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Monomer Distribution (monomer + distribution)
Selected AbstractsAmphiphilic gradient copolymers containing fluorinated 2-phenyl-2-oxazolines: Microwave-assisted one-pot synthesis and self-assembly in waterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2008Matthias Lobert Abstract Here, we present the one-step synthesis of 2-(m -difluorophenyl)-2-oxazoline and its use as a monomer for microwave-assisted statistical cationic ring-opening copolymerizations (CROP). Well-defined amphiphilic gradient copolymers, as evidenced by the polymerization kinetics, were prepared using 2-ethyl-2-oxazoline as comonomer and methyl tosylate as initiator in nitromethane at 140 °C. The resulting gradient copolymers (DP = 60 and 100) were characterized by means of size exclusion chromatography and 1H NMR spectroscopy. In the second part, we focus on a detailed study of the self-assembly of the copolymers in aqueous solution using atomic force microscopy and dynamic light scattering. Both methods revealed the self-assembly of the gradient copolymers into spherical micelles. To quantify the influence of the fluorine atoms and the monomer distribution on the self-assembly, a comparative study with gradient copolymers of 2-phenyl-2-oxazoline and 2-ethyl-2-oxazoline was performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5859,5868, 2008 [source] Synthesis, characterization, and cross-linking of a library of statistical copolymers based on 2-"soy alkyl"-2-oxazoline and 2-ethyl-2-oxazolineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2007Richard Hoogenboom Abstract The synthesis of statistical copolymers consisting of 2-ethyl-2-oxazoline (EtOx) and 2-"soy alkyl"-2-oxazoline (SoyOx) via a microwave-assisted cationic ring-opening polymerization procedure is described. The majority of the resulting copolymers revealed polydispersity indices below 1.30. The reactivity ratios (rEtOx 1.4 ± 0.3; rSoyOx = 1.7 ± 0.3) revealed a clustered monomer distribution throughout the polymer chains. The thermal and surface properties of the pEtOx- stat -SoyOx copolymers were analyzed before and after UV-curing demonstrating the decreased chain mobility after cross-linking. In addition, the cross-linked materials showed shape-persistent swelling upon absorption of water from the air, whereby as little as 5 mol % SoyOx was found to provide efficient cross-linking. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5371,,5379, 2007 [source] Preparation of gradient copolymers via ATRP using a simultaneous reverse and normal initiation process.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2005Abstract Spontaneous gradient copolymers were prepared in both bulk and miniemulsion systems via Atom Transfer Radical Polymerization (ATRP) utilizing a Simultaneous Reverse and Normal Initiation (SR & NI) process. Both instantaneous and cumulative compositions were used to characterize the gradient copolymers. The gradient copolymers were obtained with an array of gradient compositions ranging from a subtle to strong variation in monomer distribution along the polymer backbones, depending on the ratio of comonomers initially added to the copolymerization system. The compositions of the gradient copolymer produced in miniemulsion systems were similar to those generated in bulk. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3616,3622, 2005 [source] Cross-Linked Poly(, -caprolactone/D,L -lactide) Copolymers with Elastic PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2002Antti O. Helminen Abstract Cross-linked , -caprolactone (CL) and D,L -lactide (DLLA) copolymers with elastic properties were synthesized in three steps. First, the monomers were copolymerized in ring-opening polymerization to obtain telechelic star-shaped oligomers with almost completely random monomer distribution. The oligomers were methacrylated with methacrylic anhydride in the second step and cured in a third. Molar CL/DLLA compositions of 30/70, 50/50, 70/30, 90/10, and 100/0 were used to obtain elastic structures with a wide range of properties. The effect of the average length of the copolymer block on the properties of the networks was evaluated with three different co-initiator contents (0.5, 1.0, and 2.0/100) in the oligomer synthesis. The oligomers were characterized by 13C NMR spectroscopy, size-exclusion chromatography (SEC), and differential-scanning calorimetry (DSC). The formation of elastic networks was confirmed by the absence of a flow region in dynamic mechanical analysis (DMA), the increase in Tg in DSC, and the full recovery of the sample dimensions after tensile testing. In addition, gel contents were high and the samples swelled in CH2Cl2. The networks possessed break stresses from 0.7,9.7 MPa with elongations from 80,350%. Networks with 100 or 90% of , -caprolactone retained their form in vitro for 12 weeks, but an increase in lactide content made the networks more vulnerable to hydrolysis. Water absorption of the polymers during hydrolysis. [source] | ||||||||||