Polymer/liquid crystal interfacial

Recently, Crystal (1970) has studied in detail the crystallization of selenium. By application of the Hoffman-Lauritzen (1961) theory of polymer crystallization. Crystal obtains values for the liquid-crystal interfacial tension of selenium of 9.5 ergs/cm for the lateral face and 337 ergs cm for the chain folded face. He also finds e 0.1 to be a valid approximation for this inorganic polymer. 

Synthesis of polymers for liquid crystal interfacial orientation and its evaluation... 

In THE PAST DECADE, IMPROVEMENTS IN infrared spectroscopic instrumentation have contributed to significant advances in the traditional analytical applications of the technique. Progress in the application of Fourier transform infrared spectroscopy to physiochemical studies of colloidal assemblies and interfaces has been more uneven, however. While much Fourier transform infrared spectroscopic work has been generated about the structure of lipid bilayers and vesicles, considerably less is available on the subjects of micelles, liquid crystals, or other structures adopted by synthetic surfactants in water. In the area of interfacial chemistry, much of the infrared spectroscopic work, both on the adsorption of polymers or proteins and on the adsorption of surfactants forming so called "self-assembled" mono- and multilayers, has transpired only in the last five years or so. 

In general, snrfactant is more effective (higher solnbilization) withont an added cosolvent snch as alcohol, because cosolvent or cosnrfactant is such a chemical that its molecules exhibit a substantial presence within the interfacial layers (Bonrrel and Schechter, 1988). However, cosolvents are almost always added (Gary A. Pope, personal communication on Inly 30, 2008) to surfactant formulations to minimize the occurrence of gels, liquid crystals, emulsions or polymer-rich phase separating from the surfactant solution, to lower the equilibration time, and/or to reduce microemulsion viscosity. Usnally, the ratio of surfactant to cosolvent is about 2 to 3. 

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... 

There also exists a need to avoid surfactant aggregate structures such as lamellar liquid crystals which exhibit high viscosity (29-32). System parameters should be such that mixing between the fluids in the surfactant, oil and polymer slugs does not occur. A dispersion of surfactant and oil would form an undesired emulsion, while a dispersion of surfactant and polymer, if incompatible, could lead to phase separation, which would decrease the effectiveness of the process. Other points to take into account are (i) the mass transfer of surfactant to the oil bank can change the interfacial tension, and (ii) surfactant-polymer incompatibility leads to a phase separation, which would reduce the efficiency of the process (30, 31). 

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. 

Surface memory effects refer to phenomena where an initially isotropic surface can be rendered anisotropic in contact witii an anisotropic medium. This anisotropic medium can be a crystal or smectic liquid crystal. It is believed that the surface memory effect arises from the interfacial (smectic liquid) crystal-polymer coupling that leads to a deformed surface. 

Sung SJ, Jung EA, Sim K, Kim DH, Cho KY (2013) Phase separation structure and interfacial properties of lattice-patterned liquid crystal-polymer composites prepared from multicomponent prepolymers. Polym Int 63 214-220... 

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