Low yields copolymerization of styrene (S) with di-n-alkylitaconates (DI-n) and methyl n-alkylitaconates (MeI-n) with alkyl side chain of 12, 14, 16, 18 and 22 carbon atoms were carried out in bulk via radical at 60oC with AIBN as initiator. The copolymers chemical structure was characterized by FTIR and 1H and 13C-NMR, and the composition was determined by 1H-NMR. The NMR studies indicate that the copolymers are random, but with some tendency to alternation. The monomers reactivity ratios between the styrene and itaconates in the copolymerization (ri) were calculated by the Fineman-Ross (FR), Kelen Tudos (KT) methods and a modification of the last one. The obtained values of r1(DI) and r2(S) in the copolymerization among DI-n with n = 12, 14 and 16 with S were in the range of 0.22 to 0.28 for DI-n and 0.19 to 0.39 for S. Whereas for DI-n with n = 18 and 22 the values are in the order of 0.42-0.50 and 0.37-0.47 respectively. For the copolymer series derivatives of MeI-n the values were between 0.01-0.41 for the itaconate and 0.44-0.97 for S.