Evidence for structural transition in hairy-rod poly[9,9-bis(2-ethylhexyl)fluorene] under high pressure conditions
Author
Summary, in English
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.
Department/s
Publishing year
2010
Language
English
Publication/Series
Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)
Volume
82
Issue
5
Document type
Journal article
Publisher
American Physical Society
Topic
- Natural Sciences
- Physical Sciences
Status
Published
ISBN/ISSN/Other
- ISSN: 1539-3755