Influence of solvent properties and intermolecular interaction between solute and solvent on nucleation kinetics of HMBTAD

The induction time of HMBTAD was measured in four pure ester solvents and acetone + acetonitrile binary solvent mixtures at 283.15 K with different supersaturation. The wide variation of induction time shows the stochastic nature of nucleation process and can be expressed as the Poisson distribution. In ester solvents, the nucleation rate is the largest in methyl acetate and the smallest in isobutyl acetate, with ethyl acetate and propyl acetate in between. Adding acetone to the supersaturated solution of acetonitrile makes the nucleation rate slower. The calculated interfacial energy of HMBTAD in pure ester solvents increases in the order: methyl acetate < ethyl acetate < propyl acetate < isobutyl acetate. In acetone + acetonitrile binary solvent mixtures, the interfacial energy increases with the increase of the mole fraction of acetone. It is interesting to find that the interfacial energy can be correlated to the solubility data and the dielectric constant in different solvents with high accuracy. In addition, the influence of intermolecular bonding between the solute and the solvent on the nucleation difficulty has been further evaluated and analyzed based on the Raman spectra of crystal and saturated solution of HMBTAD.