food to maintain product quality. In the present work, a metal-chelating active packaging material is designed and characterized, in which poly(hydroxamic acid) (PHA) metal-chelating moieties were grafted from the surface of PET. Biomimetic PHA groups were grafted in a two-step UV-initiated process without the use of a photoinitiator. Surface characterization of the films by attenuated total reflective Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) suggested successful grafting and conversion of poly(hydroxyethyl acrylate) (PHEA) to PHA chelating moieties from the surface of PET. Colorimetric (ferrozine) and inductively coupled plasma mass spectroscopy (ICP-MS) assays demonstrated the ability of PET-g-PHA to chelate iron in a low-pH (3.0) environment containing a competitive metal chelator (citric acid). Lipid oxidation studies demonstrated the antioxidant activity of PET-g-PHA films in inhibiting iron-promoted oxidation in an acidified oil-in-water (O/W) emulsion model system (pH 3.0). Particle size and ζ-potential analysis indicated that the addition of PET-g-PHA films did not affect the physical stability of the emulsion system. This work suggests that biomimetic chelating moieties can be grafted from PET and effectively inhibit iron-promoted degradation reactions, enabling removal of metal-chelating additives from product formulations.

  16. Oxidized polyethylene films for orienting polar molecules for linear dichroism spectroscopy.

    PubMed

    Razmkhah, Kasra; Chmel, Nikola Paul; Gibson, Matthew I; Rodger, Alison

    2014-03-21

    Stretched polyethylene (PE) films have been used to orient small molecules for decades by depositing solutions on their surface and allowing the solvent to evaporate leaving the analyte absorbed on the polymer film. However, the non-polar hydrophobic nature of PE is an obstacle to aligning polar molecules and biological samples. In this work PE film was treated with oxygen plasma in order to increase surface hydrophilicity. Different treatment conditions were evaluated using contact angle measurement and X-ray photoelectron spectroscopy. Treated PE (PE(OX)) films are shown to be able to align molecules of different polarities including progesterone, 1-pyrenecarboxaldehyde, 4',6-diamidino-2-phenylindole (DAPI) and anthracene. The degree of alignment of each molecule was studied by running series of linear dichroism (LD) experiments and the polarizations of electronic transition moments were determined. For the first time optimal conditions (such as stretching factor and concentration of the sample) for stretched film LD were determined. PE(OX) aligning ability was compared to that of normal PE films. Progesterone showed a slightly better alignment on PE(OX) than PE. 1-Pyrenecarboxaldehyde oriented differently on the two different films which enabled transition moment assignment for this low symmetry molecule. DAPI (which does not align on PE) aligned well on PE(OX) and enabled us to obtain better LD data than had previously been collected with polyvinyl alcohol. Anthracene alignment and formation of dimers and higher order structures were studied in much more detail than previously possible, showing a variety of assemblies on PE and PE(OX) films.

  17. Segmental Dynamics and Dielectric Constant of Polysiloxane Polar Copolymers as Plasticizers for Polymer Electrolytes.

    PubMed

    Choi, U Hyeok; Liang, Siwei; Chen, Quan; Runt, James; Colby, Ralph H

    2016-02-10

    Dielectric relaxation spectroscopy was used to investigate the segmental dynamics of a series of siloxane-based polar copolymers combining pendant cyclic carbonates and short poly(ethylene oxide) (PEO) chains. The homopolymer with cyclic carbonate as the only side chain exhibits higher glass transition temperature T(g) and dielectric constant ε(s) than the one with only PEO side chains. For their copolymers the observed T(g) (agreeing well with the predicted values from the Fox equation) and ε(s) decrease with increasing PEO side chain content. These polar polymers exhibit a glassy β relaxation with Arrhenius character, attributed to local chain motions of side groups attached to the main chain, and a segmental α relaxation, associated with the glass transition with a Vogel temperature dependence. As PEO side chain content increases, narrowing of the local glassy β relaxation was observed in the copolymers. The segmental α dynamics were observed to be faster, with an increase in breadth and decrease in strength with increasing PEO side chain content. Owing to the trade-off between T(g) and ε(s), copolymers of intermediate composition result in the highest ionic conductivity when these copolymers are used to plasticize Li single-ion conducting ionomers.

  18. Phase behavior in blends of ethylene oxide-propylene oxide copolymer and poly(ether sulfone) studied by modulated-temperature DSC and NMR relaxometry.

    PubMed

    Van Lokeren, Luk; Gotzen, Nicolaas-Alexander; Pieters, Ronny; Van Assche, Guy; Biesemans, Monique; Willem, Rudolph; Van Mele, Bruno

    2009-01-01

    The state diagram of a blend consisting of a copolymer containing ethylene oxide and propylene oxide, P(EO-ran-PO), and poly(ether sulfone), PES, is constructed by using modulated-temperature differential scanning calorimetry (MTDSC), T(2) NMR relaxometry, and light scattering. The apparent heat capacity signal in MTDSC is used for the characterization of polymer miscibility and morphology development. T(2) NMR relaxometry is used to detect the onset of phase separation, which is in good agreement with the onset of phase separation in the apparent heat capacity from MTDSC and the cloud-point temperature as determined from light scattering. The coexistence curve can be constructed from T(2) values at various temperatures by using a few blends with well-chosen compositions. These T(2) values also allow the detection of the boundary between the demixing zones with and without interference of partial vitrification and are in good agreement with stepwise quasi-isothermal MTDSC heat capacity measurements. Important interphases are detected in the heterogeneous P(EO-ran-PO)/PES blends.

  19. Characterization and Antimicrobial Activity of N-Methyl-2-pyrrolidone-loaded Ethylene Oxide-Propylene Oxide Block Copolymer Thermosensitive Gel

    PubMed Central

    Phaechamud, T.; Mahadlek, J.; Charoenteeraboon, J.; Choopun, S.

    2012-01-01

    The purpose of this study is to investigate the effects of N-methyl-2-pyrrolidone on the thermosensitive properties of aqueous ethylene oxide-propylene oxide block copolymer (Lutrol® F127) system. Due to the aqueous solubility enhancement and biocompatibility, N-methyl-2-pyrrolidone is an interesting solubilizer for the poorly water soluble drugs to be incorporated in the Lutrol® F127 system. Effect of N-methyl-2-pyrrolidone on physicochemical properties of Lutrol® F127 system was investigated using appearance, pH, gelation, gel melting temperature and rheology. The antimicrobial activity of the thermosensitive N-methyl-2-pyrrolidone gel was also tested. Lower N-methyl-2-pyrrolidone amount (≤30%w/w) could shift the sol-gel transition to a lower temperature but the gel-sol transition was shifted to a higher temperature. Higher N-methyl-2-pyrrolidone (≥40%w/w) could shift both sol-gel and gel-sol transitions of the system to a lower temperature. The amount of N-methyl-2-pyrrolidone >60% w/w could reverse the phase of the Lutrol® F127 system to non-newtonian flow at 4° and Newtonian flow at high temperature. Aqueous Lutrol® F127 system containing N-methyl-2-pyrrolidone exhibited antimicrobial activities against Staphylococcus aureus, Escherichia coli and Candida albicans with the N-methyl-2-pyrrolidone in a dose-dependent manner. PMID:23798774

  20. pH-Responsive chimaeric pepsomes based on asymmetric poly(ethylene glycol)-b-poly(l-leucine)-b-poly(l-glutamic acid) triblock copolymer for efficient loading and active intracellular delivery of doxorubicin hydrochloride.

    PubMed

    Chen, Peipei; Qiu, Min; Deng, Chao; Meng, Fenghua; Zhang, Jian; Cheng, Ru; Zhong, Zhiyuan

    2015-04-13

    pH-Responsive chimaeric polypeptide-based polymersomes (refer to as pepsomes) were designed and developed from asymmetric poly(ethylene glycol)-b-poly(l-leucine)-b-poly(l-glutamic acid) (PEG-PLeu-PGA, PEG is longer than PGA) triblock copolymers for efficient encapsulation and triggered intracellular delivery of doxorubicin hydrochloride (DOX·HCl). PEG-PLeu-PGA was conveniently prepared by sequential ring-opening polymerization of l-leucine N-carboxyanhydride and γ-benzyl-l-glutamate N-carboxyanhydride using PEG-NH2 as an initiator followed by deprotection. Pepsomes formed from PEG-PLeu-PGA had unimodal distribution and small sizes of 64-71 nm depending on PLeu block lengths. Interestingly, these chimaeric pepsomes while stable at pH 7.4 were quickly disrupted at pH 5.0, likely due to alternation of ionization state of the carboxylic groups in PGA that shifts PGA blocks from hydrophilic and random coil structure into hydrophobic and α-helical structure. DOX·HCl could be actively loaded into the watery core of pepsomes with a high loading efficiency. Remarkably, the in vitro release studies revealed that release of DOX·HCl was highly dependent on pH, in which about 24.0% and 75.7% of drug was released at pH 7.4 and 5.0, respectively, at 37 °C in 24 h. MTT assays demonstrated that DOX·HCl-loaded pepsomes exhibited high antitumor activity, similar to free DOX·HCl in RAW 264.7 cells. Moreover, they were also potent toward drug-resistant MCF-7 cancer cells (MCF-7/ADR). Confocal microscopy studies showed that DOX·HCl-loaded pepsomes delivered and released drug into the cell nuclei of MCF-7/ADR cells in 4 h, while little DOX·HCl fluorescence was observed in MCF-7/ADR cells treated with free drug under otherwise the same conditions. These chimaeric pepsomes with facile synthesis, efficient drug loading, and pH-triggered drug release behavior are an attractive alternative to liposomes for targeted cancer chemotherapy.

  1. Radiation-induced oxidation of ultra-high molecular weight polyethylene (UHMWPE) powder by gamma rays and electron beams: A clear dependence of dose rate

    NASA Astrophysics Data System (ADS)

    Wang, Honglong; Xu, Lu; Hu, Jiangtao; Wang, Mouhua; Wu, Guozhong

    2015-10-01

    Oxidation is an important effect of irradiation on polyethylene in air. In this work, oxidation of ultra-high molecular weight polyethylene (UHMWPE) powder (ca. 110 μm in diameter) induced by gamma rays (γ ray) and electron beams (EB) in air resulted in some large differences in properties, such as oxidative scission due to dose rate differences. However, other properties, such as surface wettability and thermal stability were not that greatly affected. The dose-rates used were 0.0019 kGy/s from a cobalt-60 gamma source and 92 kGy/s from an electron beam. The chemical structure, oxidation level, surface wettability and thermal stability of irradiated UHMWPE were analyzed by FT-IR, XPS, TGA and the static contact angle. Hydrophilic carboxyl and carbonyl groups were present on the surface of irradiated UHMWPE after irradiation in air, resulting in a decrease in the contact angle. After irradiation at 300 kGy, the gel content of the γ ray-irradiated UHMWPE samples decreased to almost zero, while that of EB irradiated UHMWPE decreased to 57%. For UHMWPE powder irradiated by gamma rays at lower doses, radiation-induced oxidation was complete and consistent with a simple theoretic estimation. Surface wettability was primarily affected by surface oxidation, and the oxidation level of UHMWPE could be easily predicted.

  2. Effect of the nature of the counterion on the interaction between cesium and tetraalkylammonium dodecylsulfates and poly(ethylene oxide) or poly(vinylpyrolidone).

    PubMed

    Benrraou, Mohamed; Bales, Barney; Zana, Raoul

    2003-11-15

    The interaction between poly(ethylene oxide) or poly(vinylpyrrolidone) and cesium and tetraalkylammonium (tetramethyl to tetrabutyl ammonium) dodecylsulfate has been investigated by means of electrical conductivity measurements to determine the critical aggregation concentration (cac) of the surfactants in the presence of polymer. The cac values were compared to the values of the critical micellization concentration (cmc) of the surfactants in the absence of polymer. The value of the cac/cmc ratio increased with the radius of the counterion in the sequence: Na(+)poly(ethylene oxide) or poly(vinylpyrrolidone).

  3. Charge transport and glassy dynamics of poly(ethylene oxide)-based single-ion conductors under geometrical confinement

    NASA Astrophysics Data System (ADS)

    Runt, James; Iacob, Ciprian

    2015-03-01

    Segmental and local dynamics as well as charge transport are investigated in a series of poly(ethylene oxide)-based single-ion conductors (ionomers) with varying counterions (Li +, Na +) confined in uni-directional nanoporous silica membranes. The dynamics are explored over a wide frequency and temperature range by broadband dielectric relaxation spectroscopy. Slowing of segmental dynamics and a decrease in dc conductivity (strongly coupled with segmental relaxation) of the confined ionomers are associated with surface effects - resulting from interfacial hydrogen bonding between the host nanoporous silica membrane and the guest ionomers. These effects are significantly reduced or eliminated upon pore surface modification through silanization. The primary transport properties for the confined ionomers decrease by about one decade compared to the bulk ionomer. A model assuming reduced mobility of an adsorbed layer at the pore wall/ionomer interface is shown to provide a quantitative explanation for the decrease in effective transport quantities in non-silanized porous silica membranes. Additionally, the effect of confinement on ion aggregation in ionomers by using X-ray scattering will also be discussed. Supported by the National Science Foundation, Polymers Program.

  4. Synthesis of silica chemically bonded with poly(ethylene oxide) 4-arm, amine-terminated for copper cation removal.

    PubMed

    Kurczewska, Joanna; Schroeder, Grzegorz

    2010-12-01

    Chemically modified silica containing a poly(ethylene oxide) 4-arm, amine-terminated unit has been obtained in the multi-step synthesis. The synthesized material was characterized by elemental, thermogravimetric analysis and infrared spectroscopy. The surface morphology was analyzed by scanning electron microscopy. The support studied was applied for selective extraction of copper(II) [Cu(II)] from water solutions. The influence of different parameters (pH, amount of the support studied, and contact time) on the copper extraction was investigated. At the optimum conditions, the copper extraction was approximately 90%, significantly greater than that of the other coexisting ions--nickel(II) [Ni(II)], cobalt(II) [Co(II)], and manganese(II) [Mn(II)]. The exception was calcium(II) [Ca(II)], which reached 30% of the extraction percentage. The solid support retained its properties after treatment with different organic and inorganic solvents. The recovery of adsorbed Cu(II) ions was approximately 97%. The sorbent studied can be applied effectively for the pre-concentration of a low level of Cu(II) in the different water samples.

  5. Effects of 12-Crown-4 ether on the ionic conductivity and electrode kinetics of electrolytes in polyethylene oxide

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.

    1990-01-01

    Results are described of investigations of the electrical and electrochemical properties of thin films of polyethylene oxide (PEO) electrolytes with and without 12-Crown-4 ether (12Cr4) as a function of temperature and in the frequency regime 100 kHz-0.1 Hz. These measurements were made for LiCF3SO3, LiBF4, and LiClO4 salts. At a given temperature, the bulk conductivity, sigma, (S/cm), for a particular salt, depends on the 12Cr4 concentration with sigma reaching a maximum at about 3 mM 12Cr4. Of the three salts studied, the sigma is the highest for PEO/LiBF4 with 3 mM 12Cr4. The ac and dc measurements yield a lower charge transfer resistance for 12Cr4-incorporated samples than for samples without. Plating/stripping of Li occurs at a potential closer to Li(+)/Li for 12Cr4 samples than those without. The conductivities of a thin (about 100 microns) and a thick (400 microns) films are similar.

  6. Dielectric and mechanical investigations on the hydrophilicity and hydrophobicity of polyethylene oxide modified on a silicon surface

    SciTech Connect

    Shang, Jing; Hong, Kunlun; Wang, Tao; Zhu, Dan; Shen, Jian

    2016-10-02

    Here, polyethylene oxide (PEO) has been widely used in biomedical fields. The antibiofouling property of the PEO-modified surface has been extensively investigated but is far from being fully understood. A series of PEOs with narrowly distributed molecular weight (Mw), synthesized with the technique of high vacuum anionic polymerization, have been successfully grafted onto the surface of silicon wafers. The power-law relationship between the thickness of the monolayer versus the Mw of the grafted PEO shows a scaling of 0.3, indicating compact condensing of the chains. The static contact angles show higher hydrophobicity for the layer of PEO with higher Mw, which can be attributed to the closely packed conformation of the chains with high density. The frequency shift of the contact resonance indicates that the Young’s modulus decreases and the loss factor increases with the increase in the Mw of PEO and the thickness of the PEO layers. Dielectric spectroscopy of bare or PEO-grafted wafers in the aqueous solutions reveals an interfacial polarization, which results from compositional and structural changes in the interface layer and depends on temperatures and salt concentrations. At a given grafting density, the PEO chains are swollen in pure water, demonstrating hydrophilic behavior, whereas they collapse in salt solutions, showing hydrophobic characteristics.

  7. Nuclear magnetic resonance investigation of dynamics in poly(ethylene oxide)-based lithium polyether-ester-sulfonate ionomers

    SciTech Connect

    Roach, David J.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

    2012-01-06

    Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies for motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though their respective correlation times differ significantly. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments.

  8. Surfactant-assisted intercalation of high molecular weight poly(ethylene oxide) into vanadyl phosphate di-hydrate

    SciTech Connect

    Ferreira, Joao Paulo L.; Oliveira, Herenilton P.

    2012-03-15

    Graphical abstract: CuK{sub {alpha}} X-ray diffraction patterns of the VOPO{sub 4}/PEO (A) e VOPO{sub 4}/CTA (B) and VOPO{sub 4}/CTA/PEO (C). Highlights: Black-Right-Pointing-Pointer VOPO{sub 4}/PEO has been synthesized by using CTAB, thereby improving PEO intercalation. Black-Right-Pointing-Pointer The d-spacing increase from 1.30 nm (VOPO{sub 4}/PEO) to 2.94 nm (VOPO{sub 4}/CTA/PEO). Black-Right-Pointing-Pointer This strategy was viable for intercalation of PEO with high molecular weight. -- Abstract: A high molecular weight poly(ethylene oxide)/layered vanadyl phosphate di-hydrate intercalation compound was synthesized via the surfactant-assisted approach. Results confirmed that surfactant molecules were replaced with the polymer, while the lamellar structure of the matrix was retained, and that the material presents high specific surface area. In addition, intercalation produced a more thermally stable polymer as evidenced by thermal analysis.

  9. Dielectric and Mechanical Investigations on the Hydrophilicity and Hydrophobicity of Polyethylene Oxide Modified on a Silicon Surface.

    PubMed

    Shang, Jing; Hong, Kunlun; Wang, Tao; Zhu, Dan; Shen, Jian

    2016-11-08

    Polyethylene oxide (PEO) has been widely used in biomedical fields. The antibiofouling property of the PEO-modified surface has been extensively investigated but is far from being fully understood. A series of PEOs with narrowly distributed molecular weight (Mw), synthesized with the technique of high vacuum anionic polymerization, have been successfully grafted onto the surface of silicon wafers. The power-law relationship between the thickness of the monolayer versus the Mw of the grafted PEO shows a scaling of 0.3, indicating compact condensing of the chains. The static contact angles show higher hydrophobicity for the layer of PEO with higher Mw, which can be attributed to the closely packed conformation of the chains with high density. The frequency shift of the contact resonance indicates that the Young's modulus decreases and the loss factor increases with the increase in the Mw of PEO and the thickness of the PEO layers. Dielectric spectroscopy of bare or PEO-grafted wafers in the aqueous solutions reveals an interfacial polarization, which results from compositional and structural changes in the interface layer and depends on temperatures and salt concentrations. At a given grafting density, the PEO chains are swollen in pure water, demonstrating hydrophilic behavior, whereas they collapse in salt solutions, showing hydrophobic characteristics.

  10. Poly(ethylene oxide) irradiated in the solid state, melt and aqueous solution—a DSC and WAXD study

    NASA Astrophysics Data System (ADS)

    Jurkin, Tanja; Pucić, Irina

    2012-09-01

    Interactions of the aggregate state of poly(ethylene oxide), PEO, and γ-irradiation conditions (total dose, atmosphere) on its thermal and crystalline properties were investigated by DSC and WAXD taking into account sample molecular mass and form. In PEO irradiated in the solid state and in the presence of oxygen, chain scission dominated over concurrent crosslinking up to 200 kGy, particularly in PEO powders, due to a large surface being in contact with air. In solid samples the degree of crystallinity and crystallite size increased with the dose up to 50 kGy, probably not just due to partial crystallization upon degradation of amorphous phase, but to recrystallization of broken tie molecules. The least changes in crystallinity and phase transformation temperatures occurred in solid films. A substantial decrease in crystallinity and transformation temperatures without the initial crystallinity increase was achieved in samples that were amorphous on irradiation, at temperatures above the PEO melting temperature and in aqueous solutions. Radiation crosslinking of the PEO aqueous solution in an inert atmosphere is the most suitable way to obtain a lower degree of crystallinity and phase transformation temperatures while preserving mechanical properties.

  11. Increased bioavailability of primaquine using poly(ethylene oxide) matrix extended-release tablets administered to beagle dogs

    PubMed Central

    Bertol, C D; Oliveira, P R; Kuminek, G; Rauber, G S; Stulzer, H K; Silva, M A S

    2011-01-01

    Primaquine (PQ) is used for the radical cure of Plasmodium vivax malaria and can cause serious side effects in some individuals. The development of an extended-release dosage with poly(ethylene oxide) as a hydrophilic polymer has been investigated to improve drug efficacy and tolerability. The aim of this study was to evaluate in vivo a new extended-release formulation of PQ (60 mg). The formulation was administered to beagle dogs and plasma PQ concentrations were compared to a conventional immediate-release formulation of PQ (60 mg). The evaluation was carried out using a validated high-performance liquid chromatography method using solid-phase extraction. Total PQ exposure in beagle dogs was 2.2 times higher (area under curve of 12 193 versus 5678 ng h/ml) and the elimination half-life of PQ was a 19-fold greater (12.95 hours versus 0.68 hours) with the extended-release tablets compared with the immediate-release tablets. These findings suggest that the extended-release formulation of PQ merits further evaluation for the treatment of P. vivax malaria and/or chemoprophylaxis. PMID:22185941

  12. A comparison of united atom, explicit atom, and coarse-grained simulation models for poly(ethylene oxide).

    PubMed

    Chen, Chunxia; Depa, Praveen; Sakai, Victoria García; Maranas, Janna K; Lynn, Jeffrey W; Peral, Inmaculada; Copley, John R D

    2006-06-21

    We compare static and dynamic properties obtained from three levels of modeling for molecular dynamics simulation of poly(ethylene oxide) (PEO). Neutron scattering data are used as a test of each model's accuracy. The three simulation models are an explicit atom (EA) model (all the hydrogens are taken into account explicitly), a united atom (UA) model (CH(2) and CH(3) groups are considered as a single unit), and a coarse-grained (CG) model (six united atoms are taken as one bead). All three models accurately describe the PEO static structure factor as measured by neutron diffraction. Dynamics are assessed by comparison to neutron time of flight data, which follow self-motion of protons. Hydrogen atom motion from the EA model and carbon/oxygen atom motion from the UA model closely follow the experimental hydrogen motion, while hydrogen atoms reinserted in the UA model are too fast. The EA and UA models provide a good description of the orientation properties of C-H vectors measured by nuclear magnetic resonance experiments. Although dynamic observables in the CG model are in excellent agreement with their united atom counterparts, they cannot be compared to neutron data because the time after which the CG model is valid is greater than the neutron decay times.

  13. Nuclear magnetic resonance investigation of dynamics in poly(ethylene oxide)-based lithium polyether-ester-sulfonate ionomers

    NASA Astrophysics Data System (ADS)

    Roach, David J.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

    2012-01-01

    Nuclear magnetic resonance spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies for motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though lithium hopping is about ten times slower than the segmental motion. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and quasi-elastic neutron scattering experiments.

  14. Enhancement of stiffness, strength, ductility and toughness of poly(ethylene oxide) using phenoxy-grafted multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, Bing-Xing; Shi, Jia-Hua; Pramoda, K. P.; Goh, Suat Hong

    2007-03-01

    Phenoxy (poly(hydroxyether of bisphenol-A), also known as poly(bisphenol-A-co-epichlorohydrin)) was grafted onto multiwalled carbon nanotubes (MWNTs) by a reactive blending process. Reactions between terminal glycidyl groups of phenoxy and carboxylic acid groups of acidified MWNTs resulted in the grafting of phenoxy chains onto MWNTs. The mechanical properties of composites of poly(ethylene oxide) (PEO) and phenoxy-grafted MWNTs were studied. The miscibility between PEO and phenoxy enabled the good dispersion of nanotubes in the PEO matrix as evidenced by polarized optical microscopy and transmission electron microscopy. The spherulite size of PEO progressively decreased with increasing amount of phenoxy-grafted MWNTs added. At an optimal MWNT content of 1.5 wt%, the addition of phenoxy-grafted MWNTs led to increases of storage modulus, Young's modulus, yield stress, tensile strength, ultimate strain, and toughness of PEO by 113, 228, 166, 442, 1240, and 4080%, respectively. Such simultaneous increases in stiffness, strength, ductility and toughness of a polymer by an additive are rather uncommon.

  15. Contribution toward comprehension of contact angle values on single polydimethylsiloxane and poly(ethylene oxide) polymer networks.

    PubMed

    Bouteau, Murielle; Cantin, Sophie; Fichet, Odile; Perrot, Françoise; Teyssié, Dominique

    2010-11-16

    The large application ranges of polydimethylsiloxane (PDMS) and poly(ethylene oxide) (PEO) based materials justify the importance of controlling polymer surface properties including morphology and wettability behavior. However, it appears that the reported contact angle values of PDMS surfaces show significant scattering which cannot always be interpreted in terms of sole chemical data. In addition, few values are reported concerning pure PEO surfaces, since the polymer generally swells in the presence of water. Thus, in order to correlate surface properties with sample preparation, several single PDMS and PEO polymer networks were synthesized with varying cross-linkers and different cross-linking densities. First, the sample surface topography was systematically analyzed by atomic force microscopy (AFM). It was proven that the removal process of the polymer film from the mold plays a significant role in surface topography according to the vitreous or rubbery state of the given polymer network at room temperature irrespective of mold surface treatment. AFM-scale smooth surfaces can be obtained for all the samples by removing them systematically from the mold at a temperature below the α-relaxation temperature. Dynamic water contact angles were then measured and the values analyzed as a function of cross-linker nature and cross-linking density.

  16. Poly(ethylene oxide)-Assisted Macromolecular Self-Assembly of Lignin in ABS Matrix for Sustainable Composite Applications

    DOE PAGES

    Akato, Kokouvi M.; Tran, Chau D.; Chen, Jihua; ...

    2015-11-05

    Here we report the compatibilization of biomass-derived lignin polymer in acrylonitrile butadiene styrene (ABS) thermoplastic matrix without loss of mechanical properties via poly(ethylene oxide) (PEO)-mediated macromolecular self-assembly. ABS was blended with lignin in different concentrations, and blends with 10 wt % PEO (relative to lignin) were prepared. The relative tensile strength improved slightly at low lignin content but diminished rapidly as the lignin content was increased. However, the inclusion of PEO as an interfacial adhesion promoter helped avoid deleterious effects. Dynamic mechanical analysis showed that PEO plasticized the hard phase and thus lowered the activation energy (Ea) for its relaxationmore » but caused stiffening of the soft phase and increased its Ea. Microscopy revealed that incorporating lignin in ABS led to the statistical dispersion of discrete lignin domains (300–1000 nm) which, after PEO addition, were reduced to smaller interconnected particles (200–500 nm). The lignin-extended partially renewable ABS resins showed shear-thinning behavior and reduced viscosity compared to neat ABS. The preferred lignin-loaded compositions reinforced with 20 vol % chopped carbon fibers exhibited mechanical performances (77–80 MPa) equivalent to those of reinforced ABS materials reportedly used in 3D printing applications. In conclusion, this approach could lower the cost of ABS while reducing its carbon footprint.« less

  17. Synthesis and Gelation Characteristics of Photo-Crosslinkable Star Poly(ethylene oxide-co-lactide-glycolide acrylate) Macromonomers

    PubMed Central

    Moeinzadeh, Seyedsina; Khorasani, Saied Nouri; Ma, Junyu; He, Xuezhong; Jabbari, Esmaiel

    2011-01-01

    Viability of encapsulated cells in situ crosslinkable macromonomers depends strongly on the minimum concentration of polymerization initiators and monomers required for gelation. Novel 4-arm poly(ethylene oxide-co-lactide-glycolide acrylate) (SPELGA) macromonomers were synthesized and characterized with respect to gelation, sol fraction, degradation, and swelling in aqueous solution. SPELGA macromonomers were crosslinked in the absence of N-vinyl-2-pyrrolidone (NVP) monomer to produce a hydrogel network with a shear modulus of 27±4 kPa. The shear modulus of the gels increased by 170-fold as the macromonomer concentration was increased from 10 to 25 wt%. Sol fraction ranged between 8–18%. Addition of only 0.4 mol% NVP to the polymerization mixture increased modulus by 2.2-fold from 27±4 (no NVP) to 60±10 kPa. The higher modulus was attributed to the dilution effect of polymer chains in the sol, by delaying the onset of diffusion-controlled reaction, and cross-propagation of the growing chains with network-bound SPELGA acrylates. Degradation of SPELGA gels depended on water content and density of hydrolytically degradable ester groups. PMID:21927508

  18. Direct measurement of interaction forces between bovine serum albumin and poly(ethylene oxide) in water and electrolyte solutions.

