Synthesis of Well-defined Poly(tetrahydrofuran)-b-Poly(a-amino acid)s via Cationic Ring-opening Polymerization (ROP) of Tetrahydrofuran and Nucleophilic ROP of N-thiocarboxyanhydrides

摘要

The synthesis of block copolymers of poly(tetrahydrofuran)-b-poly(α-amino acid)(PTHF-b-PAA)is challenging since it is difficult to combine the two blocks produced via different/conflicting ring-opening polymerization(ROP)mechanisms.In this contribution,the cationic ROP of THF is catalyzed by rare-earth triflate[RE(OTf)3]and terminated by 2-(t-butyloxycarbonyl-amino)ethanol(BAE).After the deprotection of t-butyloxycarbonyl(Boc)group,the chain end of PTHF is quantitatively changed to amino group which thereafter initiates the nucleophilic ROP ofα-amino acid N-thiocarboxyanhydrides(NTAs).Both polymerizations are well controlled,generating PTHF and PAA segments with designable molecular weights(MWs).PTHF-b-polylysine(PTHF-b-PLys)and PTHF-b-polysarcosine(PTHF-b-PSar)are obtained with MWs between 8.6 and 28.7 kg/mol.The above amphiphilic diblock copolymers form micelles in water.PTHF40-b-PSar32 acts as a surfactant to stabilize oil-in-water emulsions.Both segments of PTHF-b-PAA are biocompatible and promising in the biomedical application.