Nanowrinkled and Nanoporous Polyethylene Membranes Via Entanglement Arrangement Control



Crystalline homopolymers, including polyethylene (PE), which has the simplest architecture, form a nanometer-sized combination of crystalline and amorphous components, but their arrangement control, similar to self-assembled phase-separation of block-copolymers, is usually difficult. However, molecular entanglements trapped between crystalline and amorphous components of homopolymers coincide with the segmental linking points on the interfaces of the microphase separation for block copolymers. Nanowrinkled PE membranes are prepared with a network of 30 nm-thick homogeneous lamellae using a novel entanglement control technique composed of biaxial melt-drawing and melt-shrinking procedures, which are limited for highly entangled ultrahigh molecular weight materials. Such a network arrangement of nanowrinkling lamellae spreading on membrane surface and also across the membrane thickness improves the mechanical properties of both tensile strength and tearing strength. Subsequent cold-drawing causes delamination of the lamellar interfaces, leading to the resultant nanoporous morphology composed of passing-through channels that are several tens of nanometers in diameter, without any solvent processing.