Gaurav Goel

Chemical Engineering, Indian Institute of Technology-Delhi

E-mail id: goelg[at]chemical.iitd.ac.in

 

 

Brief Bio-sketch:

Dr. Gaurav Goel is currently an assistant professor in the Department of Chemical Engineering, IIT Delhi. He earned his Ph.D. from the University of Texas at Austin in 2009 and worked as a postdoctoral fellow at the Case Western Reserve University before joining IIT-Delhi in 2011. His research group is working on advancing understanding of self-assembly processes in soft-condensed matter systems using statistical thermodynamics theory and molecular simulations. The group is particularly interested in developing new formulations with specific target properties for protein therapeutics, polymer nanocomposites, and supercapacitor materials.

 

A COARSE-GRAINED FORCE FIELD FOR INVESTIGATING LONG TIMESCALE DYNAMICS OF POLYMER-CLAY NANOCOMPOSITES

Polymer nanocomposites consisting of highly anisotropic layered-silicate (clay) nanoparticles are an important class of materials with tunable properties. These anisotropic nanoparticles provide a large polymer-particle interfacial area, and therefore, show significant impact on mechanical, structural, and barrier properties of polymer-clay nanocomposites (PCNC) even at low loadings. A large number of material and process parameters, and non-monotonic dependence of target properties on these parameters makes the development of PCNCs for specific applications a challenging task. Molecular simulations provide a means to quickly sample a large parameter space to probe dependence of nanoscale structure of the composite material on parameters such as polymer clay interfacial interactions and clay polarity. However, two key issues that limit the application of atomistic simulation to this system are long relaxation times associated with polymer dynamics and the requirement of large system size for anisotropic particles. To this end, we have developed an accurate, self-consistent coarse-grained (CG) model of a polymer-clay system consisting of organically modified montmorillonite nanoclay as the nanoparticle. The CG model is developed in accordance with the MARTINI forcefield for polymers and lipids that has been shown to accurately capture the polar-apolar character of individual subunits. We have used the energy equivalence method to correctly reproduce individual contribution of bonded, polar, and dispersive interactions to clay surface energy. A self-consistent parameter set for clay-polymer interactions is then obtained to accurately reproduce structural, thermodynamic, and dynamic properties of a polymer-clay system. The transferability of developed parameter set was verified by comparing against all-atomic (AA) simulations for PCNCs consisting of three different matrix polymers at two different temperatures. The CG-Martini simulations were found to be 90x faster than the AA simulations. We also report some interesting insights into the role of clay-polymer interactions on structure-property relationships in PCNCs. Finally, we use long timescale CG-Martini simulations to determine impact of PE-g-PEO compatibilizer on dissociation free energy of clay platelets, and the effect of compatibilizer and clay exfoliation on matrix poylmer's structural and thermodynamic properties.