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Hydrophilic Poly (hydrophilic + poly)
Selected AbstractsMicellar Structures of Hydrophilic/Lipophilic and Hydrophilic/Fluorophilic Poly(2-oxazoline) Diblock Copolymers in WaterMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2008Ruzha Ivanova Abstract Amphiphilic poly(2-alkyl-2-oxazoline) diblock copolymers of 2-methyl-2-oxazoline (MOx) building the hydrophilic block and either 2-nonyl-2-oxazoline (NOx) for the hydrophobic or 2-(1H,1H,,2H,2H,-perfluorohexyl)-2-oxazoline (FOx) for the fluorophilic block were synthesized by sequential living cationic polymerization. The polymer amphiphiles form core/shell micelles in aqueous solution as evidenced using small-angle neutron scattering (SANS). Whereas the diblock copolymer micelles with a hydrophobic NOxn block are spherical, the micelles with the fluorophilic FOxn are slightly elongated, as observed by SANS and TEM. In water, the micelles with fluorophilic and lipophilic cores do not mix, but coexist. [source] Electroconductive Hydrogels: Electrical and Electrochemical Properties of Polypyrrole-Poly(HEMA) CompositesELECTROANALYSIS, Issue 7 2005Sean Brahim Abstract Composites of inherently conductive polypyrrole (PPy) within highly hydrophilic poly(2-hydroxyethyl methacrylate)-based hydrogels (p(HEMA)) have been fabricated and their electrochemical properties investigated. The electrochemical characteristics observed by cyclic voltammetry suggest less facile reduction of PPy within the composite hydrogel compared to electropolymerized PPy, as shown by the shift in the reduction peak potential from ,472,mV for electropolymerized polypyrrole to ,636,mV for the electroconductive composite gel. The network impedance magnitude for the electroconductive hydrogel remains quite low, ca. 100,,, even upon approach to DC, over all frequencies and at all offset potentials suggesting retained electronic (bipolaronic) conductivity within the composite. In contrast, sustained application of +0.7 V (vs. Ag/AgCl, 3,M Cl,) for typically 100,min. (conditioning) to reduce the background amperometric current to <1.0,,A, resulted in complete loss of electroactivity. Nyquist plots suggest that sustained application of such a modest potential to the composite hydrogel results in impedance characteristics that resembles p(HEMA) without evidence of the conducting polymer component. PPy composite gels supported a larger ferrocene monocarboxylate diffusivity (Dappt=7.97×10,5,cm2,s,1) compared to electropolymerized PPy (Dappt=5.56×10,5,cm2,s,1), however a marked reduction in diffusivity (Dappt=1.01×10,5,cm2,s,1) was observed with the conditioned hydrogel composite. Cyclic voltammograms in buffer containing H2O2 showed an absence of redox peaks for electrodes coated with PPy-containing membranes, suggesting possible chemical oxidation of polypyrrole by the oxidant [source] High-Nanofiller-Content Graphene Oxide,Polymer Nanocomposites via Vacuum-Assisted Self-AssemblyADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Karl W. Putz Abstract Highly ordered, homogeneous polymer nanocomposites of layered graphene oxide are prepared using a vacuum-assisted self-assembly (VASA) technique. In VASA, all components (nanofiller and polymer) are pre-mixed prior to assembly under a flow, making it compatible with either hydrophilic poly(vinyl alcohol) (PVA) or hydrophobic poly(methyl methacrylate) (PMMA) for the preparation of composites with over 50 wt% filler. This process is complimentary to layer-by-layer assembly, where the assembling components are required to interact strongly (e.g., via Coulombic attraction). The nanosheets within the VASA-assembled composites exhibit a high degree of order with tunable intersheet spacing, depending on the polymer content. Graphene oxide,PVA nanocomposites, prepared from water, exhibit greatly improved modulus values in comparison to films of either pure PVA or pure graphene oxide. Modulus values for graphene oxide,PMMA nanocomposites, prepared from dimethylformamide, are intermediate to those of the pure components. The differences in structure, modulus, and strength can be attributed to the gallery composition, specifically the hydrogen bonding ability of the intercalating species [source] Dual-Tone Patterned Mesoporous Silicate Films Templated From Chemically Amplified Block CopolymersADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Sivakumar Nagarajan Abstract Directly patterned mesoporous silicate films are prepared using positive- and negative-tone strategies by performing phase selective silica condensation