Microphase-Stabilized Ferroelectric Liquid Crystals (MSFLC): Bistable Switching of Ferroelectric Liquid Crystal−Coil Diblock Copolymers

A side-chain liquid crystal (LC) block copolymer with a ferroelectric smectic C* LC block has been shown to exhibit bistable switching behavior in electric fields. Ferroelectric switching was demonstrated for block copolymers with volume fractions of 0.58 and 0.52 liquid crystal block. SAXS and TEM showed that the bulk morphologies of these two materials were hexagonally packed minority amorphous polystyrene (PS) cylinders and alternating lamellar amorphous PS layers, respectively. Cross-sectional TEM of a 10 μm thick film of the 0.58 volume fraction liquid crystal material used for the optical switching studies showed the cylinders to be well aligned along the shear direction and orthogonal to the applied electric field direction. It is believed that switching is possible due to an unwinding of the pitch of the smectic C* phase due to the presence of the intermaterial dividing surface of the microphase-separated cylindrical domains of the block copolymer which spatially confine the mesophase. This interaction realizes the concept of a microphase-stabilized ferroelectric liquid crystal (MSFLC) device.