This project focuses on cationic isothiouronium polythiophenes (CITs), a particular type of conjugated polyelectrolytes (CPEs). In general, CPEs combine a pi-conjugated polymer backbone with pendant ionic groups, which gives them chromo- and fluoro-phoric properties, and also water-solubility. This structure provides CPEs with interacting driving forces of conjugated polymers (pi-pi stacking and hydrophobic interactions) and of polyelectrolytes, such as coordination through electrostatic forces and hydrogen bonding (H-bonding). Polythiophene-CPEs in particular, have a high sensitivity to different stimuli, such as solvent (solvatochromism) or other chemical species (affinity chromism), which can be traced by fluorescence. Besides these properties, the isothiouronium cationic functionality in the CITs under study, gives them enhanced hydrogen-bonding (H-bonding) donor capabilities.

The properties in the CITs were utilized for studying how structure influences on functions such as (i) electronic properties (ionization potential, electron affinity, optical transitions and (ii) polymer-solvent, polymer-polymer and polymer-quencher interactions. The optical properties of the CITs were traced by steady-state absorption-fluorescence spectroscopic techniques in order to track molecular changes, while their aggregation was studied by electron paramagnetic resonance (EPR) spectroscopy, using paramagnetic probes with different ionic and hydrophobic constituents. Cyclic voltammetry, density functional theory (DFT) and molecular mechanics (MM) were also used as complementary tools.

These results could be useful to the broad field of supramolecular chemistry of CPEs, some of which complex phenomena is still not completely understood at a mechanistic level. This in turn could benefit fields such as actuators and sensors and organic optoelectronics, research areas which are currently finding applications to several CPEs.