Electric-field-induced phase diagrams of blue-phase systems

The effect of electric field on the phase behavior in several blue-phase systems has been studied in detail using optical reflection. The phase diagram of a CB15-E9 mixture (where CB15 represents 4-cyano-4’-(2’’-methylbutyl)-biphenyl and E9 represents a British Drug House eutectic biphenyl mixture shows an extensive temperature range in which the field-induced tetragonal and tetragonal and hexagonal phases exist. Phase diagrams of CB15-M18 and CB15-M24 mixtures (M18 represents 4-cyano-4’-hexyloxy-biphenyl and M24 represents 4-cyano-4’-octyloxy-biphenyl) do not show evidence for the tetragonal phase, but exhibit unusual topologies of phase boundaries near the cholesteric–blue-phase I–blue-phase II triple point. At sufficiently high field, the cholesteric phase transforms upon heating to a phase other than blue phase I in all the mixtures.