Kinetics of phase separation and crystallization in poly(ethylene-ran-hexene) and poly(ethylene-ran-octene)

The kinetics of phase separation and crystallization in the blends of poly(ethylene-ran-hexene) (PEH) and poly(ethylene-ran-octene) (PEOC) at several compositions were studied using phase contrast optical microscopy and time-resolved simultaneous small-angle X-ray scattering and wide-angle X-ray diffraction. The phase contrast optical microscopy showed the interconnected bicontinuous structure during phase separation process, which is characteristic of a spinodal decomposition. During isothermal crystallization, the average lamellar spacing increases with time for blends at all concentrations. The crystallinity and crystal growth rate depend on the PEH concentration. At dilute PEH concentrations, crystallization of PEH chains is difficult because they are surrounded by many non-crystallizable PEOC chains. On the other hand, at higher PEH concentrations, crystallization processes are similar to pure PEH. For example, the spherulitic growth rates are similar for a PEH/PEOC=50/50 blend and pure PEH.