Polymorphic structure
The crystal polymorphic form of MKF was determined by a powder x-ray diffractometer (Rigaku RINT-TTR, Rigaku Corporation, Tokyo, Japan). The wavelength was 1.54 Å (CuKα). Scans were performed in wide-angle x-ray scattering (WAXS) from 15° to 27° with a scan speed and a step width of 4°/min and 0.02°, respectively. The crystallization temperature for the experiments in this section was changed from 25 to 18 °C because the x-ray diffraction intensity of the sample crystallized at 25 °C was too weak. At 15, 30 and 60 min of the crystallization time, ∼1 g of the sample was carefully taken from the glass cell and gently placed in the x-ray sample holder and the polymorphic structure of the sample was characterized.