Phase transition from focal conic to cubic smectic blue phase in
partially fluorinated cyano-phenyl alkyl benzoate ester doped with ultrahigh
twisting power chiral dopant
Article
Nayek, Prasenjit, Gauza, Sebastian, Li, Guoqiang. (2015). Phase transition from focal conic to cubic smectic blue phase in
partially fluorinated cyano-phenyl alkyl benzoate ester doped with ultrahigh
twisting power chiral dopant
.
Blue phase liquid crystal (BPLC) has important applications in adaptive
lenses and phase modulators due to its polarization-independent property.
During our efforts for development of the new materials, we found a novel
phenomenology of phase transition, from focal conic smectic to smectic blue
phase in a partially fluorinated cyanophenyl alkyl benzoate ester based nematic
liquid crystal (LCM-5773) doped by ultra-high twisting power [H.T.P~160 um^-1]
chiral dopant (R5011/3 wt%). Polarized optical microscopy (POM) investigations
revealed focal conic and fan-shaped textures typical for columnar mesophases.
These focal conic domains (FCDs) are squeezed under electric field and finally
at a critical electric field they undergo a dark state. When the electric field
is withdrawn, the FCDs are regrown in a one dimensional array with smaller
domain size. Interestingly, we have observed the domain size of the FCDs can
grow several times by decreasing the cooling rate (0.02 degrees(C)/min.) ten
times without any change in the phase sequence. In blue phase (BP), we have
observed curved platelet texture and grain boundaries filled by small
platelets, which is completely different from conventional cholesteric BP. The
blue phase platelet size (PLS) also increases significantly at low cooling
rates. The thermal control of FCD and PLS size has increasing demand for the
construction of devices with optimal performances.