within lithographically exposed poly(styrene- b - tert -butyl acrylate) (PS- b -PtbA) templates containing photoacid generators. The use of supercritical fluid as a process medium enables rapid diffusion of the silicate precursor within the prepatterned block copolymer template film without disrupting its morphology. Template exposure through the mask triggers area selective generation of acid, which in turn both deprotects the poly(tert -butyl acrylate) block to yield a poly(acrylic acid) block and provides a catalyst for silica precursor condensation yielding pattern formation at the device level. Because the acid generated in the UV exposed field preferentially segregates into hydrophilic poly(acrylic acid) domains of the phase segregated, deprotected block copolymer, precursor condensation is simultaneously controlled at nanoscopic length scales via templating by the underlying block copolymer morphology. The ability of PS- b -PtbA to undergo chemical transformation in two stages, deprotection followed by crosslinking, enables precise replications of the photomask in positive and negative tones. Detemplating via calcination yields patterned mesoporous silicate films without etching. Template formulations are optimized using infrared spectroscopic studies and the silicate films are characterized using electron microscopy and scanning force microscopy. [source] Anti-thrombogenicity of styrene-butadiene-styrene triblock copolymer grafted with poly(ethylene glycol)sJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Masanobu Nagura Abstract We transformed hydrophobic/hydrophobic styrene/butadiene/styrene tri-block copolymer (SBS) to hydrophobic / hydrophilic microphase-separated surfaces by grafting with hydrophilic poly(ethylene glycol) (PEG) on poly(butadiene) (PB) domain via hydrocarboxylation and hydrobromination and investigated the anti-thrombogenicity of these surfaces. In the case of SBS cast film from toluene solution, PEG was densely grafted because of the development of an unevenness on the order of several 10 nm on the surface, which had a huge surface area in comparison with poly(butadiene) rubber with its uniformly smooth surface. Grafted PEG (molecular weight = 600) was found to clearly inhibit adhesion and activation of platelets and coagulation of the whole blood component, which is indicative of anti-thrombogenicity. These properties correspond to a surface coated by a copolymer of 2-methacryloyl-oxyethyl phosphorylcholine and n -butyl methacrylate, which is well known to be the best excellent anti-thrombogenic material in the world. Melt-molded SBS film, which also has an uneveness on the order of several 10 nm, showed similar excellent anti-thrombogenicity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Well-defined amphiphilic graft copolymer consisting of hydrophilic poly(acrylic acid) backbone and hydrophobic poly(vinyl acetate) side chainsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Yaogong Li Abstract A series of well-defined amphiphilic graft copolymers containing hydrophilic poly(acrylic acid) (PAA) backbone and hydrophobic poly(vinyl acetate) (PVAc) side chains were synthesized via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization followed by selective hydrolysis of poly(tert -butyl acrylate) backbone. A new Br-containing acrylate monomer, tert -butyl 2-((2-bromopropanoyloxy)methyl) acrylate, was first prepared, which can be polymerized via RAFT in a controlled way to obtain a well-defined homopolymer with narrow molecular weight distribution (Mw/Mn = 1.08). This homopolymer was transformed into xanthate-functionalized macromolecular chain transfer agent by reacting with o -ethyl xanthic acid potassium salt. Grafting-from strategy was employed to synthesize PtBA- g -PVAc well-defined graft copolymers with narrow molecular weight distributions (Mw/Mn < 1.40) via RAFT of vinyl acetate using macromolecular chain transfer agent. The final PAA- g -PVAc amphiphilic graft copolymers were obtained by selective acidic hydrolysis of PtBA backbone in acidic environment without affecting the side chains. The critical micelle concentrations in aqueous media were determined by fluorescence probe technique. The micelle morphologies were found to be spheres. