Effect of side-chain asymmetry on the intermolecular structure and order-disorder transition in alkyl-substituted polyfluorenes
- Knaapila, M.
- Stepanyan, R.
- Torkkeli, M.
- Haase, D.
- Fröhlich, N.
- Helfer, A.
- Forster, M.
- Scherf, U.
DOIAbstract
We study relations among the side-chain asymmetry, structure, and order-disorder transition (ODT) in hairy-rod-type poly(9,9-dihexylfluorene) (PF6) with two identical side chains and atactic poly(9-octyl-9-methyl-fluorene) (PF1-8) with two different side chains per repeat. PF6 and PF1-8 organize into alternating side-chain and backbone layers that transform into an isotropic phase at TODT(PF6) and TbiODT(PF1-8). We interpret polymers in terms of monodisperse and bidisperse brushes and predict scenarios TODT<TbiODT and TODT∼TbiODT for high and low grafting densities (the side-chain length above or below the average grafting distance). Calorimetry and x-ray scattering indicate the condition TODT(PF6)∼TbiODT(PF1-8) following the low grafting p...
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