醇溶剂交换对聚合物/黏土纳米复合水凝胶的性能改进及结构表征

采用原位自由基聚合,制备了聚N,N-二甲基丙烯酰胺(PDMAA)/黏土(clay)纳米复合水凝胶(D-NCgel),黏土在体系结构中充当多官能团交联点的作用.考察了D-NC gel中溶剂水被交换为醇溶剂时,凝胶结构稳定性,溶胀特性,以及机械性能的变化.D-NC gel在醇溶剂中仍能保持完整的三维网络结构,体系没有瓦解.而且,D-NC gel在醇溶剂中表现出依赖于醇溶剂种类的溶剂交换和溶胀行为.在甲醇中,凝胶溶胀度呈现单调增长,但是在其它醇溶剂,如乙醇、1-丙醇或1-丁醇中,凝胶表现出先收缩后溶胀的特殊溶胀行为.通过在醇溶剂中先溶胀后干燥的方法,制备具有优异机械性能的醇溶剂纳米复合凝胶.与D-NC5 gel相比,D-NC5甲醇凝胶其拉伸力学强度提高了67%(从155 kPa增加到259 kPa),拉伸模量提高了49%(从7.5 kPa增加到11.2kPa).基于凝胶在醇水溶剂中结构可逆性讨论的基础上,探讨了醇溶剂对D-NC水凝胶的改性机理.

MODIFICATION AND CHARACTERIZATION OF POLYMER/CLAY NANOCOMPOSITE HYDROGELS BY EXCHANGING WATER WITH ALCOHOLIC SOLVENTS

The effects of replacing water solvent of nanocomposite gels with alcoholic solvents are investigated on structure stability,swelling and mechanical properties of nanocomposite hydrogels(D-NC hydrogel).D-NC gels was prepared by in situ free radical polymerization of monomer(N,N-dimethylacrylamide) in the presence of exfoliated clay.Clay acts as the multifunctional plane crosslinking agent.NC hydrogels maintained the three-dimensional structure without collapsing after exchanging solvents with alcoholic solvents.It was found that NC gels that originally containing water exhibit different exchange and swelling behaviors depending on the type of alcohol in which the gels are immersed.In methanol,the swelling ratio of a D-NC gel increases monotonously as in the case of water.However,D-NC gels first shrink and then swell during immersing in other alcohols such as ethanol,propanol and butanol.Furthermore,D-NC alcoholic solvent gels with ultrahigh mechanical properties are obtained by solvent exchanging process of first swelling in a target solvent and then drying.For example,compared to those of D-NC5 hydrogels,the tensile strength of D-NC5 methanol gel increases by 67%(from 155 kPa to 259 kPa) and modulus increases by 49%(from 7.5 kPa to 11.2 kPa).Based on the reversibility of the structure during the solvent water/methanol alternative exchanging,the modification mechanism was discussed primarily.