Role of Complexation Strength on the Photophysical and Transport Properties of Semiconducting Charged Polymer Complexes

The high polymer fraction in complexes of conjugatedand insulatingpolyelectrolytes offers unique opportunities for the fabrication ofconductive thick films and bulk structures. The electrostatic interactionsin these systems further provide a handle for controlling their structureand properties. The impact of charge-mediated complexation strengthon the photophysical and electronic transport properties in blendsof conjugated polyelectrolytes (CPEs) with oppositely charged polymericionic liquids (PILs) was examined. Complexes were formed with varyingfrequency of charged repeat units, from 50 to 100%, on an anionicpolythiophene-based CPE and a complimentary cationic PIL. In highlycharged complexes, the intimate mixing between the CPE and the PILreduced the structural disorder along the CPE backbone, enhancingits intrachain conjugation and interchain stacking. In weakly chargedcomplexes (<90%), these chain planarization effects were absentand microphase separation occurred. At all charge fractions examined,the electrical conductivity of an acid-doped complex was higher thanthat of the unblended constituent CPE. The highest electrical conductivity,near 1 S cm(-1), was found for a charge fraction of100%. These results demonstrate the potential for designing effectivepolymeric conductors using electrostatic complexation.