The Effect of Surface Interactions on the Viscosity of Polymer Thin Films
- PDF / 79,064 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 17 Downloads / 241 Views
0890-Y06-03.1
The Effect of Surface Interactions on the Viscosity of Polymer Thin Films Chunhua Li∗, Jun Jiang, Miriam H. Rafailovich, Jonathan C. Sokolov Department of Material Science and Engineering, SUNY at Stony Brook, Stony Brook, NY, 11794-2275 ABSTRACT Previously, we reported that the viscosity of a polymer film can be measured in situ by observing the liquid-liquid dewetting of polymer bilayer films. In this study, we use the technique to investigate the effect of film thickness and surface interactions on the effective viscosity of polymer thin films. We found that the effective viscosity increases dramatically with decreasing the film thickness. We attribute this to the pinning of the polymer chains at the strongly interacting polymer/Silicon interface. INTRODUCTION It is well known that the solid surface strongly affects the diffusion dynamics of polymer thin films. For instance, X. Zheng [1] measured tracer diffusion constant of polymer chains near an attractive solid interface by secondary ion mass spectrometry (SIMS), he scaled D as N-3/2, which is in good agreement with the modified reptation model to account for the effect of N1/2 surface-monomer contacts. Using the same technique, he further reported the diffusion constant can be an order of magnitude slower than its bulk counterpart even persists up to 10 Rg [2]. Additionally, Z. Li [3] extracted the surface diffusion coefficient by measuring the time dependence of surface corrugation amplitude and the diffusion constants were also found to be an order of magnitude lowers than bulk due to the surface confinement effect of the polymer chains. Neutron Reflectivity (NR) is also applied to study the interdiffusion of polymer thin films, which provides a nondestructive way and better resolution for thinner films. Eric K. Lin [4,5] observed the reduced polymer mobility near the polymer/solid surface by Neutron Reflectivity. For the film less than Rg, the diffusion constant is 2 orders of magnitude smaller than the thickest films. Recently, Scanning Force Microscopy (SFM) was also introduced to study the surface interaction effect by measuring the nanomechanical properties. The surface effect was observed to propagate to a distance of 7-10 Rg [6]. In summary, these previous experiments shows that the diffusion of polymer chain dramatically decreases at attractive surface and this effect can persist to the distance much farther than the radius of gyration Rg. Based on Einstein’s relationship D∼KBT/η, Diffusion constant is inversely related to the viscosity polymer thin film. It is therefore reasonable for us to expect the viscosity of polymer thin film increases near the solid substrate as the diffusion constant decrease. In a previous work, we designed an in situ viscometer to measure the thin film viscosity by using the fundamental theories of bilayer dewetting [7]. In this work, we use the technique to investigate the surface interaction effect on the effective viscosity of polymer thin
0890-Y06-03.2
films. Our viscometer was designed based on a bi
Data Loading...
