A novel regiospecific MDMO−PPV copolymer has been synthesized by the copolymerization of the mixture of 70 wt % 1-(chloromethyl)-5-[(3,7-dimethyloctyl)oxy]-2-methoxy-4-[(octylsulfoxy)methyl]benzene (monomer A) and 30 wt % 1-(chloromethyl)-2-[(3,7-dimethyloctyl)oxy]-5-methoxy-4-[(octylsulfoxy)methyl]benzene (monomer B) via the sulfinyl precoursor synthetic route. The hole mobility of the new regiospecific MDMO−PPV polymer (also called OC1C10−PPV) measured with a time-of-flight setup is found to be a factor of ∼3.5 higher at all measured electric fields at room temperature as compared to regiorandom MDMO−PPV. The electric field and temperature dependence of the hole mobility is discussed in the framework of disorder formalism. The improved charge transport properties of the novel regiospecific MDMO−PPV copolymer is attributed to the better interchain interactions facilitated by the more regular PPV backbone, which is also supported by the red shifted optical absorption and photoluminescence. Finally, the im...