Characterizing free volumes and layer structures in polymeric membranes using slow positron annihilation spectroscopy

Y. C. Jean, Hongmin Chen, Sui Zhang, Hangzheng Chen, L. James Lee, Somia Awad, James Huang, Cher Hon Lau, Huan Wang, Fuyun Li, Tai Shung Chung

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Positron annihilation spectroscopy coupled with a newly built slow positron beam at National University of Singapore has been used to study the free volume, pore, and depth profile (0 - 10 μm) in cellulose acetate polymeric membrane at the bottom and top sides of membranes for ionic separation in water purification applications. The S and R parameters from Doppler broadening energy of annihilation radiation representing free volumes (0.1-1 nm size) and pores (>1 nm-μm) as a function of depth have been analyzed into multilayers, i.e. skin dense, transition, and porous layers, respectively. The top side of membrane has large free volumes and pores and the bottom side has a skin dense layer, which plays a key role in membrane performance. Positron annihilation lifetime results provide additional information about free-volume size and distribution at the atomic and molecular scale in polymeric membrane systems. Doppler broadening energy and lifetime spectroscopies coupled with a variable mono-energy slow positron beam are sensitive and novel techniques for characterization of polymeric membrane in separation applications.

Original languageEnglish (US)
Article number012027
JournalJournal of Physics: Conference Series
Issue number1
StatePublished - 2011
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy


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