Water-Retentive/Lipophilic Amphiphilic Surface Properties Attained by Hygroscopic Polysiloxane Ultrathin Films

Hygroscopicity and lipophilicity are opposing properties, and the development of surfaces that exhibit both these properties on a variety of solid substrates and particles is expected to lead to the creation of new functional materials. We recently reported that polydialkylsiloxane, a well-known lipophilic organosilicon compound, can exhibit hydrophilic properties by introducing an ammonium salt group. Herein, we used linear polysiloxanes containing the ammonium salt as surface modifiers. The surface of the substrate was modified with polysiloxane via a photo-initiated thiol-ene reaction. Consequently, this substrate exhibited both hygroscopic and lipophilic surface properties. The surface patterning treatment was carried out under light irradiation using a photomask, and the patterned substrate exhibited unique surface wettability, retaining water only in the presence of the polymer. As this surface treatment procedure can be widely applied to materials containing hydroxy groups on their surfaces, it is expected that various types of functional materials can be created in the future, including the preparation of particles that can be dispersed in both water and oil, or unique fiber materials.