Preparation of PDLLA based nanocomposites with modified silica by in situ polymerization: Study of molecular, morphological, and mechanical properties

In order to prepare poly-D,L-lactide/silica nanocomposites and to improve the interfacial adhesion between these two materials, silanization of silica was realized adopting two different organosilanes, i.e. 3-glycidyloxytrimethoxysilane or 3-aminopropyltrimethoxysilane. Then, resulting modified silica with epoxy or amino terminal functions served as initiating sites for D,L-lactide in situ polymerization allowing the production of poly-D,Llactide/silica nanocomposites. Silica dispersion and mechanical properties of these hybrids were compared to composites prepared with hydrophilic or hydrophobic commercial silica by in situ polymerization. These latter composites disclosed heterogeneities with microscale agglomerates and a drop in mechanical properties for 5 wt% of silica loading. In contrast, composites made from poly-D,L-lactide chains chemically grafted on silica carrying initiation sites disclosed nanoscale dispersion of nanofiller in the PDLLA matrix. In particular, with only 1 wt% of these modified silicas, thanks to the nanoscale dispersion of the inorganic nanofiller, an improvement of 24 % for Young modulus and 51 % for ultimate tensile strength was achieved.