Synthesis and styrene copolymerization of dimethyl, dimethoxy, and halogen ring-substituted isopropyl cyanophenylacrylates

Novel trisubstituted ethylenes, dimethyl, dimethoxy, and halogen ring-substituted isopropyl cyanophenylacrylates, RPhCH=C(CN)CO2CH(CH3)2 (where R is 2,3-dimethyl, 2,4dimethyl, 2,5-dimethyl, 2,6-dimethyl, 3,4-dimethyl, 3,5-dimethyl, 2,3-dimethoxy, 2,4dimethoxy, 2,5-dimethoxy, 2-Br, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-Cl, 2-F, 3-F, 4-F) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and isopropyl cyanoacetate and characterized by CHN elemental analysis, IR, Hand C-NMR. All the ethylenes were copolymerized with styrene in solution with radical initiation (ABCN) at 70C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, H and C-NMR, GPC, DSC, and TGA. Decomposition of

the copolymers in nitrogen occurred in two steps, first in the 219-500C range with residue (0.9-5.6 % wt), which then decomposed in the 500-800ºC range.

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The preparation procedure was essentially the same for all the monomers. In a typical synthesis, equimolar amounts of isopropyl cyanoacetate and an appropriate ring-substituted benzaldehyde were mixed in equimolar ratio in a 20 mL vial. A few drops of piperidine were added with stirring. The product of the reaction was isolated by filtration and purified by crystallization from 2-propanol. The condensation reaction proceeded smoothly, yielding products, which were purified by conventional techniques [35]. No stereochemical analysis of the novel ring-substituted ICPA was performed since no stereoisomers (E or/and Z) of known configuration were available.

Copolymerization
Copolymers of the ST and the ICPA monomers were prepared in 25-mL glass screw cap vials at ST/ICPA = 3 (mol) the monomer feed using 0.12 mol/L of ABCN at an overall monomer concentration 2.44 mol/L in 10 mL of toluene. The copolymerization was conducted at 70ºC. After a predetermined time, the mixture was cooled to room temperature, and precipitated dropwise in methanol. The conversion of the copolymers was kept between below 20% to minimize compositional drift. The composition of the copolymers was determined based on the nitrogen content. The ST-ICPA copolymers were characterized by nitrogen elemental analysis, FTIR, 1 H-and 13 C-NMR spectroscopies. Thermal behavior was studied by DSC and TGA.
Copolymerization (Scheme 1) of ST and the ring-substituted ICPA resulted in formation of copolymers (Table 1)

Structure and Thermal Properties
The structure of ST-ICPA copolymers was characterized by IR and NMR spectroscopy.
A comparison of the spectra of the monomers, copolymers and polystyrene shows, that the reaction between the trisubstituted ethylenes and styrene is a copolymerization. IR All the copolymers were amorphous and show no crystalline DSC endotherm on repeated heating and cooling cycles. Table 2 shows glass transition values for the ST-ICPA copolymers prepared in this work with no correlation to the size and position of the ICPA ring substitution apparently due to non-uniform composition, monomer unit distribution, and/or molecular weight and MWD. A single Tg was observed for all the copolymers with values 111-166ºC. Information on thermal stability of the copolymers ( Table 2) was obtained from thermogravimetric analysis ( Table 2). Decomposition of the copolymers in nitrogen occurred in two steps, first in the 219-500ºC range with residue (0.9-5.6% wt), which then decomposed in the 500-800ºC range. The decomposition products were not analyzed in this study, and the mechanism has yet to be investigated.

Conclusion
Novel dimethyl, dimethoxy, and halogen ring-substituted isopropyl cyanophenylacrylates were prepared and copolymerized with styrene. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, H 1 and 13 C-NMR.
The thermal gravimetric analysis indicated that the copolymers decompose in in two steps, first in the 219-500C range with residue (0.9-5.6 % wt), which then decomposed in the 500-800ºC range.