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6032,6043, 2009 [source] Synthesis and characterization of pH sensitive poly(glycidol)- b -poly(4-vinylpyridine) block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2009Sebastian Mendrek Abstract Block copolymers of poly(glycidol)- b -poly(4 -vinylpyridine) were obtained by ATRP of 4-vinylpyridine initiated by ,-(2-chloropropionyl) poly(glycidol) macroinitiators. By changing the monomer/macroinitiator ratio in the synthesis polymers with varied P4VP/PGl molar ratio were obtained. The obtained block copolymers showed pH sensitive solubility. It was found that the linkage of a hydrophilic poly(glycidol) block to a P4VP influenced the pKa value of P4VP. DLS measurements showed the formation of fully collapsed aggregates exceeding pH 4.7. Above this pH values the collapsed P4VP core of the aggregates was stabilized by a surrounding hydrophilic poly(glycidol) corona. The size of the aggregates depended significantly upon the composition of the block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1782,1794, 2009 [source] Solid-supported amphiphilic triblock copolymer membranes grafted from gold surfaceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2009Ekaterina Rakhmatullina Abstract Gold-supported amphiphilic triblock copolymer brushes composed of two hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) blocks and a hydrophobic poly(n -butyl methacrylate) (PBMA) middle part were synthesized using a surface-initiated ATRP. Attenuated total reflectance Fourier transform infrared spectroscopy, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), ellipsometry, contact angle measurements, and atomic force microscopy were used for the characterization of PHEMA- co -PBMA- co -PHEMA brushes. The PM-IRRAS analysis revealed an increase of the chain tilt toward the gold surface during growth of the individual blocks. We suggest that the orientation of the amphiphilic polymer brushes is influenced by both the chain length and the interchain interactions. Additionally, a detachment of the polymer membranes from the solid support and subsequent gel permeation chromatography analyses allowed us to establish their compositions. We applied block-selective solvents (water and hexane) as well as a good solvent for the whole polymer chain (ethanol) to study the morphology and solvent responsive behavior of the amphiphilic brushes. The presented results could serve as a good starting point for the fabrication of functional solid-supported membranes for biosensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1,13, 2009 [source] Photophysical and self-assembly behavior of poly(amidoamine) dendrons with chromophore as scaffold: The effect of dendritic architectureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Bing-Bing Wang Abstract Two series of amphiphiles composed of hydrophilic poly(amidoamine) dendrons (from the first to the third generation) as the shell and hydrophobic aromatic chromophores (3,6-di(maleimidyl)-9-phenyl carbazole and 9-(4,-maleimidyl phenyl)-3-maleimidyl carbazole) as the central scaffold were synthesized. The effect of dendritic architecture on the photophysical properties and the self-assembly behavior of these amphiphiles were studied by UV,vis absorption spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM) measurements. Both the generation of dendritic shell and the location of dendrons at the chromophoric scaffold had great effect on the photophysical properties of these amphiphiles. In addition, different spherical aggregates were formed from these amphiphiles in the aqueous solution at different concentrations. Because of the combined effects of steric hindrance and architecture of dendritic shells, the amphiphiles from G2 dendron with central chromophore self-organized into ordered aggregates more readily than that from G1 and G3. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4584,4593, 2008 [source] Synthesis and supramolecular self-assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether coreJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008Haiyan Hong Abstract A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3-ethyl-3-(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self-assembly. All the copolymers directly aggregated into core,shell unimolecular micelles (around 10 nm) and size-controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature-dependent release properties of HBPO- star -PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin-loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668,681, 2008 [source] A starlike amphiphilic graft copolymer with hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chainsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007Dan Peng Abstract A well-defined starlike amphiphilic graft copolymer bearing hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chains was synthesized by successive atom transfer radical polymerization followed by the hydrolysis of poly-(methoxymethyl acrylate) backbone. A grafting-from strategy was employed for the synthesis of a graft copolymer with narrow molecular weight distribution. Hydrophobic polystyrene side chains were connected to the backbones through stable CC bonds. The poly(methoxymethyl acrylate) backbones can be easily hydrolyzed with HCl without affecting the hydrophobic polystyrene side chains. This kind of amphiphilic graft copolymer can form stable sphere micelles in water. The sizes of the micelles were dependent on the ionic strength and pH value. