Effect of density of hydrogen-bonding donor on hydrogen-bonded multilayer buildup

The effect of density of hydrogen-bonding do-nor (HBD) on the formation of layer-by-layer assemblies of poly(4-vinylpyridine) and poly(4-vinylphenol) was investi-gated. For this purpose, a series of ethyl-substituted poly(4-vinylphenol) (EsPVPhf) with variable ethyl substitute percentage was synthesized by grafting the phenol moiety along the poly(4-vinylphenol) backbone with 1-bromoethane. UV-vis spectroscopy revealed a uniform deposition process of the hydrogen-bonded multilayer consisting of poly(4- vinylpyridine) (PVPy) and EsPVPhf with variable density of HBD. Notably, it was found that increasing the HBD density of EsPVPhf resulted in a marked decrease of both amount of polymers adsorbed and film thickness, which should be re-lated to the EsPVPhf conformation change from coiled state to extended conformation in ethanol solution. Compared with the effect of charge density in polyelectrolyte multilayer, however, there does not exist a critical density of HBD in our case of hydrogen-bonded multilayer assembly. In addition, surface structures of PVPy/EsPVPhf multilayer films also can be tailored controllably by adjusting HBD density of EsPVPhf. As a result, a new method for tuning the structure of hydrogen-bonding-directed multilayer films was devel-oped.