Hansen Solubility Parameters for Octahedral Oligomeric Silsesquioxanes

The Hansen Solubility Parameters (HSP) for several polyhedral oligomeric silsesquioxane (POSS) compounds were successfully determined, demonstrating the applicability of the HSP approach for selected types of organic–inorganic compounds. As commonly practiced with organic polymers, a set of simple “pass/fail” tests for complete solubility at a fixed concentration (100 mg/mL) was conducted for an array of five octameric POSS compounds, octa(phenethyl), octa(styrenyl), octa(isobutyl), octakis(hexafluoroisobutyl), and (1-naphthyl)heptaphenyl), and 45 test solvents. Group contributions for the octameric POSS cage were determined using three different approaches, which produced similar results. The best cage contribution estimate for the dispersive, polar, and hydrogen-bonding components δD, δP,, and δH of the total solubility parameter was determined to be δD = 22 (J/cc)1/2, δP = 19 (J/cc)1/2, and δH = 15 (J/cc)1/2, with an estimated uncertainty of approximately 5 (J/cc)1/2. The utility of the HSP approach wa...