Chain diffusion and exchange during build-up of hydrogen-bonded polymer complex film

Abstract

Poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA) were layer-by-layer (LbL) assembled to prepare thin film based on hydrogen bonding. A series of simple experiments were designed to investigate polymer chain diffusion and exchange behaviors of hydrogen-bonded PVPON/PAA film. PAA was labeled with fluorescence dye, fluorescein amine (FAM). The prepared (PVPON/PAA)20 films were immersed into PAA solution, PVPON solution and PAA-FAM solution separately, for a period that was much longer than the assembly time, and the thickness, the composition and the characteristic absorbance of the film were monitored. The experiment results indicated that polymers not only diffused into the thin film from the assembly solution but also diffused out from the thin film into the assembly solution, i.e. there existed a polymer chain exchange. The growth of hydrogen-bonded PVPON/PAA film was related with polymer chain diffusion and exchange at a certain time scale.