Molecular weight distribution (MWD)is a key characterization parameter of polymers and has crucial impact on the properties of polymers. The MWD regulation of polypeptoids,an attractive class of biomaterials,has not been reported so far. This study designed and synthesized the photolabile dormant initiator,2-nitro-4,5-dimethoxybenzylcyclohexy-laminecarbamate,for the ring-opening polymerization of N-butyl-N-carboxyanhydride (BuN-NCA). Upon the ultraviolet (UV) light irradiation (360 nm),the photolabile dormant initiator could release the active cyclohexylamine. The release amount was well controlled by manipulating the duration of the applied radiation. The release amount of cyclohexylamine was increased as the time of UV irradiation increased from 1 h to 4 h,resulting in the Mn decrease of the polypeptoid (from 9.6×103 to 4.6×103). The release rate of cyclohexylamine was controlled by the intervals of the applied UV irradiation. The early released cyclohexylamine initiated the monomer to form longer chains while the lately released cyclohexylamine initiated the monomer to form shorter chains. Thus,the MWDs of polypeptoids were well regulated in situ. This study provides the possibility to tune the Mn and MWD of polypeptoids in a more precise manner,and also lays the foundation for the investigation of the relationship between the MWD and the properties of polypeptoids.
关键词
光敏性引发剂/聚类肽/分子量分布调控/开环聚合/氮-取代-氮-羧酸内酸酐
Key words
photosensitive initiator/polypeptoid/regulation of molecular weight distribution/ring-opening polymerization/N-substituted-N-carboxyanhydride
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