Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Interfaces and Thin Films II
CPP 7.2: Vortrag
Montag, 14. März 2011, 14:15–14:30, ZEU 114
Free volume and aging in polymers of intrinsic microporosity (PIM) — •Stephan Harms1, Klaus Rätzke1, Franz Faupel1, Werner Egger2, Luca Ravelli2, Nhamo Chaukura3, and Peter Budd3 — 1Christian-Albrechts University at Kiel, Institute for Materials Science - Multicomponent Materials, 24143 Kiel — 2University of Armed Forces, 85577 Neubiberg — 3University of Manchester, Manchester M13 9PL, UK
Recently developed polymers of intrinsic microporosity (PIM) are suitable candidates as state-of the art gas separation membranes. However, as thin films, like other high free volume polymers, they can undergo aging which means that permeability and free volume become time-dependent and are reduced after prolonged storing and operation time. To investigate the time dependence of free volume, positron annihilation lifetime spectroscopy (PALS) at the pulsed low energy positron system (PLEPS) at FRM II has been performed. The PLEPS setup allows the measurement of depth profiles of the free volume for thin film samples. PIM films of different thickness and preparation method were investigated at two aging times. For all samples we could detect a time dependent decrease of the free volume compare to the bulk reference value. Samples with thickness ≥ 1300 nm do not show a homogeneous reduction of free volume but a steep gradient to the surface of the film. These experiments give valuable information for understanding aging phenomena in high free volume materials.