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Macromolecules, 2014, 47 (14), pp 4538–4547.
Sébastien Georges †‡§∥, Ahmed Osmane Touré †‡§∥, Marc Visseaux †‡§∥, Philippe Zinck†‡§∥*
† Université Lille Nord de France, F-59000 Lille, France and
‡ ENSCL, UCCS, CCM, F-59652 Villeneuve d’Ascq, France and
§USTL, UCCS, CCM, F-59655 Villeneuve d’Ascq,France and
∥ CNRS, UMR8181, F-59652 Villeneuve d’Ascq, France.
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.
Copyright © 2014 American Chemical Society.
Additional information
The properties of polymers and copolymers are strongly related to their composition and microstructure. Tuning the composition and microstructure of copolymers is usually realized by changing the catalyst metal or ligands, or by changing the feed (initial ratio of the comonomers in the reactive medium). Feeds with large excess of one of the monomer lead to a loss of a substantial part of the less reactive monomer when isolating the copolymer, while catalyst synthesis is often long, tedious, time and money consuming. We provide in this study a simple tool which enables to control both the composition and the microstructure of biobased rubbers precursors and styrene/diene copolymers, while providing at the same time catalyst economy. Coordinative Chain Transfer Polymerization (CCTP) involves the use of a single transition metal based catalyst combined with chain transfer agent in the form of main group metal alkyls. The growing macromolecular chain is able to transfer from the catalyst to the chain transfer agent, enabling the growth of several chains per transition metal. By changing the amount and nature of the chain transfer agents, one can easily play on the regioselectivity and resulting microstructure in the course of the polymerization of conjugated dienes and on the rate of insertion of comonomers in the course of statistical copolymerizations. The Coordinative Chain Transfer CoPolymerization and TerPolymerization of isoprene, myrcene and styrene is a particularly nice example of such features.
