Application of Photochemistry in Synthesis of Smart Nanocomposite Hydrogels

Abstract

Abstract Hydrogels are cross-linked, water-soluble polymers which are swollen in water or in aqueous solution. Some of these hydrogels (smart hydrogels) show a drastic change of their properties, particularly the degree of swelling and the modulus, in dependence on the properties (temperature, pH, ionic strength, and composition) of the swelling agent. The application of smart gels requires a defined and fast swell kinetic. Therefore, there is an interest in the synthesis of thin patterned films with good mechanical performance. Photolithography is a powerful method to synthesize films and pattern in the μm-range. Nanocomposite (NC) hydrogels exhibit excellent mechanical properties, even in the swollen state. The photochemical reaction may be stopped easily by switching off the light source. This allows characterizing the structure of molecules formed during the reaction. On example of synthesis of nanocomposite hydrogels the monitoring of photochemical induced network formation by dynamic light scattering is demonstrated. Application relevant properties of NC-gels and the phase diagram are reported. Gels were patterned by UV irradiation through a mask. The patterning process is visualized by FT-IR imaging.