Advanced

Structural study of helical polyfluorene under high quasihydrostatic pressure

Knaapila, M.; Konopkova, Z.; Torkkeli, M.; Haase, Dörthe LU ; Liermann, H. -P.; Guha, S. and Scherf, U. (2013) In Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)2001-01-01+01:002016-01-01+01:00 87(2).
Abstract
We report on an x-ray diffraction (XRD) study of helical poly[9,9-bis(2-ethylhexyl)fluorene] (PF2/6) under high quasihydrostatic pressure and show an effect of pressure on the torsion angle (dihedral angle) between adjunct repeat units and on the hexagonal unit cell. A model for helical backbone conformation is constructed. The theoretical position for the most prominent 00l x-ray reflection is calculated as a function of torsion angle. The XRD of high molecular weight PF2/6 (M-n = 30 kg/mol) is measured through a diamond anvil cell upon pressure increase from 1 to 10 GPa. The theoretically considered 00l reflection is experimentally identified, and its shift with the increasing pressure is found to be consistent with the decreasing... (More)
We report on an x-ray diffraction (XRD) study of helical poly[9,9-bis(2-ethylhexyl)fluorene] (PF2/6) under high quasihydrostatic pressure and show an effect of pressure on the torsion angle (dihedral angle) between adjunct repeat units and on the hexagonal unit cell. A model for helical backbone conformation is constructed. The theoretical position for the most prominent 00l x-ray reflection is calculated as a function of torsion angle. The XRD of high molecular weight PF2/6 (M-n = 30 kg/mol) is measured through a diamond anvil cell upon pressure increase from 1 to 10 GPa. The theoretically considered 00l reflection is experimentally identified, and its shift with the increasing pressure is found to be consistent with the decreasing torsion angle between 2 and 6 GPa. This indicates partial backbone planarization towards a more open helical structure. The h00 peak is identified, and its shift together with the broadening of 00l implies impairment of the ambient hexagonal order, which begins at or below 2 GPa. Previously collected high-pressure photoluminescence data are reanalyzed and are found to be qualitatively consistent with the XRD data. This paper provides an example of how the helical pi-conjugated backbone structure can be controlled by applying high quasihydrostatic pressure without modifications in its chemical structure. Moreover, it paves the way for wider use of high-pressure x-ray scattering in the research of pi-conjugated polymers. DOI: 10.1103/PhysRevE.87.022602 (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)2001-01-01+01:002016-01-01+01:00
volume
87
issue
2
publisher
American Physical Society
external identifiers
  • wos:000315150500010
  • scopus:84874535256
ISSN
1539-3755
DOI
10.1103/PhysRevE.87.022602
language
English
LU publication?
yes
id
bda2c45d-70da-4dba-a93a-7e16ea83f7ec (old id 3577867)
date added to LUP
2013-03-20 13:47:24
date last changed
2019-03-19 01:07:53
@article{bda2c45d-70da-4dba-a93a-7e16ea83f7ec,
  abstract     = {We report on an x-ray diffraction (XRD) study of helical poly[9,9-bis(2-ethylhexyl)fluorene] (PF2/6) under high quasihydrostatic pressure and show an effect of pressure on the torsion angle (dihedral angle) between adjunct repeat units and on the hexagonal unit cell. A model for helical backbone conformation is constructed. The theoretical position for the most prominent 00l x-ray reflection is calculated as a function of torsion angle. The XRD of high molecular weight PF2/6 (M-n = 30 kg/mol) is measured through a diamond anvil cell upon pressure increase from 1 to 10 GPa. The theoretically considered 00l reflection is experimentally identified, and its shift with the increasing pressure is found to be consistent with the decreasing torsion angle between 2 and 6 GPa. This indicates partial backbone planarization towards a more open helical structure. The h00 peak is identified, and its shift together with the broadening of 00l implies impairment of the ambient hexagonal order, which begins at or below 2 GPa. Previously collected high-pressure photoluminescence data are reanalyzed and are found to be qualitatively consistent with the XRD data. This paper provides an example of how the helical pi-conjugated backbone structure can be controlled by applying high quasihydrostatic pressure without modifications in its chemical structure. Moreover, it paves the way for wider use of high-pressure x-ray scattering in the research of pi-conjugated polymers. DOI: 10.1103/PhysRevE.87.022602},
  articleno    = {022602},
  author       = {Knaapila, M. and Konopkova, Z. and Torkkeli, M. and Haase, Dörthe and Liermann, H. -P. and Guha, S. and Scherf, U.},
  issn         = {1539-3755},
  language     = {eng},
  number       = {2},
  publisher    = {American Physical Society},
  series       = {Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)2001-01-01+01:002016-01-01+01:00},
  title        = {Structural study of helical polyfluorene under high quasihydrostatic pressure},
  url          = {http://dx.doi.org/10.1103/PhysRevE.87.022602},
  volume       = {87},
  year         = {2013},
}