Simultaneous Enhanced\nMechanical Properties and Foamability\nof Biodegradable PBAT via Physical Cross-Linking through Reactive\nBlending

While fully biodegradable poly(butylene adipate-<i>co</i>-terephthalate) (PBAT) is considered to be one of the\nmost promising\nmaterials, the application of PBAT materials is still hindered due\nto its intrinsic low mechanical strength and poor foamability. Herein,\na strategy is addressed to construct PBAT-based supramolecular bionanocomposites\nof high strength and excellent foamability with homogeneous dispersion\nof UPy aggregates via quadruple hydrogen bonding. The biocomposite\nwas prepared by direct melt-blending of isocyanate-terminal ureido-pyrimidinone\n(UPy-NCO) and PBAT. It was found that the terminal hydroxyl group\nof PBAT quickly reacted with the isocyanate group of UPy-NCO during\nthe mixing and in-situ formed a dimerized supramolecular polymer (PBAT-UPy-UPy-PBAT)\nowing to quadruple hydrogen bonding. The PBAT-UPy-UPy-PBAT could be\nfurther folded via longitudinal hydrogen-bonding interactions between\nthe ureido groups of UPy units, forming ordered needle-like UPy nanoassemblies\nin the PBAT matrix. Such particular nanoassemblies could function\nas physical cross-linking points for PBAT-based composites, resulting\nin simultaneous improved mechanical strength and foamability of PBAT.\nThis work paves a feasible avenue for manufacturing high-performance\nPBAT biocomposites and corresponding foams, which is challenging in\nexisting industrial technologies.