支化侧链偶氮无规共聚物中空和类囊泡聚集体研究

研究了支化侧链型偶氮无规共聚物(PMAPB6P-AA)在THF/H2O混合溶液中的自组装行为.研究发现,通过缓慢增加体系的水含量,可以制备出具有中空结构的非球形聚集体.调节聚合物的初始浓度,可以得到不同粒径的聚集体.聚集体中偶氮生色团的光致异构化速率与异构化程度随聚合物初始浓度的增大而减小.在此基础上,采用更加缓慢的增加水含量的方法,使聚合物分子进行充分的疏水聚集与H-聚集,制备出类囊泡状聚集体.在紫外光照射条件下,观察到类囊泡聚集体发生了光致解聚集.

HOLLOW AND VESICLE-LIKE AGGREGATES OF AN AMPHIPHILIC AZO RANDOM COPOLYMER BEARING BRANCHED AZOBENZENE SIDE CHAINS

The self-assembly and photoresponsive properties of an amphiphilic azo random copolymer bearing branched azobenzene side chains(PMAPB6P-AA) are reported.The aggregates of PMAPB6P-AA in THF/H2O dispersion were obtained by slowly adding deionized water into a THF solution of the polymer to the water content of 80 vol%.Instead of quenching the aggregates with excess water to form solid colloidal spheres,the dispersion was diluted with a THF/H2O mixture(THF/H2O=1/4,V/V) and then THF in the medium was slowly removed through evaporation.The procedure could generate a series of hollow-structured aggregates with different sizes simply by adjusting the preparation conditions.The hollow aggregates were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM) and dynamic light scattering(DLS).Photoisomerization behavior of the azobenzene units was studied to detect the local environment surrounding the molecular probes in the hollow aggregates.Results showed that hollow aggregates possessed the non-spherical morphology at relatively high increasing rate of water content.The size(hydrodynamic diameter) of the hollow aggregates was determined by the polymer initial concentration in THF.The photoinduced isomerization rate and the photoisomerization degree of the hollow aggregates decreased with the increase of polymer initial concentration in THF.The vesicle-like aggregates with a thin shell were formed by diluting the polymer disperse at 23 vol% water content with THF/ H2O(THF/H2O=10/3,V/V) and slowly removing THF through evaporation.For the vesicle-like aggregates,photoinduced disaggregation was observed when irradiated with the 365 nm UV light.The understanding obtained from this study can be used to develop new functional materials from photoresponsive random copolymers.