    PubMed

    Acuña, Sergio M; Bastías, José M; Toledo, Pedro G

    2017-01-01

    The net interaction between a probe tip coated with bovine serum albumin (BSA) protein and a flat substrate coated with poly(ethylene oxide) (PEO) polymer was measured directly on approach in water and electrolyte solutions using AFM. The approach force curve between the two surfaces was monotonically repulsive in water and in electrolyte solutions. At pH ~5, slightly above the isoelectric point (pI) of BSA, and at large distances, the force was dominated by electrostatic repulsion between the oxygen atoms of the incoming protein with those belonging to the ether groups of PEO. Such repulsive force and range decreased in NaCl. Under physiological conditions, pH 6, BSA is definitely charged and the electrostatic repulsion with ether groups in PEO appears at larger separation distances. Interestingly, at pH 4, below the pI of BSA, the repulsion decreased because of an attractive, although weak, electrostatic force that appeared between the ether groups in PEO and the positively charged amino groups of BSA. However, for all solution conditions, once compression of PEO begun, the net repulsion was always dominated by short-range polymeric steric repulsion and repulsive enthalpy penalties for breaking PEO-water bonds. Results suggest that PEO in mushroom conformation may also be effective in reducing biofouling.

  19. Tuning thin-film electrolyte for lithium battery by grafting cyclic carbonate and combed poly(ethylene oxide) on polysiloxane.

    PubMed

    Li, Jie; Lin, Yue; Yao, Hehua; Yuan, Changfu; Liu, Jin

    2014-07-01

    A tunable polysiloxane thin-film electrolyte for all-solid-state lithium-ion batteries was developed. The polysiloxane was synthesized by hydrosilylation of polymethylhydrosiloxane with cyclic [(allyloxy)methyl]ethylene ester carbonic acid and vinyl tris(2-methoxyethoxy)silane. (1) H NMR spectroscopy and gel-permeation chromatography demonstrated that the bifunctional groups of the cyclic propylene carbonate (PC) and combed poly(ethylene oxide) (PEO) were well grafted on the polysiloxane. At PC/PEO=6:4, the polysiloxane-based electrolyte had an ionic conductivity of 1.55 × 10(-4) and 1.50 × 10(-3)  S cm(-1) at 25 and 100 °C, respectively. The LiFePO4 /Li batteries fabricated with the thin-film electrolyte presented excellent cycling performance in the temperature range from 25 to 100 °C with an initial discharge capacity at a rate of 1 C of 88.2 and 140 mA h g(-1) at 25 and 100 °C, respectively.

  20. Preparation of Pure and Stable Chitosan Nanofibers by Electrospinning in the Presence of Poly(ethylene oxide).

    PubMed

    Mengistu Lemma, Solomon; Bossard, Frédéric; Rinaudo, Marguerite

    2016-10-26

    Electrospinning was employed to obtain chitosan nanofibers from blends of chitosans (CS) and poly(ethylene oxide) (PEO). Blends of chitosan (MW (weight-average molecular weight) = 102 kg/mol) and PEO (M (molecular weight) = 1000 kg/mol) were selected to optimize the electrospinning process parameters. The PEO powder was solubilized into chitosan solution at different weight ratios in 0.5 M acetic acid. The physicochemical changes of the nanofibers were determined by scanning electron microscopy (SEM), swelling capacity, and nuclear magnetic resonance (NMR) spectroscopy. For stabilization, the produced nanofibers were neutralized with K₂CO₃ in water or 70% ethanol/30% water as solvent. Subsequently, repeated washings with pure water were performed to extract PEO, potassium acetate and carbonate salts formed in the course of chitosan nanofiber purification. The increase of PEO content in the blend from 20 to 40 w% exhibited bead-free fibers with average diameters 85 ± 19 and 147 ± 28 nm, respectively. Their NMR analysis proved that PEO and the salts were nearly completely removed from the nanostructure of chitosan, demonstrating that the adopted strategy is successful for producing pure chitosan nanofibers. In addition, the nanofibers obtained after neutralization in ethanol-aqueous solution has better structural stability, at least for six months in aqueous solutions (phosphate buffer (PBS) or water).

  1. Nd:YVO4 laser direct ablation of indium tin oxide films deposited on glass and polyethylene terephthalate substrates.

    PubMed

    Wang, Jian-Xun; Kwon, Sang Jik; Han, Jae-Hee; Cho, Eou Sik

    2013-09-01

    A Q-switched diode-pumped neodymium-doped yttrium vanadate (Nd:YVO4, lambda = 1064 nm) laser was applied to obtain the indium tin oxide (ITO) patterns on flexible polyethylene terephthalate (PET) substrate by a direct etching method. After the ITO films were deposited on a soda-lime glass and PET substrate, laser ablations were carried out on the ITO films for various conditions and the laser ablated results on the ITO films were investigated and analyzed considering the effects of substrates on the laser etching. The laser ablated widths on ITO deposited on glass were found to be much narrower than those on ITO deposited on PET substrate, especially, at a higher scanning speed of laser beam such as 1000 mm/s and 2000 mm/s. As the thermal conductivity of glass substrate is about 7.5 times higher than that of PET, more thermal energy would be spread and transferred to lateral direction in the ITO film in case of PET substrate.

  2. Room temperature crystallization of indium tin oxide films on glass and polyethylene terephthalate substrates using rf plasma

    SciTech Connect

    Ohsaki, H.; Suzuki, M.; Shibayama, Y.; Kinbara, A.; Watanabe, T.

    2007-07-15

    The crystallization of amorphous indium tin oxide (ITO) films was achieved by rf (13.56 MHz) plasma treatment. Although the films were crystallized after 2 min, the sample temperature was lower than 90 deg. C without compulsory cooling even after 10 min of treatment and polyethylene terephthalate (PET) substrates had no damage. Plasma-crystallized sputtered ITO films have a bixbite structure and the resistivity reached to 1.6x10{sup -4} {omega}{center_dot}cm. ITO thin films have almost the same resistivity in both cases of PET and glass substrates used and plasma-treated PET ITO films have a bit higher resistivity than that of glass ITO films, while mass spectroscopy measurements indicated that ITO films deposited on PET substrates are expected to include no apparent gas species ejected from PET substrate. It was found that the plasma gas pressure is the key parameter for the effective crystallization and the appropriate gas pressure depends on the plasma gas species.

  3. Nanofibrous chitosan-polyethylene oxide engineered scaffolds: a comparative study between simulated structural characteristics and cells viability.

    PubMed

    Kazemi Pilehrood, Mohammad; Dilamian, Mandana; Mirian, Mina; Sadeghi-Aliabadi, Hojjat; Maleknia, Laleh; Nousiainen, Pertti; Harlin, Ali

    2014-01-01

    3D nanofibrous chitosan-polyethylene oxide (PEO) scaffolds were fabricated by electrospinning at different processing parameters. The structural characteristics, such as pore size, overall porosity, pore interconnectivity, and scaffold percolative efficiency (SPE), were simulated by a robust image analysis. Mouse fibroblast cells (L929) were cultured in RPMI for 2 days in the presence of various samples of nanofibrous chitosan/PEO scaffolds. Cell attachments and corresponding mean viability were enhanced from 50% to 110% compared to that belonging to a control even at packed morphologies of scaffolds constituted from pores with nanoscale diameter. To elucidate the correlation between structural characteristics within the depth of the scaffolds' profile and cell viability, a comparative analysis was proposed. This analysis revealed that larger fiber diameters and pore sizes can enhance cell viability. On the contrary, increasing the other structural elements such as overall porosity and interconnectivity due to a simultaneous reduction in fiber diameter and pore size through the electrospinning process can reduce the viability of cells. In addition, it was found that manipulation of the processing parameters in electrospinning can compensate for the effects of packed morphologies of nanofibrous scaffolds and can thus potentially improve the infiltration and viability of cells.

  4. Preparation of Pure and Stable Chitosan Nanofibers by Electrospinning in the Presence of Poly(ethylene oxide)

    PubMed Central

    Mengistu Lemma, Solomon; Bossard, Frédéric; Rinaudo, Marguerite

    2016-01-01

    Electrospinning was employed to obtain chitosan nanofibers from blends of chitosans (CS) and poly(ethylene oxide) (PEO). Blends of chitosan (MW (weight-average molecular weight) = 102 kg/mol) and PEO (M (molecular weight) = 1000 kg/mol) were selected to optimize the electrospinning process parameters. The PEO powder was solubilized into chitosan solution at different weight ratios in 0.5 M acetic acid. The physicochemical changes of the nanofibers were determined by scanning electron microscopy (SEM), swelling capacity, and nuclear magnetic resonance (NMR) spectroscopy. For stabilization, the produced nanofibers were neutralized with K2CO3 in water or 70% ethanol/30% water as solvent. Subsequently, repeated washings with pure water were performed to extract PEO, potassium acetate and carbonate salts formed in the course of chitosan nanofiber purification. The increase of PEO content in the blend from 20 to 40 w% exhibited bead-free fibers with average diameters 85 ± 19 and 147 ± 28 nm, respectively. Their NMR analysis proved that PEO and the salts were nearly completely removed from the nanostructure of chitosan, demonstrating that the adopted strategy is successful for producing pure chitosan nanofibers. In addition, the nanofibers obtained after neutralization in ethanol-aqueous solution has better structural stability, at least for six months in aqueous solutions (phosphate buffer (PBS) or water). PMID:27792192

  5. Li+ transport in poly(ethylene oxide) based electrolytes: neutron scattering, dielectric spectroscopy, and molecular dynamics simulations.

    PubMed

    Do, Changwoo; Lunkenheimer, Peter; Diddens, Diddo; Götz, Marion; Weiss, Matthias; Loidl, Alois; Sun, Xiao-Guang; Allgaier, Jürgen; Ohl, Michael

    2013-07-05

    The dynamics of Li(+) transport in polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imde mixtures are investigated by combining neutron spin-echo (NSE) and dielectric spectroscopy with molecular dynamics (MD) simulations. The results are summarized in a relaxation time map covering wide ranges of temperature and time. The temperature dependence of the dc conductivity and the dielectric α relaxation time is found to be identical, indicating a strong coupling between both. The relaxation times obtained from the NSE measurements at 0.05 Å(-1)

  6. Dielectric and mechanical investigations on the hydrophilicity and hydrophobicity of polyethylene oxide modified on a silicon surface

    DOE PAGES

    Shang, Jing; Hong, Kunlun; Wang, Tao; ...

    2016-10-02

    Here, polyethylene oxide (PEO) has been widely used in biomedical fields. The antibiofouling property of the PEO-modified surface has been extensively investigated but is far from being fully understood. A series of PEOs with narrowly distributed molecular weight (Mw), synthesized with the technique of high vacuum anionic polymerization, have been successfully grafted onto the surface of silicon wafers. The power-law relationship between the thickness of the monolayer versus the Mw of the grafted PEO shows a scaling of 0.3, indicating compact condensing of the chains. The static contact angles show higher hydrophobicity for the layer of PEO with higher Mw,more » which can be attributed to the closely packed conformation of the chains with high density. The frequency shift of the contact resonance indicates that the Young’s modulus decreases and the loss factor increases with the increase in the Mw of PEO and the thickness of the PEO layers. Dielectric spectroscopy of bare or PEO-grafted wafers in the aqueous solutions reveals an interfacial polarization, which results from compositional and structural changes in the interface layer and depends on temperatures and salt concentrations. At a given grafting density, the PEO chains are swollen in pure water, demonstrating hydrophilic behavior, whereas they collapse in salt solutions, showing hydrophobic characteristics.« less

  7. Enhanced lithium battery with polyethylene oxide-based electrolyte containing silane-Al2 O3 ceramic filler.

    PubMed

    Zewde, Berhanu W; Admassie, Shimelis; Zimmermann, Jutta; Isfort, Christian Schulze; Scrosati, Bruno; Hassoun, Jusef

    2013-08-01

    A solid polymer electrolyte prepared by using a solvent-free, scalable technique is reported. The membrane is formed by low-energy ball milling followed by hot-pressing of dry powdered polyethylene oxide polymer, LiCF3 SO3 salt, and silane-treated Al2 O3 (Al2 O3 -ST) ceramic filler. The effects of the ceramic fillers on the properties of the ionically conducting solid electrolyte membrane are characterized by using electrochemical impedance spectroscopy, XRD, differential scanning calorimeter, SEM, and galvanostatic cycling in lithium cells with a LiFePO4 cathode. We demonstrate that the membrane containing Al2 O3 -ST ceramic filler performs well in terms of ionic conductivity, thermal properties, and lithium transference number. Furthermore, we show that the lithium cells, which use the new electrolyte together with the LiFePO4 electrode, operate within 65 and 90 °C with high efficiency and long cycle life. Hence, the Al2 O3 -ST ceramic can be efficiently used as a ceramic filler to enhance the performance of solid polymer electrolytes in lithium batteries.

  8. Prediction of acetaminophen's solubility in poly(ethylene oxide) at room temperature using the Flory-Huggins theory.

    PubMed

    Yang, Min; Wang, Peng; Gogos, Costas

    2013-01-01

    Solid dispersion technologies such as hot-melt extrusion and spray drying are often used to enhance the solubility of poorly soluble drugs. The biggest challenge associated with solid dispersion systems is that amorphous drugs may phase-separate from the polymeric matrix and recrystallize during storage. A more fundamental understanding of drug-polymer mixtures is needed for the industry to embrace the solid dispersion technologies. In this study, a theoretical model based on Flory-Huggins lattice theory was utilized to predict the solubility of a model drug acetaminophen (APAP) in a semi-crystalline polymer poly(ethylene oxide) (PEO) at 300 K. The interaction parameter χ was calculated to be -1.65 from the depression of drug's melting temperature determined from rheological and differential scanning calorimetry analysis. The equilibrium solubility in amorphous PEO was estimated to be 11.7% at 300 K. Assuming no APAP molecules dissolve in the crystalline part of PEO, the adjusted theoretical solubility is around 2.3% considering PEO being 80% crystalline. The solubility of APAP in PEG 400 was calculated to be 14.6% by using the same χ value, close to the experimental measurement 17.1%. The drug's solubility could be altered noticeably by the change of both χ and polymer molecular weight. The study also suggests that the depression of drug's melting point is a good indicator for preliminary polymer screening. The polymer that reduces the melting point the most is likely to be most miscible with the drug.

  9. Controlled protein release from electrospun biodegradable fiber mesh composed of poly(epsilon-caprolactone) and poly(ethylene oxide).

    PubMed

    Kim, Taek Gyoung; Lee, Doo Sung; Park, Tae Gwan

    2007-06-29

    A blend mixture of poly(epsilon-caprolactone) (PCL) and poly(ethylene oxide) (PEO) was electrospun to produce fibrous meshes that could release a protein drug in a controlled manner. Various biodegradable polymers, such as poly(l-lactic acid) (PLLA), poly(epsilon-caprolactone) (PCL), and poly(d,l-lactic-co-glycolic acid) (PLGA) were dissolved, along with PEO and lysozyme, in a mixture of chloroform and dimethylsulfoxide (DMSO). The mixture was electrospun to produce lysozyme loaded fibrous meshes. Among the polymers, the PCL/PEO blend meshes showed good morphological stability upon incubation in the buffer solution, resulting in controlled release of lysozyme over an extended period with reduced initial bursts. With varying the PCL/PEO blending ratio, the release rate of lysozyme from the corresponding meshes could be readily modulated. The lysozyme release was facilitated by increasing the amount of PEO, indicating that entrapped lysozyme was mainly released out by controlled dissolution of PEO from the blend meshes. Lysozyme released from the electrospun fibers retained sufficient catalytic activity.

  10. 7Li NMR spectroscopy and ion conduction mechanism in mesoporous silica (SBA-15) composite poly(ethylene oxide) electrolyte

    NASA Astrophysics Data System (ADS)

    Reddy, M. Jaipal; Chu, Peter P.

    A composite of mesoporous silica (SBA-15) with a polyethylene oxide (PEO) polymer electrolyte is examined for use in various electrochemical devices. Incorporation of SBA-15 in a PEO:LiClO 4 polymer electrolyte facilitates salt dissociation, enhances ion conductivity, and improves miscibility between organic and inorganic moieties. Optimized conductivity is found at 10 wt.% SBA-15 composition, above this concentration the conductivity is reduced due to aggregation of a SBA-15:Li rich phase. Heating above melt temperature of PEO allows more of the polymer segments to interact with SBA-15. This results in a greater degree of disorder upon cooling, and the ion conductivity is enhanced. A 7Li MAS NMR study reveals three types of lithium-ion coordination. Two major types of conduction mechanism can be identified: one through conventional amorphous PEO; a second via hopping in a sequential manner by replacing the nearby vacancies ('holes') on the surface (both interior and exterior) of the SBA-15 channels.

  11. Oxidative renaturation of hen egg-white lysozyme in polyethylene glycol-salt aqueous two-phase systems.

    PubMed

    Lotwin, J; De Bernardez Clark, E

    1999-11-20

    Aqueous two-phase systems have been widely used for the separation and concentration of proteins. In this work we investigated the possibility of using aqueous two-phase system for the renaturation of inclusion body proteins by studying the effect of polyethylene glycol (PEG)-salt systems on the oxidative renaturation of hen egg-white lysozyme (HEWL) with guanidinium chloride (GdmCl) present in the system. To accomplish phase separation at moderately low concentrations of polymer and salt, the total GdmCl concentration had to be kept low (<1 M). The unfolded protein exhibited very low solubility under these conditions. In an attempt to increase the solubility of the protein, temperatures of 40, 50, and 60 degrees C were investigated. The effect of PEG molecular weight was also addressed. Best renaturation yields were obtained when using PEG 3400 and working at 50 degrees C. However, the total protein concentration had to be kept at a low level of 0.2 mg/mL. Lowering the total GdmCl concentration in the system resulted in increased aggregation.

  12. Poly(ethylene oxide)-Assisted Macromolecular Self-Assembly of Lignin in ABS Matrix for Sustainable Composite Applications

    SciTech Connect

    Akato, Kokouvi M.; Tran, Chau D.; Chen, Jihua; Naskar, Amit K.

    2015-11-05

    Here we report the compatibilization of biomass-derived lignin polymer in acrylonitrile butadiene styrene (ABS) thermoplastic matrix without loss of mechanical properties via poly(ethylene oxide) (PEO)-mediated macromolecular self-assembly. ABS was blended with lignin in different concentrations, and blends with 10 wt % PEO (relative to lignin) were prepared. The relative tensile strength improved slightly at low lignin content but diminished rapidly as the lignin content was increased. However, the inclusion of PEO as an interfacial adhesion promoter helped avoid deleterious effects. Dynamic mechanical analysis showed that PEO plasticized the hard phase and thus lowered the activation energy (Ea) for its relaxation but caused stiffening of the soft phase and increased its Ea. Microscopy revealed that incorporating lignin in ABS led to the statistical dispersion of discrete lignin domains (300–1000 nm) which, after PEO addition, were reduced to smaller interconnected particles (200–500 nm). The lignin-extended partially renewable ABS resins showed shear-thinning behavior and reduced viscosity compared to neat ABS. The preferred lignin-loaded compositions reinforced with 20 vol % chopped carbon fibers exhibited mechanical performances (77–80 MPa) equivalent to those of reinforced ABS materials reportedly used in 3D printing applications. In conclusion, this approach could lower the cost of ABS while reducing its carbon footprint.

  13. Protective effects of polyethylene oxide on the vascular and organ function of rats with severe hemorrhagic shock.

    PubMed

    Li, Qiang; Huang, Tao; Dong, Zhen

    2015-08-01

    This study examined the effects of polyethylene oxide (PEO) on the survival rate, hemodynamics, blood gas indexes, lactic acid levels, microcirculation, and inflammatory cytokine levels in rats subjected to severe hemorrhagic shock. The shocked rats were resuscitated with either Ringer's lactate solution or 20 ppm of PEO in Ringer's lactate solution for 1 h. It was found that infusion of PEO effectively improved the survival, metabolic acidosis, oxygen delivery, hyperlactacidemia, tissue perfusion, and inflammatory responses of rats subjected to hemorrhagic shock. In addition, we found, for the first time, that PEO showed protective effects on hepatic and renal injury, as evidenced by the significant decreases in the elevated levels of alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, and creatinine caused by shock induction after infusion of PEO (p < 0.05, 60 min post-resuscitation by comparison with pre-resuscitation). All of these findings indicate that PEO exhibits strong therapeutic effects under conditions of severe hemorrhagic shock,which also provides theoretical and experimental bases for the clinical use of PEO.

  14. Nuclear magnetic resonance investigation of dynamics in poly(ethylene oxide)-based lithium polyether-ester-sulfonate ionomers

    DOE PAGES

    Roach, David J.; Dou, Shichen; Colby, Ralph H.; ...

    2012-01-06

    Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies formore » motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though their respective correlation times differ significantly. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments.« less

  15. Direct measurement of interaction forces between bovine serum albumin and poly(ethylene oxide) in water and electrolyte solutions

    PubMed Central

    Bastías, José M.; Toledo, Pedro G.

    2017-01-01

    The net interaction between a probe tip coated with bovine serum albumin (BSA) protein and a flat substrate coated with poly(ethylene oxide) (PEO) polymer was measured directly on approach in water and electrolyte solutions using AFM. The approach force curve between the two surfaces was monotonically repulsive in water and in electrolyte solutions. At pH ~5, slightly above the isoelectric point (pI) of BSA, and at large distances, the force was dominated by electrostatic repulsion between the oxygen atoms of the incoming protein with those belonging to the ether groups of PEO. Such repulsive force and range decreased in NaCl. Under physiological conditions, pH 6, BSA is definitely charged and the electrostatic repulsion with ether groups in PEO appears at larger separation distances. Interestingly, at pH 4, below the pI of BSA, the repulsion decreased because of an attractive, although weak, electrostatic force that appeared between the ether groups in PEO and the positively charged amino groups of BSA. However, for all solution conditions, once compression of PEO begun, the net repulsion was always dominated by short-range polymeric steric repulsion and repulsive enthalpy penalties for breaking PEO-water bonds. Results suggest that PEO in mushroom conformation may also be effective in reducing biofouling. PMID:28296940

  16. Interaction of poly(ethylene oxide) with the sodium dodecyl sulfate micelle interface studied with nitroxide spin probes

    SciTech Connect

    Kang, Y.S.; Kevan, L. )

    1994-08-04

    Electron spin resonance (ESR) line widths of 5-, 7-, 12-, and 16-doxylstearic acid (x-DSA) and tempo nitroxides versus the concentration of poly(ethylene oxide) (PEO) in sodium dodecyl sulfate (SDS) micelles show different trends. The ESR line widths of 5-, 7-, and 16-DSA increase with increasing concentration of PEO, which is interpreted as due to increasing viscosity in the environment of the nitroxide spin probe. The tempo and 12-DSA line widths were independent of the concentration of PEO. The line width showed the highest value for 5-DSA and the lowest value of tempo. The line width of x-DSA decreases from 5-DSA to a minimum value for 12-DSA and then increases somewhat for 16-DSA. This is interpreted as bending of the alkyl chain to provide different locations for the nitroxide moiety relative to the micelle interface. The relative distances of the nitroxide moiety of [chi]-DSA from deuterated water at the SDS micelle interface was measured by deuterium electron spin echo modulation. The distances increased from 5-DSA to 12-DSA and then decreased for 16-DSA. The interpretation of the DSR line width trend is supported by the deuterium modulation depth trend. 28 refs., 5 figs., 2 tabs.

  17. Block and graft copolymers and NanoGel copolymer networks for DNA delivery into cell.

    PubMed

    Lemieux, P; Vinogradov, S V; Gebhart, C L; Guérin, N; Paradis, G; Nguyen, H K; Ochietti, B; Suzdaltseva, Y G; Bartakova, E V; Bronich, T K; St-Pierre, Y; Alakhov, V Y; Kabanov, A V

    2000-01-01

    Self-assembling complexes from nucleic acids and synthetic polymers are evaluated for plasmid and oligonucleotide (oligo) delivery. Polycations having linear, branched, dendritic. block- or graft copolymer architectures are used in these studies. All these molecules bind to nucleic acids due to formation of cooperative systems of salt bonds between the cationic groups of the polycation and phosphate groups of the DNA. To improve solubility of the DNA/polycation complexes, cationic block and graft copolymers containing segments from polycations and non-ionic soluble polymers, for example, poly(ethylene oxide) (PEO) were developed. Binding of these copolymers with short DNA chains, such as oligos, results in formation of species containing hydrophobic sites from neutralized DNA polycation complex and hydrophilic sites from PEO. These species spontaneously associate into polyion complex micelles with a hydrophobic core from neutralized polyions and a hydrophilic shell from PEO. Such complexes are very small (10-40 nm) and stable in solution despite complete neutralization of charge. They reveal significant activity with oligos in vitro and in vivo. Binding of cationic copolymers to plasmid DNA forms larger (70-200 nm) complexes. which are practically inactive in cell transfection studies. It is likely that PEO prevents binding of these complexes with the cell membranes ("stealth effect"). However attaching specific ligands to the PEO-corona can produce complexes, which are both stable in solution and bind to target cells. The most efficient complexes were obtained when PEO in the cationic copolymer was replaced with membrane-active PEO-b-poly(propylene oxide)-b-PEO molecules (Pluronic 123). Such complexes exhibited elevated levels of transgene expression in liver following systemic administration in mice. To increase stability of the complexes, NanoGel carriers were developed that represent small hydrogel particles synthesized by cross-linking of PEI with double end

  18. Quantifying the effects of sterilization and aging on the oxidative degradation and wear of crosslinked and conventional polyethylene used in total joint replacement

    NASA Astrophysics Data System (ADS)

    Willie, Bettina Maria

    2005-07-01

    Nearly 500,000 total knee and hip replacements are performed annually in the United States. The generation of ultra-high molecular weight polyethylene (PE) particulate wear debris and associated osteolysis has increasingly become the predominant cause of revision operation. Research has shown that radiation sterilization in air results in increased oxidative degradation and accelerated wear of PE components. The overall goal of this work was to better understand the effect of sterilization, radiation crosslinking, and aging on the oxidative degradation and wear performance of PE components in order to improve clinical outcomes in total joint replacement. The data indicated that after four years of real-time shelf aging, PE that was radiation sterilized in air or nitrogen had significantly greater oxidative degradation compared to PE that was sterilized with either gas plasma or ethylene oxide. After two years of real-time shelf aging, negligible oxidation occurred with minimal changes in density and percent crystallinity, indicating that oxidative degradation was not an issue in the highly crosslinked and conventional polyethylene components examined. The differences measured between time zero and two years shelf aging may be likely explained by instrumentation error or variation within polyethylene manufacturing lots. Data suggest that current manufacturing and packaging technologies have successfully avoided oxidative degradation during shelf aging. Shelf aging may not be a concern in highly crosslinked or conventional polyethylene with current packaging technologies. Conventional PE tibial components had significantly greater percent area of premelt total surface damage compared to crosslinked PE tibial components. However, conventional PE tibial components did not have a significantly different percent area of postmelt total surface damage compared to crosslinked PE tibial components. Data indicated that in vivo duration was a significant predictor of premelt

  19. Complex Transformations between Bicontinuous Cubic and Cylinder Phases in a Polystyrene-block-Poly(ethylene oxide) Diblock Copolymer

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Sun, Lu; Ge, Qing; Quirk, Roderic P.; Cheng, Stephen Z. D.; Hsiao, Benjamin S.; Sics, Igors; Avila-Orta, Carlos

    2004-03-01

    Complex phase transformations between bicontinuous cubic and hexagonal cylinder (Hex) phases in a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer were investigated using small angle X-ray scattering (SAXS), transmission electron microscope (TEM), rheology, and polarized light microscope (PLM). The sample exhibited a typical double gyroid (G) phase, together with a minority plumbers nightmare (P) phase which was only ˜6 vol.% as calculated from the SAXS scattering intensities for each phase. These two bicontinuous cubic phases had the same unit cell dimensions. Under a large-amplitude reciprocating shear, the bicontinuous cubic sample transformed into a single-crystal Hex phase. Annealing this sample at 150 ^oC for 40 min, the Hex phase partially transformed into well-oriented G and P twin structures, as evidenced by two-dimensional synchrotron SAXS experiments. Epitaxial phase transformation relationships between the Hex/G and Hex/P phases were identified. The phase transformations were further confirmed by rheology study and PLM observations. The P phase was metastable with respect to the G phase, and it disappeared when the sample was heated above the order-disorder transition temperature and annealed at 150 ^oC. The mechanism of the Hex arrow G transformation was investigated by TEM. Generally, in a hexagonal cell, three cylinders evolved into left-handed helices, while the other three formed right-handed helices. An intermediate five-fold junction was speculated to facilitate the phase transformation. The Hex -> G phase transformation was observed to follow a nucleation and growth mechanism, and the phase transition zone was less than one unit cell.

