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Confined Segmental Diffusion in Nanophase Separated Janus Polynorbornenes as Investigated by Quasielastic Neutron Scattering
- A combination of neutron time-of-flight and neutron backscattering spectroscopy was used to investigate the molecular dynamics of Janus polynorbornenes (Janus poly(tricyclononenes)) on a microscopic level.
These Janus polynorbornenes, denoted as PTCNSiOR, have a semirigid backbone with −Si(OR)3 side groups attached to it. R represents the length of the alkyl side chain. Here side chain lengths of R = 3 (propyl) and R = 8 (octyl) were considered. It is worth mentioning that these polymers have some potential as active layers in gas separation membranes, especially for the separation of higher hydrocarbons. The combination of time-of-flight and backscattering will ensure a reasonably broad time window for analysis where the incoherent intermediate scattering function SInc(q,t) is considered. Previously, it was shown by X-ray investigations that the system undergoes a nanophase separation into alkyl side chain-rich domains surrounded by a backbone-rich matrix. For PTCNSiOPr (R = 3), theA combination of neutron time-of-flight and neutron backscattering spectroscopy was used to investigate the molecular dynamics of Janus polynorbornenes (Janus poly(tricyclononenes)) on a microscopic level.
These Janus polynorbornenes, denoted as PTCNSiOR, have a semirigid backbone with −Si(OR)3 side groups attached to it. R represents the length of the alkyl side chain. Here side chain lengths of R = 3 (propyl) and R = 8 (octyl) were considered. It is worth mentioning that these polymers have some potential as active layers in gas separation membranes, especially for the separation of higher hydrocarbons. The combination of time-of-flight and backscattering will ensure a reasonably broad time window for analysis where the incoherent intermediate scattering function SInc(q,t) is considered. Previously, it was shown by X-ray investigations that the system undergoes a nanophase separation into alkyl side chain-rich domains surrounded by a backbone-rich matrix. For PTCNSiOPr (R = 3), the alkyl side-chain-rich domains are truly isolated in the backbone-rich matrix, whereas for PTCNSiOOc (R = 8) these domains percolate through the matrix. Further, it was also previously shown that the alkyl side-chain-rich domains undergo a glass transition. The advantage of neutron scattering experiments discussed here is that besides temporal also spatial information is obtained which will allow conclusions to be drawn about the type of molecular fluctuations. At the lowest measured temperature, the decay in Sinc(q,t) is due to the methyl group rotation. The methyl group dynamics is analyzed in terms of a modified jump-diffusion in a 3-fold potential and yields to a reasonable fraction of hydrogens which contribute to the methyl group rotation. At higher temperatures, the decay in SInc(q,t) is due to both the methyl group rotation and the segmental dynamics in the alkyl side-chain-rich domains. The segmental diffusion is modeled by a sublinear diffusion. For the analysis of the scattering function SInc(q,t) of PTCNSiOPr an elastic scattering due to the immobilized backbone-rich matrix must be taken into account. The analysis reveals that the segmental dynamics is confined by the finite size of alkyl chain-rich domains and that it is intrinsically heterogeneous in nature. Both effects are more pronounced for PTCNSiOPr in comparison to those of PTCNSiOOc.…
Autor*innen: | Paulina Szymoniak, Mohamed A. Kolmangadi, Martin Böhning, B. Frick, M. Apple, R. A. Mole, N. R. De Souza, R. Zorn, Andreas Schönhals |
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Dokumenttyp: | Zeitschriftenartikel |
Veröffentlichungsform: | Verlagsliteratur |
Sprache: | Englisch |
Titel des übergeordneten Werkes (Englisch): | Macromolecules |
Jahr der Erstveröffentlichung: | 2024 |
Organisationseinheit der BAM: | 6 Materialchemie |
6 Materialchemie / 6.6 Physik und chemische Analytik der Polymere | |
7 Bauwerkssicherheit | |
7 Bauwerkssicherheit / 7.5 Technische Eigenschaften von Polymerwerkstoffen | |
Veröffentlichende Institution: | Bundesanstalt für Materialforschung und -prüfung (BAM) |
Verlag: | ACS Publications |
Erste Seite: | 1 |
Letzte Seite: | 14 |
DDC-Klassifikation: | Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten |
Freie Schlagwörter: | Polynorbornene; Quasielastic Neutron Scattering |
Themenfelder/Aktivitätsfelder der BAM: | Material |
Material / Nano | |
DOI: | 10.1021/acs.macromol.4c01045 |
URN: | urn:nbn:de:kobv:b43-608712 |
Verfügbarkeit des Dokuments: | Datei für die Öffentlichkeit verfügbar ("Open Access") |
Lizenz (Deutsch): | ![]() |
Datum der Freischaltung: | 26.08.2024 |
Referierte Publikation: | Ja |
Datum der Eintragung als referierte Publikation: | 02.09.2024 |
Schriftenreihen ohne Nummerierung: | Wissenschaftliche Artikel der BAM |