Zhukov, S. ; Geppert, S. ; Stühn, B. ; Staneva, R. ; Ivanova, R. ; Gronski, W. (2002)
Dielectric relaxation in liquid crystalline/isotropic block copolymers: Effect of nanoscale confinement on the segmental dynamics.
In: Macromolecules, 35 (22)
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
We have synthesized a series of liquid crystalline/isotropic block copolymers with narrow molecular weight distribution and with well-defined chemical structure. Block volume fractions were varied systematically. The domain structure of these compounds was determined by means of small-angle X-ray scattering. Spherical, cylindrical, and lamellar morphologies were observed with the liquid crystalline (LC) block in the matrix or in the domain, respectively. The polymers are strongly segregated, and no order-to-disorder transition is found up to 170 degreesC. DSC and polarized microscopy data reveal that the mesomorphic behavior of LC blocks is only slightly influenced by copolymer composition and is basically characterized by the sequence g/similar to35 degreesC/n/similar to120 degreesCh. The rotational dynamics over a broad temperature and frequency range was studied using dielectric spectroscopy. The LC block reveals two cooperative modes assigned to the segmental relaxation (alpha process) and to the side chain rotation as a whole (delta process). A confinement effect is visible in the shift of both relaxation times to lower values for domain sizes less than 20 nm. The effect is stronger for 2D than for 1D confinement geometry. It is small compared to similar effects found for free-standing thin polymer films. For copolymers with alternate lamellae or LC cylindrical microdomains, a Maxwell-Wagner polarization was observed in addition to the alpha and delta processes.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2002 |
| Autor(en): | Zhukov, S. ; Geppert, S. ; Stühn, B. ; Staneva, R. ; Ivanova, R. ; Gronski, W. |
| Art des Eintrags: | Bibliographie |
| Titel: | Dielectric relaxation in liquid crystalline/isotropic block copolymers: Effect of nanoscale confinement on the segmental dynamics |
| Sprache: | Englisch |
| Publikationsjahr: | Oktober 2002 |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Macromolecules |
| Jahrgang/Volume einer Zeitschrift: | 35 |
| (Heft-)Nummer: | 22 |
| Kurzbeschreibung (Abstract): | We have synthesized a series of liquid crystalline/isotropic block copolymers with narrow molecular weight distribution and with well-defined chemical structure. Block volume fractions were varied systematically. The domain structure of these compounds was determined by means of small-angle X-ray scattering. Spherical, cylindrical, and lamellar morphologies were observed with the liquid crystalline (LC) block in the matrix or in the domain, respectively. The polymers are strongly segregated, and no order-to-disorder transition is found up to 170 degreesC. DSC and polarized microscopy data reveal that the mesomorphic behavior of LC blocks is only slightly influenced by copolymer composition and is basically characterized by the sequence g/similar to35 degreesC/n/similar to120 degreesCh. The rotational dynamics over a broad temperature and frequency range was studied using dielectric spectroscopy. The LC block reveals two cooperative modes assigned to the segmental relaxation (alpha process) and to the side chain rotation as a whole (delta process). A confinement effect is visible in the shift of both relaxation times to lower values for domain sizes less than 20 nm. The effect is stronger for 2D than for 1D confinement geometry. It is small compared to similar effects found for free-standing thin polymer films. For copolymers with alternate lamellae or LC cylindrical microdomains, a Maxwell-Wagner polarization was observed in addition to the alpha and delta processes. |
| Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik > Institut für Festkörperphysik (2021 umbenannt in Institut für Physik Kondensierter Materie (IPKM)) 05 Fachbereich Physik |
| Hinterlegungsdatum: | 27 Feb 2010 13:18 |
| Letzte Änderung: | 05 Mär 2013 09:32 |
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