Liquid dewetting of ultrathin polystyrene films: Is there a molecular architecture effect?

We have used a liquid dewetting method to investigate the glass transition temperature T-g of high molecular weight linear, long branched 3-arm star, and short branched 8-arm star polystyrene (PS) in the form of ultrathin films. The results of these dewetting experiments are consistent with prior studies of dewetting of linear PS films and show that, independent of molecular architecture, the glass transition temperature T-g reductions with decreasing film thickness, while important below about 20 nm, are weaker than those observed for linear PS supported on a rigid substrate and as well as those observed in freely standing films. The lack of a strong molecular architecture effect on the T-g-reductions is consistent with the T-g reductions for the dewetting from a liquid substrate reflects changes in segmental dynamics upon confinement rather than chain effects. This contrasts with changes, including increases seen in dewetting from a rigid substrate, for different molecular architectures reported in the literature.

Automated summary

The glass transition temperature T-g reductions with decreasing film thickness are weaker for different molecular architectures, suggesting that changes in segmental dynamics upon confinement rather than chain effects play a more significant role in the dewetting process.