Development of Water-soluble semiconducting polar polymers for smart applications

The development of new materials is pivotal for the exploitation of the new technologies. One important class of emerging semiconducting materials is represented by conjugated polyelectrolytes (CPEs)1 comprising an electronically delocalized ?-conjugated backbone with pendant groups bearing polar or ionic functionalities. CPEs are generally composed of (i) ?-conjugated backbones, which determine the main optical properties, such as absorption and emission spectra, light-harvesting ability, and quantum yield, and (ii) charged/polar side-chains, such as cationic quaternary ammonium groups, anionic carboxyl groups, sulfonic groups, and phosphate groups and polar amine or phosphonate groups which impart solubility in water and alcohols. CPEs combine the typical properties of polymeric semiconductors, such as chemical tunability, easy processability, lightness and flexibility with the growing demand for environmentally friendly materials and processes. As the materials obtained are used in electronics, optoelectronics and in bioelectronics they must also have both controlled molecular weight and high purity suitable. Therefore, one of the main issue to be addressed is to adapt the polymerization and purification conditions, traditionally carried out under dry conditions and non-aqueous solvents to polar polymers. Moreover, interfacial engineering has been identified recently as an essential approach for maximizing efficiency and stability of electronic and optoelectronic devices. In this contest, the intrinsic hybrid characteristics of CPEs make them promising candidates for improving the interface between the organic active layer and the metallic electrode 2-6. In this contribution, we present a series of water/alcohol soluble CPEs we have developed by properly combining different monomers in the conjugated backbone as fluorene, thiophene, benzodithiazole and/or cyclopentadithiophene with pendant polar and/or cationic or anionic groups in view of their specific application. We report their successful integration in organic and hybrid prototypes to highlight their advantages in term of enhanced device stability and efficiency.