The mechanism of polymer alignment of liquid crystal materials.
01 January 1987
Smectic and nematic liquid crystal materials can be homogeneously aligned by buffed thin films of appropriate polymers. We propose that the buffing process orients the polymer's molecular chains in a manner similar to cold-drawing of bulk polymer samples. Experimental verification of this theory is obtained by measuring buffing-induced birefringence in thin films of various polymers coated on glass. Further experiments established that the oriented state of the polymer chains, and not scratching or grooving of the surface, acts on the liquid crystal material to produce alignment. Crystallinity of the oriented polymer is found to be necessary for alignment to occur. A picture of alignment is presented in which the formation of a liquid crystal phase on the crystalline oriented polymer surface is analogous to the epitaxial growth of conventional solid crystals.