Nanoparticle effect on multiscale polymer dynamics in nanocomposites: insights from neutron and x-ray spectroscopy

Dynamics of polymers in presence of nanoparticles has attracted much attention due to immediate consequences on the rheological behavior of polymer nanocomposites. Bulk techniques are usually insufficient to study the component dynamics mainly due to lack of space-time resolution required for intrinsically complex relaxation mechanisms. In our studies, we applied extensive neutron and x-ray scattering techniques, specifically backscattering, neutron spin echo, and x-ray photon correlation spectroscopy to gain microscopic insight on the role of nanoparticle size, shape, loading, dispersion state, polymer-particle interfaces and confinement on multiscale polymer dynamics as well as on slow nanoparticle relaxation in attractive nanocomposites [1, 2]. These interconnected and often competing effects result in the unusual rheological behavior, the origin of which has long been debated. By simultaneously accessing time scales from sub-nanosecond to hundreds of nanoseconds, and length scales from monomers to entanglement spacing, we directly measured the key dynamical parameters- Rouse rate and reptation tube size- in nanocomposites, and correlated them with the macroscopic mechanical relaxation and the nanoscale particle motion [3].

[1] Senses, E. et al. Physical review letters 2017, 118, 147801
[2] Senses, E. et al. ACS Nano 2018, 12, 10807-10816
[3] Senses, E. et al. Physical review letters 2017, 119, 237801