  20. Single-molecule tracking studies of flow-induced microdomain alignment in cylinder-forming polystyrene-poly(ethylene oxide) diblock copolymer films.

    PubMed

    Tran-Ba, Khanh-Hoa; Higgins, Daniel A; Ito, Takashi

    2014-09-25

    Flow-based approaches are promising routes to preparation of aligned block copolymer microdomains within confined spaces. An in-depth characterization of such nanoscale morphologies within macroscopically nonuniform materials under ambient conditions is, however, often challenging. In this study, single-molecule tracking (SMT) methods were employed to probe the flow-induced alignment of cylindrical microdomains (ca. 22 nm in diameter) in polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) films. Films of micrometer-scale thicknesses were prepared by overlaying a benzene solution droplet on a glass coverslip with a rectangular glass plate, followed by solvent evaporation under a nitrogen atmosphere. The microdomain alignment was quantitatively assessed from SMT data exhibiting the diffusional motions of individual sulforhodamine B fluorescent probes that preferentially partitioned into cylindrical PEO microdomains. Better overall microdomain orientation along the flow direction was observed near the substrate interface in films prepared at a higher flow rate, suggesting that the microdomain alignment was primarily induced by shear flow. The SMT data also revealed the presence of micrometer-scale grains consisting of highly ordered microdomains with coherent orientation. The results of this study provide insights into shear-based preparation of aligned cylindrical microdomains in block copolymer films from solutions within confined spaces.

  1. Hole injection in tri-arylamine containing polyfluorene co-polymer devices with molybdenum oxide contacts

    NASA Astrophysics Data System (ADS)

    Buckley, Alastair; Pickup, David; Yates, Chris; Zhao, Yi; Lidzey, David

    2011-04-01

    We report spectroscopic and electrical measurements to explore hole injection and conduction in devices comprising a molybdenum sub-oxide (MoOx) hole injection layers and poly[(9,9-dioctylfluorenyl-2, 7-diyl)-co-(4,4'(N-(4-sec-butylphenyl))) diphenylamine](TFB) hole transporting polymer. We report improvements in device conductivity over benchmark structures incorporating an ITO electrode and polyethylenedioxythiophene polystyrene sulfonate (PEDOT:PSS) hole injection layers and furthermore achieve injection from MoOx to TFB that is efficient even with an underlying low workfunction Al electrode. XPS spectroscopy has been used to investigate the electronic structure of the interfaces and we find discrete energy alignment regimes consistent with recent surface science studies by Tengstedt et al. [Appl. Phys. Lett. 88, 053502 (2006)], corresponding to Fermi level pinning for MoOx/TFB and vacuum level pinning in the case of Al/TFB. While the energetic alignment regime is measured to be independent of MoOx thickness, the device conductivity continuously varies with MoOx thickness; an observation that can be qualitatively explained by considering two independent charge injection mechanisms from molybdenum oxide sites having different stoicheometry.

  2. Growth of ordered silver nanoparticles in silica film mesostructured with a triblock copolymer PEO-PPO-PEO

    NASA Astrophysics Data System (ADS)

    Bois, L.; Chassagneux, F.; Parola, S.; Bessueille, F.; Battie, Y.; Destouches, N.; Boukenter, A.; Moncoffre, N.; Toulhoat, N.

    2009-07-01

    Elaboration of mesostructured silica films with a triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide, (PEO-PPO-PEO) and controlled growth of silver nanoparticles in the mesostructure are described. The films are characterized using UV-visible optical absorption spectroscopy, TEM, AFM, SEM, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Organized arrays of spherical silver nanoparticles with diameter between 5 and 8 nm have been obtained by NaBH 4 reduction. The size and the repartition of silver nanoparticles are controlled by the film mesostructure. The localization of silver nanoparticles exclusively in the upper-side part of the silica-block copolymer film is evidenced by RBS experiment. On the other hand, by using a thermal method, 40 nm long silver sticks can be obtained, by diffusion and coalescence of spherical particles in the silica-block copolymer layer. In this case, migration of silver particles toward the glass substrate-film interface is shown by the RBS experiment.

  3. Polymeric micelles based on poly(ethylene oxide) and α-carbon substituted poly(ɛ-caprolactone): An in vitro study on the effect of core forming block on polymeric micellar stability, biocompatibility, and immunogenicity.

    PubMed

    Garg, Shyam M; Vakili, Mohammad Reza; Lavasanifar, Afsaneh

    2015-08-01

    A series of block copolymers based on methoxy poly(ethylene oxide)-block-poly(ɛ-caprolactone) (PEO-b-PCL), PEO-b-PCL bearing side groups of benzyl carboxylate (PEO-b-PBCL), or free carboxyl (PEO-b-PCCL) on the PCL backbone with increasing degrees of polymerization of the PCL backbone were synthesized. Prepared block copolymers assembled to polymeric micelles by co-solvent evaporation. The physical stability of prepared micelles was assessed by measuring their tendency toward aggregation over time using dynamic light scattering (DLS). The resistance of micelles against dissociation in the presence of a micelle destabilizing agent, i.e., sodium dodecyl sulfate (SDS), was also investigated using DLS. The rate of micellar core degradation was determined using (1)H NMR for polymer molecular weight measurement upon incubation of micelles in PBS (pH=7.4) at 37°C followed by dialysis of the remaining polymer at different time intervals. The effect of pendent group chemistry in the micellar core on the adsorption of serum proteins to micellar structure was then evaluated using Bradford Protein assay kit. Finally, the effect of micellar core structure on the induction of bone marrow derived dendritic cell (BMDC) maturation and secretion of IL-12 was studied as a measure of micellar immunogenicity. The results showed micelle structures from polymers with higher degree of polymerization in the hydrophobic block and/or those with more hydrophobic substituents on the core-forming block, to be more stable. This was reflected by a decreased tendency for micellar aggregation, reduced dissociation of micelles in the presence of SDS, and diminished core degradation. All micelles were shown to have insignificant adsorption of serum protein suggesting that the hydrophilic PEO shell provided sufficient protection of the core. However, the protein adsorption increased with increase in the hydrophobicity and molecular weight of the core-forming block. Irrespective of the micellar core

  4. Fluorescence probe studies of pluronic copolymer solutions as a function of temperature

    SciTech Connect

    Nivaggioli, T.; Alexandridis, P.; Hatton, T.A.; Yekta, A.; Winnik, M.A.

    1995-03-01

    The temperature variation of the I{sub 1}/I{sub 3} ratio of pyrene vibrational fine structure has been studied in aqueous poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer solutions, in bulk PEO, PPO, and various organic solvents. Linear decreases were observed in organic solvents and in mixtures of bulk PEO and PPO. The data in aqueous PEO-PPO-PEO copolymer solutions reveal three distinct solution conditions: at low temperatures, the linear decrease with temperature parallels that for water; over a small intermediate temperature range there is a sharp decrease in the ratio, attributed to the formation of micelles; and at higher temperatures, a linear decrease is again observed. Values in this region are strongly dependent on the PPO block and are consistent with the representation of micelles with a core dominated by PPO. The composition of the micelle core was estimated using these data and indicated an increase of poly(ethylene oxide) as the polymer becomes more hydrophilic. In addition, the size of the micelles and their aggregation numbers were determined using light scattering and pyrene luminescence decay studies, respectively. These data showed an increase of the aggregation number with temperature while the hydrodynamic radius remained constant and were interpreted in terms of dehydration of the PEO block. 38 refs., 11 figs., 3 tabs.

  5. Effect of peptide secondary structure on adsorption and adsorbed film properties on end-grafted polyethylene oxide layers.

    PubMed

    Binazadeh, M; Zeng, H; Unsworth, L D

    2014-01-01

    Poly-l-lysine (PLL), in α-helix or β-sheet configuration, was used as a model peptide for investigating the effect of secondary structures on adsorption events to poly(ethylene oxide) (PEO) modified surfaces formed using θ solvents. Circular dichroism results showed that the secondary structure of PLL persisted upon adsorption to Au and PEO modified Au surfaces. Quartz crystal microbalance with dissipation (QCM-D) was used to characterize the chemisorbed PEO layer in different solvents (θ and good solvents), as well as the sequential adsorption of PLL in different secondary structures (α-helix or β-sheet). QCM-D results suggest that chemisorption of PEO 750 and 2000 from θ solutions led to brushes 3.8 ± 0.1 and 4.5 ± 0.1 nm thick with layer viscosities of 9.2 ± 0.8 and 4.8 ± 0.5 cP, respectively. The average number of H2O per ethylene oxides, while in θ solvent, was determined as ~0.9 and ~1.2 for the PEO 750 and 2000 layers, respectively. Upon immersion in good solvent (as used for PLL adsorption experiments), the number of H2O per ethylene oxides increased to ~1.5 and ~2.0 for PEO 750 and 2000 films, respectively. PLL adsorbed masses for α-helix and β-sheet on Au sensors was 231 ± 5 and 1087 ± 14 ng cm(-2), with layer viscosities of 2.3 ± 0.1 and 1.2 ± 0.1 cP, respectively; suggesting that the α-helix layer was more rigid, despite a smaller adsorbed mass, than that of β-sheet layers. The PEO 750 layer reduced PLL adsorbed amounts to ~10 and 12% of that on Au for α-helices and β-sheets respectively. The PLL adsorbed mass to PEO 2000 layers dropped to ~12% and 4% of that on Au, for α-helix and β-sheet respectively. No significant differences existed for the viscosities of adsorbed α-helix and β-sheet PLL on PEO surfaces. These results provide new insights into the fundamental understanding of the effects of secondary structures of peptides and proteins on their surface adsorption.

  6. Mechanical Characterization of Hybrid Vesicles Based on Linear Poly(Dimethylsiloxane-b-Ethylene Oxide) and Poly(Butadiene-b-Ethylene Oxide) Block Copolymers

    PubMed Central

    Gaspard, Jeffery; Casey, Liam M.; Rozin, Matt; Munoz-Pinto, Dany J.; Silas, James A.; Hahn, Mariah S.

    2016-01-01

    Poly(dimethylsiloxane-ethylene oxide) (PDMS-PEO) and poly(butadiene-b-ethylene oxide) (PBd-PEO) are two block copolymers which separately form vesicles with disparate membrane permeabilities and fluidities. Thus, hybrid vesicles formed from both PDMS-PEO and PBd-PEO may ultimately allow for systematic, application-specific tuning of vesicle membrane fluidity and permeability. However, given the relatively low strength previously noted for comb-type PDMS-PEO vesicles, the mechanical robustness of the resulting hybrid vesicles must first be confirmed. Toward this end, we have characterized the mechanical behavior of vesicles formed from mixtures of linear PDMS-PEO and linear PBd-PEO using micropipette aspiration. Tension versus strain plots of pure PDMS12-PEO46 vesicles revealed a non-linear response in the high tension regime, in contrast to the approximately linear response of pure PBd33-PEO20 vesicles. Remarkably, the area expansion modulus, critical tension, and cohesive energy density of PDMS12-PEO46 vesicles were each significantly greater than for PBd33-PEO20 vesicles, although critical strain was not significantly different between these vesicle types. PDMS12-PEO46/PBd33-PEO20 hybrid vesicles generally displayed graded responses in between that of the pure component vesicles. Thus, the PDMS12-PEO46/PBd33-PEO20 hybrid vesicles retained or exceeded the strength and toughness characteristic of pure PBd-PEO vesicles, indicating that future assessment of the membrane permeability and fluidity of these hybrid vesicles may be warranted. PMID:26999148

  7. Effects of ions on partitioning of serum albumin and lysozyme in aqueous two-phase systems containing ethylene oxide/propylene oxide co-polymers.

    PubMed

    Johansson, H O; Lundh, G; Karlström, G; Tjerneld, F

    1996-08-13

    Aqueous two-phase systems composed of ethylene oxide/propylene oxide random co-polymers, EO30/PO70 or Ucon (EO50/PO50), in the top phase and dextran T500 in the bottom phase, have been studied. The cloud point diagram for EO30/PO70 in water solution was determined. EO30/PO70 has a cloud point of 32 degrees C at a concentration of 10% (w/w). The phase diagram for the system EO30/PO70-dextran T500-water was determined. Salt effects have been studied on the partitioning of two model proteins, bovine serum albumin and hen egg white lysozyme, in EO30/PO70-dextran and Ucon-dextran systems. Ions with different hydrophobicity, i.e., with different position in the Hofmeister or lyotropic series, were investigated with reference to their effect on protein partition. The counterion hydrophobicity was shown to have a strong influence on the partitioning of BSA and lysozyme. Most extreme partitioning was obtained with hydrophobic (chaotropic) ions like CIO4- and I-. A comparison of protein partitioning between PEG-dextran and EO30/PO70-dextran has been done. A more extreme protein partitioning was obtained in the EO30/PO70-dextran containing system. Temperature-induced phase separation was studied with EO30/PO70 at 45 degrees C. Both BSA and lysozyme were completely partitioned to the water phase formed above the cloud point of EO30/PO70. Model calculations, based on Flory-Huggins theory of polymer solutions, have been done which could reproduce the salt effect on the protein partitioning in aqueous-two phase system.

  8. Crystalline structure of the poly(ethylene oxide)--p-nitrophenol complex; 2: Fourier transform infrared spectroscopy

    SciTech Connect

    Damman, P.; Point, J.J. . Service de Chimie-Physique et Thermodynamique)

    1994-07-04

    The authors have previously reported the existence of a crystalline compound made of poly(ethylene oxide) (PEO) and p-nitrophenol (pnp). From x-ray fiber patterns on stretched and spherulitic samples of this complex, a triclinic unit cell (a = 1.172 nm, b = 0.555 nm, c = 1.557 nm, [alpha] = 90.7[degree], [beta] = 87.1[degree], and [gamma] = 104.0[degree]) was deduced; the unit cell contains 6 PEO monomeric units and 4 pnp molecules, in agreement with the stoichiometry deduced from the phase diagram. The aim of this paper is to elucidate the conformation of the PEO chains and the mutual arrangement of the PEO and pnp molecules in the unit cell. To carry out this, the authors studied the dichroism of the IR bands of pnp in two differently oriented samples, namely, in stretched samples and in spherulites. The benzene rings are found to be perpendicular to the c crystallographic parameter (chain axis), and the 1--4 axis of pnp is found to be parallel to the a* reciprocal parameter. These observations completely determine the orientation of the pnp molecules in the unit cell. The conformation of the polymeric chains in the complex is not helical as in pure PEO. From the C[sub 2h] factor group of the PEO molecules, deduced from the FTIR observations, and the normal mode analysis of hydrogenated and deuterated PEO, they propose the (t[sub 2]gt[sub 2]gt[sub 3]t[sub 2]g[prime]t[sub 2]g[prime]t[sub 3]) glide type conformation. In conclusion, it appears that in the PEO--pnp complex a stack of pnp molecules stabilizes the surrounding PEO molecules in this new conformation.

  9. The influence of guaifenesin and ketoprofen on the properties of hot-melt extruded polyethylene oxide films.

    PubMed

    Crowley, Michael M; Fredersdorf, Anke; Schroeder, Britta; Kucera, Shawn; Prodduturi, Suneela; Repka, Michael A; McGinity, James W

    2004-08-01

    Films containing polyethylene oxide (PEO) and a model drug, either guaifenesin (GFN) or ketoprofen (KTP), were prepared by hot-melt extrusion. The thermal properties of the hot-melt extruded films were investigated using differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) was used to examine the surface morphology of the films, and wide angle X-ray diffraction (XRD) was used to investigate the crystalline properties of the polymer, drugs and physical mixtures as well as the solid state structure of the films. The stability of the polymer was studied using gel permeation chromatography. The mechanical properties, including percent elongation and tensile strength of the films, were determined on an Instron according to American Society for Testing Materials (ASTM) procedures. The Hansen solubility parameter was calculated using the Hoftyzer or van Krevelen method to estimate the likelihood of drug--polymer miscibility. Both GFN and KTP were stable during the extrusion process. Melting points corresponding to the crystalline drugs were not observed in the films. Crystallization of GFN on the surface of the film was observed at all concentrations studied, however KTP crystallization did not occur until reaching the 15% level. Guaifenesin and ketoprofen were found to decrease drive load, increase PEO stability and plasticize the polymer during extrusion. The Hansen solubility parameters predicted miscibility between PEO and KTP and poor miscibility between PEO and GFN. The predictions of the solubility parameters were in agreement with the XRD and SEM results. The percent elongation decreased with increasing GFN concentrations and significantly increased with increasing levels of KTP. Both GFN and KTP decreased the tensile strength of the extruded film.

  10. Spontaneous crystallinity loss of drugs in the disordered regions of poly(ethylene oxide) in the presence of water.

    PubMed

    Marsac, Patrick J; Romary, Daniel P; Shamblin, Sheri L; Baird, Jared A; Taylor, Lynne S

    2008-08-01

    The physical stability of active pharmaceutical ingredients (APIs) formulated in the crystalline state may be compromised in the presence of excipients. In the present study, it is shown that at high relative humidity, several model crystalline drugs compacted into a matrix of poly(ethylene oxide) (PEO) may dissolve into the disordered regions of the polymer. The purpose of this project is to identify both the physicochemical properties of the API and the polymer which may lead to such a transformation and the mechanism of transformation. Crystalline drugs and PEO were physically mixed, compressed into tablets, and stored in a dessicator at 94% RH. The physical state of the drug and the polymer were determined using Raman spectroscopy and X-ray powder diffraction. The solubility of each drug in PEG 400 was measured by ultraviolet spectroscopy, the thermal properties of each compound were measured using differential scanning calorimetry, and the amount of water sorbed into these systems from the vapor phase was determined by gravimetric analysis. A spontaneous loss of crystallinity was observed for many of the model drugs when stored at high relative humidity and in the presence of PEO. In the absence of PEO, no changes in the crystalline material were observed. However, the structure of PEO was dramatically altered when exposed to high relative humidity. Specifically, it was found that PEO undergoes a very slow deliquescence increasing the disordered fraction of the polymer which facilitates the "dissolution" of the crystalline drug into these disordered regions. The degree of transformation, estimated from Raman spectroscopy, was found to qualitatively correlate with the aqueous solubility of the compounds. It can be concluded that for the systems studied here, the phase stability of the polymer was compromised at high relative humidity and the polymer underwent deliquescence. The equilibrium phase of several of the crystalline drugs studied here was then altered

  11. Performance of polymer electrolyte based on chitosan blended with poly(ethylene oxide) for plasmonic dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Buraidah, M. H.; Teo, L. P.; Au Yong, C. M.; Shah, Shahan; Arof, A. K.

    2016-07-01

    Chitosan and poly(ethylene oxide) powders have been mixed in different weight ratios. To each mixture, a fixed amount of ammonium iodide has been added. All mixtures have been dissolved in 1% acetic acid solution to form polymer blend electrolyte films by the solution cast technique. X-ray diffraction indicates that the polymer blend electrolytes are amorphous. Fourier transform infrared spectroscopy shows shifting of the amine, carboxamide and Csbnd Osbnd C bands to lower wavenumbers indicating the occurrence of complexation. Electrochemical impedance spectroscopy has been used to study the electrical properties of the samples. The ionic conductivity for 55 wt.% chitosan-45 wt.% NH4I electrolyte system is 3.73 × 10-7 S cm-1 at room temperature and is increased to 3.66 × 10-6 S cm-1 for the blended film (16.5 wt.% chitosan-38.5 wt.% PEO)-45 wt.% NH4I film. Dye-sensitized solar cells (DSSCs) have been fabricated by sandwiching the polymer electrolyte between the TiO2/dye photoelectrode and Pt counter electrode. DSSCs fabricated exhibits short-circuit current density (Jsc) of 2.71 mA cm-2, open circuit voltage (Voc) of 0.58 V and efficiency of 0.78% with configuration ITO/TiO2/N3 dye/(16.5 wt.% chitosan-38.5 wt.% PEO)-45 wt.% NH4I(+I2)/Pt/ITO and Jsc of 2.84 mA cm-2, Voc of 0.58 V and efficiency of 1.13% with configuration ITO/TiO2 + Ag nanoparticles/N3 dye/(16.5 wt.% chitosan-38.5 wt.% PEO)-45 wt.% NH4I(+I2)/Pt/ITO.

  12. Interchain coupled chain dynamics of poly(ethylene oxide) in blends with poly(methyl methacrylate): Coupling model analysis

    NASA Astrophysics Data System (ADS)

    Ngai, K. L.; Wang, Li-Min

    2011-11-01

    Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past tc = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at tc. The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some tc determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental α-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.

  13. Structural effect of glyme-Li(+) salt solvate ionic liquids on the conformation of poly(ethylene oxide).

    PubMed

    Chen, Zhengfei; McDonald, Samila; Fitzgerald, Paul A; Warr, Gregory G; Atkin, Rob

    2016-06-01

    The conformation of 36 kDa polyethylene oxide (PEO) dissolved in three glyme-Li(+) solvate ionic liquids (SILs) has been investigated by small angle neutron scattering (SANS) and rheology as a function of concentration and compared to a previously studied SIL. The solvent quality of a SIL for PEO can be tuned by changing the glyme length and anion type. Thermogravimetric analysis (TGA) reveals that PEO is dissolved in the SILs through Li(+)-PEO coordinate bonds. All SILs (lithium triglyme bis(trifluoromethanesulfonyl)imide ([Li(G3)]TFSI), lithium tetraglyme bis(pentafluoroethanesulfonyl)imide ([Li(G4)]BETI), lithium tetraglyme perchlorate ([Li(G4)]ClO4) and the recently published [Li(G4)]TFSI) are found to be moderately good solvents for PEO but solvent quality decreases in the order [Li(G4)]TFSI ∼ [Li(G4)]BETI > [Li(G4)]ClO4 > [Li(G3)]TFSI due to decreased availability of Li(+) for PEO coordination. For the same glyme length, the solvent qualities of SILs with TFSI(-) and BETI(-) anions ([Li(G4)]TFSI and [Li(G4)]BETI) are very similar because they weakly coordinate with Li(+), which facilitates Li(+)-PEO interactions. [Li(G4)]ClO4 presents a poorer solvent environment for PEO than [Li(G4)]BETI because ClO4(-) binds more strongly to Li(+) and thereby hinders interactions with PEO. [Li(G3)]TFSI is the poorest PEO solvent of these SILs because G3 binds more strongly to Li(+) than G4. Rheological and radius of gyration (Rg) data as a function of PEO concentration show that the PEO overlap concentrations, c* and c**, are similar in the three SILs.

  14. Crystallization of poly(ethylene oxide) with acetaminophen--a study on solubility, spherulitic growth, and morphology.

    PubMed

    Yang, Min; Gogos, Costas

    2013-11-01

    A simple, sensitive, efficient, and novel method analyzing the number of spherulitic nuclei was proposed to estimate the solubility of a model drug acetaminophen (APAP) in poly(ethylene oxide) (PEO). At high crystallization temperature (323 K), 10% APAP-PEO had the same low number of spherulitic nuclei as pure PEO, indicating that APAP and PEO were fully miscible. At low crystallization temperature (303 K), the number of nuclei for 10% APAP-PEO was significantly higher, suggesting that APAP was oversaturated and therefore recrystallized and acted as a nucleating agent. Based on the results obtained, the solubility of APAP in PEO is possibly between the concentration of 0.1% and 1% at 303 K. The spherulitic growth rate G of PEO was found to decrease with increasing APAP concentration, suggesting that APAP is most likely functioning as a chemical defect and is either rejected from or included in the PEO crystals during chain folding. APAP could possibly locate in the inter-spherulitic, inter-fibrillar, inter-lamellar, or intra-lamellar regions of PEO. At 323 K, the morphology of 10% APAP-PEO is more dendritic than spherulitic with large unfilled space in between dendrites and spherulites, which is a sign of one or the combination of the four modes of segregation. An extensive spherulitic nucleation and growth kinetics study using the classical theoretical relationships, for example, the Hoffman-Lauritzen (HL) and Avrami theories, was conducted. Both microscopic and differential scanning calorimetric (DSC) analysis yielded similar values for the nucleation constant Kg as well as the fold surface free energy σe and work of chain folding q. The values of σe and q increased with APAP concentration, indicating that the chain folding of PEO was hindered by APAP.

  15. Electric-double-layer doping of WSe2 field-effect transistors using polyethylene-oxide cesium perchlorate

    NASA Astrophysics Data System (ADS)

    Fathipour, Sara; Pandey, Pratyush; Fullerton-Shirey, Susan; Seabaugh, Alan

    2016-12-01

    Electric double layers (EDLs) formed between polyethylene oxide cesium perchlorate and multilayer WSe2 field-effect transistors (FETs) are explored as a means for contact and access region doping. In this application, the electric double layer is formed using a top field plate or a side gate and then locked into place by cooling of the device below the glass transition temperature of the polymer. A dual work-function Ti/Pd contact is used to form the Schottky contacts with Ti as the n-contact and Pd as the p-contact and these are evaporated in a single evaporation. Using the EDL doping technique, sheet carrier density and current density are as high as (4.9 ± 1.9) × 1013 cm-2 and 58 μA/μm for n-doping and (3.5 ± 1.9) × 1013 cm-2 and 50 μA/μm for p-doping for the highest channel conductivities. The weak temperature dependence of the transfer characteristics at high doping levels reveals that the current in the Schottky contacts is dominated by tunneling with a contact resistance of 1 kΩ μm for the p-branch and 3.4 kΩ μm for the n-branch, comparable to the best WSe2 FET reports. At the highest carrier densities, the temperature coefficient of the conductance becomes negative as the mobility of the channel controls the temperature dependence. Using EDL doping, n-FET and p-FET configurations are demonstrated.

  16. Dispersion fraction enhances cellular growth of carbon nanotube and aluminum oxide reinforced ultrahigh molecular weight polyethylene biocomposites.

