Publicação
Smectic A: cholesteric phase transition investigated by small angle X-ray diffraction and viscosity measurements
| 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 (<img src="http:/img/fbpe/bjp/v32n2b/07eq01.gif">) 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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| Autores principais: | Duarte,E. L. |
| Outros Autores: | Itri,R.; Sampaio,A. R.; Simões,M.; Palangana,A. J. |
| Ano: | 2002 |
| País: | Brasil |
| Tipo de documento: | artigo |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | IBICT |
| Idioma: | inglês |
| Origem: | Oasisbr |
| 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 (<img src="http:/img/fbpe/bjp/v32n2b/07eq01.gif">) 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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