<?xml version="1.0" encoding="utf-8"?>
<export-example>
  <doc>
    <id>51147</id>
    <completedYear/>
    <publishedYear>2020</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>6731</pageFirst>
    <pageLast>6739</pageLast>
    <pageNumber/>
    <edition/>
    <issue>15</issue>
    <volume>53</volume>
    <type>article</type>
    <publisherName>American Chemical Society</publisherName>
    <publisherPlace>Washington, DC</publisherPlace>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Molecular mobility of a polymer of intrinsic microporosity revealed by quasielastic neutron scattering</title>
    <abstract language="eng">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) at microscopic time scales 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 three-fold 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 energy for the methyl group rotation for PIM-1 and the polyimide is significantly higher than for conventional polymers.</abstract>
    <parentTitle language="eng">Macromolecules</parentTitle>
    <identifier type="doi">10.1021/acs.macromol.0c00963</identifier>
    <identifier type="issn">0024-9297</identifier>
    <identifier type="issn">1520-5835</identifier>
    <enrichment key="date_peer_review">10.09.2020</enrichment>
    <author>R. Zorn</author>
    <author>W. Lohstroh</author>
    <author>M. Zamponi</author>
    <author>W. Harrison</author>
    <author>P. Budd</author>
    <author>Martin Böhning</author>
    <author>Andreas Schönhals</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Polymer of intrinsic microporosity</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Quasielastic neutron scattering</value>
    </subject>
    <collection role="institutes" number="">6 Materialchemie</collection>
    <collection role="institutes" number="">6.6 Digitale Materialchemie</collection>
    <collection role="institutes" number="">7 Bauwerkssicherheit</collection>
    <collection role="institutes" number="">7.5 Technische Eigenschaften von Polymerwerkstoffen</collection>
    <collection role="themenfelder" number="">Material</collection>
    <collection role="themenfelder" number="">Chemie und Prozesstechnik</collection>
    <collection role="literaturgattung" number="">Verlagsliteratur</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
  </doc>
  <doc>
    <id>55485</id>
    <completedYear/>
    <publishedYear>2022</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>7340</pageFirst>
    <pageLast>7350</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume>55</volume>
    <type>article</type>
    <publisherName>American Chemical Society</publisherName>
    <publisherPlace>Washington, DC</publisherPlace>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Polymers of intrinsic microporosity - Molecular mobility and physical aging revisited by dielectric spectroscopy and X‑ray scattering</title>
    <abstract language="eng">Polymers of intrinsic microporosity (PIMs) are promising candidates for the active layer in gas separation membranes due to their high permeability and reasonable permselectivity. These appealing properties originate from a microporous structure as a result of inefficient segment packing in the condensed state due to a combination of a ladder-like rigid backbone and sites of contortion. However, this class of polymers suffers from a significant decrease in the permeability with time due to physical aging, whereby typically, the permselectivity increases. The initial microporous structures approach a denser state via local rearrangements, leading to the reduction of the permeability. Hence, a detailed characterization of the molecular mobility in such materials can provide valuable information on physical aging. In this work, the dielectric behavior of PIM-1 films and their behavior upon heating (aging) were revisited by isothermal frequency scans during different heating/cooling cycles over a broad temperature range between 133 and 523 K (−140 to 250 °C). In addition, the obtained results were compared with data of samples that were annealed at ambient temperatures over different time scales. Multiple dielectric processes were observed: several relaxation processes due to local fluctuations and a Maxwell−Wagner−Sillars polarization effect related to the microporosity. The temperature dependence of the rates of all processes follows the Arrhenius law where the estimated activation energy depends on the nature of the process. The influence of the thermal history (aging) on the processes is discussed in detail.</abstract>
    <parentTitle language="eng">Macromolecules</parentTitle>
    <identifier type="doi">10.1021/acs.macromol.2c00934</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="date_peer_review">02.09.2022</enrichment>
    <author>Farnaz Emamverdi</author>
    <author>Huajie Yin</author>
    <author>Glen Jacob Smales</author>
    <author>W. J. Harrison</author>
    <author>P. M. Budd</author>
    <author>Martin Böhning</author>
    <author>Andreas Schönhals</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Polymers of intrinsic microporosity</value>
    </subject>
    <collection role="ddc" number="620">Ingenieurwissenschaften und zugeordnete Tätigkeiten</collection>
    <collection role="ddc" number="621">Angewandte Physik</collection>
    <collection role="institutes" number="">6 Materialchemie</collection>
    <collection role="institutes" number="">6.5 Synthese und Streuverfahren nanostrukturierter Materialien</collection>
    <collection role="institutes" number="">6.6 Digitale Materialchemie</collection>
    <collection role="institutes" number="">7 Bauwerkssicherheit</collection>
    <collection role="institutes" number="">7.5 Technische Eigenschaften von Polymerwerkstoffen</collection>
    <collection role="themenfelder" number="">Energie</collection>
    <collection role="themenfelder" number="">Material</collection>
    <collection role="literaturgattung" number="">Verlagsliteratur</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
  </doc>
</export-example>
