Stereo- and Temporally Controlled Coordination Polymerization Triggered by Alternating Addition of a Lewis Acid and Base

Significant progress has been made with regard to temporally controlled radical and ring‐opening polymerizations, for example, by means of chemical reagents, light, and voltage, whereas quantitative switch coordination polymerization is still challenging. Herein, we report the temporally and stereoc...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2016-09, Vol.55 (39), p.11975-11978
Main Authors: Liu, Bo, Cui, Dongmei, Tang, Tao
Format: Article
Language:English
Subjects:
Addition polymerization
Coordination
coordination polymerization
Copolymerization
Copolymers
Isoprene
Lewis acid
Lewis acids
Lewis bases
Polymerization
Polystyrene
Polystyrene resins
Pyridines
Reagents
Selectivity
sequence-controlled polymers
Styrene
Syndiotacticity
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Summary:Significant progress has been made with regard to temporally controlled radical and ring‐opening polymerizations, for example, by means of chemical reagents, light, and voltage, whereas quantitative switch coordination polymerization is still challenging. Herein, we report the temporally and stereocontrolled 3,4‐polymerization of isoprene through allosterically regulating the active metal center by alternating addition of Lewis basic pyridine to “poison” the Lewis acidic active metal species through acid–base interactions and Lewis acidic AliBu3 to release the original active species through pyridine ion. This process is quick, quantitative, and can be repeated multiple times while maintaining high 3,4‐selectivity. Moreover, this strategy is also effective for the switch copolymerization of isoprene and styrene with dual 3,4‐ and syndiotactic selectivity. Tuning the switch cycles and intervals enables the isolation of various copolymers with different distributions of 3,4‐polyisoprene and syndiotactic polystyrene sequences. Going round in circles: Temporally and stereocontrolled coordination polymerization was achieved by switching the activity of a Lewis acidic metal catalyst by alternating addition of a Lewis base and a Lewis acid. The switching process was rapid, quantitative, and could be repeated multiple times; not only the catalytic activity but also the selectivity of the polymerization were controlled.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201605038