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Evidence for structural transition in hairy-rod poly[9,9-bis(2-ethylhexyl)fluorene] under high pressure conditions

Knaapila, Matti LU ; Stepanyan, R; Haase, Dörthe LU ; Carlson, Stefan LU ; Torkkeli, M; Cerenius, Y LU ; Scherf, U and Guha, S (2010) In Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)2001-01-01+01:002016-01-01+01:00 82(5).
Abstract
We report on an x-ray scattering experiment of bulk poly[9,9-bis(2-ethylhexyl)fluorene] under quasihydrostatic pressure from 1 to 11 GPa at room temperature. The scattering pattern of high molecular weight (HMW) polyfluorene (>10 kg/mol) undergoes significant changes between 2 and 4 GPa in the bulk phase. The 110 reflection of the hexagonal unit cell disappears, indicating a change in equatorial intermolecular order. The intensity of the 00 21 reflection drops, with a sudden move toward higher scattering angles. Beyond these pressures, the diminished 00 21 reflection tends to return toward lower angles. These changes may be interpreted as a transition from crystalline hexagonal to glassy nematic phase (perceiving order only in one... (More)
We report on an x-ray scattering experiment of bulk poly[9,9-bis(2-ethylhexyl)fluorene] under quasihydrostatic pressure from 1 to 11 GPa at room temperature. The scattering pattern of high molecular weight (HMW) polyfluorene (>10 kg/mol) undergoes significant changes between 2 and 4 GPa in the bulk phase. The 110 reflection of the hexagonal unit cell disappears, indicating a change in equatorial intermolecular order. The intensity of the 00 21 reflection drops, with a sudden move toward higher scattering angles. Beyond these pressures, the diminished 00 21 reflection tends to return toward lower angles. These changes may be interpreted as a transition from crystalline hexagonal to glassy nematic phase (perceiving order only in one direction). This transition may be rationalized by density arguments and the underlying theory of phase behavior of hairy-rod polyfluorene. Also the possible alteration of the 21-helical main chain toward more planar main chain conformation is discussed. The scattering of low molecular weight polyfluorene (<10 kg/mol), which is glassy nematic in ambient pressure, is reminiscent with that of HMW polymer above 2–4 GPa. (Less)
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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
82
issue
5
publisher
American Physical Society
external identifiers
  • wos:000284466700004
  • scopus:78651358099
ISSN
1539-3755
DOI
10.1103/PhysRevE.82.051803
language
English
LU publication?
yes
id
e19ea424-a8e5-49a9-a4cf-6a79f043cdea (old id 1737317)
date added to LUP
2010-12-09 07:57:01
date last changed
2018-08-24 08:49:47
@article{e19ea424-a8e5-49a9-a4cf-6a79f043cdea,
  abstract     = {We report on an x-ray scattering experiment of bulk poly[9,9-bis(2-ethylhexyl)fluorene] under quasihydrostatic pressure from 1 to 11 GPa at room temperature. The scattering pattern of high molecular weight (HMW) polyfluorene (&gt;10 kg/mol) undergoes significant changes between 2 and 4 GPa in the bulk phase. The 110 reflection of the hexagonal unit cell disappears, indicating a change in equatorial intermolecular order. The intensity of the 00 21 reflection drops, with a sudden move toward higher scattering angles. Beyond these pressures, the diminished 00 21 reflection tends to return toward lower angles. These changes may be interpreted as a transition from crystalline hexagonal to glassy nematic phase (perceiving order only in one direction). This transition may be rationalized by density arguments and the underlying theory of phase behavior of hairy-rod polyfluorene. Also the possible alteration of the 21-helical main chain toward more planar main chain conformation is discussed. The scattering of low molecular weight polyfluorene (&lt;10 kg/mol), which is glassy nematic in ambient pressure, is reminiscent with that of HMW polymer above 2–4 GPa.},
  articleno    = {051803},
  author       = {Knaapila, Matti and Stepanyan, R and Haase, Dörthe and Carlson, Stefan and Torkkeli, M and Cerenius, Y and Scherf, U and Guha, S},
  issn         = {1539-3755},
  language     = {eng},
  number       = {5},
  publisher    = {American Physical Society},
  series       = {Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)2001-01-01+01:002016-01-01+01:00},
  title        = {Evidence for structural transition in hairy-rod poly[9,9-bis(2-ethylhexyl)fluorene] under high pressure conditions},
  url          = {http://dx.doi.org/10.1103/PhysRevE.82.051803},
  volume       = {82},
  year         = {2010},
}