    PubMed

    Patel, Anup Kumar; Balani, Kantesh

    2015-01-01

    Ultrahigh molecular weight polyethylene (UHMWPE) is widely used as bone-replacement material for articulating surfaces due to its excellent wear resistance and low coefficient of friction. But, the wear debris, generated during abrasion between mating surfaces, leads to aseptic loosening of implants. Thus, various reinforcing agents are generally utilized, which may alter the surface and biological properties of UHMWPE. In the current work, the cellular response of compression molded UHMWPE upon reinforcement of bioactive multiwalled carbon nanotubes (MWCNTs) and bioinert aluminum oxide (Al2O3) is investigated. The phase retention and stability were observed using X-ray diffraction, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The reinforcement of MWCNTs and Al2O3 has shown to alter the wettability (from contact angle of ~88°±2° to ~118°±4°) and surface energy (from ~23.20 to ~17.75 mN/m) of composites with respect to UHMWPE, without eliciting any adverse effect on cytocompatibility for the L929 mouse fibroblast cell line. Interestingly, the cellular growth of the L929 mouse fibroblast cell line is observed to be dominated by the dispersion fraction of surface free energy (SFE). After 48 h of incubation period, a decrease in metabolic activity of MWCNT-Al2O3 reinforced composites is attributed to apatite formation that reduces the dispersion fraction of surface energy. The mineralized apatite during incubation was confirmed and quantified by energy dispersive spectroscopy and X-ray diffraction respectively. Thus, the dispersion fraction of surface free energy can be engineered to play an important role in achieving enhanced metabolic activity of the MWCNT-Al2O3 reinforced UHMWPE biopolymer composites.

  17. Interchain coupled chain dynamics of poly(ethylene oxide) in blends with poly(methyl methacrylate): coupling model analysis.

    PubMed

    Ngai, K L; Wang, Li-Min

    2011-11-21

    Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past t(c) = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at t(c). The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some t(c) determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental α-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.

  18. Design and formulation of nanoemulsions using 2-(poly(hexafluoropropylene oxide)) perfluoropropyl benzene in combination with linear perfluoro(polyethylene glycol dimethyl ether)

    PubMed Central

    Mountain, Gregory A.; Jelier, Benson J.; Bagia, Christina; Friesen, Chadron M.; Janjic, Jelena M.

    2014-01-01

    This is the first report where PFPAE aromatic conjugates and perfluoro(polyethylene glycol dimethyl ether) are combined and formulated as nanoemulsions with droplet size below 100 nm. A perfluoropolyalkylether (PFPAE) aromatic conjugate, 2-(poly(hexafluoropropylene oxide)) perfluoropropyl benzene, was used as fluorophilic-hydrophilic diblock (FLD) aimed at stabilizing perfluoro(polyethylene glycol dimethyl ether) nanoemulsions. Its effects on colloidal behaviors in triphasic (organic/fluorous/aqueous) nanoemulsions were studied. The addition of FLD construct to fluorous phase led to decrease in PFPAE nanoemulsion droplet size to as low as 85 nm. Prepared nanoemulsions showed high colloidal stability. Our results suggest that these materials represent viable novel approach to fluorous colloid systems design with potential for biomedical and synthetic applications. PMID:24976645

  19. Immobilization of natural anti-oxidants on carbon nanotubes and aging behavior of ultra-high molecular weight polyethylene-based nanocomposites

    NASA Astrophysics Data System (ADS)

    Dintcheva, Nadka Tzankova; Arrigo, Rossella; Gambarotti, Cristian; Guenzi, Monica; Carroccio, Sabrina; Cicogna, Francesca; Filippone, Giovanni

    2014-05-01

    The use of natural antioxidants is an attractive way to formulate nanocomposites with extended durability and with potential applications in bio-medical field. In this work, Vitamin E (VE) in the form of α-tocopherol and Quercetin (Q) are physically immobilized on the outer surface of multi-walled carbon nanotubes (CNTs). Afterward, the CNTs-VE and CNTs-Q are used to formulate thermally stable ultra high molecular weight polyethylene based nanocomposites. The obtained results in the study of the thermo-oxidation behavior suggest a beneficial effect of the natural anti-oxidant carbon nanotubes systems. The unexpected excellent thermo-resistance of the nanocomposites seems to be due to a synergistic effect of the natural anti-oxidant and carbon nanotubes, i.e. strong interaction between CNT surface and anti-oxidant molecules. Particularly, these interactions cause the formation of structural defects onto outer CNT surfaces, which, in turn, increase the CNT radical scavenging activity.

  20. Block copolymer with simultaneous electric and ionic conduction for use in lithium ion batteries

    DOEpatents

    Javier, Anna Esmeralda K; Balsara, Nitash Pervez; Patel, Shrayesh Naran; Hallinan, Jr., Daniel T

    2013-10-08

    Redox reactions that occur at the electrodes of batteries require transport of both ions and electrons to the active centers. Reported is the synthesis of a block copolymer that exhibits simultaneous electronic and ionic conduction. A combination of Grignard metathesis polymerization and click reaction was used successively to synthesize the block copolymer containing regioregular poly(3-hexylthiophene) (P3HT) and poly(ethylene oxide) (PEO) segments. The P3HT-PEO/LiTFSI mixture was then used to make a lithium battery cathode with LiFePO.sub.4 as the only other component. All-solid lithium batteries of the cathode described above, a solid electrolyte and a lithium foil as the anode showed capacities within experimental error of the theoretical capacity of the battery. The ability of P3HT-PEO to serve all of the transport and binding functions required in a lithium battery electrode is thus demonstrated.

  1. Tailor-Made Onion-Like Stereocomplex Crystals in Incompatible Enantiomeric Polylactide Containing Block Copolymer Blends

    SciTech Connect

    Sun,L.; Zhu, L.; Rong, L.; Hsiao, B.

    2006-01-01

    Stereocomplexes formed by blending enantiomeric PLA block copolymers have demonstrated great potential for applications in biomedical devices. Here, we successfully synthesized well-defined enantiomeric PLA containing block copolymers by living ring-opening polymerization of L- and D-lactides from hydroxyl-terminated hydrophilic [poly(ethylene oxide) or PEO] and hydrophobic [poly(ethylene-co-1,2-butylene) or PEB] oligomers. Quantitative stereocomplex formation was achieved by equimolar mixing of the incompatible PEO-b-PLLA and PEB-b-PDLA. Intriguingly, in the blend of PEB-b-PDLA and PEO-b-PLLA with different PEB and PEO molecular weights, onion-like stereocomplex crystals were observed because of unbalanced surface stresses caused by different PEO and PEB molecular weights.

  2. Effect of poly(ethylene oxide)-silane graft molecular weight on the colloidal properties of iron oxide nanoparticles for biomedical applications.

    PubMed

    Barrera, Carola; Herrera, Adriana P; Bezares, Nayla; Fachini, Estevão; Olayo-Valles, Roberto; Hinestroza, Juan P; Rinaldi, Carlos

    2012-07-01

    The size, charge, and stability of colloidal suspensions of magnetic nanoparticles with narrow size distribution and grafted with poly(ethylene glycol)-silane of different molecular weights were studied in water, biological buffers, and cell culture media. X-ray photoelectron spectroscopy provided information on the chemical nature of the nanoparticle surface, indicating the particle surfaces consisted of a mixture of amine groups and grafted polymer. The results indicate that the exposure of the amine groups on the surface decreased as the molecular weight of the polymer increased. The hydrodynamic diameters correlated with PEG graft molecular weight and were in agreement with a distributed density model for the thickness of a polymer shell end-grafted to a particle core. This indicates that the particles obtained consist of single iron oxide cores coated with a polymer brush. Particle surface charge and hydrodynamic diameter were measured as a function of pH, ionic strength, and in biological buffers and cell culture media. DLVO theory was used to analyze the particle stability considering electrostatic, magnetic, steric, and van der Waals interactions. Experimental results and colloidal stability theory indicated that stability changes from electrostatically mediated for a graft molecular weight of 750 g/mol to sterically mediated at molecular weights of 1000 g/mol and above. These results indicate that a graft molecular weight above 1000 g/mol is needed to produce particles that are stable in a wide range of pH and ionic strength, and in cell culture media.

  3. Filler effect of ionic liquid attached titanium oxide on conducting property of poly(ethylene oxide)/poly(methyl methacrylate) composite electrolytes.

    PubMed

    Lee, Lyungyu; Kim, Ick-Jun; Yang, Sunhye; Kim, Seok

    2014-10-01

    Composite polymer electrolytes (CPEs) were prepared by containing blend of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) as a host polymer, propylene carbonate as a plasticizer, and LiClO4 as a salt. By an addition of a various content of ionic liquid attached TiO2 (IL-TiO2) to above electrolytes, the effects were studied. As a result, by increasing the IL-TiO2 content, the crystallinity of PEO was decreased and the ionic conductivity was increased. The ionic conductivity of CPEs was dependent on the content of IL-TiO2 and showed the highest value of 1.05 x 10(-4) S/cm at 9 wt.%. However, when IL-TiO2 content exceeds 9 wt.%, the ionic conductivity was decreased due to the slow ionic transport due to immiscibility or aggregation of the IL-TiO2 filler within the polymer film matrix.

  4. Effect of hydrophobicity inside PEO-PPO-PEO block copolymer micelles on the stabilization of gold nanoparticles: experiments.

    PubMed

    Chen, Shu; Guo, Chen; Hu, Guo-Hua; Wang, Jing; Ma, Jun-He; Liang, Xiang-Feng; Zheng, Lily; Liu, Hui-Zhou

    2006-11-07

    In this paper we present the effect of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer micelles and their hydrophobicity on the stabilization of gold nanoparticles. Gold nanoparticles were prepared by a method developed by Sakai et al. (Sakai, T.; Alexandridis, P. Langmuir 2004, 20, 8426). An absorption centered at 300-400 nm in time-dependent UV spectra provided evidence that the very first step of the synthesis was to form primary gold clusters. Then the gold clusters grew in size and were stabilized by block copolymer micelles. The stabilization capacities of the micelles were modulated by tuning the block copolymer concentration and composition and by adding salts. With good stabilization, gold particles were spherical and uniform in size with a diameter of 5-10 nm. Otherwise they were aggregates with irregular shapes such as triangular, hexagonal, and rodlike. The presence of a small amount of NaF significantly increased the stabilization capacity of the micelles and consequently modified the quality of the gold particles. Using FTIR and 1H NMR spectroscopy, micellization of the block copolymers and hydrophobicity of the micelles were proven very important for the stabilization. A higher hydrophobicity of the micelle cores was expected to favor the entrapment of primary gold clusters and the stabilization of gold nanoparticles.

  5. Deciphering the Effect of Polymer-Assisted Doping on the Optoelectronic Properties of Block Copolymer-Anchored Graphene Oxide.

    PubMed

    Maity, Nabasmita; Kuila, Atanu; Nandi, Arun K

    2017-02-14

    Doping facilitates the tuning of band gap, providing an opportunity to tailor the optoelectronic properties of graphene in a simple way, and polymer-assisted doping is a new route to combine the optoelectronic properties of graphene with the properties of a polymer. In this endeavor, a linear diblock copolymer, polycaprolactone-block-poly(dimethyl aminoethyl methacrylate) (PCL13-b-PDMAEMA117) (GPCLD) is grafted from the graphene oxide (GO) surface via consecutive ring opening and atom transfer radical polymerization. GPCLD is characterized using proton nuclear magnetic resonance ((1)H NMR), Fourier transform infrared spectroscopy, atomic force microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy. The phase transition behavior of the GPCLD solution with varying temperature and pH is monitored using fluorescence spectroscopy and dynamic light scattering. Temperature-dependent (1)H NMR spectra at pH 9.2 indicate the influence of temperature on the interaction between GPCLD and solvent (water) molecules causing the phase separation. Fluorescence spectra at pH 4 and 9.2 give the evidence of localized p- and n-type doping of graphene assisted by the pendent PDMAEMA chains. In the impedance spectra of GPCLD films, the Nyquist plots vary with pH; at pH 4, they exhibit a semicircle at higher frequencies and a spike at lower frequencies; at pH 7.0, the spike is replaced by an arc; and at pH 9.2, the semicircle at higher frequencies vanishes and only a spike is noticed, all of these suggesting different types of doping of graphene at different pH values. The dc-conductivity also varies with pH and temperature because of the different types of doping. The current (I)-voltage (V) property of GPCLD at different pH values is very unique: at pH 9.2, an interesting feature of negative differential resistance (NDR) is observed; at pH 7, the rectification property is observed; and at pH 4, again the NDR property is observed. The temperature

  6. Polyimide nanofoams for microelectronic applications: Nanofoams derived from 6FXDA/6FDAM-co-polypropylene oxide copolymers

    SciTech Connect

    Carter, K.R.; Labadie, J.W.; DiPietro, R.A.

    1995-12-01

    As part of our research efforts to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices, we have explored polyimide foams created using a block copolymer approach. In these systems the pore sizes are in the manometer range thus the term {open_quotes}nanofoam{close_quotes}. The polyimide foams are prepared from block copolymers consisting of thermally stabile and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block leaving pores the size and shape corresponding to the initial copolymer morphology. Nanofoams of 6FXDA/6FDAm polyimide were investigated. These highly fluorinated polyimide foams showed a drop in refractive index, indicative of a significant lowering of the dielectric constant. The foams were characterized by a variety of techniques including, TEM, SAXS, WAXD, DMTA, density measurements mid refractive index measurement. Thin film, high modulus foams with good mechanical properties can be synthesized using the copolymer/nanofoam approach.

  7. Sans Studies Insight Into Improving of Yield of Block Copolymer-Stabilized Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ray, Debes; Aswal, V. K.

    2010-01-01

    Triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) are well known as dispersion stabilizers. It has also been recently found that they can act as reducing agents along with stabilizers and these two properties of block copolymers together have provided a single-step synthesis and stabilization of gold nanoparticles at ambient temperature. We have studied the synthesis of stable gold nanoparticle solutions using block copolymer P85. Gold nanoparticles are prepared from 1 wt% aqueous solution of P85 mixed with varying concentration of HAuCl4.3H2O salt in the range 0.001 to 0.1 wt%. Surface plasmon resonance (SPR) band in UV-visible absorption spectra confirm the formation of the gold nanoparticles and the maximum yield of the nanoparticles is found to be quite low at 0.005 wt% of the salt solution. Small-angle neutron scattering (SANS) measurements in these systems suggest that a very small fraction of the block copolymers (<1%) is only associated with the gold nanoparticles and remaining form their own micelles, which probably results in the low yield. This can be explained as on an average a high block copolymer-to-gold ion ratio r0 (22) is required for 1 wt% P85 in the reduction reaction to produce gold nanoparticles. Based on this understanding, a step-addition method is used to enhance the yield of gold nanoparticles by manifold where the gold salt is added in small steps to maintain higher value of r(>r0) and therefore continuous formation of nanoparticles.

  8. Pyrolysis result of polyethylene waste as fuel for solid oxide fuel cell with samarium doped-ceria (SDC)-carbonate as electrolyte

    NASA Astrophysics Data System (ADS)

    Syahputra, R. J. E.; Rahmawati, F.; Prameswari, A. P.; Saktian, R.

    2017-02-01

    In this research, the result of pyrolysis on polyethylene was used as fuel for a solid oxide fuel cell (SOFC). The pyrolysis result is a liquid which consists of hydrocarbon chains. According to GC-MS analysis, the hydrocarbons mainly consist of C7 to C20 hydrocarbon chain. Then, the liquid was applied to a single cell of NSDC-L | NSDC | NSDC-L. NSDC is a composite SDC (samarium doped-ceria) with sodium carbonate. Meanwhile, NSDC-L is a composite of NSDC with LiNiCuO (LNC). NSDC and LNC were analyzed by X-ray diffraction to understand their crystal structure. The result shows that presence of carbonate did not change the crystal structure of SDC. SEM EDX analysis for fuel cell before and after being loaded with polyethylene oil to get information of element diffusion to the electrolyte. Meanwhile, the conductivity properties were investigated through impedance measurement. The presence of carbonate even increases the electrical conductivity. The single cell test with the pyrolysis result of polyethylene at 300 – 600 °C, found that the highest power density is at 600 °C with the maximum power density of 0.14 mW/cm2 and open circuit voltage of 0.4 Volt. Elemental analysis at three point spots of single cell NDSC-L |NSDC|NSDC-L found that a migration of ions was occurred during fuel operation at 300 – 600 °C.

  9. Release of bacteriocins from nanofibers prepared with combinations of poly(d,l-lactide) (PDLLA) and poly(ethylene oxide) (PEO).

    PubMed

    Heunis, Tiaan; Bshena, Osama; Klumperman, Bert; Dicks, Leon

    2011-01-01

    Plantaricin 423, produced by Lactobacillus plantarum, and bacteriocin ST4SA produced by Enterococcus mundtii, were electrospun into nanofibers prepared from different combinations of poly(d,l-lactide) (PDLLA) and poly(ethylene oxide) (PEO) dissolved in N,N-dimethylformamide (DMF). Both peptides were released from the nanofibers with a high initial burst and retained 88% of their original antimicrobial activity at 37 °C. Nanofibers have the potential to serve as carrier matrix for bacteriocins and open a new field in developing controlled antimicrobial delivery systems for various applications.

  10. Agarose hydrogels embedded with pH-responsive diblock copolymer micelles for triggered release of substances.

    PubMed

    Jin, Naixiong; Morin, Emily A; Henn, Daniel M; Cao, Yu; Woodcock, Jeremiah W; Tang, Shuangcheng; He, Wei; Zhao, Bin

    2013-08-12

    Hybrid agarose hydrogels embedded with pH-responsive diblock copolymers micelles were developed to achieve functional hydrogels capable of stimulus-triggered drug release. Specifically, a well-defined poly(ethylene oxide) (PEO)-based diblock copolymer, PEO-b-poly(2-(N,N-diisopropylamino)ethyl methacrylate) (PEO(113)-b-PDPAEMA(31), where the subscripts represent the degrees of polymerization of two blocks), was synthesized by atom transfer radical polymerization. PDPAEMA is a pH-responsive polymer with a pKa value of 6.3. The PEO(113)-b-PDPAEMA(31) micelles were formed by a solvent-switching method, and their pH-dependent dissociation behavior was investigated by dynamic light scattering and fluorescence spectroscopy. Both studies indicated that the micelles were completely disassembled at pH = 6.40. The biocompatibility of PEO(113)-b-PDPAEMA(31) micelles was demonstrated by in vitro primary cortical neural culture. Hybrid agarose hydrogels were made by cooling 1.0 wt % agarose solutions that contained various amounts of PEO(113)-b-PDPAEMA(31) micelles at either 2 or 4 °C. Rheological measurements showed that the mechanical properties of gels were not significantly adversely affected by the incorporation of diblock copolymer micelles with a concentration as high as 5.0 mg/g. Using Nile Red as a model hydrophobic drug, its incorporation into the core of diblock copolymer micelles was demonstrated. Characterized by fluorescent spectroscopy, the release of Nile Red from the hybrid hydrogel was shown to be controllable by pH due to the responsiveness of the block copolymer micelles. Based on the prominent use of agarose gels as scaffolds for cell transplantation for neural repair, the hybrid hydrogels embedded with stimuli-responsive block copolymer micelles could allow the controlled delivery of hydrophobic neuroprotective agents to improve survival of transplanted cells in tune with signals from the surrounding pathological environment.

  11. Tissue engineering of fish skin: behavior of fish cells on poly(ethylene glycol terephthalate)/poly(butylene terephthalate) copolymers in relation to the composition of the polymer substrate as an initial step in constructing a robotic/living tissue hybrid.

    PubMed

    Pouliot, Roxane; Azhari, Rosa; Qanadilo, Hala F; Mahmood, Tahir A; Triantafyllou, Michael S; Langer, Robert

    2004-01-01

    This study presents the development of a biosynthetic fish skin to be used on aquatic robots that can emulate fish. Smoothness of the external surface is desired in improving high propulsive efficiency and maneuvering agility of autonomous underwater vehicles such as the RoboTuna (Triantafyllou, M., and Triantafyllou, G. Sci. Am. 272, 64, 1995). An initial step was to determine the seeding density and select a polymer for the scaffolds. The attachment and proliferation of chinook salmon embryo (CHSE-214) and brown bullhead (BB) cells were studied on different compositions of a poly(ethylene glycol terephthalate) (PEGT) and poly(butylene terephthalate) (PBT) copolymer (Polyactive). Polymer films were used, cast of three different compositions of PEGT/PBT (weight ratios of 55/45, 60/40, and 70/30) and two different molecular masses of PEGT (300 and 1000 Da). When a 55 wt% and a 300-Da molecular mass form of PEGT was used, maximum attachment and proliferation of CHSE-214 and BB cells were achieved. Histological studies and immunostaining indicate the presence of collagen and cytokeratins in the extracellular matrix formed after 14 days of culture. Porous scaffolds of PEGT/PBT copolymers were also used for three-dimensional tissue engineering of fish skin, using BB cells. Overall, our results indicate that fish cells can attach, proliferate, and express fish skin components on dense and porous Polyactive scaffolds.

  12. Nuclear magnetic resonance investigation of dynamics in poly(ethylene oxide) based polyether-ester-sulfonate ionomers

    NASA Astrophysics Data System (ADS)

    Roach, David J.

    Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies for motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though lithium hopping is about ten times slower than the segmental motion. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments. Polymer backbone dynamics of single ion conducting poly(ethylene oxide) (PEO)-based ionomer samples with low glass transition temperatures (T g) have been investigated using solid-state nuclear magnetic resonance (NMR). Experiments detecting 13C with 1H decoupling under magic angle spinning (MAS) conditions identified the different components and relative mobilities of the polymer backbone of a suite of. lithium- and sodium-containing ionomer samples with varying cation contents. Variable temperature (203-373 K) 1H-13C cross-polarization MAS (CP-MAS) experiments also provided qualitative assessment of the differences in the motions of the polymer backbone components as a function of

  13. "Non-equilibrium" block copolymer micelles with glassy cores: a predictive approach based on theory of equilibrium micelles.

    PubMed

    Nagarajan, Ramanathan

    2015-07-01

    Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to

  14. Bioinspired catecholic copolymers for antifouling surface coatings.

    PubMed

    Cho, Joon Hee; Shanmuganathan, Kadhiravan; Ellison, Christopher J

    2013-05-01

    We report here a synthetic approach to prepare poly(methyl methacrylate)-polydopamine diblock (PMMA-PDA) and triblock (PDA-PMMA-PDA) copolymers combining mussel-inspired catecholic oxidative chemistry and atom transfer radical polymerization (ATRP). These copolymers display very good solubility in a range of organic solvents and also a broad band photo absorbance that increases with increasing PDA content in the copolymer. Spin-cast thin films of the copolymer were stable in water and showed a sharp reduction (by up to 50%) in protein adsorption compared to those of neat PMMA. Also the peak decomposition temperature of the copolymers was up to 43°C higher than neat PMMA. The enhanced solvent processability, thermal stability and low protein adsorption characteristics of this copolymer makes it attractive for variety of applications including antifouling coatings on large surfaces such as ship hulls, buoys, and wave energy converters.

  15. Growth of ordered silver nanoparticles in silica film mesostructured with a triblock copolymer PEO-PPO-PEO

    SciTech Connect

    Bois, L.; Chassagneux, F.; Parola, S.; Bessueille, F.; Battie, Y.; Destouches, N.; Boukenter, A.; Moncoffre, N.

    2009-07-15

    Elaboration of mesostructured silica films with a triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide, (PEO-PPO-PEO) and controlled growth of silver nanoparticles in the mesostructure are described. The films are characterized using UV-visible optical absorption spectroscopy, TEM, AFM, SEM, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Organized arrays of spherical silver nanoparticles with diameter between 5 and 8 nm have been obtained by NaBH{sub 4} reduction. The size and the repartition of silver nanoparticles are controlled by the film mesostructure. The localization of silver nanoparticles exclusively in the upper-side part of the silica-block copolymer film is evidenced by RBS experiment. On the other hand, by using a thermal method, 40 nm long silver sticks can be obtained, by diffusion and coalescence of spherical particles in the silica-block copolymer layer. In this case, migration of silver particles toward the glass substrate-film interface is shown by the RBS experiment. - Graphical abstract: Growth of silver nanoparticles in a mesostructured block copolymer F127-silica film is performed either by a chemical route involving NaBH{sub 4} reduction or by a thermal method. An array of spherical silver nanoparticles with 10 nm diameter on the upper-side of the mesostructured film or silver sticks long of 40 nm with a preferential orientation are obtained according to the method used. a: TEM image of the Fag5SiNB sample illustrating the silver nanoparticles array obtained by the chemical process; b: HR-TEM image of the Fag20Sid2 sample illustrating the silver nanosticks obtained by the thermal process.

  16. Poly(ethylene oxide)-silica hybrids entrapping sensitive dyes for biomedical optical pH sensors: Molecular dynamics and optical response

    NASA Astrophysics Data System (ADS)

    Fabbri, Paola; Pilati, Francesco; Rovati, Luigi; McKenzie, Ruel; Mijovic, Jovan

    2011-06-01

    Polymer-silica hybrid nanocomposites prepared by sol-gel process based on triethoxisilane-terminated poly(ethylene oxide) chains and tetraethoxysilane as silica precursor, doped with organic pH sensitive dyes, have been prepared and their suitability for use as sensors coupled with plastic optic fibers has been evaluated. Sensors were prepared by immobilizing a drop of the hybrid materials onto the tip of a multi-mode poly(methyl methacrylate) optical fiber. The performance of the optical sensor in terms of sensitivity and response time was tested in different experimental conditions, and was found to be markedly higher than analogous sensors present on the market. The very fast kinetic of the hybrid's optical response was supported by studies performed at the molecular level by broadband dielectric relaxation spectroscopy (DRS), investigated over a wide range of frequency and temperature, showing that poly(ethylene oxide) chains maintain their dynamics even when covalently bonded to silica domains, which decrease the self-association interactions and promote motions of polymer chain segments. Due to the fast response kinetic observed, these pH optical sensors result suitable for the fast-detection of biomedical parameters, i.e. fast esophageous pH-metry.

  17. Curcumin Encapsulated into Methoxy Poly(Ethylene Glycol) Poly(ε-Caprolactone) Nanoparticles Increases Cellular Uptake and Neuroprotective Effect in Glioma Cells.

    PubMed

    Marslin, Gregory; Sarmento, Bruno Filipe Carmelino Cardoso; Franklin, Gregory; Martins, José Alberto Ribeiro; Silva, Carlos Jorge Ribeiro; Gomes, Andreia Ferreira Castro; Sárria, Marisa Passos; Coutinho, Olga Maria Fernandes Pereira; Dias, Alberto Carlos Pires

    2017-03-01

    Curcumin is a natural polyphenolic compound isolated from turmeric (Curcuma longa) with well-demonstrated neuroprotective and anticancer activities. Although curcumin is safe even at high doses in humans, it exhibits poor bioavailability, mainly due to poor absorption, fast metabolism, and rapid systemic elimination. To overcome these issues, several approaches, such as nanoparticle-mediated targeted delivery, have been undertaken with different degrees of success. The present study was conducted to compare the neuroprotective effect of curcumin encapsulated in poly(ε-caprolactone) and methoxy poly(ethylene glycol) poly(ε-caprolactone) nanoparticles in U251 glioblastoma cells. Prepared nanoparticles were physically characterized by laser doppler anemometry, transmission electron microscopy, and X-ray diffraction. The results from laser doppler anemometry confirmed that the size of poly(ε-caprolactone) and poly(ethylene glycol) poly(ε-caprolactone) nanoparticles ranged between 200-240 nm for poly(ε-caprolactone) nanoparticles and 30-70 nm for poly(ethylene glycol) poly(ε-caprolactone) nanoparticles, and transmission electron microscopy images revealed their spherical shape. Treatment of U251 glioma cells and zebrafish embryos with poly(ε-caprolactone) and poly(ethylene glycol) poly(ε-caprolactone) nanoparticles loaded with curcumin revealed efficient cellular uptake. The cellular uptake of poly(ethylene glycol) poly(ε-caprolactone) nanoparticles was higher in comparison to poly(ε-caprolactone) nanoparticles. Moreover, poly(ethylene glycol) poly(ε-caprolactone) di-block copolymer-loaded curcumin nanoparticles were able to protect the glioma cells against tBHP induced-oxidative damage better than free curcumin. Together, our results show that curcumin-loaded poly(ethylene glycol) poly(ε-caprolactone) di-block copolymer nanoparticles possess significantly stronger neuroprotective effect in U251 human glioma cells compared to free curcumin and curcumin

  18. Preparation and in vitro evaluation of Methotrexate-loaded magnetic nanoparticles modified with biocompatible copolymers.

