Effect of alkyl group substituents on the thermal and enzymatic degradation of poly (n-alkyl acrylates)

Effect of alkyl group substituents on the thermal and enzymatic degradation of poly (n-alkyl acrylates) J. P. Mahalik and Giridhar Madras∗ Department of Chemical Engineering, Indian Institute of Science, Bangalore-12 Abstract The effect of alkyl group substituents on the thermal degradation kinetics of poly (n-alkyl acrylate) was investigated in pyrolysis and in solution. The activation energies for the pyrolytic degradation of poly (n-butyl acrylate) (PBA), poly (ethyl acrylate) (PEA), and poly (methyl acrylate) (PMA), determined by the Friedman's technique, were 150, 170 and 203 kJ/mol, respectively. For the thermal degradation of the polymers in solution, a continuous distribution kinetic model was used to determine the random chain degradation rate coefficients. The activation energies, determined from the temperature dependence of the rate coefficients, for PBA, PEA and PMA in solution were 109, 117, and 138 kJ/mol, respectively. This indicates that the variation of the activation energies with chain length of the substituent in the polymer is similar to degradation both by pyrolysis and in solution, though the values obtained are lower for degradation in solution. The enzymatic degradation of these polymers was also investigated at different temperatures with various enzymes (Novozym 435, Lipolase and Porcine Pancreas) in different solvents. A continuous distribution kinetic model was used to evaluate the polymer chain end scission rate coefficient. The degradation rates were highest when the acrylates were degraded in presence of Porcine Pancreas in toluene at 50 C.