We report the synthesis of a series of novel polythiophenes with vinylene linked pendant carborane sidechains. Polymers containing ortho, meta and para substituted carborane linked via a cis or trans double bond are reported. The inclusion of carborane sidechains is demonstrated to afford soluble polymers without the presence of any additional alkyl groups. The choice of carborane and double bond isomer is shown to influence the optoelectronic, photovoltaic and charge-transporting properties of the polymer. In particular the incorporation of ortho-carborane was shown to have a pronounced electron withdrawing effect resulting in a substantial increase in polymer ionisation potential. Field effect transistors and solar cells devices fabricated from the various isomers showed significant differences in performance.