title: Effect of functional group on the monolayer structures of biodegradable quaternary ammonium surfactants.
abstract: The monolayer structures and conformational ordering of cationic surfactants including the biodegradable quaternary ammonium molecules have been systematically characterized by π-A isotherm, surface potential, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and sum frequency generation (SFG) vibrational spectroscopy. It was found that the monolayer of the typical dialkyl dimethylammonium on the water surface was less densely packed along with many conformational gauche defects. The packing density and ordering of these monolayers were improved as halide ions were added to the subphase. A similar condensation effect was also observed when amide or ester groups are present in the alkyl tails of the surfactant. These results are discussed on the basis of the repulsive electrostatic interactions between the terminal ammonium moieties, the hydrogen bonding between the functional groups in the alkyl chains, as well as the flexibility of the alkyl chains in these surfactants. The present study is crucial to understanding the relationship between the interfacial structures and the functionalities of the biodegradable quaternary ammonium surfactants.
authors.affiliation: Catalysis Research Center, Hokkaido University , Sapporo 001-0021, Japan.
authors.forename: Aimin
authors.initials: A
authors.lastname: Ge
authors.forename: Qiling
authors.initials: Q
authors.lastname: Peng
authors.forename: HengLiang
authors.initials: H
authors.lastname: Wu
authors.forename: Huijin
authors.initials: H
authors.lastname: Liu
authors.forename: Yujin
authors.initials: Y
authors.lastname: Tong
authors.forename: Takuma
authors.initials: T
authors.lastname: Nishida
authors.forename: Naoya
authors.initials: N
authors.lastname: Yoshida
authors.forename: Keigo
authors.initials: K
authors.lastname: Suzuki
authors.forename: Takaya
authors.initials: T
authors.lastname: Sakai
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Osawa
authors.forename: Shen
authors.initials: S
authors.lastname: Ye
mesh_terms: D006860:Hydrogen Bonding; D015394:Molecular Structure; D000644:Quaternary Ammonium Compounds / Q000737:chemistry* / Q000378:metabolism; D055672:Static Electricity; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents