Development of highly functional membranes through structural control of crystalline/amorphous phases

Abstract

Molecular entanglements have been thought to restrict a desirable chain orientation during drawing. Therefore, a reduction in chain entanglements has been a focus for manufacturing high-performance fibers and membranes. In contrast, our melt-drawing technique utilizes molecular entanglements as a strain transmitter, achieving a nanoperiodic arrangement in which the crystalline and amorphous phases are interconnected. This periodic structure is similar to microphase separation in block copolymers, in which linked points are located at the boundaries between chemically different phases. The results show highly functional membranes can be successfully prepared from highly entangled homopolymer, as well as block copolymer, using solvent-free procedures. Molecular entanglements (left) divide the crystalline and amorphous phases and are similar to the linked points that cause microphase separation in block copolymer (right). Our melt-drawing technique results in periodic arrangement of these phases and replaces the conventional paradigm of “entanglement exclusion for high performance” with the novel “entanglement utilization for high functionality”. In this review, our recent developments for nanostructured membranes using block copolymers and homopolymers are compared and reviewed based on their structural similarities.