Optical dichroism potential

Incorporation of chiral units into polymers generates optically active polymers.27 Two types of optically active polymers could be obtained according to where the chiral units reside optically active polymers with chirality derived from chiral side chains and optically active polymers with chirality derived from tire chiral main chain. The circular dichroism (CD) measurement of 32, an optically active polymer with chiral side chains, showed that the chiral substituents have induced main-chain chirality. The induced main-chain chirality disappeared at higher temperature and appeared upon cooling. This type of chiral conjugated polymer is potentially useful in reversing optical recording28 ... 

Ross WN, Salzberg BM, Cohen LB et al (1977) Changes in absorption, fluorescence, dichroism and birefringence in stained giant axons optical measurement of membrane potential. J Membr Biol 33 141-183... 

The electronic absorption characteristics of chromophores within potential gela-tors can provide an important experimental monitor of the microscopic environment in which they reside. This is especially true when the information includes optical rotatory dispersion (ORD) and circular dichroism (CD) data for potential gelalors that arc chiral. Dichroism relates to the absorptivity difference between the two components of circularly polarized light, w-hich constitutes the incident plane of linearly polarized light as described by the Kronig-Kramers transform. The intensity of UV/vis absorption depends on corresponding quantum transition. The wavelengths at which nonzero circular dichroism may be observable in the CD spectrum can be discerned from the shape of the absorption bands. The... 

Rydberg transitions and ionization potentials Optical Rotatory Dispersion (o.r.d.) and Circular Dichroism (c.d.). ... 

Abbreviations NMR, nuclear magnetic resonance PMR, proton magnetic resonance ppm, parts per million TMS, tetramethylsilane MW, molecular weight EPR, electron paramagnetic resonance CD, circular dichroism ORD, optical rotatory dispersion HiPISP, high potential iron-sulfur portein. 

One of the most interesting photoresponsive properties of azo polymers is the photoinduced birefringence and dichroism (Xie et al., 1993). The photoinduced anisotropy is caused by the disparity of the repeated trans-cis isomerization of azo chromophores under linear polarized light irradiation. The most efficient excitation occurs in the polarization direction, which can force the chromophores to continually change their orientation and to be eventually stabilized at the direction perpendicular to the polarization (Natansohn and Rochon, 2002). The effect shows potential applications in areas such as reversible optical data storage, optical switching and sensors. 

In this chapter we shall only be concerned with electro-optic and thermo-optic switching effects in thermotropic side-chain polymer liquid crystals. We will consider briefly the synthesis and structure of such compounds and show how the nematic, cholesteric and smectic phases arise. Since the optical properties of each of these phases are different, and may be altered depending on alignment within the phase, each gives rise to different electro-optic effects. If these are coupled to the use of dye additives or substituents, then it will be realized that a wide range of electro-optic devices based on dichroism or fluorescence as well as birefringence or scattering power may be fabricated. These will be considered and discussed in terms of their performance and potential applications. Finally, possible uses of polymer-low molar mass liquid crystal solutions will be considered in terms of electro-optic device applications. 

The ultraviolet spectra of crowded olefins and substituted butadienes have been studied the sign of the Cotton effect has been related to the chirality of a series of w-molecular complexes of olefins with tetracyanoethylene the sign of the chiral-optical effects of non-planar heteroannular cisoid dienes is opposite to that predicted from the diene rule. Studies of linear and circular dichroism in mono-olefins and magnetic circular dichroism of conjugated olefins have been made, and the experimental ionization potentials of fourteen alkenes have been correlated with the inductive effects of substituents. ... 

Raman optical activity (ROA) or, more precisely, spontaneous vibrational Raman optical activity scattering is, like vibrational circular dichroism (VCD), a spectroscopic method that directly probes the chirality, or handedness, of molecular vibrations. ROA and VCD therefore have an obvious stereochemical potential. That such phenomena could yield structural information not otherwise available was realized long before their measurement became feasible and the first observations of ROA and VCD date back only a quarter of a century. For ROA, measurement was preceded by a detailed theoretical analysis and, perhaps inevitably so in view of the experimental difficulties, some false claims of its observation. 

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