This title appears in the Scientific Report : 2003 

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. / Seeck, O. / Pålsson, L.-O. / Serimaa, R. / Torkkeli, M. / Monkman, A. P.
Streumethoden; IFF-STM
The @journal of physical chemistry / B, 107 (2003) S. 12425 - 12430
Washington, DC Soc. 2003
12425 - 12430
Journal Article
Kondensierte Materie
Journal of Physical Chemistry B 107
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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.