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A semicrystalline poly(trimethylene monothiocarbonate) (PTMMTC) has been synthesized via the selective and alternating copolymerization of carbonyl sulfide and oxetane. This reaction was catalyzed by (salen)CrCl accompanied by organic bases over a wide range of temperatures from 40 to 130 °C. PTMMTC is shown to exhibit similar crystallization behavior to high-density polyethylene (HDPE), i.e., being spherulite and possessing melting temperatures (Tm) up to 127.5 °C and a degree of crystallinity (Xc) of up to 71%. Moreover, PTMMTC has a wide processing temperature window of ca. 100 °C. [ABSTRACT FROM AUTHOR]

Polyester synthesis from the alternating copolymerization of epoxides with cyclic anhydrides via a metal-free route remains a key challenge. This work reports the development of a highly active organocatalytic route for the copolymerization of a spectrum of epoxides and cyclic anhydrides. Fully alternating polyesters were synthesized by a variety of organic Lewis acid-base pairs including organoboranes and quaternary onium salts. The effect of the acidity, type, and size of Lewis pairs on the catalytic activity and selectivity of the copolymerization is presented. The undesirable transesterification and etherification were effectively suppressed even in the case of complete conversion of the cyclic anhydride. This could be ascribed to the formation of a unique tetracoordinate bond-carboxylate (or alkoxide) anion. The Lewis pairs are highly active, with a turnover frequency of 102 and 303 h-1 for the copolymerization of propylene oxide with maleic anhydride and phthalic anhydride, respectively, at 80 °C. Block polyester with narrow polydispersity of 1.05 was achieved via a sequential addition strategy. This work provides robust organocatalysts for the selective copolymerization of epoxides with cyclic anhydrides. [ABSTRACT FROM AUTHOR]