Wettability of Phosphonium Benzene Sulfonate on Parafilm

The wettability of phosphonium benzene sulfonate on parafilm has been investigated by means of dynamic contact angle measurement. Based on the surface tension data, the spreading coefficient, adhesion tension (γlg cosθ), and adhesion work (WA) were further analyzed. It was revealed that the surface tension and contact angle decreased with the increase in concentration, and remained constant when the concentration was higher than the critical micelle concentration (CMC). Furthermore, the spreading coefficient increased with increase in concentration then stays unchanged. In the studied concentration range, the value of spreading coefficient is negative, indicating that it cannot rapidly spread the surfactant on the parafilm surface to an uniform film. The measurements show a linear relationship between the adhesion tension γlg cosθ and the surface tension in the concentration range of 2 × 10−6 mol L−1 to 1 × 10−4 mol L−1. The adsorbed amount of surfactant molecules at the parafilm-solution interface is lower than that at the gas-liquid interface. The value of WA was initially decreased then increased as the concentration was increasing and reaches a minimum value at the concentration near the CMC.