AbstractAn investigation was carried out of the anionic copolymerization of methyl methacrylate (M1), 2‐methoxyethyl methacrylate (M2), and 2‐(N, N‐dimethylamino) ethyl methacrylate (M3) in benzene solution at 20°C initiated with lithium tert‐butoxide. The monomer reactivity ratios (M1–M2)r1= 1.51 ± 0.05,r2= 2.10 ± 0.10, (M1–M3)r1= 1.20 ± 0.10,r3= 0.40 ± 0.05, (M2–M3)r2= 1.40 ± 0.15,r3= 0.60 ± 0.15 show that the reactivities of the individual monomersM1,M2, andM3do not differ too much from each other. A study of the microstructure of copolymersM1–M2by the NMR method revealed that at low conversions the tacticity of the copolymers depends on the concentration of 2‐methoxyethyl methacrylate in the starting monomer mixture; in the initial stage of copolymerization it is strongly dependent on conversion. Already a low content ofM2in the starting monomer mixture (below 1%) strongly affects the tacticity of the forming copolymer by depressing the content of