Liquid crystal-polymer network composites

A new class of liquid crystal/polymer network composite with very small amounts of polymer network (3 Wt%) is described. These composites are formed by photopolymerization of the monomers in-situ from a solution of monomer dissolved in low-molar-mass liquid crystals. Several techniques have proven useful to characterize these polymer networks. This review describes polymer network structure and its influence on electro-optic behavior of liquid crystals. Structural formation in these composites begins with the phase separation of polymer micronetworks, which aggregate initially by reaction-limited, and then by diffusion-limited modes. The morphology can be manipulated advantageously by controlling the crossover condition between such modes, the order of the monomer solution prior to photopolymerization, and the molecular structure of monomers or comonomers. 

RAJARAM ET AL. Liquid Crystal-Polymer Network Composites... 

Electro-Optic Properties of Polymer Stabilized Liquid Crystals. Polymer networks have been used to stabilize many of the liquid crystal display states in various types of displays quite advantageously. In this section, we present some recent work on correlating the material properties of the liquid crystal/polymer network composite to the electro-optic properties of the flat-panel displays specifically cholesteric texture displays (75) and simple nematic birefringent type displays (7(5). 

Hybrid composite materials (HCM) represent the newest group of various composites where more than one type of fibre is used to increase cost-performance effectiveness, i.e., in a composite system reinforced with carbon fibres the cost can be minimised by reducing its content while maximising the performance by optimal partial replacement with an another fibre or by changing the orientations. HCM include nanocomposites [31], functionally gradient materials [32], Hymats (hybrid materials) [33], interpenetrating polymer networks (IPN) [34], and liquid crystal polymers [35]. 

Title Liquid-Crystal Compositions and Polymer Networks Derived Therefrom... 

Morphology of Composites of Low-Molar-Mass Liquid Crystals and Polymer Networks... 

The birefiingence of the polymer network was estimated by measuring the birefringence after replacing the liquid crystal solvent with an isotropic solvent such as octane. The birefiingence of the liquid crystal composite was modeled as follows. The polymer network was assumed to be a square array of parallel fibrils of radius R and order parameter Sp. The order parameter of the liquid crystal solvent was assumed to be equal to that of the polymer network at the interface, and continuously decreasing away from this interface. 

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