Monomolecular and thin polymer films: Fabrication, characterization, applications, and models of wetting.

摘要

A variety of chemically modified surfaces were synthesized and their molecular structures and reactivities were characterized. These interfaces include: (1) Monomolecular films of n-alkanoic acids (CH(sub 3)(CH(sub 2))(sub n)COOH) and n-perfluorocarboxylic acids (CF(sub 3)(CF(sub 2))(sub n)COOH) on silver; and (2) calcichrome immobilized at an anion exchange polymer film. The monomolecular films were fabricated by the self-assembly method and characterized by optical ellipsometry, infrared reflection spectroscopy, and contact angle measurements. A comparison is given of the properties of these films with regard to composition, defectiveness, intermolecular environment, molecular orientation, wettability, and formation thermodynamics. As it is relevant to monolayer formation thermodynamics, the isoelectric point of the surface of evaporated silver films was determined by contact angle titration. Potential applications of these films are discussed. Monomolecular films as models of wetting are also examined in terms of van der Waals interactions at the macroscopic interfaces. Theoretical considerations of the effects of intermolecular forces on depth sensitivity of wetting and limiting contact angles of various systems are assessed. One of the synthesized interfaces has been applied as a Ca(II) optical sensor. The sensor was fabricated by electrostatic immobilization of calcichrome at an anion exchange polymer film. The structure and reactivity of this interface was characterized by ultraviolet-visible diffuse reflectance spectroscopy and infrared photoacoustic spectroscopy. Equations to determine the metal complex formation constant and acid dissociation constants of the immobilized reagent form diffuse reflectance spectra are developed. Possible causes affecting the reactivity of an immobilized indicator are discussed.