Journal article
Poly(9-undecyl-9-methyl-fluorene) and poly(9-pentadecyl-9-methyl-fluorene): Synthesis, solution structure, and effect of side chain asymmetry on aggregation behavior
Department of Physics, Technical University of Denmark1
Neutrons and X-rays for Materials Physics, Department of Physics, Technical University of Denmark2
University of Bradford3
Helmholtz-Zentrum Hereon4
Universidade de Coimbra5
Technical University of Denmark6
Bergische Universität Wuppertal7
We report on solution aggregates and backbone conformation of poly(9-undecyl-9-methyl-fluorene) (PF1-11) and poly(9-pentadecyl-9-methyl-fluorene) (PF1-15), having two different side chains compared with poly(9,9-dihexylfluorene) (PF6) and poly(9,9-dioctylfluorene) (PF8) with two identical side chains.
In the poor solvent methylcyclohexane (MCH), X-ray scattering indicates that PF1-11 and PF1-15 appear as three-dimensional aggregates (5-10 nm wide and thick), forming ribbon-like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two-dimensional aggregates (>10 nm wide and 2-3 nm thick) involving ribbon-like agglomerates (correlation lengths much greater than 100?nm).
Upon heating, all aggregates undergo a gel-sol transition which occurs at lower temperatures for PF1-11 and PF1-15 (80°C). In the good solvent toluene, PF1-11 and PF1-15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1-2 nm).
Nuclear magnetic resonance spectra in toluene-d8 together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1-11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1-15.
Language: | English |
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Year: | 2019 |
Pages: | 826-837 |
ISSN: | 10990488 and 08876266 |
Types: | Journal article |
DOI: | 10.1002/polb.24838 |
ORCIDs: | Knaapila, Matti , 0000-0003-1455-8462 , 0000-0001-9315-4188 , 0000-0001-9128-2557 , 0000-0002-8338-6441 , 0000-0003-3127-2298 and 0000-0001-8368-4919 |