偶氮聚电解质的H-聚集和光响应行为

用偶氮聚电解质上的偶氮苯基团作为“探针” ,研究了侧链偶氮聚电解质聚 {丙烯酸 2 [4 (4′ 乙氧基苯基偶氮 )苯氧基 ]乙酯 co 丙烯酸 }(PEAPE)在水中的H 聚集及其对光响应性的影响 .研究发现 ,与在DMF溶液的紫外吸收光谱相比 ,偶氮聚电解质在水中的紫外吸收λmax 发生明显蓝移 ,表明在水溶液中偶氮生色团形成了H 聚集体 .溶解在DMF H2 O混合溶剂中的上述偶氮聚电解质也存在部分H 聚集 ,H 聚集程度与水和DMF的比例有关 .H 聚集体的形成使光异构化速率明显减慢 ,异构化效率显著降低 .同时 ,其光异构化动力学不符合一级指数衰减规律 ,说明该过程同时包含‘孤立的’偶氮生色团的光异构化反应和H 聚集体的光致解聚集

H-AGGREGATION AND PHOTO-RESPONSIVE BEHAVIOR OF AN AZO POLYELECTROLYTE

By using spectroscopic characteristics of azo chromophores in different states as a ‘probe',H-aggregation of the azo chromospheres of a polyelectrolyte poly{2-[4-(4′-ethoxyphenylazo)phenoxy]ethyl acrylate-co-acrylic acid｝(PEAPE) aqueous solutions and its effect on photo-responsive behavior were studied.Compared with the azo polyelectrolytes in DMF,PEAPE in H 2O showed an obvious blue-shift of the maximum absorbance due to H-aggregation of the azo chromophores formed in the solution.There also exists H-aggregation of the azo chromospheres in PEAPE solution in DMF/H 2O,and the degree of H-aggregation depends on the ratio of DMF and H 2O.The UV-Vis spectra of PEAPE aqueous solution change with different degrees of functionalization of the azo chromophores.With the degree of functionalization increase,the λ max of PEAPE gradually blue shifts,which suggests the degree of H-aggregation increase.H-Aggregation of the azo chromospheres results in a slower photo-isomerization rate and lower photo-isomerization efficiency of the azo polyelectrolyte PEAPE.The photo-isomerization kinetics of the PEAPE aqueous solution doesn't obey the first order exponential decay function,which also indicates that the coexistence of H-aggregates and “isolated” azo chromospheres in the system.