Ultrastrong, Ultraflexible, and Ultratransparent Polyethylene Cellular Nanofilms

TL;DR

This paper presents a novel method to create ultrathin, transparent, and mechanically strong polyethylene cellular nanofilms with potential applications in flexible devices and membranes.

Contribution

The authors developed a sequential planar extension technique to produce ultrathin, transparent, and high-strength polyethylene nanofilms with unique cellular microstructures.

Findings

Nanofilms as thin as 20 nm with >98.5% transparency.

Ultrahigh tensile strength of 1071 MPa.cm^3.g^(-1).

Reversible deflection of 43 nm thick film up to 8.0 mm.

Abstract

Light weight and mechanically robust cellular polymer nanofilms provide materials solutions to many cutting-edge technologies, such as high-flux membrane filtration, ultrathin flexible energy storage, and skin-conformable devices. However, it remains challenging to fabricate hand manipulatable cellular polymer nanofilms for use as self-standing structural materials. Herein, we used a sequential planar extension approach to transform low-entanglement ultrahigh molecular weight polyethylene (UHMWPE) gel films dispersed in porogenic polyethylene oligomers into cellular nanofilms consisting of stretch-dominated triangular cells of molecularly anisotropic cell edges. The microstructure afforded the cellular nanofilm, which had a thickness down to 20 nm, with a unique combination of ultratransparency (>98.5%), ultrahigh in-plane tensile strength (1071 MPa.cm^3.g^(-1)), and ultrahigh flexibility: a 43 nm thick film can deflect reversibly up to 8.0 mm in depth (185,000 times) under a spherical indentation load. As an application, we fabricated the nanofilm into a freestanding ultratransparent respiratory face covering. The new polyethylene cellular nanofilms are expected to represent a new class of platform membranes for advancing fundamental and technological development.