This paper examines the liquid crystalline blue phases of mixtures of a readily available chiral system (consisting of cholesteryl nonanoate and cholesteryl benzoate) with various proportions of a low molecular weight and low polydispersity polymer. By observing the textures of samples using polarizing optical microscopy as they are heated from the chiral nematic through the blue phase and into the isotropic liquid phase, the temperature range where the blue phase of these mixtures is stable is measured as a function of polymer volume fraction for several molecular weights of polystyrene and poly(methyl methacrylate). The mixtures with polystyrene showed a blue phase stability range of up to 12 K, one of the largest measured on heating, and this range varied smoothly as a function of polymer volume fraction. The dependence of the range on the polymer volume fraction and molecular weight could be captured well by a theoretical model based on the Flory-Huggins and Maier-Saupe theories.

Previously unstudied dibenzoindolo[3,2-b]carbazoles have been prepared by two-directional, phase tag-assisted synthesis utilizing a connective-Pummerer cyclization and a SmI2-mediated tag cleavage-cyclization cascade. The use of a phase tag allows us to exploit unstable intermediates that would otherwise need to be avoided. The novel materials were characterized by X-ray, cyclic voltammetry, UV-vis spectroscopy, TGA, and DSC. Preliminary studies on the performance of OFET devices are also described.

A theoretical method is proposed for modelling phase transitions and phase ranges in a multi-component liquid crystalline mixture where the liquid crystal structure is distorted and defects are formed. This method employs the Maier-Saupe and Kobayashi-McMillan theories of liquid crystalline ordering and the Flory-Huggins theory of mixtures. It builds on previous work on mixed systems that can form smectic-A and nematic phases by incorporating "distortion factors" into the expression for the local free energy of the mixture, which account for the effects of a deviation of the liquid crystal structure from the uniform nematic and smectic-A states. The method allows a simple description of chiral defect phases such as the blue phase and the twist grain boundary phase. In a previous work, it was shown that a model of the blue phase along these lines could effectively explain the observed effect whereby an added guest compound can stabilize the phase by separating into the high energy defect regions of the structure. It is shown here that with the correct choice of guest material a similar effect could be observed for the twist grain boundary phase.

Artículo de publicación ISISin acceso a texto completoA small fraction of an acrylate liquid crystalline monomer (<= 5%) is mixed into nematic and smectic liquid crystalline phases, and polymerised through the application of a voltage (electropolymerisation). Polarising optical microscopy reveals that the textures during polymerisation are templated through stabilisation via the forming polymer. During polymerisation in the nematic phase, the director can be observed to gradually reorient into the field-on state. Scanning electron microscopy reveals rope-like and corrugated structures of a distinctive periodicity (500-750 nm). Quite different polymer structures are formed by electropolymerisation in the smectic phase, such as micron-scale worm-like objects that agglomerate reversibly as the temperature changes.Conicyt Fondecyt Project 1130187 NowNano Progra

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