Hydrolytic and pyrolytic degradation of poly [2-(N-Methylcarbamoyloxy)-ethyl acrylate]

Poly[2-(N-methylcarbamoyloxy)ethyl acrylate] (PolyMCEA)

was subjected to acid and base hydrolysis at room temperature and to isothermal vacuum pyrolysis at different temperatures. The study aimed to investigate effects of the polymeric structure on the reactivities of the polymer pendent groups.

Appropriate model compounds were synthesized, hydrolyzed and pyrolyzed, and their behavior was compared to that of the polymer in order to provide a better understanding of these effects. A major model compound was 2-(N-methylcarbamoyloxy)ethyl propionate (MCEP).

The results suggested that the ester linkage, in general, was more susceptible to hydrolysis than the carbamate. However, the steric hindrance and the hydrophobicity of the chain and the growing number of carboxyl or carboxylate groups during the hydrolysis of the polymer increased the stability of the ester linkage by shielding it from catalysts. In some acid and base solutions of MCEP, ester hydrolysis was complete before any carbamate hydrolysis was recognized, while simultaneous hydrolysis of the two groups occurred in the polymer, where the ester is more sterically and hydrophobically protected by the chain. In some instances, the hydrolysis of the ester dropped significantly after a substantial growth in the number of carboxyl or carboxylate groups on the chain.

In the pyrolysis of polyMCEA, the polymeric structure favored transesterification reaction between ester groups and hydroxyethyl residues resulting from decomposition of the carbamate. This reaction was neither expected nor observed during the pyrolysis of MCEP, for which ester pyrolysis appeared to proceed by a E_i mechanism.