Synthesis, properties, and functions of thermosensitive copolymers having pyridyl and/or pyridinium groups

The copolymer 4VP-NIPAAm was soluble in dilute HCl below 32 °C, but the quaternized 4VP-NIPAAm copolymer was soluble even in aqueous solutions of pH 6.5 below 28 °C. The thermosensitivity of both 4VP-NIPAAm and the quaternized 4VP-NIPAAm copolymer was observed. The quaternized 4VP-NIPAAm copolymer could adsorb food dyes dissolved in water and the copolymer-dye complexes became water-insoluble. The quaternized 4VP-NIPAAm copolymer also exhibited high antibacterial activity against bacteria such as Escherichia coli.