    PubMed

    Jahangiri, Sahar; Akbarzadeh, Abolfazl

    2016-11-01

    Superparamagnetic iron oxide nanoparticles (SPION) are attractive materials that have been widely used in medicine for drug delivery, diagnostic imaging and therapeutic applications. In our study, SPION and the anticancer drug, Methotrexate, were encapsulated into polycaprolactone-polyethylene glycol (PCL-PEG) nanoparticles for local treatment. The magnetic properties conferred by SPION could help to maintain the nanoparticles in the joint with an external magnet. The drug encapsulation efficiency achieved for Fe3O4 magnetic nanoparticles modified with PCL-PEG copolymer was 92.36%. There is potential for use of these nanoparticles for biomedical application.

  19. Diblock Copolymer Micelles and Supported Films with Noncovalently Incorporated Chromophores: A Modular Platform for Efficient Energy Transfer

    SciTech Connect

    Adams, Peter G.; Collins, Aaron M.; Sahin, Tuba; Subramanian, Vijaya; Urban, Volker S.; Vairaprakash, Pothiappan; Tian, Yongming; Evans, Deborah G.; Shreve, Andrew P.; Montaño, Gabriel A.

    2015-04-08

    Here we report generation of modular, artificial light-harvesting assemblies where an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(butadiene), serves as the framework for noncovalent organization of BODIPY-based energy donor and bacteriochlorin-based energy acceptor chromophores. The assemblies are adaptive and form well-defined micelles in aqueous solution and high-quality monolayer and bilayer films on solid supports, with the latter showing greater than 90% energy transfer efficiency. Ultimately, this study lays the groundwork for further development of modular, polymer-based materials for light harvesting and other photonic applications.

  20. Modified release from lipid bilayer coated mesoporous silica nanoparticles using PEO-PPO-PEO triblock copolymers.

    PubMed

    Rahman, Masoud; Yu, Erick; Forman, Evan; Roberson-Mailloux, Cameron; Tung, Jonathan; Tringe, Joseph; Stroeve, Pieter

    2014-10-01

    Triblock copolymers comprised of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, or trade name Pluronic) interact with lipid bilayers to increase their permeability. Here we demonstrate a novel application of Pluronic L61 and L64 as modification agents in tailoring the release rate of a molecular indicator species from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer-coated superparamagnetic Fe3O4/mesoporous silica core-shell nanoparticles. We show there is a direct relationship between the Pluronics' concentration and the indicator molecule release, suggesting Pluronics may be useful for the controlled release of drugs from lipid bilayer-coated carriers.

  1. Self-Assembly of Pluronic Block Copolymers in Solutions: Simulation and Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Hong, Kunlun; Do, Changwoo; Biology and Soft-Matter Division, Oak Ridge National Laboratory Team; Chemical Science Division, Oak Ridge National Laboratory Team

    2014-03-01

    Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers in water solution display various phase behaviors such as micellar, lamellar, and hexagonal phases and have been of great interest to researchers for their wide range of applications including templates of various nanostructures in solar cell and transportation of nanoparticles in drug delivery. In this study, we combined density functional theory-based mesoscale simulation and small-angle neutron scattering (SANS) experiments to investigate equilibrium structures of L62/water systems at different concentrations. Various simulation parameters found in the literature have been revisited with the experimental findings. Scattering experiments were found to be an excellent. This research is supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Energy Division.

  2. Interaction of Curcumin with PEO-PPO-PEO block copolymers: a molecular dynamics study.

    PubMed

    Samanta, Susruta; Roccatano, Danilo

    2013-03-21

    Curcumin, a naturally occurring drug molecule, has been extensively investigated for its various potential usages in medicine. Its water insolubility and high metabolism rate require the use of drug delivery systems to make it effective in the human body. Among various types of nanocarriers, block copolymer based ones are the most effective. These polymers are broadly used as drug-delivery systems, but the nature of this process is poorly understood. In this paper, we propose a molecular dynamics simulation study of the interaction of Curcumin with block copolymer based on polyethylene oxide (PEO) and polypropylene oxide (PPO). The study has been conducted considering the smallest PEO and PPO oligomers and multiple chains of the block copolymer Pluronic P85. Our study shows that the more hydrophobic 1,2-dimethoxypropane (DMP) molecules and PPO block preferentially coat the Curcumin molecule. In the case of the Pluronic P85, simulation shows formation of a drug-polymer aggregate within 50 ns. This process leaves exposed the PEO part of the polymers, resulting in better solvation and stability of the drug in water.

  3. End Group Effects on the Hydrogel Formation of PEO-PPO-PEO Triblock Copolymers

    NASA Astrophysics Data System (ADS)

    Cohen, Aaron; Ryu, Chang Y.; Jung, Gyoo Y.; Hwang, Hee Sung

    2012-02-01

    Pluronic F108, a triblock copolymer consisting of outer polyethylene oxide (PEO) chains and an inner polypropylene oxide (PPO) chains, has been shown to be an effective hydrogel matrix for DNA separation by capillary electrophoresis using single-stranded conformation polymorphism. This presentation will discuss a new pathway to potentially enhance the separation abilities of F108 by altering the chain end groups of the block copolymers. F108 is believed to form a micelle in aqueous solutions with the hydrophobic group in the interior, thus we expect considerable interaction between the DNA sample and the end groups found at the hydrophilic brush layers of the micelle. The rheological properties of end group derivatives of F108, in combination of small angle x-ray scattering, can reveal structural differences in the micelles. In particular, gelation temperature of the end group derivatives can be linked to differences in the micelle structure. Dynamic light scattering can also be used to determine the effects of chain end groups on the hydrodynamic size of the block copolymer micelles in dilute solution.

  4. Experimental and modeling approaches for the formation of hydroperoxide during the auto-oxidation of polymers: Thermal-oxidative degradation of polyethylene oxide

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Yamane, Shogo; Sago, Tomohiro; Hagihara, Hideaki; Kutsuna, Shuzo; Uchimaru, Tadafumi; Suda, Hiroyuki; Sato, Hiroaki; Mizukado, Junji

    2016-07-01

    ROOH was a key intermediate compound in oxidation of polymer because it was only source of radOH radicals. ROOH was believed to be produced by ROOrad abstraction H-atom from polymer, which is thermodynamically unfavorable, but it may be facilitated due to the high polymer concentration. However, ROOH also could be produced by ROOrad reaction with HO2rad. For examining the formation scheme of ROOH, kinetics and mechanism for the thermal-oxidative degradation of PEO at 473 K in air was investigated by using the experimental and modeling approaches. The contribution of HO2rad reaction with ROOrad to the formation of ROOH was estimated.

  5. Safety Evaluation of Polyethylene Glycol (PEG) Compounds for Cosmetic Use

    PubMed Central

    Shin, Chan Young; Kim, Kyu-Bong

    2015-01-01

    Polyethylene glycols (PEGs) are products of condensed ethylene oxide and water that can have various derivatives and functions. Since many PEG types are hydrophilic, they are favorably used as penetration enhancers, especially in topical dermatological preparations. PEGs, together with their typically nonionic derivatives, are broadly utilized in cosmetic products as surfactants, emulsifiers, cleansing agents, humectants, and skin conditioners. The compounds studied in this review include PEG/PPG-17/6 copolymer, PEG-20 glyceryl triisostearate, PEG-40 hydrogenated castor oil, and PEG-60 hydrogenated castor oil. Overall, much of the data available in this review are on PEGylated oils (PEG-40 and PEG-60 hydrogenated castor oils), which were recommended as safe for use in cosmetics up to 100% concentration. Currently, PEG-20 glyceryl triisostearate and PEGylated oils are considered safe for cosmetic use according to the results of relevant studies. Additionally, PEG/PPG-17/6 copolymer should be further studied to ensure its safety as a cosmetic ingredient. PMID:26191379

  6. Electrochemical Deposition Of Conductive Copolymers

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, Ganesan; Distefano, Salvador; Liang, Ranty H.

    1991-01-01

    Experiments show electrically conductive films are deposited on glassy carbon or indium tin oxide substrates by electrochemical polymerization of N-{(3-trimethoxy silyl) propyl} pyrrole or copolymerization with pyrrole. Copolymers of monomer I and pyrrole exhibit desired electrical conductivity as well as desired adhesion and other mechanical properties. When fully developed, new copolymerization process useful in making surface films of selectable conductivity.

  7. Biodegradation of the composites based on polyethylene and sevilene with natural rubber

    NASA Astrophysics Data System (ADS)

    Kolesnikova, N. N.; Lukanina, Yu. K.; Popov, A. A.

    2013-10-01

    The mechanical properties, the water absorption, and the resistance to soil microrbiota of the composite films based on polyethylene and ethylene-vinyl acetate copolymers with additives of natural rubber are studied. The intensity of the biodegradation of the composites is shown to depend on both the mixture composition and the content of vinyl acetate units in a copolymer.

  8. Polyethylene glycol grafted flower-like cupric nano oxide for the hollow-fiber solid-phase microextraction of hexaconazole, penconazole, and diniconazole in vegetable samples.

    PubMed

    Zendegi-Shiraz, Amene; Sarafraz-Yazdi, Ali; Es'haghi, Zarrin

    2016-08-01

    A simple, rapid, highly efficient, and reliable sample preparation method has been developed for the extraction and analysis of triazole pesticides from cucumber, lettuce, bell pepper, cabbage, and tomato samples. This new sorbent in the hollow-fiber solid-phase microextraction method is based on the synthesis of polyethylene glycol-polyethylene glycol grafted flower-like cupric oxide nanoparticles using sol-gel technology. Afterward, the analytes were analyzed by high-performance liquid chromatography with ultraviolet detection. The main parameters that affect microextraction efficiency were evaluated and optimized. This method has afforded good linearity ranges (0.5-50 000 ng/mL for hexaconazol, 0.012-50 000 ng/mL for penconazol, and 0.02-50 000 ng/mL for diniconazol), adequate precision (2.9-6.17%, n = 3), batch-to-batch reproducibility (4.33-8.12%), and low instrumental LODs between 0.003 and 0.097 ng/mL (n = 8). Recoveries and enrichment factors were 85.46-97.47 and 751-1312%, respectively.

  9. Structural and optical properties of Ag-doped copper oxide thin films on polyethylene napthalate substrate prepared by low temperature microwave annealing

    SciTech Connect

    Das, Sayantan; Alford, T. L.

    2013-06-28

    Silver doped cupric oxide thin films are prepared on polyethylene naphthalate (flexible polymer) substrates. Thin films Ag-doped CuO are deposited on the substrate by co-sputtering followed by microwave assisted oxidation of the metal films. The low temperature tolerance of the polymer substrates led to the search for innovative low temperature processing techniques. Cupric oxide is a p-type semiconductor with an indirect band gap and is used as selective absorption layer solar cells. X-ray diffraction identifies the CuO phases. Rutherford backscattering spectrometry measurements confirm the stoichiometry of each copper oxide formed. The surface morphology is determined by atomic force microscopy. The microstructural properties such as crystallite size and the microstrain for (-111) and (111) planes are calculated and discussed. Incorporation of Ag led to the lowering of band gap in CuO. Consequently, it is determined that Ag addition has a strong effect on the structural, morphological, surface, and optical properties of CuO grown on flexible substrates by microwave annealing. Tauc's plot is used to determine the optical band gap of CuO and Ag doped CuO films. The values of the indirect and direct band gap for CuO are found to be 2.02 eV and 3.19 eV, respectively.

  10. The effect of self-assembly conditions on the size of di- and tri-block copolymer micelles: solicitation from response surface methodology.

    PubMed

    Honary, Soheila; Lavasanifar, Afsaneh

    2014-08-27

    Abstract The objective of this study was to assess the application of Response Surface Methodology in defining the effect of self-assembly condition on the average diameter of polymeric micelles. Di- and tri-block copolymers of poly(ethylene oxide)-b-poly(α-benzylcarboxylate-ϵ-caprolactone) (PEO-PBCL) and PBCL-b-poly(ethylene glycol)-b-PBCL (PBCL-PEG-PBCL) were synthesized through ring opening polymerization of α-benzyl-ε-carboxylate using MePEO or dihydroxy PEG as initiator, respectively. Polymeric micelles were formed through solubilization of block copolymers in acetone followed by drop-wise addition of this solution to water. Polymer concentration was changed and the intensity mean diameter of self-assembled structures was measured by dynamic light scattering. The experimental data were fitted to a mathematical model. The experimental conditions leading to the production of micelles of certain size (30, 60 or 90 nm for tri-block and 30 nm for di-block copolymers) was predicted. A good match between predicted and experimental data was observed. The results showed it would be possible to obtain micelles of certain size using block copolymers of different molecular weights or obtain micelles of different size at a given block copolymer molecular weight, by manipulating the polymer concentration. These observations show reproducible micelles of defined average diameter can be prepared by co-solvent evaporation by controlling the used polymer concentration.

  11. Pentablock copolymers of poly(ethylene glycol), poly((2-dimethyl amino)ethyl methacrylate) and poly(2-hydroxyethyl methacrylate) from consecutive atom transfer radical polymerizations for non-viral gene delivery.

    PubMed

    Xu, Fu-Jian; Li, Hongzhe; Li, Jun; Zhang, Zhongxing; Kang, En-Tang; Neoh, Koon-Gee

    2008-07-01

    Well-defined pentablock copolymers (PBPs) of P(HEMA)-b-P(DMAEMA)-b-PEG-b-P(DMAEMA)-b-P(HEMA) (in which PEG=poly(ethylene glycol), P(DMAEMA)=poly((2-dimethyl amino)ethyl methacrylate), and P(HEMA)=poly(2-hydroxyethyl methacrylate)), with different block lengths of P(DMAEMA), for non-viral gene delivery were prepared via consecutive atom transfer radical polymerizations (ATRPs) from the same di-2-bromoisobutyryl-terminated PEG (Br-PEG-Br) center block. The PBPs demonstrate good ability to condense plasmid DNA (pDNA) into 100-160 nm size nanoparticles with positive zeta potentials of 25-35 mV at PBPs/pDNA weight ratios of 5-25. The PBPs exhibit very low in vitro cytotoxicity and excellent gene transfection efficiency in HEK293 and COS7 cells. In particular, the transfection efficiencies of all the PBPs in HEK293 cells are comparable to, or higher than those of polyethylenimine (PEI, 25 kDa) at most weight ratios. The ability of the copolymers to condense plasmid DNA and the transfection efficiency of the resulting complexes are dependent on the chain length of P(DMAEMA) blocks. In addition to reducing the cytotoxicity and increasing the stability of the plasmid complexes, the PEG center block and the short P(HEMA) end blocks also help to enhance the gene transfection efficiency. Thus, the approach to well-defined block copolymers via ATRP provides a versatile means for tailoring the structure of non-viral gene vectors to meet the requirements of low cytotoxicity, good stability and high transfection capability for gene therapy applications.

  12. Oxidation and biodegradation of polyethylene films containing pro-oxidantadditives: Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation on the oxidation and biodegradation of linear low density poly (ethylene) PE-LLD films containing pro-oxidant were examined. To achieve oxidation and degradation, films were first exposed to the sunlight for 93 days du...

  13. pH-dependent mucoadhesion of a poly(N-isopropylacrylamide) copolymer reveals design rules for drug delivery.

    PubMed

    Zhu, X; Degraaf, J; Winnik, F M; Leckband, D

    2004-11-23

    This study investigated the mucoadhesive property of a hydrophobically modified copolymer N-isopropylacryamide and glycidylacrylamide NIPAM-N-Gly-(C18)2 (NIPAM-Gly). Prior studies demonstrated that the interfacial properties of this copolymer are pH dependent and that the chains form strong hydrogen bonds at pH < 7 via the carboxylic acid side chains of the glycine moieties. Mucin interactions with the copolymer brushes were investigated by surface plasmon resonance and by direct force measurements. Mucin adsorption was determined as a function of pH, ionic strength, and mucin concentration. It adsorbs to the copolymer strongly at pH 5, but the adsorption decreases with increasing pH. The adsorbed amount is also ionic-strength dependent, decreasing with increasing monovalent salt concentrations at all pH values investigated. When compared with similar investigations with poly(ethylene oxide), these results provide insights into both the chemical characteristics and the solution conditions that determine the mucoadhesive properties of polymers.

  14. Effect of poly(ethylene oxide) on ionic conductivity and electrochemical properties of poly(vinylidenefluoride) based polymer gel electrolytes prepared by electrospinning for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Prasanth, Raghavan; Shubha, Nageswaran; Hng, Huey Hoon; Srinivasan, Madhavi

    2014-01-01

    Effect of poly(ethylene oxide) on the electrochemical properties of polymer electrolyte based on electrospun, non-woven membrane of PVdF is demonstrated. Electrospinning process parameters are controlled to get a fibrous membrane consisting of bead-free, uniformly dispersed thin fibers with diameter in the range of 1.5-1.9 μm. The membrane with good mechanical strength and porosity exhibits high uptake when activated with the liquid electrolyte of lithium salt in a mixture of organic solvents. The polymer gel electrolyte shows ionic conductivity of 4.9 × 10-3 S cm-1 at room temperature. Electrochemical performance of the polymer gel electrolyte is evaluated in Li/polymer electrolyte/LiFePO4 coin cell. Good performance with low capacity fading on charge-discharge cycling is demonstrated.

  15. A mechanistic study explaining the synergistic viscosity increase obtained from polyethylene oxide (PEO) and {beta}-naphthalene sulfonate (BNS) in shotcrete

    SciTech Connect

    Pickelmann, J.; Plank, J.

    2012-11-15

    In shotcrete, a combination of polyethylene oxide (PEO) and {beta}-naphthalene sulfonate (BNS) is commonly applied to reduce rebound. Here, the mechanism for the synergistic viscosity increase resulting from this admixture combination was investigated via x-ray diffraction (XRD), infrared and nuclear magnetic resonance (NMR) spectroscopy. It was found that the electron-rich aromatic rings present in BNS donate electrons to the alkyl protons of PEO and thus increase the electron density there. This rare interaction is known as CH-{pi} interaction and leads to the formation of a supramolecular structure whereby PEO chains bind weakly to BNS molecules. Through this mechanism a polymer network exhibiting exceptionally high molecular weight and thus viscosity is formed. Among polycondensates, sulfanilic acid-phenol-formaldehyde (SPF) provides even higher synergy with PEO than BNS while melamine (PMS), acetone (AFS) or polycarboxylate (PCE) based superplasticizers do not work at all. Effectiveness of lignosulfonates is dependent on their degree of sulfonation.

  16. Controlling solidification and fiber diameter of Polyethylene oxide nanofibers electrospun from aqueous solution by controlling the partial pressure of water vapor

    NASA Astrophysics Data System (ADS)

    Tripatanasuwan, Sureeporn; Zhong, Zhenxin; Reneker, Darrell

    2007-03-01

    Electrospinning is widely in research attention due to its cost effectiveness and straightforwardness for making nanofibers. During the electrospinning process, a charged jet is elongated by repulsive force between electrical charges carried by the jet. The charged jet develops spiral path due to the electrically driven bending instability, which make it possible for the jet to elongate and produce nanofibers in a small space. Solidification has been identified as an important factor that determines the diameter of electrospun nanofibers. The elongation and thinning of a charged jet stops as the charged jet is solidified. Controlling solidification of the charged jet by controlling of partial vapor of water in electrospinning of polyethylene oxide from aqueous solution has been demonstrated in this study. As the partial vapor of water increase, the solidification process of the charged jet becomes slower, allowing elongation of charged jet to continue.

  17. Synthesis and Characterization of Luminescent Eu(TTA)3phen in a Poly(ethylene oxide) Matrix for Detecting Traces of Water

    NASA Astrophysics Data System (ADS)

    Choi, Pu-Reun; Park, Hyung-Ho; Koo, Eunhae

    2013-05-01

    The water vapor transmission rate (WVTR) is limited to 10-6 g/m2/day for flexible organic light-emitting diodes. However, it is difficult to measure permeability as low as 10-6 g/m2/day with current commercial testing methods. To address this need, a developed optochemical method which is extremely sensitive to oxygen or water shows promise. In this study, an Eu complex is synthesized and characterized as a fluorescent probe for detecting traces of water molecules. The Eu-complex film dispersed in poly(ethylene oxide) has strong red fluorescence that is easily quenched by a trace of water. Based on the photoluminescence spectra, the detection limit of the film to water appears to be below 1.0 × 10-9 g/cc. This suggests that the Eu-complex film can be used as a film sensor to measure WVTRs below 10-6 g/m2/day.

  18. Physical, thermodynamics, and transport properties for carbon dioxide and nitrous oxide in solutions of diethanolamine or di-2-propanolamine in polyethylene glycol

    SciTech Connect

    Davis, R.A.; Menendez, R.E.; Sandall, O.C. . Dept. of Chemical and Nuclear Engineering)

    1993-01-01

    Several properties important for the absorption of carbon dioxide and nitrous oxide in solutions of diethanolamine (DEA) or di-2-propanolamine (DIPA) and polyethylene glycol (PEG 400, average molecular weight 400) were determined experimentally. These properties include the density and viscosity of the amine-PEG 400 solutions, the physical solubility and diffusivity of CO[sub 2] in PEG 400, and the physical solubility and diffusivity of N[sub 2]O in DEA-PEG 400 and DIPA-PEG 400 solutions. The results were obtained for 0-300 wt% amine in PEG 400 over the temperature range of 20-40C. The results were correlated for temperature and composition dependence.

  19. Sign change of the Soret coefficient of poly(ethylene oxide) in water/ethanol mixtures observed by thermal diffusion forced Rayleigh scattering.

    PubMed

    Kita, Rio; Wiegand, Simone; Luettmer-Strathmann, Jutta

    2004-08-22

    Soret coefficients of the ternary system of poly(ethylene oxide) in mixed water/ethanol solvent were measured over a wide solvent composition range by means of thermal diffusion forced Rayleigh scattering. The Soret coefficient S(T) of the polymer was found to change sign as the water content of the solvent increases with the sign change taking place at a water mass fraction of 0.83 at a temperature of 22 degrees C. For high water concentrations, the value of S(T) of poly(ethylene oxide) is positive, i.e., the polymer migrates to the cooler regions of the fluid, as is typical for polymers in good solvents. For low water content, on the other hand, the Soret coefficient of the polymer is negative, i.e., the polymer migrates to the warmer regions of the fluid. Measurements for two different polymer concentrations showed a larger magnitude of the Soret coefficient for the smaller polymer concentration. The temperature dependence of the Soret coefficient was investigated for water-rich polymer solutions and revealed a sign change from negative to positive as the temperature is increased. Thermodiffusion experiments were also performed on the binary mixture water/ethanol. For the binary mixtures, the Soret coefficient of water was observed to change sign at a water mass fraction of 0.71. This is in agreement with experimental results from the literature. Our results show that specific interactions (hydrogen bonds) between solvent molecules and between polymer and solvent molecules play an important role in thermodiffusion for this system.

  20. Investigation of space charge distribution of low-density polyethylene/GO-GNF (graphene oxide from graphite nanofiber) nanocomposite for HVDC application.

    PubMed

    Kim, Yoon Jin; Ha, Son-Tung; Lee, Gun Joo; Nam, Jin Ho; Ryu, Ik Hyun; Nam, Su Hyun; Park, Cheol Min; In, Insik; Kim, Jiwan; Han, Chul Jong

    2013-05-01

    This paper reported a research on space charge distribution in low-density polyethylene (LDPE) nanocomposites with different types of graphene and graphene oxide (GO) at low filler content (0.05 wt%) under high DC electric field. Effect of addition of graphene oxide or graphene, its dispersion in LDPE polymer matrix on the ability to suppress space charge generation will be investigated and compared with MgO/LDPE nanocomposite at the same filler concentration. At an applied electric field of 80 kV/mm, a positive packet-like charge was observed in both neat LDPE, MgO/LDPE, and graphene/LDPE nanocomposites, whereas only little homogenous space charge was observed in GO/LDPE nanocomposites, especially with GO synthesized from graphite nano fiber (GNF) which is only -100 nm in diameter. Our research also suggests that dispersion of graphene oxide particles on the polymer matrix plays a significant role to the performance of nanocomposites on suppressing packet-like space charge. From these results, it is expected that nano-sized GO synthesized from GNF can be a promising filler material to LDPE composite for HVDC applications.

  1. Evaluation of the drug solubility and rush ageing on drug release performance of various model drugs from the modified release polyethylene oxide matrix tablets.

    PubMed

    Shojaee, Saeed; Nokhodchi, Ali; Maniruzzaman, Mohammed

    2017-02-01

    Hydrophilic matrix systems are currently some of the most widely used drug delivery systems for controlled-release oral dosage forms. Amongst a variety of polymers, polyethylene oxide (PEO) is considered an important material used in pharmaceutical formulations. As PEO is sensitive to thermal oxidation, it is susceptible to free radical oxidative attack. The aim of this study was to investigate the stability of PEO based formulations containing different model drugs with different water solubility, namely propranolol HCl, theophylline and zonisamide. Both polyox matrices 750 and 303 grade were used as model carriers for the manufacture of tablets stored at 40 °C. The results of the present study suggest that the drug release from the matrix was affected by the length of storage conditions, solubility of drugs and the molecular weight of the polymers. Generally, increased drug release rates were prevalent in soluble drug formulations (propranolol) when stored at the elevated temperature (40 °C). In contrast, it was not observed with semi soluble (theophylline) and poorly soluble (zonisamide) drugs especially when formulated with PEO 303 polymer. This indicates that the main parameters controlling the drug release from fresh polyox matrices are the solubility of the drug in the dissolution medium and the molecular weight of the polymer. DSC traces indicated that that there was a big difference in the enthalpy and melting points of fresh and aged PEO samples containing propranolol, whereas the melting point of the aged polyox samples containing theophylline and zonisamide was unaffected. Graphical abstract ᅟ.

  2. Vibrational spectroscopy of ultra-high molecular weight polyethylene hip prostheses: influence of the sterilisation method on crystallinity and surface oxidation

    NASA Astrophysics Data System (ADS)

    Taddei, Paola; Affatato, Saverio; Fagnano, Concezio; Bordini, Barbara; Tinti, Anna; Toni, Aldo

    2002-08-01

    Due to its high strength and low creep, ultra-high molecular weight polyethylene (UHMWPE) has been used for 30 years in the replacement of damaged articulating cartilage for total joint replacement surgery. In this study, micro-Raman spectroscopy was used to investigate the effects of the sterilisation method (gamma and ethylene oxide (EtO) treatment) on the crystallinity changes of UHMWPE acetabular cups. The crystallinity of the cups was evaluated by micro-Raman spectroscopy coupled to the partial least square (PLS) regression as a function of the inner surface position. Unworn gamma-sterilised cups were found to be significantly more crystalline than the EtO-sterilised ones. No significant differences were observed between the crystallinity values of worn (in in vitro tests) and unworn cups for each type of sterilisation, showing that the changes in surface crystallinity were mainly caused by irradiation rather than by mechanical friction during the in vitro wear tests. These results were discussed in relation to gravimetric measurements, which revealed at the end of the in vitro tests, a higher mean weight loss for the EtO-sterilised cups than for the gamma-sterilised ones. No significant amounts of oxidative degradation products were detected by IR spectroscopy in the inner surface of the EtO-sterilised worn and unworn cups. Regarding the gamma-sterilised cups, the oxidation level appeared to be slightly higher in the centre of the worn cups than on their borders.

  3. [Effect of crystallization and branch on fine structure of orthorhombic in polyethylene].

    PubMed

    Kang, N; Xu, Y; Weng, S; Wu, J; Xu, D

    2001-02-01

    The CH2 rocking bands are used as a probe to monitor the crystalline behavior of polyethylene segments in a series of poly (ethylene-octene) copolymers. High resolution and cryogenic FTIR spectra reveal that different composition and/or crystalline condition of the copolymers result in significant variation on the CH2 rocking bands including the change in peak position, band width and A730/A720. We conclude that side chain in the copolymer can influence the structure of the orthorhombic polyethylene crystallite although they can not enter the crystal lattice.

