Quantifying the thermodynamic interactions of polyhedral boranes in solution to guide nanocomposite fabrication

The solubility of boron containing nanoparticles in a variety of solvents is quantified using static light scattering in conjunction with refractometry. Four polyhedral boranes were tested in this work, using refractometry to obtain dn/dc, while static light scattering quantifies A2. A2 obtained from these measurements was then used to calculate χ, the solute–solvent interaction parameter, and the Hildebrand solubility parameter, δ, which provides a quantifiable method to identify good solvents. Of the nanoparticles studied, 1,3-di-o-carboranylpropane is thermodynamically stable in toluene, with a χ less than 0.5, a solubility limit of 2.47 mg/mL, and all solutions remaining clear with no visible particle settling. For all of the particles tested, there was good correlation between the physical observations of the solutions, χ, and δ. For instance, lower values of χ correspond to a smaller radius of gyration (Rg). A list of suitable solvents based on δ is also presented.