title: Stepwise heat-capacity change at an orientation transition in liquid crystals.
abstract: During a phase transition in a bulk material, heat is exchanged with matter to balance the changes in the internal energy and the entropy of the system. Here we report on the thermal detection of a surface-mediated anchoring transition, a spontaneous and discontinuous orientation change between planar (P) and homeotropic (H) alignments within a single nematic phase by changing temperature. In this case a stepwise change in the heat flow, similar to a glass transition, is observed by means of high-resolution differential scanning calorimetry. We found that the jump in the specific heat does not depend on the sample volume, although the contribution of molecules in the vicinity of surfaces, which trigger the transition, becomes less with increasing the sample volume. This means that different molecular orientations, H and P, with respect to surfaces have different thermodynamic free energies. We also address why the anchoring transition occurs by means of grazing-incidence x-ray diffraction measurements, which clearly reveal the formation of quasismectic layers parallel to surfaces in the nematic phase.
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Aya
authors.affiliation: Division of Applied Physics, Graduate School of Engineering, Hokkaido University, North 13 West 8, Kita-ku, Sapporo 060-8628, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sasaki
authors.affiliation: University of Warsaw, Department of Chemistry, ul. Żwirkii Wigury 101, 02-089 Warsaw, Poland.
authors.forename: Damian
authors.initials: D
authors.lastname: Pociecha
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Fumito
authors.initials: F
authors.lastname: Araoka
authors.affiliation: University of Warsaw, Department of Chemistry, ul. Żwirkii Wigury 101, 02-089 Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Górecka
authors.affiliation: Department of Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8551, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ema
authors.affiliation: Department of Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8551, Japan.
authors.forename: Igor
authors.initials: I
authors.lastname: Muševič
authors.affiliation: Division of Applied Physics, Graduate School of Engineering, Hokkaido University, North 13 West 8, Kita-ku, Sapporo 060-8628, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Orihara
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Ishikawa
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Takezoe