Study of the dielectric properties of ferroelectric liquid crystals and related side chain liquid crystalline polymers

摘要

Broadband dielectric spectroscopy (frequency range 10~(-1) —10~6 Hz) was used to analyze the frequency and temperature dependence of the molecular dynamics of a series of ferroelectric liquid crystals (FLCs) and polymers which exhibit a chiral smectic C (S_C~*) phase in a wide temperature range (about 190℃) including room temperature. Two ferroelectric modes, Goldstone and Soft mode, were observed in the low-molar-mass FLCs. Both of these modes were found in the S_C~*phase; however, only the soft mode was present in the smectic A (S_A) phase. On the other hand, two collective relaxation processes (Soft and Goldstone mode) and four molecular relaxations (δ, α, β and γ-relaxation) of the side chain liquid crystalline polymer were demonstrated.