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Dr. Ramanan Krishnamoorti Seminar
September 28 @ 11:00 am - 12:00 pm
Understanding the Structure and Dynamics of Polymer Grafted Nanoparticles
The behavior of nanoparticles dispersed in solutions and polymer matrices plays a crucial role in a wide range of technological applications including additive manufacturing, polymer nanocomposites and drug-delivery. These applications require well-dispersed particles, commonly achieved by grafting polymers to the particle. Understanding and quantifying the perturbation in conformation and dynamics of end-grafted chains, resulting from the surface crowding and by confinement caused by macromolecules and nanoparticles, has been a scientific goal of my research group. We directly measure the structure and dynamics of grafted polymer chains and polymer-grafted nanoparticles using scattering and microscopy techniques. The role of confinement, grafting and interaction between polymer and nanoparticle have significant consequences on the structure of the polymer. Dynamically, the grafted polymers are confined by neighboring chains. Macromolecular crowders increase the osmotic pressure of the solution to compress the grafted polymers and increase the confinement of the grafted polymers. Structurally, the osmotic pressure drives the grafted nanoparticles to aggregate. During aggregation, the grafted polymers introduce a soft repulsion potential that results in a controllable surface-to-surface spacing within the aggregate. Tuning the perturbations of the grafted polymer results in materials with novel structures and dynamic relaxations.