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Positron annihilation and free volume related issues in polymeric systems :

Positron annihilation and free volume related issues in polymeric systems : a Sketch of Günter Dlubek's contributions. Ashraf Alam Physics, University of Bristol. A tribute on behalf of the positron community. But, also a personal tribute to a teacher. Bristol 1989. Bristol 1999.

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Positron annihilation and free volume related issues in polymeric systems :

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  1. Positron annihilation and free volume related issues in polymeric systems : a Sketch of Günter Dlubek's contributions Ashraf Alam Physics, University of Bristol

  2. A tribute on behalf of the positron community But, also a personal tribute to a teacher

  3. Bristol 1989

  4. Bristol 1999 Bristol 2004

  5. PSPA 2004 PSPA 2007

  6. PSPA 2010 – last conference attended

  7. Gűnter’s start with polymer: • understanding of the size / size distribution of the free volume holes • what is feasible to measure/analyse and more importantly what is not realistic (e.g Bimodal distribution? – more than one polymer phases?) Earliest papers on polymers Positron lifetime studies of free volume hole size distribution in glassy polycarbonate and polystyrene, phys. stat. sol. (a) 157, 351 (1996) Positron lifetime studies of free volume hole size distribution in amorphous and in semi-crystalline polymers, J. Rad. & Nucl. Chem. 211, 69 (1996)

  8. Important contribution themes: • hole volume vs ‘states / compostions’ of polymers: • deformed • co-polymers, cross linking, branching • partially crystalline • Microscopic hole volume vs. macrosocopic volume • (specific volume: density, PVT measurements) Number density of holes and related issues • Chemical environments of the local free volume

  9. Most important contribution, in my view is • in the understanding the practical implications of • free volumes in : • Diffusion related issues mediated by free volumes • Ionic conductivity in electrolyte polymers • Polymer dynamics • PVT, Simha-Somcynski eq. of state, free volume etc. • Cohen-Turnbull & structural relaxation: • Free Volume Fluctuations & Dynamic Heterogeneity In the following, a selection of examples

  10. Effect of Cross-Linking on the Free-Volume Properties of Polymer Networks: Macromolecules 1998, 31, 4574-4580 Macromolecules, 31, No. 14, 1998

  11. Probe for the Chemical Environment of Free Volume Holes in Polymers Based on simple S-parameter like approach (faster estimation) Macromolecules, 33, No. 1, 2000

  12. Probe for the Chemical Environment of Free Volume Holes in Polymers Based on simple S-parameter like approach (faster estimation) Macromolecules, 33, 187, 2000 Polymer 47 , 3486, 2006

  13. Diffusion & free volume: ionic conductivity in a polymer electrolyte J. Chem. Phys., 118, 9420, 2003 J. Chem. Phys., 115, 7260, 2001

  14. Diffusion & free volume: ionic conductivity in a polymer electrolyte Extended Cohen-Turnbull free volume theory + Nernst-Einstein eq: J. Chem. Phys., 118, 9420, 2003 J. Chem. Phys., 115, 7260, 2001

  15. PVT, Simha-Somcynski equation of state, free volume etc. Polymer, 46, 859, 2005 Polymer, 46, 869, 2005

  16. Miscellaneous Mean hole volume vs Tg /groups of polymers Compilation from a number of Dlubek Authored papers Pressure densification e-Polymers, no 108, 1 - 20 (2007d).

  17. Free volume & polymer dynamics Free volume & structural relaxation: Macromol. Chem. Phys. 207, 721, 2006

  18. Free Volume Fluctuations & Dynamic Heterogeneity • Polymer dynamics! • Movements of molecular segments (relaxations) : • High T ‘a-relaxation above cross-over T • Below a ‘cross-over’ T • A fast -process : Arrhenius T-dependence; thermally activated and segment mobility independent of surrounding • A slower a-process: non-Arrhenius T dependence • physical origin of the non-Arrhenius behavior  locally heterogeneous dynamics

  19. Free Volume Fluctuations & Dynamic Heterogeneity • mobility governed by cooperative movement of several molecular segments in a localised volume – the cooperatively rearranging region (CRR) • CRR • Composed of ‘an island’ of high mobility (Glarum-Levy defect) • surrounded buy a shell of lower mobility. The smallest sub • system related to relaxation • Glarum-Levy defect  free volume hole?

  20. Free Volume Fluctuations & Dynamic Heterogeneity Free Volume Fluctuations & Dynamic Heterogeneity

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