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

2. But, also a personal tribute to a teacher
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 9

10. Effect of Cross-Linking on the Free-Volume Properties of Polymer Networks:
Macromolecules 1998, 31,
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., 115, 7260, 2001
J. Chem. Phys., 118, 9420, 2003

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

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

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