The growing process of poly(ethylene oxide) (PEO) spherulites was examined by optical microscopy. Using unpolarized white light instead of cross-polarized light as the incident beam, the formation of multicolored ring stripes could be more clearly displayed. As the growing two-dimensional spherulites impinged with each other, the shoved-up melt near the boundary changed its original crystallization direction and habit. The residual shoved melt flowed towards the center of the spherulites and gradually crystallized on their upper surface below the cover glass plate. Since the amount of the residual melt was limited, the thickness of the surface crystallized layer was diminished and disk-like vacuum wedges were formed under the cover slide. Such interspaces caused the formation of the multicolored ring stripes belonging to the category of equal-thickness interference. The present experiment was in fact a direct visual observation of secondary crystallization of two-dimensional spherulites, and the obtained results may offer an insight into theoretical development of secondary crystallization.

Key words: polymer spherulite, multicolored ring stripe, equal thickness interference, poly(ethylene oxide) (PEO), secondary crystallization