References of "Molecular Crystals & Liquid Crystals"
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See detailLiquid Crystals in Novel Geometries prepared by Microfluidics and Electrospinning
Liang, Hsin-Ling; Enz, Eva; Scalia, Giusy et al

in Molecular Crystals & Liquid Crystals (2011), 549

We describe two new techniques of preparing liquid crystal samples and discuss their potential for novel research and applications. Very thin polymer composite fibers func- tionalized by a liquid ... [more ▼]

We describe two new techniques of preparing liquid crystal samples and discuss their potential for novel research and applications. Very thin polymer composite fibers func- tionalized by a liquid crystalline core are realized by coaxial electrospinning of a polymer solution surrounding the liquid crystal during the spinning process. The re- sulting fiber mats exhibit the special properties and responsiveness of the liquid crystal core, e.g. temperature dependent selective reflection when a short-pitch cholesteric is encapsulated. In the second approach an axisymmetric nested capillary microfluidics set-up is used to prepare liquid crystalline shells suspended in an aqueous continuous phase. The spherical geometry of the shell imposes specific defect configurations, the exact result depending on the prevailing liquid crystal phase, the director anchoring conditions at the inner and outer surfaces, and the homogeneity of the shell thickness. With planar director anchoring a variety of defect configurations are possible but for topological reasons the defects must always sum up to a total defect strength of s = +2. Homeotropic anchoring instead gives a defect-free shell, in contrast to a droplet with homeotropic boundary conditions, which must have a defect at its core. By varying the inner and outer fluids as well as the liquid crystal material and temperature, the defect configuration can be tuned in a way that makes the shells interesting e.g. as a versatile colloid crystal building block. [less ▲]

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See detailDielectric investigations of a chiral monomer and side chain polymer
Gouda, F.; Kutub, Abdul A; Fodor-csorba, K. et al

in Molecular Crystals & Liquid Crystals (2000), 352

The dynamics of different collective and non-collective modes in a chiral liquid crystalline monomer and its side-chain polymer have been studied by dielectric spectroscopy. The monomer system enabled us ... [more ▼]

The dynamics of different collective and non-collective modes in a chiral liquid crystalline monomer and its side-chain polymer have been studied by dielectric spectroscopy. The monomer system enabled us to study the temperature dependence of the dielectric permittivity when crossing the transition from the SmA* phase directly to the crystal phase. Although the polymer system has a SmA* to SmC* transition, we found that the temperature dependence of the dielectric permittivity is radically different from the normally observed behaviour in these phases. The contributions from the soft and Goldstone modes, respectively, are extremely low, a result which is related to the very low value of the spontaneous polarization of the material. At lower temperatures in the SmC* phase, a very weak dielectric absorption located around 50 kHz is observed and discussed in terms of the liberational motion of side chains around the polymer main chain. [less ▲]

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See detailElectrooptic and dielectric spectroscopy measurements of binary chiral-dopant antiferroelectric mixtures
Parghi, D. D.; Lagerwall, Jan UL; Heppke, Gerd

in Molecular Crystals & Liquid Crystals (1999), 351

Recent examinations on binary chiral-dopant antiferroelectric liquid crystalline mixtures revealed an unusual switching behaviour. In order to investigate the switching processes that take place in the ... [more ▼]

Recent examinations on binary chiral-dopant antiferroelectric liquid crystalline mixtures revealed an unusual switching behaviour. In order to investigate the switching processes that take place in the mixtures, both in the bulk and as influenced by surfaces, further electrooptic and dielec- tric spectroscopy studies have been carried out on two model binary mix- tures in the induced SmA*, SmC* and SmCA* phases. The dielectric spectra feature the different modes typical for these phases, but of varying purity, indicating a more complex phase behaviour than expected. The electrooptic behaviour in the antiferroelectric phase varied from clearly antiferroelectric to near hysteresis-free switching directly between ferro- electric states. We conclude that the phase sequence, and consequently switching behaviour, is a function of both the type of dopant used and of the strength of the surface interactions (cell thickness). In thin cells syn- clinic (ferroelectric) ordering appears to be favoured. [less ▲]

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