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 <b>1</b> in combination with [Ph<sub>3</sub>C][B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] and Al<sup><i>i</i></sup>Bu<sub>3</sub> showed a high transfer efficiency
(93.8%) in the presence of 10 equiv of Al<sup><i>i</i></sup>Bu<sub>3</sub> toward the chain-transfer polymerization (CTP) of
isoprene (IP) in high 1,4-selectivity (83%). Meanwhile, under the
same conditions, the analogous lutetium precursor <b>3</b> based
system was 3,4-regioselective and exhibited almost perfect chain transfer
efficiency (96.5–100%) in a wide range of Al<sup><i>i</i></sup>Bu<sub>3</sub>-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 <b>1</b> and <b>3</b> in various ratios to give a series of
PIPs bearing different distribution of 1,4- and 3,4-PIP sequences
and <i>T</i><sub>g</sub> values. This work provides a new
strategy to access stereoregular and architecture controlled polymers
from a single monomer
