Synthesis of the Materials with a Switchable Wettability Based on Photosensitive Terpolymers Containing Poly(Titanium Oxide)

Abstract

In this paper, we synthesized the organic–inorganic terpolymers based on poly(titanium oxide) ((≡TiO)_n), hydroxyethyl methacrylate (HEMA), and various organic vinyl monomers (styrene, vinylbutyl ether, butyl methacrylate, isobornyl acrylate, 2-ethylhexyl acrylate, acrylonitrile, and methyl methacrylate) by using a polycondensation-polymerization method. Independent of the composition, the terpolymers are optically transparent in the visible spectral range (transparency is T ~ 90%). Using X-ray phase analysis, the terpolymers were established to have an amorphous structure, and the poly(titanium oxide) chains are self-organized into anatase-type nanoclusters. The dimming of terpolymers occurred under the effect of UV irradiation as a result of the reversible photochromic one-electron transition Ti⁴⁺ + \(\bar {e}\)\( \rightleftarrows \) Ti³⁺. The change in the nature of monomers of terpolymers and the molar ratio of their components allows controlling the rates of both direct and reverse reactions and also leads to the modification of the strength characteristics of the materials. The biggest change in light transmission under UV exposure for 180 min is observed in terpolymers with styrene, butyl methacrylate, and acrylonitrile monomers at a molar ratio of the components [(≡TiO)_n] : [HEMA] : [M] = 1 : 5 : 1; the corresponding changes are 55, 70, and 60%. Higher rates of the Ti³⁺ → Ti⁴⁺ + \(\bar {e}\) reaction (clearing) are observed for materials of the indicated composition, as well as for terpolymers with vinylbutyl ether monomers. The effect of photoinduced superhydrophilicity was found for terpolymers; i.e., a ~60° reduction in the contact angle of their surface under UV exposure was observed.