Speaker
Description
We use nanoindentation to measure the Young's modulus of thin films of polystyrene stable glass fabricated with the help of physical vapor deposition (PVD). Glasses formed this way exhibit fictive temperatures as low as Tg – 20 K and kinetic stability down to deposition temperatures of ~ 0.84 Tg. The Young's modulus of stable glass films is significantly higher than that of ordinary liquid-cooled glass. The enhancement increases with stability and is as large as 70% greater than the liquid-cooled glass, signifying enhanced packing and mechanical resistance in highly stable films. The observed modulus enhancements are substantially larger than previously reported for organic glasses and are comparable to those measured in certain ultra-aged lunar glasses. Additionally, we studied the mechanical properties of rejuvenated glasses. We systematically measured the Young's modulus of stable glass, as well as partially and fully rejuvenated glass. Partially rejuvenated films show a modulus value intermediate between that of the stable and normal glass. The value of the elastic modulus decreased with an increased percentage of rejuvenation of the film, which is consistent with the front propagation model of rejuvenation. Spatial heterogeneity of the modulus values is investigated and discussed.
| Keyword-1 | Ultrastable polymer glass |
|---|---|
| Keyword-2 | Polystyrene |
| Keyword-3 | Nanoindentation |