  4. Molecular weight determination of block copolymers by pulsed gradient spin echo NMR.

    PubMed

    Barrère, Caroline; Mazarin, Michaël; Giordanengo, Rémi; Phan, Trang N T; Thévand, André; Viel, Stéphane; Charles, Laurence

    2009-10-01

    Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) is the technique of choice to achieve molecular weight data for synthetic polymers. Because the success of a MALDI-MS analysis critically depends on a proper matrix and cation selection, which in turn relates closely to the polymer chemical nature and size, prior estimation of the polymer size range strongly helps in rationalizing MALDI sample preparation. We recently showed how pulsed gradient spin echo (PGSE) nuclear magnetic resonance could be used as an advantageous alternative to size exclusion chromatography, to rationalize MALDI sample preparation and confidently interpret MALDI mass spectra for homopolymers. Our aim here is to extend this methodology to the demanding case of amphiphilic block copolymers, for which obtaining prior estimates on the Mw values appears as an even more stringent prerequisite. Specifically, by studying poly(ethylene oxide) polystyrene block copolymers of distinct molecular weights and relative block weight fractions, we show how PGSE data can be used to derive the block Mw values. In contrast to homopolymers, such determination requires not only properly recorded calibration curves for each of the polymers constituting the block copolymers but also an appropriate hydrodynamic model to correctly interpret the diffusion data.

  5. Aqueous Self-Assembly of Y-Shaped Amphiphilic Block Copolymers into Giant Vesicles.

    PubMed

    Li, Hanping; Jin, Yong; Fan, Baozhu; Lai, Shuangquan; Sun, Xiaopeng; Qi, Rui

    2017-02-06

    The preparation and aqueous self-assembly of newly Y-shaped amphiphilic block polyurethane (PUG) copolymers are reported here. These amphiphilic copolymers, designed to have two hydrophilic poly(ethylene oxide) (PEO) tails and one hydrophobic alkyl tail via a two-step coupling reaction, can self-assemble into giant unilamellar vesicles (GUVs) (diameter ≥ 1000 nm) with a direct dissolution method in aqueous solution, depending on their Y-shaped structures and initial concentrations. More interesting, the copolymers can self-assemble into various distinct nano-/microstructures, such as spherical micelles, small vesicles, and GUVs, with the increase of their concentrations. The traditional preparation methods of GUVs generally need conventional amphiphilic molecules and additional complicated conditions, such as alternating electrical field, buffer solution, or organic solvent. Therefore, the self-assembly of Y-shaped PUGs with a direct dissolution method in aqueous solution demonstrated in this study supplies a new clue to fabricate GUVs based on the geometric design of amphiphilic polymers.

  6. Block copolymer self-assembly fundamentals and applications in formulation of nano-structured fluids

    NASA Astrophysics Data System (ADS)

    Sarkar, Biswajit

    Dispersions of nanoparticles in polymer matrices form hybrid materials that can exhibit superior structural and functional properties and find applications in e.g. thermo-plastics, electronics, polymer electrolytes, catalysis, paint formulations, and drug delivery. Control over the particle location and orientation in the polymeric matrices are essential in order to realize the enhanced mechanical, electrical, and optical properties of the nanohybrids. Block copolymers, composed of two or more different monomers, are promising for controlling particle location and orientation because of their ability to organize into ordered nanostructures. Fundamental questions pertaining to nanoparticle-polymer interfacial interactions remain open and formulate the objectives of our investigation. Particle-polymer enthalpic and entropic interactions control the nanoparticle dispersion in polymer matrices. Synthetic chemical methods for modifying the particle surface in order to control polymer-particle interactions are involved and large scale production is not possible. In the current approach, a physical method is employed to control polymer-particle interactions. The use of commercially available solvents is found to be effective in modifying particle-polymer interfacial interactions. The approach is applicable to a wide range of particle-polymer systems and can thereby enable large scale processing of polymer nanohybrids. The systems of silica nanoparticles dispersed in long-range or short-range self-assembled structures of aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Pluronics) is considered here. The effect of various parameters such as the presence of organic solvents, pH, and particle size on the block copolymer organization and the ensuing particle-polymer interactions are investigated. Favorable surface interactions between the deprotonated silica nanoparticle and PEO-rich domain facilitate particle

  7. Heat capacity anomaly in a self-aggregating system: Triblock copolymer 17R4 in water

    NASA Astrophysics Data System (ADS)

    Dumancas, Lorenzo V.; Simpson, David E.; Jacobs, D. T.

    2015-05-01

    The reverse Pluronic, triblock copolymer 17R4 is formed from poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO): PPO14 - PEO24 - PPO14, where the number of monomers in each block is denoted by the subscripts. In water, 17R4 has a micellization line marking the transition from a unimer network to self-aggregated spherical micelles which is quite near a cloud point curve above which the system separates into copolymer-rich and copolymer-poor liquid phases. The phase separation has an Ising-like, lower consolute critical point with a well-determined critical temperature and composition. We have measured the heat capacity as a function of temperature using an adiabatic calorimeter for three compositions: (1) the critical composition where the anomaly at the critical point is analyzed, (2) a composition much less than the critical composition with a much smaller spike when the cloud point curve is crossed, and (3) a composition near where the micellization line intersects the cloud point curve that only shows micellization. For the critical composition, the heat capacity anomaly very near the critical point is observed for the first time in a Pluronic/water system and is described well as a second-order phase transition resulting from the copolymer-water interaction. For all compositions, the onset of micellization is clear, but the formation of micelles occurs over a broad range of temperatures and never becomes complete because micelles form differently in each phase above the cloud point curve. The integrated heat capacity gives an enthalpy that is smaller than the standard state enthalpy of micellization given by a van't Hoff plot, a typical result for Pluronic systems.

  8. Polyethylene Glycol 3350

    MedlinePlus

    Polyethylene glycol 3350 is used to treat occasional constipation. Polyethylene glycol 3350 is in a class of medications ... Polyethylene glycol 3350 comes as a powder to be mixed with a liquid and taken by mouth. ...

  9. Molecular modeling of micelle formation and solubilization in block copolymer micelles. 2. Lattice theory for monomers with internal degrees of freedom

    SciTech Connect

    Hurter, P.N.; Hatton, T.A. . Dept. of Chemical Engineering); Scheutjens, J.M.H.M. )

    1993-09-13

    A self-consistent mean-field lattice theory of the micellization and solubilization properties of poly(ethylene oxide)-poly(propylene oxide) block copolymers is described. The polymer segments are allowed to assume both polar and nonpolar conformations (corresponding to the gauche and trans rotations of the C-C and C-O bonds), which permits the dependence of the segment-segment interactions on temperature and composition to be accounted for in a physically realistic manner. The phase diagrams of poly(ethylene oxide) and poly(propylene oxide) in water, both of which exhibit lower critical solution temperatures, can be reproduced semiquantitatively. The predictions of the theory compare favorably with published light scattering results on the aggregation behavior of block copolymers and with the authors experimental results for the solubilization of naphthalene in these micelles as a function of polymer composition and molecular weight. The dependence of the micelle-water partition coefficient on polymer composition is not simply related to the proportion of the hydrophobic constituent but depends on the detailed micelle structure. The strong effect of the molecular weight and PPO content of the polymer on the amount of naphthalene solubilized observed experimentally was interpreted in terms of the model results.

  10. Polyhomologation based on in situ generated boron-thexyl-silaboracyclic initiating sites: a novel strategy towards the synthesis of polyethylene-based complex architectures.

    PubMed

    Zhang, Zhen; Zhang, Hefeng; Gnanou, Yves; Hadjichristidis, Nikos

    2015-06-21

    A novel strategy, based on the in situ generated boron-thexyl-silaboracyclic initiating sites for the polyhomologation of dimethylsulfoxonium methylide, has been developed for the synthesis of complex polyethylene-based architectures. As examples, the synthesis of a 4-arm polyethylene star, three (polystyrene)(polyethylene)2 3-miktoarm stars and a PE-branched double graft copolymer is given.

  11. Reduced graphene oxide composites with water soluble copolymers having tailored lower critical solution temperatures and unique tube-like structure

    PubMed Central

    Namvari, Mina; Biswas, Chandra S.; Galluzzi, Massimiliano; Wang, Qiao; Du, Bing; Stadler, Florian J.

    2017-01-01

    Nanohybrids of graphene with water soluble polymer were synthesized using ‘grafting from’ method. GO, prepared by modified Hummers’ method, was first reacted with sodium azide. Alkyne-terminated RAFT-CTA was synthesized by reaction of propargyl alcohol and S-1-dodecyl-S’-(α,α‘-dimethyl-α”-acetic acid) trithiocarbonate. RAFT-CTA was grafted onto the GO sheets by facile click-reaction and subsequently, N-isopropylacrylamide (NIPAM) and N-ethyleacrylamide (NEAM) were polymerized on graphene sheets via RAFT polymerization method. The respective copolymers with different ratios were also prepared. The nanohybrids were characterized by FTIR, XRD, TGA, Raman, SEM, and AFM. Both SEM and AFM clearly showed rod-like structures for rGO-PNEAM. XRD showed a small peak at 2θ = 19.21°, corresponding to d-spacing ≈ 4.6 Å. In addition, the nanohybrids showed a very broad temperature range for the LCST in water between ca. 30 and 70 °C. PMID:28291225

  12. Reduced graphene oxide composites with water soluble copolymers having tailored lower critical solution temperatures and unique tube-like structure

    NASA Astrophysics Data System (ADS)

    Namvari, Mina; Biswas, Chandra S.; Galluzzi, Massimiliano; Wang, Qiao; Du, Bing; Stadler, Florian J.

    2017-03-01

    Nanohybrids of graphene with water soluble polymer were synthesized using ‘grafting from’ method. GO, prepared by modified Hummers’ method, was first reacted with sodium azide. Alkyne-terminated RAFT-CTA was synthesized by reaction of propargyl alcohol and S-1-dodecyl-S’-(α,α‘-dimethyl-α”-acetic acid) trithiocarbonate. RAFT-CTA was grafted onto the GO sheets by facile click-reaction and subsequently, N-isopropylacrylamide (NIPAM) and N-ethyleacrylamide (NEAM) were polymerized on graphene sheets via RAFT polymerization method. The respective copolymers with different ratios were also prepared. The nanohybrids were characterized by FTIR, XRD, TGA, Raman, SEM, and AFM. Both SEM and AFM clearly showed rod-like structures for rGO-PNEAM. XRD showed a small peak at 2θ = 19.21°, corresponding to d-spacing ≈ 4.6 Å. In addition, the nanohybrids showed a very broad temperature range for the LCST in water between ca. 30 and 70 °C.

  13. Reduced graphene oxide composites with water soluble copolymers having tailored lower critical solution temperatures and unique tube-like structure.

    PubMed

    Namvari, Mina; Biswas, Chandra S; Galluzzi, Massimiliano; Wang, Qiao; Du, Bing; Stadler, Florian J

    2017-03-14

    Nanohybrids of graphene with water soluble polymer were synthesized using 'grafting from' method. GO, prepared by modified Hummers' method, was first reacted with sodium azide. Alkyne-terminated RAFT-CTA was synthesized by reaction of propargyl alcohol and S-1-dodecyl-S'-(α,α'-dimethyl-α"-acetic acid) trithiocarbonate. RAFT-CTA was grafted onto the GO sheets by facile click-reaction and subsequently, N-isopropylacrylamide (NIPAM) and N-ethyleacrylamide (NEAM) were polymerized on graphene sheets via RAFT polymerization method. The respective copolymers with different ratios were also prepared. The nanohybrids were characterized by FTIR, XRD, TGA, Raman, SEM, and AFM. Both SEM and AFM clearly showed rod-like structures for rGO-PNEAM. XRD showed a small peak at 2θ = 19.21°, corresponding to d-spacing ≈ 4.6 Å. In addition, the nanohybrids showed a very broad temperature range for the LCST in water between ca. 30 and 70 °C.

  14. Polyether-polyester graft copolymer

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L. (Inventor)

    1987-01-01

    Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

  15. Dextran and polymer polyethylene glycol (PEG) coating reduce both 5 and 30 nm iron oxide nanoparticle cytotoxicity in 2D and 3D cell culture.

    PubMed

    Yu, Miao; Huang, Shaohui; Yu, Kevin Jun; Clyne, Alisa Morss

    2012-01-01

    Superparamagnetic iron oxide nanoparticles are widely used in biomedical applications, yet questions remain regarding the effect of nanoparticle size and coating on nanoparticle cytotoxicity. In this study, porcine aortic endothelial cells were exposed to 5 and 30 nm diameter iron oxide nanoparticles coated with either the polysaccharide, dextran, or the polymer polyethylene glycol (PEG). Nanoparticle uptake, cytotoxicity, reactive oxygen species (ROS) formation, and cell morphology changes were measured. Endothelial cells took up nanoparticles of all sizes and coatings in a dose dependent manner, and intracellular nanoparticles remained clustered in cytoplasmic vacuoles. Bare nanoparticles in both sizes induced a more than 6 fold increase in cell death at the highest concentration (0.5 mg/mL) and led to significant cell elongation, whereas cell viability and morphology remained constant with coated nanoparticles. While bare 30 nm nanoparticles induced significant ROS formation, neither 5 nm nanoparticles (bare or coated) nor 30 nm coated nanoparticles changed ROS levels. Furthermore, nanoparticles were more toxic at lower concentrations when cells were cultured within 3D gels. These results indicate that both dextran and PEG coatings reduce nanoparticle cytotoxicity, however different mechanisms may be important for different size nanoparticles.

  16. Flash NanoPrecipitation of organic actives via confined micromixing and block copolymer stabilization

    NASA Astrophysics Data System (ADS)

    Johnson, Brian K.

    This dissertation provides a method and the understanding required to produce nanoparticles of organic actives using Flash NanoPrecipitation . The process comprises mixing a solvent phase containing molecularly dissolved amphiphilic block copolymer and an organic active with an anti-solvent. One block of the copolymer precipitates to alter the nucleation and growth of the organic active while the other remains in solution for particle stabilization. A custom built confined impinging jets (CIJ) mixer provides optimum micromixing at the laboratory or full scale within milliseconds. Comparison to other reactor designs is provided. The resulting nanoparticles have functional surfaces tailored to meet the needs of pharmaceutical or specialty chemical formulations. Example beta-carotene nanoparticles with a polyethylene oxide surface are produced at high concentration, high yield, low stabilizer content, and a size suitable for sterile filtration or larger. The technical challenges in nanoparticle production are explained via the characteristic times for mixing, copolymer aggregation, and organic active particle formation. The time for Flash NanoPrecipitation is shown to depend strongly on the time for copolymer aggregation, and control of the organic nucleation versus growth is critical to achieve nanoparticles. Mixing operating lines explain the impact of solubility differences between the colloidal stabilizer and the organic active as function of mixing rate. Techniques to measure the solubility of the copolymer and DeltaG° , DeltaH°, and DeltaS° of micellization are demonstrated. An analytical CIJ mixer is developed by quantifying the characteristic time and physical mechanism of mixing. The methodology described to find an absolute mixing lifetime is also applied to a vortex mixer at a spectrum of flow ratios away from one. Dimensional analysis using the process Damkohler number, defined as the ratio of the mixing to the process time, is applied to precipitation

  17. Equilibrium structure of a triblock copolymer system revealed by mesoscale simulation and neutron scattering

    NASA Astrophysics Data System (ADS)

    Do, Changwoo; Chen, Wei-Ren; Hong, Kunlun; Smith, Gregory S.

    2013-12-01

    We have performed both mesoscale simulations and neutron scattering experiments on Pluronic L62, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer system in aqueous solution. The influence of simulation variables such PEO/PPO block ratio, interaction parameters, and coarse-graining methods is extensively investigated by covering all permutations of parameters found in the literatures. Upon increasing the polymer weight fraction from 50 wt% to 90 wt%, the equilibrium structure of the isotropic, reverse micellar, bicontinuous, worm-like micelle network, and lamellar phases are respectively predicted from the simulation depending on the choices of simulation parameters. Small angle neutron scattering (SANS) measurements show that the same polymer systems exhibit the spherical micellar, lamellar, and reverse micellar phases with the increase of the copolymer concentration at room temperature. Detailed structural analysis and comparison with simulations suggest that one of the simulation parameter sets can provide reasonable agreement with the experimentally observed structures.

  18. Equilibrium Structure of a Triblock Copolymer System Revealed by Mesoscale Simulation and Neutron Scattering

    SciTech Connect

    Do, Changwoo; Chen, Wei-Ren; Hong, Kunlun; Smith, Gregory Scott

    2013-01-01

    We have performed both mesoscale simulations and neutron scattering experiments on Pluronic L62, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer system in aqueous solution. The influence of simulation variables such PEO/PPO block ratio, interaction parameters, and coarse-graining methods is extensively investigated by covering all permutations of parameters found in the literatures. Upon increasing the polymer weight fraction from 50 wt% to 90 wt%, the equilibrium structure of the isotropic, reverse micellar, bicontinuous, worm-like micelle network, and lamellar phases are respectively predicted from the simulation depending on the choices of simulation parameters. Small angle neutron scattering (SANS) measurements show that the same polymer systems exhibit the spherical micellar, lamellar, and reverse micellar phases with the increase of the copolymer concentration at room temperature. Detailed structural analysis and comparison with simulations suggest that one of the simulation parameter sets can provide reasonable agreement with the experimentally observed structures.

  19. Nanostructured Copolymer Gels for dsDNA Separation by Capillary Electrophoresis

    PubMed Central

    Wan, Fen; Zhang, Jun; Lau, Angela; Tan, Sarah; Burger, Christian; Chu, Benjamin

    2010-01-01

    Pluronics copolymers are triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) and are able to form many different ordered nanostructures at appropriate polymer concentrations and temperatures in selective solvents. These nano-structured ‘gels’ showed desirable criteria when used as DNA separation media, especially in microchip electrophoresis, including dynamic coating ability and viscosity switchable property. A ternary system of F127 (E99P69E99)/TBE buffer/1-butanol was selected as a model system to test the sieving performance of different nanostructures in separating dsDNA by capillary electrophoresis. The lattice structures were determined by small-angle x-ray scattering with quasi-lattice crystal parameters being calculated according to the x-ray scattering data. Viscosity measurements showed the sol-gel transition phenomena. In addition to the cubic structure, successful electrophoretic separation of dsDNA in 2-D hexagonal packed cylinders was achieved. Results showed that without further optimization, ΦX174 DNA-Hae III digest was well separated within 15 minutes in a 7-cm separation channel, by using F127/TBE/1-butanol gel with a 2-D hexagonal structure. A mechanism for DNA separations by those gels with both hydrophilic and hydrophobic domains is discussed. PMID:19053068

  20. Kinetics and microscopic processes of long-term fracture in polyethylene-piping materials. Annual report, February 1, 1989-February 1, 1990

    SciTech Connect

    Brown, N.; Lu, X.

    1990-05-10

    Contents: notchology--the effect of the notching method on the slow crack growth failure in tough polyethylene; the effect of molecular weight on the fatigue behavior of high density polyethylene; the transition from ductile to slow crack growth failure in a copolymer of polyethylene; the ductile-brittle transition in a polyethylene copolymer; a unification of ductile failure and slow crack growth in an ethylene-octene copolymer; the dependence of butyl branch density on slow crack growth in polyethylene-kinetics; slow crack growth under fatigue and constant stress for ethylene-hexene resins with different density of branches; correlation of the fatigue test and the constant load slow crack growth test; relationship between slow crack growth and morphological change in ethylene-hexene copolymers; morphological changes on annealing in hdpe and mdpe and their effect on slow crack growth; ranking of pe gas pipe resins in air and igepal; brittle fracture of pe at low temperature; butt fusion welding.

  1. PEGylation affects cytotoxicity and cell-compatibility of poly(ethylene imine) for lung application: Structure-function relationships

    SciTech Connect

    Beyerle, Andrea; Merkel, Olivia; Stoeger, Tobias; Kissel, Thomas

    2010-01-15

    Poly(ethylene imine) (PEI) has widely been used as non-viral gene carrier due to its capability to form stable complexes by electrostatic interactions with nucleic acids. To reduce cytotoxicity of PEI, several studies have addressed modified PEIs such as block or graft copolymers containing cationic and hydrophilic non-ionic components. Copolymers of PEI and hydrophilic poly(ethylene glycol) (PEG) with various molecular weights and graft densities were shown to exhibit decreased cytotoxicity and potential for DNA and siRNA delivery. In this study, we evaluated the cytotoxicity and cell-compatibility of different PEGylated PEI polymers in two murine lung cell lines. We found that the degree of PEGylation correlated with both cytotoxicity and oxidative stress, but not with proinflammatory effects. AB type copolymers with long PEG blocks caused high membrane damage and significantly decreased the metabolic activity of lung cells. In addition, they significantly increased the release of two lipid mediators such as 8-isoprostanes (8-IP) and prostaglandin E{sub 2} (PGE{sub 2}) in a dose-dependent manner. In contrast, the cytokine profiles which indicated high levels of acute-phase cytokines such as TNF-alpha, IL-6, and G-CSF did not follow any clear structure-function relationship. In conclusion, we found that modification of PEI 25kDa with high degree of PEGylation and low PEG chain length reduced cytotoxic and oxidative stress response in lung cells, while the proinflammatory potential remained unaffected. A degree of substitution in the range of 10 to 30 and PEG-chain lengths up to 2000 Da seem to be beneficial and merit further investigations.

  2. Processing, Characterization and Fretting Wear of Zinc Oxide and Silver Nanoparticles Reinforced Ultra High Molecular Weight Polyethylene Biopolymer Nanocomposite

    NASA Astrophysics Data System (ADS)

    Alam, Fahad; Kumar, Anil; Patel, Anup Kumar; Sharma, Rajeev K.; Balani, Kantesh

    2015-04-01

    Ultra-high molecular weight polyethylene (UHMWPE) is the most widely used biopolymer for articulating surfaces, such as an acetabular cup liner interfacing with a metal/ceramic femoral head. However, the formation of wear debris leads to the aseptic loosening of implants. Thus, in order to improve the life span via enhancing the fretting wear resistance, UHMWPE is reinforced with ZnO/Ag nanoparticles. It is envisaged that the ZnO/Ag addition will also exhibit antibacterial properties. In the current study, the synergetic effect of the reinforcement of ZnO/Ag nanoparticles (0-3 wt.% combinations) on the fretting wear behavior of a UHMWPE matrix is assessed. The phase characterization of compression- molded UHMWPE-Ag-ZnO biopolymer nanocomposites has elicited the retention of starting phases. All samples were processed at >98% density using compression molding. Silver and ZnO reinforcement showed enhanced hardness ~20.4% for U3A and 42.0% for U3Z. Fretting wear performance was evaluated at varying loads (5-15 N), keeping in mind the weight at different joints, with constant frequency (5 Hz) as well as amplitude of oscillation (100 µm). Laser surface profilometry showed change of wear volume from 8.6 × 10-5 mm3 for neat polymer to 5.8 × 10-5 mm3 with 1 wt.% Ag + 1 wt.% ZnO reinforcement (at 15 N load). Consequently, the mechanics of resistance offered by Ag and ZnO is delineated in the UHMWPE matrix. Further, S. aureus viability reduction is ~28.7% in cases with 1 wt.% Ag addition, ~42.5% with 1 wt.% ZnO addition, but synergistically increase to ~58.6% and 47.1% when each of Ag and ZnO is added with 1 wt.% and 3 wt.%, respectively (when compared to that of the UHMWPE control sample). Increased wear resistance and superior bioactivity and enhanced anti-bacterial properties of 1 wt.% Ag + 1 wt.% ZnO and 3 wt.% Ag + 3 wt.% ZnO shows the potential use of ZnO-Ag-UHMWPE biopolymer composites as an articulating surface.

  3. Phase separations in a copolymer copolymer mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Jun; Jin, Guojun; Ma, Yuqiang

    2006-01-01

    We propose a three-order-parameter model to study the phase separations in a diblock copolymer-diblock copolymer mixture. The cell dynamical simulations provide rich information about the phase evolution and structural formation, especially the appearance of onion-rings. The parametric dependence and physical reason for the domain growth of onion-rings are discussed.

  4. A new method to analyze copolymer based superplasticizer traces in cement leachates.

    PubMed

    Guérandel, Cyril; Vernex-Loset, Lionel; Krier, Gabriel; De Lanève, Michel; Guillot, Xavier; Pierre, Christian; Muller, Jean François

    2011-03-15

    Enhancing the flowing properties of fresh concrete is a crucial step for cement based materials users. This is done by adding polymeric admixtures. Such additives have enabled to improve final mechanicals properties and the development of new materials like high performance or self compacting concrete. Like this, the superplasticizers are used in almost cement based materials, in particular for concrete structures that can have a potential interaction with drinking water. It is then essential to have suitable detection techniques to assess whether these organic compounds are dissolved in water after a leaching process or not. The main constituent of the last generation superplasticizer is a PolyCarboxylate-Ester copolymer (PCE), in addition this organic admixture contains polyethylene oxide (free PEO) which constitutes a synthesis residue. Numerous analytical methods are available to characterize superplasticizer content. Although these techniques work well, they do not bring suitable detection threshold to analyze superplasticizer traces in solution with high mineral content such as leachates of hardened cement based materials formulated with superplasticizers. Moreover those techniques do not enable to distinguish free PEO from PCE in the superplasticizer. Here we discuss two highly sensitive analytical methods based on mass spectrometry suitable to perform a rapid detection of superplasticizer compounds traces in CEM I cement paste leachates: MALDI-TOF mass spectrometry, is used to determine the free PEO content in the leachate. However, industrial copolymers (such as PCE) are characterized by high molecular weight and polymolecular index. These two parameters lead to limitation concerning analysis of copolymers by MALDI-TOFMS. In this study, we demonstrate how pyrolysis and a Thermally assisted Hydrolysis/Methylation coupled with a triple-quadrupole mass spectrometer, provides good results for the detection of PCE copolymer traces in CEM I cement paste

  5. β-NMR measurements of lithium ion transport in thin films of pure and lithium-salt-doped poly(ethylene oxide).

    PubMed

    McKenzie, Iain; Harada, Masashi; Kiefl, Robert F; Levy, C D Philip; MacFarlane, W Andrew; Morris, Gerald D; Ogata, Shin-Ichi; Pearson, Matthew R; Sugiyama, Jun

    2014-06-04

    β-Detected nuclear spin relaxation of (8)Li(+) has been used to study the microscopic diffusion of lithium ions in thin films of poly(ethylene oxide) (PEO), where the implanted lithium ions are present in extremely low concentration, and PEO with 30 wt % LiCF3SO3 over a wide range of temperatures both above and below the glass transition temperature. Recent measurements by Do et al. [Phys. Rev. Lett. 2013, 111, 018301] found that the temperature dependence of the Li(+) conductivity was identical to that of the dielectric α relaxation and was well described by the Vogel-Fulcher-Tammann relation, implying the α relaxation dominates the Li(+) transport process. In contrast, we find the hopping of Li(+) in both samples in the high temperature viscoelastic phase follows an Arrhenius law and depends significantly on the salt content. We propose that the hopping of Li(+) between cages involves motion of the polymer but that it is only for long-range diffusion where the α relaxation plays an important role.

  6. Presentation of a novel model of chitosan- polyethylene oxide-nanohydroxyapatite nanofibers together with bone marrow stromal cells to repair and improve minor bone defects

    PubMed Central

    Emamgholi, Asgar; Rahimi, Mohsen; Kaka, Gholamreza; Sadraie, Seyed Homayoon; Najafi, Saleh

    2015-01-01

    Objective(s): Various methods for repairing bone defects are presented. Cell therapy is one of these methods. Bone marrow stromal cells (BMSCs) seem to be suitable for this purpose. On the other hand, lots of biomaterials are used to improve and repair the defect in the body, so in this study we tried to produce a similar structure to the bone by the chitosan and hydroxyapatite. Materials and Methods: In this study, the solution of chitosan-nanohydroxyapatite-polyethylene oxide (PEO) Nanofibers was produced by electrospinning method, and then the BMSCs were cultured on this solution. A piece of chitosan-nanohydroxyapatite Nanofibers with BMSCs was placed in a hole with the diameter of 1 mm at the distal epiphysis of the rat femur. Then the biomechanical and radiographic studies were performed. Results: Biomechanical testing results showed that bone strength was significantly higher in the Nanofiber/BMSCs group in comparison with control group. Also the bone strength in nanofiber/BMSCs group was significant, but in nanofiber group was nearly significant. Radiographic studies also showed that the average amount of callus formation (radio opacity) in nanofiber and control group was not significantly different. The callus formation in nanofiber/BMSCs group was increased compared to the control group, and it was not significant in the nanofiber group. Conclusion: Since chitosan-nanohydroxyapatite nanofibers with BMSCs increases the rate of bone repair, the obtained cell-nanoscaffold shell can be used in tissue engineering and cell therapy, especially for bone defects. PMID:26523221

  7. A novel chitosan-polyethylene oxide nanofibrous mat designed for controlled co-release of hydrocortisone and imipenem/cilastatin drugs.

