Role of complexation strength on the photophysical and transport properties of semiconducting charged polymer complexes

The high polymer loading in complexes of conjugated and insulating polyelectrolytes offers unique opportunities for fabrication of conductive thick films and bulk structures. The electrostatic interactions in these systems provide a handle for controlling their structure and properties. The impact of the charge- mediated complexation strength on the photophysical and electronic transport properties in blends of conjugated polyelectrolytes (CPEs) with oppositely charged polymeric ionic liquids (PILs) is presented here. Varying the frequency of charged repeat units from 50% to 100% on an anionic polythiophene-based CPE and a complimentary cationic PIL results in a model system with controlled complexation strength. In highly charged complexes, the intimate mixing between the CPE and the PIL is found to reduce the structural disorder along the CPE backbone, enhancing its intrachain conjugation and interchain stacking. In weakly charged complexes (<90%), these chain planarization effects are absent and microphase separation occurs. At all charge fractions examined, the electrical conductivity of a doped complex is higher than that of the unblended constituent CPE. The highest electrical conductivity near 1 S cm-1 is found for a charge fraction of 100%. These results demonstrate the potential for designing effective electrical conductors using electrostatic complexation.

Methods
Please refer to the Experimental Methods section in the Manuscript for details on sample preparation and data collection/processing.