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• 57280-22-5 4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0]-octane 

Relevant academic research and scientific papers

Stereospecific CO2 copolymers from 3,5-dioxaepoxides: Crystallization and functionallization

Selective transformation of CO2 into biodegradable polycarbonates (CO2-based copolymers) by the alternating copolymerization with epoxides represents a most promising green polymerization process. Despite the tremendous progress this field has made, most of the CO2-based polycarbonates are known to be amorphous, and their low thermal resistance makes them difficult to use as structural materials. Herein, we report the selective synthesis of highly isotactic CO2 copolymers from meso-3,5-dioxaepoxides in perfectly alternating nature by the enantiopure dinuclear Co(III)-complex-mediated desymmetrization copolymerization under mild conditions. These isotactic CO2-based polycarbonates are typical semicrystalline polymers, possessing melting points (Tm) of 179-257 C, dependent on the substitute groups at 4-position of the meso-epoxides. As a model monomer of 3,5-dioxa-epoxides, 4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0] octane (CXO) was studied in detail in the asymmetric copolymerization with CO2. The isotactic CO2/CXO copolymer (PCXC) with >99% enantioselectivity possesses a high Tm of 242 C and a decomposition temperature of 320 C, while its atactic copolymer has a high Tg of up to 140 C. Moreover, the acid hydrolysis of highly isotactic PCXC was performed to provide stereoregular poly(1,2-bis(hydroxymethyl)ethylene carbonate)s (PCFC) with two hydroxyl groups in a carbonate unit, which showed a remarkable decrease of ～80 C in thermal decomposition temperature. This hydroxyl-functionalized CO2 copolymer accords with an unmet need for a readily degradable biocompatible polycarbonate and was further explored to prepare bush copolymers for biomedical and pharmaceutical applications. This approach was initially demonstrated by the hydroxyl groups appended in polycarbonate backbone of a hydroxyl-functionalized terpolymer serving as macroinitiators for direct graft polymerization via organocatalytic lactide ring-opening polymerization to give fully degradable brush polymers with polycarbonate backbones and polylactide side chains. Furthermore, enantiopure dinuclear Co(III)-complex-mediated asymmetric terpolymerization of CO2 with CXO and cyclohexene oxide (CHO) at various feed ratios was carried out in toluene solution, affording optically active terpolymers poly(CHC-co-CXC) with highly enantioselective ring-opening of the both meso-epoxides. These stereospecific terpolymers were found to be crystallizable and their crystallization capacity could be tuned by changing the feed ratio of the epoxides.