Smectic A: cholesteric phase transition investigated by small angle X-ray diffraction and viscosity measurements

AUTOR(ES)

Duarte, E. L., Itri, R., Sampaio, A. R., Simões, M., Palangana, A. J.

FONTE

Brazilian Journal of Physics

DATA DE PUBLICAÇÃO

2002-06

RESUMO

We have studied the in influence of the mean molecular length on the nature of the cholesteric (N*) – smectic A (A) liquid crystal phase transition for thermotropic compounds of cholesteryl myristate (C14), cholesteryl nonanoate (C9), and binary mixtures of C14 – C9 and cholesteryl caproate (C6) phase (dA), the mean molecular length () in the N* domain, and the correlation length (epsilon), as well as changes along the N* – A phase transition, were determined from the X-ray diffraction data. The results show a decrease in A phase domain and an expansion of the N* – domain as the mean molecular length is diminished. Such effect induces a second order A – N* phase transition for a particular mixture of 63.1 mol% of C9 and 36.9 mol% of C6, evidenced by viscosity measurements in good agreement with previous density data.

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