Nucleation effects of α-cyclodextrin inclusion complexes on the crystallization behavior of biodegradable poly(1,4-butylene adipate)

Abstract

This study examined the polymorphic crystallization behavior of poly(1,4-butylene adipate) (PBA) with the addition of nucleation agents such as the α-cyclodextrin (α-CD) inclusion complex (IC) of PBA (PBAIC) and the IC of poly(ε-caprolactone) (PCLIC). The formation of PBAIC and PCLIC was characterized by ¹H NMR, Fourier-transform infrared (FT-IR) spectroscopy and wide-angle X-ray diffraction (WAXD). The differential scanning calorimetry (DSC) and WAXD results suggest that some of the PBA segments remained outside the α-CD cavities even after the formation of ICs with α-CD. WAXD investigation also confirmed that the ICs had a channel structure. The DSC and polarized optical microscopy (POM) results showed the ICs to exhibit nucleation effects on the crystallization and polymorphic behavior of the PBA. The cooling rate played a significant role in the polymorphic crystallization behavior of the pure PBA. Thus, when the cooling rate was decreased, the crystal structures changed from β to α-form and vice versa. The blending of a nucleating agent with the PBA led to higher crystallization temperatures, thus favoring the nucleation of the α-form crystal of PBA rather than pure PBA. The nucleating activity of the PCLIC during the crystallization of the PBA was higher than that of PBAIC.