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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
Tuning intermolecular interactions in dioctyl-substituted polyfluorene via hydrostatic pressure
K Paudel1, H Knoll, M Chandrasekhar
1Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA.
The Journal of Physical Chemistry. A
|March 19, 2010
Summary
We studied how hydrostatic pressure affects polyfluorenes (PFs), a type of blue-emitting polymer. Pressure influences polymer structure and light emission, revealing insights into their electronic properties and potential applications.
Area of Science:
- Materials Science
- Polymer Chemistry
- Condensed Matter Physics
Background:
- Polyfluorenes (PFs) are blue-emitting polymers with tunable properties based on side-chain functionalization.
- The backbone conformation and inter/intrachain structures significantly impact PF properties.
- Dioctyl-substituted PF (PF8) exhibits conformational variations dependent on monomer torsion angles.
Purpose of the Study:
- To investigate the effects of hydrostatic pressure on the photoluminescence (PL) and Raman scattering of dioctyl-substituted polyfluorene (PF8).
- To elucidate the role of backbone torsional angles in pressure-induced spectral shifts.
- To understand electron-phonon interactions in PFs under pressure.
Main Methods:
- Photoluminescence (PL) and Raman scattering spectroscopy were performed on bulk and thin-film samples of PF8 under hydrostatic pressure.
- Thermal annealing was applied to bulk samples before pressure-dependent studies.
- Density functional theoretical (DFT) calculations were conducted on fluorene oligomers to model pressure and torsion angle effects.
Main Results:
- Both as-is and annealed PF8 samples showed red shifts in PL energy with increasing pressure, but at different rates, indicating the influence of backbone torsion angles.
- Raman peaks shifted to higher frequencies (hardened) under pressure, with a specific C-C stretch mode showing a pressure coefficient of 7.2 cm(-1)/GPa.
- Asymmetric line shapes in Raman spectra at higher pressures suggested strong electron-phonon interactions.
Conclusions:
- Hydrostatic pressure significantly alters the optoelectronic properties of PF8 by affecting backbone conformation and interchain interactions.
- The distinct pressure coefficients of PL shifts highlight the critical role of torsional angles in dictating polymer behavior under pressure.
- Raman spectroscopy confirms pressure-induced structural changes and provides evidence for strong electron-phonon coupling in PFs.
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