Professor Eamor Woo of the National Cheng Kung University in Taiwan and Siti Nurkhadmidah, now at Institut Teknologi Sepuluh Nopember in Indonesia, report on the formation of both non-birefringent and birefringent concentric ring-banded spherulites in poly(L-lactic acid). The birefringent property depends on the film thickness.
Different lamellar arrangements across the bands influence the nanoscale morphology further.
Different crystal growth rates in the same band induce an asymmetry in the height profiles of the concentric ring-banded spherulites. Lamellar growth is faster in the early stages, slowing down later on. This may be due to the lack of material to crystallize, or in the differential rates of the molten polymer diffusion and the interface’s forward movement.