CHE Seminars  

Speaker Mr. Rahul Mangal
Graduate Research Assistant, Cornell University, USA
Topic Structure and Dynamics of Nanoparticle Polymer Composites
Date 18,January 2016 (Monday)
Place L-2 Lecture Hall Complex (LHC)
4 pm. - 5 pm.

Nanoparticle-polymer composites, or polymer nanocomposites (PNCs), exhibit unusual mechanical and dynamical features when the particle size (D) approaches the random coil dimensions of the host polymer. This talk will discuss a strategy for creating model PNCs in which spherical nanoparticles (NPs) are uniformly dispersed in high molecular weight (Mw) entangled polymers. In particular, by carefully harnessing favorable enthalpic interactions between particle-tethered and host polymers we show that particle-particle aggregation can be completely avoided.
Investigation of the mechanical properties of these model PNCs reveal that nanoparticles have profound effects on their host polymer’s physical properties and dynamics on essentially all timescales. The talk will specifically consider the effect of surface and geometric confinement and constraint release processes induced by particle motion induce on dynamics of entangled melts. We show, for example, that progressive addition of NPsto polymers induce additional constraints for the polymer chain motion than typically observed in entangled melts, leading to an earlier discovery of the confinement tube. On long timescales, NPs appear to promote an early onset of terminal relaxation of the polymer chains for high Mw hosts. At high particle content, particle constraints can induce glassy behavior in the host polymer. Investigation of nanoparticle dynamics reveal that as the nanoparticle size D, is progressively increased above the tube diameter of the host polymer (a), particles undergo a transition from normal diffusion to hyperdiffusive relaxation dynamics. A local viscosity model capable of explaining these observations is discussed and the results compared with findings from a recently proposed scaling/theoretical model for hopping of NPs in polymers.

Rahul Mangal is currently a PhD candidate with Prof. Lynden Archer at Cornell University. His research focuses on understanding different Structural and Dynamic properties of Polymer Nanocomposites. He graduated from IIT Kanpur in 2010 with a B.Tech-M.Tech Dual degree in Chemical Engineering. During his masters he worked with Prof. Ashutosh Sharma on biomimetic viscoelastic polymer adhesive films. After graduating from IITK he worked in Reliance Industries Limited, Jamnagar as a manager for couple of years after which he joined Cornell University in 2012.

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