Structures and permselectivity of multicomponent polymer membranes

This paper describes the relationship between structures of multicomponent polymer membranes and their permselectivity for organic liquid mixtures in pervaporation. Transmission electron micrography demonstrated that the morphology of microphase separation in the multicomponent polymer membranes containing poly (dimethylsiloxane) (PDMS) was quite different between block copolymer membranes and graft copolymer ones. The annealing of the block copolymer membranes resulted in dramatic changes in the morphology of their microphase separation, but that of the graft copolymer membranes did not. Their morphology strongly influenced the membrane permselectivity in the separation of organic liquid mixtures. The analysis using various permeation models revealed that the continuity of the PDMS phase in the microphase separation governs the permselectivity of their membranes. These studies suggested that the morphological designs of multicomponent polymer membranes by the molecular architecture and annealing are very important in controlling membrane properties. In addition, this paper also focuses on simple surface modifications of membranes by polymer additives and on the effect of their surface characteristics on the permselectivity for organic liquid mixtures. Polymer membranes were surface-modified by adding hydrophilic and hydrophobic copolymer additives containing PDMS. The permselectivity of the surface-modified membranes was controlled without lowering their permeability by using some simple surface modifications. Our results suggest a novel concept for designing the structure of high-performance membranes, that is, a method for controlling the permselectivity of pervaporation membranes without lowering their permeability.