Research
Research in our group encompasses broadly in the areas of theoretical chemistry involving statistical mechanics of soft condensed mater systems. Specifically we are interested currently in the following:
Polymer Melt Dynamics: Conventional approaches to anomalous dynamics in unentangled chain melts are based on the variants of mode coupling theory or generalized Langevin equation. Either are first principles theories based on separation of time scales in phase space variables. The resulting framework due to complexities is not exactly solvable, and the subsequent well-investigated approximations explain not all physical regimes of interest. The understanding remains incomplete with scope for alternate approaches.
We provide an alternate approach to look into the unentangled polymer melt dynamics.1 We generalize the idea of diffusing diffusivity—particle diffusivity modeled as a stochastic process in time—to many particle system with localized interactions, a chain of connected beads, namely Rouse model.2 Our treatment derives exact modified Rouse dynamics. We apply our theory to simulation trajectories of unentangled polymer melts and show explicitly its success in explaining anomalous and non-Gaussian center of mass and monomer diffusion, concurrent with the existing understanding in the subject.1
1 P. Shukla, N. Ahamad, and P. Debnath, Diffusing diffusivity in dynamics of unentangled polymer melts, Macromolecular Theory and Simulations, 2100056, 2021.
2 N. Ahamad and P. Debnath, Rouse model in crowded environment modeled by “diffusing diffusivity”, Physica A, 124335, 549, 2020.
Dynamics of Model Polymer Systems: Rupture models has been studied extensively to understand the microscopic origin of various physical phenomena involving the relative motion of surfaces. We focus on one such tractable, generic, one-dimensional model, involving a flexible polymer connected to a rigid substrate by interconnecting bonds which rupture stochastically under external stress; in an attempt to capture the microscopic mechanism at the single polymer level. The problem was simulated, and by using a mean field approximation and travelling wave formalism, we could derive a closed form expression for rupture fronts that detach the flexible polymer from rigid substrate, thus providing useful insights into the stability of modeled system.
Ref: Soft Matter, 2016, 12, 4406 – 4417.