Depolymerisation of polyisoprene by olefin cross-metathesis at equilibrium

Abstract

Chemical valorisation of polymers gained a massive interest in the recent years, as it represents a more sustainable approach for the management of plastic waste. In particular, depolymerisation of polydienes by olefin cross metathesis is a powerful strategy to access telechelic oligomers with a variety of end groups. Despite the multiplication of investigations aimed at developing new materials from these oligomers, there has been little interest in the prediction of their molecular weight after depolymerisation, even though it represents a major parameter influencing macromolecular properties; in fact, most studies only rely on a kinetic approach to obtain a targeted molar mass. Here, we demonstrate that the equilibrium molecular weight of the oligodienes can be calculated from the amount of chain-transfer agent incorporated in the polymer. Equilibrium was achieved by performing several additions of catalyst, and the molar mass could be predicted from a simple statistical model. While we could not predict the conversion of chain-transfer agent beforehand, this statistical approach still provides an easy tool to establish the degree of polymerization of the products and, hence, have a better control over the final materials properties.