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- Knaapila, Matti, et al.
(författare)
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An effect of side chain length on the solution structure of poly(9,9-dialkylfluorene)s in toluene
- 2008
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 49:8, s. 2033-2038
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Tidskriftsartikel (refereegranskat)abstract
- The effect of side chain length of pi-conjugated poly(9,9-dialkylfluorene)s has been studied in semi-dilute (10 mg/mL) toluene solutions using small-angle neutron scattering (SANS) and H-1 and H-2 NMR spectroscopies. Under these conditions, SANS data indicate that poly(9,9-dinonylfluorene) and poly(9,9-dioctylfluorene) are dissolved down to the molecule level and appear as elongated one-dimensional chains (length >20-30 nm). In contrast, the shorter side chain polymers exhibit a self-association so that poly(9,9-diheptylfluorene) forms thin sheet-like (similar to 1 nm) and poly(9,9-dihexylfluorene) thin (similar to 1 nm) and thick sheet-like (>6 nm) aggregates. H-1 NMR data, together with the density functional theory (DFT) calculations, however, show that this occurs without changes in the conformation of the polymer backbone.
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- Knaapila, Matti, et al.
(författare)
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Influence of side chain length on the self-assembly of hairy-rod poly(9,9-dialkylfluorene)s in the poor solvent methylcyclohexane
- 2007
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 40:26, s. 9398-9405
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Tidskriftsartikel (refereegranskat)abstract
- We report on the phase behavior of poly(9,9-dihexylfluorene) (PF6), poly(9,9-diheptylfluorene) (PF7), poly(9,9-diocylfluorene) (PF8) poly(9,9-dinonylfluorene) (PF9), and poly(9,9-didecylfluorene) (PF10) in methylcyclohexane (MCH). After a heating-cooling cycle, in the 10-50 mg/mL. concentration range. PF6/ MCH. PF7/MCH. PF8/MCH, and PF9/MCH systems were found to be gel-like, while PF10/MCH appears less viscous. PF6/MCH, PF7/MCH, PF8/MCH, and PF9/MCH form large (10- 100 nm) sheetlike assemblies (thickness of 2-3 nm). The larger length scale Structures of these sheets show an odd-even dependence on the side chain (spacer) length: the PF6 and PF8 sheets are broader and thinner, whereas PF7 and PF9 sheets are thicker with a Putative double layer Structure. PF10 does not follow this sequence, and only part of the polymer is assembled into a sheetlike structure the rest remaining dissolved at the molecular level. PF8/MCH and PF9/MCH mixtures also have lower length scale crystalline structures with an internal period corresponding to the periodicity observed in the solid-state P phase of PF8. Vestiges of crystalline domains are found for PF6 and PF7 but not for PF10. PF7/MCH. PF8/MCH, and PF9/MCH systems contain the conformational isomer C, of those chains observed in the ss phase, while this is not observed with other polymer/MCH systems.
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