聚丙烯酰胺/甲基纤维素半互穿网络的制备及溶胀动力学研究

 以过硫酸铵(APS)为引发剂、N,N′-二甲基双丙烯酰胺(MBA)、四甲基乙二胺(TEMED)为催化剂,在室温下通过水溶液自由基聚合,制备了聚丙烯酰胺/甲基纤维素半互穿网络(PAM/MC semi-IPN)。通过傅里叶红外光谱(FT-IR)对凝胶结构进行了表征,考察了MC含量和温度对凝胶外观、平衡溶胀和溶胀动力学的影响。从FT-IR图谱可看出,随MC含量增加,PAM酰胺Ⅰ带的吸收峰从1632cm^-1移到1650cm^-1,表明PAM与MC发生了明显的氢键相互作用。随MC含量增加,凝胶颜色从透明到乳白色逐渐加深。随温度升高,各组分凝胶的平衡溶胀比都增大。随MC含量的增加,相同温度下,凝胶的平衡溶胀比下降。另外,半互穿网络凝胶的尺寸随温度升高没有明显变化,说明MC在高温下的相转变并未造成半互穿网络的体积相变。凝胶的溶胀动力学显示,凝胶在100min前均快速溶胀,在200min以后溶胀速度变缓,最终趋于平衡。扩散指数(n)和溶胀速率(k)的数据表明,温度对扩散机理有很大影响,并且MC含量低于1.0%时凝胶组成对扩散机理影响不大。通过线性拟合的R²可知,各组分凝胶在各温度下均较好的符合二级动力学方程,并且MC含量低于1.0%时对凝胶的初始溶胀速率影响不大。

Preparation and Swelling Dynamics Research on Polyacrylamide/methyl Cellulose Semi-interpenetrating Polymer Networks

Polyacrylamide/methyl cellulose semi-interpenetrating polymer networks (PAM/MC semi-IPNs) were prepared by aqueous radical polymerization at room temperature and APS, MBA, and TEMED were used as initiator, crossliking agent, and accelerator, respectively. The structure of hydrogels was characterized by FT-IR. The influence of MC content and temperature on hydrogel appearance, equilibrium swelling, and swelling kinetics of semi-IPN was investigated. The FT-IR spectra show that the peak of aminoⅠfor PAM is shifted from 1632cm^-1 to 1650cm^-1; the fact indicates that there is a strong hydrogen-bonding interaction between PAM and MC. The color of hydrogels becomes muddier from transparent to milky-like as MC content increasing. The equilibrium swelling of the series of hydrogels is enhanced as temperature increasing. However, at the same temperature, the equilibrium swelling of hydrogel is suppressed as MC content increasing. In addition, the size of semi-IPN hydrogels does not change much as temperature rising, it is inferred that the phase transition of MC at higher temperature does not lead to volume phase transition of semi-IPN hydrogel. All the hydrogel samples show rapid swelling properties before 100min, the swelling becomes slow down after 200min, and eventually the swelling approaches the equilibrium. The data of diffusion index (n) and swelling rate (k) infer that the temperature has great influence on the diffusion mechanism and swelling rate, whereas the hydrogel that its MC content is under 1.0% has little influence on that. The swelling of hydrogel is conformed to the second-order kinetics equation quite well under varying temperatures.