γ-丁内酯对聚醚酰亚胺膜结构形态的影响

Influence of γ-butyrolactone on the morphology of polyetherimide membranes

以聚醚酰亚胺(PEI)为制膜材料、N-甲基吡咯烷酮(NMP)为溶剂、γ-丁内酯(GBL)为弱非溶剂以及纯水为凝胶剂,采用浸没沉淀法制备了系列平板膜和厚度梯度膜,考察了GBL的存在对铸膜液黏度、平板膜及厚度梯度膜结构的影响.随着GBL浓度的增加,PEI铸膜液的黏度会增大,当m(GBL)∶m(NMP)达到69.6∶15.4时,PEI聚合物溶液黏度急剧增大,促使PEI聚合物溶液由单一均相溶液向贫/富两相区转化.GBL浓度增加的同时,PEI膜结构形态逐渐由完全的指状结构向海绵结构转化.就PEI厚度梯度膜而言,当膜厚增加到临界结构转化厚度Lc时,海绵状结构开始向指状孔结构转变.铸膜液体系中GBL浓度的增加延迟了厚度梯度膜中海绵状结构向指状孔结构的转化,临界结构转化厚度Lc随着铸膜液体系中GBL浓度的增加而增加.

By immersion precipitation method, polyetherimide （PEI） flat sheet membranes and PEI thicknessgradient membranes were prepared with PEI/N- methyl pyrrolidone （NMP）/γ-butyrolaetone（GBL） casting solutions and coagulant water. The effect of GBL on the viscosity of the casting solution, the morphology of PEI flat sheet membranes and thickness - gradient membranes was studied. With the increase in GBL in the casting solution, the solution viscosity increased. When the ratio of rn （GBL） ： m （NMP） was up to 69.6：15.4, the solution viscosity increased greatly, resulting in the phase inversion. Meanwhile, with the increase in GBL in the casting solution, the morphology of PEI flat sheet membranes evolved from finger- like structure to sponge- like structure. When the membrane thickness approached to the critical structure - transition Lc, the morphology of PEI thickness - gradient membranes evolved from sponge - like structure to finger- like structure. The existance of GBL in the casting solution prevented the transition of sponge - like structure to finger - like struc- ture, resulting in the increase in Lc.