Abstract
The kinetic of D,L-lactide polymerization in presence of biocompatible zirconium acetylacetonate initiator was studied by differential scanning calorimetry in isothermal mode at various temperatures and initiator concentrations. The enthalpy of D,L-lactide polymerization measured directly in DSC cell was found to be ΔH=-17.8±1.4 kJ mol(-1). Kinetic curves of D,L-lactide polymerization and propagation rate constants were determined for polymerization with zirconium acetylacetonate at concentrations of 250-1000 ppm and temperature of 160-220 °C. Using model or reversible polymerization the following kinetic and thermodynamic parameters were calculated: activation energy E(a) =44.51±5.35 kJ mol(-1), preexponential constant lnA=15.47±1.38, entropy of polymerization ΔS=-25.14 J mol(-1) K(-1). The effect of reaction conditions on the molecular weight of poly(D,L-lactide) was shown.