Polarized microscopic texture of high-birefringence spherulite

Abstract

We found that the spherulite of poly(trimethylene terephthalate) (PTT) has high birefringence and shows vivid interference colors, such as yellow, blue and green, under a polarized microscope without a sensitive tint plate. The birefringence of the PTT spherulite was evaluated to be ca. 0.065 by using the Michel-Levy chart. The extremely large birefringence seems to cause the unique and colorful image under the microscope without the plate. The birefringence in the spherulite was found to increase with increasing a distance from the center of the spherulite, suggesting that ordering in spherulite increases along the radius direction. As the crystallization temperature decreased, the ordering in spherulite increased.