Abstract
An open system is a system driven away from equilibrium by a source that supplies an inflow of energy and a sink to maintain an outflow. A typical example of an open system is a system close to its phase transition temperature under irradiation by a laser. This provides a steady flow of energy through a photon flux. The sink in that case is the environment to which energy is lost in the form of heat dissipation. Creation of such a thermodynamically open state suggests that we can expect generation of exotic spatio-temporal structures length-scale independent correlation maintained under the global dissipative forces provided by the surroundings. Internal long-range forces can bring in additional spatio-temporal correlations, giving rise to states with a very long lifetime, the ‘quasistationary states’ (QSS). In this communication, we report evolution of quasistationary states, in a mixture of the well-known liquid crystal (N-(4-methoxybenzylidene)-4-butylaniline, MBBA) and an iron-based room temperature ionic liquid (RTIL), namely, 1-ethyl-3-methylimidazolium tetrachloroferrate (EMIF) at the Nematic-Isotropic phase transition, when focused radiation with 532 nm wavelength from a Nd:YAG laser (200-300 mW optical power) is incident on the sample. We explain the QSS by invoking a sharp negative thermal gradient due to the laser photon flux and dipolar interactions. In our model, the dipoles are the charge transfer complexes (CTCs) formed in the RTIL by resonant laser pumping, which create an orientational ordering and balance the fluctuating force of the thermal gradient to create the QSS. In the absence of such CTCs in a mixture of MBBA and a Gallium-based RTIL (1-ethyl-3-methylimidazolium tetrachlorogallate, EMIG), the QSS was not observed.
Highlights
When in a phase transition the system transforms from one equilibrium structure to another with a change in symmetry, there is exchange of a fixed amount of energy with the surrounding at a fixed temperature
From the equilibrium and non-equilibrium properties of the mixtures described in sections Equilibrium Properties of the Mixtures and The Open Systems and Their Dynamics, respectively, we find that (1) EMIG has a stronger effect on the NI transition than ethyl-3-methylimidazolium tetrachloroferrate (EMIF) under equilibrium conditions while (2) it has essentially no effect on the transition under non-equilibrium conditions
We have shown that a quasistationary state is generated at the nematic-isotropic interfacial region of a mixture of a liquid crystalline material and an iron-based room temperature ionic liquid on focused irradiation by a laser
Summary
When in a phase transition the system transforms from one equilibrium structure to another with a change in symmetry, there is exchange of a fixed amount of energy with the surrounding at a fixed temperature. In the stage of EMIF-MBBA N-I transition dynamics (region 3, Figure 2A), roughly triangular areas with their bases on the nematic-isotropic boundary open up in the nematic bulk These patches consist of randomly oriented, nanometer-sized domains similar to those in the interfacial zone. We see a monotonically increasing isotropic domain, where the growth rate of that domain increases with laser power This qualitative and tentative model of the RTIL system, besides explaining the quasi-stationary states formed in this particular situation provides the framework for deciding the requirements to generate QSS in this class of materials that are emerging as highly promising for a wide range of application
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
