Browsing by Author "Diaz, F"

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    Degradation of the electrical properties of chlorine-doped poly(seleno-p-arylen diamine)s
    (1996) MHarzi, H; Safoula, G; Conan, A; Bernede, JC; Diaz, F; Godoy, A; Molinie, P; Spiesser, M
    The changes in the conductivity of chlorine-doped poly(seleno-p-arylen diamine)s have been studied with temperature, storage time and ambient atmosphere, The samples have also been studied using X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR). The conductivity of the polymers with carbonyl in their backbone decreases with storage time but is insensitive to oxygen, The decrease in conductivity with time is attributed to the breaking of the Se-N bonds by chlorine attack, which induces polymer degradation as shown by XPS. The conductivity of the polymers without carbonyl in their backbone was increased by oxygen. This increase can be attributed to oxidation of these polymers and to bipolaron formation as shown by ESR measurements. (C) 1996 Elsevier Science Limited
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    Photochemical and photopolymerization study of 2,6-dihalogen derivatives of p-nitroaniline in the presence of N,N-dimethylaniline as a bimolecular photoinitiator system
    (1997) Costela, A; GarciaMoreno, I; Diaz, F; Dabrio, J; Sastre, R
    Steady-state photolysis at 365 nm has been employed to carry out a structure-reactivity investigation of the 2,6-dihalogen derivatives of p-nitroaniline (pNA). Detailed studies of the spectroscopy of these molecules were accomplished. Photoreduction behavior of the 2,6-dihalogen derivatives of p-nitroaniline in the presence of N,N-dimethylaniline (DMA) has been analyzed. The efficiency of these compounds as photoinitiators was studied by following the polymerization kinetics of the lauryl acrylate (LA) monomer by differential scanning photo-calorimetry (Photo-DSC) under aerobic and anaerobic conditions. Using size exclusion chromatography (SEC) analysis of the polymers their number-average molecular weights, the number-average degree of polymerization, and the length of the kinetic chain were determined and information on the nature of the end-chain groups and the chain-transfer behavior of these photoinitiators systems were obtained. The polymerization activity of the 2,6-dihalogen derivatives of pNA proved to be higher than those obtained with conventional aromatic ketone photoinitiators.
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    Vinyltrimethylsilane-co-methylmethacrylate copolymers. Synthesis and reactivity ratios
    (MARCEL DEKKER INC, 2000) Gatica, N; Alegria, S; Tagle, LH; Diaz, F; Gargallo, L; Radic, D
    In order to obtain information about the copolymerization process of vinyltrimethyl silane with comonomers of different chemical structure, copolymers containing vinyltrimethylsilane and methyl methacrylate at different compositions were synthesized and characterized. Comparison of the reactivity ratios of the resulting copolymers with those containing N-vinyl-2-pyrrolidone and 2-vinylpyridine previously reported and other related comonomers with different chemical structure allows us to establish some reactivity structure relationship and a generalization for these systems. The monomer reactivity ratios r(1) and r(2) (MRR) were estimated by using the classical linear fitting procedures and also through a computer program based on a nonlinear minimization algorithm, starting from the r(1) and r(2) values obtained by the former procedures.