A molecular dynamics simulation study to investigate poly(vinyl acetate)-poly(dimethyl siloxane) based easy-clean coating: An insight into the surface behavior and substrate interaction

Abstract

Easy-clean coatings have received overwhelming interest in outdoor and indoor surface applications nowadays. Poly (dimethylsiloxane) (PDMS), though a popular hydrophobic material, exhibits poor substrate adhesion which limits its use for aforementioned coating applications. To counter this drawback, blends of PDMS with poly (vinylacetate) (PVAc) of different commercially available hydrolysis grades (0%, 86%, and 100%) have been proposed. Coatings made from such blends shall be sufficiently hydrophobic on one side to exhibit easy-cleaning nature, and on another side, demonstrate sufficient adherence with substrate for durability. Molecular dynamics (MD) simulations have been employed to model such blends to understand their surface behavior, substrate adhesion and to evaluate bulk properties. In this work, blends of PDMS and PVAc with the latter present in varying weight fractions and hydrolysis content have been both simulated and experimentally formulated. Properties like substrate interaction energy (IE), surface energy, transparency, water/oil contact angles (WCA/OCA), solubility parameter and thermal stability (T20/T50) have been investigated. Simulation estimates of surface energy, water/oil contact angles and refractive indices compared well with previously reported results and those of water contact angle and transparency are in proximity to experimental outcomes of this work. The improved surface behavior (WCA∼ 97 ± 1°/OCA∼ 41.6 ± 2°), substrate adhesion (−0.725 mN/m against Al substrate), thermal stability (T20 ∼322 °C/T50 ∼500 °C) and transparency (>89%) estimates enable us to screen and propose a 20 wt% PVAc (0% hyd.) in PDMS as a potential easy-clean coating material.