Dielectric and mechanical relaxation in isooctylcyanobiphenyl (8*OCB).
J Phys Condens Matter
; 22(23): 235101, 2010 Jun 16.
Article
en En
| MEDLINE
| ID: mdl-21393760
ABSTRACT
The dynamics of isooctylcyanobiphenyl (8*OCB) was characterized using dielectric and mechanical spectroscopies. This isomer of the liquid crystalline octylcyanobiphenyl (8OCB) vitrifies during cooling or on application of pressure, exhibiting the typical features of glass-forming liquids non-Debye relaxation function, non-Arrhenius temperature dependence of the relaxation times, τ(α), a dynamic crossover at T â¼ 1.6T(g). This crossover is evidenced by changes in the behavior of both the peak shape and the temperature dependence of τ(α). The primary relaxation time at the crossover, 2 ns at ambient pressure, is the smallest value reported to date for any molecular liquid or polymer. Interestingly, at all temperatures below this crossover, τ(α) and the dc conductivity remain coupled (i.e., conform to the Debye-Stokes-Einstein relation). Two secondary relaxations are observed in the glassy state, one of which is identified as the Johari-Goldstein process. Unlike the case for 8OCB, no liquid crystalline phase could be attained for 8*OCB, demonstrating that relatively small differences in chemical structure can effect substantial changes in the intermolecular potential.
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Espectrofotometría
/
Compuestos de Bifenilo
/
Vidrio
Tipo de estudio:
Risk_factors_studies
Idioma:
En
Revista:
J Phys Condens Matter
Asunto de la revista:
BIOFISICA
Año:
2010
Tipo del documento:
Article
País de afiliación:
Polonia