Dual cooperative organocatalysts for one-pot synthesis of polyester-polythiocarbonate block copolymers from multiple mon
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al cooperative organocatalysts for one-pot synthesis of polyesterpolythiocarbonate block copolymers from multiple monomers Cheng-Jian Zhang, Xun Zhang & Xing-Hong Zhang
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Key Laboratory of Macromolecular Synthesis and Functionalization, Ministry of Education, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China Received June 1, 2020; accepted July 7, 2020; published online August 26, 2020
The sequential arrangement of multiple monomer units in a polymer chain remains a major challenge in synthetic chemistry. Here we describe a versatile route to the novel polyester-polythiocarbonate block copolymer from commercially available lactones, epoxides, and carbonyl sulfide (COS). A bicomponent organocatalyst combining triazabicyclodecene (TBD) with triethyl borane (TEB) generates two types of tunable active sites, i.e., TBD-capped alcohol via hydrogen bond and TEB-capped alcohol via O→B coordination bond, which can successively catalyze ring-opening polymerization of lactones and ring-opening copolymerization of COS and epoxides from mixed monomers in one pot. Because of the reversible activated propagating anions and fast activity exchange between the active and dormant species, all of the polymer chains are enchained with both polyester and polythiocarbonate blocks. Kinetic determination quantitatively confirms the proposed mechanism. This method enables diverse lactones and epoxides to form sulfur-containing block copolymers with readily tunable structures. block copolymer, polyester, polythiocarbonate, organocatalysis, polymer synthesis Citation:
Zhang CJ, Zhang X, Zhang XH. Dual cooperative organocatalysts for one-pot synthesis of polyester-polythiocarbonate block copolymers from multiple monomers. Sci China Chem, 2020, 63, https://doi.org/10.1007/s11426-020-9816-4
1 Introduction In comparison with natural macromolecules [1], the synthetic polymers seldom have the same fidelity in the sequential arrangement of monomer units in polymer chains, especially when multiple monomers are involved [2]. Block copolymers represent a primary level of sequence-controlled polymers, which are constructed by connecting discrete linear chains incorporating dozens to hundreds of identical repeating units [3,4] and have been used in membrane fabrication [5], lithography [6], and drug delivery [7]. Of special, block copolymers comprising aliphatic ester and carbonate linkages are appealing biocompatible and biodegradable materials [8–12]. Synthetic polymer chemistry has made many useful strategies to enable the covalent connec*Corresponding author (email: [email protected])
tion of polyester and polycarbonate blocks [13–18]. Coates and co-workers [19] reported the one-step route to estercarbonate diblock via rate-determined ring-opening copolymerization (ROCOP) of epoxides with cyclic anhydrides and carbon dioxide (CO2) by using a (bdi)ZnOAc catalyst. Darensbourg et al. [20,21] reported the tandem catalysis method whereby a (salen)Co(III)X catalyst and an organic base of 1,8-diazabicyclo[5.4.0]
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