Abstract
The innovation in polymer design to rival conventional polyethylene glycol(PEG)is an important ap-proach to achieving a more sustainable society.Here,cyclic PEG-like polycarbonates having high molec-ular weight(4.4-49.5 kg/mol)were enabled through zwitterionic ring-opening polymerization(ZROP)of macrocyclic carbonates(MCs)mediated by N-heterocyclic carbene(NHC).The thermodynamic behavior of polymerization depends on the ring size of monomers.During this process,the ZROP of 11-membered MC was driven by the change of enthalpy(ΔHp)which differed from the ZROP of 14-membered MC driven by the entropic change(ΔSp).Cyclic polycarbonates depicted improved thermostability(Td5％≥ 204 ℃)and higher glass transition temperatures(Tg＞-40 ℃)in comparison to their linear analogues(Td5％≤ 185 ℃,Tg～-50 ℃).In addition,the mechanism of ZROP of MC was addressed through computational study.A distinct mechanism of polymerization distinguishable from the well-known NHC-mediated ZROP of cyclic esters was revealed,where the zwitterion from nucleophilic addition to MC,i.e.tetrahedral intermediate,cannot be ring-opened probably due to the delocalization of negative charge on the carbonate group,but serves as an active center for the polymerization.In comparison to PEG,the attained polymer demon-strated comparable hydrophilic and biocompatible properties,as revealed by the results of contact angle and in vitro cytotoxicity studies,suggesting that cyclic polycarbonate hold the promise as the alternative of PEG.
基金项目
China Postdoc Council(OCPC)for the financial support of Postdoctoral International Exchange Program(YJ20210095)
国家自然科学基金(22078150)
国家重点研发计划(2021YFC2101904)
Jiangsu National Synergetic Innovation Center for Advanced Materials(SICAM)()
江苏省高等学校优势学科建设工程项目()
Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture(XTB2201)
Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)()
NETL
NSTL
万方数据