Eiji Ando

J-aggregation of photochromic spiropyran in Langmuir-Blodgett films

Abstract The possibility of controlling the photochromic reactions of two different spiropyrans was investigated using the Langmuir-Blodgett technique. The spiropyran having a long chain formed an unstable monolayer without UV light and a stable monolayer with UV light. The spiropyran having two long chains, however, could form more stable monolayers with and without irradiation and the most stable monolayer was formed on mixing with n-octadecane in a molar ratio of 1:2. The assemblies of this monolayer, under UV irradiation at temperatures above 35 °C, exhibited a sharp and intense band at a longer wavelength, which could be assigned to the formation of J-aggregates. The half-decay period in the dark was 104 times longer than that of conventional spiropyrans. The possibilities of three-dimensional high density optical memory with this photochromic spiropyran are suggested.

Controls of photochromic reactions in spiropyran Langmuir-Blodgett films☆

The possibility of controlling photochromic reactions has been investigated in Langmuir-Blodgett (LB) films. The formation of J aggregates of a spiropyran (SP1822) with two long chains has been found previously. We have studied another possibility using LB films of 1′-octadecyl-3′,3′-dimethyl-6-nitro-8-methoxy- spiro[2H-1-benzopyran-2,2′-indoline] (SP1801). SP1801 at the air-water interface gave a monolayer which showed the photomerocyanine form. The LB film of the compound returned to the spiropyran form in the dark. The LB film of the hetero structure with SP1801 and stearic acid, however, turned to J aggregates from the photomerocyanine form spontaneously in the dark. The absorption of the J aggregates was a sharp and intense band, and the half-decay period in the dark was 104 times longer than that of conventional spiropyrans. SP1801, in addition to SP1822, is suggested as a candidate for a multifrequency optical memory system with several J-aggregated photochromic compounds having different sharp absorption bands.

Frictional properties of monomolecular layers of silane compounds

The frictional performance of ultrathin films was evaluated, especially in monomolecular layers of silane compounds. The monolayer of γ-(N,N- dioctadecylsuccinylamino)propyltriethoxysilane is one of the candidates for the best lubricating film. The film exhibited a low coefficient of kinetic friction, μk < 0.1, and 105 transits without stick-slip. From X-ray photoelectron spectroscopy and Fourier transform IR analysis, both the adhesion between the molecules of the lubricant and the surface of the substrate and the cohesion between the molecules of the lubricant are extremely strong.

Molecular arrangements of photochromic spiropyrans on a subphase

Abstract The photochromic behaviours of long alkyl chain spiropyrans were observed in a monomolecular layer at the air-water interface. UV-induced merocyanines of SP16 and SP1822 formed J aggregates on the subphase, whereas that of SP1801 did not form. They exhibited different molecular arrangements in the photochromic reaction processes, including the formation of J aggregates. Models of the molecular arrangements of these compounds on the subphase are presented.