The complexation between poly(acrylic acid-g-N-isopropylacrylamide) [P(AA-g-NIPAM)] and poly(N-isopropylacrylamide) (PNIPAM) in an aqueous solution was studied by UV transmittance measurements, fluorescence probe and fluorescence anisotropy techniques. It was found that the complex was formed between the two polymers through hydrogen bonding interactions. Moreover, the complexation showed the dependence on pH values and the AA contents in the graft copolymers. The complexation became stronger with increasing AA contents in the graft copolymers and decreasing the solution pH value. This interaction made the polymer backbones shrink, meanwhile, the complex system exhibited hydrophobic properties, and its hydrophilic character was weakened.

Key words: complexation, P(AA-g-NIPAM), PNIPAM, fluorescence anisotropy