Twisting of Lamellar Crystals in Poly(3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate) Ring-Banded Spherulites

Wang, Zongbao; Li, Ya; Yang, Jian; Gou, Quting; Yang, Wu; Wu, Xuedong; Liu, Pengbo; Gu, Qun

doi:10.1021/ma902773u

Cited by 59 publications

(54 citation statements)

References 31 publications

(39 reference statements)

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“…Etching of banded polymer spherulites with solvent has been applied to separate the twisting lamellae [41]. The study provided firm support that the banded spherulite consisted of twisting lamellar crystals, while radiating from the spherulite center to the periphery.…”

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

confidence: 89%

“…Since individual twisted lamellar crystals can be isolated from the crystallized samples [41,65], the origin of lamellar twisting should be internal rather than external forces, though the external fields during lamellar growth may affect lamellar twisting to some extent. In addition, the external fields could not guarantee the fixed handedness of twisting during lamellar growth.…”

Section: Driving Force For Lamellar Twisting In Banded Polymer Spherumentioning

confidence: 99%

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

confidence: 89%

Section: Driving Force For Lamellar Twisting In Banded Polymer Spherumentioning

confidence: 99%

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

Zhang

et al. 2017

Crystals

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“…Wang et al [47] even discussed evidence of twisting lamellae in poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) by methylamine-vapor etching on crystallized lamellae. Several other investigators also used methylamine as an etchant to expose the lamellae behind the polymer banded spherulites without considering the chemical reactivity of methylamine with the polymer itself.…”

Section: Chemical Etchingmentioning

confidence: 99%

“…Etching methods are long known to be effective in exposing the crystal assembly in contrast to amorphous domains in bulk polymer samples [6,7,47,48], although some chemical reaction during etching is sometimes inevitable [48,49]. Severe chemical changes or deformation of crystal shapes, however, must be cautioned against, as otherwise, interpretation of crystal morphology based on etched samples might be misleading.…”

Section: Etching Effects On Distortion Of Lamellae In Ptt Banded Sphementioning

confidence: 99%

Interior Lamellar Assembly and Optical Birefringence in Poly(trimethylene terephthalate) Spherulites: Mechanisms from Past to Present

2017

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Poly(trimethylene terephthalate) (PTT) with its unique spherulitic morphologies, highly birefringent features, and crystal stability serves as a good candidate to study polymer crystallization and assembly. This review compiles the main findings on crystallization in PTT, including birefringence and morphology, thermal behavior, as well as the interior structure of PTT banded spherulites, in order to elucidate the origin and formation mechanism of banded spherulites. Interior observation through the inner anatomy of crystal assembly in banded spherulites hidden under the top surface is necessary to provide a complete picture for the unsettled arguments about formation mechanism. Careful attention should be taken when selecting the etching agent for exposing the lamellar structure of polymer spherulite, otherwise, misinterpretation could result.

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“…The mechanical properties of PLLA/PEO blends determine their broader applications. 32,33,42,43 It is reasonable to expect that the Izod impact toughness of PLLA is enhanced by the blending. In addition, the mechanical properties of PLLA have been This is the Pre-Published Version demonstrated to be significantly affected by its morphology, which is strongly controlled by the processing parameters.…”

Section: Introductionmentioning

confidence: 99%

The relationship between morphology and impact toughness of poly(l-lactic acid)/poly(ethylene oxide) blends

Schultz

Chan

2015

Polymer

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Twisting of Lamellar Crystals in Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Ring-Banded Spherulites

Cited by 59 publications

References 31 publications

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

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

Interior Lamellar Assembly and Optical Birefringence in Poly(trimethylene terephthalate) Spherulites: Mechanisms from Past to Present

The relationship between morphology and impact toughness of poly(l-lactic acid)/poly(ethylene oxide) blends

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