POST-POLYMERIZATION MODIFICATION OF BIOPOLYESTERS: FROM RADICAL GRAFTING TO NANOCOMPOSITES

The preparation of "functional" biopolyesters having specifically targeted properties useful to enlarge their application range are here considered and applied to poly(lactic acid) (PLA) and poly(butylene succinate) (PBS). Two different methodologies are considered and compared: the controlled insertion of specific functionalities, and the building up of multifunctional nanostructured hybrid systems. To fulfill the first approach, the nitroxide radical coupling reaction (NRC) is used as an effective tool to impart new properties without negatively affecting the structural and thermomechanical features of PLA and PBS: TEMPO derivatives bearing different functional moieties ranging from polar groups to pro-fluorescent chromophores, dyes, antioxidants, and nanostructured carbonaceous systems (CNT) are used to functionalize PLA and PBS thus providing materials with tailored properties. For the second approach, the dispersion at the nanoscale level of specially modified anionic clays (hydrotalcites) is investigated for the preparation of multifunctional nanocomposites, where the conventional improvements of mechanical, thermal and barriers properties can be synergistically implemented by special features imparted by the surfactant properties. Dyes, and antioxidants have been successfully intercalated in LDH clays and then dispersed in PLA; by opportune optimization of the interfacial interactions, polymer nanocomposites exhibiting the same photophysical and chemical response properties of the modified clays have been prepared and characterized.