The copolymerizations of m-isopropenyl-alpha,alpha＇-dimethylbenzyl isocyanate (m-TMI) with styrene (STY) was investigated. The weight conversion of the copolymerization reaction increased as the duration of copolymerization increased. The reaction temperature was maintained between 60 and 75 degrees C. Molecular weights of the copolymers decreased with increasing molar fraction of m-TMI in the feed. This study obtained reactivity ratios, Alfrey-Price parameters, Mark-Houwink constant, characteristic ratio, thermal degradation activation energy, difference of reactive propagation activation energy, and intrinsic viscosity for the copolymers. The copolymers were characterized by using elemental analysis (EA), gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. The copolymer chains in solution were observed to have a high degree of stiffness and a lack of rotational freedom.