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3687,3697, 2007 [source] Synthesis of amphiphilic copolymer brushes: Poly(ethylene oxide)-graft-polystyreneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2006Zhongyu Li Abstract A well-defined amphiphilic copolymer brush with poly(ethylene oxide) as the main chain and polystyrene as the side chain was successfully prepared by a combination of anionic polymerization and atom transfer radical polymerization (ATRP). The glycidol was first protected by ethyl vinyl ether to form 2,3-epoxypropyl-1-ethoxyethyl ether and then copolymerized with ethylene oxide by the initiation of a mixture of diphenylmethylpotassium and triethylene glycol to give the well-defined polymer poly(ethylene oxide- co -2,3-epoxypropyl-1-ethoxyethyl ether); the latter was hydrolyzed under acidic conditions, and then the recovered copolymer of ethylene oxide and glycidol {poly(ethylene oxide- co -glycidol) [poly(EO- co -Gly)]} with multiple pending hydroxymethyl groups was esterified with 2-bromoisobutyryl bromide to produce the macro-ATRP initiator [poly(EO- co -Gly)(ATRP). The latter was used to initiate the polymerization of styrene to form the amphiphilic copolymer brushes. The object products and intermediates were characterized with 1H NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Fourier transform infrared, and size exclusion chromatography in detail. In all cases, the molecular weight distribution of the copolymer brushes was rather narrow (weight-average molecular weight/number-average molecular weight < 1.2), and the linear dependence of ln[M0]/[M] (where [M0] is the initial monomer concentration and [M] is the monomer concentration at a certain time) on time demonstrated that the styrene polymerization was well controlled. This method has universal significance for the preparation of copolymer brushes with hydrophilic poly(ethylene oxide) as the main chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4361,4371, 2006 [source] Synthesis and interfacial behaviors of amphiphilic poly(oxypropylene) amidoacidsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Kuan-Liang Wei Abstract A series of hydrophobic poly(oxypropylene) (POP)-backboned and hydrophilic poly(oxyethylene)-backboned amidoacids and imidoacids were prepared through the reaction of poly(oxyalkylene) diamines and trimellitic anhydride (TMA) under mild conditions. The synthesized copolymers were characterized with nuclear magnetic resonance and Fourier transform infrared. Their ability to lower the water surface tension and toluene/water interfacial tension was measured and correlated with the hydrophobic/hydrophilic balance with multiple sodium carboxylate functionalities. The specific POP2000/TMA copolymers, consisting of a 2000 g/mol POP segment and multiple amidoacid functionalities, enabled the demonstration of a strong surfactant tendency and a critical micelle concentration at 0.1 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 646,652, 2006 [source] Ideal tetrafunctional amphiphilic PEG/PDMS conetworks by a dual-purpose extender/crosslinker.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Abstract The synthesis of a new type of amphiphilic conetwork (APCN) consisting of well-defined hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments is described. The conetwork is ideal (the lengths of each PEG and PDMS chain segments, respectively, are identical) and tetrafunctional (exactly four chains emanate from each crosslink site). The synthesis of the conetworks was achieved by the use of a novel dual-purpose extender/crosslinker Y (bis [(dimethylsilyl)oxy]-[(etoxydimethylsilyl)oxy]phenylsilane, (SiPh(SiH)2OEt)), in two steps: (1) Synthesis of a new linear random multiblock copolymer (MBC) (AY)n(BY)m, where A is the hydrophilic PEG and B is the hydrophobic segment, and (2) Crosslinking the multiblocks by catalytic condensation of the SiOEt groups in the Y units. The extender/crosslinker fulfills two totally different functions: First, it extends two incompatible hydrophilic and hydrophobic prepolymers (PEG and PDMS) to a random MBC, and, subsequently, it cross-links the multiblocks to the target APCN. The synthesis and characterization of the extender/crosslinker is also presented. