Regioselective Chain Shuttling Polymerization of Isoprene: An Approach To Access New Materials from Single Monomer
作者:Bo Liu and Dongmei Cui
关键字:Chain shuttling polymerization; chain transfer; random copolymers; regioselective; architecture controlle

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.