Smetic

Fig. 10.14 a) SEM of three smetic domains I, II and III of p-FeOOH crystals. In domain I the crystals stand upright so that only the ends are visible, A/hereas in domains II and III, only the sides of the crystals are visible, b) SEM of domain I. c) Schematic figure of the arrangement of crystals in the three domains (Reprinted from Maeda Maeda, copyright 1996, A/ith permission and Courtesy, H. Maeda). 

FK5.6.I9 Schematic representation of the structural formation and order-disorder transition for photoactive LBK showing (A) the compressed monolayer on the water surface with densely packed chromophore side chains oriented into the gas phase and the polymer backbone facing the water surface, and (B) LBK transfer from the water to a solid support, resulting in well-ordered smetic-tike (bilayered) multilayer assemblies. (C) After phcnoinduced trars to cts isomerization, a largely disordered struaure is obtained and the layered structure is completely lost (reproduced from reference 72 with permission from Wifey-VCH). 

An exception is thus liquid-crystalline materials in a nematic or smetic state (Ref. 18). 

Aerosol reactors are used to synthesize nano-size particles. Owing to their size, shape, and high specihc surface area, nanoparticles can be used in a number of applications such as in pigments in co.smetics, membranes, photo-catalytic reactors, catalysts and ceramics, aitd catalytic reactors. 

PPV-b-PS made by anionic polymerization, exhibits the same lamellar morphology observed with copolymers made by ATRP. This result confirms the good architecture control that CRP can provide for these copolymers. This study also confirms the unique transition between ordered lamellae and isotropic phase with the coil volume fraction. However, a transition between nematic and smetic C phases in the PPV lamellae has been also shown. This behavior is characteristic of a weakly segregated system. 

Optical investigations of smetic liquids indicated a behaviour of uniaxial or biaxial crystals depending on the special type of material. They are usually positive birefringent, which means that with transmitted light the ordinary beam has a lower refractive index. The nematic liquid is optically positive. 

The problem of identifying phases in the area between highly-ordered, smetic liquid crystals and condis crystals is well recognized and often only solvable when a complete motional, structural, and entropic analysis is available. 

Leupke, N. P. (t985). Hen s egg chorioallantoic membrane te.st for irritating potential. Food Co.smetic Toxical, 23, 287-29L... 

McDonald, T. O., Baldwin, H. A., and Beasley, C. H. (1972). Slit-lamp examination of experimental animal eyes. I. Technique of illumination of the nomial animal eye. /. Soc. Co.smetic Chemi.sts 24, 163-180... 

Abbreviations K, crystal Sa, smectic A i, isotropic. No distinct DSC peaks associated with the phase transition between the crystalline phase and smetic A phase was observed. ... 

Aiitanolamides are prepared from the reaction of fatty acids with mono-or dieihanolamide. They are used as foam stabilizers and thickeners in co.smetic products intended for the cleansing of the skin and scalp. They have not found an irnportam place in the pharmaceutical industry (37). 

Smectic elastomers, due to their layered structure, exhibit distinct anisotropic mechanical properties and mechanical deformation processes that are parallel or perpendicular to the normal orientation of the smectic layer. Such elastomers are important due to their optical and ferroelectric properties. Networks with a macroscopic uniformly ordered direction and a conical distribution of the smectic layer normal with respect to the normal smetic direction are mechanically deformed by uniaxial and shear deformations. Under uniaxial deformations two processes were observed [53] parallel to the direction of the mechanical field directly couples to the smectic tilt angle and perpendicular to the director while a reorientation process takes place. This process is reversible for shear deformation perpendicular and irreversible by applying the shear force parallel to the smetic direction. This is illustrated in Fig. 2.14. 

Ahn et al. reported [62] preparation of a smetic hquid crystalline elastomer with shape memory properties. Shape memory polymeric materials can recover their equilibrium, permanent shapes from nonequilibrium, temporary shapes as a result of external stimuli, like heat or light. Such materials have apphcation in medical practice. Main-chain polynorbomenes were linked with three different side-chains, cholesterol, poly(ethylene glycol), and butylacrylate. 

While initiator A (t-butyl) leads to polymers with a reentrant nematic behaviour, Figure 2b, the polymer from the "hexa-fluoro type B (Figure 2c) shows a typical and stable smectic phase with a prolate morphology of the main chain. A prolate phase (typical for smetic phases) is entered first which finally changes to a nematic behaviour in the range of 75 °C. The Ru-initiator finally leads to a high trans atactic polymer (Figure 2a). 

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