2014 JPCC

ABSTRACT. The diameter of imogolite nanotube was regulated by altering the synthesis temperature and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and ²⁹Si cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS-NMR). Imogolite diameter modulation via thermodynamic control was induced by the curvature formation of proto-imogolite cluster which depends on the degree of silanol (Si-OH) substitution. At lower temperature, 323K, the amount of SiOH substitution on proto-imogolite clusters decreases and accordingly reduces the hydrogen bonding among SiOH substituents. On the other hand, at higher temperature, 371K, large amount of SiOH substitution on proto-imogolite cluster increases the hydrogen bonding among silanol groups which also increases the degree of curvature. The proto-imogolite clusters with a larger curvature can quickly create tubular structures by closing a circle with a smaller diameter.