“一锅法”光控开环聚合原位调控聚类肽分子量及分子量分布

One-Pot Photo-Controlled Ring-Opening Polymerization towards in situ Molecular Weight and Distribution Regulation of Polypeptoids

设计和合成了光敏性休眠引发剂2-硝基-4,5-二甲氧基苄基环己胺基甲酸酯,用于氮-丁基-氮-羧酸内酸酐(^(Bu)N-NCA)的可控开环聚合。该光敏性引发剂在紫外光(360 nm)下释放环己胺引发剂。通过改变紫外光的照射时长可控制环己胺引发剂的释放量,从而调控聚类肽的分子量。随着照射时长从1 h增至4 h,聚类肽的数均分子量从9.6×10^(3)降至4.6×10^(3)。通过调控紫外光的照射间隔控制环己胺引发剂的释放速率。先释放的引发剂先引发单体,后释放的引发剂后引发单体,形成链长不均一的聚合物。通过光控实现了“一锅法”原位调控聚类肽的分子量及分子量分布,为聚类肽分子量分布宽度及分布形状更精准的调控提供了可能,也为研究聚类肽分子量分布和性能间的关系奠定了基础。

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-dimethoxybenzylcyclohexylaminecarbamate,for the ring-opening polymerization of N-butyl-N-carboxyanhydride(^(Bu)N-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 9.6×10^(3)to 4.6×10^(3)).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.