Eco-friendly synthesis of biodegradable poly(ε-caprolactone) using L-lactic and glycolic acids as organic initiator

Biodegradable poly(epsilon-caprolactone) (PCL) was successfully synthesized by the green polymerization process that was conducted in the absence of heavy metal catalyst and toxic solvent. L-Lactic (LLA) and glycolic acids (GA) were utilized as green initiator for the bulk ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL). These organic initiators could produce PCL with number average molecular weight (M-n) in the range of 8.46 x 10(3)-1.98 x 10(4) g/mol and molecular weight distribution (MWD) of 1.71-1.81. GA could produce higher molecular weight PCL than LLA under identical synthesis condition. The catalytic performance of these initiators in the ROP of epsilon-CL was completely investigated by the non-isothermal differential scanning calorimetry (DSC). From non-isothermal DSC kinetics analysis, the reactivity of GA was higher than LLA in the bulk ROP of epsilon-CL as supported by the lower values of activation energy (E-a) and frequency factor (A) of GA than LLA initiator. The polymerization mechanism for the ROP of epsilon-CL initiated by LLA and GA was proposed through the activated monomer mechanism. [GRAPHICS] .

Automated summary

Biodegradable poly(epsilon-caprolactone) (PCL) was successfully synthesized through a green polymerization process without heavy metal catalyst and toxic solvent. L-Lactic (LLA) and glycolic acids (GA) were used as initiators, producing PCL with different molecular weights in the absence of water. Non-isothermal DSC analysis showed that GA had higher reactivity than LLA in epsilon-CL ROP, and proposed the polymerization mechanism initiated by LLA and GA.