Electric-field-induced isotropic-nematic phase transition

Biaxiality-induced magnetic field effects in bent-core nematics: Molecular-field and Landau theory

“…Later Rosenblatt [3] was able to observe an increase in the transition temperature, but the shift was negligible, of only a few mK. More recently, all three fieldinduced phenomena have been observed experimentally for a system of calamitic molecules in electric fields by Lelidis and Durand [4]. However, in general these effects are also weak and difficult to observe.…”

“…Thus the unusual experimental observation was simply that for this system it was possible to observe a noticeable magnetic-field dependence of the nematic-isotropic phase transition. Electric field effects are in principle analogous from a theretical point of view, and should be easier to observe, because the electric coupling to experimentally accessible electric field is higher than that to experimentally accessible magnetic fields [4,36,45]. But electric fields present other kinds of problems, most noticeably Ohmic heating and screening, and so in some sense a magnetic field experiment presents a more unambiguous test of theory.…”

“…In general such theories exchange simplicity for a degree of accuracy, but do have the advantage of using as input parameters which are obtained from experiment. In uniaxial nematogens Landau-de Gennes theories have already been used some time ago to describe the effects of magnetic [1,7,9] and electric [4,36] fields. There has also been considerable work on Landau-de Gennes theories in biaxial nematogens in zero field [1,[37][38][39][40][41][42][43].…”

“…makes little difference to the mathematical structure of the theory. Landau-de Gennes theories for electric [4] and magnetic [1,7] fields both give analytical formulas for the three field-induced phenomena discussed above. Analogous calculations for nematics formed from calamitic molecules, using Maier-Saupe-like molecular field theories in the presence of an external field, have been made by Hanus [8] (electric fields) and Wojtowicz and Sheng [9] (magnetic fields).…”

Light scattering from liquid crystal director fluctuations in steady magnetic fields up to 25 tesla

“…The capabilities of the Split Florida-helix should considerably expand the general scope of high-field studies of LCs, including quenching of director fluctuations and enhanced optical birefringence in nematics [5]; magnetic field-induced phase transitions and related symmetry changes [6,7]; field effects on the phase diagram [8][9][10][11][12]; and the impact of field on pretansitional and critical phenomena [13][14][15][16][17][18], particularly in situations where large electric fields are impractical or deleterious to the sample. We hope that the results we present here, together with the extended data acquisition capabilities planned for the future, will inspire new users of NHMFL within the broader soft matter community.…”