Cooperative strings in glassy nanoparticles
  Motivated by recent experimental results on glassy polymer nanoparticles, we develop a minimal theoretical framework for the glass transition in spherical confinement. This is accomplished using our cooperative-string model for supercooled dynamics, that was successful at recovering the bulk phenomenology and describing the thin-film anomalies. In particular, we obtain predictions for the mobile-layer thickness as a function of temperature, and for the effective glass-transition temperature as a function of the radius of the spherical nanoparticle - including the existence of a critical particle radius below which vitrification never occurs. Finally, we compare the theoretical results to experimental data on polystyrene from the recent literature, and we discuss the latter. 
Maxence Arutkin, Elie Rapha\"el, James A. Forrest, Thomas Salez
cond-mat.stat-mech cond-mat.dis-nn cond-mat.mes-hall cond-mat.soft physics.chem-ph