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4953,4964, 2005 [source] Novel materials for bioanalytical and biomedical applications: Environmental response and binding/release capabilities of amphiphilic hydrogels with shape-persistent dendritic junctions,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2005Chao Zhu Abstract The binding and release capabilities of a hydrogel series, constructed of hydrophilic poly(ethylene glycol) segments and hydrophobic dendritic junctions [poly (benzyl ether)s], are evaluated in aqueous media. The environmental response of the amphiphilic networks is also tested in water at three pH values: 1.5, 7.0, and 10.1. The highest swelling ratio is observed under acidic conditions and varies between 3.7 and 6.5, depending on the crosslinking density and dendrimer generation. Gel specimens with embedded indicators react within 3,6 s with a clear color switch to the change in the pH of the surrounding medium. The experiments with model anionic and cationic indicators and stains show that the hydrogels have basic interiors. The gel binding capabilities depend on the water solubility of the substrate and on the size of the incorporated dendritic fragments. Model release studies have been performed at 37 °C and pHs 1.5, 7.0, and 10.1. The observed phenomena are explained by the transformations in the structure and charge that both the networks and the model compounds undergo with the changes in the pH of the aqueous medium. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4017,4029, 2005 [source] Environmentally responsive micelles from polystyrene,poly[bis(potassium carboxylatophenoxy)phosphazene] block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005Youngkyu Chang Abstract Amphiphilic diblock copolymers that contained hydrophilic poly[bis(potassium carboxylatophenoxy)phosphazene] segments and hydrophobic polystyrene sections were synthesized via the controlled cationic polymerization of Cl3PNSiMe3 with a polystyrenyl,phosphoranimine as a macromolecular terminator. These block copolymers self-associated in aqueous media to form micellar structures which were investigated by fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. The size and shape of the micelles were not affected by the introduction of different monovalent cations (Li+, K+, Na+, and Cs+) into the stable micellar solutions. However, exposure to divalent cations induced intermicellar crosslinking through carboxylate groups, which caused precipitation of the ionically crosslinked aggregates from solution. This micelle-coupling behavior was reversible: the subsequent addition of monovalent cations caused the redispersion of the polystyrene- block -poly[bis(potassium carboxylatophenoxy)phosphazene] (PS,KPCPP) block copolymers into a stable micellar solution. Aqueous micellar solutions of PS,KPCPP copolymers also showed pH-dependent behavior. These attributes make PS,KPCPP block copolymers suitable for studies of guest retention and release in response to ion charge and pH. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2912,2920, 2005 [source] Direct synthesis of amphiphilic block copolymers from glycidyl methacrylate and poly(ethylene glycol) by cationic ring-opening polymerization and supramolecular self-assembly thereofJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2005Wei Huang Abstract Amphiphilic block copolymers composed of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic poly(glycidyl methacrylate) (PGMA) block were synthesized through cationic ring-opening polymerization with PEG as the precursor. The model reactions indicated that the reactivity of the epoxy groups was higher than that of the double bonds in the bifunctional monomer glycidyl methacrylate (GMA) under the cationic polymerization conditions. Through the control of the reaction time in the synthesis of block copolymer PEG- b -PGMA, a linear GMA block was obtained through the ring-opening polymerization of epoxy groups, whereas the double bond in GMA remained unreacted. The results showed that the molecular weight of the PEG precursor had little influence on the grafting of GMA, and the PGMA blocks almost kept the same length, despite the difference of the PEG blocks. In addition, the PGMA blocks only consisted of several