干燥方式对含直链淀粉半互穿网络水凝胶溶胀和降解的影响

以4,4′-二甲基丙烯酰胺基偶氮苯(BMAAB)为交联剂,制备了丙烯酸-丙烯酰胺-甲基丙烯酸酯共聚物和直链淀粉半互穿网络水凝胶.以冷冻干燥和空气干燥两种方式,研究了干凝胶在pH2.2和pH7.4时的溶胀和降解性能.结果表明采用两种干燥方式的凝胶在不同pH的介质中都遵循二级溶胀动力学.凝胶内部水的扩散均为非Fickian机理,即扩散和链松弛协同作用的机理.但经历冷冻干燥的凝胶其扩散机制占优势.在pH=7.4的介质中,冷冻干燥凝胶的平衡溶胀比(SR)显著增大,而在pH=2.2时则无明显变化.扫描电镜(SEM)和降解实验发现,在结肠内容物的作用下,冷冻干燥凝胶在5天内降解率可达35.3%,而空气干燥凝胶的降解率为28.1%,表明冷冻干燥的方式可在一定程度上促进凝胶在结肠环境下的降解.

INFLUENCE OF DRY METHODS ON THE SWELLING AND DEGRADATION OF SEMI-IPN HYDROGELS CONTAINING AMYLOSE

The semi-IPN hydrogels of poly(acrylic acid-acrylamide-butyl methacrylate) an d amylose were prepared using 4,4′-bis(methacryloylamino)azobenzene (BMAAB) a s a crosslinker.The swelling behavior and degradation of hydrogels air-dried an d freezed-dried both were investigated by immersion in buffer solutions of pH=2.2 and 7.4.The results indicate that b oth types of gels follow the Schott second-order swelling kinetics.Diffusion o f water in gels was a non-Fic kian process, having a combinational mechanism of diffusion of water molecules a nd relaxation of the macromolecular chain.However,the diffusio n mechanism was dominative for freezed-dried hydrogels.The equilibrium swelling ratio of freez ed-dried hydrogels increases remarkablely in pH=7.4 buffer solutions,but almost no change in pH=2.2 buffer solutions.The degradation of gels was carried out in the presence of colon suspension.SEM and degradation of hydrogels show that the degradation ratios of freezed-dried and air-dried gels were 35.3% and 28.1% within 5 days, respectively.It indicates that the degradation can be enhanced in the colon for gels treated by the freezed-dried method.