Probing the interior lamellar periodicity and nano-assembly of polymer spherulites via combinatory etching methodology

Physical and chemical degradative effects of etching agents on polymer spherulites have been explored thoroughly to understand the etching mechanism as well as to perceive the polymer crystal structure and assembly. Interior lamellae of an aromatic polyester, poly(trimethylene terephthalate) (PTT), crystallized into a well-defined periodic-birefringent spherulitic structure, are subjected to sequence-assorted etching agents of basic methylamine (MA) vapor, acidic permanganate (KMnO4) reagent, inorganic acids mixture (H2SO4:H3PO4), and organic dichloroacetic acid (DCA). The chemistry involved in reactions between the selected etchants with the polymer spherulites was probed and their synergistic effects on exposing the interior 3D assembly were assessed. The exposed circumferential alignment of rod-like polycrystals interconnected by nanofibrils signifies the hidden interfaces between the lamellae that are assembled in a periodic grating structure to form banded PTT spherulites.