Preparation, performance and structure-properties relationship of poly (lactic acid)/modified saponite nanocomposites based on thiol-ene click chemistry

Saponite (SA)-mercaptopropyl polyhedral oligomeric silsesquioxane (POSS-SH) grafted poly (L-lactic acid) (SA-POSS-PLLA) was synthesized by thiol-ene click chemistry. SA-POSS-PLLA was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. When 0.3 wt% SA-POSS-PLLA was used as a modifier in poly (lactic acid) (PLA), the impact strength and elongation at break of PLA/SA-POSS-PLLA nanocomposites were increased by 1.73 times and 4.25 times compared with pure PLA, respectively. The differential scanning calorimeter analysis showed that the crystallinity of PLA/SA-POSS-PLLA nanocomposites was increased from 7.74% to 30.32%. The addition of SA-POSS-PLLA increased the crystallization rate of PLA and significantly reduced the grain size of PLA, which also was proved by polarization optical microscopy analysis. Rheonaut technology for simultaneous rheometry and FTIR demonstrated that the reason why the addition of SA-POSS-PLLA nanoparticles accelerated the crystallization rate of PLA was that SA-POSS-PLLA nanoparticles promoted the adjustment of C-O-C structure and -CH3 group in the main molecular chain of PLA.