Spacer length variations

Kiihnpast. K., Springer, J.. Scherowsky. G., Giesselmann, F. and Zugenmaier, R, Ferroelectric liquid-crystalline side group polymers spacer length variation and comparison with the monomers, Liq. Cry.st., 14, 861-869 (1993). 

A separate study used in-chain spacer length variation to control charge carrier mobihty in a triarylamine-functionahzed polymer [130]. Charge carrier mobUities were controlled over three orders of magnitude simply by varying the number of methylene units between pendant 2,7-bis(phenyl-w-toluylamino)fluorine groups. 

It has to be taken into account that these catalysts are not yet fully developed. Introduction of electron-withdrawing groups is suspected to increase Lewis acidity, which influences activity, and the optimum spacer length may enable formation of chiral polymers, but such variations are synthetically challenging. 

Variation of the spacer length between CMPO groups attached to the 1,3-and 2,4-positions of the calixarene platform did not lead to appreciable improvements, in terms of extraction or selectivity. 

The variations on the spacer module within 29 are available from Dabes-tani s laboratory [89]. The methylene spacer has been systematically extended to the tetramethylene case. As may be anticipated from previous studies on structurally similar aminoalkylaromatic PET systems [90-92], the fluorescence quantum yield (4>f) of the ion-free sensor rises gradually with increasing spacer length as the PET rate drops. Potassium ions cause moderate to small fluorescence enhancements, but the same trend can be discerned in the values, though muted. As usual, protons cause the largest enhancements of all and the ([>f values remain constant across the series since PET has been completely killed off. 

Table 4.4 Variation of pK, with spacer length in macrocycles of type Hm[4n]aneN4m+ (n = 2-4 m = 3 and 4).

Fig. 6. Variation in the Entropy of Clearing with Spacer Length for Polymers 1,2and4inXable 1...

The probes applied in this work are able to detect differences in both the mobility and polarity of the matrix. Selective attachment of the probe to the polymer opens the opportunity to study the behavior of the probe at different points fixed at the polymer. A variation of the spacer length would give selective information about the mobility and polarity, respectively. In general, covalently bonded probes are reasonable tools to examine swollen samples because they cannot be extracted during the swelling procedure. 

Figure 13. Variation of the isotropization temperature Tj with the flexible spacer length n ( with thermal decomposition).

Study of the variation of the spacer length in polyacrylates V-n has shown that the spontaneous polarization increases when the spacer is shortened [21]. This could be... 

KUhnpast, K., Springer, J., Davidson, P, and Scherowsky, G., Spacer length and molecular weight variation on ferroelectric liquid-crystalline polymers. Makromol. Chem., 193, 3097-115 (1992). 

This finding offers the opportunity to tailor the thermal and mechanical properties of the photoconductor without seriously affecting the transport properties. This can be achieved either by variation of the spacer length between the chromophore and the backbone or by variation of the backbone itself A typical example for this group is PVK [12, 32, 34, 35]. Here, the transition from dispersive to non-dispersive transport could be observed [34]. Due to the fact, that the TOP curves have been measured over 10 decades in time, it was possible by means of a numerical inverse Laplace transform [34] to calculate from the measured photocurrent the trapping rate distribution, which is a measure for the density of localized states. 

For an easy variation of the spacer length in mixed SAMs, Schuhmann and Gorton developed a three-step modification procedure (Fig. 9) [121]. 

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