Janus超支化超分子聚合物的构筑及电化学响应性自组装行为研究

A Supramolecular Janus Hyperbranched Polymer and Its Electrochemically Responsive Self-Assembly Behavior

本工作报道了第一例具有电化学氧化还原刺激响应性的Janus超支化超分子聚合物,研究了其自组装及响应性解组装的行为.通过阴离子开环聚合和阳离子开环聚合的方法,分别合成了以β-环糊精为中心的亲水超支化聚缩水甘油醚CD-g-HPG和末端为二茂铁的疏水超支化聚(3-乙基-3-羟甲基环氧丁烷)Fc-g-HBPO.两者通过Fc/CD之间的主客体包结络合作用,构筑了两亲性Janus超支化超分子聚合物HBPO-b-HPG.该聚合物在水中可以自组装形成囊泡.通过动态光散射(DLS)跟踪、2D-NOESY和循环伏安曲线表征了CD-g-HPG和Fc-g-HBPO之间的主客体包结络合作用,通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)表征了囊泡结构.最后,研究了囊泡在电化学刺激下的解组装行为,同时也验证了囊泡在加热、加入主客体竞争分子和化学氧化下的稳定性.

Herein,we report a Janus supramolecular polymer consisting of two chemically distinct hyperbranched polymers,which is coined as Janus hyperbranched polymer(JHBP).Firstly,hydrophilic hyperbranched polyglycerol with an apex ofβ-cyclodextrin(CD-g-HPG)and hydrophobic hyperbranched poly(3-ethyl-3-oxetanemethanol)with an apex of a ferrocene(Fc-g-HBPO)were synthesized according to the anionic ring-opening multi-branching polymerization and cationic ring-opening polymerization,respectively.Then,amphiphilic supramolecular JHBP HBPO-b-HPG was constructed by adding H2O to cosolvent DMF through the special Fc/CD host-guest interactions and such an amphiphilic supramolecular polymer can further aggregated into assemblies.The formation and self-assembly process of supramolecular JHBP HBPO-b-HPG was tracked by dynamic light scattering(DLS).The results showed that when the volume percentage ratio of H2O/DMF was increased to 16%,the HBPO-b-HPG was formed with Dh of 5.6 nm,which is close to the size of the 1∶1 complex of CD-g-HPG and Fc-g-HBPO,then,with H2O/DMF ratio continuing to increase,HBPO-b-HPG rapidly aggregated into assemblies.The 2D NOESY and cyclic voltammetry(CV)curves were also used to verify the Fc/CD host-guest complexation ability.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were employed to characterize the morphology of the assemblies.The results showed that the HBPO-b-HPG self-assembled into unilamellar bilayer vesicles of around 260 nm.When NaCl was added after electrochemical oxidation,such vesicles could disassemble due to the cooperation of the transformation of Fc to oxidation state Fc+and equal potential destruction.Finally,DLS tracking proved that such vesicles showed excellent stability under the conditions of heating and adding host and guest competition molecules.