AFM observation of polyethylene single crystals: selective handedness of screw dislocations in a chair type

Toda, Akihiko; Okamura, Mari; Hikosaka, Masamichi; Nakagawa, Y.

doi:10.1016/s0032-3861(03)00592-5

Cited by 28 publications

(8 citation statements)

References 6 publications

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“…Actually for polyethylene and PVDF, it is known that polymer molecules and their crystal structures are non-chiral, and hence the selection of the handedness of the twisting in their banded spherulites must be introduced by a higher order structure [12], such as the three-dimensional shape of single crystals. As we have pointed out in our recent papers [8,9,13], the consecutive formation of spiral terraces [14] in the chair-type can be one of the candidates to produce the twisting correlation in the banded spherulites of polyethylene and PVDF.…”

Section: Introductionmentioning

confidence: 88%

“…In a previous paper [9], we have examined the morphology by atomic force microscopy (AFM) and reported a successful observation of the three-dimensional shape of single crystals of polyethylene grown from dilute xylene solution by placing the single crystals on a soft substrate of aqueous solution of poly(vinyl alcohol) (PVA). Similar method has been applied by Geil [10] and Ishihara and Imura [11], and the threedimensional shape of polyethylene has been observed by the shadowing contrast with TEM.…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional shape of polyethylene single crystals grown from dilute solutions and from the melt

Toda¹,

Okamura²,

Hikosaka³

et al. 2005

Polymer

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Three-dimensional shape of polyethylene single crystals grown from dilute solutions and from the melt

Toda¹,

Okamura²,

Hikosaka³

et al. 2005

Polymer

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“…This leads to poor cooperative packing of twisting lamellae and probably results in the irregular banded structure at high temperatures. Toda et al [50][51][52] have systematically revealed the role of macro screw dislocations in lamellar branching in the banded polymer spherulites.…”

Section: Organization Of Twisted Lamellae In Banded Spherulitesmentioning

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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“…[11] Figure 1 shows a BF electron micrograph and its corresponding ED pattern of the HDPE single crystal. The strong (hk0) reflections indicate that the single crystal exhibits a perfect crystallographic orientation with the c-axis parallel to the crystal thickness direction, while the a-and b-axes are in the film plane.…”

Section: Resultsmentioning

confidence: 99%

“…It should be pointed out that there exists a dominant central pleat in the crystals along the crystallographic b-axis direction, which is the mark of the collapse of their initial hollow pyramid. [11] In order to clearly illustrate the morphological and crystalline structural changes of the melt recrystallized HDPE single crystals with or without particle coating, a BF electron micrograph and its corresponding ED pattern of the recrystallized HDPE single crystal without Cr or carboncoating is presented in Figure 2. The annealing temperature was 140 8C.…”

Section: Resultsmentioning

confidence: 99%

Surface Fixing Effect of Vacuum Evaporated Particles on Polyethylene Single Crystals

Lu¹,

Yang²

2005

Macromol. Rapid Commun.

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Summary: The recrystallization behavior of high density polyethylene (HDPE) single crystals with vacuum evaporated metal chromium or carbon on their surface has been investigated by transmission electron microscopy (TEM) and electron diffraction (ED) techniques. The results indicate that the particle‐coated HDPE single crystals can retain their single crystal structure after complete melting and subsequent recrystallization, with the heat‐treated temperature as high as 200 °C. This phenomenon is attributed to a surface fixing effect of vacuum evaporated Cr or carbon on the single crystals.A bright‐field electron micrograph and the corresponding electron diffraction pattern of recrystallized Cr‐coated HDPE single crystals.magnified imageA bright‐field electron micrograph and the corresponding electron diffraction pattern of recrystallized Cr‐coated HDPE single crystals.

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AFM observation of polyethylene single crystals: selective handedness of screw dislocations in a chair type

Cited by 28 publications

References 6 publications

Three-dimensional shape of polyethylene single crystals grown from dilute solutions and from the melt

Three-dimensional shape of polyethylene single crystals grown from dilute solutions and from the melt

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

Surface Fixing Effect of Vacuum Evaporated Particles on Polyethylene Single Crystals

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