PAm-g-PMAA亲水性聚合物微球的合成

SYNTHESIS OF HYDROPHILIC POLY(METHYLACRYLIC ACID) GRAFTEDPOLYACRYLAMIDE MICROSPHERES

利用链转移自由基聚合和端基置换反应法 ,合成了苯乙烯基单封端的聚甲基丙烯酸叔丁酯 (PBMA)大分子单体 .在N ,N′ 亚甲基二丙烯酰胺 (Bis A)存在的条件下 ,使PBMA大分子单体与亲水性单体丙烯酰胺(Am)在乙醇 水的混合介质中进行分散共聚反应 ,得到了表面为PBMA接枝的聚丙烯酰胺 (PAm g PBMA)聚合物微球 .将所得PAm g PBMA微球在酸性条件下水解 ,得到了整体亲水的聚甲基丙烯酸接枝的聚丙烯酰胺(PAm g PMAA)聚合物微球 .用激光光散射、透射电子显微镜和X射线光电子能谱仪等对聚合物微球的直径、形态及表面组成进行了表征 .研究结果表明 ,在共聚反应中PBMA大分子单体的分子量与浓度、Bis A浓度和介质的组成对微球的形成与颗粒直径的大小有明显影响 ;所形成的聚合物颗粒是以PBMA为壳、以交联PAm为核的核壳结构微球 .

Poly(tert-butyl methacrylate) (PBMA) macromononer with one vinyl end group per polymer chain was synthesized by using free radical polymerization in the presence of 2-mercaptethanol and end capping reaction with p-chloromethyl styrene. The PBMA macromonomer was selected as reaction stabilizer to prepare core-shell polymeric microspheres. The PBMA grafted polyacrylamide (PAm-g-PBMA) microspheres were obtained by dispersion copolymerization of acrylamide (Am) with PBMA macromononer using 2,2′-azobis (N,N′-dimethyl-eneisobutyramidine) (VA) as a free radical initiator in the presence of N,N′-bismethyleneacrylamide (Bis-A) as crosslinking agent in the different ethanol/water mixed solvents at 60℃ for 24 h. Also,the poly(methylacrylic acid) graft polyacrylamide (PAm-g-PMAA) microspheres were obtained by hydrolysis of PAm-g-PBMA microspheres in HCl. The monodisperse polymeric microspheres were studied by using transmission electron microscopy (TEM) and laser light scattering (LLS). It was found that the microspheres have a hydrophilic core and a hydrophobic shell based on the analysis results of X-ray photoelectron spectra. The morphology and diameter of the microspheres can be controlled by changing reaction conditions such as the volume ratio of ethanol to water,the molecular weight of PBMA macromononer,the mole ratio of Am to PBMA macromononer and Bis-A concentration in feed. It was found that the PAm microspheres can be swollen in water greatly and their size distribution remains narrow.