Pendant cyanate functional vinyl polymers and imido-phenolic-triazines thereof: synthesis and thermal properties

Maleimide-incorporated vinyl polymers, based on butyl acrylate (BuA), methy l methacrylate (MMA) and styrene (STY) with pendant phenol functions were s ynthesised by free radical copolymerization of respective monomers with N-( 4-hydroxy phenyl) maleimide. The phenol functions of the linear polymers we re transformed to the corresponding cyanato phenyl derivatives. Thermal cur ing of these polymers through the cyclotrimerization of the pendant cyanate groups led to crosslinked imido-phenolic-triazines. The thermal stabilitie s of the phenol precursors depended on the backbone structure. Presence of maleimide improved the thermal stability of BuA- and STY-based copolymers, whereas, it was detrimental for MMA-based ones. The early chain unzipping i n the case of the latter has been attributed to the steric interaction betw een the alpha-methyl group of MMA and maleimide moiety. Although the presen ce of imide and triazine groups in the crosslinked network was conducive fo r decreasing the rate of thermal degradation at higher temperatures, they t riggered an early onset of decomposition because of steric factors. The non isothermal kinetics of thermal decomposition was studied and the relevant k inetic parameters like activation energy (E) and pre-exponential factor (ii ) have been calculated for various phenol-functional precursors and the cor responding imidophenolic triazines. Although the trend in values of E with composition was not indicative of the thermal stability of the triazine-net work polymers due to the prevalence of kinetic compensation effect, the val ues served to estimate the rate constant for decomposition of various polym ers, which exhibited a direct correlation with their thermogravimetric beha viour. (C) 2000 Elsevier Science Ltd. All rights reserved.