Twisting orientation and the role of transient states in polymer crystallization

Keith, H. D.; Padden, F. J.

doi:10.1016/0032-3861(84)90264-7

Cited by 329 publications

(323 citation statements)

References 30 publications

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“…It is believed to arise from cooperative twisting of radiating lamellar crystals about their axis of fastest growth due to stress accumulation. 101,[104][105][106] These stresses shall arise from irregular chain folding at the fold surfaces of a lamella, which in their turn are caused by growth that is fast with respect to the creation and arrangement of folds. The stresses may also be linked with chain tilt at the lamellar surfaces such pointing in opposite directions at the two faces.…”

Section: Crystallization and Growth Of Pvdfmentioning

confidence: 99%

Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

Liu

Jungnickel

2007

J Polym Sci B Polym Phys

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A survey is presented on the crystallization kinetics and the morphology of miscible crystalline/crystalline polymer blends. There are only few corresponding systems. In them, however, a number of strange kinetic and structural phenomena can be observed: (i) spherulitic crystallization of the components side‐by‐side, (ii) “interpenetrating crystallization,” (iii) “interlocking spherulitic crystallization,” and (iv) “interfilling crystallization.” Cocrystallization is forbidden for crystallographic reasons. The blend partners grow instead in their own lamellar stacks, and mixed lamellar stacks are a seldom and questionable exception. They crystallize also usually stepwise and not simultaneously. Upon step crystallization, the crystallization of the second component is determined by its redistribution with crystallization of the former. Those composition inhomogeneities are an independent issue that arises also with the development of the morphology in crystalline/amorphous blends, and a corresponding survey is yielded, too. The blend poly (vinylidene fluoride)/poly‐β‐hydroxybutyrate is a convenient model system as it can show all of these morphological and kinetic features after suitable thermal treatment. Some of them are demonstrated in the present publication. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1917–1931, 2007

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Section: Crystallization and Growth Of Pvdfmentioning

confidence: 99%

Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

Liu

Jungnickel

2007

J Polym Sci B Polym Phys

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“…Excepting the successful manipulation between uniform flat-on and random orientations, the periodic variation of radial lamellar orientation, e.g., lamellar twisting, cannot happen. For the origins of periodic twisting of polymer lamellae, the most acceptable model should belong to that advocated by Keith and Padden [51][52][53]. They suggested that the periodic twisting is a consequence of the unbalanced stresses on opposite fold surfaces originating from the significantly different overcrowding and inefficient packing in the fast-growing lamellae [51].…”

Section: Modulating the Periodic Orienatation Of Radial Lamellae To Pmentioning

confidence: 99%

“…For the origins of periodic twisting of polymer lamellae, the most acceptable model should belong to that advocated by Keith and Padden [51][52][53]. They suggested that the periodic twisting is a consequence of the unbalanced stresses on opposite fold surfaces originating from the significantly different overcrowding and inefficient packing in the fast-growing lamellae [51]. According to this theory, it is reasonable that the disorder can be intensified with the increase of both the molecular weight and crystallization rate which is, therefore, expected to promote the twisting of lamellae [53].…”

Section: Modulating the Periodic Orienatation Of Radial Lamellae To Pmentioning

confidence: 99%

Morphological Control of Polymer Spherulites via Manipulating Radial Lamellar Organization upon Evaporative Crystallization: A Mini Review

Wang

2017

Crystals

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Abstract:Various spherulites or spherulitic crystals are widely encountered in polymeric materials when crystallized from viscous melts or concentrated solutions. However, the microstructures and growth processes are quite complicated and remain unclear and, thus, the formation mechanisms are rather elusive. Here, diverse kinds of spherulitic growths and patterns of typical polyesters via evaporative crystallization of solution-cast thin films are delineated after detailed investigating the microstructures and in situ following the developing processes. The spherulitic crystals produced under different evaporation conditions reflect variously optical features, such as the usual Maltese Cross, non-birefringent or half-birefringent concentric-rings, extinction spiral banding, and even a nested ring-banded pattern. Polymer spherulites are composed of stacks of radial fibrillar lamellae, and the diversity of bewitchingly spherulitic morphologies is dominated by the arrangement and organization of radial lamellae, which is predicted to be tunable by modulating the evaporative crystallization processes. The emergence of various types of spherulitic morphologies of the same polymer is attributed to a precise manipulation of the radial lamellar organization by a coupling of structural features and specific crystal evolving courses under confined evaporation environments. The present findings improve dramatically the understanding of the structural development and crystallization mechanism for emergence of diverse polymer spherulitic morphologies.

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“…It can be seen that the periodic distance and the gray distance of the extinction rings increase with crystallization temperature; however, the white distance of the extinction rings decreases with the crystallization temperature. The most comprehensive study on the ring-banded spherulite structures in homopolymers such as polyethylene has been published by Keith and Padden [24]. The proposed basic mechanism leading to the ring pattern is axial twisting in lamellae under the influence of surface stress, and cooperative arrangement of twisted crystallites.…”

Section: Crystallization Morphology and Ring-banded Spherulite Of Peomentioning

confidence: 99%

“…[20] Banding in polymer spherulites, i.e., the presence of radially periodic structure attributable to a twisting of crystallographic orientation about radii that usually give rise to concentric rings or bands of extinction in polarized light microscopy, is a common occurrence and has been studied for more than a century [21]. Banding in polymer spherulites is currently generating renewed interest [21][22][23][24][25][26][27]. The banded spherulites that evince a twisting of crystalline orientation about the radii are common in both circumstances and, although occurrence is still quite rare, polymer of both kinds are also found in the form of isolated twisted crystals having roughly the form of right helicoids [21].…”

Section: Introductionmentioning

confidence: 99%

Crystallization Behaviors and Structure Transitions of Biocompatible and Biodegradable Diblock Copolymers

Xue

Jiang

2014

Polymers

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Biocompatible and biodegradable block copolymers (BBCPs) containing crystalline blocks become increasingly important in polymer science, and have great potential applications in polymer materials. Crystallization in polymers is accompanied by the adoption of an extended conformation, or often by chain folding. It is important to distinguish between crystallization in homopolymers and in block copolymers. In homopolymers, chain folding leads to metastable structures introduced by the crystallization kinetics. In contrast, equilibrium chain folding in diblocks can be achieved as the equilibrium number of the folds is controlled by the size of the second block. The structures of BBCPs, which are determined by the competition between crystallization, microphase separation, kinetics and processing, have a tremendous influence on the final properties and applications. In this review, we present the recent advances on crystalline-crystalline diblock copolymer in our group.

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Twisting orientation and the role of transient states in polymer crystallization

Cited by 329 publications

References 30 publications

Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

Morphological Control of Polymer Spherulites via Manipulating Radial Lamellar Organization upon Evaporative Crystallization: A Mini Review

Crystallization Behaviors and Structure Transitions of Biocompatible and Biodegradable Diblock Copolymers

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