Rich polymorphism of a rod-like liquid crystal (8CB) confined in two types of unidirectional nanopores

• Published in: The European physical journal. E, Soft matter and biological physics Vol. 26; no. 3; pp. 261 - 273
• Main Authors: Guégan, R., Morineau, D., Lefort, R., Béziel, W., Guendouz, M., Noirez, L., Henschel, A., Huber, P.
• Format: Journal Article
• Language: English
• Published: Bologna Società Italiana di Fisica 01.07.2008; Springer; EDP Sciences: EPJ
• Subjects: Aluminum Oxide - chemistry; Biological and Medical Physics; Biophysics; Calorimetry, Differential Scanning; Chemistry; Colloidal state and disperse state; Complex Fluids and Microfluidics; Complex Systems; Condensed Matter; Earth Sciences; Environmental Sciences; Exact sciences and technology; General and physical chemistry; Geophysics; Global Changes; Lipid Bilayers - chemistry; Liquid Crystals - chemistry; Membranes; Nanostructures - chemistry; Nanotechnology; Neutron Diffraction; Phase Transition; Physics; Physics and Astronomy; Polymer Sciences; Porosity; Porous materials; Regular Article; Scattering, Small Angle; Sciences of the Universe; Silicon - chemistry; Soft and Granular Matter; Soft Condensed Matter; Surface Properties; Surfaces and Interfaces; Temperature; Thin Films; 61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems; 64.70.mj Experimental studies of liquid crystal transitions; 61.05.fg Neutron scattering (including small-angle scattering); Confinement; Rod; Smectic state; Porous material; Liquid crystals; X ray diffraction; Inorganic membrane; Nanoporosity; Polymorphism; silicon; confinement; neutron; 8CB; porous; liquid-crystal; quenched disorder
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2007-10323-0

. We present a neutron and X-rays scattering study of the phase transitions of 4-n-octyl-4' -cyanobiphenyl (8CB) confined in unidirectional nanopores of porous alumina and porous silicon (PSi) membranes with an average diameter of 30nm. Spatial confinement reveals a rich polymorphism, with at least four different low temperature phases in addition to the smectic A phase. The structural study as a function of thermal treatments and conditions of spatial confinement allows us to get insights into the formation of these phases and their relative stability. It gives the first description of the complete phase behavior of 8CB confined in PSi and provides a direct comparison with results obtained in bulk conditions and in similar geometric conditions of confinement but with reduced quenched disorder effects using alumina anopore membranes.