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Cascading time evolution of dissipative structures leading to unique crystalline textures.

Hashimoto T, Murase H - IUCrJ (2015)

Bottom Line: The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields.The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures.Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

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Affiliation: Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan ; Quantum Beam Science Directorate, Japan Atomic Energy Agency , Tokai-mura, Ibaraki, 1319-1195, Japan ; Professor Emeritus, Kyoto University , Kyoto, 606-8501, Japan.

ABSTRACT
This article reports unique pattern formation processes and mechanisms via crystallization of materials under external flow fields as one of the general problems of open nonequilibrium phenomena in statistical physics. The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields. The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures. Moreover, this cascading pattern evolution obeys the Ginzburg-Landau law. It first evolves a series of large-length-scale amorphous precursors driven by liquid-liquid phase separation under a relatively low bulk stress and then small-length-scale structures driven by a large local stress concentrated on the heterogeneous amorphous precursors, eventually leading to the formation of unique crystalline textures which cannot be developed free from the external fields. Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

No MeSH data available.


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Cascading pattern formation from homogeneous polymer solutions to the SKs via the flow-induced formation of dissipative structures 1–4, following the free energy landscape D1, and cascading pattern formation from the SK to the ECCs via the hot-drawing-induced dissipative structures 5 and 6, following the free energy landscape D2. 1 is the PLWCF, 2 is the randomly arranged demixed domains, 3 is the optically isotropic strings, 4 is the optically anisotropic strings, 5 and 6 are the SK having a kebab fraction reduced stepwise and increased shish length. The barriers A and B illustrate the free energy barrier in the absence of the external fields from the homogeneous polymer solutions to ECC or to SK, respectively, while the barrier C illustrates that from SK to ECC. The barriers A to C are anticipated to be extremely large, because the corresponding patterns were never observed in the absence of the external fields.
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fig15: Cascading pattern formation from homogeneous polymer solutions to the SKs via the flow-induced formation of dissipative structures 1–4, following the free energy landscape D1, and cascading pattern formation from the SK to the ECCs via the hot-drawing-induced dissipative structures 5 and 6, following the free energy landscape D2. 1 is the PLWCF, 2 is the randomly arranged demixed domains, 3 is the optically isotropic strings, 4 is the optically anisotropic strings, 5 and 6 are the SK having a kebab fraction reduced stepwise and increased shish length. The barriers A and B illustrate the free energy barrier in the absence of the external fields from the homogeneous polymer solutions to ECC or to SK, respectively, while the barrier C illustrates that from SK to ECC. The barriers A to C are anticipated to be extremely large, because the corresponding patterns were never observed in the absence of the external fields.

Mentions: On the basis of experimental results and the discussion presented in §4.2.1 and §4.2.2, we now propose a concept of the cascading time evolutions of a series of dissipative structures into SKs dispersed in solvent, starting from a homogeneous solution composed of entangled random coils of polymers swollen with solvent, as shown in Fig. 15 ▶. The exceedingly high free energy barrier B encountered by the crystallization of random-coil chains in the homogeneous solution into the SK in the absence of an applied field will be stepwise suppressed as shown by the free energy landscape D1 under the applied fields via the cascading evolution of a series of the dissipative structures 1–4 as experimentally clarified in §4.2.1 and §4.2.2. The structures 1–3 are the amorphous precursors for the SK which is driven by the flow-induced L–L phase separation inherent in the dynamically asymmetric systems, while structure 4 is the crystalline precursor for the SK driven by the special crystallization process already elucidated in §4.2.2 (e) and to be further discussed in §5.4. The hypothesis about the free energy landscape D1 has not been theoretically proven yet, and an exploration of it deserves further work.


Cascading time evolution of dissipative structures leading to unique crystalline textures.

Hashimoto T, Murase H - IUCrJ (2015)

Cascading pattern formation from homogeneous polymer solutions to the SKs via the flow-induced formation of dissipative structures 1–4, following the free energy landscape D1, and cascading pattern formation from the SK to the ECCs via the hot-drawing-induced dissipative structures 5 and 6, following the free energy landscape D2. 1 is the PLWCF, 2 is the randomly arranged demixed domains, 3 is the optically isotropic strings, 4 is the optically anisotropic strings, 5 and 6 are the SK having a kebab fraction reduced stepwise and increased shish length. The barriers A and B illustrate the free energy barrier in the absence of the external fields from the homogeneous polymer solutions to ECC or to SK, respectively, while the barrier C illustrates that from SK to ECC. The barriers A to C are anticipated to be extremely large, because the corresponding patterns were never observed in the absence of the external fields.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4285881&req=5

fig15: Cascading pattern formation from homogeneous polymer solutions to the SKs via the flow-induced formation of dissipative structures 1–4, following the free energy landscape D1, and cascading pattern formation from the SK to the ECCs via the hot-drawing-induced dissipative structures 5 and 6, following the free energy landscape D2. 1 is the PLWCF, 2 is the randomly arranged demixed domains, 3 is the optically isotropic strings, 4 is the optically anisotropic strings, 5 and 6 are the SK having a kebab fraction reduced stepwise and increased shish length. The barriers A and B illustrate the free energy barrier in the absence of the external fields from the homogeneous polymer solutions to ECC or to SK, respectively, while the barrier C illustrates that from SK to ECC. The barriers A to C are anticipated to be extremely large, because the corresponding patterns were never observed in the absence of the external fields.
Mentions: On the basis of experimental results and the discussion presented in §4.2.1 and §4.2.2, we now propose a concept of the cascading time evolutions of a series of dissipative structures into SKs dispersed in solvent, starting from a homogeneous solution composed of entangled random coils of polymers swollen with solvent, as shown in Fig. 15 ▶. The exceedingly high free energy barrier B encountered by the crystallization of random-coil chains in the homogeneous solution into the SK in the absence of an applied field will be stepwise suppressed as shown by the free energy landscape D1 under the applied fields via the cascading evolution of a series of the dissipative structures 1–4 as experimentally clarified in §4.2.1 and §4.2.2. The structures 1–3 are the amorphous precursors for the SK which is driven by the flow-induced L–L phase separation inherent in the dynamically asymmetric systems, while structure 4 is the crystalline precursor for the SK driven by the special crystallization process already elucidated in §4.2.2 (e) and to be further discussed in §5.4. The hypothesis about the free energy landscape D1 has not been theoretically proven yet, and an exploration of it deserves further work.

Bottom Line: The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields.The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures.Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan ; Quantum Beam Science Directorate, Japan Atomic Energy Agency , Tokai-mura, Ibaraki, 1319-1195, Japan ; Professor Emeritus, Kyoto University , Kyoto, 606-8501, Japan.

ABSTRACT
This article reports unique pattern formation processes and mechanisms via crystallization of materials under external flow fields as one of the general problems of open nonequilibrium phenomena in statistical physics. The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields. The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures. Moreover, this cascading pattern evolution obeys the Ginzburg-Landau law. It first evolves a series of large-length-scale amorphous precursors driven by liquid-liquid phase separation under a relatively low bulk stress and then small-length-scale structures driven by a large local stress concentrated on the heterogeneous amorphous precursors, eventually leading to the formation of unique crystalline textures which cannot be developed free from the external fields. Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

No MeSH data available.


Related in: MedlinePlus