Dual-Cure Dynamic Networks for Mechanophotopatterning of Surface Topography

Abstract

Control of thin film surface features is critical in the fields of optics, biologics, electronics, and microfluidics, among others. Although facile in method, implementation of mechanophotopatterning has been chemically constrained, resulting in an undesired evolution or a limited processing window. This work overcomes these limitations by combining dynamic covalent chemistry to alter the surface relief with a dual-cure approach that increases the cross-link density and glass transition temperature following patterning to permanently fix the structure. The inclusion of a photosensitive dynamic covalent moiety, in the form of an allyl sulfide, allows for spatiotemporal stress relaxation control, and the associated formation of topographic patterns when the elastomer is exposed to light under strain. Typically, the resulting topography remains susceptible to undesirable evolution as the network’s dynamic capacity persists. To mitigate the residual dynamics, 65 wt % bisphenol A diglycidyl ether is included, in combination with a thermally latent acid, to facilitate a post-topography altering cationic polymerization which permanently fixes the topography through large changes in cross-link density and glass transition. Feature height of films fixed by this cure remain within 100 nm (<1% change), of their original dimensions.