Polymer/liquid crystal interfacial interaction

The sensitivity of deuteron NMR to the molecular orientational order and to director field configurations turned out to be extremely useful in studies of liquid crystals confined into snbmicrometer pores. Moreover, the large surface-to-volume ratio of these composite systems render the interfacial and surface phenomena, induced by the liquid crystal-surface interactions, accessible even to an essentially integrative technique like NMR. Since the discovery of polymer dispersed liquid crystals (PDLCs) in 1986 [4], NMR of selectively deuterated liquid crystals was used to discriminate unambiguously among various director structures in cavities, resulting from an interplay between elastic forces, morphology and size of the cavity, and surface interactions. These structures include the escaped-radial, planar axial, planar-polar, and... 

The PDLC system performance depends strongly on the final morphology of the liquid crystal domains dispersed inside the polymer matrix. The size, shape and distribution of liquid crystal domains are generally dictated not only by thermodynamic phase equilibrium, but also by the type of material used and by interfacial interactions [58-62]. 

Smooth substrates include crystal and glass surfaces, and polymer films. The direct influence of such a substrate on the liquid crystal is limited to the molecules in the surface layer and is due to the short-range interaction of these molecules with the substrate (Fig. 4a). Once these microscopic anchoring conditions are known, the configuration of the rest of the liquid crystal (in particular the orientation of the director outside the interfacial region) can be determined from the properties of the liquid crystal regarding propagation of orientational order. 

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