Network stabilized liquid crystals polymer dispersions

In the past few decades the technological possibilities and interests have boosted research in systems in highly restricted geometries in almost every field of physics — recently down to lengthscales close to or even below the molecular level. In the field of liquid crystals, the importance of electro-optical applications which incorporate ordered liquid materials [1-3] has focused the research on LC systems with high surface-to-volume ratio [4]. In order to provide mechanically stable applications, liquid crystals are dispersed in polymers, stabilized by a polymer network, fill the cavities in porous materials, etc. [5,6]. The major technological interest concerns the scattering, reflective and bistable displays, optical switches, and others. 

The synthesis, characterization and mesomorphic behavior of diacrylates based on polymerized liquid crystals are reported. Several types of polymer stabilized liquid crystal display devices were prepared from the dispersions of low concentration of diacrylates in liquid crystals and subsequently the prepolymers were polymerizaton by ultraviolet radation toorm polymer networks. The morphology stupes show that the orientation of polymer networks induced by the surface treatment of the substrate has led to the preferential liquid crystal alignment... 

Nematic gels are very interesting systems, thus deserving further study. Actually, these systems are being studied experimentally for applications. Examples are polymer dispersed liquid crystal displays are sometimes dispersed not in a polymer, but in a polymer network. Displays by means of the polymer stabilized cholesteric texture change, are also achieved in crosslinked systems. In addition, the chiral smectic phase has been obtained in such systems as well. Other types of liquid crystal gels have been applied or are expected to be applied in such devices. 

H.-S. Kitzerow, Pol mer-dispersed and polymer-stabilized chiral liquid crystals, in Liquid Crystals in Complex Geometries Formed by Polymer and Porous Networks (edited by G.P. Crawford and S. Zumer), Taylor and Francis, London, 1996, pp. 187-220. 

Lahiri T, Pal Majumder T (2012) The effect of cross-linked chains of polymer network on the memory states of polymer stabilized ferroelectric molecules. Polymer 53 2121-2127 Lee K, Suh SW, Lee SD (1994a) Fast linear electro-optical switching properties of polymer-dispersed ferroelectric liquid crystals. Appl Phys Lett 64 718 Lee K, Suh SW, Lee SD, Kim CY (1994b) Ferroelectric response of polymer-dispersed chiral smectic C liquid crystal composites. J Korean Phys Soc 27(1) 86... 

Malik MK, Deshmukh RR (2014) Electro-optics of homogeneously aligned nematic liquid crystals stabilized by a polymer network. Int J ChemTech Res 6 1833-1835 Manohar R, Tripathi G, Singh AK, Srivastava AK, Shukla JP, Prajapati AK (2006) Dielectric and optical properties of polymer-liquid crystal composite. J Phys Chem Solids 67 2300-2304 Mei E, Higgins DA (1998) Polymer-dispersed liquid crystal films studied by near-field scanning optical microscopy. Langmuir 14 1945-1950... 

The continuous phase can be a solid or have some characteristics of a solid. This implies that the structural elements are immobilized, which considerably enhances physical stability of the system. When making such a dispersion, the continuous phase is always liquid, but it can solidify afterwards, e.g., by lowering the temperature or by evaporating the solvent. The liquid can become crystallized, form a glass (Section 16.1), or turn into a gel. Especially the last named situation is frequently encountered in foods. Also the solvent, generally an aqueous solution, in the continuous phase then is more or less immobilized (Section 5.3). If the gel is a classical polymer gel (Section 17.2.2), the polymer molecules provide a continuous network, but do not make up a continuous phase the polymer strands cannot be seen as a structure in which other molecules can be present and diffuse. 

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