Synchronous\nToughening, Strengthening, and Ultraviolet\nResistance of Immiscible Polylactic Acid/polypropylene Carbonate Blends\nCompatibilized by a Low Threshold of Reactive Janus Nanosheets

Poor toughness limits the use of biobased and biodegradable\npolylactic\nacid (PLA). The conventional method of blending with flexible polymers\ntoughens PLA with a significant loss of strength and incompatibility.\nIn this work, carbon dioxide-based biodegradable polypropylene carbonate\n(PPC) was used as the flexibilizer, and PPC-TiO<sub>2</sub>-epoxy\nJanus nanosheets (JNs) synthesized by grafting PPC-diols and epoxy\ngroups onto each side of titanium dioxide nanosheets respectively\nwere used as compatibilizers. PLA/PPC/JNs blends were then prepared\nby melt processing. The in situ reaction between the epoxy groups\non one side of the JNs and the carboxylic acid groups on the PLA occurs,\nforming a solid covalent bond. The grafted PPC chains on the other\nside of the JNs were tightly entangled with those of the PPC flexibilizer.\nMoreover, due to the Pickering effect of JNs, they can stably anchor\nat the interface, which reduces the interfacial tension and significantly\nenhances compatibility. Compared with PLA/PPC, the addition of as\nlow as even 0.3 wt % JNs reduced the PPC domain size from 3.25 to\n0.42 μm, and consequently, the elongation at break increased\nby 250%. Moreover, the introduction of JNs significantly improved\nthe UV shielding in both UV-A and UV–B regions and the UV aging\nresistance of the blends without reducing the transparency that much.\nHerein, this work provides a new method for improving the compatibility\nof PLA-based blends and preparing high-performance PLA materials.