Three substituted styrenes were respectively synthesized by reaction of benzoic acid, acetic acid, and methanol with vinylbenzylchloride, then copolymerized with maleic anhydride. The measurements of the reactivity ratios of these three copolymerizations were carried out with a method using high conversions of the reactions. The results show a good correlation between a linear alternating structure for one of the copolymers and an alternating and a partially crosslinked structure for the two others. The copolymerizations were also performed with various percentages of initiator, giving similar proportions of incorporated monomers in the resulting products, and a relation between their viscosities and their weight molecular masses was presented.