Dramatic Modification of Nanoparticle Surface Mobility in Polymer Colloids with a Core-Shell Structure

Advances in polymer nanoparticle synthesis and assembly techniques have enabled new applications, from drug delivery carriers to novel coatings. However, the thermal transition of polymer dynamics, especially at the particle surfaces, must be understood in order to realize their potential. Using Brillouin light scattering as a direct probe of the particle surface mobility via polymer nanoparticle vibrations, recent experiments confirm the correlation between the glass transition behavior and surface dynamics of polymer nanoparticles. This raises a challenge of how the glass transition dynamics of polymer nanoparticles can be engineered. To address this need, we modify the surface condition of polystyrene nanoparticles with different shell architecture layers. We demonstrate that a shell layer composed of two polyelectrolytes, as thin as a single polymer chain, is able to eliminate the effect of enhanced particle surface mobility. Other shell structures, such as a single polyelectrolyte layer, enables tailoring the glass transition temperature, softening behavior, and elasticity of the nanoparticles.