Layer-by-layer (LbL) assembly has been rigorously applied to the construction of superhydrophobic surfaces.Typically, this involves generating a hierarchical porous structure which is then coated with a low surface energy compound. In this study, a porous LbL film was constructed from poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) using a PAA solution with a bimodal molecular weight distribution. This solution was prepared by mixing two PAA solutions with different average molecular weights (100,000 and 15,000 g/mol). The mixing ratio was adjusted for fine control of the porous structure, which was induced by acid treatment at pH 2.0-2.4. Generally, surface pore structure was weakened as the 15,000 g/mol PAA ratio increased. However, the surface roughness decreased or increased as the 15,000 g/mol PAA ratio increased depending on the acid treatment pH and time. The porous LbL films were coated with fluorinated silane to make them hydrophobic. When the acid condition was pH 2.4 for 5min, the water contact angle decreased significantly from 132o to minimum of 105o as the amount of 15,000 g/mol PAA increased. However, at pH 2.0 for 5min, the water contact angle decreased smaller from 148o to 139o as the amount of 15,000 g/mol PAA increased.

Layer-by-layer Porous Superhydrophobic Molecular Weight Multilayer

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