Cinetica de foto e termoisomerização de azocompostos em matrizes polimericas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

In this work we had been studied the photo and thermal isomerization processes of the azo dyes (4-Dimethyl aminoazobenzene (DAB); [4-(N-(2-hidroxiethyl)-N-ethyl)-4 -nitroazobenzene] (DR1); [4-(N-(2-hidroxiethyl)-N-ethyl)-2 -chlore-4 nitroazobenzene] (DR13)) searching to make correlation with rate constants and the viscosity of the polymeric solutions, the effect of the matrix, the effect of the annealing the polymeric films and the effect of the polarity matrix. Two forms of incorporate of the azo dyes had been studied: doped and funcionalized systems. The kinetic curves had been gotten by the accompaniment of spectral changes associates to the syn/anti isomerization process being these data fitted with mono-exponential, exponential streched and bi-exponential functions. The viscosity effect was evaluated by the accompaniment of the kinetic behavior of photochromatic dyes dissolved in solutions of polystyrene in toluene (PS/toluene). The results shows that conversions obey the linear relation foreseen for Arrhenius for unimoleculars reactions and the effect of the viscosity at the rate constants was explained by the modified theory of the state of transition (TST). In PS films, the kinectic can be well-described by bi-exponential functions and the diference observed in kinetics behaviours of DAB dye in films gotten by scattering solutions and by centrifuge deposition had been explained on the basis of diferent leveI of order in the system. Diference observed in kinetic behaviours in films annealed had been explained by the different free volumes distributions and its fluctuations. The effect of the polarity matrix studied in functionalized polymers of the DR13 dye linked in: polystyrene (PS-DR13), poly(methyl acrylate) (PMA-DR13) and random copolymers of poly(styrene-comethyl acrylate) (PS-PMA-DR13) shows that the rate constants at the photo and thermal isomerization growing up with the polarity matrix and it was explained by the stabilization of the trasition state with the increase the polarity matrix.

ASSUNTO(S)

cinetica azocompostos fotoisomerização

ACESSO AO ARTIGO

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