Surface-relief and interior lamellar assembly in Janus-face spherulites of Poly(butylene succinate) crystallized with Poly(ethylene oxide)

Polarized-light optical, atomic-force, electron scanning microscopies and X-ray techniques were applied to reveal and analyze a highly anisotropic crystal aggregation into Janus-face spherulites in poly(butylene succinate) (PBSu) induced by crystallization in presence of molten poly(ethylene oxide) (PEO) at T_c = 70 °C. The dual-face (i.e., Janus-face) PBSu spherulites are distinguished with various fractions of two different lamellar assemblies filling the spherulites’ two portions. The Janus-face PBSu crystals (straight dendritic and circularly ring-banded lamellae) become significant only when the PEO content is kept at 20–30 wt% in the blended PBSu/PEO mixtures at T_c = 70 °C, with no top-cover confinement. That is, existence of Janus-faced spherulite is highly kinetics-selective for favorable nucleation to highly anisotropic growth into co-existence of two faces. Mechanisms of unique nucleation and interior lamellae assembly into the peculiar Janus-face PBSu spherulites are analyzed and discussed.