    PubMed

    Fazli, Yousef; Shariatinia, Zahra; Kohsari, Iraj; Azadmehr, Amirreza; Pourmortazavi, Seied Mahdi

    2016-11-20

    Antimicrobial chitosan-polyethylene oxide (CS-PEO) nanofibrous mats containing ZnO nanoparticles (NPs) and hydrocortisone-imipenem/cilastatin-loaded ZnO NPs were produced by electrospinning technique. The FE-SEM images displayed that the spherical ZnO NPs were ∼70-200nm in size and the CS-PEO nanofibers were very uniform and free of any beads which had average diameters within the range of ∼20-130nm. For all of the nanofibrous mats, the water uptakes were the highest in acidic medium but they were decreased in the buffer and the least swellings were obtained in the alkaline environment. The drug incorporated mat preserved its bactericidal activity even after it was utilized in the release experiment for 8days in the PBS buffer. The hydrocortisone release was increased to 82% within first 12h while the release rate of imipenem/cilastatin was very much slower so that 20% of the drug was released during this period of time suggesting this nanofibrous mat is very suitable to inhibit inflammation (by hydrocortisone) and infection (using imipenem/cilastatin antibiotic and ZnO NPs) principally for the wound dressing purposes.

  8. Impedance study of the interface between lithium, polyaniline, lithium-doped MnO 2 and modified poly(ethylene oxide) electrolyte

    NASA Astrophysics Data System (ADS)

    Baochen, Wang; Li, Feng; Yongyao, Xia

    1993-03-01

    Impedance study was carried out for the interfaces between lithium, polyaniline (PAn), lithium-doped MnO 2 and modified poly(ethylene oxide) (PEO) electrolyte under various conditions. The interfacial charge-transfer resistance Rct on PEO/PAn, Rct on PEO/LiMn 2O 4 increase with depth-of-discharge and decrease after the charge of the cell containing modified PEO as electrolyte. The charge-transfer resistance Rct on PEO/PAn is higher than Rct on PEO/LiMn 2O 4 under the same condition, since inserted species and mechanism are different for both cases. In the case of PAn, an additional charge-transfer resistance might be related to the electronic conductivity change in discharge/charge potential range, as it was evident from a voltammetry curve. With increasing cycle numbers, the charge-transfer resistance increases gradually. The impedance results also have shown that at low frequency the diffusion control is dominant in the process of the charge and discharge of Li/PEO/PAn or Li/PEO/LiMn 2O 4 cell. The diffusion coefficients have been calculated from impedance data.

  9. Impedance study of the interfaces between lithium, polyaniline, lithium-doped MnO2 and modified poly(ethylene oxide) electrolyte

    NASA Astrophysics Data System (ADS)

    Wang, Baochen; Feng, Li; Xia, Yongyao

    1993-03-01

    Impedance study was carried out for the interfaces between lithium, polyaniline (PAn), lithium-doped MnO2 and modified poly(ethylene oxide) (PEO) electrolyte under various conditions. The interfacial charge-transfer resistances R(sub ct) on PEO/PAn, R(sub ct) on PEO/LiMn2O increas e with depth-of-discharge and decrease after the charge of the cell containing modified PEO as electrolyte. The charge-transfer resistance R(sub ct) on PEO/PAn is higher than R(sub ct) on PEO/LiMn2O4 under the same condition, since inserted species and mechanism are different for both cases. In the case of PAn, an additional charge-transfer resistance might be related to the electronic conductivity change in discharge/charge potential range, as it was evident from a voltammetry curve. With increasing cycle numbers, the charge-transfer resistance increases gradually. The impedance results also have shown that at low frequency the diffusion control is dominant in the process of the charge and discharge of Li/PEO/PAn or Li/PEO/LiMn2O4 cell. The diffusion coefficients have been calculated from impedance data.

  10. Enhanced Lithium Ion Transport in Poly(ethylene glycol) Diacrylate-Supported Solvate Ionogel Electrolytes via Chemically Cross-linked Ethylene Oxide Pathways.

    PubMed

    D'Angelo, Anthony J; Panzer, Matthew J

    2017-02-02

    Lithium-ion solvate ionic liquids (SILs), consisting of complexed Li(+) cations and a weakly basic anion, represent an emergent class of nonvolatile liquid electrolytes suitable for lithium-based electrochemical energy storage. In this report, solid-state, flexible solvate ionogel electrolytes are synthesized via UV-initiated free radical polymerization/cross-linking of poly(ethylene glycol) diacrylate (PEGDA) in situ within the [Li(G4)][TFSI] electrolyte, which is formed by an equimolar mixture of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and tetraglyme (G4). Ion diffusivity measurements reveal enhanced Li(+) diffusion in PEGDA-supported solvate ionogels, as compared to poly(methyl methacrylate)-supported gels that lack ethylene oxide chains. At 21 vol% PEGDA, a maximum Li(+) transport number of 0.58 and a room temperature ionic conductivity of 0.43 mS/cm have been achieved in a solvate ionogel electrolyte that exhibits an elastic modulus of 0.47 MPa. These results demonstrate the importance of polymer scaffold selection on solvate ionogel electrolyte performance for advanced lithium-based batteries.

  11. Nanoscale confinement effects on the relaxation dynamics in networks of diglycidyl ether of bisphenol-A and low-molecular-weight poly(ethylene oxide).

    PubMed

    Kalogeras, Ioannis M; Stathopoulos, Andreas; Vassilikou-Dova, Aglaia; Brostow, Witold

    2007-03-22

    Thermoplastic poly(ethylene oxide) (PEO) (Mw(PEO) approximately 4000) has been used to prepare thermosetting nanocomposites incorporating diglycidyl ether of bisphenol A (DGEBA) epoxy oligomer. Blends with various PEO/DGEBA weight ratios were cured using stoichiometric portions of 4,4'-diaminodiphenylmethane. The resulting semi-interpenetrating polymer networks were studied by several techniques. Nanoscale confinement effects, thermal (glass transition, melting and crystallization temperatures) and structural features of our materials are similar to those for networks with much higher Mw(PEO) and different curing agents; however, the polyether crystallization onset occurs in our case at a lower PEO concentration; shorter PEO chains organize themselves more easily into crystalline domains. Very low estimates of the k parameter of the Gordon-Taylor equation, used to fit the compositional dependences of the dielectric and calorimetric glass transition temperatures, and a strong plasticization of the motion of the glyceryl segments (beta-relaxation) in the epoxy resin were observed. These illustrate an intensified weakening in the strength of the intermolecular interactions in the modified networks, as compared to the high strength of the self-association of hydroxyls in the neat resin. The significance of hydrogen-bonding interactions between the components for obtaining structurally homogeneous thermoset-i-thermoplastic networks is discussed.

  12. Quantitative control of poly(ethylene oxide) surface antifouling and biodetection through azimuthally enhanced grating coupled-surface plasmon resonance sensing

    NASA Astrophysics Data System (ADS)

    Sonato, Agnese; Silvestri, Davide; Ruffato, Gianluca; Zacco, Gabriele; Romanato, Filippo; Morpurgo, Margherita

    2013-12-01

    Grating Coupled-Surface Plasmon reflectivity measurements carried out under azimuth and polarization control (GC-SPR φ ≠ 0°) were used to optimize the process of gold surface dressing with poly(ethylene oxide) (PEO) derivatives of different molecular weight, with the final goal to maximize the discrimination between specific and non-specific binding events occurring at the surface. The kinetics of surface deposition of thiol-ending PEOs (0.3, 2 and 5 kDa), introduced as antifouling layers, was monitored. Non-specific binding events upon immersion of the surfaces into buffers containing either 0.1% bovine serum albumin or 1% Goat Serum, were evaluated as a function of polymer size and density. A biorecognition event between avidin and biotin was then monitored in both buffers at selected low and high polymer surface densities and the contribution of analyte and fouling elements to the signal was precisely quantified. The 0.3 kDa PEO film was unable to protect the surface from non-specific interactions at any tested density. On the other hand, the 2 and 5 kDa polymers at their highest surface densities guaranteed full protection from non-specific interactions from both buffers. These densities were reached upon a long deposition time (24-30 h). The results pave the way toward the application of this platform for the detection of low concentration and small dimension analytes, for which both non-fouling and high instrumental sensitivity are fundamental requirements.

  13. β - NMR Measurements of Lithium Ion Transport in Thin Films of Pure and Lithium-Salt-Doped Poly(ethylene oxide)

    NASA Astrophysics Data System (ADS)

    McKenzie, Iain; Harada, Masashi; Cortie, David L.; Kiefl, Robert F.; Levy, C. D. Philip; Macfarlane, W. Andrew; McFadden, Ryan M. L.; Morris, Gerald D.; Ogata, Shin-Ichi; Pearson, Matthew R.; Sugiyama, Jun

    2015-03-01

    β - Detected nuclear spin relaxation of 8Li+ has been used to study the microscopic diffusion of lithium ions in thin films of poly(ethylene oxide) (PEO), PEO with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), PEO with lithium triflate (LiTf) and PEO with lithium trifluoroacetic acid (LiTFA) with monomer-to-salt ratios of 8.3:1. Hopping of Li + above ~ 250 K follows an Arrhenius law in all of the films. Diffusion of Li+ is fastest in pure PEO and decreases in order LiTFSI >LiTf >LiTFA. We observed the activation energy for hopping (EA) and the intrinsic hop rate (τ0-1) both increasing in order LiTFA

  14. Chemical modification of wheat protein-based natural polymers: grafting and cross-linking reactions with poly(ethylene oxide) diglycidyl ether and ethyl diamine.

    PubMed

    Kurniawan, Lusiana; Qiao, Greg G; Zhang, Xiaoqing

    2007-09-01

    Mobile poly(ethylene oxide) diglycidyl ether (PEODGE) segments were chemically grafted onto a soluble wheat protein (WP), and different network structures were formed via coupling reactions with ethyl diamine (EDA) in different PEODGE/EDA (PE) ratios. When the PE ratio was 1:1, linear PEs were the predominant segments grafted onto WP chains and the whole WP-PEODGE-EDA (WPE) system was still soluble with an increased molecular weight. Reducing the amount of EDA in the systems produced insoluble cross-linked WPE networks. The broad distribution of network structures and chain mobility resulted in a broad glass transition for the WPE materials. However, the glass transition started at lower temperatures, and the materials became flexible at room temperature. The PE segments were present in all rigid, intermediate, and mobile phases in WPE networks, while the proportion of mobile WP chains was increased as a result of the plasticization effect from the mobile PE segments. The mobility of the most mobile component lipid was also restricted to some extent when forming the cross-linked WPE networks. The study demonstrated that the formation of different network structures with PE segments could significantly improve the flexibility of WP materials, vary the solubility, and modify the mechanical performance of WP-based natural polymer materials.

  15. Conformational sensitivity of conjugated poly(ethylene oxide)-poly(amidoamine) molecules to cations adducted upon electrospray ionization - a mass spectrometry, ion mobility and molecular modeling study.

    PubMed

    Tintaru, Aura; Chendo, Christophe; Wang, Qi; Viel, Stéphane; Quéléver, Gilles; Peng, Ling; Posocco, Paola; Pricl, Sabrina; Charles, Laurence

    2014-01-15

    Tandem mass spectrometry and ion mobility spectrometry experiments were performed on multiply charged molecules formed upon conjugation of a poly(amidoamine) (PAMAM) dendrimer with a poly(ethylene oxide) (PEO) linear polymer to evidence any conformational modification as a function of their charge state (2+ to 4+) and of the adducted cation (H(+)vs Li(+)). Experimental findings were rationalized by molecular dynamics simulations. The G0 PAMAM head-group could accommodate up to three protons, with protonated terminal amine group enclosed in a pseudo 18-crown-6 ring formed by the PEO segment. This particular conformation enabled a hydrogen bond network which allowed long-range proton transfer to occur during collisionally activated dissociation. In contrast, lithium adduction was found to mainly occur onto oxygen atoms of the polyether, each Li(+) cation being coordinated by a 12-crown-4 pseudo structure. As a result, for the studied polymeric segment (Mn=1500gmol(-1)), PEO-PAMAM hybrid molecules exhibited a more expanded shape when adducted to lithium as compared to proton.

  16. Conformational and Dynamic Properties of Poly(ethylene oxide) in an Ionic Liquid: Development and Implementation of a First-Principles Force Field.

    PubMed

    McDaniel, Jesse G; Choi, Eunsong; Son, Chang-Yun; Schmidt, J R; Yethiraj, Arun

    2016-01-14

    The conformational properties of polymers in ionic liquids are of fundamental interest but not well understood. Atomistic and coarse-grained molecular models predict qualitatively different results for the scaling of chain size with molecular weight, and experiments on dilute solutions are not available. In this work, we develop a first-principles force field for poly(ethylene oxide) (PEO) in the ionic liquid 1-butyl 3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) using symmetry adapted perturbation theory (SAPT). At temperatures above 400 K, simulations employing both the SAPT and OPLS-AA force fields predict that PEO displays ideal chain behavior, in contrast to previous simulations at lower temperature. We therefore argue that the system shows a transition from extended to more compact configurations as the temperature is increased from room temperature to the experimental lower critical solution temperature. Although polarization is shown to be important, its implicit inclusion in the OPLS-AA force is sufficient to describe the structure and energetics of the mixture. The simulations emphasize the difference between ionic liquids from typical solvents for polymers.

  17. On-line sample preconcentration by sweeping and poly(ethylene oxide)-mediated stacking for simultaneous analysis of nine pairs of amino acid enantiomers in capillary electrophoresis.

    PubMed

    Lin, En-Ping; Lin, Kai-Cheng; Chang, Chia-Wei; Hsieh, Ming-Mu

    2013-09-30

    This study proposes a sensitive method for the simultaneous separation and concentration of 9 pairs of amino acid enantiomers by combining poly(ethylene oxide) (PEO)-based stacking, β-cyclodextrin (β-CD)-mediated micellar electrokinetic chromatography (MEKC), and 9-fluoroenylmethyl chloroformate (FMOC) derivatization. The 9 pairs of FMOC-derivatized amino acid enantiomers were baseline separated using a discontinuous system, and the buffer vials contained a solution of 150 mM Tris-borate (TB), 12.5% (v/v) isopropanol (IPA), 0.5% (w/v) PEO, 35 mM sodium taurodeoxycholate (STDC), and 35 mM β-CD, and the capillary was filled with a solution of 1.5 M TB, 12.5% (v/v) IPA, 35 mM STDC, and 35 mM β-CD. Based on the difference in viscosity between the sample zone and PEO solution and because of the STDC sweeping, the discontinuous system effectively stacked 670 nL of the 9 pairs of FMOC-derivatized amino acid enantiomers without losing chiral resolution. Consequently, the limits of detection for the 9 pairs of FMOC-derivatized amino acid enantiomers were reduced to 40-60 nM. This method was successfully used to determine d-Tryptophan (Trp), l-Trp, d-Phenylalanine (Phe), l-Phe, d-Glutamic acid (Glu), and l-Glu in various types of beers.

  18. A new solid polymer electrolyte incorporating Li10GeP2S12 into a polyethylene oxide matrix for all-solid-state lithium batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Yanran; Wu, Chuan; Peng, Gang; Chen, Xiaotian; Yao, Xiayin; Bai, Ying; Wu, Feng; Chen, Shaojie; Xu, Xiaoxiong

    2016-01-01

    Li10GeP2S12 (LGPS) is incorporated into polyethylene oxide (PEO) matrix to fabricate composite solid polymer electrolyte (SPE) membranes. The lithium ion conductivities of as-prepared composite membranes are evaluated, and the optimal composite membrane exhibits a maximum ionic conductivity of 1.21 × 10-3 S cm-1 at 80 °C and an electrochemical window of 0-5.7 V. The phase transition behaviors for electrolytes are characterized by DSC, and the possible reasons for their enhanced ionic conductivities are discussed. The LGPS microparticles, acting as active fillers incorporation into the PEO matrix, have a positive effect on the ionic conductivity, lithium ion transference number and electrochemical stabilities. In addition, two kinds of all-solid-state lithium batteries (LiFeO4/SPE/Li and LiCoO2/SPE/Li) are fabricated to demonstrate the good compatibility between this new SPE membrane and different electrodes. And the LiFePO4/Li battery exhibits fascinating electrochemical performance with high capacity retention (92.5% after 50 cycles at 60 °C) and attractive capacities of 158, 148, 138 and 99 mAh g-1 at current rates of 0.1 C, 0.2 C, 0.5 C and 1 C at 60 °C, respectively. It is demonstrated that this new composite SPE should be a promising electrolyte applied in solid state batteries based on lithium metal electrode.

  19. Formulation and in vitro evaluation of floating tablets of hydroxypropyl methylcellulose and polyethylene oxide using ranitidine hydrochloride as a model drug

    PubMed Central

    Gharti, KP; Thapa, P; Budhathoki, U; Bhargava, A

    2012-01-01

    The present study was carried out with an objective of preparation and in vitro evaluation of floating tablets of hydroxypropyl methyl cellulose (HPMC) and polyethylene oxide (PEO) using ranitidine hydrochloride as a model drug. The floating tablets were based on effervescent approach using sodium bicarbonate a gas generating agent. The tablets were prepared by dry granulation method. The effect of polymers concentration and viscosity grades of HPMC on drug release profile was evaluated. The effect of sodium bicarbonate and stearic acid on drug release profile and floating properties were also investigated. The result of in vitro dissolution study showed that the drug release profile could be sustained by increasing the concentration of HPMC K15MCR and Polyox WSR303. The formulation containing HPMC K15MCR and Polyox WSR303 at the concentration of 13.88% showed 91.2% drug release at the end of 24 hours. Changing the viscosity grade of HPMC from K15MCR to K100MCR had no significant effect on drug release profile. Sodium bicarbonate and stearic acid in combination showed no significant effect on drug release profile. The formulations containing sodium bicarbonate 20 mg per tablet showed desired buoyancy (floating lag time of about 2 minutes and total floating time of >24 hours). The present study shows that polymers like HPMC K15MCR and Polyox WSR303 in combination with sodium bicarbonate as a gas generating agent can be used to develop sustained release floating tablets of ranitidine hydrochloride. PMID:23493037

  20. Simulation of synaptic short-term plasticity using Ba(CF3SO3)2-doped polyethylene oxide electrolyte film

    PubMed Central

    Chang, C. T.; Zeng, F.; Li, X. J.; Dong, W. S.; Lu, S. H.; Gao, S.; Pan, F.

    2016-01-01

    The simulation of synaptic plasticity using new materials is critical in the study of brain-inspired computing. Devices composed of Ba(CF3SO3)2-doped polyethylene oxide (PEO) electrolyte film were fabricated and with pulse responses found to resemble the synaptic short-term plasticity (STP) of both short-term depression (STD) and short-term facilitation (STF) synapses. The values of the charge and discharge peaks of the pulse responses did not vary with input number when the pulse frequency was sufficiently low(~1 Hz). However, when the frequency was increased, the charge and discharge peaks decreased and increased, respectively, in gradual trends and approached stable values with respect to the input number. These stable values varied with the input frequency, which resulted in the depressed and potentiated weight modifications of the charge and discharge peaks, respectively. These electrical properties simulated the high and low band-pass filtering effects of STD and STF, respectively. The simulations were consistent with biological results and the corresponding biological parameters were successfully extracted. The study verified the feasibility of using organic electrolytes to mimic STP. PMID:26739613

  1. Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma

    NASA Astrophysics Data System (ADS)

    Hu, Wen-Juan; Xie, Fen-Yan; Chen, Qiang; Weng, Jing

    2008-10-01

    We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C-O-C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C-O-C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

  2. Dynamics of a poly(ethylene oxide) tracer in a poly(methyl methacrylate) matrix: remarkable decoupling of local and global motions.

    PubMed

    Haley, Jeffrey C; Lodge, Timothy P

    2005-06-15

    The tracer diffusion coefficient of unentangled poly(ethylene oxide) (PEO, M=1000 gmol) in a matrix of poly(methyl methacrylate) (PMMA, M=10 000 gmol) has been measured over a temperature range from 125 to 220 degrees C with forced Rayleigh scattering. The dynamic viscosities of blends of two different high molecular weight PEO tracers (M=440 000 and 900 000 gmol) in the same PMMA matrix were also measured at temperatures ranging from 160 to 220 degrees C; failure of time-temperature superposition was observed for these systems. The monomeric friction factors for the PEO tracers were extracted from the diffusion coefficients and the rheological relaxation times using the Rouse model. The friction factors determined by diffusion and rheology were in good agreement, even though the molecular weights of the tracers differed by about three orders of magnitude. The PEO monomeric friction factors were compared with literature data for PEO segmental relaxation times measured directly with NMR. The monomeric friction factors of the PEO tracer in the PMMA matrix were found to be from two to six orders of magnitude greater than anticipated based on direct measurements of segmental dynamics. Additionally, the PEO tracer terminal dynamics are a much stronger function of temperature than the corresponding PEO segmental dynamics. These results indicate that the fastest PEO Rouse mode, inferred from diffusion and rheology, is completely separated from the bond reorientation of PEO detected by NMR. This result is unlike other blend systems in which global and local motions have been compared.

  3. Degradable polyethylene: fantasy or reality.

    PubMed

    Roy, Prasun K; Hakkarainen, Minna; Varma, Indra K; Albertsson, Ann-Christine

    2011-05-15

    Plastic waste disposal is one of the serious environmental issues being tackled by our society today. Polyethylene, particularly in packaging films, has received criticism as it tends to accumulate over a period of time, leaving behind an undesirable visual footprint. Degradable polyethylene, which would enter the eco-cycle harmlessly through biodegradation would be a desirable solution to this problem. However, the "degradable polyethylene" which is presently being promoted as an environmentally friendly alternative to the nondegradable counterpart, does not seem to meet this criterion. This article reviews the state of the art on the aspect of degradability of polyethylene containing pro-oxidants, and more importantly the effect these polymers could have on the environment in the long run. On exposure to heat, light, and oxygen, these polymers disintegrate into small fragments, thereby reducing or increasing the visual presence. However, these fragments can remain in the environment for prolonged time periods. This article also outlines important questions, particularly in terms of time scale of complete degradation, environmental fate of the polymer residues, and possible accumulation of toxins, the answers to which need to be established prior to accepting these polymers as environmentally benign alternatives to their nondegradable equivalents. It appears from the existing literature that our search for biodegradable polyethylene has not yet been realized.

  4. Synthesis and dose interval dependent hepatotoxicity evaluation of intravenously administered polyethylene glycol-8000 coated ultra-small superparamagnetic iron oxide nanoparticle on Wistar rats.

    PubMed

    Rajan, Balan; Sathish, Shanmugam; Balakumar, Subramanian; Devaki, Thiruvengadam

    2015-03-01

    Superparamagnetic iron oxide nanoparticles are being used in medical imaging, drug delivery, cancer therapy, and so on. However, there is a direct need to identify any nanotoxicity associated with these nanoparticles. However uncommon, drug-induced liver injury (DILI) is a major health concern that challenges pharmaceutical industry and drug regulatory agencies alike. In this study we have synthesized and evaluated the dose interval dependent hepatotoxicity of polyethylene glycol-8000 coated ultra-small superparamagnetic iron oxide nanoparticles (PUSPIOs). To assess the hepatotoxicity of intravenously injected PUSPIOs, alterations in basic clinical parameters, hematological parameters, hemolysis assay, serum levels of liver marker enzymes, serum and liver lipid peroxidation (LPO) levels, enzymatic antioxidant levels, and finally histology of liver, kidney, spleen, lung, brain, and heart tissues were studied in control and experimental Wistar rat groups over a 30-day period. The results of our study showed a significant increase in the aspartate transaminase (AST) enzyme activity at a dose of 10mg/kg b.w. PUSPIOs twice a week. Besides, alanine transaminase (ALT), alkaline phosphatase (ALP), and gamma-glutamyl transferase (γGT) enzyme activity showed a slender increase when compared with control experimental groups. A significant increase in the serum and liver LPO levels at a dose of 10mg/kg b.w. PUSPIOs twice a week was also observed. Histological analyses of liver, kidney, spleen, lung, brain and heart tissue samples showed no obvious uncharacteristic changes. In conclusion, PUSPIOs were found to posses excellent biocompatibility and Wistar rats showed much better drug tolerance to the dose of 10mg/kg b.w. per week than the dose of 10mg/kg b.w. twice a week for the period of 30 days.

  5. ABC copolymer silicone surfactant templating for biomimetic silicification.

    PubMed

    Sun, Bo; Guo, Caiyun; Yao, Yuan; Che, Shunai

    2012-07-15

    Using the ABC copolymer silicone surfactant polydimethylsiloxane (PDMS)-graft-(polyethylene oxide (PEO)-block-propylene oxide (PPO)) (PSEP, Scheme 1a) as a template and tetraethoxysilane (TEOS) as a silica source, silica particles with various structures and morphologies (i.e., disordered spherical micellar aggregation, two-dimensional p6mm mesostructure, asymmetric multi-layer non-equilibrium vesicles and symmetric monolayer vesicles) were synthesized by changing the synthesis temperature from 30 to 80 °C. Increasing the hydrophobicity of the surfactant by increasing the temperature resulted in an increase in the surfactant packing parameter g, which led to the mesophase transformation from micellar to cylinder and later to a lamellar structure. The good compatibility between the PDMS and the TEOS, the different natures of the hydrophobic PDMS and PPO segments, and the hydrolysis and condensation rates of TEOS enabled the variation of silicification structures. This novel silicone surfactant templating route and a new type of materials with highly ordered mesostructures and asymmetric morphologies provide a new insight into the molecular factors governing inorganic-organic mesophase and biosilicification for fabricating functionalized materials.

  6. Intermolecular interactions and solvent diffusion in ordered nanostructures formed by self-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Gu, Zhiyong

    Hydrogels formed by Poloxamer poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers find various pharmaceutical and biomedical applications. A variety of ordered structures can be exhibited by Poloxamer block copolymers in selective solvents such as water, for example, micellar cubic phase, hexagonal phase, lamellar phase, etc. We are interested in the thermodynamic and transport properties of water in such hydrogels that have an ordered (lyotropic liquid crystalline) structure. We have investigated the time evolution of water loss from Poloxamer gel films under a driving force of known water vapor pressure in the air in contact with the film. The experimental data on the drying process have been fitted to the diffusion equation for water in the film, under a boundary condition that includes the water concentration in the gel at infinite time; the water diffusion coefficient and other parameters have thus been obtained. The water chemical potential and osmotic pressure in the gel have been obtained from osmotic stress measurements. The osmotic pressure (force), together with data on the corresponding lyotropic liquid crystal spacing (distance) that we obtained from Small Angle X-Ray Scattering (SAXS) measurements, have been analyzed to provide information on the prevailing intermolecular (inter-assembly) forces in the gel. The forces in the gel reveal interactions that occur at two levels, that of the PEO coil and that of the PEO segment.

  7. Synthesis and aqueous solution properties of novel sugar methacrylate-based homopolymers and block copolymers.

    PubMed

    Narain, Ravin; Armes, Steven P

    2003-01-01

    We report the facile preparation of a range of novel, well-defined cyclic sugar methacrylate-based polymers without recourse to protecting group chemistry. 2-Gluconamidoethyl methacrylate (GAMA) and 2-lactobionamidoethyl methacrylate (LAMA) were prepared directly by reacting 2-aminoethyl methacrylate with D-gluconolactone and lactobionolactone, respectively. Homopolymerization of GAMA and LAMA by atom transfer radical polymerization (ATRP) gave reasonably low polydispersities as judged by aqueous gel permeation chromatography. A wide range of sugar-based block copolymers were prepared using near-monodisperse macroinitiators based on poly(ethylene oxide) [PEO], poly(propylene oxide) [PPO], or poly(e-caprolactone) [PCL] and/or by sequential monomer addition of other methacrylic monomers such as 2-(diethylamino)ethyl methacrylate [DEA], 2-(diisopropylaminoethyl methacrylate [DPA], or glycerol monomethacrylate [GMA]. The reversible micellar self-assembly of selected sugar-based block copolymers [PEO23-GAMA50-DEA100, PEO23-LAMA30-DEA50, PPO33-GAMA50, and PPO33-LAMA50] was studied in aqueous solution as a function of pH and temperature using dynamic light scattering, transmission electron microscopy, surface tensiometry, and 1H NMR spectroscopy.

