Effect of Fabrication Conditions on the Structures and Photoreactions of Langmuir-Blodgett Films of Amphiphilic Spiropyran

Abstract

We studied the effect of fabrication conditions on the structures and photoreactions of Langmuir and Langmuir-Blodgett (LB) films of an amphiphilic derivative of spiropyran (SP1822). Pure LB films of SP1822 and mixed LB films of SP1822 and arachidic acid (C20) fabricated at high fabrication temperatures consisted of circular domains with a constant height of 4 nm. UV illumination gave rise to the formation of J-aggregates, accompanied by the development of structures extending radially from the nuclei in the domains. Pure LB films of SP 1822 fabricated at low temperatures were comprised of 4-nm-high domains with a considerable amount of voids. On UV illumination, J-aggregation proceeded accompanied with morphological changes. In the mixed LB films of SP1822 and C20 fabricated at low temperatures, the presence of C20 molecules suppressed the diffusion of dye molecules in the films, thereby inhibiting the J-aggregation.