Jian-Feng Li

Biaxiality in a Cyclic Thermotropic Nematic Liquid Crystal

Birefringence and textural data are presented for a ring-shaped trimeric liquid crystal. The material apparently undergoes a uniaxial-to-biaxial nematic phase transition as a function of temperature.

A No-Buff Technique to Produce Surfaces That Induce Alignment in Liquid Crystals

Alignment layers for liquid crystal cells were prepared by directional deposition of high molecular weight rigid-rod ionomers on glass and indium–tin–oxide substrates. Several deposition techniques were developed and tested. Material type, concentration, temperature, and application technique were systematically varied and the resultant alignment of the liquid crystals studied. Three different methods of applying the alignment layer were investigated: directional spray deposition, brushing, and directional deposition using a squeegee (doctor bar). The application temperature ranged from 30 to 80°C. The best results were obtained using a squeegee to perform directional deposition at temperature of less than 60°C. The alignment layers obtained in this way are robust, exhibit excellent alignment, and have pretilt angles of a few degrees.

Solitary Waves in an Antiferroelectric Liquid Crystal

Abstract The antiferroelectric liquid crystalline phase and related ferrielectric phases exhibit a rich variety of physical behavior. Recently we have been examining the dynamics of these materials. For materials whose dielectric anisotropy Δe < 0, we find a critical threshold d.c. field Eth in the Sm CA* phase, above which solitary waves propagate rapidly along the layer direction. These solitary waves, which consist of ferroelectric regions propogating into an antiferroelectric sea, may be “frozen” in place by reducing the field to Eth, or forced to retreat by reducing the field to E < Eth.