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 T_g values. This work provides a new strategy to access stereoregular and architecture controlled polymers from a single monomer.