聚氧乙烯球晶上彩色环状条纹的形成

Formation of Multicolored Ring Stripes on PEO Spherulites

用自然白光代替偏振光在显微镜下观察聚氧乙烯球晶的生长过程,可以更清晰地看到彩色环形条纹的形成.当成长中的二维球晶相互碰撞后,被挤出的熔体改变球晶的原有结晶方向,流向饼形球晶中央而在其表面上逆向结晶,由于被挤出的熔体数量有限,晶层的厚度逐渐减小,在盖玻片下方形成一个盘状的楔形真空间隙.此间隙导致彩色环状干涉条纹的形成.实验用肉眼直接观察到二维球晶在生长过程中结晶方式的变化,为二次结晶理论的发展提供了实验依据.

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 dearly 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.