含芳香侧链聚类肽的合成与自组装

Synthesis and Self-assembly of Polypeptoids with Aromatic Side Chains

设计合成了一种侧链含有溴苯基团的新型N-取代-N-硫代环内羧酸酐(NNTA)单体,即N-4-溴苯基甘氨酸-N-硫代环内羧酸酐(NBrG-NTA).以聚乙二醇胺作为大分子引发剂,乙酸作为促进剂,实现了NBrG-NTA在DMAc中的可控开环聚合,以较高的产率(>80%)制备得到了不同嵌段长度的两嵌段共聚物聚(乙二醇)-b-聚(N-4-溴苄基甘氨酸)(PEG-b-PNBrG).体积排除色谱(SEC)测试表明产物具有较窄的分子量分布(Đ<1.06).示差扫描量热法(DSC)测试表明PNBrG嵌段具有良好的结晶性.系统研究了PEG-b-PNBrG在醇类溶剂中的自组装行为,利用透射电子显微镜(TEM)对组装体的形貌进行了详细表征,根据不同的退火温度和保温时间,获得了“竹叶”状、“海胆”状和“蒲公英”状等形貌的组装体.

The solution self-assembly of crystalline polypeptoids to form hierarchical nanostructures with tailorable morphologies and functionalities has attracted increasing attention.While,the common crystalline polypeptoids obtained by ring-opening polymerizations(ROPs)are mainly with linear alkyl side chains.The self assemblies of crystalline polypeptoids with aromatic side chains are rarely reported.In this study,a novel N-substitutedN-thiocarboxyanhydride(NNTA)monomer with bromophenyl side group was designed and synthesized,namely N-4-bromobenzylglycine-N-thiocarboxycanhydride(NBrG-NTA).Using poly(ethylene glycol)amine as macroinitiator and acetic acid as a promoter,the controlled ROPs of NBrG-NTA in DMAc were achieved,which produced diblock copolymers poly(ethylene glycol)-b-poly(N-4-bromobenzylglycine)(PEG-b-PNBrG).The structures of the diblock copolymers were confirmed by 1H-NMR and FTIR spectra.By adjusting monomer to initiator feed molar ratios,PEG_(44)-b-PNBrG_(7) and PEG_(44)-b-PNBrG_(12) were prepared with high yields(>80%)and narrow molecular weight distributions(Đ<1.06).The chain lengths of PNBrG blocks were closed to the feed molar ratios,which showed the good controllability of the polymerizations.DSC measurements showed that PNBrG chains of both homopolymers and block copolymers had a good crystallinity.Therefore,crystallization and solvophobic interaction-driven self-assembly of PEG-b-PNBrG in alcoholic solvents was systematically studied,and the morphologies of the assemblies were characterized by TEM.After annealing in n-butanol at 100℃for 4 h,PEG_(44)-b-PNBrG_(7) was adequately dissolved,and“bamboo leaf”-like assemblies were formed after incubated at 25℃for 2 h,and the size of the assemblies increased when the incubation time prolonged to 12 h.When the annealing time in n-butanol was cut down to 2 h,irregular spherical micelles were obtained at first due to the inadequate dissolution of partial PEG_(44)-b-PNBrG_(7) chains,while the fully dissolved chains assembled to spindly nano-sheets,and finally nano-sheets aggregated around the irregular spherical micelles to form“sea urchin”-like assemblies.To the case of PEG_(44)-b-PNBrG_(12),after annealing in n-octanol at 140℃for 4 h,it assembled to“dandelion”-like nanoparticles with similar formation processes to the“sea urchin”-like assemblies.