Synthesis and copolymerization of novel oxy ring-substituted isopropyl cyanoarylacrylates

Novel oxy ring-substituted isopropyl 2-cyano-3-arylacrylates, RPhCH=C(CN)CO2CH(CH3)2 (where R is 3-phenoxy, 4-phenoxy, 2-benzyloxy, 3-benzyloxy, 4-benzyloxy, 4-acetyloxy, 3-acetyl, 4-acetyl, 4-acetylamino, 4-methoxy-2-methyl, 4-methoxy-3-methyl, 3-ethoxy-4-methoxy, 3,4-dibenzyloxy, 3-benzyloxy-4-methoxy, 4-benzyloxy-3-methoxy, 2,3-dimethyl-4-methoxy, 2,5-dimethyl-4-methoxy, 2,4-dimethoxy-3-methyl, 2,4-dimethoxy-6-methyl, 3,5-dimethoxy-4-hydroxy) were prepared and copolymerized with styrene. The acrylates were synthesized by the piperidine catalyzed Knoevenagel condensation of oxy ring-substituted benzaldehydes and isopropyl cyanoacetate and characterized by CHN elemental analysis, FTIR, 1H and 13C-NMR. All the acrylates were copolymerized with styrene in solution with radical initiation at 70C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by FTIR, 1H and 13C-NMR. Thermal properties of the copolymers are characterized by DSC and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500ºC range with a residue, which then decomposed in the 500-800ºC range.


Copolymerization
Copolymers of the styrene (ST) and the ICAA compounds, P(ST-co-ICAA) were prepared in 25-mL glass screw cap vials at ST/ICAA=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 composition of the copolymers was determined based on the nitrogen content (cyano group in ICAA monomers). The conversion of the copolymers was kept between 10 and 20% to minimize compositional drift (Table 1). Since ICAA monomers do not homopolymerize, the most likely structure of the copolymers would be short styrene sequences alternating with isolated ICAA monomer units (n = 1) (Scheme 2).

Structure and Thermal Properties
The structure of ST-ICAA 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 spectra of the copolymers show overlapping bands in 3300-2700 cm 1  were measured by GPC in THF. According to GPC analysis the copolymers had weightaverage molecular masses 24.8 to 64.3 kD ( Table 1).
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-ICAA copolymers prepared in this work with no correlation to the size and position of the ICAA 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 84-154ºC. 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 247-500ºC range with residue (2-11% 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.

Conclusions
Novel trisubstituted ethylenes, oxy ring-substituted isopropyl cyanoarylacrylates 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 two steps, 18 first in the 247-500C range with residue (2-11%wt), which then decomposed in the 500-800ºC range.