Modeling the pH-dependent PLA oligomer degradation kinetics

摘要

The hydrolysis of lactic acid oligomers involves several different reactions, acid-catalyzed, base-catalyzed as well as non-catalyzed. In the present paper a pH-dependent kinetic model has been developed and its kinetic constants evaluated by fitting to experimental data of degrading lactic acid oligomers at 37 ℃ in aqueous solution at pH = 1,2,3.5, 5.7 and 7.4. The model was able to properly describe the experimental data with an average error of about 5%. The estimated values of the kinetic constants at the selected temperature are: kg = 4.44 × 10~3 L~2mol~(-2)h~(-1), k_D~B = 9.29×10~(-4) L~2mol~(-2)h~(-1) (acid-catalyzed), k_(RH) = 1.56×10~3 L~2mol~(-2)h~(-1), k_(BB)=2.88×10~6 Lmol~(-1)h~(-1) (base-catalyzed) and k_w = 2.49×10~5 Lmol~(-1) h~(-1) (non-catalyzed).