A copolymer of N-isopropylacrylamide (NIPAAm), ruthenium-complex (Ru(bpy)(3)), and N-succinimidyl acrylic acid (NAS) was synthesized to investigate its selfoscillating properties in a solution. This polymer exhibits self-oscillation in turbidity and viscosity synchronized via a Belousov-Zhabotinsky (BZ) reaction. The molecular size of the polymer during oscillation was investigated by dynamic light scattering and electrochemical measurements. Both molecular size and viscosity exhibited periodic changes during the BZ reaction. A simple mechanism accounting for such periodic changes was investigated by numerical calculations. (c) 2007 Wiley Periodicals, Inc.