Harnessing Nanoparticle Vibrations to Probe Surface Mobility and Glass Transition

Advances in polymer nanoparticle synthesis and assembly techniques have enabled new applications, from drug delivery carriers to coatings. However, the polymer dynamics, especially at the nanoparticle surfaces of architected colloids, must be understood in order to realize their potential. Brillouin light spectroscopy, as a direct probe of the particle surface mobility via nanoparticle vibrations, reveals the correlation between the glass transition behavior and surface dynamics, and the presence of a low frequency mode extremely sensitive to particle-particle interactions. These are enabled by the surface mobility which can be engineered by different shell architecture layers. We demonstrate that irreversibly adsorbed layer atop soft and hard nanoparticles is able to eliminate the effect of enhanced particle surface mobility and drastically modify the structure of nanoparticle assembly. Furthermore, this surface mobility can be strongly affected by the application of gas pressure enabling a facile soldering of the colloidal film.