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Surface self-diffusion of an organic glass.
L Zhu1, C W Brian, S F Swallen
1Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Physical Review Letters
|July 21, 2011
Summary
This study measured surface self-diffusion in organic glass for the first time. Surface diffusion is significantly faster than bulk diffusion, driving surface evolution in organic glasses.
Area of Science:
- Materials Science
- Physical Chemistry
- Surface Science
Background:
- Organic glasses exhibit unique properties relevant to various applications.
- Understanding surface dynamics is crucial for predicting material behavior and performance.
- Previous studies have not directly measured surface self-diffusion in organic glasses.
Purpose of the Study:
- To quantify surface self-diffusion in an organic glass.
- To compare surface diffusion rates with bulk diffusion.
- To elucidate the primary mechanisms governing surface evolution in organic glasses.
Main Methods:
- Fabrication of 1000 nm surface gratings on indomethacin, an organic glass.
- Analysis of grating flattening via viscous flow and surface diffusion.
- Temperature-dependent measurements above and below the glass transition temperature.
Main Results:
- Surface self-diffusion was measured for an organic glass for the first time.
- Flattening occurred via viscous flow above the glass transition temperature (Tg + 12 K).
- Surface diffusion dominated at lower temperatures, being at least 10^6 times faster than bulk diffusion.
Conclusions:
- Surface diffusion is a highly mobile process in organic glasses.
- Surface diffusion is the dominant mechanism for surface evolution at micro- to nanoscale.
- This finding has implications for the stability and processing of organic materials.
