Thermally-induced inversion of the

A similar thermally-induced inversion of the cholesteric sense was observed for the PBLG liquid crystal in benzyl alcohol. In this solution, a gel-like opaque phase coexists with the cholesteric phase at lower temperatures. The opaque phase disappears around 70 °C, where endothermic peaks are observed in the differential scanning calorimetry curve. The value of S below 70 °C remains constant, and then changes with temperature above 70 °C. The compensation occurs at about 103 °C, and the transition from biphasic phase to the isotropic phase is observed above 150 °C in this case. The results are summarized in Fig. 12, where the reciprocal of the half-pitch is plotted against temperature. The sign of 1/S is taken as positive when the cholesteric sense is the right-handed. 

The thermally induced inversion of the cholesteric sense was considered to be related to the intermolecular hydrogen-bond formation of the side chain ester groups of PBLG with m-cresol, since it was first observed in m-cresol solutions. However, our subsequent investigations revealed that the sense inversion also occurs in 1,2,3-trichloropropane(TCP) which does not have any particular functional groups. A similar finding was recently reported in 1,1,2,2-tetrachloroethane. ... 

Toriumi H, Kusumi Y, Uematsu I, Uematsu Y (1979) Thermally induced inversion of the cholesteric sense in lyotropic polypeptide liquid crystals. Polym J 11 863-869... 

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