Regensburg 2013 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: Poster: Colloids and Complex Liquids
CPP 20.33: Poster
Dienstag, 12. März 2013, 18:15–20:15, Poster C
Positron annihilation lifetime spectroscopy in a porous liquid — •Tönjes Koschine1, Klaus Rätzke1, Nicola Giri2, and Stuart L. James2 — 1Christian-Albrechts-Universität Kiel, Institute for Material Science - Multicomponent Materials, Kaiserstraße 2, Kiel, Germany — 2School of Chemistry and Chemical Engineering, Queen's University Belfast, Stranmilis Road, Belfast, Northern Ireland
Porous liquids (PL), or liquids with intrinsic porosity, are a new type of material [1]. In contrast to well known cavities between molecules of a liquid (extrinsic porosity), intrinsic porosity refers to empty voids within the molecules. The materials are composed of rigid cages to which short hydrocarbon tails or cyclic crown ethers are attached to endow liquid-like behavior, or very high solubility in liquid crown ether solvents respectively. The main question is whether such side groups or solvent molecules remain outside the cage cavities or whether they are able to occupy the cage cavities over time. Positron annihilation lifetime spectroscopy (PALS) is a suitable tool to detect empty pores in the sub-nanometer range. The measured orthopositronium lifetime is directly related to the pore size by the Tao-Eldrup model. Two different series of PL were studied at various temperatures by PALS to find evidence for permanent intrinsic porosity. A detailed analysis of the spectra as function of temperature, involving both PL and control materials, allowed clear separation of the lifetime due to the side groups and lifetime due to the empty pores in the PL. Thus, we were able to prove that the pores in these liquids are indeed permanently empty.
[1]O Reilly, N.; Giri, N.; James, S.L.:Chem.Eur.J.,13,2007,3020-3025.