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| Titel: |
New mesogens with cubic phases: hydrogen-bonded bipyridines and siloxane-containing benzoic acids I. Preparation and phase behaviour |
| Auteur: | |
| Verschenen in: |
Liquid crystals |
| Paginering: | Jaargang 27 (2000) nr. 11 pagina's 1457-1462 |
| Jaar: |
2000-01-01 |
| Inhoud: |
Several 4-(oligodimethylsiloxyl)alkoxybenzoic acids and their hydrogen-bonded complexes with 4,4-dipyridyl or 1,2-bis(4-pyridyl)ethane were prepared and their phase behaviour studied by DSC and polarized optical microscopy. The neat acids showed no liquid crystalline phases. The 4,4-dipyridyl complex of 4-(n-heptamethyltrisiloxyl)hexyloxybenzoic acid (Si3C6BA) exhibits an optically isotropic, highly viscous liquid crystalline phase below a smectic A phase. The 1,2-bis(4-pyridyl)ethane complex of Si3C6BA also shows an optically isotropic liquid crystalline phase above its smectic C phase. Its behaviour is similar to that of the well known cubic D phase found in 4-n-alkoxy-3-nitrobiphenyl-4-carboxylic acids. In the hydrogenbonded mesogens studied herein, the cubic phase appears to assemble spontaneously in order to take account of the chemical incompatibility between the siloxane moiety terminating the H-bonded complex and the stiff aromatic cores. The transition temperatures of the cubic phases in these materials is around 100oC, hence they are amenable to a variety of physical measurements. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 64 van 131 gevonden artikelen
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