Research

We use complementary experimental and simulation approach to study rheology of nonequilibrium disentangled melts of longer polymer chains. The idea is that such systems should display a different rheological behavior, glass transition temperature etc. in comparison to their equilibrated counterparts. The experimental part of the work involves fabrication of single-chain nanoparticles using electrospinning technique, characterizing (using SEM, TEM, AFM and NMR) and investigating the rheological properties, relaxation behavior and glass-transition temperature of disentangled polymer melts consisting of these single-chain nanoparticles. The theoretical part of my research involves performing bead-spring (Kremer-Grest) model based molecular dynamics simulations to prepare fully disentangled melt of globules of single independent chains. Thereafter the disentangled melt is allowed to relax and studied with respect to change in structure of polymer chains (radius of gyration, end-to-end distance and entanglement length), rheological behavior and glass-transition temperature. The development of entanglements during relaxation is studied using primitive path analysis (PPA).

Nature has its own complex way of lubricating sliding surfaces with the help of glycoproteins. In recent times mankind has tried to imitate natural lubrication using polymer brushes. Polymer molecules are attached by one end to a surface using different approaches (‘grafting to’ or ‘grafting from’); if the surface grafting density is so high that the polymer chains start to overlap, they stretch away from the surface forming a polymer brush. The equilibrium brush height is larger than the size of the unperturbed chains in bulk solution. Polymer-brush-coated surfaces find applications in many fields including colloidal stabilization, adhesion, bio-compatibilization and tribology. The aim of our study is to understand the underlying molecular mechanisms of frictional behavior of polymer brushes and gels in a good solvent by employing complementary experimental and simulation studies.

Rolling is one of the oldest and most important metalworking processes. The mechanical objective of rolling is to reduce the thickness of strip from an initial value to a pre-determined final value. It is done with the help of a rolling mill where two rolls rotating in opposite directions draw the work piece into the roll gap and force it to exit, causing reduction in the thickness of work piece.

Friction is one of the most important parameters for the rolling process. In this context it is appropriate to quote Roberts (1997) "Of all the variables associated with rolling, none is more important than friction in the roll bite. Friction in rolling, as in many other mechanical processes can be a best friend or a mortal enemy, and its control within an optimum range for each process is essential. "