Formation of a Defect Lattice in Electroconvection of Nematics
by N. Oikawa, Y. Hidaka and S. Kai
submitted to Phys. Rev. E

Conventional defect chaos ( Quick Time movie (10.6MB) played in 5.6 times speed )
Defects glide over a wide area.
f = 300 [Hz] ( f / fc = 0.29 )
epsilon = 0.35
Image width : 479 [micron]
Image height : 486 [micron]

Defect chaos with abnormal rolls ( Quick Time movie (9.7MB) played in 5.6 times speed )
Defect motion is suppressed by the "cage effect".
f = 670[Hz] ( f / fc = 0.65 )
epsilon = 0.25
Image width : 479[micron]
Image height : 486[micron]

epsilon = (V²-V_c²) / V_c² : normalized voltage for the convection
f : frequency of the applied voltage
fc ~ 1036[Hz] : the critical frequency separating the conductive regime from the dielectric one


< Materials >
p-methoxybenzilidene-p'-n-butylaniline (MBBA)
Electric conductivity of the sample was controlled by using 0.01 wt%-doping of tetra-n-butyl-ammonium bromide (TBAB).

Dielectric constant e and electric conductivity s at T=30[degree] :
e = 4.87
s = 1.19*10^-7[Omega^-1m^-1]

Thickness of the sample : d = 24.5[micron]

Planar aignment in the x-y plane parallel to the glass plates;
the surfaces of the glass plates were rubbed in one direction (the x-direction) after their treatment by polyvinyl alcohol.