CHAPTER 5: Surface Modification of Halloysite

As naturally occurring nanotubular clay, halloysite nanotubes (HNTs) have found many important applications, such as reinforcement for polymers, sustained release of functional substances, immobilization of functional substances for catalysis or pollutant removal, etc. These applications are largely determined by the surface modification of HNTs, which is one of the key factors that govern the composite structure and functions. In this chapter, the modification chemistry and the state-of-the-art modification techniques for HNTs are summarized in detail. Broadly, these methods are categorized into covalent methods and non-covalent methods. Except for the commonly known silanization and wrapping via hydrogen bonding/electrostatic interaction, several interesting modifications, including controlled enlargement of the lumen and selective inside/outside modification of the lumen, are highlighted.