Electric-field-induced B1-B2 transition in bent-core mesogens

Area of Science:

• Liquid crystal physics
• Materials science
• Organic chemistry

Background:

• Bent-shaped mesogens are known for complex phase behaviors.
• The B1 phase typically exhibits antiferroelectric properties.
• Electro-optic effects in the B1 phase are uncommon.

Purpose of the Study:

• To investigate the electro-optic properties of novel bent-shaped mesogens in the B1 phase.
• To characterize the phase transitions induced by electric fields.
• To determine the ferroelectric or antiferroelectric nature of the observed phenomena.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis.
• X-ray diffraction for structural characterization.
• Electro-optic measurements to assess optical response to electric fields.
• Polarization reversal and dielectric spectroscopy to probe ferroelectric/antiferroelectric behavior.

Main Results:

• Two bent-shaped mesogens displayed an electro-optic effect in the B1 phase, characterized by increased birefringence under an AC electric field.
• No switching current was detected, confirming antiferroelectric behavior in the B1 phase.
• A reversible field-induced phase transition to a homochiral B2 phase was observed, exhibiting typical antiferroelectric switching.

Conclusions:

• Novel bent-shaped mesogens demonstrate an unexpected electro-optic response in the B1 phase.
• The B1 phase in these compounds retains antiferroelectric properties despite the observed electro-optic effect.
• Electric field application can induce a reversible transition to a homochiral B2 phase, offering potential for new electro-optic applications.