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Indexed by:期刊论文

Date of Publication:2016-04-26

Journal:MACROMOLECULES

Included Journals:SCIE、EI

Volume:49

Issue:8

Page Number:2971-2976

ISSN No.:0024-9297

Abstract:Carbonyl sulfide (COS) as a carbon source for copolymerization with epoxides has recently received some attention. The introduction of sulfur atom can provide enhancement of important polymer properties compared to the corresponding copolymer from CO2. However, the synthesized copolymers are all amorphous, therefore hindering them to be used as structural materials. Herein, we report the synthesis and characterization of semicrystalline poly(thiocarbonate)s derived from enantiopure epichlorohydrin and COS employing the single-site bifunctional catalyst. The catalyst shows excellent regioselectivity for epichlorohydrin ring-opening at methylene carbon. The copolymerization mechanism has been studied by means of NMR and ESI-MS methods. It is found the reaction temperature plays an important role in the crystallization behavior of the resultant copolymers. That is, at ambient temperature the propagating monothiocarboxylate species favors the nucleophilic attack at the chloromethylene of epichlorohydrin to form an epoxy ring end group, along with the release of chloride ion as a new initiator. This chain termination results in low molecular weight and board distributed copolymers, in accordance with the amorphousness. Alternatively, at reduced temperature such as -25 degrees C, the monothiocarboxylate species prefers consecutive alternating enchainment of COS and epichlorohydrin to give copolymers with enhanced molecular weights. Of importance, the formed polymer is a typical semicrystalline thermoplastic, possessing a T-g of 15.6 degrees C and a T-m of 96.7 degrees C.