Positron Annihilation: A New Method for Studying Subnanometer-Size Local Free Volumes in Polymers
- Prof. T. W. Clyne and
- F. Simancik
Published Online: 21 DEC 2005
Copyright © 2000 Wiley-VCH Verlag GmbH, Weinheim
Metal Matrix Composites and Metallic Foams, Volume 5
How to Cite
Dlubek, G., Fretwell, H. M. and Meyendorf, N. (2000) Positron Annihilation: A New Method for Studying Subnanometer-Size Local Free Volumes in Polymers, in Metal Matrix Composites and Metallic Foams, Volume 5 (eds T. W. Clyne and F. Simancik), Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, FRG. doi: 10.1002/3527606203.ch43
Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB2 3QZ, U.K.
- Published Online: 21 DEC 2005
- Published Print: 20 APR 2000
Print ISBN: 9783527301263
Online ISBN: 9783527606207
- positron annihilation;
- subnanometer-size local free volumes in polymers
Positron/positronium annihilation spectroscopy is a unique tool to probe free-volume holes which appear in amorphous polymers due to the irregular molecular packing. The positron lifetime spectroscopy provides information on the mean hole size and on the hole size distribution which may be studied as a function of temperature, content of plasticizer or humidity, composition of copolymers and blends etc. Typical hole sizes lie in the range r = 0.2–0.4 nm and v = 0.05–0.4 nm3. By comparing the coefficients of thermal expansion of specific and of hole volume in PE and PTFE, a fractional free (hole) volume at Tg of ∼5 % and a hole number of 0.5–1 nm–3 are estimated. The variation of the hole volume with composition is studied for CR39- and ethylene-vinyl acetate (EVA) copolymers.