Synthesis of Telechelic 1,4-Polybutadiene by Metathesis Reactions and Borane Monomers

This paper describes a novel method for preparing telechelic 1,4-polybutadiene polymers which have functional groups, such as hydroxy and iodo groups, located at both ends of the polymer chains. The chemistry is based on borane-terminated 1,4-polybutadiene intermediates, in which the borane groups can be quantitatively converted to other functional groups under mild reaction conditions. The preparation of borane-terminated 1,4-polybutadiene involves two metathesis reactions, one being ring-opening metathesis polymerization of 1,5-cycooctadiene in conjunction with a borane monomer as the chain-transfer agent, the other involving the metathesis degradation of 1,4-polybutadine with the simultaneous functionalization of the broken chain end by borane monomer. Due to the good stability of borane moieties to transition-metal catalysts and good solubility of borane-containing polymers in hydrocarbon solution, both metathesis reactions are very effective in providing telechelic polymers with not only a high degree of functionalization but also controllable molecular weight.