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Charge density effects on the aggregation properties of poly(p-phenylene-ethynylene)-based anionic polyelectrolytes
Mingyan Wu1, Palwinder Kaur, Hongjun Yue
1Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
The Journal of Physical Chemistry. B
|March 1, 2008
Summary
Low charge density poly(p-phenylene-ethynylene)s aggregate in water, unlike their high charge density counterparts. Cationic surfactants can disrupt these aggregates, forming new supramolecular complexes.
Area of Science:
- Polymer Science
- Supramolecular Chemistry
- Materials Science
Background:
- Poly(p-phenylene-ethynylene)s (PPEs) are conjugated polymers with tunable properties.
- Charge density significantly influences the solution behavior of polyelectrolytes.
Purpose of the Study:
- To investigate the aggregation behavior of poly(p-phenylene-ethynylene)s with varying charge densities in aqueous solutions.
- To explore the effect of pH and surfactants on polymer aggregation and complex formation.
Main Methods:
- Steady-state spectroscopy to monitor spectral changes indicative of aggregation.
- pH variation to control charge density in weak polyelectrolytes.
- Fluorescence correlation spectroscopy (FCS) to determine aggregate size.
- Interaction studies with cationic surfactants.
Main Results:
- Low charge density PPEs (PPE-SO3Na-L, PPE-CO2Na-L) form aggregates in water, confirmed by spectral shifts compared to DMSO.
- High charge density PPEs (PPE-SO3Na-H, PPE-CO2Na-H) do not aggregate in water.
- Cationic surfactant octadecyltrimethyl ammonium dissociates low charge density aggregates.
- Surfactants form supramolecular complexes with both low and high charge density PPEs.
Conclusions:
- Polymer charge density is a critical factor governing aggregation in aqueous media.
- Surfactants can act as disaggregating agents and form novel supramolecular structures with polyelectrolytes.
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