Material World Network: Dynamics in Polymer Nanocomposites Containing Hard, Soft and Mobile Nanoparticles

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

TECHNICAL SUMMARY: Nanoparticles can impart polymers with unique mechanical and functional properties while also having dramatic effects on how nanoparticles and polymers move. Unlike traditional polymer composites, nanocomposites contain nanoscale particles that are smaller than the radius of gyration of the polymers and this presents a variety of new underlying questions in polymer physics. The dynamics of nanoparticles and polymers are fundamentally important to the processability, dispersion and properties of polymer nanocomposites. Recent reports have found a variety of unexpected, and even inconsistent, results about dynamics in polymer nanocomposites as measured by rheology, neutron scattering methods, and polymer melt diffusion. This Materials World Network project will provide fundamental understanding of dynamics in the presence of spherical nanoparticles (3-100 nm) using complementary experimental and simulation tools. Three research aims correspond to three classes of nanoparticles: hard nanoparticles with just surface functionalization, soft nanoparticles with grafted polymer chains, and mobile nanoparticles. This US and United Kingdom team has expertise spanning polymer science, including nanoparticle functionalization, synthesizing grafted nanoparticles, nanocomposite fabrication and morphology characterization, polymer diffusion studies, neutron scattering, self-consistent field calculations, and simulations by molecular dynamics and dissipative particle dynamics. The team will participate in monthly teleconferences and exchange visits to both institutions by the PI, CoPIs, and their students, as well as joint trips to neutron scattering facilities in Europe. NON-TECHNICAL SUMMARY: Nanoparticles can impart polymers with unique mechanical and functional properties, while also having dramatic effects on how nanoparticles and polymers move in polymer nanocomposites. Brownian motion describes the random motion of gases that is dominated by collisions between gas molecules. Polymer molecules can be thousands of times larger much gas molecules and when surrounded by and entangled with other polymers they typically move by the reptation mechanism, a snake-like motion that involves moving along the contour of the polymer. This widely accepted mechanism is insufficient to describe the dynamics in polymer nanocomposites. The motions of nanoparticles and polymers are fundamentally important to the processability, dispersion and properties of polymer nanocomposites. This Materials World Network (MWN) project seeks to provide a fundamental understanding of how nanoparticles and polymers move using complementary experimental and simulation methods. Given the growing industrial importance of polymer nanocomposites, the MWN team will develop a short course to present the fundamentals and the latest research in this rapidly expanding field. The MWN team will have regular scientific exchanges with industrial scientists. The US and United Kingdom researchers all routinely have undergraduates performing research in their groups and this will extend to this project. Finally, the three senior personnel are active in improving the status of women in science and engineering and this international collaboration will enable information exchanges regarding best practices pertaining to identifying, recruiting, developing and retaining women students and faculty. This project is supported by the Polymers Program and the Office of Special Programs in the Division of Materials Research.