Polymer liquid crystals alignment

Recently, experimental data of S for various liquid-crystalline polymer solutions have become available. Figure 12 illustrates the concentration dependence of S for three polymer liquid crystal systems (a) PBLG-DMF [92,93], (b) PHIC-toluene [94], and (c) poly(yne)-platinum polymer (PYPt)-trichloro-ethane (TCE) [33]. For systems (a) and (c), with the alignment made by... 

K. Hongladarom, W. R. Burghardt, S. G. Baek, S. Cementwala, and J. J. Magda, Molecular alignment of polymer liquid crystals in shear flows. I. Spectroscopic birefringence technique, steady-state orientation, and normal stress behavior in poly(benzyl glutamate) solutions, Macromolecules, 26, 772 (1993). 

Wu, Y., Demachi, Y., Tsutsumi, O., Kanazawa, A., Shiono, X, and Ikeda, T. Photoinduced alignment of polymer liquid crystals containing azolienzene moieties in the side chain. 1. Effect of light intensity on alignment behavior. Macromolecules 31, 349 (1998). 

Kim, D. Y., Kumar, J., and Tripathy, S. K. Liquid crystal alignment using optically induced surface relief gratings on azo polymer films. Polymer Preprints 1998, 319, pp. 1107-1108. 

M. Sakuragi, T. Seki, Y. Kawanishi, T. Tamaki, K. Ichimura, R. Fukuda, H. Hiramatsu, and K. Fujiwara, Photoregulation of liquid crystal alignment by Langmuir-Blodgett layers of azobenzene polymers, J. Photopolym. Sci. Technol. 4, 279-282 (1991). 

The most important theoretical models for attempting to accoimt for liquid-crystal alignment are the lattice model, introduced by Flory in 1956, and the mean-field model introduced about 1960 by Maier and Saupe. Of these, the former has proved to be more readily applicable to polymers. It is based on the rather obvious idea that, as the number of rigid impenetrable rods in a given volume is increased, they must eventually become aligned approximately parallel to each other, at least in local regions, and it attempts to predict the concentration at which this will tend to happen. In this model there is no specific interaction between the rods except for the short-range repulsive force that corresponds to their mutual impenetrability. 

Ichimura K, 1996. Photoregulation of liquid crystal alignment by photochromic molecules and polymeric thin films. In Shibaev V, editor. Polymers as Electrooptical and Photooptical Active Media. Berlin Springer. 

Kim JY, Kim TH, Kimura T, Fukuda T, Matsuda H. 2002. Surface relief grating and liquid crystal alignment on azobenzene ftmctionalized polymers. Opt Mater 21 627 631. 

Kawatsuki N, Goto K, Kawakami T, Yamamoto T. 2002. Reversion of alignment direction in the thermally enhanced photoorientation of photo cross linkable polymer liquid crystal films. Macromolecules 35 706 713. 

In this Section we will introduce the principles and experimental details of NEXAFS spectroscopy. The focus of the discussion will be on showing that this technique has all the capabilities required to address the origin of liquid crystal alignment on rubbed polymer surfaces. 

In fact it was the understanding within the model of liquid crystal alignment on ion beam irradiated polymer surfaces, which inspired the develop-... 

Molecular Anisotropy and Liquid Crystal Alignment on Rubbed Polymer Surfaces... 

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