Control over phase behavior and solution structure of hairy-rod polyfluorene by means of side-chain length and branching
(2008) In Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 77(5).- Abstract
- We present guidelines on how the solution structure of pi-conjugated hairy-rod polyfluorenes is controlled by the side-chain length and branching. First, the semiquantitative mean-field theory is formulated to predict the phase behavior of the system as a function of side-chain beads (N). The phase transition at N=N* separates a lyotropic phase with solvent coexistence (N < N*) and a metastable membrane phase (N > N*). The membrane phase transforms into the isotropic phase of dissolved rodlike polymers at the temperature T-mem*(N), which decreases both with N and with the degree of side-chain branching. This picture is complemented by polymer demixing with the transition temperature T-IN*(N), which decreases with N. For N < N*,... (More)
- We present guidelines on how the solution structure of pi-conjugated hairy-rod polyfluorenes is controlled by the side-chain length and branching. First, the semiquantitative mean-field theory is formulated to predict the phase behavior of the system as a function of side-chain beads (N). The phase transition at N=N* separates a lyotropic phase with solvent coexistence (N < N*) and a metastable membrane phase (N > N*). The membrane phase transforms into the isotropic phase of dissolved rodlike polymers at the temperature T-mem*(N), which decreases both with N and with the degree of side-chain branching. This picture is complemented by polymer demixing with the transition temperature T-IN*(N), which decreases with N. For N < N*, the lyotropic phase turns isotropic with increasing T at T-IN*. For N > N*, stable membranes are predicted for T-IN*< T < T-mem* and metastable membranes with nematic coexistence for T < T-IN*. Second, in experiment, samples of poly(9,9-dialkylfluorene) with N=6-10 were mixed in methylcyclohexane. For N=8 the side-chain branching was controlled by (9,9-dioctylfluorene)/(9,9-bis(2-ethylhexyl)fluorene) (F8/F2/6) random copolymers. The proportion of F8 to F2/6 repeat units was 100:0, 95:5, 90:10, 50:50, and 0:100. In accordance with the theory, lyotropic, membrane, and isotropic phases with the corresponding phase transitions were observed. For N < N*similar to 6 only the lyotropic phase is present for attainable temperatures. The membrane and isotropic phases are present for N > N*. T-mem*(N) decreases from 340 K to 280 K for N >= 8. For copolymers, the membrane phase is found when the fraction of F8 units is at least 90%, T-mem* decreasing with this fraction. The membrane phase contains three material types: loose sheets of two polymer layers, a better packed beta phase, and dissolved polymer. For N >= 7 and T < T-mem* the tendency for membrane formation becomes stronger with increasing temperature. (Less)
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https://lup.lub.lu.se/record/1190532
- author
- Knaapila, Matti LU ; Stepanyan, R. ; Torkkeli, M. ; Garamus, V. M. ; Galbrecht, F. ; Nehls, B. S. ; Preis, E. ; Scherf, U. and Monkman, A. R.
- organization
- publishing date
- 2008
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)
- volume
- 77
- issue
- 5
- article number
- 051803
- publisher
- American Physical Society
- external identifiers
-
- wos:000256885400085
- scopus:43449089204
- pmid:18643093
- ISSN
- 1539-3755
- DOI
- 10.1103/PhysRevE.77.051803
- language
- English
- LU publication?
- yes
- id
- dddfd6c2-562e-4228-a2a0-b19e8de76f28 (old id 1190532)
- date added to LUP
- 2016-04-01 12:13:37
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- 2022-03-28 22:02:18
@article{dddfd6c2-562e-4228-a2a0-b19e8de76f28,
abstract = {{We present guidelines on how the solution structure of pi-conjugated hairy-rod polyfluorenes is controlled by the side-chain length and branching. First, the semiquantitative mean-field theory is formulated to predict the phase behavior of the system as a function of side-chain beads (N). The phase transition at N=N* separates a lyotropic phase with solvent coexistence (N < N*) and a metastable membrane phase (N > N*). The membrane phase transforms into the isotropic phase of dissolved rodlike polymers at the temperature T-mem*(N), which decreases both with N and with the degree of side-chain branching. This picture is complemented by polymer demixing with the transition temperature T-IN*(N), which decreases with N. For N < N*, the lyotropic phase turns isotropic with increasing T at T-IN*. For N > N*, stable membranes are predicted for T-IN*< T < T-mem* and metastable membranes with nematic coexistence for T < T-IN*. Second, in experiment, samples of poly(9,9-dialkylfluorene) with N=6-10 were mixed in methylcyclohexane. For N=8 the side-chain branching was controlled by (9,9-dioctylfluorene)/(9,9-bis(2-ethylhexyl)fluorene) (F8/F2/6) random copolymers. The proportion of F8 to F2/6 repeat units was 100:0, 95:5, 90:10, 50:50, and 0:100. In accordance with the theory, lyotropic, membrane, and isotropic phases with the corresponding phase transitions were observed. For N < N*similar to 6 only the lyotropic phase is present for attainable temperatures. The membrane and isotropic phases are present for N > N*. T-mem*(N) decreases from 340 K to 280 K for N >= 8. For copolymers, the membrane phase is found when the fraction of F8 units is at least 90%, T-mem* decreasing with this fraction. The membrane phase contains three material types: loose sheets of two polymer layers, a better packed beta phase, and dissolved polymer. For N >= 7 and T < T-mem* the tendency for membrane formation becomes stronger with increasing temperature.}},
author = {{Knaapila, Matti and Stepanyan, R. and Torkkeli, M. and Garamus, V. M. and Galbrecht, F. and Nehls, B. S. and Preis, E. and Scherf, U. and Monkman, A. R.}},
issn = {{1539-3755}},
language = {{eng}},
number = {{5}},
publisher = {{American Physical Society}},
series = {{Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)}},
title = {{Control over phase behavior and solution structure of hairy-rod polyfluorene by means of side-chain length and branching}},
url = {{http://dx.doi.org/10.1103/PhysRevE.77.051803}},
doi = {{10.1103/PhysRevE.77.051803}},
volume = {{77}},
year = {{2008}},
}