Chromium-assisted immobilization of N-isopropylacrylamide-based methacrylic acid copolymers on collagen and leather surfaces: thermo-responsive behaviour

In the present paper, we report the non-covalent immobilization of pH and temperature responsive poly(N-isopropylacrylamide)-co-methacrylic acid on a protein collagen (type I) and a leather surface. The polymer has N-isopropylacrylamide (NIPAM) functionality that is responsible for the thermo-responsive characteristics and carboxylic acid/carboxylate functionality that facilitates the pH-responsive behaviour. We were able to tune the clouding behaviour of the polymer in water from 15 to 40 degrees C by changing the pH from 4.5 to 5.7. The binding of the polymer to a native collagen protein (type I) or leather is facilitated by the carboxylate groups that form coordination complexes with chromium(III). The polymer was successfully used in the retanning and coating of leather. The polymer-coated leather as well as the polymer-grafted collagen clearly show thermo-responsive characteristics.