Pitch-band

When linearly polarized light passes through a cholesteric phase having helical directors wound in a right-handed helix, RCP is scattered selectively, and the sactter-ing results in eL < eR, i.e., Ae < 0. Thus, the pitch-band CD with minus sign corresponds to a right-handed helical sense in the mesophase. 

The Relationships Between the ICD Signs and the Sign of the Pitch-Band CD... 

For CD observation, pyrene-2-carboxylic acid methyl ester was dissolved into a cholesteric mixture of 55.5 mole percent of cholesteryl nonanoate and 44.5 mole percent of cholesteryl chloride, which exhibited a pitch band CD with plus sign... 

Recently, we also found that several types of chiral smectic C phases composed of achiral and chiral aromatic esters exhibit a large shift of their pitch band CD, depend-... 

Fig. 26a and b. Temperature dependence of CD spectra of a colored PBLG film a cholesteric pitch bands around 500 nm b LCICD of the side-chain phenyl groups... 

Plate 7. Pitch bands associated with the TGBA phase at a temperature near to the clearing point of (S)-l-methylheptyl 4 -(4-n-tetradecyloxyphenylpropioloyloxy)biphenyl-4-carbox-ylate (xlOO)... 

These two different structures can be easily differentiated by observing the selective reflection at oblique incidence [12]. Namely, a so-called full pitch band is observable in the ferroelectric phase at the wavelength of twice of that of the normal selective reflection band, while the full pitch band must be absent in the antiferroelectric phase. This is actually the case based on the first experimental evidence, as shown in Figure 9.6 [12], in which no full... 

A final application that should be mentioned is the use of pitch band measurements in chiral-solute-induced twisted nematic phases to determine the enantiomeric purity and structures of chiral (solute) molecules [339, 340]. It has been shown that the ability of a chiral solute to twist a nematic phase (the so-called twisting power, p) can be defined... 

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