Physicochemical characterization of organosilylated halloysite clay nanotubes

摘要: Abstract Halloysite nanotubes (HNTs) were functionalized with several organosilanes different functional groups, by a post-grafting methodology, in aprotic and anhydrous conditions: 3-aminopropyltriethoxysilane (APTES), N-2-aminoethyl-3-aminopropyltrimethoxysilane (AEAPTMS), (3-mercaptopropyl)trimethoxysilane (MPTMS), (3-bromopropyl)-trimethoxysilane (BrTMS), vinyltrimethoxysilane (VTMS) phenyltriethoxysilane (PhTES). The pristine silylated clay minerals characterized transmission scanning electron microscopy, energy-dispersive X-ray spectroscopy, powder diffraction, nitrogen adsorption-desorption isotherms at −196 °C, bulk elemental analysis, photoelectron thermogravimetry, Fourier transform infrared spectroscopy-attenuated total reflectance 13C, 29Si 27Al solid-state nuclear magnetic resonance. techniques identified HNTs as halloysite-7A (dehydrated form) proved their successful silylation without the disruption of structure. showed Si C contents up to 7.30 1.92 mmol/g, respectively, APTES material containing highest surface loadings, confirming its efficiency. Some insights into reaction mechanism also provided used. Combination MAS NMR XRD data suggested that occurred at Al–OH groups from inner lumen surface, well Si–OH edges or external defects; no evidence was found for existence functionalization interlayer groups. proceed through alkoxy moieties organosilane referred 3-fold (for VTMS BrTMS), 2-fold covalent grafting MPTMS) mixture both approaches APTES, AEAPTMS PhTES); case APTES- AEAPTMS-functionalized HNTs, polymerization side-reaction evidenced, parallel pathway.