From Nano-Crystals to Periodically Aggregated Assembly in Arylate Polyesters—Continuous Helicoid or Discrete Cross-Hatch Grating?

Abstract

This work used several model arylate polymers with the number of methylene segment n = 3, 9, 10, and 12, which all crystallized to display similar types of periodically banded spherulites at various Tc and kinetic factors. Universal mechanisms of nano- to microscale crystal-by-crystal self-assembly to final periodic aggregates showing alternate birefringence rings were probed via 3D dissection. The fractured interiors of the birefringent-banded poly(decamethylene terephthalate) (PDT) spherulites at Tc = 90 °C revealed multi-shell spheroid bands composed of perpendicularly intersecting lamellae bundles, where each shell (measuring 4 μm) was composed of the interior tangential and radial lamellae, as revealed in the SEM results, and its shell thickness was equal to the optical inter-band spacing (4 μm). The radial-oriented lamellae were at a roughly 90° angle perpendicularly intersecting with the tangential ones; therefore, the top-surface valley band region appeared to be a submerged “U-shape”, where the interior radial lamellae were located directly underneath. Furthermore, the universal self-assembly was proved by collective analyses on the three arylate polymers.

Iridescent Features Correlating with Periodic Assemblies in Custom-Crystallized Arylate Polyesters

“…Similar to the work on PTT or other polyesters, an earlier analysis of the top surface and internal analysis perspectives of neat PDT (10 methylene segments in chemical repeat unit) crystallized at T c = 80-95 • C has been described by Yang et al [60]. The ring-banded PDT spherulites are composed of cyclic patterns of a protruded ridge and a flat-plane untextured valley area, as viewed from the top surface.…”

Coherence in Polycrystalline Thin Films of Twisted Molecular Crystals

“…Linear retardance (LR) is the path difference gained by orthogonal polarization modes vibrating in anisotropic crystals that is proportional to the intrinsic difference in refractive activity, as well as the path length. Woo et al observed that spherulites with incoherent twisted fibers have lower LR compared to spherulites with coherent fibers. , In other words, coherent fibers better approximate the LR of a single crystal. Here, we measured LR for twisted coumarin crystals with different boundary incoherence using Mueller matrix microscopy (Supporting Information).…”

“…Woo et al observed that spherulites with incoherent twisted fibers have lower LR compared to spherulites with coherent fibers. 25 , 26 In other words, coherent fibers better approximate the LR of a single crystal. Here, we measured LR for twisted coumarin crystals with different boundary incoherence using Mueller matrix microscopy ( Supporting Information ).…”

“…Due to the anisotropy of crystal cross section shape and branching frequency, twisting substantially complicates fiber organization in spherulites. Previously efforts to account for emergent complexity have relied on microstructural analyses of the 3D arrangements of twisted lamellae in polymer spherulites. − A more global analysis emphasized here relies on polarization-dependent optical properties. For instance, circular birefringence measurements of banded spherulites indicate that the adjacent twisted lamellae with anisotropic cross sections cannot grow parallel to each other due to the space constraints in films crystallized between two glass slides.…”

Editorial of Special Issue “Functional Nanomaterials Based on Self-Assembly”

“…Prof. Woo and colleagues [9] studied the self-assembly of model arylate polyester polymers with different numbers of methylene segments (n = 3, 9, 10, and 12) in solid state. These polymers crystallized depending on the conditions as similar types of periodically banded spherulites.…”