### Abstract

The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH (MCH-d_{14}) solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.00058-4.29 ^{-}1) and optical spectroscopy. The number of side chain carbons (N) ranged from 6 to 10. The phase behavior was rationalized in terms of polymer overlap, cross-link density, and blending rules. For N=6-9, the system contains isotropic areas and lyotropic areas where sheetlike assemblies (lateral size of >400) and free polymer chains form ribbonlike agglomerates (characteristic dimension of >1500) leading to a gel-like appearance of the solutions. The ribbons are largely packed together with surface fractal characteristics for N=6-7 but become open networklike structures with mass fractal characteristics for N=8-9, until the system goes through a transition to an isotropic phase of overlapping rodlike polymers for N=10. The polymer order within sheets varies allowing classification for loose membranes and ordered sheets, including the so-called β phase. The polymers within the ordered sheets have restricted motion for N=6-7 but more freedom to vibrate for N=8-9. The nodes in the ribbon network are suggested to contain ordered sheets cross-linking the ribbons together, while the nodes in the isotropic phase appear as weak density fluctuations cross-linking individual chains together. The tendencies for macrophase separation and the formation of non beta sheets decrease while the proportion of free chains increases with increasing N. The fraction of β phase varies nonlinearly, reaching its maximum at N = 8.

Original language | English |
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Article number | 051803 |

Journal | Physical Review E - Statistical, Nonlinear, and Soft Matter Physics |

Volume | 83 |

Issue number | 5 |

DOIs | |

Publication status | Published - May 19 2011 |

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### ASJC Scopus subject areas

- Condensed Matter Physics
- Statistical and Nonlinear Physics
- Statistics and Probability

### Cite this

*Physical Review E - Statistical, Nonlinear, and Soft Matter Physics*,

*83*(5), [051803]. https://doi.org/10.1103/PhysRevE.83.051803

**Network structure of polyfluorene sheets as a function of alkyl side chain length.** / Knaapila, M.; Bright, D. W.; Stepanyan, R.; Torkkeli, M.; Almásy, L.; Schweins, R.; Vainio, U.; Preis, E.; Galbrecht, F.; Scherf, U.; Monkman, A. P.

Research output: Contribution to journal › Article

*Physical Review E - Statistical, Nonlinear, and Soft Matter Physics*, vol. 83, no. 5, 051803. https://doi.org/10.1103/PhysRevE.83.051803

}

TY - JOUR

T1 - Network structure of polyfluorene sheets as a function of alkyl side chain length

AU - Knaapila, M.

AU - Bright, D. W.

AU - Stepanyan, R.

AU - Torkkeli, M.

AU - Almásy, L.

AU - Schweins, R.

AU - Vainio, U.

AU - Preis, E.

AU - Galbrecht, F.

AU - Scherf, U.

AU - Monkman, A. P.

PY - 2011/5/19

Y1 - 2011/5/19

N2 - The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH (MCH-d14) solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.00058-4.29 -1) and optical spectroscopy. The number of side chain carbons (N) ranged from 6 to 10. The phase behavior was rationalized in terms of polymer overlap, cross-link density, and blending rules. For N=6-9, the system contains isotropic areas and lyotropic areas where sheetlike assemblies (lateral size of >400) and free polymer chains form ribbonlike agglomerates (characteristic dimension of >1500) leading to a gel-like appearance of the solutions. The ribbons are largely packed together with surface fractal characteristics for N=6-7 but become open networklike structures with mass fractal characteristics for N=8-9, until the system goes through a transition to an isotropic phase of overlapping rodlike polymers for N=10. The polymer order within sheets varies allowing classification for loose membranes and ordered sheets, including the so-called β phase. The polymers within the ordered sheets have restricted motion for N=6-7 but more freedom to vibrate for N=8-9. The nodes in the ribbon network are suggested to contain ordered sheets cross-linking the ribbons together, while the nodes in the isotropic phase appear as weak density fluctuations cross-linking individual chains together. The tendencies for macrophase separation and the formation of non beta sheets decrease while the proportion of free chains increases with increasing N. The fraction of β phase varies nonlinearly, reaching its maximum at N = 8.

AB - The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH (MCH-d14) solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.00058-4.29 -1) and optical spectroscopy. The number of side chain carbons (N) ranged from 6 to 10. The phase behavior was rationalized in terms of polymer overlap, cross-link density, and blending rules. For N=6-9, the system contains isotropic areas and lyotropic areas where sheetlike assemblies (lateral size of >400) and free polymer chains form ribbonlike agglomerates (characteristic dimension of >1500) leading to a gel-like appearance of the solutions. The ribbons are largely packed together with surface fractal characteristics for N=6-7 but become open networklike structures with mass fractal characteristics for N=8-9, until the system goes through a transition to an isotropic phase of overlapping rodlike polymers for N=10. The polymer order within sheets varies allowing classification for loose membranes and ordered sheets, including the so-called β phase. The polymers within the ordered sheets have restricted motion for N=6-7 but more freedom to vibrate for N=8-9. The nodes in the ribbon network are suggested to contain ordered sheets cross-linking the ribbons together, while the nodes in the isotropic phase appear as weak density fluctuations cross-linking individual chains together. The tendencies for macrophase separation and the formation of non beta sheets decrease while the proportion of free chains increases with increasing N. The fraction of β phase varies nonlinearly, reaching its maximum at N = 8.

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U2 - 10.1103/PhysRevE.83.051803

DO - 10.1103/PhysRevE.83.051803

M3 - Article

VL - 83

JO - Physical review. E

JF - Physical review. E

SN - 2470-0045

IS - 5

M1 - 051803

ER -