表面张力法研究温敏性接枝共聚物的微胶束化行为

用表面张力法研究了以水溶性可生物降解的葡聚糖为主链 ,具有温敏相变特性的聚 (N 异丙基丙烯酰胺 )为接枝链的葡聚糖 接枝 聚 (N 异丙基丙烯酰胺 ) (Dextran g PNIPAM)共聚物在水溶液中的胶束化行为 .研究结果表明Dextran g PNIPAM体系的微胶束化行为与共聚物结构和溶液体系的温度密切相关 ,接枝共聚物中PNIPAM含量越大 ,水溶液体系的温度越高 ,形成胶束的临界胶束浓度 (CMC)越小 .特别值得指出的是 ,无论水溶液的温度是否高于PNIPAM接枝链段的相变温度 (LCST) ,即PNIPAM链段由亲水性转变为疏水性的温度 ,Dextran g PNIPAM均呈现一个临界胶束浓度大 ,对该现象给予了解释 .

MICELLIZATION STUDIES OF THERMO-SENSITIVE GRAFT COPOLYMERS IN AQUEOUS SOLUTIONS BY MEANS OF SURFACE TENSION MEASUREMENTS

The micellization of thermo-responsive dextran-g-PNIPAM copolymers in aqueous solutions was studied by means of surface tension technique.The surface tension of the aqueous solutions of the graft copolymers was determined over the concentration range of 0.0001 wt% to 0.5 wt% at two temperatures (15 and 37℃).It was found that the absorption of the graft polymers at the air/water interface behaved in a dynamic way.The critical micellization concentration (CMC) of the copolymers was determined from curves of the surface tension versus lg concentration.The micellization behavior depended closely on the grafting of the copolymers and the aqueous solution temperature.Micelles could be formed in the lower concentrations when increasing PNIPAM contents of the copolymers or raising the aqueous solution temperature.More importantly,the copolymers showed CMCs in all cases no mater whether the temperature was higher than the phase transition temperature (LCST) of the copolymers or not.An explanation was given for understanding the phenomenon