10 November 2004 Multiple orientation and nematic-hexagonal transition in uniaxially aligned polyfluorene thin films
Author Affiliations +
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.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Matti Knaapila, Matti Knaapila, Benjamin P. Lyons, Benjamin P. Lyons, Kaisa Kisko, Kaisa Kisko, Oliver H. Seeck, Oliver H. Seeck, Joel P. Foreman, Joel P. Foreman, Ulla Vainio, Ulla Vainio, Ritva Serimaa, Ritva Serimaa, Mika Torkkeli, Mika Torkkeli, Andrew P. Monkman, Andrew P. Monkman, "Multiple orientation and nematic-hexagonal transition in uniaxially aligned polyfluorene thin films", Proc. SPIE 5519, Organic Light-Emitting Materials and Devices VIII, (10 November 2004); doi: 10.1117/12.555823; https://doi.org/10.1117/12.555823
PROCEEDINGS
9 PAGES


SHARE
Back to Top