|
| << vorige | volgende >> |
Tijdschrift beschrijving
Alle jaargangen van het bijbehorende tijdschrift
Alle afleveringen van het bijbehorende jaargang
Alle artikelen van de bijbehorende aflevering
Details van artikel 12 van 13 gevonden artikelen
| Titel: |
Phase transfer Pd(0)/Cu(I) catalysed polymerization reactions 7. Synthesis and thermotropic behaviour of 1,4-bis[2-(3',3''-difluoro-4',4''-di-n-alkyloxyphenyl)-ethynyl]benzene dimers |
| Auteur: |
Pugh, Coleen Andersson, Sara K. Percec, Virgil |
| Verschenen in: |
Liquid crystals |
| Paginering: | Jaargang 10 (1991) nr. 2 pagina's 229-242 |
| Jaar: |
1991-08-01 |
| Inhoud: |
The symmetrically difluorinated aryl-acetylene dimers, 1,4-bis[2-(3',3''-difluoro-4',4''-di-n-alkyloxyphenyl)ethynyl]benzenes (n = 7-12), were prepared by a one pot phase transfer. Pd(0)/Cu(I) catalysed, three step coupling of 1,4-diiodobenzene with 2-methyl-3-butyn-2-ol and the appropriate 1-bromo-3-fluoro-(4-n-alkyloxy)benzene. All members of the series display enantiotropic nematic and smectic C phases as well as an additional smectic mesophase in the sequence C-S-SC-N-I. The textures observed by polarized optical microscopy strongly support identification of the second smectic phase as a SE mesophase. The SC temperature window increases as the length of the n-alkyloxy substituent increases, whereas the stability of the nematic and SE temperature windows decrease. In these fluorinated dimers, destabilization of mesomorphic behaviour by lateral fluorine substitution is compensated by stabilization due to the large length to breadth ratio of the mesogen, such that melting and crystallization are depressed more than isotropization when compared to the non-fluorinated dimers. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 12 van 13 gevonden artikelen
| << vorige | volgende >> |