Prabir K. Mukherjee

Bio: Prabir K. Mukherjee is an academic researcher from Presidency University, Kolkata. The author has contributed to research in topics: Phase transition & Liquid crystal. The author has an hindex of 8, co-authored 28 publications receiving 230 citations.

The puzzle of the nematic-isotropic phase transition

Abstract: The low value of , where is the nematic-isotropic phase transition temperature and denotes the virtual transition temperature, is a long-standing puzzle in the physics of liquid crystals. The present review presents experimental and theoretical results on this long-standing problem. New experimental and theoretical results for the critical behaviour in the isotropic phase of nematogens are reviewed. We calculate in a unified approach the low value of , at both critical and tricritical points. The possibility of tricritical behaviour at the nematic-isotropic transition is also discussed by means of Landau theory. The various predictions are compared with the available experimental results.

On a new topology in the phase diagram of biaxial nematic liquid crystals

Abstract: We describe new topologies in the phase diagrams involving biaxial nematic liquid crystals. We find that a direct isotropic-biaxial nematic phase transition is possible. Our results show that three different biaxial nematic phases can occur. We outline how the novel phase diagrams could be detected experimentally.

Does the characteristic value of the discontinuity of the isotropic?mesophase transition in n-cyanobiphenyls exist?

Abstract: Results of the extended Landau?de Gennes model analysis and experimental studies of the isotropic?nematic (I?N) and isotropic?smectic-A (I?SmA) phase transitions in rod-like liquid crystalline n-alkylcyanobiphenyls are presented. Experiments were carried out as a function of temperature and pressure using the static dielectric permittivity and its ?nonlinear? (strong electric field related) counterpart?the low-frequency nonlinear dielectric effect. Precise estimations of the values of the discontinuity of the isotropic?mesophase transitions (?T) for nCB from n?=?3?14 have been obtained. It is suggested that for each nCB a unique, characteristic minimal value of ?T, associated with the I?N?SmA triple point, exists. For ?shorter? nCBs it can be hidden in the negative pressures domain. The possibility of the extension of the ?melting curve? into the negative pressures region as well as the appearance of the ?melting inversion? at high enough pressures is indicated.

Tricritical behavior of the smectic-A to smectic-C ∗ transition

Abstract: A phenomenological Landau-like theory is presented, which describes the tricritical behavior of the smectic-A to smectic-C∗ transition in a liquid crystal mixture. The influence of the concentration on this transition is discussed by varying the coupling between the concentration variable and the order parameters. It was observed from the theoretical calculations that for a particular value of the concentration, the first order smectic-A to smectic-C∗ transition becomes second order at a tricritical point. Calculations based on this model agree qualitatively with experiment.

Tricritical behavior of the R(I)-R(V) rotator phase transition in a mixture of alkanes with nanoparticles.

Abstract: A phenomenological theory is presented, which describes the tricritical behavior of the RI–RV rotator phase transition in the mixture of alkanes with nanoparticles The influence of the nanoparticles on the RI–RV transition in alkanes is discussed by varying the coupling between the order parameters of the rotator phases and nanoparticle When nanoparticle solutes are added to pure alkanes, the RI–RV transition temperature is increased It was observed from the theoretical calculations that for a particular value of the concentration of the nanoparticles, the first order RI–RV transition becomes second order at a tricritical point Calculations based on this model agree qualitatively with experiment

Liquid crystal elastomer actuators: Synthesis, alignment, and applications

Abstract: Liquid crystal elastomers (LCEs) are a unique class of materials which combine rubber elasticity with the orientational order of liquid crystals. This combination can lead to materials with unique properties such as thermal actuation, anisotropic swelling, and soft elasticity. As such, LCEs are a promising class of materials for applications requiring stimulus response. These unique features and the recent developments of the LCE chemistry and processing will be discussed in this review. First, we emphasize several different synthetic pathways in conjunction with the alignment techniques utilized to obtain monodomain LCEs. We then identify the synthesis and alignment techniques used to synthesis LCE-based composites. Finally, we discuss how these materials are used as actuators and sensors. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 395–411

Theory of Ferroelectric Nanoparticles in Nematic Liquid Crystals

Abstract: Recent experiments have reported that ferroelectric nanoparticles have drastic effects on nematic liquid crystals---increasing the isotropic-nematic transition temperature by about 5 K, and greatly increasing the sensitivity to applied electric fields. To understand these effects, we develop a theory for the statistical mechanics of ferroelectric nanoparticles in liquid crystals. This theory predicts the enhancements of liquid-crystal properties, in good agreement with experiments. These predictions apply even when electrostatic interactions are partially screened by moderate concentrations of ions.

Self-reporting and self-regulating liquid crystals

Abstract: Liquid crystals (LCs) are anisotropic fluids that combine the long-range order of crystals with the mobility of liquids1,2. This combination of properties has been widely used to create reconfigurable materials that optically report information about their environment, such as changes in electric fields (smart-phone displays) 3 , temperature (thermometers) 4 or mechanical shear 5 , and the arrival of chemical and biological stimuli (sensors)6,7. An unmet need exists, however, for responsive materials that not only report their environment but also transform it through self-regulated chemical interactions. Here we show that a range of stimuli can trigger pulsatile (transient) or continuous release of microcargo (aqueous microdroplets or solid microparticles and their chemical contents) that is trapped initially within LCs. The resulting LC materials self-report and self-regulate their chemical response to targeted physical, chemical and biological events in ways that can be preprogrammed through an interplay of elastic, electrical double-layer, buoyant and shear forces in diverse geometries (such as wells, films and emulsion droplets). These LC materials can carry out complex functions that go beyond the capabilities of conventional materials used for controlled microcargo release, such as optically reporting a stimulus (for example, mechanical shear stresses generated by motile bacteria) and then responding in a self-regulated manner via a feedback loop (for example, to release the minimum amount of biocidal agent required to cause bacterial cell death). Liquid crystals are used to self-report and self-regulate either continuous or transient release of droplets or microparticles trapped within them in response to thermal, chemical, mechanical or biological stimuli.

Critical behavior at the isotropic-to-nematic phase transition in a bent-core liquid crystal.

Abstract: Magnetic birefringence and dynamic light scattering measurements of orientational order parameter fluctuations at the isotropic-nematic phase transition of a bent-core liquid crystal reveal a pretransitional temperature dependence consistent with the standard Landau-deGennes mean field theory. However, as follows: the transition in the bent-core compound is more weakly first order (TNI-T* approximately 0.4 degrees C), the leading Landau coefficient is approximately 30 times lower, the viscosity associated with nematic order fluctuations is approximately 10 times higher, and the density change is approximately 10 times lower, than typically observed in calamitic (rod-shaped) liquid crystals. One consistent explanation for these anomalies is an optically isotropic phase composed of microscopic complexes or "clusters" of bent-core molecules.