Wettability, Adsorption and Adhesion in Polymer (PMMA)-Commercially Available Mouthrinse System

The study concerns the evaluation of the physicochemical and thermo-adsorptive surface properties of six commercially available mouthrinses, particularly surface tension, surface activity, partitioning coefficient, critical micellar concentration, Gibbs excesses at interfaces, surface entropy, and enthalpy. The aim was to quantify their effect on the adhesion and wettability of a model poly(methyl methacrylate) (PMMA) polymer. The adsorptive and thermal surface characteristics were derived from surface tension (γ) vs. concentration and temperature dependences. Polymer surface wettability was characterized by the contact angle hysteresis (CAH) formalism, using the measurable advancing Θ and receding Θ dynamic contact angles and γ as the input data. Further, wettability parameters: Young static angle (Θ), film pressure (Π), surface free energy (γ) with its dispersive and polar components, work of adhesion (W), and adhesional tension (γ cosΘ) were considered as interfacial interaction indicators. The mouthrinse effect demonstrated the parameter's evolution in reference to the PMMA/pure water case: Θ, Θ and Θ↓, CAH↑, Π↓, W↓, γ↓, and γcosΘ↑. Furthermore, the variations of the surface excess ratio pointed to the formation of multilayered structures of surfactants composing the mouthrinse mixtures considered. The contact angle data allowed for the penetration coefficient and the Marangoni temperature gradient-driven liquid flow speed to be estimated.