Etude de la dégradation thermique du poly{acétoxy‐1 [(chloro‐2 éthyl)‐4 phényl]‐1 éthylène}

Abstract

A kinetic study of the thermal decomposition of poly(1 -acetoxy-l-[4-(2-~hloroethyl)phenyl]ethylene) (1) was carried out by thermogravimetry. Two stages, well separated, are observed. The first one begins at 140°C. The corresponding decomposition reaction is a superposition of two reactions: loss of acetic acid and partial depolymerization. The main volatile products released in this first stage, identified by gas chromatography/mass spectrometry coupling, are chiefly acetic acid and a small quantity of p-(2-~hloroethyl)acetophenone; there is no monomer from the monomeric unit. As in case of other poly(para-substituted a-acetoxystyrenes) the solid residue is polyIp-(2-chloroethyl)phenylacetylene)] (5) of low molar mass, soluble in all usual organic solvents. No auto-catalytic mechanism was found during this first stage, unlike in case of poly(viny1 acetate). The reaction order is one, over a wide range of conversion. The activation energy was found to be about 145,6 kJ/mol and the pre-exponential factor 1,6. l O I 5 min-I. An explanation for the insolubility of the residues, obtained by thermal degradation of some poly@-chloroalkylstyrenes), is proposed. 4 solubles de faibles masses molaires et laisse Cchapper de l'acide et de l'anhydride acetique, du monomere et/ou de l'acetophenone correspondante.Pour les seconds, la decomposition thermique conduit a des produits reticules insolubles oh il n'y a plus de chlore, et laisse Cchapper essentiellement du chlorure d'hydrogene et du monomere. Dans la serie des polymeres 3, nous avons constate qu'avant toute degradation, ces produits sont deja peu ou pas solubles dans les solvants organiques usuels. En particulier, le polymkre 3 b est totalement insoluble. Cette insolubilitC peut Ctre attribuee a des reactions de pontage interchaine au niveau du chlore et des carbones tertiaires de la chaine principale. 0 1991, Hiithig & Wepf Verlag, Basel CCC 0025-1 16X/91/$05.00