X-ray Diffraction Studies of Multiple Orientation in Poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl) Thin Films

Knaapila, M.; Foreman, J. P.; Lyons, B. P.; Monkman, A. P.; Torkkeli, M.; Pålsson, L.-O.; Kisko, K.; Vainio, U.; Serimaa, R.; Mihaylova, M.; Seeck, O.

doi:10.1021/jp035259t

Journal Article

X-ray Diffraction Studies of Multiple Orientation in Poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl) Thin Films

Knaapila, M. ; Lyons, B. P. ; Kisko, K. ; Foreman, J. P. ; Vainio, U. ; Mihaylova, M.FZJ* ; Seeck, O.FZJ* ; Pålsson, L.-O. ; Serimaa, R. ; Torkkeli, M. ; Monkman, A. P.

2003
Soc. Washington, DC

The journal of physical chemistry <Washington, DC> / B 107, 12425 - 12430 (2003) [10.1021/jp035259t]

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Please use a persistent id in citations: http://hdl.handle.net/2128/1322 doi:10.1021/jp035259t

Abstract: The structural investigation of poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl) (PF2/6) in aligned thin films is presented. Formation of a thickness dependent triaxial texturing is identified in thermotropically aligned films. X-ray reflectivity measurements reveal good macroscopic quality, and polarized photoluminescence and dichroic ratios in absorption indicate clear axial alignment. Grazing-incidence X-ray diffraction shows axially aligned mesomorphic structure with a distinct arrangement of helices and large correlation lengths, indicating a high local lateral order. Theoretical models produced using molecular mechanics methods suggest 5/2-helicity. The polymer chains are parallel to the substrate in the c direction. In particular, the hexagonal-like cells are flattened in the direction of the surface normal and reveal two kinds of coexistent crystallites, a multiple orientation where the greater proportion of the crystallites have one crystal axis a perpendicular to the substrate surface, whereas a smaller proportion is aligned with the crystal axis a parallel to the surface. In thinner films the former class of orientation is usually dominant, while the proportion of the parallel orientation type increases with prolonged annealing.

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