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Interplay between dewetting and layer inversion in poly(4-vinylpyridine)/polystyrene bilayers

Citation

Thickett, SC and Harris, A and Neto, C, Interplay between dewetting and layer inversion in poly(4-vinylpyridine)/polystyrene bilayers, Langmuir, 26, (20) pp. 15989-15999. ISSN 0743-7463 (2010) [Refereed Article]

Copyright Statement

Copyright 2010 American Chemical Society

DOI: doi:10.1021/la103078k

Abstract

We investigated the morphology and dynamics of the dewetting of metastable poly(4-vinylpyridine) (P4VP) thin films situated on top of polystyrene (PS) thin films as a function of the molecular weight and thickness of both films. We focused on the competition between the dewetting process, occurring as a result of unfavorable intermolecular interactions at the P4VP/PS interface, and layer inversion due to the lower surface energy of PS. By means of optical and atomic force microscopy (AFM), we observed how both the dynamics of the instability and the morphology of the emerging patterns depend on the ratio of the molecular weights of the polymer films. When the bottom PS layer was less viscous than the top P4VP layer (liquid−liquid dewetting), nucleated holes in the P4VP film typically stopped growing at long annealing times because of a combination of viscous dissipation in the bottom layer and partial layer inversion. Full layer inversion was achieved when the viscosity of the top P4VP layer was significantly greater (>104) than the viscosity of the PS layer underneath, which is attributed to strongly different mobilities of the two layers. The density of holes produced by nucleation dewetting was observed for the first time to depend on the thickness of the top film as well as the polymer molecular weight. The final (completely dewetted) morphology of isolated droplets could be achieved only if the time frame of layer inversion was significantly slower than that of dewetting, which was characteristic of high-viscosity PS underlayers that allowed dewetting to fall into a liquid−solid regime. Assuming a simple reptation model for layer inversion occurring at the dewetting front, the observed surface morphologies could be predicted on the basis of the relative rates of dewetting and layer inversion.

Item Details

Item Type:Refereed Article
Research Division:Chemical Sciences
Research Group:Physical Chemistry (incl. Structural)
Research Field:Colloid and Surface Chemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
Author:Thickett, SC (Dr Stuart Thickett)
ID Code:99416
Year Published:2010
Web of Science® Times Cited:18
Deposited By:Chemistry
Deposited On:2015-03-23
Last Modified:2015-04-27
Downloads:0

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