Reductions of the transition temperatures

Fig. 4.6 (A and B) Dependence of the drug-induced reduction of the transition temperature (A 7",) on the amount of chlorphentermine and clofibric acid added. The dissociation equilibrium of the drugs was shifted to the indicated forms by adjusting the pH of the liposome suspension to pH 6 and over pH 9 respectively (A). Dose-effect curves of the uncharged forms (pH 10 and pH 4.5, respectively. Dotted line indicates drug amounts at which morphologic alterations occurred in the liposome suspension (B). (Reprinted from Fig. 2 of ref. 96 with permission from Elsevier Science). (C) Liposomal binding of chlorphentermine and clofibric acid depending on the total amount of drug added to the liposome suspension (mean values of triplicate determinations). Maximum deviation from the mean was 10% of the mean. (Reprinted from Fig. 3 of ref. 96 with permission from Elsevier Science)...

All of these methods can produce a reduction of the transition temperatures without adversely affecting the range of mesophase stability, but the greater part of the literature concerning LC polymers with main chain mesogenic units has been concerned with the use of flexible spacers for this purpose. 

Liquid crystals based on aliphatic isocyanides and aromatic alkynyls (compounds 16) show enantiotropic nematic phases between 110 and 160 °C. Important reductions in the transition temperatures, mainly in clearing points (<100 °C), areobtained when a branched octyl isocyanide is used. The nematic phase stability is also reduced and the complexes are thermally more stable than derivatives of aliphatic alkynes. Other structural variations such as the introduction of a lateral chlorine atom on one ring of the phenyl benzoate moiety or the use of a branched terminal alkyl chain produce a decrease of the transition temperatures enhancing the formation of enantiotropic nematic phases without decomposition. 

Polycondensations of 3,3-bis(chloromethyl)oxetane and a variety of bisphenols were studied using the microwave-PTC technique (Eq. 23) [35]. The results obtained showed the advantages of microwaves in terms of the molecular weights for crystalline polymer, as reflected in higher values of the transition temperature (Tg) and melting point (Tm) but also in reduction of reaction times for all types of structure. 

Fig. 28. Classification of salt effects on the swelling curve. Until now four types of effect have been observed, each of which has different combination of increment or decrement of the transition temperature, induction or reduction of the transition discontinuity, and their combinations...

Reduction of the solution temperature allows transition from steady-state to peak-shaped response simply by way of the marked diminution of D at low temperatures. Figure 16.5 shows slow-scan cyclic voltammograms obtained at two microdisk electrodes as a function of solution temperature. Between -120 and -140°C there is a particularly clear transition for the 25-pm-diameter electrode as the diffusion-layer thickness becomes less than the disk radius. Also illustrated here is the immense decrease in the limiting currents that is seen over this range of temperatures due to the 100-fold decrease in D. 

Finite size effects on the critical temperature for Bose-Einstein condensation of a noninteracting Bose gas conhned in a harmonic trap manifests the reduction of the condensate fraction and the lowering of the transition temperature, as compared to the infinite system [14, 127]. Eor an N particle condensate, the shift of the critical temperature Tc, relative to that for the N by the cluster size scaling relation [14, 127]... 

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