Atomic Force Microscopy Characterization and Interpretation of Thin‐Film Poly(butylene adipate) Spherulites with Ring Bands

Frömsdorf, Andreas; Woo, Eamor M.; Lee, Li‐Ting; Chen, Yu-Fan; Förster, Stephan

doi:10.1002/marc.200800246

Cited by 35 publications

(30 citation statements)

References 26 publications

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“…Crystallization temperature 30 °C was selected because at this T c , all neat and blend systems were in mixed α − and β −crystal polymorphic form region, and the regular ring‐banded spherulites are formed in neat and 95/5 blend, and only one type of spherulites (dendritic spherulites) observed in 90/10 and 80/20 blends (to reduce the complexity). AFM micrograph of ring‐banded spherulite in neat PBA, as already reported in previous publication,23 are composed of alternating stalk lamellae (edge‐on) and platelet lamellae (flat‐on). The band spacing of this neat ring‐banded spherulite is about 5–6 μm.…”

Section: Resultssupporting

confidence: 57%

Crystal Polymorphism and Spherulites in Poly(butylene adipate) Diluted with Strongly Versus Weakly Interacting Amorphous Polymers

Lugito

Woo

2012

Macro Chemistry & Physics

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Polymorphism and ring‐banded spherulites in poly(butylene adipate) (PBA) diluted with poly(vinyl acetate) (PVAc) or poly(hydroxyether of bisphenol A) (phenoxy) were studied. For neat PBA, polymorphism and ring‐banded spherulites occur at overlapped Tc = 28–31 °C (4 °C range). By comparison, ring bands of crystallized PBA/PVAc blend remain similar to neat PBA; while for PBA/phenoxy blend, ring bands are completely disrupted (revealed by surface AFM phase images), owing to strong interchain interactions between PBA and phenoxy. The results summarily demonstrate that the Tc range for polymorphism becomes much wider (Tc = 19–32 °C) with the addition of the amorphous polymers and reveals the phenomenon of ring bands in PBA is not correlated or attributed to its α+β polymorphism.

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Section: Resultssupporting

confidence: 57%

Crystal Polymorphism and Spherulites in Poly(butylene adipate) Diluted with Strongly Versus Weakly Interacting Amorphous Polymers

Lugito

Woo

2012

Macro Chemistry & Physics

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“…In the past decade, Woo et al [46][47][48] has studied the surface and cross section morphology of banded spherulites in fractured films of various polyesters. Based on these morphology observations, he questioned the mechanism of lamellar twisting in these banded spherulites and proposed the scheme of alternative radial and tangential growth of lamellar crystals.…”

Section: Real Time Atomic Force Microscopy (Afm) Observation Reveals mentioning

confidence: 99%

Organization of Twisting Lamellar Crystals in Birefringent Banded Polymer Spherulites: A Mini-Review

Zhang

et al. 2017

Crystals

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Abstract:In this mini-review, we summarize the evidences of lamellar twisting in the birefringent banded polymer spherulites demonstrated by various characterization techniques, such as polarized optical microscopy, real-time atomic force microscopy, micro-focus wide angle X-ray diffraction, etc. The real-time observation of lamellar growth under atomic force microscopy unveiled the fine details of lamellar twisting and branching in the banded spherulites of poly(R-3-hydroxybutyrate-co-17 mol % R-3-hydroxyhexanoate). Organization of the twisting lamellar crystals in the banded spherulites was revealed as well. The lamellar crystals change the orientation via twisting rather than the macro screw dislocations. In fact, macro screw dislocation provides the mechanism of synchronous twisting of neighboring lamellar crystals. The driving force of lamellar twisting is attributed to the anisotropic and unbalanced surface stresses. Besides molecular chirality, variation of the growth axis and the chemical groups on lamellar surface can change the distribution of the surface stresses, and thus may invert the handedness of lamellar twisting. Thus, based on both experimental results and physical reasoning, the relation between crystal chirality and chemical molecular structures has been suggested, via the bridge of the distribution of surface stresses. The factors affecting band spacing are briefly discussed. Some remaining questions and the perspective of the topic are highlighted.Keywords: banded polymer spherulite; ringed spherulite; lamellar twisting; organization of lamellar crystals; surface stresses; chirality When crystallized from quiescent melt or concentrated solution, polymer chains usually form spherulites consisted of multiple lamellar crystals radiating from the spherulite center. Observed under polarized optical microscope (POM), a spherulite shows the characteristic Maltese-cross extinction. Besides the Maltese cross, some spherulites demonstrate alternative bright and dark bands under POM. These spherulites are termed as banded spherulites or ringed spherulites. The band structure with different light intensities may result from different thicknesses or different birefringences but similar thickness. In the former case, the bands are due to the periodical modulation of sample thickness and there is no variation of refractive index in the spherulite. These nonbirefringent banded spherulites have been observed in some polymer single crystals formed from thin melt films [1] or solutions [2] and are reviewed by Li et al. [3] in this special issue. In the latter case, the birefringent bands can result from the wavy bending growth or twisting growth of crystals. The wavy bands have been reported in sheared liquid crystals [4,5], which do not form spherulites under the condition. In this mini-review, we focus on the birefringent banded spherulites, which consist of synchronously twisted lamellar crystals. The organization of the twisted lamellar crystals in the banded spherulites and the driving force for lamell...

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“…As lamellae assembly can be influenced by many factors, there are of course additional viewpoints that differ. Other researchers propose mechanisms different from the lamellar twisting in expounding the formation of ring‐banded spherulites 6–9. Wang et al6 proposed a non‐linear diffusion process‐induced rhythmic growth mechanism to interpret the concentric ring‐banded structures of poly(ϵ‐caprolactone) (PCL) produced during solvent evaporation, and the nonlinear diffusion process is due to the periodically change in the concentration gradient of the polymer solution.…”

Section: Introductionmentioning

confidence: 99%

Unconventional Non‐birefringent or Birefringent Concentric Ring‐Banded Spherulites in Poly(L‐lactic acid) Thin Films

Nurkhamidah

Woo

2013

Macro Chemistry & Physics

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Unconventional concentric up-and-down bands, differing from the conventional brightextinction or blue/orange bands in other polymers, in poly( L -lactic acid) are found via controlled thin fi lms. Non-birefringent and birefringent concentric banded spherulites are obtained from 350-400 nm and 1800-2000 nm fi lm thicknesses, respectively. Non-birefringent concentric ring-banded spherulites are arranged only by fl at-on lamellae; in contrast, complex combinations of fl at-on, edge-on, and round-shaped lamellae in four transitional zones are present within a single band in the thicker fi lms of birefringent, concentric, ring-banded spherulites. Interband is an optically extinction crevice that segregates two neighboring bands. Unique lamellar arrangements at specifi c T c and thickness confi nement are two factors for the unconventional concentric bands.

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Atomic Force Microscopy Characterization and Interpretation of Thin‐Film Poly(butylene adipate) Spherulites with Ring Bands

Cited by 35 publications

References 26 publications

Crystal Polymorphism and Spherulites in Poly(butylene adipate) Diluted with Strongly Versus Weakly Interacting Amorphous Polymers

Crystal Polymorphism and Spherulites in Poly(butylene adipate) Diluted with Strongly Versus Weakly Interacting Amorphous Polymers

Organization of Twisting Lamellar Crystals in Birefringent Banded Polymer Spherulites: A Mini-Review

Unconventional Non‐birefringent or Birefringent Concentric Ring‐Banded Spherulites in Poly(L‐lactic acid) Thin Films

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