Langmuir-Blodgett films molecular orientation

On a conceptual level, the ideal format for thin-film materials for nonlinear optics is the Langmuir-Blodgett film. Molecularly engineered chrom-ophores with large hyperpolarizabilities can, in principle, be incorporated at high concentration, with well-defined orientations into films having thicknesses defined by molecular resolution. Extremely large resonantly enhanced values of have been reported in LB films several layers thick (30, 3i) thus the considerable promise of this approach is established. 

Crockett R G M, Campbell A J and Ahmed F R 1990 Structure and molecular-orientation of tetramethoxy-tetraoctoxy phthalocyaninato-polysiloxane Langmuir-Blodgett-films Po/yme/ 31 602-8... 

D. Molecular Orientation of Carotene in the Spin-Coated Rim and in the Langmuir-Blodgett Film. . 349... 

Yasuda Y, Sugino H, Toyotama H et al. Control of protein orientation in molecular photoelectric devices using Langmuir-Blodgett films of photosynthetic reaction centers from Rhodopseudomonas viridis. Bioelectrochem Bioenerg 1994 34 135-139. 

FIGURE 8.21. Insoluble monolayer films can, with careful work, be deposited onto solid substrates from the liquid surface. The so-called Langmuir-Blodgett films will usually have alternating molecular orientations (a) first-layer deposition with the head (or tail) toward the solid substrate and (h) the second-layer head-to-head or tail-to-tail in a Y film orientation. Under some conditions it is possible to produce an X film with head-to-tail orientation (c). 

The tip of an atomic force microscope makes a single point contact with a surface. Consequently, understanding tribological behavior becomes intellectually simpler. Friction has been shown to be correlated not with the magnitude of the adhesion between two bodies, but rather with the adhesion hysteresis [6]. Our recent study of a model system, a Langmuir-Blodgett film on mica [7], shows no dependence on adhesion hysteresis, but rather a dependence on molecular orientation [2]. 

Hasegawa, T., Umemura, J. and Takenaka, T. (1993) Infrared external reflection study of molecular orientation in thin Langmuir-Blodgett films. J. Phys. Chem., 97, 9009-9012. 

Hasegawa, T Takeda, S., Kawaguchi, A. and Umemura, J. (1995) Quantitative analysis of uniaxial molecular orientation in Langmuir-Blodgett films by infrared reflection spectroscopy. Langmuir, 11, 1236-1243. 

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