Solvent effect on hydrogen-bonded thin film of poly(vinylpyrrolidone) and poly(acrylic acid) prepared by layer-by-layer assembly

The hydrogen-bonded thin film of poly(vinylpyrrolidone)(PVPON)/poly(acrylic acid) (PAA) was prepared via layer-by-layer (LbL) assembly. A serial of solvents has been selected to study the formation and disintegration of the thin film. The film could be produced in acidic water and alcohols but could not be fabricated in some polar aprotic solvents, such as dimethylacetamide (DMA), dimethylsulfoxide (DMSO), tetramethylurea (TMU) and N-methyl pyrrolidone (NMP). In acidic water, the film growth was much quicker than that in alcohols. The solvent effect on the film growth was analyzed from the aspects of the polymer-solvent interaction and polymer chain conformation in the assembling solution. In addition, the thin films prepared in aqueous solution were immersed into the polar aprotic solvents to observe the disintegration process. At the room temperature, DMSO dissolved the thin film quickly, DMA dissolved the thin film in 1-2 days, but in NMP or TMU the thin film could keep intact for several weeks. As the temperature elevated, the disintegration would accelerate. The thin film prepared by the higher molecular weight PVPON and PAA showed stronger resistance to the polar aprotic solvents. (C) 2015 Elsevier B.V. All rights reserved.