Non-equilibrium phase transitions in a liquid crystal

摘要: The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features "Nematic-Isotropic" (N-I) phase a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from effects heating rate initial temperature on transitions, through differential scanning calorimetry (DSC), Fourier transform infrared fluorescence spectroscopy. Around vicinity (Tg), while only change in baseline ΔCp vs T curve is observed for (β) > 5 K min(-1), consistent with transition, clear peak β ≤ min(-1) rapid reduction value former to latter correspond an order-disorder ergodic non-ergodic behaviour. ln β 1000/T shows convex Arrhenius that can be explained very by purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. spectroscopy indicates sudden freezing out-of-plane distortion vibrations benzene rings around considerable red shift indicating enhanced coplanarity and, consequently, enhancement molecular ordering compared room temperature. We further provide direct experimental evidence nature N-I dependence this (TNI) associated enthalpy (ΔH) (at fixed β-values) DSC scans. A plausible qualitative explanation based Mesquita's extension Landau-deGennes theory [O. N. de Mesquita, Braz. J. 28, 257 (1998)] has been put forward. nematic isotropic investigated anisotropy measurements where order parameter, quantified anisotropy, goes zero phase. To point below temperature, parameter constant but decreases linearly increase during nematic-isotropic transition.