Supramolecular Nanoarchitectonics of PNIPAAM‐co‐MA and Imogolite to Obtain Thermoresponsive Clay Nanotubes Through Complexation Mechanism

Abstract In this study, the colloidal properties of hybrids formed by imogolite nanotubes (INTs) and poly( N ‐isopropylacrylamide)‐co‐methacrylic (PNIPAAM‐co‐MA) are investigated, which is a thermo‐sensitive copolymer suitable for drug delivery applications. The selective adsorption of anionic PNIPAAM‐co‐MA onto the positively charged external surface of imogolite is driven by electrostatic attractions as evidenced by both ζ‐potential and Dynamic Light Scattering (DLS) experiments. According to polarized optical observations and Small‐angle X‐ray scattering (SAXS) measurements, the specific interactions with PNIPAAM‐co‐MA affect the structural organization of imogolite nanotubes, destabilizing the nematic phase. On the other hand, the formation of PNIPAAM‐co‐MA/INTs complex alters the thermo‐responsive characteristics of the copolymer due to variations on the thermodynamics of the coil‐to‐globule transition of PNIPAAM‐co‐MA. Thermodynamic characterizations (Differential Scanning Calorimetry, Density and Speed of sound experiments) reveal that the lower crystalline solution temperature (LCST) of PNIPAAM‐co‐MA is reduced in the presence of imogolite nanotubes. The attained knowledge represents a starting point to develop thermo‐responsive clay nanotubes useful for biomedical purposes by exploiting the selective coating of imogolite with PNIPAAM‐co‐MA.