One-Pot Formation of ZnO-graft-Poly(D,L-Lactide) Hybrid Systems via Microwave-Assisted Polymerization of D,L-Lactide in the Presence of ZnO Nanoparticles

The surface modification of inorganic nanoparticles by polymer grafting is generally required for obtaining well dispersed polymer-based (bio)nanocomposites, and the in situ polymerization of corresponding monomers is considered to be a versatile approach to this purpose. In this work, the microwave-assisted ring-opening polymerization of d,l-lactide in the presence of zinc oxide (ZnO) nanoparticles affords an original and straightforward method for generating ZnO-graft-poly(d,l-lactide) hybrid systems. The influence of ZnO particle size and concentration on polymerization kinetics and molar masses of free poly(d,l-lactide) (PLA) chains is analyzed. Several physico-chemical techniques, including proton nuclear magnetic resonance (H-1 NMR), Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis, are used to characterize intermediates and/or reaction products. Taking into account the kinetic and spectroscopic investigation, competitive chemical pathways based on grafting from and grafting onto reactions are proposed for the one-pot formation of PLA-grafted ZnO nanoparticles.