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Proceedings Paper

Multiple orientation and nematic-hexagonal transition in uniaxially aligned polyfluorene thin films
Author(s): Matti Knaapila; Benjamin P. Lyons; Kaisa Kisko; Oliver H. Seeck; Joel P. Foreman; Ulla Vainio; Ritva Serimaa; Mika Torkkeli; Andrew P. Monkman
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Paper Abstract

We present a structural study of poly(9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl) (PF2/6) in aligned thin films on a rubbed polyimide substrate. PF2/6 forms 5/2-helical hairy-rodlike molecular structure which is self-organized in the hexagonal structure. In thin films, the aligned rigid polymer chains are parallel to the substrate in the direction corresponding to the molecular backbone, c axis. The cells are flattened in the direction of the surface normal and -in particular- reveal a multiple orientation where the greater proportion of the crystallites have one crystal axis a perpendicular to the substrate surface but a small proportion are aligned with the crystal axis a parallel to surface. We find further that by reducing the polymer chain length to approximately twenty repeat units the degree of axial alignment of PF2/6 is considerably improved while the local order changes from hexagonal packing towards nematic phase with no sign of multiple orientation.

Paper Details

Date Published: 10 November 2004
PDF: 9 pages
Proc. SPIE 5519, Organic Light-Emitting Materials and Devices VIII, (10 November 2004); doi: 10.1117/12.555823
Show Author Affiliations
Matti Knaapila, Univ. of Durham (United Kingdom)
Benjamin P. Lyons, Univ. of Durham (United Kingdom)
Kaisa Kisko, Univ. of Helsinki (Finland)
Oliver H. Seeck, Forschungszentrum Juelich GmbH (Germany)
Joel P. Foreman, Univ. of Durham (United Kingdom)
Ulla Vainio, Univ. of Helsinki (Finland)
Ritva Serimaa, Univ. of Helsinki (Finland)
Mika Torkkeli, Univ. of Helsinki (Finland)
Andrew P. Monkman, Univ. of Durham (United Kingdom)

Published in SPIE Proceedings Vol. 5519:
Organic Light-Emitting Materials and Devices VIII
Zakya H. Kafafi; Paul A. Lane, Editor(s)

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