Entropy-Driven Heterocomplexation of Conjugated Polymers in Highly Diluted Solutions

Examples of complexes formed by the association of two dissimilar polymers are scarce. We unravel in this report a rare phenomenon of complexation of two conjugated polymers in highly diluted solutions. Spectroscopy characterization of titrated solutions combined with molecular dynamics and time-dependent density functional theory reveal the presence of strong supramolecular interactions giving rise to the formation of conjugated heterocomplexes of the distinctive charge transfer electronic character. Temperature-dependent studies provide association constants in the 104 to 105 M–1 range and negative van’t Hoff slopes characteristic of entropy-driven association. We explain the entropy gain as the result of solvent molecule release and their subsequent redistribution upon polymer association. Our findings have implications in the field of organic photovoltaics, where the mixing/segregation of polymers of different electronic characters is key to performance.