Addition of methyl groups to dialkyl fumarates bearing two cyanobiphenyl mesogens dramatically changed the phase-transition behavior and polymerization capability. No mesophase appeared and radical polymerization did not proceed in the absence of the branched methyl groups, whereas well-defined liquid-crystal phases were observed in the ambient temperature range and high molecular weight polymers were obtained in the presence of the branched methyl groups. An increase in the number of the attached methyl groups decreases the liquid crystalline temperature width as well as the molecular weight of the resulting polymers.