Crystallization behavior of poly(p-dioxanone) with cyclodextrin complex and nucleation mechanism discussion

In the interest of improving the crystallization rate of poly(p-dioxanone) (PPDO) without introducing any toxic nucleating agents, an inclusion complex (IC) based on beta-cyclodextrin (beta-CD) and polyglycolide (PGA) serving as a green nucleating agent for PPDO was achieved by a solution technique. The formation of PGA-IC was verified by FT-IR, WAXD, and DSC. The crystallization kinetics and morphology of PPDO and its composites with 3 wt% PGA-IC or beta-CD were investigated by DSC and POM. The results indicated that both beta-CD and PGA-IC could enhance the crystallization of PPDO, with PGA-IC being the more effective of the two. The nucleating efficiency of PGA-IC is 33.1%, and with the addition of PGA-IC, the nucleation density of PPDO increased by 2-3 orders of magnitude. A reduction of surface free energies was detected according to the analysis of crystal growth behavior. A possible mechanism based on Titus and Millner's model is put forth to interpret the nucleation effect. The hydrophilic interaction as well as the different crystalline structures of PGA-IC and beta-CD were supposed to be the key factors for their different nucleation abilities. Poly(epsilon-caprolactone) was chosen as a polymer matrix to discuss the hydrophilic interaction's influence on the nucleation effect of PGA-IC.