Poly-y-alkyl-L-glutamates

From the viscosity measurements in dichloroacetic acid the molecular weights of polyglutamates were estimated. The solutions were prepared by weighing the polymer and solvent in a stoppered bottle. After shaking slowly on a magnetic stirrer for long time, the solutions were put carefully into the cell, which was having parallel sides 2mm apart. Then the top of the capillary of the cell was sealed to prevent the 

Dilatometric measurements were carried out using Hg as a confining liquid, which was transferred into the dilatometer after solidifying the sample solution by liquid nitrogen. CD spectra, were measured with JASCO ORD/UV-50 over the region from 220 to 300nm. 

The time required to arrive at equilibrium varied from one to several hours. The solvents used here were purified by standard methods. 

Recently DuPre et al reported that, S increases linearly with temperature rise. Qualitatively, their results are consistent with ours. However, the time required to reach the equilibrium pitch, varied with temperature, the concentration of polymer, and also the thermal history. For PBLG solution in dichloro-ethane (EDC), which concentration is 0.12 vol/vol, the variation of pitch with time was measured at a constant temperature by T-jump method. Fig. 1 shows the time dependence of cholesteric pitch by the T-jump method from -2°C to +30°C, 40°C and 50°C respectively. It is clear that the time required to arrive at the equilibrium pitch is shorter at higher temperature but is still over several hours. Therefore, the equilibrium pitch must be measured after prolonged aging at each measuring temperature. It was found that the 

In order to obtain the relationship between S and the concentration C, a double logarithmic plot of S against C at each temperature was made as shown in fig. 4. It can be seen that log S is proportional to log C and, its slope n is an increasing function of temperature, characteristic of the specimens used. 

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