Performance and multi-scale investigation on the phase miscibility of poly(lactic acid)/amided silica nanocomposites.

In this work, amino-functionalized nano-SiO2 (m@g-SiO2) was synthesized through coupling reaction on the surface of nano-SiO2. Moreover, the optimum preparation conditions of m@g-SiO2 were selected via orthogonal experiments as follows: reaction temperature of 80 °C, reaction time of 8 h, the mass ratio of stearic acid, N,N'‑carbonyldiimidazole, imidazole hydrochloride and g-SiO2 of 0.5:0.7:0.7:1. Fourier transform infrared spectroscopy, static angle measurement and X-ray photoelectron spectroscopy unanimously confirmed the formation of m@g-SiO2. Furthermore, poly(lactic acid)(PLA)/m@g-SiO2 nanocomposites was prepared with m@g-SiO2 as fillers to improve the comprehensive performance of PLA. Then, the mechanical properties and crystallization behavior of PLA/m@g-SiO2 nanocomposites were studied, which showed that the impact strength and elongation-at-break of PLA/m@g-SiO2 (0.3 wt%) nanocomposites were increased by 78.05% and 1148%, respectively, and its crystallinity was increased by 26.46%. Simultaneously, thermal gravimetric analysis indicated that the thermal stability of PLA/m@g-SiO2 nanocomposites was improved. Eventually, the multi-scale investigation on the phase miscibility of PLA/m@g-SiO2 nanocomposites was probed by rheological behaviors analysis and the molecular dynamics simulations, which confirmed that surface modification of SiO2 greatly enhanced the interaction energy and miscibility between the filler and PLA bulk.