Polarity of the polymer microenvironment in binary solvents On the microenvironment of polymers in solution. 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. 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 PVP surface coating stabilized the nanotubes through steric hindrance in polar protic, dipolar aprotic, and chloroform. 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 goal of these approaches was to improve and maintain nanotube dispersion in polymer compatible polar and non- polar solvents. 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. Dispersing surface-modified imogolite nanotubes in polar and non- polar solventsįurthering 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.
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