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PEO Segments (peo + segment)

Distribution by Scientific Domains

Polymers and Materials Science	87%

Selected Abstracts

Relationship between morphology structure and composition of polycaprolactone/Poly(ethylene oxide)/Polylactide copolymeric microspheres

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2002
Guangming Li
Abstract A novel tri-component copolymer, polycaprolactone/poly(ethylene oxide)/polylactide (PCEL) was synthesized. The effect of the chemical composition on physical properties was investigated by using NMR, differential scanning calorimetry (DSC) and X-ray diffraction. Both the soft segment poly(ethylene oxide) (PEO) and polycaprolactone (PCL) could enhance the mobility of polymer chains and decrease the crystallizability of the copolymers. The polymeric microspheres, which are of interest for drug delivery systems, were prepared using an emulsification-solvent evaporation technique. By scanning electron microscopy (SEM) and atomic force microscopy (AFM), the surface morphology of the microspheres was studied. It was found that the presence of PEO segment could improve the hydrophilicity of the copolymers and the morphology of the polymeric microspheres could be altered by adjusting the chemical composition. The accumulation of PEO segments on the outer surface of the polymeric microspheres was proven by X-ray photoelectron spectroscopy (XPS). It had also been proven that the PCL segment could facilitate the movement of PEO segment to the outer surface. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Surface properties of poly(ethylene oxide)-based segmented block copolymers with monodisperse hard segments

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009
D. Husken
Abstract The surface properties of segmented block copolymers based on poly(ethylene oxide) (PEO) segments and monodisperse crystallizable tetra-amide segments were studied. The monodisperse crystallizable segments (T6T6T) were based on terephthalate (T) and hexamethylenediamine (6). Due to the crystallinity of T6T6T being high (, 85%), the amount of amorphous T6T6T dissolved in the polyether phase was limited. The length of the PEO segments was varied (between 600 and 4600 g/mol) and effect of extending the PEO segments with terephthalic groups was investigated. Studied was the hydrophilicity of the surface by contact angle measurements and of the bulk copolymers by water absorption measurements The results were compared with data of PEO-poly(butylene terephthalate) (PEO-PBT) copolymers. For a given hydrophilicity of the bulk copolymer, the surface hydrophilicity decreased in the order PEO-PBT, PEO-T6T6T, and (PEO-T)-T6T6T. The use of short monodisperse hard segments resulted in low contact angles, with a lowest observed value of , 29°. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Binding and release studies of a cationic drug from a star-shaped four-arm poly(ethylene oxide)- b -poly(methacrylic acid)

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2010
E. He
Abstract Star-shape polymers possess higher densities of terminal functional groups and three-dimensional tetrahedron structure that induce significantly different association and interactions with drug compared to linear structure of identical molecular weights. Four-arm poly(ethylene oxide)- b -poly(methacrylic acid) block copolymer was synthesized by atom transfer radical polymerization technique, and it self-assembled into core-shell micelles and extended unimers at low and high pH respectively. The negatively charged carboxylate groups on the polymer chains interacted with a cationic drug through electrostatic interaction forming polymer/drug complexes stabilized by biocompatible hydrophilic PEO segments. The hydrodynamic radius (Rh) of the polymeric aggregates and polymer/drug complexes ranged from 46 to 84,nm and 32 to 55,nm at pH of 4.6 and 8.0 respectively, making them suitable for drug delivery applications. The thermodynamic parameters and interactions between polymer and drug were determined by isothermal titration calorimetric technique. The electrostatic force, hydrogen bonding and hydrophobic interactions controlled the characteristics of polymer/drug formation and complexes when the molar ratios of drug and polymer were varied. Drug selective electrode system was used to measure the dynamic release of imipramine hydrochloride (IPH) from multi-arm PEO- b -PMAA star polymer. The release exponent n was greater than 0.5 indicating a non-Fickian type diffusion behavior, where the release behavior was dominated by chain relaxation induced by ion exchange that was dependent on pH. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:782,793, 2010 [source]

Amphiphilic silicones prepared from branched PEO-silanes with siloxane tethers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2010
Ranjini Murthy
Abstract Amphiphilic silicones were prepared by the covalent incorporation of branched polyethylene oxide (PEO) via a siloxane tether. This was achieved by using six novel branched PEO-silanes with varying siloxane tether lengths and PEO molecular weight (Mn). Each PEO-silane was crosslinked via acid-catalyzed sol,gel condensation with ,,,-bis(Si-OH)polydimethylsiloxane (PDMS) (Mn = 3000 g/mol) to yield six amphiphilic silicone films. Film surface hydrophilicity increased with siloxane tether length, particularly after exposure to an aqueous environment, indicating that the PEO segments were more readily driven to the surface. This effect was more pronounced for films prepared with PEO-silanes containing lower Mn PEO segments. AFM was used to study surface reconstruction of films upon exposure to an aqueous environment. Adsorption of bovine serum albumin (BSA) and human fibrinogen (HF) proteins decreased with siloxane tether length, particularly after first exposing films to an aqueous environment. For a given siloxane tether length, relatively less BSA adsorbed onto films prepared with PEO-silanes with lower Mn PEO segments whereas less HF adsorbed onto films prepared with PEO-silanes with higher Mn PEO segments. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4108,4119, 2010 [source]

Segmented Block Copolymers with Terephthalic-Extended Poly(ethylene oxide) Segments

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2008
Debby Husken
Abstract Segmented block copolymers comprised of flexible PEO segments and monodisperse crystallizable bisestertetraamide segments have been synthesized. The influence of the terephthalic units in the soft phase on the transitions and the thermal mechanical and elastic properties are studied. The presence of terephthalic units in the copolymer increases the glass transition temperature of the soft phase by ,5,°C. The low-temperature flexibility of the copolymers is improved because of the lower crystallinity and melting temperature of PEO. With the use of terephthalic-extended PEO segments, segmented block copolymers with low moduli (G',<,15 MPa) and good elastic properties could be obtained. [source]

Synthesis of CdS Nanoparticles Dispersed Within Poly(urethane acrylate- co -styrene) Films Using an Amphiphilic Urethane Acrylate Nonionomer

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2006
Ju-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]