Premium
Influence of Molecular Weight on the Surface Morphology of Aligned, Branched Side‐Chain Polyfluorene
Author(s) -
Knaapila M.,
Lyons B. P.,
Hase T. P. A.,
Pearson C.,
Petty M. C.,
Bouchenoire L.,
Thompson P.,
Serimaa R.,
Torkkeli M.,
Monkman A. P.
Publication year - 2005
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200500061
Subject(s) - materials science , crystallite , polyfluorene , morphology (biology) , texture (cosmology) , phase (matter) , atomic force microscopy , crystallography , surface finish , phase transition , diffraction , polymer , optics , nanotechnology , composite material , condensed matter physics , organic chemistry , chemistry , copolymer , physics , biology , genetics , image (mathematics) , artificial intelligence , computer science , metallurgy
Abstract The surface structure of uniaxially aligned poly(9,9‐bis(ethylhexyl)‐fluorene‐2,7‐diyl) films on rubbed polyimide has been studied as a function of molecular weight ( M n = 3–150 kg mol –1 , number‐average molecular weight) using polarized microscopy, atomic force microscopy (AFM), X‐ray reflectivity, and grazing‐incidence X‐ray diffraction. At the threshold M n , M n * = 10 4 g mol –1 , there is a prominent transition in morphology from featureless ( M n < M n *) to rough ( M n > M n *), corresponding to the nematic–hexagonal phase transition. The hexagonal phase reveals two coexistent crystallite types in the whole film and at least one crystallite type has been observed at the surface by AFM. The combined optimization of alignment and surface smoothness is achieved slightly below M n * while the combined optimization of orientational and local order and moderately smooth surface is achieved slightly above M n *.