Ring‐banded spherulites in poly(pentamethylene terephthalate): A model of waving and spiraling lamellae

Abstract

A new aryl polyester, poly(pentamethylene terephthalate) (PPT) with five methylene groups in the repeat unit, was synthesized. Its multiple‐melting behavior and crystal structure were analyzed with differential scanning calorimetry and wide‐angle X‐ray diffraction. In addition, the spherulitic/lamellar morphology of melt‐crystallized PPT was investigated. Typical Maltese‐cross spherulites (with no rings) were seen in melt‐crystallized PPT at low temperatures (70–90 °C), but ring patterns were seen in PPT crystallized only at temperatures ranging from 100 to 115 °C, whereas rings disappeared with crystallization above 120 °C. The mechanisms of the rings in PPT were explained with several coordinated directional changes (wavy changes, twisting changes, and combinations) in the lamellae during growth. Scanning electron microscopy, in combination with atomic force microscopy, further proved that the ringed spherulites originated from the aggregation of sufficient numbers of edge‐on lamellar crystals; the radial‐growth edge‐on/flat‐on lamellae could be twisted and/or waved to form realistic band patterns. A postulated model properly described a possible origin of the ring bands through combined mechanisms of waving (zigzagging) and twisting (spiraling) of the lamellae during crystallization. Superimposed twisting and/or wavy models during crystallization were examined as examples. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4421–4432, 2004

Origins of periodic bands in polymer spherulites

“…A recent article [29] has just attempted to address the inherent constraint of analyses based on only the top-surface morphology of ring-banded polymers spherulites, which may not suffice in probing the complex issues of interior lamellae assembly accounting for the ring-band patterns. In addition to literature reports on ring-banded spherulites in aliphatic polyesters such as widely studied poly(ethylene adipate) (PEA) [14,22,[30][31][32], many aromatic polyesters are among the most investigated materials for ring-banded spherulites, such as poly(trimethylene terephthalate) (PTT) [33][34][35][36], poly(pentamethylene terephthalate) (PPT) [37,38], poly(octamethylene terephthalate) (POT) [39], poly(nonamethylene terephthalate) (PNT) [40][41][42].…”

Coexisting Straight, Radial, and Banded Lamellae on the Six Corners of Hexagon‐Shaped Spherulites in Poly(l‐Lactide)

“…Some semicrystalline polymers or polymer blends have been reported to form ring‐banded spherulites at specific crystallization conditions . However, the formation of ring‐banded spherulite morphology remains one of the most challenging and complex issues in the field of crystalline polymer morphology.…”

Amorphous-Phase Miscibility and Crystal Phases in Blends of Polymorphic Poly(hexamethylene terephthalate) with Monomorphic Poly(pentamethylene terephthalate)

“…Note that the polymeric chains in the synthesized PHT contain at least 30 repeat units, whose characteristic crystalline morphology and melting peaks are pretty much the same as those in longer-chain PHT. Similarly, poly(pentamethylene terephthalate) (PPT) was also synthesized in-house using two-step polycondensation procedures, 31,32 by starting from 1,5-pantanediol and dimethyl terephthalate with 0.1% butyl titanate as a catalyst. The molecular weight (M w ) and polydispersity index (PDI) measured by gel permeation chromatography (GPC) were 10,700 g/mol and 1.7, respectively.…”

“…Marks are indicated for identifying some of the unitcell diffraction planes for the -form crystal in the neat PPT. 31 Apparently, a few peaks of unit-cell diffraction planes in the PPT constituent may be overlapping with those from PHT in blends, but other distinct and separate diffraction peaks in the PPT constituent also present to distinguish from those of PHT. Thus, the polymorphism of the PHT constituent in the miscible blend state is almost identical to that of the neat PHT, except that the blends also display additional characteristic diffraction peaks of the PPT component.…”

“…PHT is a polymorphic polyester that has been characterized to display as many as three different crystal cells (, , ) depending on thermal and/or solution treatments; [28][29][30] however, by contrast, PPT is packed with only a single type of crystal cell. PPT exhibits distinct banded spherulites; 31 but the PHT forms radial spherulites with Maltese-cross. Thus, it would be of great interest to probe the blends of these two polyesters, not only on phase behavior and miscibility in the amorphous phase of blends but also effect of blending on crystals, spherulites, polymorphism, etc.…”