Influence of anti-solvent property on the modes of crystallization of HNIW

A study on the methods and processes of crystallization of ε-HNIW was given, and a theoretical explanation of its crystal transformation was found in this paper. The solubility of HNIW almost does not change with variations in the temperature of solution. Therefore only the anti-solvents involved in crystallization is effective in the preparation of ε-HNIW. It is revealed that the physical properties such as the dipole moment and molecular polarity of the anti-solvent play an important role in the process of crystallization of HNIW. When using acetic ether or acetone as the solvents, anti-solvents with lower values of dipole moment, for example petroleum ether, isooctane, cyclohexane, toluene etc, make the HNIW to form an ε-modification, whereas anti-solvents with higher values of dipole moment, such as triethylene glycol, to form other modifications of HNIW. At higher temperatures, the duration that ε-HNIW can keep its modification is longer in non-polar solvents than in polar solvents.