MMT and LDH organo-modification with surfactants tailored for PLA nanocomposites

Low molecular weight polyesters were end-functionalized with ammonium and carboxylate salts and used in ionic exchange reactions with respectively cationic (MMT) and anionic (LDH) clays. The hybrid organic-inorganic substrates were structurally analysed to determine the ester oligomers' modification degree and their thermal behaviour owing to confinement effects. The dispersion of such hybrids in polylactic acid (PLA) matrix was performed and the ultimate structural, morphological and thermal properties of the collected nanocomposites were investigated and correlated to the tailored interfacial properties with the different inorganic substrates. While the composites with MMT proved to be stable under thermo-oxidative conditions, the samples obtained by dispersing the LDH hybrid suffered from poor final thermostability owing to molecular weights decrease. Deeper insights about the effect of the interactions at interface (polymer chain-surfactant and polymer chain-inorganic surface) evidenced that by promoting an intimate contact between PLA chains and LDH surface (through oligoester used as inorganic substrate modifier) a certain extent of PLA hydrolysis triggered by both surfactant and inorganic surface (LDH) occurred and cannot completely avoided.