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Pyridine Solution (pyridine + solution)
Selected AbstractsPolyesterification of aromatic dicarboxylic acids and bisphenols with tosyl chloride/dimethylformamide/pyridine promoted by the improvement of the difficult solubility of the activated diacids with lithium chlorideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2004Fukuji Higashi Abstract The solution polyesterification of dicarboxylic acids in pyridine, the activated intermediates of which were difficult to dissolve in tosyl chloride/dimethylformamide/pyridine, was investigated in the presence of lithium chloride. The solubility of the activated dicarboxylic acids was largely improved by the presence of the salt, and the polycondensation with bisphenols was greatly facilitated. The salt was more effectively added to a pyridine solution of dicarboxylic acids than to the activated dicarboxylic acids in pyridine. The favorable additive effect on the improved solubility was attributed to a lowered degree of association of the activated dicarboxylic acids, which led to distributions of the resulting oligomers from bisphenols at an earlier stage closer to the theoretical ones and yielded better polycondensation results. The reaction, which proceeded through favorable distributions of the co-oligomers, produced copolymers of higher inherent viscosities and slightly block sequence distributions determined by NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2725,2733, 2004 [source] Main-chain, thermotropic, liquid-crystalline, hydrogen-bonded polymers of 4,4,-bipyridyl with aliphatic dicarboxylic acidsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2003Pradip K. Bhowmik Abstract A series of main-chain, thermotropic, liquid-crystalline (LC), hydrogen-bonded polymers or self-assembled structures based on 4,4,-bipyridyl as a hydrogen-bond acceptor and aliphatic dicarboxylic acids, such as adipic and sebacic acids, as hydrogen-bond donors were prepared by a slow evaporation technique from a pyridine solution and were characterized for their thermotropic, LC properties with a number of experimental techniques. The homopolymer of 4,4,-bipyridyl with adipic acid exhibited high-order and low-order smectic phases, and that with sebacic acid exhibited only a high-order smectic phase. Like the homopolymer with adipic acid, the two copolymers of 4,4,-bipyridyl with adipic and sebacic acids (75/25 and 25/75) also exhibited two types of smectic phases. In contrast, the copolymer of 4,4,-bipyridyl with adipic and sebacic acids (50/50), like the homopolymer with sebacic acid, exhibited only one high-order smectic phase. Each of them, including the copolymers, had a broad temperature range of LC phases (36,51 °C). The effect of copolymerization for these hydrogen-bonded polymers on the thermotropic properties was examined. Generally, copolymerization increased the temperature range of LC phases for these polymers, as expected, with a larger decrease in the crystal-to-LC transition than in the LC-to-isotropic transition. Additionally, it neither suppressed the formation of smectic phases nor promoted the formation of a nematic phase in these hydrogen-bonded polymers, as usually observed in many thermotropic LC polymers. The thermal transitions for all of them, measured by differential scanning calorimetry, were well below their decomposition temperatures, as measured by thermogravimetric analysis, which were in the temperature range of 193,210 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1282,1295, 2003 [source] Synthesis of poly(methyl methacrylate) in a pyridine solution by atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001José Luis de la Fuente Abstract Pyridine was used as a solvent for the atom transfer radical polymerization (ATRP) of methyl methacrylate. The homopolymerizations were carried out with methyl 2-halopropionate (MeXPr, where X was Cl or Br) as an initiator, copper halide (CuX) as a catalyst, and 2,2,-bipyridine as a ligand from 80 to 120 °C. The mixed halogen system methyl 2-bromopropionate/copper chloride was also used. For all the initiator systems used, the polymerization reaction showed linear first-order rate plots, a linear increase in the number-average molecular weight with conversion, and relatively low polydispersities. In addition, the dependence of the polymerization rate on the temperature is presented. These data are compared with those obtained in bulk, demonstrating the effectiveness of this solvent for this monomer in ATRP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3443,3450, 2001 [source] Microwave-assisted synthesis and characterization of heterocyclic, and optically active poly(amide-imide)s incorporating L -amino acidsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008Abdol R. Hajipour Abstract N,N,-Pyromelliticdiimido-di- L -alanine (1), N,N,-pyromelliticdiimido-di- L -phenylalanine (2), and N,N,-pyromelliticdiimido-di- L -leucine (3) were prepared from the reaction of pyromellitic dianhydride with corresponding L -amino acids in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. The microwave-assisted polycondensation of the corresponding diimide-diacyl chloride monomers (5,7) with 4-phenyl-2,6-bis(4-aminophenyl) pyridine (10) or 4-(p -methylthiophenyl)-2,6-bis(4-aminophenyl) pyridine (12) were carried out in a laboratory microwave oven. The resulting poly(amide-imide)s were obtained in quantitative yields, and they showed admirable inherent viscosities (0.12,0.55 dlg,1), were soluble in polar aprotic solvents, showed good thermal stability and high optical purity. The synthetic compounds were characterized by IR, MS, 1H NMR, and 13C NMR spectroscopy, elemental analysis, and specific rotation. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||