Relaxation behaviors of enantiomorphic S-ibuprofen as revealed by dielectric and photon correlation spectroscopies

• We measure the dielectric and PCS properties of enantiomorphic ibuprofens.
• The relaxation map of S-ibuprofen is provided.
• The fragility of the enantiomorphic ibuprofen is determined.

Relaxation behaviors of enantiomorphic S-ibuprofen were investigated in its amorphous state by using dielectric and photon correlation spectroscopies. The dielectric relaxation processes of the S-ibuprofen were nearly identical to those of the racemic RS-ibuprofen. The relaxation parameters and the dielectric strengths of the α-process and the D-process for the S-ibuprofen were very similar to those for the RS-ibuprofen. These results indicate that the stereochemistry of ibuprofen molecules do not have any substantial effect on molecular motions in the amorphous state of ibuprofen. The relaxation times of the main relaxation process probed by using the photon correlation spectroscopy were consistent with those of the dielectric α-process. The fragility of the S-ibuprofen was 76, which was nearly the same to that determined based on the thermal relaxation times and smaller than that of the racemic compound.