Effect of Incorporating a Trace Amount of Fluorocarbon into Poly(N-isopropylacrylamide) on Its Association in Water

A combination of laser light scattering (LLS), viscometry, and fluorescence spectroscopy was used to study the association of a series of fluorocarbon-modified poly(N-isopropylacrylamide) (PNIPAM) copolymers in aqueous solution. The interchain association increases as both the fluorocarbon content and polymer concentration increase, evidenced by the changes of the apparent molar mass, intrinsic viscosity, Huggins constant, and fluorescence excimer-to-monomer intensity ratio. The LLS results are well-represented by the open association model. Our results also revealed that the intrachain association starts when each polymer chain, on average, has more than two fluorocarbon monomers.