Catalytic hydrosilation of polybutadienes as a route to functional polymers

Abstract

Polybutadienes having a variety of different microstructures have been hydrosilated using HSiMe_xCl_{3 –x}, x= 0–2 in the presence of H₂[PtCl₆]. High conversions of double bonds pendant from the main chain are observed but hydrosilation also occurs on the backbone of the polymer especially if there is a high percentage of backbone double bonds. This backbone hydrosilation is accompanied by double-bond migration along the polymer backbone to give conjugated diene units within the polymer backbone. These polymers have been further functionalised by reactions with alcohols [EtOH, EtO(CH₂CH₂O)₂H, 4-hydroxybiphenyl or MeO(CH₂CH₂O)_nH (M_n= 500 or 750)] in the presence of Et₃N or by alkylation, e.g. with 2-lithiomethylpyridine or with 6-lithio-2,2′-bipyridine. Polymers containing —SiMe_x(OR)_{3 –x}x= 2 or 0, R = EtO(CH₂CH₂O)₂H or MeO(CH₂CH₂O)_nH (M_n= 500 or 750) have been shown to form polymer electrolytes, in some cases with room-temperature conductivities as high as 2.5 × 10^–5S cm^–1. Sequential hydrosilation and epoxidation reactions have been carried out to give polymers in which the pendant double bonds have been hydrosiiated and the backbone double bonds have been epoxidised.