title: Infrared spectroscopic study of stereo-controlled poly(N-isopropylacrylamide) with an extended chain conformation induced by adsorption on a gold surface.
abstract: Poly(N-isopropylacrylamide) (PNiPAM) compounds with various diad tacticities were prepared, and the molecular interaction properties in a thin film deposited on a gold surface were analyzed using infrared spectroscopy. The intramolecular and intermolecular interactions were found to depend on the tacticity, and only atactic (diad ratio 46 %) PNiPAM exhibits poor molecular interaction even in the bulk sample. On the other hand, the same series of compounds dissolved in an acetone solution were spread on a gold surface to form a thin film. In the dissolution process, the polymer molecules are relaxed via solvation, and they are bound to the gold surface by a molecular interaction to form a submonolayer thin film. In the thin film, the molecular interaction with the gold surface via the N-H group was monitored in the infrared spectra only for a nearly isotactic (m = 90) PNiPAM by an apparent shift of the N-H stretching vibration band. This shift was confirmed by changing the degree of hydrophilicity of the gold surface: a larger shift is found on a gold surface with stronger hydrophilicity. As a result, the conformation of a nearly isotactic molecule is found to be extended by the interaction with the gold surface, which works to immobilize the molecule.
authors.affiliation: Laboratory of Solution and Interface Chemistry, Division of Environmental Chemistry, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Shimoaka
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Rikiyama
authors.forename: Yukiteru
authors.initials: Y
authors.lastname: Katsumoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hasegawa