Crystal Nucleation in Ibuprofen Glass: Possible Relevance between the Characteristic Length of the Cooperatively Rearranging Region and the Size of Crystal Nuclei

Crystallization behavior of ibuprofen glass was investigated with focus on the nucleation process and its possible relevance to the cooperatively rearranging region (CRR). The nucleation temperature range of ibuprofen glass was determined by annealing it at various temperatures, followed by observation of the probability of cold crystallization. The temperature to provide the highest probability of nucleation was -15 °C. The effect of the addition of a polymer was also investigated to find that it enhanced and suppressed the crystallization depending on the polymer species and its amount added. The added polymer seemed to influence both nucleation and crystal growth processes by decreasing the glass/nuclei interfacial tension and increasing viscosity, respectively. In addition, the coincidence of the size of CRR in the presence of the polymer with the critical size of nuclei was assumed to enhance nucleation. This finding provides a novel viewpoint for clarifying the nucleation mechanism from supercooled liquids and glasses.