Probing 'nanoconfinement' effects on Tg of high-molecular-weight chains via molecular simulation

A number of experimental studies have reported on distinct alterations in the Tg of ultra-high molecular weight polymers in thin films as compared to polymers at lower molecular weights. These effects include much larger reductions in Tg (when compared at equal film thickness) and even observation of two Tg's. The origin of these new effects at high molecular weight have remained unresolved. In an effort to provide insight into this question, here we report on of simulations of glass formation in bead-spring polymer films comprised of high-molecular-weight entangled chains. We compare alterations in Tg as measured via density vs dynamics, as well as comparing to results in lower molecular weight chains.