Crystal transition of ε-CL-20 in different solvent

ε-CL-20 was recrystallized from single (alcohol, dichloromethane, acetone and ethyl acetate) and mixed (alcohol-acetone, alcohol-ethylacetate, dichloromethane-acetone, dichloromethane-ethyl acetate and acetone-ethyl acetate with different volume ratio) solvents. The resulting crystal forms were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). ε-CL-20 changes its crystal form only when recrystallizing from acetone, ethyl acetate, and alcohol-acetone; while has little change from other solvents, particularly, from the mixed solvents. The types of recrystallized CL-20 are much dependent on the volume ratio of two components of the mixed solvents, and the crystal transition reflects the ″solvent effect″. The structure of the recrystallized CL-20 from mixed solvents composed of two components is identical with the one obtained from the component with higher dipole moment. This may be relate with solubility of ε-CL-20 in such solvents, while solubility is dependent on the dissolution parameters and the supersaturation degree of the solution.