Grupo de Polimeros
Grupo de Polimeros
Velasquez C.L.,Grupo de Polimeros |
Rivas A.,Grupo de Polimeros |
Ocanto I.S.,Laboratorio Of Organica
Avances en Quimica | Year: 2014
Results obtained during the study of American Genipa L. fruits from the Venezuelan plains region in order to extract, characterize and quantify its content on the iridoid known as genipin are presented. It was possible to outline a simple procedure for obtaining the intended compound starting from the green fruits and maceration in CHCl3 although the yield was low (0.030 ± 0.005 % with respect to the initial mass of fruit); however, the same fruits stored under refrigeration for 41 days produced a higher yield (0.44 ± 0.06 %). The solid obtained was characterized by its melting point, specific rotation, FTIR and NMR spectroscopy (1H-NMR and 13C-NMR, uni- and bidimensional) and preparation of the mono 10-genipin mono (3,5-dinitrobenzoate) derivative (monoéster of the primary hydroxyl group in genipin).
Rangel-Rangel E.,Grupo de Polimeros |
Torres C.,Grupo de Polimeros |
Rincon L.,Grupo de Procesos Dinamicos en Quimica |
Koteich-Khatib S.,Laboratorio Of Resonancia Magnetica Nuclear |
Lopez-Carrasquero F.,Grupo de Polimeros
Revista Latinoamericana de Metalurgia y Materiales | Year: 2012
Low yields copolymerization of styrene (S) with di-n-alkylitaconates (DI-n) and methyl n-alkylitaconates (MeI-n) with alkyl side chain of 12, 14, 16, 18 and 22 carbon atoms were carried out in bulk via radical at 60°C with AIBN as initiator. The copolymers chemical structure was characterized by FTIR and 1H and 13C-NMR, and the composition was determined by 1H-NMR. The NMR studies indicate that the copolymers are random, but with some tendency to alternation. The monomers reactivity ratios between the styrene and itaconates in the copolymerization (ri) were calculated by the Fineman-Ross (FR), Kelen Tüdös (KT) methods and a modification of the last one. The obtained values of r1(DI) and r2(S) in the copolymerization among DI-n with n = 12, 14 and 16 with S were in the range of 0.22 to 0.28 for DI-n and 0.19 to 0.39 for S. Whereas for DI-n with n = 18 and 22 the values are in the order of 0.42-0.50 and 0.37-0.47 respectively. For the copolymer series derivatives of MeI-n the values were between 0.01-0.41 for the itaconate and 0.44-0.97 for S. © 2012 Universidad Simón Bolívar.
Rico M.,Grupo de Polimeros |
Lopez J.,Grupo de Polimeros |
Montero B.,Grupo de Polimeros |
Bouza R.,Grupo de Polimeros |
Diez F.J.,Grupo de Polimeros
European Polymer Journal | Year: 2014
The effect of varying the molecular weight of a thermoplastic modifier on the phase separation in polystyrene (PS)-modified epoxy/amine blends was investigated by comparing blends with PS of different molecular weights. A thermodynamic analysis of polymerization-induced phase separation was performed using a model based on the Flory-Huggins theory, from which the phase diagram and species distribution in the separated phases were calculated. Morphologies developed by the blends were studied in terms of concentration and molecular weight of modifier. Trends in morphologies and thermodynamics of phase separation were exposed and discussed. An increase in the molecular weight of modifier caused a decrease in the miscibility of blend affecting phase diagram, molecular fractionation between the separated phases and morphologies developed showing that molecular weight is a tool to control the final materials. © 2014 Elsevier Ltd. All rights reserved.