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Experimental Molecular Weights (experimental + molecular_weight)
Selected AbstractsSynthesis of Random Copolymers Poly (methylmethacrylate- co -azo monomer) by ATRP-AGETMACROMOLECULAR SYMPOSIA, Issue 1 2009M.A. Nájera Abstract The synthesis of the azo molecule 1-(2-(4-nitrophenyl) diazenyl) naphtalen-2-ol which has been functionalized with a methacryloxyl fraction is now reported. This azo monomer was copolymerized with methyl methacrylate (MMA) by ATRP where the active species is prepared "in situ" after the reduction reaction of the metal complex Cu (II) - HMTETA by tin 2-ethylhexanoate in 2-butanone as solvent. Experimental conditions for the controlled homopolymerization of MMA were established. By adjusting the amount of reducing agent, a good correlation between theoretical and experimental molecular weight was obtained. Such conditions were also employed for the random copolymerization of MMA with the synthesized azo monomer. [source] Atom transfer radical polymerization of n -butyl acrylate catalyzed by CuBr/N -(n -hexyl)-2-pyridylmethanimineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Huiqi Zhang Abstract The homogeneous atom transfer radical polymerization (ATRP) of n -butyl acrylate with CuBr/N -(n -hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different solvents such as toluene, anisole, N,N -dimethylformamide, and 1-butanol were linear throughout the reactions, and the experimental molecular weights increased linearly with increasing monomer conversion and were very close to the theoretical values. These, together with the relatively narrow molecular weight distributions (polydispersity index , 1.40 in most cases with monomer conversion > 50%), indicated that the polymerization was living and controlled. Toluene appeared to be the best solvent for the studied ATRP system in terms of the polymerization rate and molecular weight distribution among the solvents used. The polymerization showed zero order with respect to both the initiator and the catalyst, probably because of the presence of a self-regulation process at the beginning of the reaction. The reaction temperature had a positive effect on the polymerization rate, and the optimum reaction temperature was found to be 100 °C. An apparent enthalpy of activation of 81.2 kJ/mol was determined for the ATRP of n -butyl acrylate, corresponding to an enthalpy of equilibrium of 63.6 kJ/mol. An apparent enthalpy of activation of 52.8 kJ/mol was also obtained for the ATRP of methyl methacrylate under similar reaction conditions. Moreover, the CuBr/N -(n -hexyl)-2-pyridylmethanimine-based system was proven to be applicable to living block copolymerization and living random copolymerization of n -butyl acrylate with methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3549,3561, 2002 [source] Nonstoichiometric polycondensation I. synthesis of polythioether from dibromomethane and 4,4,-thiobisbenzenethiolMACROMOLECULAR SYMPOSIA, Issue 1 2003Hirokazu Iimori Abstract High molecular weight poly(phenylene thioether) (3) was successfully obtained by the polycondensation of 4,4,-thiobisbenzenethiol (1) and dibromomethane (2) with a variety of feed ratios in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in 1-methyl-2-pyrrolidinone (NMP) at 75°C. The resulting polymer showed the maximum inherent viscosity (,inh) of 0.50 dL/g in 4 h when 1.5 equivalents excess of 2 was used. The model reaction using benzenethiol (4) and dichloromethane (5) in the presence of DBU in deuterated dimethylsulfoxide (DMSO- d6) at 25°C indicated that the rate of the second nucleophilic displacement reaction (k2) is 61 times faster than that of the first one (k1). The maximum of theoretical molecular weights calculated at various stoichiometric imbalance (S) under the condition of k2/k1 = 61 showed a good agreement with the experimental molecular weights at specific polymerization times. [source] Surface-initiated nitroxide-mediated polymerization: a tool for hybrid inorganic/organic nanocomposites ,in situ' synthesisPOLYMER INTERNATIONAL, Issue 10 2006Leďla Ghannam Abstract Hybrid silica particles comprised of an inorganic core and an organic polymer shell can be synthesized by surface-initiated nitroxide-mediated polymerization (SINMP) in the presence of a grafted alkoxyamine as initiator. The layer of initiator molecules attached or adsorbed to the particles surface is based on a nitroxide group. The synthesis and characterization of these alkoxyamine structures are briefly described. The grafted initiator particles are studied in order to determine the nature of the anchorage sites and the grafting density. With a stable radical or nitroxide as chain-growth moderator tethered to the inorganic core, it was demonstrated that the grafting from or to SINMP exhibits a control character with a very low polydispersity and good agreement between theoretical/experimental molecular weights. A comparative review of different alkoxyamines with a bimolecular system based on a grafted azoic initiator in the presence of an acyclic ,-phosphonylated nitroxide called SG1 is also described. Moreover, original methods for the synthesis of alkoxyamine grafted surface by in situ trapping of carbon radicals and some new developments for colored pigments will be reported. These topics could be one of the directions of the field in the next years. Copyright © 2006 Society of Chemical Industry [source] | ||||||||||