par Gbabode, Gabin 
;Chattopadhyay, Basab
Référence Non-equilibrium Phenomena in Confined Soft Matter: Irreversible Adsorption, Physical Aging and Glass Transition at the Nanoscale, Springer International Publishing, page (207-225)
Publication Publié, 2015-08
;Chattopadhyay, Basab Référence Non-equilibrium Phenomena in Confined Soft Matter: Irreversible Adsorption, Physical Aging and Glass Transition at the Nanoscale, Springer International Publishing, page (207-225)
Publication Publié, 2015-08
Partie d'ouvrage collectif
| Résumé : | In this chapter, we investigate the unusual phase behavior of a thermotropic discotic liquid crystal (DLC), processed as thin and ultrathin films. The physical confinement imposed by the reduced size is responsible for the stabilization, at reduced film thickness i.e. less than 30 nm, of a new structural arrangement different from the bulk stable columnar rectangular phase. The presence of this new singular non-equilibrium form is unambiguously revealed by microscopy and X-ray diffraction techniques. Grazing incidence X-ray diffraction clearly put forward a net increase in packing order between the non-equilibrium phase and the thermodynamically stable structure. In particular, the latter presents a conventional two-dimensional molecular packing typical for columnar phases of DLCs, while the former is characterized by full three-dimensional packing. Surprisingly, extensive optical and scanning probe microscopy observations carried out as a function of time demonstrate that this new crystal form is favored by interfaces and is effectively able to nucleate at the substrate/film as well as at the film/air interface, independently of film thickness. |
