Comment on "Viscoelastic properties of confined polymer films measured via thermal wrinkling" by E. P. Chan, K. A. Page, S. H. Im, D. L. Patton, R. Huang, and C. M. Stafford, Soft Matter, 2009, 5, 4638-4641
Abstract
In the original paper using the thin film wrinkling technique, results were presented for the rubbery plateau modulus and viscosity of a polystyrene (PS) material having a molecular mass of approximately 600 kg mol 1. The wrinkling technique itself, for the elastic case, is fully described in a number of previous publications. The comments are concerned with the viscoelastic analysis and the data presented for the polystyrene relative to that in the macroscopic state. In particular, we show that there is an error of several orders of magnitude in the reported macroscopic viscosity for the PS and these were, seemingly, consistent with the thin film results. This suggests that the method is not refined enough to provide viscoelastic data in the long time regime of polymers. We also show that the values of the rubbery modulus determined for the thin polymer film are highly sensitive to the assumptions made for the Poisson's ratio of the polymer in the (nearly incompressible) rubbery state. The viscosity estimates are also sensitive to the assumed value of Poisson's ratio, but not sufficiently to explain the orders of magnitude differences with literature reports. Because of issues with the constrained thin film analysis, we examine here an analysis of the data using a conventional analytical solution for a thick compliant layer, i.e. where the material is not confined, and again find that the results for the PS film are not consistent with measured bulk properties. This suggests that these thin film wrinkling experiments may be in a region where the confinement is not well defined and/or that further refinement to the reported viscoelastic model is required to fully capture the viscoelastic properties of confined polymer films.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2011
- Accession Number
- ADA579259
Entities
People
- Christopher M. Stafford
- Edwin P Chan
- Gregory B. McKenna
- Paul A. O'connell
Organizations
- National Institute of Standards and Technology