Spiral-Stacked Crystal Assembly Leading to Intensified Iridescence in Poly(trimethylene terephthalate)

Abstract

Poly(trimethylene terephthalate) (PTT) is used as an ideal model to study the correlation between the interior 3D assembly and surface banding topology subjected to various etching methods (physical and chemical) for enhancing the contrast of crystal arrangements in three-dimensional perspective. Narrow crystal shells are sandwiched between crevices on the successive bands in chemically etched PTT and the gap between the successive crystal bands exposed in physically etched PTT further strengthens the evidence of inter-band discontinuity of growth in the radial direction. Spiral-spin assembly with periodic conical banded aggregates is proved, where periodicity starts from a core nucleus with an initial geometry guiding the formation of different types of banded crystals. Intensified iridescence due to the orderly lamellar stacking is unique.