Recyclable low-temperature phase change microcapsules for cold storage

Recyclable low-temperature phase change microcapsules (LTPCMs) have the potential applications in the short-distance cold chain transportation due to their reliable reusability in cold storage. Herein, LTPCMs are synthesized via in-situ suspension copolymerization of styrene and methyl methacrylate in absence of harm substances, providing the non-crosslinking copolymer shells. n-Dodecane, n-tridecane and n-tetradecane, inducing the microphase separation of non-crosslinking copolymers, are successfully encapsulated to achieve n-do-LTPCMs, n-tri-LTPCMs and n-tetra-LTPCMs, which respectively bear the high phase change enthalpy of 110.53 J·g-1 at -8.69 °C, 38.33 J·g-1/93.71 J·g-1 at -17.61 °C/-4.96 °C and 166.79 J·g-1 at 8.59 °C and subsequently show the cold-discharging periods of 30 min, 40 min and 120 min. The multiple circulation of cold-discharging process indicates the excellent recyclability for cold storage owing to their unchanged cold-discharging period. Especially, n-tetra-LTPCM-65 bears the best comprehensive cold-storing performance in all the previously reported LTPCMs, such as narrow cold-discharging temperature range of 3-4 °C, long cold-discharging period of 69-120 min and low cold-discharging capacity of 33.4 J·g-1·K-1. This work successfully provided the recyclable LTPCMs for cold storage in the short-distance cold chain transportation.