Dynamics of Nematic Liquid Crystal with Quenched Disorder in the Random Dilution and Random Field Regimes

Abstract

By means of specific heat spectroscopy, we have studied the dynamics of nematic 8CB nucleated, in the presence of random disorder, as the temperature is lowered across the isotropic to nematic phase transition such that the crossover region of random dilution to random field regimes of disorder strength is explored. We show, in terms of frequency dependence, hysteretic behavior, and aging effects, that the out-of-equilibrium properties of the nematic nucleated in the random disorder regime are strongly reminiscent of the bulk material while the one grown in the random field regime shows a glassy behavior with aging leading to slower dynamics. The aging effect has been explained in terms of strain relaxation in analogy with observations in other soft glassy colloidal systems.

Invited Review Article: Photopyroelectric calorimeter for the simultaneous thermal, optical, and structural characterization of samples over phase transitions

“…This causes its transition temperature to be lower with respect to the bulk like material and eventually leads to the fragmentation of the grown domains. 98 Figure 21 also shows that the latent heat exchanged over the LTP is considerably smaller than over the HTP. This once again FIG.…”

Computational studies of history dependence in nematic liquid crystals in random environments

“…Many experiments have been reported using the nCB series, with n ranging from 5 to 8. Among experimental techniques used have been various types of NMR studies [13][14][15], magnetically-induced birefringence [16], electro-optics [17], static and dynamic light scattering [18][19][20][21][22], various types of calorimetry [10,19,20,[23][24][25][26][27][28], dielectric spectroscopy [13,29] and cross-polarized microscopy [25]. Porous systems of a number of different related types have been employed, e.g.…”

“…Porous systems of a number of different related types have been employed, e.g. anopore-membrane gels [20,23], silica aerosil dispersions [15,25,26,[30][31][32], membrane filters [22], porous glass [13,16,27,28], solid polymer matrix [17], silicaparticle-based random gel [14,17,18], silica aerogel [19,21] and jammed aqueous laponite suspensions [33]. In general, transitions are rounded, order parameters reduced (with the degree of reduction depending on pore size), and long-range order in the nematic phase is lost.…”

Molecular dynamics of a short-range ordered smectic phase nanoconfined in porous silicon

“…4 Although it seems a quite general behavior, the connection between the glass-like 4 dynamics of confined LC's and the nature of the porous topology, surface interactions and confinement-induced quenched disorder effects remains challenging. 21,22,23,24 The individual molecular dynamics of confined LC's is also strongly modified. Dielectric relaxation spectroscopy has been extensively used since it allows one to probe the rotationallibrational dynamics of the dipolar molecules around their short axis as well as tumbling relaxation modes around the local nematic director.…”