Dynamics of the amorphous and crystalline α, γ-phases of indomethacin

Crystallization processes in indomethacin can be observed below T-g leading to different forms depending on the thermal treatment: a rapid and deep quench below T-g leads to the metastable alpha-phase and a slow cooling close to T-g gives rise to the stable gamma-phase. To understand this atypical behavior, we have studied the molecular mobility of the amorphous and crystalline forms of indomethacin by dielectric relaxation and H-1 NMR spectroscopy. Two relaxations were detected in the glassy state obtained from the deeply quenched liquid. One, also present in the gamma-phase, was attributed to local rotations. The other one, of very low amplitude, was attributed to the Johari-Goldstein relaxation. The results allowed to discuss the relationship between these two relaxation processes and the crystallization properties of amorphous indomethacin.