Coordinative Chain Transfer Copolymerization and Terpolymerization of Conjugated Dienes

Abstract

The coordinative chain transfer co- and ter-polymerizations of myrcene, isoprene and styrene have been achieved using Cp*La(BH4)2(THF)2 (Cp* = pentamethylcyclopentadienyl) combined with magnesium dialkyl and aluminum dialkyl. New highly stereoregular poly(myrcene-co-styrene), poly(myrcene-co-isoprene), and poly(myrcene-co-isoprene-co-styrene) copolymers have been obtained with good yields and a wide range of compositions. The concept of coordinative chain transfer polymerization (CCTP) induced control of the microstructure of statistical copolymers could be successfully extended to 1,4-conjugated dienes statistical copolymerization and terpolymerization and to a renewable monomer. In addition to significant transmetalation in the course of the polymerization, a modification of the apparent comonomers reactivity ratio was observed in the presence of a chain transfer agent. This could be combined, depending on the nature of the chain transfer agent, with either a stereospecific polymerization of both conjugated dienes or the introduction of 3,4 enchainments in the microstructure. The former 1,4-trans stereoselective homo-, co-, and terpolymerizations enable the growth of several stereoregular chains per catalyst atom, providing significant catalyst economy, at the expense of the activity however. The latter affords an easy and straightforward modification of the microstructure of conjugated dienes co- and terpolymers in terms of both composition and regioregularity. This is particularly interesting regarding long and tedious catalysts synthesis required to reach the same array of polymeric materials via a classical living approach.