On the structure, morphology and transport through limitedly flexible chain sulfonated co-polyimide

Abstract

The relationship between structural features and selective transport properties of a polymer remains to be the topic of major interest among the scientists working in the field of membrane materials development. In the present work the structural and morphological features of the sulfonated co-polyimide and their role in the realisation of its selective transport properties are discussed. The features of the macromolecular chain having limitedly flexible -O-Ph-O- fragment and their influence on the properties of the material are studied with X-Ray diffraction analysis and differential scanning calorimetry. Microphase separated morphology of the block-co-polyimide was detected by the means of atomic force microscopy in the lateral force contrast mode. Theoretical and practical studies on the influence of the counterion nature on the block-copolymer morphology are conducted. Transport properties of the co-polyimide were investigated in the processes of pervaporation and gas separation. Morphological features of the copolymer allow the realisation of the selective fixed-site carrier facilitated transport in terms of pervaporation separation of various binary methanol mixtures. The polymer showed good separation performance in application to pervaporation separation of close to azeotropic MeOH/DMC and MeOH/DME mixtures reaching selectivity values close to 4. The relationship between real and ideal separation selectivities during PV of the studied mixtures are established. The lamellar-like morphology of the studied co-polyimide along with its other unique properties makes it perspective in application to fixed-site carrier facilitated pervaporation and gas separation membranes development.