Thermal stability of ethylene copolymers with multi-alkenylsilsesquioxane comonomers synthesized by organometallic catalyst - Effect of copolymer structure

Abstract

This study was focused on thermal properties of ethylene copolymers with di-, tri- and tetra-alkenylsilsesquioxanes (POSS) synthesized by ansa-metallocene complex. Ethylene copolymers with multi-alkenyl POSS were characterized by different thermal behavior depending on the kind of POSS comonomer and its content, as well as the copolymer structure. The copolymers differed in the incorporation way of POSS into the polymer chain (linear and crosslinked structure), content of specific unsaturation groups, molecular weight, as well as heterogeneity of polymer chain compositions. It was found that the kind and content of unsaturation groups in E/POSS copolymers played a significant role in the thermal stability of the obtained hybrid materials determined in non-isothermal conditions. Thus, linear copolymers showed higher thermal stability in comparison with neat polyethylene and crosslinked copolymers.Thermal stability of copolymers under iso-thermal conditions (1500 h heating at 100 °C) of polymeric products was primarily determined by the kind and content of silicon-oxygen POSS cage incorporated into the polymer chain. Incorporation of alkenylsilsesquioxane with completely condensed POSS cage into the polymer chain caused significant improvement of thermal stability, even in case of crosslinked copolymers, in contrast to comonomers with incompletely condensed silicon-oxygen POSS cage.