The preparation of optically active poly(isocyanide)s derived from chiral promesogenic monomers is reported. Remarkably, the stereogenic carbon atom in the monomer is able to pass its chiral “information” to the growing polymer backbone which is at least 14 atoms (approximately 16 Å) remote from it. The sense of helical induction in these conformationally rigid polymers is compared to the helical sense of the cholesteric phases, as well as to the helical senses of chiral smectic C phases, induced by the monomers in nematic and smectic C phases, respectively. Both relate to the odd−even rules for chiral sense changes in liquid crystalline phases. The role of noncovalent interactions in the polymerization has been proven by performing the reactions at various concentrations and in different solventsthe chiral induction from monomer to polymer is greatest in most concentrated reactions and in solvents with a balance between high dipolarity−polarizability and low hydrogen bond accepting and cavitational terms, as determined by an LSER analysis.

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Method based on polarized infrared spectroscopy for the determination of the spatial orientation of transition dipole moments of a ferroelectric liquid crystal Appl. Phys. Lett. 83, 389 (2003); 10.1063/1.1586991Polarized infrared spectroscopy and two-dimensional correlation spectroscopy study of molecular structure of ferroelectric liquid crystals with a naphthalene ring AIP Conf.Polarized absorption spectra of 13 nematic liquid crystals (Les) with various conjugations and structures were measured in the spectral range from 185 to 400 nm. These absorption bands represent all the 1T'--~>1T* electronic transitions of these LCs. Resonance wavelength, absorption coefficient, and dichroic ratio of each band were characterized. The contribution of each band to LC birefringence is briefly discussed. Some structural effects on the LC absorption are illustrated. These absorption spectra will also serve as valuable data bases for further theoretical calculations on the band structure of LC molecules. 78 J.

Supercritical fluid extraction (SFE) was used to obtain brewed coffee extracts with an aroma as similar as possible to the original brewed coffee. The optimization of the process operating variables was performed by means of a sequential simplex method whose response was based on the sensorial evaluation of the aroma extracts. Subsequently, the composition of the extracts obtained at the optimal SFE conditions was determined by using a purge-and-trap device coupled to a GC-MS. For comparison, extracts obtained by using liquid−liquid extraction and headspace-solid-phase microextraction were also obtained and analyzed by GC-MS. Keywords: Supercritical fluid extraction; brewed coffee; aroma; simplex method

Treatment with supercritical CO(2) is proposed for deodorizing antioxidant rosemary extracts obtained by steam distillation and Soxhlet extraction. The process conditions have been optimized by applying a Taguchi experimental design with the aim of obtaining, at minimum cost, a product with acceptable antioxidant activity as well as minimum rosemary aroma. Variables were selected for their effects on the selective extraction of the compounds responsible for the residual aroma of the rosemary extract. The optimized method allowed 90% dearomatization; no detrimental effects in antioxidant activity or color of the extracts have been observed after supercritical fluid processing.

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Other metals used for the metallization (Au, Ag, Cu, Sn, etc.), which did not exhibit such strong effects as tellurium, may show these properties when substrate temperatures are used at which desorption and adsorption rates have similar magnitudes. But the melting points of the polymer substrates (413 K and 438 K for HDPE and iPP, respectively) limit the substrate temperatures. ExperimentalUniaxially oriented polymer substrates were prepared by the method of Petermann and Gohil [11]. The commercial polymer granulate was dissolved in xylene (~0.5 wt.-%) at a temperature of 423 K. A few drops of this solution were placed on a preheated glass slide with a temperature well above the crystallization temperature of the polymer in use. The solution was dispersed uniformly and the solvent evaporated. From the remaining molten polymer film, a highly oriented ultrathin polymer film was drawn by a motor-driven cylinder. The thickness of these films is of the order of 100 nm. The thin films were cut into squares, mounted on copper TEM grids, and used for the electron irradiation, metallization, and TEM investigations without further treatment. The TEM images of the metallized polymer films were obtained in the absorption contrast mode. No distinct contrast is visible on the irradiated areas without metallization. The electron-beam irradiation and TEM investigations were performed in a Philips CM200 electron microscope operated at 200 kV. The radiation doses used were estimated from the main plate screen current given by the control unit of the microscope. For writing in the transmission electron microscope, the electron beam was focused to a spot whose diameter depended on the magnification and moved over the polymer sample by the deflection unit of the microscope. The irradiated substrates were subsequently metallized with tellurium in a Balzers BAE080T evaporation chamber at a pressure of~11 0 ±3 Pa at temperatures ranging between 293 K and 393 K. The nominal layer thicknesses and deposition rates were monitored with a quartz crystal oscillating microbalance. The preparation procedure is sketched in Figure 7.