Preparation of Poly(serine ester)s by Ring-opening Polymerization of N-Trityl Serine Lactone Under Catalysis of ZnEt2

Poly(N-trityl serine lactone)(PTSL) and mPEG-block-poly(N-trityl serine lactone)(mPEG-b-PTSL, PEG=polyethylene glycol) were synthesized via the ring-opening polymerization of N-trityl serine lactone(TSL) with diethyl zinc(ZnEt₂) as catalyst. The structures of these polymers were confirmed with hydrogen nuclear magnetic resonance(¹H NMR) spectroscopy, carbon nuclear magnetic resonance(¹³C NMR) spectroscopy and infrared(IR) spectrometer. The thermal decomposition temperature and glass transition temperature of PTSL were 241 and 161 ℃, respectively. A series of mPEG-b-PTSL with different molecular weights(M_n's from 7000 to 32000) was obtained by tuning the TSL/mPEG feed ratio. After the removal of the trityl groups, mPEG-block-poly(serine lactone)(mPEG- b-PSL) was obtained as a new kind of cationic block copolymer. Low cytotoxicity of these polymers to L929 cells was confirmed via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay.