Polythiophene-based conjugated polyelectrolyte: Optical properties and association behavior in solution

• Association behavior of the conjugated polyelectrolyte, slow relaxation processes.
• Solvatochromism and concentration dependence of optical properties.
• Translation of architecture between solid state and solution – mesoscale effects.
• Combination of spectroscopic, microscopic and light scattering methods.

Conjugated polyelectrolyte with polythiophene main chain and imidazolium side groups, poly{3-[6-(1-methylimidazolium-3-yl) hexyl]thiophene-2,5-diyl bromide}, is investigated. Polymer architecture with hydrophobic main chain and hydrophilic side groups is responsible for the inconvenient behavior of the polymer in solution. Absorption and emission characteristics and supramolecular assembling are investigated by spectroscopic, microscopic and light-scattering methods. We report significant solvatochromism which is observable by a naked eye. Water solutions and mixed solvent systems exhibit most interesting features: supramolecular assembling was investigated by DLS, AFM and TEM techniques and common spectroscopic methods such as UV–vis and fluorescence spectroscopy. Moreover, slow relaxation processes take part in water as it is evidenced by time evolution of absorption spectra. It is a result of vanishing of inter- and intramolecular interactions. These interactions are responsible for extraordinary solution behavior of the ionic polythiophene.

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