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Relaxation of a rubbed polystyrene surface.
Alexander D Schwab1, Ali Dhinojwala
1Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA.
Summary
Surface relaxation dynamics of rubbed polystyrene (PS) were studied using SFG spectroscopy. The PS surface exhibits faster relaxation than the bulk, with a distinct surface layer approximately 12 nm thick.
Area of Science:
- Polymer Science
- Surface Science
- Spectroscopy
Background:
- Understanding polymer surface dynamics is crucial for material properties.
- Previous studies on polystyrene (PS) relaxation dynamics have provided bulk insights.
Purpose of the Study:
- To characterize the relaxation dynamics of rubbed polystyrene (PS) surfaces.
- To compare surface relaxation with bulk properties of PS.
Main Methods:
- Infrared-visible sum frequency generation (SFG) spectroscopy was employed.
- SFG results were correlated with prior relaxation of retardation measurements.
Main Results:
- The rubbed PS surface shares the same glass transition temperature (T(g)) as the bulk (defined as tau(T(g))=5 s).
- The surface layer exhibits a lower activation energy (deltaE) and a larger stretching exponent (beta(KWW)) compared to bulk PS.
- A distinct surface region with these altered relaxation parameters was identified, estimated to be around 12 nm thick.
Conclusions:
- The surface region of rubbed PS relaxes more rapidly than the bulk.
- The observed differences in deltaE and beta(KWW) highlight unique surface relaxation mechanisms in polymers.