DescriptionA comparative study of the electrochemical polymerization of 1,4-di(aryl)-5,5-dimethylcyclopentadienes (XC5X) as a function of aryl group identity (X = thienyl, Th; furyl, Fur; and N-methylpyrrolyl; Pyr groups) is presented. The solubility of charged species generated at the surface of the working electrode during polymerization impedes efficient polymer growth and deposition with only ThC5Th and FurC5Fur monomers affording suitable films for analysis. Poly(ThC5Th) and poly(FurC5Fur) films possess a UV/vis absorption maxima max of 500 nm and 400 nm, respectively, that when oxidized are bleached and give rise to low energy charge-carrier absorption features that are consistent with those observed in poly(terthiophene) and poly(terfuran), respectively. Addition of the anodically activated cross-linking agent 1,3,5-tris(2-aryl)benzenes (3XB) to a solution with XC5X greatly improved the formation of films. Spectroelectrochemical analyses reveal that copolymer films possess higher energy absorption signatures in both the neutral and oxidized state when compared to their corresponding homopolymer, a property attributed to the use of the meta-substituted arrangement of 3XB that is expected to reduce conjugation across the polymer backbone. A compositional variation study was performed comparing the ThC5Th:3ThB system to that of its aromatic congener terthiophene (Th3), Th3:3ThB. Based on the ThC5Th-containing systems, the optical signatures of a film can be tailored towards poly(ThC5Th) by reducing the feed ratio of 3ThB in the comonomer solution. This indicates that film deposition can be improved by adding an additive without compromising the properties observed in the homopolymer.