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Dewetting induced by complete versus nonretarded van der Waals forces
Heping Zhao1, Yong Jian Wang, Ophelia K C Tsui
1Institute of Nano Science and Technology and Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 15, 2005
Summary
Spontaneous polymer film rupture is linked to free energy curvature. This study reveals that van der Waals interactions, even in thin films, are significantly affected by retardation effects, challenging prior assumptions.
Area of Science:
- Materials Science
- Surface Science
- Polymer Physics
Background:
- Spontaneous rupture of polymer films during heating is a common phenomenon.
- This instability is governed by the system free energy (G(L)) exhibiting negative curvature.
- Van der Waals (vdW) interactions are critical for apolar films (< or = 100 nm), often approximated without considering retardation effects.
Purpose of the Study:
- To investigate the limitations of the approximated van der Waals interaction formula in polymer films.
- To calculate complete vdW interactions using the Dzyaloshinskii, Lifshitz, and Pitaevskii (DLP) theory.
- To assess the impact of retardation effects on free energy in thin polymer films.
Main Methods:
- Utilized the Dzyaloshinskii, Lifshitz, and Pitaevskii (DLP) theory for calculations.
- Computed complete van der Waals interactions for specific polymer film systems.
- Analyzed systems including air-polystyrene-SiO2-Si, air-polystyrene-poly(methyl methacrylate)-Si, and air-poly(methyl methacrylate)-polystyrene-Si.
Main Results:
- Retardation effects significantly modify the system free energy G(L).
- These modifications are substantial even for polymer and/or interlayer thicknesses as small as 1-2 nm.
- The widely used approximation for vdW interactions, ignoring retardation, is shown to be inadequate in these cases.
Conclusions:
- The conventional assumption that retardation effects are negligible in thin polymer films is challenged.
- Accurate modeling of van der Waals interactions in polymer films requires incorporating retardation effects.
- Understanding these interactions is crucial for predicting and controlling polymer film dewetting and rupture phenomena.
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