In situ prepared poly(DL-lactic acid)/silica nanocomposites: Study of molecular composition, thermal stability, glass transition and molecular dynamics

The objective of the present study was to prepare a series of poly(DL-lactic acid) (PDLLA) nanocomposites with four different amounts of silica (SiO2) nanoparticles (2.5, 5, 10 and 20 wt%), following a new two-step synthesis route: ring opening polymerization of DL-lactide and polycondensation. Effects of different percentage of SiO2 on various properties such as molecular weight, crystallinity, thermal stability, glass transition temperature (T-g) and molecular dynamics, are discussed and compared with the theoretical models available in literature. Thermal stability of PDLLA was substantially enhanced from the addition of SiO2, while calorimetry and dielectric spectroscopy showed increased T-g in the nanocomposites, as well as indications for formation of interfacial rigid amorphous polymer fraction.