Kinetics of autophobic dewetting of polymer films

Abstract

We experimentally investigated the retraction of poly(dimethylsiloxane) films of variable thickness on layers of chemically identical molecules, end-grafted onto a silicon substrate (autophobic dewetting of a melt-on-brush system). Measuring simultaneously the dewetted distance (d) and the width (w) of the rim formed by the collection of the retracted liquid, we were able to determine in situ and in real time (t) the contact angle, the velocity of retraction, and the energy dissipation mechanism at the melt-brush interface. The dewetting velocity decreased linearly with the width of the rim. Together with the characteristic thickness dependence and an exponent α of 2/3 for the power-law behavior of d to approximately tα, we concluded that the melt is slipping on the brush. The slippage length was on the order of 10 μm, indicating little interpenetration between melt and brush. We demonstrate that dewetting experiments represent a valuable tool for the characterization of static and kinetic properties of polymer-polymer interfaces.