Calus, SylwiaSylwiaCalusJabłońska, BeataBeataJabłońskaBusch, MarkMarkBuschRau, DanielDanielRauHuber, PatrickPatrickHuberKityk, Andriy V.Andriy V.Kityk2021-04-162021-04-162014-06-09Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 89 (6): 062501 (2014-06-09)http://hdl.handle.net/11420/9320We explore the optical birefringence of the nematic binary mixtures 6CB1-x7CBx (0≤x≤1) embedded into parallel-aligned nanochannels of mesoporous alumina and silica membranes for channel radii of 3.4≤R≤21.0 nm. The results are compared with the bulk behavior and analyzed with a Landau-de Gennes model. Depending on the channel radius the nematic ordering in the cylindrical nanochannels evolves either discontinuously (subcritical regime, nematic ordering field σ<1/2) or continuously (overcritical regime, σ>1/2), but in both cases with a characteristic paranematic precursor behavior. The strength of the ordering field, imposed by the channel walls, and the magnitude of quenched disorder varies linearly with the mole fraction x and scales inversely proportionally with R for channel radii larger than 4 nm. The critical pore radius, Rc, separating a continuous from a discontinuous paranematic-to-nematic evolution varies linearly with x and differs negligibly between the silica and alumina membranes. We find no hints of preferred adsorption of one species at the channels walls. By contrast, a linear variation of the nematic-to-paranematic transition point TPN and of the nematic ordering field σ versus x suggests that the binary mixtures of cyanobiphenyls 6CB and 7CB keep their homogeneous bulk stoichiometry also in nanoconfinement, at least for channel diameters larger than ∼7 nm. © 2014 American Physical Society.en1550-237620146American Physical SocietyNatural Sciences and Mathematics::530: PhysicsJournal Article10.1103/PhysRevE.89.06250125019799Journal Article