title: Control of photoreaction of amphiphilic spiropyran/n-alkane Langmuir and Langmuir-Blodgett films using the phase transition of n-alkane.
abstract: The structures and photoreactions of Langmuir and Langmuir-Blodgett (LB) films of an amphiphilic spiropyran, 1',3'-dihydro-3',3'-dimethyl-6-nitro-1'-octadecyl-8-(docosanoyloxymethyl)spiro[2H-1-benzopyran-2,2'-(2H)-indole] (SP), mixed with n-alkane are investigated. The mixing ratio was fixed at 1/2 for SP/n-alkane. The surface pressure-area isotherms of SP/octadecane are categorized into two regimes: a low-temperature regime where octadecane is packed with the alkyl chains of SP, and a high-temperature regime where the addition of octadecane does not influence the isotherms significantly. The temperature dividing the two regimes is related with the melting point of the n-alkane mixed with SP in the bulk. UV irradiation of the Langmuir film in the high-temperature regime gives rise to light-induced J-aggregation, whereas that in the low-temperature regime causes only the isomerization of SP to the corresponding merocyanine, indicating that J-aggregation is hindered by the presence of n-alkane in the low-temperature regime. IR external reflection spectroscopy of the Langmuir films shows that n-alkane is released from the film during J-aggregation. The structural changes of the mixed Langmuir and LB films during J-aggregation are almost the same with those of the films of pure SP.
authors.affiliation: Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nakazawa
authors.forename: Reiko
authors.initials: R
authors.lastname: Azumi
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abe
authors.forename: Mutsuyoshi
authors.initials: M
authors.lastname: Matsumoto
mesh_terms: D000473:Alkanes / Q000737:chemistry* / Q000528:radiation effects*; D001578:Benzopyrans / Q000737:chemistry* / Q000528:radiation effects*; D007211:Indoles / Q000737:chemistry* / Q000528:radiation effects*; D008567:Membranes, Artificial; D015394:Molecular Structure; D009574:Nitro Compounds / Q000737:chemistry* / Q000528:radiation effects*; D010316:Particle Size; D044367:Phase Transition; D010777:Photochemistry; D013141:Spiro Compounds / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: C509603:1',3'-dihydro-3',3'-dimethyl-6-nitro-1'-octadecyl-8-(docosanoyloxymethyl)spiro(2H-1-benzopyran-2,2'-(2H)-indole); D000473:Alkanes; D001578:Benzopyrans; D007211:Indoles; D008567:Membranes, Artificial; D009574:Nitro Compounds; D013141:Spiro Compounds; C088184:spiropyran