Capacitance and optical studies of elastic and dielectric properties in an organosiloxane tetrapode exhibiting a NB phase

摘要

Biaxial (N_B) and uniaxial nematic (N_U) phase behavior was detected and confirmed for an organosiloxane tetrapode material using capacitance and birefringence measurements. Elastic constants, permittivities at two distinct low frequencies, and birefringencies were determined as a function of temperature over both the N_U and the N_B phase ranges. The N_U-N_B transition is clearly observed in the birefringencies and conoscopy data. A temperature dependent cross-over frequency is also detected in this material for the permittivities, allowing the electrical switching of both planar and homeotropic aligned samples.