Lipase catalyzed synthesis of polycaprolactone and clay-based nanohybrids

This study presents the use of original systems based on Candida antarctica lipase B (CALB) immobilized on montmorillonite and sepiolite nanoclays as efficient catalysts for the enzymatic polymerization of ε-caprolactone (ε-CL) and the in situ elaboration of nanohybrids. The kinetic studies showed that the most efficient system was obtained with CALB immobilized on organo-modified montmorillonite. Polycaprolactone (PCL) characterization demonstrated that the hydroxyl groups from the clay organo-modifier participate to the reaction as co-initiators. This allowed the successful in situ elaboration of organic/inorganic nanohybrids by promoting the PCL chains grafting and growth from the hydroxyl groups present at the clay surface. Selective extraction procedures carried out on the nanohybrids and the performed thermogravimetric analyses evidenced the effective grafting of PCL chains from the clay surface. Observations by electronic microscopy further confirmed such PCL chain grafting and demonstrated its positive effect for the elaboration of nanohybrids with finely dispersed clay nanoparticles in the polymer matrix.