Ring‐Opening Polymerization of a Benzyl‐Protected Cyclic Ester towards Functional Aliphatic Polyester

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 liv-ing 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(Mn=536 kDa)and narrow dispersity(D=1.06)was obtained.The produced polymer with a glass transition temperature of-17℃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 Te from-17℃to 38℃.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.