Heat-indueed Crystal Transformation of Synthetic Bilayer

Okuyama, Kenji; Ikeda, Mieko; Yokoyama, Shingo; Ochiai, Yanami; Hamada, Yusuke; Shimomura, Masatsugu

doi:10.1246/cl.1988.1013

Cited by 17 publications

(29 citation statements)

References 2 publications

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“…17,18,44,45 Thus, the present results for the H-and J′-aggregates found in the LB films of 12A3H may be similar to those for C n AzoC m N + Br -in the cast films.…”

Section: Discussionsupporting

confidence: 82%

“…As in the case of the latter, 17,18,24 the J′-aggregates of the former show a red shift by 5-10 nm in the UV-vis spectra by cooling down the film from above 100 to 30°C (Figure 2). This observation strongly suggests that the J′-aggregate is transformed to the J-aggregate after annealing.…”

Section: Discussionmentioning

confidence: 64%

“…17,18 The band in the 350-400 nm region is broad and has a shoulder near 385 nm, indicating the existence of at least two kinds of J-aggregates (hereafter the J-aggregates formed at elevated temperatures are referred to as J′-aggregates. 17,18 ). Similar heat-induced conversion from H-to J′-aggregate was reported for cast films of C n AzoC m N + Br -.…”

Section: Uv-vismentioning

confidence: 99%

“…17,18 Therefore, temperature-dependent changes in the molecular structure and orientation of the LB films of 12A3H may also be linked with the conversion from H-to J-aggregate.…”

Section: Introductionmentioning

confidence: 99%

“…[17][18][19] Experimental Section Sample Preparation. The azobenzene-containing long-chain fatty acid 12A3H was commercially supplied by Dojin Chemical Co. Ltd. (Kumamoto, Japan) and used without further purification.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Studies on Phase Transitions in Langmuir−Blodgett Films of an Azobenzene-Containing Long-Chain Fatty Acid: Dependence of Phase Transitions on the Number of Monolayers and Transition Cycles among H-, J-, and J‘-Aggregates in Multilayer Films

et al. 1996

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Ultraviolet-visible (UV-vis), infrared transmission, reflection-absorption (RA), and fluorescence spectra have been measured for one-, three-, and nine-monolayer Langmuir-Blodgett (LB) films of an azobenzenecontaining long-chain fatty acid (4-dodecyloxy-4′-(3-carboxytrimethyleneoxy)azobenzene, abbreviated 12A3H) at various temperatures to investigate dependences of phase transitions and annealing effects on the number of monolayers. The UV-vis spectra of the LB films have revealed that the fatty acid investigated forms H-aggregates in the LB films irrespective of the number of monolayers at room temperature. With a temperature increase the H-aggregate in the one-monolayer LB film gradually breaks into the monomers, while that in the three-and nine-monolayer LB films abruptly changes into the J-aggregate near 90°C. These observations show that the one-monolayer LB film does not have a clear order-disorder transition, while the three-and nine-monolayer films have a phase transition near 90°C. The infrared study has also given unambiguous evidence that supports this conclusion. For example, the peak intensities of CH 2 antisymmetric and symmetric stretching bands at 2920 and 2850 cm -1 in the transmission spectrum of the one-monolayer film gradually decrease with temperature, suggesting that the alkyl chain becomes tilted little by little with respect to the surface normal. In contrast to the one-monolayer film, the peak intensities of most of the infrared bands of the three-and nine-monolayer films undergo a marked change near 90°C. Therefore, it seems that the tilt angles of both the alkyl chain and chromophobic part change largely concomitantly with the conversion from the H-aggregate to the J-aggregate. Cyclic thermal treatment experiments for the UVvis spectra of the LB films show that the conversion from the H-aggregate to monomers in the one-monolayer film is nearly reversible, while annealing of the three-and nine-monolayer films causes a transition from the J-aggregate to another J-aggregate. The latter J-aggregate is further converted to the original H-aggregate by leaving the LB films in the atmosphere or irradiating them with UV laser light.

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“…17,18,44,45 Thus, the present results for the H-and J′-aggregates found in the LB films of 12A3H may be similar to those for C n AzoC m N + Br -in the cast films.…”

Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 64%

Section: Uv-vismentioning

confidence: 99%

“…17,18 Therefore, temperature-dependent changes in the molecular structure and orientation of the LB films of 12A3H may also be linked with the conversion from H-to J-aggregate.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Spectroscopic Studies on Phase Transitions in Langmuir−Blodgett Films of an Azobenzene-Containing Long-Chain Fatty Acid: Dependence of Phase Transitions on the Number of Monolayers and Transition Cycles among H-, J-, and J‘-Aggregates in Multilayer Films

et al. 1996

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Reactivity and Crystal Structure

Ohashi¹

1994

Reactivity in Molecular Crystals

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Investigation of solid-state polymerization of crystalline monomers has attracted increasing attention over the past three decades.') Development of this subject relied on the use of ultraviolet(UV) light and ionizing radiation. The high penetration of y rays enables homogeneous initiation of the polymerization in whole crystals. It is also easy to determine the polymer yields per absorbed energy and t o compare inherent reactivities of monomer crystals. O n the other hand, the homogeneous initiation of the polymeri7ation with UV light is difficult unless extinction coefficients of monomers at irradiation wavelengths are sufficiently low. Reflection and scattering of U V light make it impossible to determine quantum yields of polymers. The advantage of U V light is selective excitation by choice of irradiating wavelengths.This chapter gives a comparison of the inherent reactivities of a series of crystalline diethynylbenzene derivatives in solid-state polymerization, which is initiated by radicals generated upon irradiation with y rays. Effects of the molecular packing in the crystals on the reactivities are described. The structures of the monomers are shown in Fig. 6. I , whereNumerous studies have been published on the solid-state polymerization of acetylenic compounds. Most of them examine diacetylenes having a wide variety of substituents.2' The polymeri7ation of the diacetylenes has been interpreted by a typical lattice-controlled mechanism. Crystalline 1,4-diethynylnaphthalene and its analogs including 1,4diethynylbenzene (1) are also known to polymerize when irradiated with UV light.') One of the ethynyl groups participates in the polymeriiation resulting in conjugated polyene backbones having ethynyl groups as pendants. 1,4-Diethynylbeni-ene is regarded as the simplest acetylenic compound that is crystalline at room temperature. Various crystalline diethynylbenzene derivatives, which are dimethyl-, dimethoxy-, or methylmethoxysubstituted bis(3-acetoxy-1 -propynyl)benienes (2-8), were synthesi~ed by procedures in the l i t e r a t~r e .~) The monomer crystals were sealed in Pyrex tubes under vacuum and irradiated with y rays from a h°Co source at room temperature. The product formation in the solid-state polymerization was correlated to the molecular packing in the crystals. When 0.5 M benzene solutions of the monomers were irradiated, there was no difference in the yields and the molecular weight distributions of the products among the monomers. R = CH20COCH1.

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