Reaction kinetics and tacticity of macromolecules. II. Acrylic acid copolymers

Abstract

AbstractThe influence of steric effects and of the microtacticity of polymeric chains has been examined during the hydrolysis of acid–ester copolymers. Four different acrylic acid–ethyl ethacrylate copolymers have been prepared; their molar acid content was 50, 67, 77, and 85%. The rate of hydrolysis was examined at different degrees of neutralization in buffered aqueous solutions at 113°C. The rate was directly proportional to the content of (acid–ester–acid) triads and was highest where the degree of neutralization was equal to 0.5. The final degree of conversion is, however, limited on account of the existence of different stereochemical structures of these (acid–ester–acid) triads. Conventional and isotactic acrylic acid–methyl acrylate copolymers have also been prepared; their molar acid content was 64.5 and 80.5% for the conventional and 67 and 80% for the isotactic copolymers. From the rates of hydrolysis measured at 103°C. in buffered aqueous solutions, it becomes evident that the isotactic polymers hydrolyze 3 to 5 times more rapidly than the conventional polymers; moreover, the final degree of conversion is much higher. Finally conventional and isotactic acrylic acid–tert‐butyl acrylate copolymers have been examined; these copolymers hydrolyze only in the presence of mineral acid; any intramolecular functional interaction is absent in both cases. This stability has been explained on the basis of a different mechanism of hydrolysis of these tertiary butyl esters.