Effects of lithium perchlorate on the nucleation and crystallization of poly(ethylene oxide) and poly(ε-caprolactone) in the poly(ethylene oxide)–poly(ε-caprolactone)–lithium perchlorate ternary blend

Abstract

The effects of lithium perchlorate (LiClO₄) on the nucleation and crystallization of poly(ethylene oxide) (PEO) and poly(ε-caprolactone) (PCL) in the PEO–PCL–LiClO₄ ternary blend were studied by using a polarizing optical microscope (POM), differential scanning calorimetry (DSC) and Fourier transformation infrared spectroscopy (FTIR). LiClO₄ has a heterogeneous nucleation effect on PEO in the blend, irrespective of the presence of PCL. The coordination interaction between PEO and LiClO₄ decreases with the increase of the PCL content, so the heterogeneous nucleation ability of LiClO₄ on PEO decreases with the increase of the PCL content in the ternary blends. LiClO₄ has no heterogeneous nucleation effect on PCL. In the ternary blend, the heterogeneous nucleation effect of PEO on PCL is remarkably promoted with the addition of LiClO₄. POM observations show that the miscibility of PEO and PCL improves after the addition of LiClO₄, leading to an increase in the interface volume of PEO and PCL phase domains. The increased concentration-fluctuation at the interface promotes the interfacial nucleation of PCL in the ternary blend. The combination of “fluctuation-assisted crystallization” and “interface-assisted crystallization” mechanisms of the interfacial nucleation of PCL in the PEO–PCL binary blend is also suitable for the interfacial nucleation of PCL in the PEO–PCL–LiClO₄ ternary blend.