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Molecular dynamics of the asymmetric blend PVME/PS revisited by broadband dielectric and specific heat spectroscopy: Evidence of multiple glassy dynamics

  • The molecular mobility of the highly asymmetric miscible blend poly(vinyl methyl ether)/polystyrene was investigated by broadband dielectric (frequency range 10^-1 Hz – 10^9 Hz) and specific heat spectroscopy (frequency range 10^1 Hz – 10^4 Hz). The dielectric spectra revealed a complex molecular dynamic behavior, where three different relaxation processes were observed. At temperatures below the glass transition temperature an α´-relaxation was found, with an Arrhenius-like temperature dependence of its relaxation rates. It is assigned to localized fluctuations of the confined PVME segments within a frozen glassy matrix dominated by PS. Above the thermal glass transition temperature two processes with a VFT behavior of their relaxation rates were detected called α1- and α2-relaxation, both originating from PVME dipoles fluctuating in PS-rich environments, however with diverse PS concentrations. The relevant length scales for the processes are assumed to be different,The molecular mobility of the highly asymmetric miscible blend poly(vinyl methyl ether)/polystyrene was investigated by broadband dielectric (frequency range 10^-1 Hz – 10^9 Hz) and specific heat spectroscopy (frequency range 10^1 Hz – 10^4 Hz). The dielectric spectra revealed a complex molecular dynamic behavior, where three different relaxation processes were observed. At temperatures below the glass transition temperature an α´-relaxation was found, with an Arrhenius-like temperature dependence of its relaxation rates. It is assigned to localized fluctuations of the confined PVME segments within a frozen glassy matrix dominated by PS. Above the thermal glass transition temperature two processes with a VFT behavior of their relaxation rates were detected called α1- and α2-relaxation, both originating from PVME dipoles fluctuating in PS-rich environments, however with diverse PS concentrations. The relevant length scales for the processes are assumed to be different, corresponding to the Kuhn segment length for the former relaxation and to the CRR for the latter one. The observed multiple glassy dynamics result from spatial local compositional heterogeneities on a microscopic level. Additionally, SHS investigations were performed for the first time for this system, proving an existence of a fourth relaxation process (α3-relaxation) due to the cooperative fluctuations of both PS and PVME segments. The separation between the thermal α3- and dielectric α2-relaxation increases dramatically with increasing polystyrene concentration, proving that the thermal response is dominated by PS.zeige mehrzeige weniger

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  • Macromolecules 52 _2019_1620-1631.pdf
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Metadaten
Autoren/innen:Paulina Szymoniak, Sherif Madkour, Andreas Schönhals
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Macromolecules
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:6 Materialschutz und Oberflächentechnik
6 Materialschutz und Oberflächentechnik / 6.6 Nano-Tribologie und Nanostrukturierung von Oberflächen
Verlag:ACS Publications
Jahrgang/Band:52
Ausgabe/Heft:4
Erste Seite:1620
Letzte Seite:1631
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Broadband dielectric spectroscopy; Dynamic heterogeneity; Polymer blends; Specific heat spectroscopy
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Materialien und Stoffe
Material / Nanoskalige Materialien und deren Eigenschaften
DOI:https://doi.org/10.1021/acs.macromol.8b02697
URL:http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS_CPL&DestLinkType=FullRecord&UT=WOS:000460199600025
ISSN:0024-9297
Verfügbarkeit des Volltexts:Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:11.03.2019
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:15.03.2019