STUDY OF THE ORIENTATION OF NEMATIC THIN-FILMS BY THE METHOD OF IR MULTIPLE FRUSTRATED TOTAL-INTERNAL-REFLECTION SPECTROSCOPY

This paper gives estimates of the dichroic ratioof the main IR absorpt ion bands in the multiple frustrated-total-internal-reflection spectra and the order parameter S of thin films of a nematic liquid crystal ( LC) based on cyanobiphenyls (CBs). For planar-oriented CB molecules on an amorphous hydrogenated-carbon (a-C:H) surface, the value of S lies in the interval 0.63-0.68, while the dichroic ratio of the main absor ption bands lies within the limits 4.3-5.3. When the CB films obtained on the surface of a plasma-polymerized layer have a homeotropic struc ture, S = 0.43-0.45. The change of these quantities after storage of t he LC cells and as a result of heating the oriented structure to the n ematic-->isotrope transition temperature is studied. The nature of the observed changes is discussed. (C) 1998 The Optical Society of Americ a.