Rapid crystallization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer accelerated by cyclodextrin-complex as nucleating agent

The nucleation effect of inclusion complex (IC) between poly(3-hydroxybutyrate) (PHB) and alpha-cyclodextrin (α-CD) on the rapid crystallization of a series of bacterial copolyesters poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with 3HH molar fraction ranging from 7 to 18 mol% was investigated by differential scanning calorimetry (DSC) and a polarized optical microscopy (POM). The results were compared with the effectiveness of PHB particles as a nucleation agent. Both the PHB-IC and the PHB particles enhance the nucleation and crystallization of PHBH, whereas the PHB-IC particles show much more effective nucleation ability than the PHB particles for the crystallization of PHBH. With introduction of PHB-IC, PHBH with 18% 3HH unit can finish crystallization during cooling process from the melt at 10 °C/min, and its crystallinity is greatly increased. The crystallization half-time (t1/2) of PHBH with 7–18% 3HH units decreases significantly in the presence of PHB-IC. The PHB crystals in the PHB-IC are suggested to favorably nucleate PHBH crystallization with the same crystalline lattice.