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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster Session II

CPP 35.17: Poster

Wednesday, March 29, 2023, 11:00–13:00, P1

Positrons probe advanced and functionalized porous materials — •Ahmed Gamal Attallah, Eric Hirschmann, Maik Butterling, Maciej Oskar Liedke, and Andreas Wagner — Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf

Positron annihilation lifetime spectroscopy (PALS) is an effective porosimetry technique complementing standard gas intrusion methods. PALS is able to detect open and closed pores, and resolve depth-dependent porosity. It can operate under variable pressures, temperatures, and atmospheres to monitor structural changes during in situ conditions. In this contribution, PALS results of various functionalized porous materials including polymer grating, structural changes in metal-organic-frameworks (MOFs), effect of additives in food ingredients (maltodextrin) on water uptake, and impact of modification of low-k dielectrics on stiffness will be presented. In polymer grafting, the mechanism of polymer grafting on MCM-48-type mesoporous silica nanoparticles forming core-shell composite structure is understood from PALS. Uniquely in MOFs, PALS was able to prove that the temperature-driven transformed metal-organic framework DUT-8(Ni) is still porous possessing closed porosity that is not accessible by other techniques. Sucrose in maltodextrin is the third topic where in situ humidity experiment during PALS revealed that adding 10 % sucrose to maltodextrins has a negligible effect on hygrocapacity at relative humidity > 50 %. Finally, the improved mechanical stability of low-k materials by adding methyl terminal groups that cause less interconnected pores has been verified by positron annihilation.