Ring-Opening Polymerization of a Benzyl-Protected Cyclic Ester towards Functional Aliphatic Polyester(dagger)

Comprehensive Summary Monomer design strategy has become a powerful tool to access polymers with desired and diverse functionalities. Here, we designed a novel monomer 2-((benzyloxy)methyl)-1,4-oxathiepan-7-one (BTO) via installing a benzyl ether side chain to the structure of 1,4-oxathiepan-7-one (OTO). The ring-opening polymerization of BTO with Zn1 as the catalyst demonstrated the characteristics of living polymerization with turnover frequency (TOF) up to 2520 h(-1). With a [BTO](0)/[Zn1](0)/[I](0) feed ratio of 2000/2/1, polymer with high number-average molecular weight (M-n = 536 kDa) and narrow dispersity ( = 1.06) was obtained. The produced polymer with a glass transition temperature of -17 degrees C behaved as an elastomer at room temperature. Consequently, the monomer BTO was copolymerized with (L)-LA to modulate the mechanical properties of P((L)-LA). When the BTO content is 10%, the copolymer exhibits excellent strength (24 MPa) and elongation at break (270%), affording a crystalline, hard, and tough plastic material that combines the high ductility of P(BTO) and the high modulus of P((L)-LA). In addition, the oxidation of P(BTO) to P(BTO)-SO2 led to an improvement of T-g from -17 degrees C to 38 degrees C. Debenzylation of P(BTO)-SO2 afforded P(BTO)-SO2-OH containing free hydroxyl groups. Ultimately, P(BTO) could be hydrolyzed under a base condition to recover the corresponding hydroxyl acid intermediate, which could be used to prepare the monomer again and complete the closed-loop from monomer to polymer to monomer.