A Bifunctional β‑Diiminate Zinc Catalyst with CO2/Epoxides Copolymerization and RAFT Polymerization Capacities for Versatile Block Copolymers Construction

• Published in: Macromolecules 2018-05, Vol.51 (10), p.3640-3646
• Main Authors: Zhang, Yao-Yao, Yang, Guan-Wen, Wu, Guang-Peng
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.8b00576

Construction of block copolymers is a practical method for modifying the properties of CO2-based polycarbonates (CO2-PCs) in order to meet specific needs. Herein, we report a well-defined single-site β-diiminate zinc complex 1 equipped with the capacities of coordination copolymerization of CO2/epoxide and reversible addition–fragmentation chain transfer (RAFT) polymerization of vinyl monomers. Complex 1 is specifically designed to possess a 3-(benzylthio­carbonothioylthio)­propionate (BSTP) initiating group, which enables the controlled ring-opening copolymerization of epoxides and CO2, leaving a polycarbonate with BSTP functional group at the end of the chain. The end-capped BSTP allows direct chain extension via living RAFT polymerization, thus providing a robust method to construct various CO2-based block copolymers in one pot via a tandem catalysis strategy. The structure of 1 is established by single-crystal X-ray diffraction as well as 1H and 13C NMR. By utilizing 1, a wide range of CO2-based block copolymers including poly­(cyclohexene carbonate)-block-poly­(2-(dimethyl­amino)­ethyl methacrylate) (PCHC-b-PDMAEMA), poly­(cyclohexene carbonate)-block-polystyrene (PCHC-b-PS), and poly­(cyclohexene carbonate)-block-poly­(N-isopropyl­acrylamide) (PCHC-b-PNIPAM) with controlled molecular weight and compositions are prepared. These block copolymers are fully characterized by DSC, 1H NMR, and 13C NMR spectroscopy. Especially, a thermoresponsive PCHC-b-PNIPAM copolymer is for the first time synthesized as a functional nanomaterial. The complex and catalytic process provided here offers a straightforward catalytic access to CO2-based block copolymers.