Telechelic oligomers obtained by metathetic degradation of both polyisoprene and styrene-butadiene rubbers. Applications for recycling waste tyre rubber

Metathetic degradation of synthetic cis-1,4-polyisoprene (PI) and styrene-butadiene copolymer (SBR) was performed with cis-1,4-diacetoxy-2-butene (DAB) as chain transfer agent (CTA) using Grubbs II catalyst. Well-defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a wide range of targeted average molecular weights from 350 g mol−1 to 98,000 g mol−1, with a polydispersity index of around 2. Starting from SBR, a similar structure control was obtained with a range of Mn from 1400 g mol−1 to 65,000 g mol−1. It was found that precise selection of catalyst concentration and solvent is the major factor to obtain targeted products with high Mn control. Moreover, preliminary tests using such a procedure have shown its efficiency starting from waste tyre. This methodology thus suggests the possibility to recycle such rubber waste leading to high value liquid rubber.