Langmuir 1996, 12, 3365
3365
Comments Comment on “Surface Pressure-Induced Layer Growth of a Monolayer at the Air-Water Interface” 1
We wish to comment on the paper “Surface PressureInduced Layer Growth of a Monolayer at the Air-Water Interface”.1 In this paper, the authors reported a phase transition in Langmuir films of liquid crystal (LC) and cadmium stearate (SA). They concluded from the surface pressure-area isotherms, X-ray diffraction pattern, and UV-vis absorption spectra that ordinary mixed monolayers form at 25 mN/m while at 40 mN/m the formation of supermonomolecular layers proceeds which can be described as segregated bilayers containing an island LC monolayer and a uniform SA monolayer. Some years ago we already observed similar phenomena in mixed layers of amphiphilic squarylium dye and cadmium icosanoate and analyzed the structures using similar techniques.2-4 We arrived at similar conclusions and employed the same term supermonomolecular layers to describe the special layers observed at 40 mN/m. The model structure A in Figure 1 was concluded out of four candidates using UV-vis absorption spectra of specially fabricated LB films: the squarylium dye can be squeezed out under or above the monolayer of cadmium icosanoate, and the alkyl chains of the dye can be directed in an upward or downward direction. The authors suggest a model corresponding to structure A though there are four candidates shown in Figure 1. For a detailed determination of the supermonomolecular structure our method could be essential. (1) Fang, J. Y.; Uphaus, R. A. Langmuir 1994, 10, 1005. (2) Kawabata, Y.; Sekiguchi, T.; Tanaka, M.; Nakamura, T.; Komizu, H.; Honda, K.; Manda, E.; Saito, M.; Sugi, M.; Iizima, S. J. Am. Chem. Soc. 1985, 107, 5270. (3) Kawabata, Y.; Sekiguchi, T.; Tanaka, M.; Nakamura, T.; Komizu, H.; Matsumoto, M.; Manda, E.; Saito, M.; Sugi, M.; Iizima, S. Thin Solid Films 1985, 133, 175. (4) Matsumoto, M.; Nakamura, T.; Tanaka, M.; Sekiguchi, T.; Komizu, H.; Matsuzaki, S. Y.; Manda, E.; Kawabata, Y.; Saito, M.; Iizima, S.; Sugi, M. Bull. Chem. Soc. Jpn. 1987, 60, 2737.
S0743-7463(95)00540-3 CCC: $12.00
Figure 1. Four candidates for a supermonomolecular structure at the air-water interface. Structure A is the most plausible one for squarylium-cadmium icosanoate systems.
M. Matsumoto,* M. Tanaka, and E. Manda
National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305, Japan T. Nakamura
Research Institute for Electronic Science, Hokkaido University, Sapporo 060, Japan M. Sugi
Faculty of Engineering, Toin University of Yokohama, 1614 Kurogane-cho, Aoba-ku, Yokohama 225, Japan Received October 30, 1995 In Final Form: February 27, 1996 LA950540N * To whom correspondence should be addressed. Telephone: +81-298-54-4586. Fax: +81-298-54-4669. E-mail: mmatsumoto@ ccmail.nimc.go.jp.
© 1996 American Chemical Society
