Polymer Mediated Depletion Attraction and Interfacial Colloidal Phase Behavior

We report direct measurements of poly(ethylene oxide) (PEO) mediated depletion attraction between colloids and surfaces using total internal reflection microscopy (TIRM) and in quasi-2D colloidal phase behavior using video microscopy (VM). PEO concentration dependent particle-wall depletion attraction is accurately quantified by a modified Asakura–Oosawa (AO) potential. The modified AO potential employs an equation of state, depletion length, and partition coefficient computed using results from renormalization group (RG) theory. Quasi-2D phase behavior measurements are in excellent agreement with Monte Carlo (MC) simulations using the same modified AO potential. The analytically simple modified AO depletion potential accurately captures depletion attraction for a realistic excluded volume polymer system, which suggests it can be generalized to other material systems.