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Synthesis and Processing of Monodisperse Oligo(fluorene‐ co ‐bithiophene)s into Oriented Films by Thermal and Solvent Annealing
Author(s) -
Zeng Lichang,
Yan Feng,
Wei Simon K.H.,
Culligan Sean W.,
Chen Shaw H.
Publication year - 2009
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.200900101
Subject(s) - materials science , annealing (glass) , solvent , chlorobenzene , oligomer , dispersity , chemical engineering , fluorene , polymer , polymer chemistry , organic chemistry , composite material , chemistry , engineering , catalysis
A series of oligo(fluorene‐ co ‐bithiophene)s, OF2Ts , have been synthesized and characterized to investigate the effects of oligomer length and pendant aliphatic structure on glassy‐nematic mesomorphism. The OF2Ts comprising more than one repeat unit and their polymer analogue, PF2T , carrying 52 number‐average repeat units, possess the highest occupied molecular orbital energy level at −5.3 ± 0.2 eV, but the anisotropic field‐effect mobilities increase with the oligomer length. Spin coating from high‐boiling chlorobenzene with and without subsequent exposure to saturated chlorobenzene vapor constitute solvent‐vapor annealing and quasi‐solvent annealing, respectively. Solvent‐vapor annealing yields monodomain glassy‐nematic films in which OF2Ts are aligned as well as with thermal annealing across a 2 cm diameter. Quasi‐solvent annealing, however, amounts to kinetically trapping a lower orientational order than solvent‐vapor or thermal annealing. While amenable to thermal annealing at elevated temperatures, PF2T shows no alignment at all following either strategy of solvent annealing.