Blendas de polipirrol e poli(cloreto de vinila) : propriedades termicas, mecanicas e eletroquimicas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

Blends including an intrinsically conductive polymer, polypyrrole or polythiophene, and an insulating polymer, PVC, were prepared. The method used was the oxidative chemical polymerization of the heterocyclic monomers, in the vapor phase, in PVC films impregnated with an oxidant agent (FeCl3). This procedure was efficient for the preparation of blends composed by a conductive and an insulating polymer. With respect to the insulating rnatrix, the incorporation of FeCI3 to PVC produces an effect similar to plasticization. This was verified by the changes in the viscoelastic properties of PVC/FeCl3 in relation to pure PVC. With ferric chIoride incorporation, the mechanical properties vary from hard and ductile to soft and tough and Tg shifts to lower temperatures. The presence of the FeCI4¨ ion, observed by UV/Visible spectroscopy, explain the changes as a result of the interaction between PVC and FeCl3. This interaction originates an ionic pair, inducing a mobility increase in the polymeric chains. Thermogravimetric analysis indicate that addition of ferric chloride does not change the thermal stability of PVC. The incorporation of PPy and PTh in the PVC matrix was confirmed by FTIR-ATR spectroscopy and the possibility for formation of "sandwich" type structures was noted. The lower reactivity of thiophene in relation to pyrrole, in the, experimental conditions used, explain the differences in properties of the blends PVC/PPy and PVC/PTh. The blending of PPy and PTh in PVC does not change the thermaI behavior of the conductive polymers. The relation between the monomers diffusion rate and polymerization rate controls the degree of incorporation and the distribution of the conductive polymer in the matrix. Monomers exposure time and initial concentration of oxidant agent influences the amount of conductive polymer incorporated, the mechanical properties and Tg. The conductivity of the PVC/PPy blends (in the range 10 a 10 S.cm), however, is independent to there variables, but is influenced by matrix thickness and temperature. We noted that there is a phase separation as a result of the low solubility between PPy and PVC. These blends, obtained by a chemical method, showed electroactivity similar to those obtained electrochemically, as a result of the redox properties of PPy. The electroactivity, however, is clearly influenced by the presence of the insulating matrix.

ASSUNTO(S)

quimica

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