Description: Molecular Mobility of a Polymer of Intrinsic Microporosity Revealed by Quasielastic Neutron Scattering

This title appears in the Scientific Report : 2020

Molecular Mobility of a Polymer of Intrinsic Microporosity Revealed by Quasielastic Neutron Scattering

Quasielastic neutron scattering by employing a combination of time-of-flight and backscattering techniques is carried out to explore the molecular mobility of a polymer of intrinsic microporosity (PIM-1) on microscopic timescales in comparison with a high-performance polyimide. Molecular fluctuation...

Personal Name(s):	Zorn, Reiner
	Lohstroh, Wiebke / Zamponi, Michaela / Harrison, Wayne J. / Budd, Peter M. / Böhning, Martin / Schönhals, Andreas (Corresponding author)
Contributing Institute:	Neutronenstreuung; JCNS-1 JCNS-4; JCNS-4 JCNS-FRM-II; JCNS-FRM-II Neutronenstreuung und biologische Materie; IBI-8
Published in:	Macromolecules, 53 (2020) 15, S. 6731 - 6739
Imprint:	Washington, DC Soc. 2020
DOI:	10.1021/acs.macromol.0c00963
Document Type:	Journal Article
Research Program:	FRM II / MLZ Soft Matter, Health and Life Sciences Functional Macromolecules and Complexes Jülich Centre for Neutron Research (JCNS)
Subject (ZB):	Soft Condensed Matter > 0 Polymers, Soft Nano Particles and Proteins > 0
Link:	Restricted Published on 2020-07-27. Available in OpenAccess from 2021-07-27.
	Publikationsportal JuSER

Please use the identifier: http://dx.doi.org/10.1021/acs.macromol.0c00963 in citations.
Please use the identifier: http://hdl.handle.net/2128/26623 in citations.

Quasielastic neutron scattering by employing a combination of time-of-flight and backscattering techniques is carried out to explore the molecular mobility of a polymer of intrinsic microporosity (PIM-1) on microscopic timescales in comparison with a high-performance polyimide. Molecular fluctuations can change the structure of the temporary network of micropores and open or close pathways for gas molecules. Therefore, the investigation might help to understand the selectivity of PIMs in gas separation processes. The performed neutron scattering experiments provide evidence for a low-temperature relaxation process, which was assigned to methyl group rotation. This methyl group rotation was analyzed in terms of jump diffusion in a threefold potential. The analysis results in a fraction of methyl groups, which are immobilized. For PIM-1, it was found that the fraction of immobilized methyl groups decreases with increasing temperature up to 350 K. At higher temperatures, the number of immobilized methyl group increases gain due to an underlying relaxation process. This motional process on a somewhat larger length scale might lead to a reversible structural rearrangement, which partially hinders the strongly localized methyl group rotation. In addition, it was found that the activation energies for the methyl group rotation for PIM-1 and the polyimide are significantly higher than that for conventional polymers.