Novel copolymers of vinyl acetate. 2. Oxy ring-substituted ethyl 2-cyano- 3-phenyl-2-propenoates

Novel copolymers of vinyl acetate and oxy ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO2C2H5 (where R is 2-methoxy, 3-methoxy, 4-methoxy, 2-ethoxy, 4-ethoxy, 4-propoxy, 4-butoxy, 2,3-dimethoxy, 2,4-dimethoxy, 2,5-dimethoxy, 3,4-dimethoxy, 2,3,4-trimethoxy, 2,4,5-trimethoxy, 2,4,6-trimethoxy, 3,4,5-trimethoxy) were prepared in solution with radical initiation at 70C. The propenoates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and ethyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C-NMR. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, 1H and 13C-NMR. Thermal behavior of the copolymers was studied by DSC (Tg) and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 160-350ºC range with residue (2.2-25.3 wt%), which then decomposed in the 500-650ºC range.

TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 160-350ºC range with residue (2.2-25.3 wt%), which then decomposed in the 500-650ºC range.

Copolymerization
Copolymerization (Sch. 1) of VAC and the ring-substituted EOCP resulted in formation of copolymers (Table 1)  According to the nitrogen elemental analysis, between 42.2 and 49.9 mol% of TSE monomer is present in the copolymers prepared at VAC/EOCP = 3 (mol), which is indicative of relatively high reactivity of the monomers towards VAC. According to the nitrogen elemental analysis, between 42.2 and 49.6 mol% of TSE monomer is present in the copolymers prepared at VAC/EOCP = 3 (mol), which is indicative of relatively high reactivity of the monomers towards VAC.

Structure and Thermal Properties
The structure of VAC-EOCP copolymers was characterized by IR and NMR spectroscopy.
A comparison of the spectra of the monomers, copolymers, and polyvinyl acetate with the spectra of ring-unsubstituted ethyl 2-cyano-3-phenyl-2-propenoate -VAC [28] shows, that the reaction between the EOCP monomers and VAC is a copolymerization.
The copolymers prepared in the present work are all soluble in ethyl acetate, THF, DMF and CHCl3 and insoluble in methanol, ethyl ether, and petroleum ether. They are amorphous and show no crystalline DSC endotherm. Results of thermal analysis of VAC-EOCP copolymers are presented in Table 1. Relatively high Tg of the copolymers (78-154 ºC) in comparison with that of polyvinyl acetate, Tg = 28-31ºC [29] indicates decrease of chain mobility of the copolymer due to the high dipolar character of the EOCP structural units.
Information on the degradation of the copolymers was obtained from thermogravimetric analysis. Decomposition of the copolymers in nitrogen occurred in two steps, apparently acetic acid elimination [30] in 160-350ºC range followed by more slow decomposition of formed residue (25.9-2.2 wt%), which then decomposed in the 500-650ºC range.
Oxy ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates were prepared and copolymerized with vinyl acetate. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, H 1 and 13 C-NMR. Thermal gravimetric analysis indicated that the copolymers decompose in in two steps, first in the 200-500C range with residue (13-16 wt%), which then decomposed in the 500-650ºC range.