Continuous fabrication platform for highly aligned polymer films

Abstract

Superior mechanical and thermal properties in bulk polymers can be achieved by aligning the molecular chains through drawing-induced plastic deformation. Although highly aligned polymer films (HAPFs) are in demand, current fabrication methods are limited to manual, lab-scale batch processes. Here we report a continuous fabrication platform for HAPFs consisting of a three-step sol-gel extrusion, structure freezing and drying, and mechanical drawing process. First, a polymer-solvent solution is subjected to a high shear, high temperature, Couette flow extrusion into a thin film, resulting in initial chain disentanglement. Next, the extruded disentangled structure is frozen using a liquid N 2-cooled substrate, and then solvent is removed from polymer gel through ambient evaporation. Finally, dried films are mechanically drawn within a heated enclosure using a constant-force adaptive-thickness drawing system. The performance of this platform has been confirmed by fabricating polyethylene HAPFs with > 99% crystallinity and draw ratios up to 100× (creating continuous films > 15 m in length).