Hydrogen-bonding-directed layer-by-layer assembly of dendrimer and poly(4-vinylpyridine) and micropore formation by post-base treatment

We reported a way to fabricate microporous films by post-base treatment of hydrogen-bonding-directed multilayer films of poly(4-vinylpyridine) (PVP) and carboxyl-terminated polyether dendrimer (DEN-COOH). The PVP/DEN-COOH multilayer film was fabricated by layer-by-layer assembly of PVP and DEN-COOH from a methanol solution. UV-visible spectroscopy revealed a uniform deposition process. The interaction between PVP and DEN-COOH was identified as hydrogen bonding through Fourier transform infrared (FT-IR) spectroscopy. Meanwhile, the composition change of a PVP/DEN-COOH multilayer film in a basic solution was detected by X-ray photoelectron spectroscopy and UV-visible spectroscopy, and the morphology variation was observed by atomic force microscopy. A two-step variation was observed: the dissolution of DEN-COOH from the multilayer into the basic solution and the gradual reconformation of PVP polymer chains remaining on the substrate, which produced a microporous film. Interestingly, compared with our previous PVP/poly(acrylic acid) (PAA) system under the same conditions, the release of DEN-COOH from a PVP/DEN-COOH multilayer is slower than that of PAA, and the microporous morphology is also different, which indicates that the molecular structure of a building block has a remarkable influence on the variation of a hydrogen-bonding-directed film in a basic solution.