Asymmetric Properties of Ultrathin Poly(vinylchloride) Films as Generated by Molecular Association of Ionic Porphyrins at the Polymer-Water Interface

An amphiphilic porphyrin derivative, 4,4′,4″,4‴-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis[l- hexadecylpyridinium] cation or its zinc complex (abbreviated as MC16TPyP), was preferentially impregnated on a single surface of an ultrathin poly(vinylchloride) film prepared by casting the polymer solution on water. Enrichment of the cationic porphyrin moiety to the polymer-water interface during the film preparation was strongly indicated by contact-angle measurement of water-droplets on the dry surface. A subsequent treatment of the film with an aqueous solution, which contained an anionic porphyrin (4,4′,4″, 4‴-(21 H, 23H-porphine-5,10,15,20-tetrayl)tetrakis[p-benzenesulfonatej anion or its copper or zinc complex: M'TPPS), led to molecular association of the two-types of porphyrins (MC16TPyP-M'TPPS) on the film surface. Spectroscopic evidences for the formation of molecular association on the thin film were obtained by measuring electronic absorption, fluorescence, and optical second-harmonic generation.