M. Olbrich et al., FLUCTUATIONS ABOVE THE SMECTIC-A-ISOTROPIC TRANSITION IN LIQUID-CRYSTALLINE ELASTOMERS UNDER EXTERNAL STRESS, Europhysics letters, 31(5-6), 1995, pp. 281-286
Using birefringence measurements, we observe for the first time nemati
c as well as smectic fluctuations above the smectic-A-isotropic transi
tion in liquid crystalline elastomers under an external mechanical str
ess. From a mean-field analysis we find that there are temperatures (f
ar above the isotropic-ii transition) for which nematic fluctuations d
ominate as well as a range of temperatures (above and close to this ph
ase transition) where smectic fluctuations are more important. These t
wo regimes are connected by a crossover regime where the coupling betw
een the two types of fluctuations becomes important. We also discuss t
he possibility of a triple point in liquid crystalline elastomers, whe
re an isotropic, a smectic and a nematic phase meet.