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Initiator Molar Ratio (initiator + molar_ratio)
Selected AbstractsKinetic study of methacrylate copolymerization systems by thermoanalysis methodsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Ali Habibi Abstract The free-radical solution copolymerization of isobutyl methacrylate with lauryl methacrylate in the presence of an inhibitor was studied with thermoanalysis methods. A set of inhibited polymerization experiments was designed. Four different levels of initial inhibitor/initiator molar ratios were considered. In situ polymerization experiments were carried out with differential scanning calorimetry. Furthermore, to determine the impact of the polymerization media on the rate of initiation, the kinetics of the initiator decomposition were followed with nonisothermal thermoanalysis methods, and the results were compared with in situ polymerization counterparts. The robust M -estimation method was used to retrieve the kinetic parameters of the copolymerization system. This estimation method led to a reasonable prediction error for the dataset with strong multicollinearity. The model-free isoconversional method was employed to find the variation of the Arrhenius activation energy with the conversion. It was found that robust M -estimation outperformed existing methods of estimation in terms of statistical precision and computational speed, while maintaining good robustness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Induction of chemical and moisture resistance in Saccharum spontaneum L fiber through graft copolymerization with methyl methacrylate and study of morphological changesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Balbir Singh Kaith Abstract In this article, morphological modification of Saccharum spontaneum L, a natural fiber through graft copolymerization with methylmethacrylate using ferrous ammonium sulfate,potassium per sulfate redox initiator has been reported. Different reaction parameters such as reaction temperature, time, initiator molar ratio, monomer concentration, pH and solvent were optimized to get maximum graft yield (144%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron microscopy, X-ray diffraction and thermogravimetric, differential thermal analysis, and differential thermogravimetric techniques. Graft copolymer has been found to be more moisture resistant and also showed higher chemical and thermal resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Synthesis of poly(4-vinylpyridine) by reverse atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Gregory T. Lewis Abstract Controlled radical polymerization of 4-vinylpyridine (4VP) was achieved in a 50 vol % 1-methyl-2-pyrrolidone/water solvent mixture using a 2,2,-azobis(2,4-dimethylpentanitrile) initiator and a CuCl2/2,2,-bipyridine catalyst,ligand complex, for an initial monomer concentration of [M]0 = 2.32,3.24 M and a temperature range of 70,80 °C. Radical polymerization control was achieved at catalyst to initiator molar ratios in the range of 1.3:1 to 1.6:1. First-order kinetics of the rate of polymerization (with respect to the monomer), linear increase of the number,average degree of polymerization with monomer conversion, and a polydispersity index in the range of 1.29,1.35 were indicative of controlled radical polymerization. The highest number,average degree of polymerization of 247 (number,average molecular weight = 26,000 g/mol) was achieved at a temperature of 70 °C, [M]0 = 3.24 M and a catalyst to initiator molar ratio of 1.6:1. Over the temperature range studied (70,80 °C), the initiator efficiency increased from 50 to 64% whereas the apparent polymerization rate constant increased by about 60%. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5748,5758, 2007 [source] Synthesis of homopolymers and multiblock copolymers by the living ring-opening metathesis polymerization of norbornenes containing acetyl-protected carbohydrates with well-defined ruthenium and molybdenum initiatorsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2004Yoshitaka Miyamoto Abstract The ring-opening metathesis polymerization (ROMP) of norbornenes containing acetyl-protected glucose [2,3,4,6-tetra- O -acetyl-glucos-1- O -yl 5-norbornene-2-carboxylate (1)] and maltose [2,3,6,2,,3,,4,,6,-hepta- O -acetyl-maltos-1- O -yl 5-norbornene-2-carboxylate (2)] was explored in the presence of Mo(N -2,6- iPr2C6H3)(CHCMe2Ph)(OtBu)2 (A), Ru(CHPh)(Cl)2(PCy3)2 (B; Cy = cyclohexyl), and Ru(CHPh)(Cl)2(IMesH2)(PCy3) (C; IMesH2 = 1,3-dimesityl-4,5-dihydromidazol-2-ylidene). The polymerizations promoted by B and A proceeded in a living fashion with exclusive initiation efficiency, and the resultant polymers possessed number-average molecular weights that were very close to those calculated on the basis of the monomer/initiator molar ratios and narrow molecular weight distributions (weight-average molecular weight/number-average molecular weight < 1.18) in all cases. The observed catalytic activity of B was strongly dependent on both the initial monomer concentration and the solvent employed, whereas the polymerization initiated with A was completed efficiently even at low initial monomer concentrations. The polymerization with C also took place efficiently, and even the polymerization with 1000 equiv of 1 was completed within 2 h. First-order relationships between the propagation rates and the monomer concentrations were observed for all the polymerization runs, and the estimated rate constants at 25 °C increased in the following order: A > C > B. On the basis of these results, we concluded that ROMP with A was more suitable than ROMP with B or C for the efficient and precise preparation of polymers containing carbohydrates. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4248,4265, 2004 [source] | ||||||||||