AI Article Synopsis
- A normal-mode analysis was conducted on glass-forming polymer systems, comparing bulk and free-standing film geometries prepared in the same way.
- The free-standing films showed significant differences in their normal-mode spectrum, including a new low-frequency peak and increased intensity at the Boson peak frequency.
- An eigenvector analysis linked the low-frequency peak to shear-horizontal modes, while the Boson peak related to motions across a length scale double the interaction site diameter, providing insights into the dynamics of glass formers and addressing reduced fragility in thinner films.
Article Abstract
We have performed a normal-mode analysis on a glass forming polymer system for bulk and free-standing film geometries prepared under identical conditions. It is found that for free-standing film glasses, the normal-mode spectrum exhibits significant differences from the bulk glass with the appearance of an additional low-frequency peak and a higher intensity at the Boson peak frequency. A detailed eigenvector analysis shows that the low-frequency peak corresponds to a shear-horizontal mode which is predicted by continuum theory. The peak at higher frequency (Boson peak) corresponds to motions that are correlated over a length scale of approximately twice the interaction site diameter. These observations shed some light on the microscopic dynamics of glass formers, and help explain decreasing fragility that arises with decreasing thickness in thin films.
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| http://dx.doi.org/10.1063/1.1689952 | DOI Listing |
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