Antiferroelectric Liquid Crystal from Bent-Core Molecule with Vinyl End Group

Abstract

Three banana-shaped achiral compounds, 4-chloro-1,3-phenylene bis [4-{4-(undecenyloxy)phenyl iminomethyl}benzoate] derivatives, were synthesized with variation of a substituent (x=H, F, Cl); their antiferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C(Sm C * ) phase, were characterized by differential scanning calorimetry, polarizing optical microscopy, triangular wave method, and X-ray diffractometry. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules induced a decrease in melting temperature and formation of the switchable Sm C * phase in the melt. The smectic phase having a lateral fluorine-substituent at 3-position of the Schiff's base moiety showed antiferroelctric switching, and the value of spontaneous polarization on reversal of an applied electric field was 250 nC/cm 2 .

Side-Chain Liquid Crystalline Poly(meth)acrylates with Bent-Core Mesogens

“…Although BCLCs have been extensively investigated, research on BCLC polymers is still limited. A few polymerizable BCLC systems have been reported. − In most of these cases, polymerizable groups, such as 1,3-diene, di(meth)acrylates, or vinyl group, ,,− were symmetrically attached in both ends, some of which could be thermally or optically cross-linked to form BCLC networks. ,, Polarized polymeric materials with pyroelectric properties could be achieved when those monomers were polymerized in the B2 phase under the external electric field . Nematic phase was found when ester-type banana mesogens were introduced in polymer main chain together with rodlike mesogens synthesized via alternating diene metathesis polycondensation. , Furthermore, B1 and B2 phases could be formed in main-chain polymers with azomethine-type mesogens, but the high viscosity and high phase transition temperature restricted further investigation .…”