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Monomer Feed Ratio (monomer + feed_ratio)
Selected Abstracts,-Conjugated oligomers containing tropone in the main chain: Synthesis, characterization, and optical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2002Koji Takagi Abstract The synthesis and characterization of tropone-containing ,-conjugated oligomers were investigated. Two kinds of oligomers [1,4-phenylene type (4a,4e) and 2,5-thienylene type (5)] were successfully obtained by the Wittig polycondensation technique, in which the tropone content could be controlled by the monomer feed ratio for the 1,4-phenylene-type oligomers. The absorption maximum blueshifted and the emission intensity decreased with an increase in the tropone content in the oligomers. The emissive color could be tuned by the selection of the aromatic ring; that is, 4a,4e emitted orange-yellow light and 5 emitted either orange-yellow or red light according to the excitation wavelength. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3927,3937, 2002 [source] Copolymerization of propylene with various higher ,-olefins using silica-supported rac -Me2Si(Ind)2ZrCl2JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001Jun-Ting Xu Abstract The copolymerization of propylene with 1-hexene, 1-octene, 1-decene, and 1-dodecene was carried out with silica-supported rac -Me2Si(Ind)2ZrCl2 as a catalyst. The copolymerization activities of the homogeneous and supported catalysts and the microstructures of the resulting copolymers were compared. The activity of the supported catalyst was only one-half to one-eighth of that of the homogeneous catalyst, depending on the comonomer type. The supported catalyst copolymerized more comonomer into the polymer chain than the homogeneous catalyst at the same monomer feed ratio. Data of reactivity ratios showed that the depression in the activity of propylene instead of an enhancement in the activity of olefinic comonomer was responsible for this phenomenon. We also found that copolymerization with ,-olefins and supporting the metallocene on a carrier improved the stereoregularity and regioregularity of the copolymers. The melting temperature of all the copolymers decreased linearly with growing comonomer content, regardless of the comonomer type and catalyst system. Low mobility of the propagation chain in the supported catalyst was suggested as the reason for the different polymerization behaviors of the supported catalyst with the homogeneous system. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3294,3303, 2001 [source] Low Water Swelling and High Proton Conducting Sulfonated Poly(arylene ether) with Pendant Sulfoalkyl Groups for Proton Exchange MembranesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 24 2007Jinhui Pang Abstract Novel side-chain-type sulfonated poly(arylene ether) with pendant sulfoalkyl group copolymers (PSA-SPAE-6F) have been synthesized by direct copolymerization from a new sulfonated monomer, sodium 3-(4-(2,6-difluorobenzoyl)phenyl)propane-1-sulfonate. The sulfonate content could be easily controlled by adjusting the sulfonated and the unsulfonated monomer feed ratio. The obtained copolymers all show good thermal and mechanical properties. It should be noted that the most highly sulfonated copolymer, PSA-SPAE-6F90 with an ion exchange capacity of 1.30 mequiv,·,g,1, shows a proton conductivity of 0.11 S,·,cm,1 and a water swelling ratio of only 12.9% at 100,°C, which indicates its high proton conductivity and excellent dimensional stability in hot water. [source] Modeling of Semibatch Esterification Process for Poly(ethylene terephthalate) SynthesisMACROMOLECULAR REACTION ENGINEERING, Issue 4 2007Himanshu Patel Abstract The esterification kinetics of terephthalic acid (TPA) and ethylene glycol (EG) in poly(ethylene terephthalate) (PET) synthesis were studied using a semibatch reactor. Rate constants were optimized by data fitting with the oligomeric chain length, the fraction of carboxyl groups in the terminal groups (,) and the water generation curve for different EG/TPA feed ratios. The influence of the TPA particle size distribution on the solid-liquid mass transfer rate and on acid conversion (,) was investigated. It was observed that conversion became more sensitive towards TPA particle size as the EG/TPA feed ratio was lowered. It is advantageous to use the model based on TPA particle size for mass transfer limited esterification reactors. The effect of the monomer feed ratio on conversion, chain length and system heterogeneity can be predicted with this model. [source] Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains via metal-free anionic polymerization "grafting from" techniqueJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2010Junpeng Zhao Abstract Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains were synthesized via a "grafting from" technique. Poly(p -hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by random copolymerization of mixtures of oxyalkylene monomers, using metal-free anionic ring-opening polymerization, with the phosphazene base (t -BuP4) being the polymerization promoter. By controlling the monomer feed ratios in the graft copolymerization, two samples with the same side-chain length and different compositions were prepared, both of which possessed high molecular weights and low molecular weight distributions. The results from light scattering and fluorescence