Fractal character of triglyceride spherulites is a consequence of nucleation kinetics

Multicomponent triglyceride mixtures crystallize from the melt to form polycrystalline clusters, or spherulites, under low undercooling. Using polarized light microscopy and image analysis, we show that spherulite diameter scales with the mass fraction of solids in a power law fashion, with a characteristic fractal dimension (D = 1.71) whose value was in close agreement with image analysis results (D = 1.73). This suggests that the internal spatial distribution of mass within these spherulites is fractal in nature. Based on these findings, and former work by our group [A.G. Marangoni, S.E. McGauley, Cryst. Growth Des. 3 (2003) 95–108; H.D. Batte, A.G. Marangoni, Cryst. Growth Des. 5 (2005) 1703–1705], we then derive a relationship between spherulite diameter and the free energy of nucleation.