Conjugated Polyelectrolytes (CPEs) play an important role in modern optoelectronics as they combine polar nature of their ionic side groups with the electronical properties from the conjugated polymer backbone. Therefore several applications in optoelectronic devices (e. g. in photovoltaics as charge extraction layers) have been reported and can vary due to their composition of backbone and ionic functionality.
In this thesis, the syntheses of novel conjugated polyelectrolytes (CPEs) are presented. Via post-polymerization modifications of neutral precursor polymers cationic, anionic and zwitterionic (with both, positive and negative charge, in one repeating unit) polyelectrolytes are easily accessible. Beside syntheses of polymers with different side groups the focus of this thesis is on the variation of the π-conjugated backbone.
At first, the synthesis of thiophene-based polyelectrolytes is described. So-called polymerized ionic liquids (PILs) with variable length of the alkyl-spacer between thiophene backbone and imidazolium side groups are presented. Additionally zwitterionic polythiophenes with a variety of different spacer lengths between positive and negative charge are introduced. This variation allows tuning of the dipole moment of the zwitterionic functionalities. Another variation of the effective dipole moment of the polyelectrolytes is achieved by reducing the content of charged side groups in either statistical or alternating thiophene-based CPEs.
Secondly, a new approach for the synthesis of electron-deficient benzotriazole-based polyelectrolytes is presented. In contrast to literature known polycondensation of ionic monomers, in this thesis post-polymerization modification of neutral polybenzotriazoles with solubilizing, branched alkyl-chains is described.
Finally, a series of novel donor-acceptor-polyelectrolytes is introduced. In this chapter, the focus is on the systematic modification of the π-conjugated backbone. By smart combination of the donor and acceptor building blocks a great tunability of the optical properties of the resulting copolymers can be achieved. Also the role of additional electron-rich thiophene units is discussed including the aspect of different donor-strength of the corresponding donor building blocks (CPDT, carbazole, fluorene).