  8. Polydispersity-Driven Block Copolymer Amphiphile Self-Assembly into Prolate-Spheroid Micelles

    SciTech Connect

    Schmitt, Andrew L.; Repollet-Pedrosa, Milton H.; Mahanthappa, Mahesh K.

    2013-09-26

    The aqueous self-assembly behavior of polydisperse poly(ethylene oxide-b-1,4-butadiene-b-ethylene oxide) (OBO) macromolecular triblock amphiphiles is examined to discern the implications of continuous polydispersity in the hydrophobic block on the resulting aqueous micellar morphologies of otherwise monodisperse polymer surfactants. The chain length polydispersity and implicit composition polydispersity of these samples furnishes a distribution of preferred interfacial curvatures, resulting in dilute aqueous block copolymer dispersions exhibiting coexisting spherical and rod-like micelles with vesicles in a single sample with a O weight fraction, w{sub O}, of 0.18. At higher w{sub O} = 0.51-0.68, the peak in the interfacial curvature distribution shifts and we observe the formation of only American football-shaped micelles. We rationalize the formation of these anisotropically shaped aggregates based on the intrinsic distribution of preferred curvatures adopted by the polydisperse copolymer amphiphiles and on the relief of core block chain stretching by chain-length-dependent intramicellar segregation.

  9. Comparison of stabilization by Vitamin E and 2,6-di-tert-butylphenols during polyethylene radio-thermal-oxidation

    NASA Astrophysics Data System (ADS)

    Richaud, Emmanuel

    2014-10-01

    This paper reports a compilation of data for PE+Vitamin E and 2,6-di-tert-butylphenols oxidation in radio-thermal ageing. Data unambiguously show that Vitamin E reacts with Prad and POOrad whereas 2,6-di-tert-butyl phenols only react with POOrad. Kinetic parameters of the stabilization reactions for both kinds of antioxidants were tentatively extracted from phenol depletion curves, and discussed regarding the structure of the stabilizer. They were also used for completing an existing kinetic model used for predicting the stabilization by antioxidants. This one permits to compare the efficiency of stabilizer with dose rate or sample thickness.

  10. Anisotropic Lithium Ion Conductivity in Single-Ion Diblock Copolymer Electrolyte Thin Films.

    PubMed

    Aissou, Karim; Mumtaz, Muhammad; Usluer, Özlem; Pécastaings, Gilles; Portale, Giuseppe; Fleury, Guillaume; Cloutet, Eric; Hadziioannou, Georges

    2016-02-01

    Well-defined single-ion diblock copolymers consisting of a Li-ion conductive poly(styrenesulfonyllithium(trifluoromethylsulfonyl)imide) (PSLiTFSI) block associated with a glassy polystyrene (PS) block have been synthesized via reversible addition fragmentation chain transfer polymerization. Conductivity anisotropy ratio up to 1000 has been achieved from PS-b-PSLiTFSI thin films by comparing Li-ion conductivities of out-of-plane (aligned) and in-plane (antialigned) cylinder morphologies at 40 °C. Blending of PS-b-PSLiTFSI thin films with poly(ethylene oxide) homopolymer (hPEO) enables a substantial improvement of Li-ion transport within aligned cylindrical domains, since hPEO, preferentially located in PSLiTFSI domains, is an excellent lithium-solvating material. Results are also compared with unblended and blended PSLiTFSI homopolymer (hPSLiTFSI) homologues, which reveals that ionic conductivity is improved when thin films are nanostructured.

  11. Asymmetric block copolymers for supramolecular templating of inorganic nanospace materials.

    PubMed

    Bastakoti, Bishnu Prasad; Li, Yunqi; Kimura, Tatsuo; Yamauchi, Yusuke

    2015-05-06

    This review focuses on polymeric micelles consisting of asymmetric block copolymers as designed templates for several inorganic nanospace materials with a wide variety of compositions. The presence of chemically distinct domains of asymmetric triblock and diblock copolymers provide self-assemblies with more diverse morphological and functional features than those constructed by EOn POm EOn type symmetric triblock copolymers, thereby affording well-designed nanospace materials. This strategy can produce unprecedented nanospace materials, which are very difficult to prepare through other conventional organic templating approaches. Here, the recent development on the synthesis of inorganic nanospace materials are mainly focused on, such as hollow spheres, tubes, and porous oxides, using asymmetric triblock copolymers.

  12. Processing-structure-property studies of: (I) submicron polymeric fibers produced by electrospinning and (II) films of linear low density polyethylenes as influenced by the short chain branch length in copolymers of ethylene/1-butene, ethylene/1-hexene and ethylene/1-octene synthesized by a single site metallocene catalyst

    NASA Astrophysics Data System (ADS)

    Gupta, Pankaj

    The overall theme of the research discussed in this dissertation has been to explore processing-structure-property relationships for submicron polymeric fibers produced by electrospinning (Part I) and to ascertain whether or not the length of the short chain branch has any effect on the physical properties of films of linear low-density polyethylenes (LLDPEs) (Part II). The research efforts discussed in Part I of this dissertation relate to some fundamental as well as more applied investigations involving electrospinning. These include investigating the effects of solution rheology on fiber formation and developing novel methodologies to fabricate polymeric mats comprising of high specific surface submicron fibers of more than one polymer, high chemical resistant substrates produced by in situ photo crosslinking during electrospinning, superparamagnetic flexible substrates by electrospinning a solution of an elastomeric polymer containing ferrite nanoparticles of Mn-Zn-Ni and substrates for filtration applications. Bicomponent electrospinning of poly(vinyl chloride)-polyurethane and poly(vinylidiene fluoride)-polyurethane was successfully performed. In addition, filtration properties of single and bicomponent electrospun mats of polyacrylonitrile and polystyrene were investigated. Results indicated lower aerosol penetration or higher filtration efficiencies of the filters based on submicron electrospun fibers in comparison to the conventional filter materials. In addition, Part II of this dissertation explores whether or not the length of the short chain branch affects the physical properties of blown and compression molded films of LLDPEs that were synthesized by a single site metallocene catalyst. Here, three resins based on copolymers of ethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene were utilized that were very similar in terms of their molecular weight and distribution, melt rheology, density, crystallinity and short chain branching content and

  13. Amine-reactive biodegradable diblock copolymers.

    PubMed

    Tessmar, Jörg K; Mikos, Antonios G; Göpferich, Achim

    2002-01-01

    A new class of diblock copolymers was synthesized from biodegradable poly(lactic acid) and poly(ethylene glycol)minus signmonoamine. These polymers were activated by covalently attaching linkers such as disuccinimidyl tartrate or disuccinimidyl succinate to the hydrophilic polymer chain. The polymers were characterized by (1)H NMR spectroscopy, (13)C NMR spectroscopy and gel permeation chromatography (GPC). These investigations indicated that the polymers were obtained with the correct composition, in high purities, and the expected molecular weight. By using dyes containing primary amine groups such as 5-aminoeosin as model substrates, it was possible to show that the polymers are able to bind such compounds covalently. The diblock copolymers were developed to suppress unspecific protein adsorption and allow the binding of bioactive molecules by instant surface modification. The polymers are intended to be used for tissue engineering applications where surface immobilized cell adhesion peptides or growth factors are needed to control cell behavior.

  14. Self-assembly of the triblock copolymer 17R4 poly(propylene oxide)₁₄-poly(ethylene oxide)₂₄-poly(propylene oxide)₁₄ in D₂O.

    PubMed

    Kumi, Bryna C; Hammouda, Boualem; Greer, Sandra C

    2014-11-15

    Our recent investigation of the three regions of the phase diagram of 17R4 in D2O (Huff et al., 2011) has led us to study the copolymer structure in this system by small-angle neutron scattering, rheometry, and dynamic light scattering. In region I at low temperatures and copolymer concentrations (0-30°C, 0.1-0.2 mass fraction ω), the cloudy solution contains the copolymer in large clusters made of hydrophobic PPO-rich "knots" bridged by dissolved hydrophilic PEO chains. These clusters vanish in region I at the lower temperatures and concentrations (below 39°C and ω=0.01). In region I over long times (weeks) at 25°C, a white liquid/gel film forms at the air-D2O interface. In region II at temperatures above the micellization line (above about 35°C, at ω=0.22) the large clusters dissipate and unimers coexist with "flower micelles," where the PPO blocks are the centers of the micelles and the PEO blocks loop into the solvent. In region III at still higher temperatures (above about 40°C at ω=0.2), the solution separates into coexisting liquid phases, where the upper phase of higher copolymer concentration is in region II, and the lower phase is in region I. The concentrated upper phase may contain micelles so crowded as to form a network.

  15. Poly(ethylene oxide)-bonded stationary phase for separation of inorganic anions in capillary ion chromatography.

    PubMed

    Linda, Roza; Lim, Lee Wah; Takeuchi, Toyohide

    2013-06-14

    A tosylated-poly(ethylene oxide) (PEO) reagent was reacted with primary amino groups of an aminopropylsilica packing material (TSKgel NH2-60) in acetonitrile to form PEO-bonded stationary phase. The reaction was a single and simple step reaction. The prepared stationary phase was able to separate inorganic anions. The retention behavior of six common inorganic anions on the prepared stationary phase was examined under various eluent conditions in order to clarify its separation/retention mechanism. The elution order of the tested anions was iodate, bromate, bromide, nitrate, iodide, and thiocyanate, which was similar as observed in common ion chromatography. The retention of inorganic anions could be manipulated by ion exchange interaction which is expected that the eluent cation is coordinated among the PEO chains and it works as the anion-exchange site. Cations and anions of the eluent therefore affected the retention of sample anions. We demonstrated that the retention of the analyte anions decreased with increasing eluent concentration. The repeatability of retention time for the six anions was satisfactory on this column with relative standard deviation values from 1.1 to 4.3% when 10mM sodium chloride was used as the eluent. Compared with the unmodified TSKgel NH2-60, the prepared stationary phase retained inorganic anions more strongly and the selectivity was also improved. The present stationary phase was applied for the determination of inorganic anions contained in various water samples.

  16. A bifunctional poly(ethylene glycol) silane immobilized on metallic oxide-based nanoparticles for conjugation with cell targeting agents

    SciTech Connect

    Kohler, Nathan J.; Fryxell, Glen E.; Zhang, Miqin

    2004-06-16

    A trifluoroethylester-terminal poly (ethylene glycol) (PEG) silane was synthesized and self-assembled on iron oxide nanoparticles. The nanoparticle system thus prepared has the flexibility to conjugate with cell targeting agents having either carboxylic and amine terminal groups for a number of biomedical applications, including magnetic resonance imaging (MRI) and controlled drug delivery. The trifluoroethylester silane was synthesized by modifying a PEG diacid to form the corresponding bistrifluoroethylester (TFEE), followed by a reaction with 3-aminopropyltriethoxysilane (APS). The APS coupled with PEG chains confers the stability of PEG self-assembled monolayers (SAMs) and increases the PEG packing density on nanoparticles by establishing hydrogen bonding between the carbonyl and amine groups present within the monolayer structure. The success of the synthesis of the PEG TEFE silane was confirmed with 1H NMR and Fourier transform infrared spectroscopy (FTIR). The conjugating flexibility of the PEG TEFE was demonstrated with folic acid having carboxylic acid groups and amine terminal groups respectively and confirmed by FTIR. TEM analysis showed the dispersion of nanoparticles before and after they were coated with PEG and folic acid.

  17. Iron oxide nanoparticles grafted with sulfonated copolymers are stable in concentrated brine at elevated temperatures and weakly adsorb on silica.

    PubMed

    Bagaria, Hitesh G; Xue, Zheng; Neilson, Bethany M; Worthen, Andrew J; Yoon, Ki Youl; Nayak, Susheela; Cheng, Victoria; Lee, Jae Ho; Bielawski, Christopher W; Johnston, Keith P

    2013-04-24

    Magnetic nanoparticles that can be transported in subsurface reservoirs at high salinities and temperatures are expected to have a major impact on enhanced oil recovery, carbon dioxide sequestration, and electromagnetic imaging. Herein we report a rare example of steric stabilization of iron oxide (IO) nanoparticles (NPs) grafted with poly(2-acrylamido-2-methylpropanesulfonate-co-acrylic acid) (poly(AMPS-co-AA)) that not only display colloidal stability in standard American Petroleum Institute (API) brine (8% NaCl + 2% CaCl2 by weight) at 90 °C for 1 month but also resist undesirable adsorption on silica surfaces (0.4% monolayer NPs). Because the AMPS groups interacted weakly with Ca(2+), they were sufficiently well solvated to provide steric stabilization. The PAA groups, in contrast, enabled covalent grafting of the poly(AMPS-co-AA) chains to amine-functionalized IO NPs via formation of amide bonds and prevented polymer desorption even after a 40,000-fold dilution. The aforementioned methodology may be readily adapted to stabilize a variety of other functional inorganic and organic NPs at high salinities and temperatures.

  18. Controlled release camptothecin tablets based on pluronic and poly(acrylic acid) copolymer. Effect of fabrication technique on drug stability, tablet structure, and release mode.

    PubMed

    Bromberg, Lev; Hatton, T Alan; Barreiro-Iglesias, Rafael; Alvarez-Lorenzo, Carmen; Concheiro, Angel

    2007-06-01

    Poly(ethylene oxide)-b-poly(propylene oxide)-b-(polyethylene oxide)-g-poly(acrylic acid), a graft-comb copolymer of Pluronic 127 and poly(acrylic acid) (Pluronic-PAA), was explored as an excipient for tablet dosage form of camptothecin (CPT). The tablets were prepared by either direct compression of the drug-polymer physical blend, suspension in ethanol followed by evaporation, or compression after kneading and characterized with respect to their physical structures, drug stability, and release behavior. Porosity and water uptake rate were strongly dependent on the fabrication procedure, ranking in the order: direct compression of physical blend > compression after suspension/evaporation in ethanol > compression after kneading. Tablets prepared by compression of physical blends swelled in water with a rapid surface gel layer formation that impeded swelling and disintegration of the tablets core. These tablets were able to sustain the CPT release for a period of time longer than those observed with the tablets made by either suspension/evaporation or kneading, which disintegrated within a few minutes. Despite the tablet disintegration, the CPT release was impeded for at least 6 hr, which was attributed to the ability of the Pluronic-PAA copolymers to form micellar aggregates at the hydrated surface of the particles. Physical mixing did not alter the fraction of CPT being in the pharmaceutically active lactone form, whilst the preparation of the tablets by the other two methods caused a significant reduction in the lactone form content. Tablets prepared from the physical blends demonstrated CPT release rates increasing with the pH due to the PAA ionization leading to the increase in the rate and extent of the tablet swelling. The results obtained demonstrate the potential of the Pluronic-PAA copolymers for the oral administration of chemotherapeutic agents.

  19. In vitro and in vivo evaluation of a new nanocomposite, containing high density polyethylene, tricalcium phosphate, hydroxyapatite, and magnesium oxide nanoparticles.

    PubMed

    Pourdanesh, Fereydoun; Jebali, Ali; Hekmatimoghaddam, Seyedhossein; Allaveisie, Azra

    2014-07-01

    In this study, a new nanocomposite, which contained high density polyethylene (HDPE), tricalcium phosphate (Ca3(PO4)2) nanoparticles (TCP NPs), hydroxyapatite nanoparticles (HA NPs), and magnesium oxide nanoparticles (MgO NPs) was prepared. As in vitro experiment, human osteoblasts (HOB) cells were exposed to pristine HDPE and its nanocomposite for a period of 1, 4, and 7 days at 37 °C, and then different assays were carried out, including osteoblast cell proliferation, Trypan blue staining, cell viability, alkaline phosphatase (ALP), and cell adhesion. Antibacterial property of pristine HDPE and its nanocomposite was evaluated, and also their mechanical properties were measured after 2 and 4 months. As in vivo experiment, pristine HDPE and its nanocomposite were separately implanted on calvarium bone of rabbits, and tissue inflammation and osteogenesis were investigated after 2, 4, and 6 months. In case of HOB cells treated with HDPE or nanocomposite, as incubation time was increased, cell proliferation, live/dead ratio, and cell viability were decreased. But, the ALP activity and cell adhesion of HOB cells which treated with nanocomposite were raised after increase of incubation time. This study demonstrated that although the mechanical properties of nanocomposite were similar to HDPE sheet, but their antibacterial property was not similar. The in vivo experiment showed that both pristine HDPE and its nanocomposite had same inflammation responses. Interestingly, osteogenesis was observed after 2 months at bone/nanocomposite interface, and was highly increased after 4 and 6 months. It must be noted that such pattern was not seen at bone/HDPE interface.

  20. Q-switched erbium doped fiber laser based on single and multiple walled carbon nanotubes embedded in polyethylene oxide film as saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmed, M. H. M.; Ali, N. M.; Salleh, Z. S.; Rahman, A. A.; Harun, S. W.; Manaf, M.; Arof, H.

    2015-01-01

    A passive, stable and low cost Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), which are embedded in polyethylene oxide (PEO) film as a saturable absorber (SA). The film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation operating at wavelength of 1533.6 nm. With SWCNTs, the laser produces a stable pulse train with repetition rate and pulse width ranging from 9.52 to 33.33 kHz and 16.8 to 8.0 μs while varying the 980 nm pump power from 48.5 mW to 100.4 mW. On the other hand, with MWCNTs, the repetition rate and pulse width can be tuned in a wider range of 6.12-33.62 kHz and 9.5- 4.2 μs, respectively as the pump power increases from 37.9 to 120.6 mW. The MWCNTs produce the pulse train at a lower threshold and attain a higher repetition rate compared to the SWCNTs. This is due to thicker carbon nanotubes layer of the MWCNTs which provides more absorption and consequently higher damage threshold. The Q-switched EDFL produces the highest pulse energy of 531 nJ at pump power of 37.9 mW with the use of MWCNTs-PEO SA.

  1. Multifunctional Photosensitizer Grafted on Polyethylene Glycol and Polyethylenimine Dual-Functionalized Nanographene Oxide for Cancer-Targeted Near-Infrared Imaging and Synergistic Phototherapy.

    PubMed

    Luo, Shenglin; Yang, Zhangyou; Tan, Xu; Wang, Yang; Zeng, Yiping; Wang, Yu; Li, Changming; Li, Rong; Shi, Chunmeng

    2016-07-13

    The integration of photodynamic therapy (PDT) with photothermal therapy (PTT) offers improved efficacy in cancer phototherapy. Herein, a PDT photosensitizer (IR-808) with cancer-targeting ability and near-infrared (NIR) sensitivity was chemically conjugated to both polyethylene glycol (PEG)- and branched polyethylenimine (BPEI)-functionalized nanographene oxide (NGO). Because the optimal laser wavelength (808 nm) of NGO for PTT is consistent with that of IR-808 for PDT, the IR-808-conjugated NGO sheets (NGO-808, 20-50 nm) generated both large amounts of reactive oxygen species (ROS) and local hyperthermia as a result of 808 nm laser irradiation. With PEG- and BPEI-modified NGO as the carrier, the tumor cellular uptake of NGO-808 exhibited higher efficacy than that of strongly hydrophobic free IR-808. Through evaluation with both human and mouse cancer cells, NGO-808 was demonstrated to provide significantly enhanced PDT and PTT effects compared to individual PDT using IR-808 or PTT using NGO. Furthermore, NGO-808 preferentially accumulated in cancer cells as mediated by organic-anion transporting polypeptides (OATPs) overexpressed in many cancer cells, providing the potential for highly specific cancer phototherapy. Using the targeting ability of NGO-808, in vivo NIR fluorescence imaging enabled tumors and their margins to be clearly visualized at 48 h after intravenous injection, providing a theranostic platform for imaging-guided cancer phototherapy. Remarkably, after a single injection of NGO-808 and 808 nm laser irradiation for 5 min, the tumors in two tumor xenograft models were ablated completely, and no tumor recurrence was observed. After treatment with NGO-808, no obvious toxicity was detected in comparison to control groups. Thus, high-performance cancer phototherapy with minimal side effects was afforded from synergistic PDT/PTT treatment and cancer-targeted accumulation of NGO-808.

  2. Drug release, cell adhesion and wound healing evaluations of electrospun carboxymethyl chitosan/polyethylene oxide nanofibres containing phenytoin sodium and vitamin C.

    PubMed

    Zarandi, Mohammad Amin; Zahedi, Payam; Rezaeian, Iraj; Salehpour, Alireza; Gholami, Mehdi; Motealleh, Behrooz

    2015-08-01

    In this work, N, O-carboxymethyl chitosan (CMCS) samples from virgin chitosan (CS) were synthesised and CMCS/polyethylene oxide (PEO) (50/50) blend nanofibrous samples were successfully electrospun from their aqueous solution. The electrospinning conditions to achieve smooth and fine diameter nanofibrous mats were optimised via D-optimal design approach. Afterwards, vitamin C and phenytoin sodium (PHT-Na) were added to these samples for producing wound dressing materials. H-nuclear magnetic resonance, scanning electron microscopy and Fourier transform infrared tests for the evaluation of functionalised CS, morphology and biodegradability studies of CMCS/PEO blend nanofibrous samples were applied. The kinetic and drug release mechanism for vitamin C and PHT-Na drug-loaded electrospun samples were also investigated by UV-vis spectrophotometer and high performance liquid chromatography, respectively. The results showed an approximately similar drug release rate of the two drugs and followed Higuchi's kinetic model. The stem cells viability and their adhesion on the surface of the samples containing PHT-Na and vitamin C were carried out using MTT assay and the best cells' biocompatibility was obtained using both drugs into the CMCS/PEO nanofibrous samples. Moreover, the in vivo animal wound model results revealed that the electrospun samples containing vitamin C and PHT-Na (1%) had a remarkable efficiency in the wounds' closure and their healing process compared with vitamin C/PHT-Na (50/50) ointment. Finally, the histology observations showed that the wound treated with optimised electrospun samples containing two drugs enabled regeneration of epidermis layers due to collagen fibres accumulation followed by granulating tissues formation without necrosis.

  3. Dynamics of poly(ethylene oxide) in a blend with poly(methyl methacrylate): A quasielastic neutron scattering and molecular dynamics simulations study

    SciTech Connect

    Genix, A.-C.; Arbe, A.

    2005-09-01

    In this paper, we have addressed the question of the dynamic miscibility in a blend characterized by very different glass-transition temperatures, T{sub g}, for the components: poly(ethylene oxide) and poly(methyl methacrylate) (PEO/PMMA). The combination of quasielastic neutron scattering with isotopic labeling and fully atomistic molecular dynamics simulations has allowed us to selectively investigate the dynamics of the two components in the picosecond--10 nanoseconds scale at temperatures close and above the T{sub g} of the blend. The main focus was on the PEO component, i.e., that of the lowest T{sub g}, but first we have characterized the dynamics of the other component in the blend and of the pure PEO homopolymer as reference. In the region investigated, the dynamics of PMMA in the blend is strongly affected by the {alpha}-methyl rotation; an additional process detected in the experimental window 65 K above the blend-T{sub g} can be identified as the merged {alpha}{beta} process of this component that shows strong deviations from Gaussian behavior. On the other hand, pure PEO displays entropy driven dynamics up to very large momentum transfers. Such kind of motion seems to freeze when the PEO chains are in the blend. There, we have directly observed a very heterogeneous and moreover confined dynamics for the PEO component. The presence of the hardly moving PMMA matrix leads to the creation of little pockets of mobility where PEO can move. The characteristic size of such confined islands of mobility might be estimated to be of {approx_equal}1 nm. These findings are corroborated by the simulation study, which has been an essential support and guide in our data analysis procedure.

  4. Chemical stability and bioadhesive properties of an ester prodrug of Delta 9-tetrahydrocannabinol in poly(ethylene oxide) matrices: effect of formulation additives.

    PubMed

    Thumma, Sridhar; Majumdar, Soumyajit; ElSohly, Mahmoud A; Gul, Waseem; Repka, Michael A

    2008-10-01

    The objective of the present research was to stabilize a novel hemiglutarate ester prodrug of Delta(9)-tetrahydrocannabinol (THC), in polyethylene oxide (PEO) polymeric matrices produced by hot-melt fabrication, for systemic delivery of THC through the oral transmucosal route. For this purpose, the influence of pH modifiers and antioxidants employed as stabilizing agents in these matrices was investigated. Based on the stability studies, two final formulations were made, and the stability of the active was assessed in these systems. In addition, the bioadhesive properties of PEO matrices were studied as a function of bioadhesive polymer type and concentration, contact time, drug loading and wetting time. Of all of the polymers investigated, bioadhesion was highest with Carbopol 971p. Bioadhesion increased with bioadhesive polymer concentration and wetting time to a certain level beyond which there was no further contribution. Both the contact time and drug loading influenced the bioadhesion. Severe degradation of the prodrug was observed during storage, even at room temperature (75% at the end of 3 months). Incorporation of the stabilizing agents in the PEO matrices reduced the degradation of the prodrug considerably. Citric acid was the most effective of all of the pH modifiers studied. Among the various antioxidants utilized, degradation was observed least in presence of BHT and ascorbic acid. Only 7.6% and 8.2% of prodrug degraded in these matrices, respectively, as compared to the PEO-only matrices (59.4%) at the end of 3 months at 25 degrees C/60% RH. The prodrug was very stable in both of the final formulations at the end of the 3 months at 40 degrees C/75% RH.

  5. Dynamics of a poly(ethylene oxide) tracer in a poly(methyl methacrylate) matrix: Remarkable decoupling of local and global motions

    NASA Astrophysics Data System (ADS)

    Haley, Jeffrey C.; Lodge, Timothy P.

    2005-06-01

    The tracer diffusion coefficient of unentangled poly(ethylene oxide) (PEO, M =1000g/mol) in a matrix of poly(methyl methacrylate) (PMMA, M =10000g/mol) has been measured over a temperature range from 125to220°C with forced Rayleigh scattering. The dynamic viscosities of blends of two different high molecular weight PEO tracers (M =440000 and 900000g/mol) in the same PMMA matrix were also measured at temperatures ranging from 160to220°C; failure of time-temperature superposition was observed for these systems. The monomeric friction factors for the PEO tracers were extracted from the diffusion coefficients and the rheological relaxation times using the Rouse model. The friction factors determined by diffusion and rheology were in good agreement, even though the molecular weights of the tracers differed by about three orders of magnitude. The PEO monomeric friction factors were compared with literature data for PEO segmental relaxation times measured directly with NMR. The monomeric friction factors of the PEO tracer in the PMMA matrix were found to be from two to six orders of magnitude greater than anticipated based on direct measurements of segmental dynamics. Additionally, the PEO tracer terminal dynamics are a much stronger function of temperature than the corresponding PEO segmental dynamics. These results indicate that the fastest PEO Rouse mode, inferred from diffusion and rheology, is completely separated from the bond reorientation of PEO detected by NMR. This result is unlike other blend systems in which global and local motions have been compared.

  6. Dynamics of poly(ethylene oxide) in a blend with poly(methyl methacrylate): a quasielastic neutron scattering and molecular dynamics simulations study.

    PubMed

    Genix, A-C; Arbe, A; Alvarez, F; Colmenero, J; Willner, L; Richter, D

    2005-09-01

    In this paper, we have addressed the question of the dynamic miscibility in a blend characterized by very different glass-transition temperatures, Tg, for the components: poly(ethylene oxide) and poly(methyl methacrylate) (PEO/PMMA). The combination of quasielastic neutron scattering with isotopic labeling and fully atomistic molecular dynamics simulations has allowed us to selectively investigate the dynamics of the two components in the picosecond-10 nanoseconds scale at temperatures close and above the Tg of the blend. The main