Side group 284 INDEX

Finally, a side group index SG was defined as the fourth power of the fraction (N - NBB)/N of the vertices of the hydrogen-suppressed graph of the repeat unit that are in its side groups ... 

In order to assess the orientational stability of the poled state, the temperature dependence of the dipole mobility of the side groups was examined through dielectric relaxation measurements. (13) No low temperature relaxation below Tg was observed in the frequency range studied (100 Hz-100 kHz). In addition, the dielectric constant was approximately equal to the square of the refractive index, indicating that below T only electronic and no significant orientational contributions to the dielectric displacement are present. Thus, it was expected that a given orientational state of the ensemble would be stable at temperatures significantly below Tg. 

Some of the latest work on high refractive index polyphosphazenes makes use of polymers that contain both fluoroalkoxy and di- or tri-chlorophenoxy side groups.261 These amorphous glasses are thermally stable up to 400 °C, show a large variation of refractive index with temperature, and refractive index values that vary from 1.39-1.56 depending on composition. Thus, they are candidates for uses in thermo-optical switching devices. 

PMPS films (6400 amu by GPC) synthesized by Wurtz have been used as pattern masks in UV lithography.56 UV absorption in air by the material led to a large decrease of the refractive index from 1.70 to 1.56 as a result of the photodecomposition accompanying the cleavage of the Si backbone and the elimination of the ir-conjugation moieties of the side groups. 

Optical Materials. The polyphosphazene skeleton is electron-rich, which means that it provides a refractive index increment compared to conventional saturated organic backbones. In addition, the macromolecular substitution synthesis aUows highly unsaturated organic side groups to be linked to the skeleton in ways that allow the refractive index, the color, the liquid crystalline, and nonlinear optical characteristics of the polymer to be finely tuned. Thus, the use of these polymers in opto-electronic (photonic) switches and lens systems is a subject of growing interest. 

Fukudome, M., Kamiyama, K., Kawai, T., and Irie, M, Photochromism of a dithienylethene having diphenylamino side groups in the bulk amorphous phase25 refractive index change of an amorphous bisbenzothienylethene. Chem. Lett. 70, 2001. 

Define a locally anisotropic property as a property whose value is highly sensitive to whether each atom or bond is in the chain backbone or in a side group. By contrast, while the value of a globally anisotropic property may be very sensitive to the overall orientation of the polymer chains, it is somewhat less sensitive to the precise location of any given atom or bond in the structure. For example, the refractive index is a globally anisotropic property. The stress-optic coefficient, whose value depends both on the refractive index and on the difference in the polarizability of a polymer chain segment parallel and perpendicular to the chain, is a locally... 

The most important index was SG. It had a correlation coefficient of 0.8337 with o, so that there is a fairly strong correlation between o and increasing side group size as SG is the, fourth power of the fraction of the vertices of the hydrogen-suppressed graph that are in side groups. 

The refractive index modulation of the block copolymer lb carrying cyano-azobenzene side-groups is more than twice that of the methoxy-substituted block copolymer 14. In addition, lb exhibits a much higher sensitivity than 14. This is just a consequence of (7), in which the sensitivity increases with the refractive index modulation. Furthermore, 14 exhibits a continuous decay after the writing laser is turned off, similar to that shown in Fig. 27. Block copolymer lb, in contrast, even shows an increase by 15% within a few hours, and the refractive index modulation is stable for years. In this case, the so-called post-development is not due to a different morphology as discussed above. Rather, the liquid crystalline character of the... 

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