A self-assembled montmorillonite-carbon nanotube hybrid nanoreinforcement for poly-l-lactic acid bone scaffold

Abstract

The high tendency of montmorillonite (MMT) or carbon nanotube (CNT) agglomeration makes their uniform dispersion as reinforcements in biopolymer a great challenge. Herein, CNT was acidified to produce carboxylic groups and then grafted with aminopropyltriethoxysilane (KH550) followed by reacting with glacial acetic acid, which introduced ammonium salt onto the surface of CNT. The ammonium salt-grafted CNT could intercalate into the interlayers of MMT through cation exchange reaction between the alkylammonium cations and the sodium cations of MMT to form a self-assembled MMT-CNT hybrid nanostructure. In this nanostructure, tubular CNT sandwiched between the interlayer of MMT reduced the stacking of MMT, whereas the lamellar MMT acted as steric hindrance to block the entanglement of CNT, thus improving the dispersion of each other via a synergistic effect. As a result, the incorporation of MMT-CNT hybrid into poly-l-lactic acid scaffold enhanced the mechanical properties, including tensile strength and modulus increased by 113.04% and 111.46%, respectively, and compressive strength and modulus increased by 58.20% and 63.27%, respectively. In addition, the scaffold exhibited improved hydrophilicity and degradability, and favorable affinity for cell adhesion, growth and proliferation.