Cholesteryl oleyl carbonates

Polymerization of MMA both thermally and pho-tochemically in the ordered media, cholesteryl oleyl carbonate and cholesteryl 2-ethylhexyl carbonate, were studied in the presence and absence of cobalt tetraphenylporphyrin. The percentage conversion and molecular weight were lowered in the presence of CoTPP for thermal polymerizations. In photopolymerizations, the percentage conversion was high and the molecular weights were low.129... 

Pollmann and Stegemeyer investigated the effect of pressure on the pitch of cholesteryl oleyl carbonate (COC) mixed with cholesteryl chloride and found that the pitch increases very rapidly with pressure, the effect being more pronounced the greater the concentration of COC. This appears at first quite surprising, but, in fact, the explanation is straightforward. We have emphasized that the pitch diverges as the temperature... 

FIGURE 3.2 (See color insert following page 14-20.) Misdbilit)r test between the chiral nematic LC induced by (R)- or (S)-PCH506-Binol and the standard LC, cholesteryl oleyl carbonate of counterclockwise (left-handed) screw direction. 

Figure 2.10 Reflection CD spectra of the cholesteryl oleyl carbonate and the N -LCs induced by (R)-D-2 and (5)-D-2. (R)-N -LC PCH302 PCH304 (R)-D-2=100 100 2 (mole ratio). (5)-N -LC PCH302 PCH304 (5)-D-...

To observe them, we used mixtures of cholesteryl oleyl carbonate, cholesteryl nonanoate, and cholesteryl chloride. The ratio of cholesteryl oleyl carbonate to cholesteryl nonanoate was unity by weight in all our mixtures, but the concentration of cholesteryl chloride varied for different phase-matching conditions as listed in Table II. Figure 3 shows, from our measurements, the pitch as a function of the concentration of cholesteryl chloride at 20 and 40 C. The temperature variation of the pitch between 20 and 40 "C can be crudely estimated from the two curves in Fig. 3. The sample used to observe the 12th phase-matching condition was a mixture of cholesteryl chloride and cholesteryl myris-... 

The effects of manufacturing temperature and store conditions on drug permeability across cholesteryl oleyl carbonate (COC)-embedded membranes are investigated. 

The time constant of ordinary cholesteric materials is in the order of 0.1 s. For example, for cholesteryl nonanoate it is 0.1 s and for cholesteryl oleyl carbonate 0.2 s. These response times do not indicate a limitation if the materials are to be observed by eye motion pictures at 64 frames/s have been successfully made and information determined from single frames. 

The cholesteric range of cholesteryl oleyl carbonate increases with pressure. There is evidence of a tricritical point. In the case of methoxy- and ethoxybenzoic acid a pressure-induced nematic and a smectic phase are observed. 

The use of cholesteric liquid crystals for thermography was reviewed some years ago by Elser and Ennulat [4], and more recently in the commercial literature of Hallcrest [5]. Amongst the substances with the largest temperature coefficient are cholesteryl oleyl carbonate [6] and 5-cholesteryl esters... 

Figure 19. Selectively reflected light as a function of wavelength for the chiral nematic cholesteryl oleyl carbonate at different temperatures (a) 20.68 °C, (b) 20.55 °C, (c) 20.44 °C, and (d) 20.5 °C (redrawm from [9]).

Figure 23. Pressure dependence of the selective reflection maxima for different cholesteryl oleyl carbonate (COC) and chloride (CC) mixtures. Compositions (by weight) are (a) COC CC 74.8 25.2 and (b) COC CC 80.1 19.9 (data adapted from [99]. (One bar equals 10 N m . )...

Typically, ORP decreases with increasing wavelength. For example, in quartz ORP varies between 17 and 49, in AgGaS2 between 430 and 950 (in units of degree/mm), and in the liquid crystal cholesteryl oleyl carbonate it varies between 167 and 4167. 

Field-induced phase change Cholesteric > nematic Scattering clear 0 Positive Ae cholesteric added MBBA + PEBAB + cholesteryl oleyl carbonate... 

In this paper we will provide experimental evidence of this mode-coupling phenomenon in the isotropic phase of cholesteryl oleyl carbonate (COG) an analysis will be given of the temperature and wavelength dependence of the data. 

Nakano and Hirata found that the cisoid/transoid ratio of 1 increased from ca. 0.3 to 0.7 with an increase of [ACN] from ca. 7 x 10 to 7 x 10 Min cholesteric LC (cholesteryl oleyl carbonate, cholesteryl hnolate, and cholesteryl oleate), whereas nematic LC or benzene as the reaction medium did not affect the ratio. These results suggest that the cholesteric LC structure makes the ACN molecules align in a phase-to-phase manner. For dimerization of ACN in the nematic phase, Oh-hashi et al. reported briefly the effect of electric fields on the cisoid/transoid ratio. Upon irradiation (X, > 300 nm) of ACN in nematic LC (4-hexyloxyphenyl 4 -butylbenzoate, LCl), application of an electric field up to 5 kV cm decreased the cisoid/transoid ratio from 0.33 to 0.15. They attributed this effect to the preferred formation of the Ti state of ACN by molecular stirring under dynamic scattering of the nematic phase. 

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