Thermoplastic elastomers: structural and morphological aspects of ether-esteramide copolymers

Polyesteramide 6NT6 (I)-polytetramethylene ether glycol (II) copolymers, pptd. from dil. soln. were studied by small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) with variation of the II content. A comparison of the structural characteristics of these materials was made with those of I, which consists of -CO-p-C6H4CONH(CH2)6NHCO-p-C6H4CO2(CH2)6O- units. Chain folding is assumed as the crystn. mechanism for the low-II content copolymers, with possible inclusion of polyether segments within the I crystal lattice. WAXS data support the view of a weakening of the I cryst. packing in the equatorial planes as the reason for broadening of the diffraction peaks, for changes in their relative intensities, and for the increase in the equatorial interplanar distances in the high-II content samples. The annealing behavior was investigated

Different aspects of solvent engineering in lipase catalysed esterifications

A microbial lipase from Pseudomonas sp., immobilized on an ACR-silica gel, has been used as catalyst for esterification reactions in organic solvents which were largely different in some fundamental physico-chemical characteristics. The results obtained were compared with the same reactions carried out in supercritical carbon dioxide. Significant variations in conversion values as function of log Pmow of the solvent (dielectric constants and Hildebrand solubility parameters not providing consistent results) seem to demonstrate the importance of the enzyme-water content on the mechanism of action as in terms of conformations arrangements as well as in terms of substrates partition equilibrium with the polar matrix. Differently, the conversions and enantioselectivity of the reactions in the supercritical fluid, always higher than in organic solvents, could be attributed to the specific properties of the medium in terms of low viscosity and surface pressure values and higher diffusivity of substrates in the supercritical phase

Complessi del cobalto (III) con il legante polimerico poli (4-vinilpiridina)

The preparation of a cobalt(IIT) complex with $Coen_2$ (en = ethylenediamine) units bound with two pyridine nitrogen atoms of two different polymeric chains of poly-(4-vynilpyridine) in trans position was performed. The obtained compound is insoluble in water as well as in the most usual organic solvents, while it has partial solubility in some others, such as dimethylsulfoxide. By elemental analysis it was found that for 12-13 average pyridine nitrogen atoms, one cobalt(III) atom is available

DOPING KINETICS OF POLYACETYLENE IN THE SHORT RANGE

La cinétique du dopage avec I2 de films de polyacétylène (PA), obtenus par la méthode de Shirakawa /1/, a été étudiée dans les premières minutes du contact entre le dopant et le PA en suivant la variation des propriétés électriques de conductivité et spectroscopique d'absorbance IR à 1400 cm-1 et à 1023 et 750 cm-1. Les données expérimentales ont mis en évidence l'existence, dans cet intervalle de temps, de au moins trois étapes de réaction caractérisées par des constantes cinétiques qui diffèrent par des ordres de grandeur. On a essayé d'élaborer un modèle cinétique du processus de dopage et on a calculé les valeurs des énergies d'activation.The kinetics of doping with iodine of Polyacetylene (PA) films, synthesized by the Shirakawa technique /1/, have been investigated by measuring the variation of electrical conductivity and IR absorbance at 1400, 1023 and 750 cm-1 within the time range of the first minute of doping. The experimental data suggest that the doping process occurs within at least three steps whose rate constants differ by orders of magnitude. An attempt is made to elaborate a kinetic model for the doping process and the activation energies are calculated