spectroscopy indicated that the brush copolymers in their dilute aqueous solutions were near completely solvated at low temperature and underwent slight intramolecular chain contraction/association and much more profound intermolecular aggregation at different stages of the step-by-step heating process. Above 50 °C, very turbid solutions, followed by macrophase separation, were observed for both of the samples, which implied that it was difficult for the brush copolymers to form stable nanoscopic aggregates at high temperature. All these observations were attributed, at least partly, to the distribution of the oxyalkylene monomers along the side chains and the overall brush-like molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2320,2328, 2010 [source] Synthesis and characterization of electrically conducting poly(o -/m -toluidine- co - o -/m -aminoacetophenone) copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2004P. Savitha Abstract A series of poly(o -/m -toluidine- co - o -/m -aminoacetophenone) copolymers combining the features of high conductivity and processibility are synthesized and characterized by a number of techniques including 1H NMR; thermogravimetry; IR, Raman, and UV,visible spectroscopy; scanning electron microscopy; and X-ray diffraction. The copolymers are synthesized by the emulsion and inverse emulsion methods using conventional ammonium persulfate and a new oxidant, benzoyl peroxide, respectively. The influence of the polymerization conditions such as the monomer feed ratios, solvent, and the nonsolvent is investigated. The composition of the resulting copolymers is determined by 1H NMR analysis. The conductivity of the copolymers varies with the aminoacetophenone content in the feed and the polymerization conditions. It is interesting that the conductivity of the copolymers is higher than that of the corresponding homopolymers. The results are rationalized on the basis of the effect of the COCH3 substituent on the polymer structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4300,4310, 2004 [source] Chemo-Enzymatic Synthesis of Raffinose-Branched Polyelectrolytes and Self-Assembly Application in Microcapsules,MACROMOLECULAR BIOSCIENCE, Issue 1 2006Qi Wu Abstract Summary: A novel biocompatible polyelectrolyte poly(vinyl raffinose- co -acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe2+/K2S2O8/H2O2 starting from enzymatically-synthesized monomer: 1- O -vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer-by-layer technique. The multilayers of PRCA/poly(methacryloyloxyethyl dimethylbenzyl ammonium chloride) (PMBA) on quartz slides and PRCA/poly(dimethyldiallyl ammonium chloride) (PDDA) on acyclovir crystals template were fabricated and characterized with UV-Vis spectra, the microelectrophoretic measurement, and TEM. Hollow capsules can be formed after the removal of acyclovir crystals template in a buffer solution. The nano-capsule-carrying galactose residue is a potential targeting drug-controlled delivery systems. Synthesis of PRCA and TEM image of a hollow (PRCA/PDDA)10 capsule. [source] Copolymerization of 2-Acrylamido-2-methyl-1-propanesulfonic Acid and 1-Vinylimidazole in Inverse MiniemulsionMACROMOLECULAR REACTION ENGINEERING, Issue 2 2008Susann Wiechers Abstract The copolymerization behavior of the acidic monomer 2-acrylamido-2-methyl-1-propanesulfonic acid (APSA) and 1-vinylimidazole in inverse miniemulsion was studied under various conditions. Initially, different surfactants and surfactant concentrations were investigated. After determining a suitable composition of the miniemulsion, changes in the reaction behavior under different pH values and monomer feed compositions were studied. The highest polymerization rates could be produced under neutral conditions over all monomer feed ratios. The addition of acid or base to change the pH value of the monomer mixture also has influence on the polymers obtained. The thermal stability, rheological stiffness and intrinsic viscosity increase when Na-APSA is incorporated. [source] Synthesis and Characterization of Degradable p(HEMA) Microgels: Use of Acid-Labile CrosslinkersMACROMOLECULAR BIOSCIENCE, Issue 4 2007Volga Bulmus Abstract New divinyl-functionalized acetal-based crosslinkers were synthesized as building elements to form acid-labile microgel particles for controlled-release applications. The synthesized crosslinkers underwent hydrolysis at slightly acidic pHs in less than 1 h while they were stable at neutral pHs for longer times. HEMA was copolymerized with the crosslinkers via an inverse emulsion polymerization technique using a redox initiator system at room temperature to form crosslinked, colloidal p(HEMA) microgels. Microgels in diameters ranging from 150 to 475 nm with narrow distribution could be produced. The crosslinking density and the diameter of the microgels were found to be controlled by monomer/crosslinker feed ratio. The microgels demonstrated a pH-dependent cleavage behavior that mimicked the pH-dependent hydrolysis profile of the acid-labile crosslinkers. Model biomacromolecules, i.e., Rhodamine B-labeled dextran and BSA were efficiently loaded into the microgels. The release of the biomolecules from p(HEMA) microgels was also found to be controllable by the pH of the environment similar to the particle degradation. The protein released from the microgels was observed to retain its structural stability. [source] | ||||||||||