N-异丙基丙烯酰胺/丙烯酸胆甾醇酯共聚物研究

STUDY ON THERMO-SENSITIVE AMPHIPHILIC COPOLYMERS FROM N-ISOPROPYLACRYLAMIDE AND CHOLESTERYL ACRYLATE

合成和表征了N 异丙基丙烯酰胺 (NIPAM)与丙烯酸胆甾醇酯 (CHA)的共聚物 .利用表面张力和荧光探针法研究了共聚物水溶液的表面活性性能 ,确定了其临界胶束浓度 (CMC) .利用浊度法和荧光探针法测定了共聚物的最低临界溶液温度 (LCST) .研究发现 ,在聚N 异丙基丙烯酰胺 (PNIPAM)分子链中引入疏水结构单元CHA会使其LCST下降 ;且随着共聚物中CHA含量的增加 ,LCST下降幅度增加 .在PNIPAM链段中引入少量的CHA就会使其表现出明显的两亲性 ,共聚物在水中能形成有壳核结构的稳定胶束 .通过将疏水化合物胆甾醇作为模拟药物包埋在胶束的疏水核中的研究 ,证实所得的胶束能包埋疏水药物 ,且随着包埋胆甾醇含量的增加 ,胶束平均粒径增大 .

The copolymers of N-isopropylacrylamide (NIPAM) and cholesteryl acrylate (CHA) in different molar ratios were synthesized and characterized. The surface activity and micellar behavior of the copolymers in aqueous solution were studied by surface tension method and fluorescence probe method. The Lower Critical Solution Temperature(LCST) of the copolymers was determined by fluorescence probe and turbidity measurement method. Results showed that the incorporation of hydrophobic comonomer CHA led to a lower LCST than PNIPAM and the LCST decreased with the increase of the ratio of CHA. The copolymers in aqueous solution had obvious aggregation behavior with the increase of their concentrations. It was evident that the introduction of a small amount of CHA units into the polymer backbone could lead to a very dramatic effect on the amphiphilic properties of the copolymers. The inner core of the micelles formed by self-aggregates of CHA segments of the copolymers was observed to encapsulate hydrophobic compounds, such as cholesterol (a drug model). With the increase of cholesterol amount in the sample solutions with the same polymeric concentrations, the average size of the formed micelles shifted to a larger value, which indicated that more cholesterol molecules were encapsulated in the micelles.