Synthesis and properties investigation of hydroxyl functionalized polyisoprene prepared by cobalt catalyzed co-polymerization of isoprene and hydroxylmyrcene

Abstract

The intrinsic hydrophobicity of rubber matrices renders compatibility with polar fillers rather difficult in most cases. In this manuscript, a cobalt complex supported by a 2-oxazoline-pyridine ligand armed with a labile 6-(di-tert-butyl-phosphine oxide) moiety is prepared and characterized. In combination with excess AlEt₂Cl, the precursor actively copolymerizes isoprene with the bio-sourced myrcene derivative 2-methyl-6-methyleneoct-7-en-3-ol with adjustable comonomer incorporation from 4.4 mol% to 31.5 mol%. The presence of hydroxyl functionalized polyisoprene was characterized by using Fourier transform infrared spectroscopy, ¹H/¹³C NMR, and validated by the improved hydrophilicity, elevated glass transition temperature and microphase separation observed by AFM. Up to 30 wt% SiO₂ loading can be individually dispersed in the 4.4 mol% hydroxyl functionalized polyisoprene copolymer with substantially reduced aggregation. The improved filler–polymer interfacial interactions via “hydrogen bonds” offer not only effective improvement of the tensile strength (9.6 ± 0.2 MPa), but an unusual stretchability of over 885.3 ± 2.0% and improved hysteresis loss with respect to pristine polyisoprene/SiO₂ vulcanizates.