Abstract Radical homo‐ and copolymerizations of 1,3,5‐triacryloylhexahydro‐1,3,5‐triazine ( 1 ) with methyl methacrylate (MMA), styrene (S) and a ‐methylstyrene (MS) were investigated at 60°C in DMF, varying the total concentrations of the monomers as well as the contents of 1 . The monomer reactivity ratios were evaluated using the copolymer composition obtained by elemental analysis, according to the Kelen‐Tüdős method applying the equation of Gibbs. The resulting values for the system 1/MMA , based on the concentration of the CC double bonds, are: r 1 = 0,50, r MMA = 1,76 and for the system 1 /S: r 1 = 0,17, r S = 1,03. Furthermore, the double bond content of the copolymers was determined by thiophenol addition showing a significant variation with the overall monomer concentration in the reaction mixtures concerned. This fact has to be considered when calculating the real monomer reactivity ratios yielding in the case of the system 1 /S the values r 1 = 0,43 and r S = 0,41.
