Novel Copolymers of Trisubstituted Ethylenes and Styrene. 9. Some Ring-Substituted Ethyl 2-Cyano-1-oxo-3-phenyl-2-propenylcarbamates

Electrophilic trisubstituted ethylenes, ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC₆H₃CH = C(CN)CONHCO₂C₂H₅(where R is 2-CN, 3-CN, 4-CN, 3-Br- 4-CH₃O, 5-Br-2-CH₃O, 5-Br-2,3-(CH₃O)₂, 5-Br-2,4-(CH₃O)₂), were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR, ¹H- and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H- and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 5-Br-2-CH₃O (3.4) > 5-Br-2,3-(CH₃O)₂ (1.7) > 3-Br- 4-CH₃O (1.4) > 5-Br-2,4-(CH₃O)₂ (0.7) > 4-CN (0.4) > 3-CN (0.4) > 2-CN (0.3). High T _g of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene structural unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 250–420°C with residue (5–15% wt), which then decomposed in the 420–650°C range.