Suppressed Cracking in Drying Nanoparticle-Polymer Coatings at High Peclet Numbers

Abstract

We provide experimental evidence that spontaneous cracking in silica-poly(vinyl alcohol) aqueous suspensions is significantly suppressed at high Peclet numbers (Pe). The cracking event in drying suspension coating was quantified by measuring numbers of nucleation points per unit area from acquired time-lapse video images. Direct imaging revealed that increases in Pe, i.e. the film shrinkage rate relative to the particle diffusion rate, postponed the secondary crack nucleation and the inter-crack connection to thicker films. The primary nucleation was first suppressed and then enhanced as increasing Pe, resulting in a remarkable morphology transition from ladder-like to distinct star-like cracks.