α‐Melt‐mediated crystallization of 1‐palmitoyl‐2‐oleoyl‐3‐stearoyl‐<i>sn</i>‐glycerol

Abstract

Abstract The α‐melt‐mediated crystallization of 1‐palmitoyl‐2‐oleoyl‐3‐stearoyl‐ sn ‐glycerol (POS) has been investigated by differential scanning calorimetry (DSC), combined with polarized‐light microscopy. Starting from a completely liquid state, the melt was first cooled down and maintained at a temperature, T 1 , during a time, t 1 , where the α‐phase formed. Then it was heated to a temperature, T 2 , above the melting point of α for isothermal solidification into a solid phase, which was identified as δ. Based upon DSC solidification peaks, the time‐temperature‐transformation (TTT) diagram of POS was constructed for these solidification conditions and was compared with the TTT diagram of direct crystallization from the melt. The α‐melt‐mediated solidification showed accelerated kinetics of the δ‐phase. The effects of T 1 and t 1 were also studied: at short t 1 , crystallization was faster with a decreasing value of T 1 , whereas the opposite trend was observed for a longer plateau at T 1 . These tendencies were interpreted in terms of three competing phenomena: the density of δ‐nuclei that can form during the plateau at T 1 , α‐δ solid‐state transformation, and memory effects of molecule arrangements in the α‐remelted phase.