一锅法制备pH和热敏的P(NIPAM-co-AA)高分子空心球

基于N-异丙基丙烯酰胺(NIPAM)在高于PNIPAM的相转变温度时的沉淀聚合反应,利用在成核阶段形成的非交联的核为模板,然后在核的增长阶段加入交联剂N,N′-亚甲基双丙烯酰胺(BMA)和丙烯酸(AA)使得核周围形成一层交联的P(NIPAM-co-AA)共聚物壳层,降温至相转变温度以下使得非交联的PNIPAM核解散并自发地从交联的壳层扩散出来,得到具有温度和pH敏感性的P(NIPAM-co-AA)空心球.透射电镜结果表明该微球具有中空结构.利用光散射在不同pH值和温度条件下对该空心球进行了表征,结果表明,P(NIPAM-co-AA)空心球对pH值和温度具有良好的响应能力.

SYNTHESIS OF pH-AND THERMO-SENSITIVE P(NIPAM-co-AA)HOLLOW SPHERES VIA A ONE-POT PROCESS

A novel approach to prepare pH-and thermo-sensitive hollow spheres based on a precipitation polymerization method has been demonstrated.The poly(N-isopropylacrylamide)(PNIPAM) nuclei formed in the nucleation stage played the role of non-cross-linked templates,on which cross-linked poly(N-isopropylacrylamide-co-acrylic acid)(P(NIPAM-co-AA)) shells were formed by adding a cross-linker N,N′-methylene-bisacrylamide and acrylic acid to the aqueous solution during the following nucleus-growing stage.A "self-removing" process was found to take place when the temperature of the reaction solution was reduced below the LCST,where the non-cross-linked PNIPAM nuclei spontaneously penetrated through the cross-linked shells to form the hollow spheres.The hollow structure was confirmed by TEM analysis.The zeta potential analysis indicated that,the shells of these hollow spheres contained carboxylic groups derived from the polymerized acrylic acid.These hollow spheres were characterized by light scattering analysis at various pH and temperatures.The results indicated that these hollow spheres could well respond to the change of pH and temperatures.As the pH increased from 2 to 7,the volume of the hollow spheres with 4.76% and 9.09% AA contents increased by about 12 and 18 times,respectively.As the temperature increased from 25℃ to 40℃,the volume of the hollow spheres with 4.76% AA content decreased by about 12 times.