Regioselective Chain Shuttling Polymerization of Isoprene: An Approach To Access New Materials from Single Monomer
writer：Lei Li, Shihui Li and Dongmei Cui
keywords：Chain shuttling polymerization; chain transfer; random copolymers; regioselective; architecture controlle
source：期刊
specific source：http://pubs.acs.org/doi/pdf/10.1021/acs.macromol.6b00904
Issue time：2016年
Chain
shuttling polymerization (CSP) has exhibited unique privilege to combine monomer
sequences of different properties into one macromolecular chain, which,
however, is difficult to achieve because of low chain transfer efficiency and
thus lead to poor architecture control over the resulting polymers. Herein, we
reported that the pyridyl–methylene fluorenyl scandium complex 1 in
combination with [Ph3C][B(C6F5)4]
and AliBu3 showed a high transfer efficiency
(93.8%) in the presence of 10 equiv of AliBu3 toward
the chain-transfer polymerization (CTP) of isoprene (IP) in high
1,4-selectivity (83%). Meanwhile, under the same conditions, the analogous
lutetium precursor 3 based system was 3,4-regioselective and
exhibited almost perfect chain transfer efficiency (96.5–100%) in a wide range
of AliBu3-to-Lu ratios from 10:1 to 100:1,
indicating that each Lu generated apparently 100 polyisoprene (PIP)
macromolecules. Both CTPs performed fluently without compromising the
selectivity and the activity and had comparable chain transfer rate constants.
Based on this, 1,4- and 3,4-regioselective CSPs were realized by mixing 1 and 3 in
various ratios to give a series of PIPs bearing different distribution of 1,4-
and 3,4-PIP sequences and Tg values. This work
provides a new strategy to access stereoregular and architecture controlled
polymers from a single monomer.
