We have measured the positron annihilation lifetime spectra in an epoxy polymer using the electrotechnical laboratory (ETL) slow-positron facility as a function of positron energy from 0.2 to 3.0 keV. The ortho-positronium lifetime from the bulk increases near the surface while the intensity decreases. The results are interpreted in terms of a Ps free-volume model. A larger hole size and fraction near the polymeric surface are observed. A reduction of glass transition temperature near the surface is estimated from the WLF theory.
CITATION STYLE
Jean, Y. C., Cao, H., Dai, G. H., Suzuki, R., Ohdaira, T., Kobayashi, Y., & Hirata, K. (1997). Free-volume hole properties near the surface of polymers obtained from slow positron annihilation spectroscopy. Applied Surface Science, 116, 251–255. https://doi.org/10.1016/S0169-4332(96)01064-1
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