par Richardson, Hugh;Lopez-Garcia, I.;Sferrazza, Michele 
;Keddie, J. L.
Référence Physical review. E, Statistical, nonlinear, and soft matter physics, 70, page (051805)
Publication Publié, 2004
;Keddie, J. L.Référence Physical review. E, Statistical, nonlinear, and soft matter physics, 70, page (051805)
Publication Publié, 2004
Article révisé par les pairs
| Résumé : | The isothermal structural relaxation of glassy, spin-cast polymer thin films has been investigated. Specifically, the thickness [Formula presented] of freshly cast poly(methyl methacrylate) thin films was measured over time using spectroscopic ellipsometry. The spin-cast films exhibit a gradual decrease in thickness, which is attributed to structural relaxation of the glass combined with simultaneous solvent loss. In all cases, [Formula presented] was found to be greater than the equilibrium thickness [Formula presented], which is obtained by cooling slowly from the melt. It is observed that both the rate of the volume relaxation and the fractional departure from [Formula presented] (referred to as [Formula presented]) increase with increasing film thickness. In the limit of very thin films, the initial [Formula presented] is close to [Formula presented], and [Formula presented] is small, whereas in thick films [Formula presented], a plateau value of [Formula presented] of 0.16 is observed, which is close to the volume fraction of the solvent at the vitrification point. This dependence of [Formula presented] on thickness is observed regardless of the substrate, polymer molecular weight, or angular velocity during spin casting. Enhanced mobility near film surfaces could be leading to greater relaxation in thinner films prior to, and immediately after, the vitrification of the polymer during the deposition process. © 2004 The American Physical Society. |
