Glassy Dynamics of Polymers Under Soft and Hard Confinement

An immense amount of research has been devoted to understanding the impact of nanoscale confinement on the glass transition temperature (Tg) and physical aging of thin polymer films. When a polymer is confined to the nanoscale, Tg and physical aging can differ substantially from the bulk. When discussing nanoscopically-confined polymer, two effects are generally highlighted: (i) size effects and (ii) interfacial effects. Size effects are purported to occur when the length-scale of the confining dimension and the length scale governing the property coincide. Interfacial effects are expected to increase in significance with an increase in the ratio of interfacial area to volume. The interplay between size and interfacial effects can in general result in substantial increases or decreases in the Tg, and suppressed or reduced aging. Factors that influence the deviation in Tg and physical aging with confinement include geometry, strength of interfacial interactions, sample preparation, and chemical structure. We advance the current understanding of how confinement impacts Tg and physical aging by undertaking studies on polymers under soft and hard confinement. This is achieved via calorimetry studies on polymer nanoparticles (soft confinement) and polymer-silica core shell nanoparticles (hard confinement) suspended in solution.