Dispersing surface-modified imogolite nanotubes in polar and non-polar solvents

作者：Li Ming; Brant Jonathan A

来源：Journal of Nanoparticle Research, 2018, 20(2): 19.

DOI：10.1007/s11051-017-4100-7

• Nanocomposite membranes
• Imogolite nanotubes
• Aggregation
• Non-polar solvents
• Water filtration

Furthering the development of nanocomposite structures, namely membranes for water treatment applications, requires that methods be developed to ensure nanoparticle dispersion in polar and non-polar solvents, as both are widely used in associated synthesis techniques. Here, we report on a two-step method to graft polyvinylpyrrolidone (PVP), and a one-step method for octadecylphosphonic acid (OPA), onto the outer surfaces of imogolite nanotubes. The goal of these approaches was to improve and maintain nanotube dispersion in polymer compatible polar and non-polar solvents. The PVP coating modified the imogolite surface charge from positive to weakly negative at pH <= 9; the OPA made it weakly positive at acidic pH values to negative at pH >= 7. The PVP surface coating stabilized the nanotubes through steric hindrance in polar protic, dipolar aprotic, and chloroform. In difference to the PVP, the OPA surface coating allowed the nanotubes to be dispersed in n-hexane and chloroform, but not in the polar solvents. The lack of miscibility in the polar solvents, as well as the better dispersion in n-hexane, was attributed to the stronger hydrophobicity of the OPA polymer relative to the PVP.

• 出版日期2018-1-20