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Research Areas
 
Liquid Crystals, Nano-composites &   Polyelectrolytes
Phase behaviour of ionic surfactants
Structure of DNA-surfactant complexes
Organization of sterols in membranes
Colloids and complex fluids
Biophysics
 
Theoretical studies
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Liquid Crystals, Nano-composites and Polyelectrolytes
 
Experimental and theoretical studies have been undertaken at RRI to deal with the structure property relations of ‘soft’ materials, which are easily deformable by external stresses, electric, and magnetic fields. Among these soft materials, thermotropic liquid crystals consisting of highly anistropic organic molecules, nano-composite materials, polymers and biomaterials such as biomolecules and cells are studied using a variety of experimental techniques. The interplay between the different degrees of freedom and various constraints present in these systems often give rise to rich and complex behaviour that can be exploited for potential technological applications.

The chemistry wing of the Soft Condensed Matter Group is involved in the design, synthesis and characterisation of novel liquid crystalline materials that exhibit remarkable electronic and optoelectronic properties. A number of monomeric, oligomeric, polymeric, and ionic liquid crystalline materials have been synthesized. The synthesis of liquid crystalline materials using microwave heating has also been carried out with a view to find quick and environment-friendly synthetic routes.

The incorporation of nanomaterials like metal-nanoparticles, quantum dots, carbon nanotubes and graphene in the supramolecular order of liquid crystals is likely to lead to novel materials for many applications. With this view, a research program has been initiated to prepare and functionalise these nanomaterials with discotic as well as other molecules and disperse them in monomeric, oligomeric and polymeric discotic liquid crystals. The dispersion of such functionalised nanomaterials in columnar matrix has been found to enhance physical properties such as conductivity and photoconductivity significantly.

One of the present research interests of the SCM group is in investigating electric field induced chiral symmetry breaking in liquid crystals made of achiral molecules. The structure and properties of novel field induced dark mesophases composed of electro optically switchable macroscopic chiral domains are being studied, using a variety of techniques like optical microscopy, dielectric spectroscopy and x-ray diffraction. Field dependent shape transitions, exhibited by the nucleating chiral domains, which form these mesophases, are also being studied in order to understand the observed enantioselectivity. The role of growth morphology in coarsening is under study to get a physical insight into the effects of chiral and electrostatic interactions. Studies of chiral thin films possessing tunable enantioselectivity are also interesting from a technological point of view, as they have potential for chiroptical and NLO applications.

Another area of interest is in understanding structure and dynamics of polyelectrolytes using dielectric spectroscopy. Very low frequency relaxation modes arising from polarization mechanisms involving counter ions and polar side chains are usually quite challenging to probe experimentally, and have therefore not been explored extensively. Detailed dielectric studies have been undertaken on some aqueous polyelectrolytes, some of which also exhibit coacervation.

 
Phase behaviour of ionic surfactants
 
The effect of adsorbing counterions and polyelectrolytes on the phase behavior of ionic surfactants is being investigated using a variety of experimental techniques. The main objective of these studies is to find conditions under which novel aggregate morphologies and phases can be stabilized in these systems. Theoretical modelling of these systems is also planned.
 
Structure of DNA-surfactant complexes
 
Structure of DNA-cationic surfactant complexes is being investigated using x-ray diffraction. The main focus of the study is to stabilize different structures of these complexes by changing parameters, such as the size of the surfactant molecule and the nature of its counterion.
 
Organization of sterols in membranes
 
The phase behaviour of lipid membranes containing different sterol molecules is being studied, with a view to understanding the organization of these biologically important molecules in the membrane. Further experiments are underway to probe the orientation of these molecules in the membrane.
 
Colloids and complex fluids
 
Experimental investigations of the structure, dynamics and rheology of non-Newtonian fluids and aging suspensions, soft glassy rheology, flow-structure correlations in complex fluids, rheological chaos and the nonlinear dynamics of shear flows, interfacial instabilities, the design of viscometers to measure complex flows, the stability of colloidal suspensions, the sedimentation of colloidal gels, micellar packings, controlled, targeted drug delivery using copolymer micelles as vehicles for drug delivery, the physics of granular media are being carried out.

Experimental tools such as static and dynamic light scattering, rheology, ultrasound attenuation spectroscopy and high-speed imaging are being used extensively for these studies. Many of these investigations involve collaborations with engineers and theoretical physicists working in the areas of statistical mechanics and materials science.
 
Biophysics
 
The Biophysics group at RRI encompasses experimental, theoretical and computational study of various biological systems.

A physicist’s approach to biological systems provides a novel perspective on how living machinery inside a cellular factory works. The group at RRI aims at achieving a quantitative physical description of dynamical phenomena occurring in cells at various levels. They are interested in nanoscale molecular structures that dominate interactions in DNA, protein segregation and signaling at the cell membrane, aided by active cellular dynamics. They also investigate dynamical phenomena in neuronal cells leading to shape transitions and active mechanical responses. To quantify these studies, novel state-of-the-art techniques are developed in-house: for example, single molecule resolution nano-devices which help in deciphering secrets of biological nano-world and ultra-sensitive force measurement methods to probe mechanical responses of single cells. Theoretical and computational approach is aimed at not only deciphering quantitative experiments but also to predict novel mechanisms. This is a rapidly expanding area of research at RRI and overlaps with other traditional topics like statistical mechanics, membrane- and polymer physics.
 
Theoretical studies
 
Theoretical investigations in the SCM group primarily focus on the theory of elasticity and topological defects in soft matter. Orientational (such as nematic, vector, hexatic) tangent-plane order on two-dimensional membranes deformable in three dimensions suffers frustration on curved membranes. This is also the case for certain smectic liquid crystals, and thin crystalline lamellae. For example, solution- and melt grown polymer crystallites grow in the form of lamellae exhibiting diverse morphologies such as helicoidal-, tent- and scroll structures. Attempts are being made to formulate a phenomenological theory based upon the interplay between elasticity and topological defects to explain the stability of observed morphologies.
 
 
 
 
 
 
 
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