Kinetic behavior in free-radical polymerization of isomer methacrylic monomers with active functional groups as side substituents
✍ Scribed by Carlos Elvira; Angel E. Lozano; Julio San Román
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 187 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0887-624X
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✦ Synopsis
The kinetic behavior of the free-radical polymerization of 2-hydroxy-4-Nmethacrylamidobenzoic acid (4-HMA) and 2-hydroxy-5-N-methacrylamidobenzoic acid (5-HMA) in a solution of N,N-dimethylformamide is described. The methacrylic monomers 4-HMA and 5-HMA were isomers in which the phenolic and carboxylic functional groups were in different positions on the side aromatic ring with respect to the methacrylamide group. Semiempirical (AM1 and PM3 treatments) and ab initio (6-31G**) quantum mechanical calculations indicated the existence of intramolecular H-bonding between the phenolic and carboxylic groups. These calculations also indicated a slightly higher reactivity of 4-HMA with respect to 5-HMA under the same experimental conditions as obtained from the frontier orbital interactions between the highest molecular orbital of the monomers and the singly occupied molecular orbital of the radical obtained by the reaction of a methyl radical with the corresponding monomer. Gravimetric study of the free-radical polymerization of 4-HMA and 5-HMA at several temperatures ranging from 50 to 150 °C demonstrated this behavior. The kinetic results obtained and the average molecular weights of the polymers prepared at different temperatures indicated that the monomer 4-HMA had a slightly higher reactivity at low temperatures (50 -90 °C), whereas at higher temperatures (120 -150 °C), the reactivity of both monomers became similar as a consequence of the "dead-end" radical polymerization.