Experimental and theoretical study on the temperature dependence of water contact angle on Polydimethylsiloxane film

To investigate the effect of temperature on the contact angle of water droplets on polydimethylsiloxane （PDMS） films, a self-built high-temperature and high-pressure sessile-drop visualization system was adopted in this study. Combined with the low-bond axisymmetric drop shape analysis, the morphologies of water droplets on the PDMS surface were systematically captured, and their corresponding contact angles were accurately measured at a constant pressure of 5 MPa over a temperature range of 30–210 °C. The experimental data revealed that the contact angle remains essentially constant at ~96° throughout the entire temperature range, exhibiting negligible temperature sensitivity. On the theoretical side, the water-PDMS interaction was represented by a Steel 10-4-3 potential, with the water-PDMS attraction energy treated as an adjustable parameter. After calibrating this parameter to the experimental contact angle at a single arbitrary temperature, classical density functional theory combined with Young’s equation was used to predict the contact angle evolution. The calculations indicated a slight increase in the contact angle with temperature at low temperatures, followed by a pronounced decrease at higher temperatures, a trend that deviates from the experimentally observed plateau. This discrepancy suggests that the interaction potential requires further refinement. The present work not only enlarges the high-temperature, high-pressure contact angle database for water-solid systems but also provides a valuable guidance for future theoretical development.