GMA units. The obtained amphiphilic PEG- b -PGMA block copolymers could form polymeric core,shell micelles by direct molecular self-assembly in water. The crosslinking of the PGMA core of the PEG- b -PGMA micelles, induced by ultraviolet radiation and heat instead of crosslinking agents, greatly increased the stability of the micelles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2038,2047, 2005 [source] Hyperbranched Fluoropolymers and their Hybridization into Complex Amphiphilic Crosslinked Copolymer NetworksMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2007Jeremy W. Bartels Abstract This feature article highlights three types of hyperbranched fluoropolymers (HBFPs) with different structural features, which were synthesized by either polycondensation of fluorinated ABx monomers or self-condensing vinyl (co)polymerization of fluorinated inimers and/or fluorinated comonomers. Amphiphilic crosslinked networks with hybridization of these hydrophobic HBFPs and linear hydrophilic poly(ethylene glycol)s are also discussed. As microphase-segregated materials with nanoscale surface heterogeneities, these networks possessed unusual anti-biofouling abilities, atypical sequestration and release behaviors for guest molecules, and special mechanical properties. [source] Synthesis of CdS Nanoparticles Dispersed Within Poly(urethane acrylate- co -styrene) Films Using an Amphiphilic Urethane Acrylate NonionomerMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2006Ju-Young Kim Abstract Summary: CdS nanoparticles dispersed within poly(urethane acrylate- co -styrene) (PUCS) films were prepared using amphiphilic urethane acrylate nonionomer (UAN) precursor chains, which had a poly(propylene oxide)-based hydrophobic segment and a hydrophilic poly(ethylene oxide) segment. CdS nanoparticles were first prepared and dispersed in UAN/styrene mixtures, and then these nano-colloid solutions could be directly converted to CdS/PUCS nanocomposite films via radical bulk polymerization process. Formation of CdS nanoparticles was confirmed by UV absorption spectra, PL emission spectra and TEM images. The size of the CdS nanoparticles was varied from 10.2 to 14.5 nm, in correlation with the increase of amount of cadmium salt in the preparation composition, which was also confirmed by a red shift in the UV and PL emission spectra. In the course of the formation of the CdS nanoparticles within the UAN/styrene mixtures, the PEO segments of UAN are microphase-separated from the hydrophobic segments of UAN and styrene to make a complex with the cadmium cations and stabilize the CdS nanoparticles. This was also confirmed by TEM images and DMA measurements. TEM micrograph of the polyurethane acrylate films containing CdS nanoparticles, prepared using a weight fraction of cadmium acetate of 0.125 wt.-%. [source] Synthesis and characterization of hydrogels containing biodegradable polymersPOLYMER INTERNATIONAL, Issue 7 2008Adina Cretu Abstract BACKGROUND: Amphiphilic block and graft copolymers constitute a very interesting class of polymers with potential for biomedical applications, due to their special characteristics, which derive from the combination of properties of hydrophilic and hydrophobic moieties. In this work, the synthesis and biodegradation of poly(2-hydroxyethyl methacrylate)- graft -poly(L -lactide) are studied. RESULTS: The graft copolymers were synthesized using the macromonomer technique. In a first step, methacryloyl-terminated poly(L -lactide) macromonomers were synthesized in a wide molecular weight range using different catalysts. Subsequently, these macromonomers were copolymerized with 2-hydroxyethyl methacrylate in order to obtain a graft copolymer. These new materials resemble hydrogel scaffolds with a biodegradable component. The biodegradation was studied in hydrolytic and enzymatic environments. The influence of different parameters (molecular weight, crystallinity, ratio between hydrophilic and hydrophobic components) on the degradation rate was investigated. CONCLUSION: Based on this study it will be possible to tailor the release properties of biodegradable materials. In addition, the materials will show good biocompatibility due to the hydrophilic poly(2-hydroxyethyl methacrylate) hydrogel scaffold. This kind of material has potential for many applications, like controlled drug-delivery systems or biodegradable implants. Copyright © 2008 Society of Chemical Industry [source] Cancer-associated pH-responsive tetracopolymeric micelles composed of poly(ethylene glycol)- b -poly(L -histidine)- b -poly(L -lactic acid)- b -poly(ethylene glycol)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008Kyung Taek Oh Abstract To create a novel vector for specifically delivering anticancer therapy to solid tumors, we used diafiltration to synthesize pH-sensitive polymeric micelles. The micelles, formed from a tetrablock copolymer [poly(ethylene glycol) -b -poly(L -histidine)- b -poly(L -lactic acid)- b -poly(ethylene glycol)] consisted of a hydrophobic poly(L -histidine) (polyHis) and poly(L -lactic acid) (PLA) core and a hydrophilic poly(ethylene glycol) (PEG) shell, in which we encapsulated the model anticancer drug doxorubicin (DOX). The robust micelles exhibited a critical micellar concentration (CMC) of 2.1,3.5,µg/ml and an average size of 65,80,nm pH 7.4. Importantly, they showed a pH-dependent micellar destabilization, due to the concurrent ionization of the polyHis and the rigidity of the PLA in the micellar core. In particular, the molecular weight of PLA block affected the ionization of the micellar core. Depending on the molecular weight of the PLA block, the micelles triggering released DOX at pH 6.8 (i.e. cancer acidic pH) or pH 6.4 (i.e. endosomal pH), making this system a useful tool for specifically treating solid cancers or delivering cytoplasmic cargo in vivo. Copyright © 2008 John Wiley & Sons, Ltd. [source] Rapid Protein Anchoring into the Membranes of Mammalian Cells Using Oleyl Chain and Poly(ethylene glycol) DerivativesBIOTECHNOLOGY PROGRESS, Issue 3 2004Koichi Kato The cell membrane is an important interface for communication with extracellular events, and incorporation of bioactive substances, such as antibodies and receptors, into the cell membrane may enhance the potential abilities of cells. Gene manipulation, chemical modification of membrane proteins, and cell surface painting using a GPI anchor have been performed to introduce substances into cell membranes. Furthermore, many lipid anchors have also been used to modify lipid membranes such as liposomes. In this study, we have focused on developing an easy and rapid method for anchoring of substances including macromolecular proteins into the membranes of living mammalian cells. We employed a single oleyl chain derivative coupled with hydrophilic poly(ethylene glycol) (PEG90, the ethyleneoxide (EO) unit is 90) to facilitate solubilization in water. This water-soluble derivative was designated Biocompatible Anchor for Membrane (BAM). Some proteins (streptavidin, EGFP and an antibody) were coupled with BAM90 at the distal terminal of PEG and rapidly (within a few minutes) anchored into the membranes of various cells (NIH3T3, 32D, Ba/F3, hybridoma 9E10). However, the anchored BAM90 disappeared from the cell membranes within 4,5 h in serum-free culture media, and moreover, the retention time of anchoring was shortened (1,2 h) in culture medium containing 10% FBS. We further prepared a dioleylphosphatidylethanolamine (DOPE)-PEG derivative (DOPE-BAM80, the EO unit is 80) as a double oleyl chain derivative for comparison with the single oleyl chain derivative, BAM90. The retention time of anchored DOPE-BAM80 was longer than that of BAM90 and more than 8 h in culture media with and without 10% serum. Furthermore, the treatment time of DOPE-BAM80 for anchoring was nearly as short (within a few minutes) as that of BAM90. In addition, both types of BAMs, BAM90 and DOPE-BAM80, showed no cytotoxicity. Therefore, DOPE-BAM80 is useful for protein anchoring to cells. Although the utilization of BAM90 is considered to be limited, it is expected to useful in restricted environments, for example, in tissues such as the cornea, peritoneum, bladder, and various mucosae, which are less exposed to serum. Thus, we suggest the possibility that both types of BAM can be applied to cell surface engineering. [source] Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT PolymerizationCHINESE JOURNAL OF CHEMISTRY, Issue 11 2009Yongjun Chen Abstract Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl-based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The PFCB-containing acrylate monomer, p -(2-(p -tolyloxy)perfluorocyclobutoxy)-phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2,-azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number-average molecular weights (Mn) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (Mw/Mn,1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4-cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG-CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB-based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique. [source] | |||||||||||||