Unusual Ringed/Dendritic Sector Faces in Poly(butylene succinate) Crystallized with Isomeric Polymer

Abstract

Poly­(butylene succinate) (PBSu) and poly­(ethylene adipate) (PEA), isomeric to each other, are mixed in a miscible state, and PBSu crystallized at T c’s where PEA is kept at a molten state. PBSu upon crystallization in the presence of isomeric PEA at various Tc’s develops sector-face spherulitic patterns, which are shown to originate from a common nuclei center. The two faces of sector-face PBSu spherulites are more strikingly contrast when PBSu is highly diluted by isomeric PEA in PBSu/PEA mixtures (PEA = 70–80%) and crystallized at intermediate T c = 50–60 °C. The main characteristics of crystallized PBSu and lamellar assembly mechanisms in these two faces were investigated using POM, SEM, AFM, and DSC. For both faces (ring-banded vs dendritic) of the sector-face PBSu spherulites, the lamellar assembly mechanism differs, but the growth is similar by repeating with periodic multiplication of fractal branches (whose number is proportional to square of radius) in the next cycle; thus, the lamellae fractal branches not only able to interpret the periodic optical banding but also account for filling the expanding spherulite. This growth mechanism is readily accounted by many fractal patterns in the nature.

Crystal-by-Crystal Assembly in Two Types of Periodically Banded Aggregates of Poly(p-Dioxanone)

“…Packing and maturing into multiple (or dual) types of spherulites may be related to nucleation instability, where the initial geometry of nucleus/nuclei (or bundled sheaves) serves as a determining factor for guiding the later lamellae to grow and assemble. In several other polymers, it has been also found that dual or multiple types of spherulites co-exist due to the instability of the initial nucleus, as documented in several literature papers [ 45 , 46 ].…”

Microscopic and Small-/Wide-Angle Microbeam X-ray Analyses on Dendritic Crystals in Poly(butylene succinate)

“…37 Furthermore, the kinetic growth of spherulites is one of the most important factors affecting the final morphology. 38 Common morphologies of crystal aggregates include ringless spherulites, 39 ring-banded spherulites, 40 dendritic spherulites, 41 and many other special morphologies such as feather-like spherulites, 42 seaweed-like spherulites, 37 ring-banded with an eye-like region, 43 dendritic sector-face spherulites, 44 and flower-petal like ring bands, 45 nd so forth. Recently, Wu, et al 46 diluted poly(hydroxybutyrate-cohydroxyvalerate) (with valerate unit = 8−12%) with lowmelting poly(trimethylene adipate), and reported that ringbanded spherulites were observed under a polarized light microscope, with alternate blue/orange-color rings on spherulites.…”

Unique Periodic Rings Composed of Fractal-Growth Dendritic Branching in Poly(p-dioxanone)

“…By adjusting the ratio of the polymers and crystallization temperature, many polymer blends exhibit diverse crystallization morphologies, such as Maltese cross spherulites, ring-banded spherulites, dendritic spherulites, hexagonal spherulites [ 1 ], feather-like spherulites [ 2 ], seaweed spherulites [ 3 ], and the unique Janus-face spherulites [ 4 , 5 ]. However, in recent decades, the formation mechanism of periodic ring-banded spherulites was interpreted controversially.…”