Formation of Periodically Modulated Polymer Crystals

Poudel, Purushottam; Majumder, S. B.; Chandran, Sivasurender; Zhang, Hui; Reiter, Günter

doi:10.1021/acs.macromol.8b01366

Cited by 20 publications

(32 citation statements)

References 50 publications

(84 reference statements)

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“…(a). Simultaneously, as T C increases, the crystal growth rate decreases, accompanied by an increase in detachment probability of polymers at the crystal growth front and a small increase of the diffusion coefficient of the detached and molten polymers . In our experiments, we observed stacks containing a large number of correlated crystalline lamellae only for T C near the melting temperature.…”

Section: Resultsmentioning

confidence: 47%

“…Although these nuclei were not all formed at the same time, they were correlated nonetheless with respect to their orientation because they were all initiated through the basal lamella. Additionally, the same self‐induced nucleation mechanism was found to propagate into subsequent higher‐level lamellae, producing a stack of uniquely oriented lamellae . The nucleation probability through self‐induced nucleation can be much higher than homogeneous nucleation from an equilibrated melt but depends on the type of polymer used.…”

Section: Introductionmentioning

confidence: 90%

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A nucleation mechanism leading to stacking of lamellar crystals in polymer thin films

Majumder

Poudel

Zhang

et al. 2019

Polymer International

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Systematic studies based on well-controllable model systems aim at understanding how crystallization from a melt or solution of randomly coiled polymers leads to the formation of mono-lamellar crystals. However, besides mono-lamellar crystals also various other morphologically simple but yet not well understood structures are found. In particular, stacks of correlated lamellar crystals have been observed since the early days of the study of polymer crystallization. Here, we demonstrate that a recently proposed mechanism of self-induced nucleation within lamellar crystals provides a possibility to explain how in such stacks lamellar crystals can be correlated. Examining various polymer systems, we show that the probability for generating self-induced nuclei depends on the morphology of an initiating dendritic basal lamellar crystal. In addition, we provide evidence that this self-induced nucleation mechanism, together with a high rate of transport of molten polymer to the fold surface, may allow the formation of polymer crystals with similar size in all three dimensions, containing a large number of superposed correlated lamellae.

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Section: Resultsmentioning

confidence: 47%

Section: Introductionmentioning

confidence: 90%

A nucleation mechanism leading to stacking of lamellar crystals in polymer thin films

Majumder

Poudel

Zhang

et al. 2019

Polymer International

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“…For very thin film, one‐layer single crystals are usually observed. At large undercooling, each single crystal shows a spherical shape, indicating no preference of the sites of secondary nucleation 116 . In contrast, at low undercooling, the single crystal is hexagonal, with the six corners preferred for secondary nucleation.…”

Section: Interplay Of Different Kinetic Processesmentioning

confidence: 95%

“…The probability of self‐induced nucleation is much lower than that of the secondary nucleation. The competition of lamellar growth, self‐induced nucleation (or in other cases macro screw dislocations) and chain diffusion leads to formation of non‐birefringent banded spherulites caused by the periodical variation of the number of layers of the single crystals 114,116–119 . The formation of such non‐birefringent banded spherulites has been summarized in a review 120 .…”

Section: Interplay Of Different Kinetic Processesmentioning

confidence: 99%

Secondary nucleation in polymer crystallization: A kinetic view

Zhang

Wang

Guo

et al. 2021

Polymer Crystallization

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Secondary nucleation on the surfaces of growing crystals plays a vital role in polymer crystallization, which determines the lamellar thickness at growth front and the radial growth rate. Though secondary nucleation has been intensively studied in the past decades, our understanding on the molecular mechanism and kinetics is not yet complete. In this perspective, we will briefly review the major advances in the secondary nucleation of flexible polymer chains in the past decade and discuss some remained questions from a viewpoint of kinetics. The main theories, thermodynamics and kinetics of secondary nucleation are first summarized. The difference of nucleation of polymer chains from that of small molecular crystals is revealed via analysis of kinetics. Then, the interplay of various microscopic processes leading to the final crystalline structures is discussed, such as lamellar thickening versus widening, intra‐chain vs inter‐chain nucleation, secondary nucleation versus lateral spreading, secondary vs primary nucleation, nucleation of polymorphisms, and so forth. Finally, some remained open questions are highlighted. Combining kinetic theory considering various microscopic processes and new experimental evidences at different length and time scales would greatly help deepen our understanding on the secondary nucleation during crystallization of flexible polymer chains.

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“…[ 37–40 ] The self‐induced nucleation of the stacked lamellae was extended to the ring bands. [ 36,43,44 ] At the same time, this self‐induced nucleation of the stacked lamellae generated the structural discontinuity in banded rings. [ 36,45 ] Wavy growth rate was observed in banded spherulite with periodic intervals; in the beginning stage, the thin lamellae layer nucleated at a fast growth rate, and it was gradually slowed down when it reaches the maximum thickness.…”

Section: Introductionmentioning

confidence: 99%

Lamellar Assembly Mechanism on Dendritic Ring‐Banded Spherulites of Poly(ε‐caprolactone)

Nagarajan

2021

Macromol. Rapid Commun.

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The self‐assembly structures of lamellae in optical ring bands have a critical effect on their optical and physical arrangements. Two different types of dendritic banded spherulites (namely ring‐banded and zigzag ring‐banded) are formed in poly(ε‐caprolactone)/poly (phenyl methacrylate) blend at crystallization temperatures of 42 and 46 °C, respectively. The difference in optical birefringence of ring bands in two types of spherulites is resolved by means of direct morphological comparison. Banded spherulites are fractured carefully to facilitate lamellar orientation analyses of both the top surface and the interior surface. The results have revealed the existence of tree‐like dendritic fractal growth lamellar assemblies in both banded spherulites. The optical ring patterns of the banded spherulites are differentiated mainly by the fractal orientation of the edge‐on crystal branches in the ridge region. On the basis of detailed morphological analysis, 3D‐lamellar assembly mechanisms are proposed to explain the growth of dendritic ring‐banded spherulites at 42 °C and dendritic zigzag ring‐banded spherulites at 46 °C.

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Formation of Periodically Modulated Polymer Crystals

Cited by 20 publications

References 50 publications

A nucleation mechanism leading to stacking of lamellar crystals in polymer thin films

A nucleation mechanism leading to stacking of lamellar crystals in polymer thin films

Secondary nucleation in polymer crystallization: A kinetic view

Lamellar Assembly Mechanism on Dendritic Ring‐Banded Spherulites of Poly(ε‐caprolactone)

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