Shear-Induced Concentration Fluctuations in Ultrahigh Molecular Weight Polyethylene Solutions. 1. Observation above the Melting Point

Murase, Hiroki; Kume, Takuji; Hashimoto, Takeji; Ohta, Yasuo; Mizukami, Tohru

doi:10.1021/ma00127a019

Cited by 36 publications

(48 citation statements)

References 4 publications

(4 reference statements)

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“…10a) was quite similar to the online snapshot of the OM image shown in Fig. 10(c) (Murase et al, 1995) in terms of both the size and the shape of individual domains and their spatial distribution. Thus the spatial distribution of the domains is believed to be well conserved in the offline TEM image through the fixation method.…”

Section: Offline Tem Investigationssupporting

confidence: 76%

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Cascading time evolution of dissipative structures leading to unique crystalline textures

Hashimoto

Murase

2015

Int Union Crystallogr J

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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 smalllength-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.

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Section: Offline Tem Investigationssupporting

confidence: 76%

“…The right-half of the OM image (c) shows a contour pattern composed of the isointensity lines of the left-half transmission OM image. The data are based on those given by Murase et al (1995Murase et al ( , 2011.…”

Section: Offline Tem Investigationsmentioning

confidence: 99%

Cascading time evolution of dissipative structures leading to unique crystalline textures

Hashimoto

Murase

2015

Int Union Crystallogr J

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“…10(a), a "butterfly-type" pattern gradually grows after the startup of the flow, and the pattern changes from the butterfly pattern to an elliptic pattern, that is slightly elongated in the flow direction, which is kept during the period when the solution flows. The butterfly pattern was observed in polystyrene solutions by Murase et al 17) and Kume et al 18) when the shear rate was increased above a critical shear rate.…”

Section: Sals Patternsmentioning

confidence: 77%

Flow Property and Micellar Structures in Capillary Flows of Surfactant Solutions

Hashimoto¹,

Turukawa²,

Môri³

2005

J. Soc. Rheol., Jpn

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Flow property, which is expressed by the relation between wall shear stress and apparent shear rate, is examined in the flows of surfactant solutions through various capillaries. Furthermore, small angle light scattering (SALS) experiments are carried out in the flow through a slit cell. In the present experiments, aqueous solutions of Cetyltrimethylammonium bromide (CTAB) and Sodium Salicylate (NaSal) are used. The flow curve has a break point and its slope below the bending point significantly depends on the ratio of salt concentration C S to surfactant concentration C D . From the experiments on the effect of capillary diameter, it is found that eqimolar solution for C D = 0.03M exhibits a remarkable diameter dependence below the break point while the solution for C D = 0.03M and C S /C D = 7.7 exhibits a diameter dependence only in a narrow region at intermediate shear rates. In the SALS experiments the butterfly pattern is observed for C S /C D =1 and the four-fold symmetry pattern for C S /C D = 7.7. The characteristic scattering pattern is destroyed just after the startup of the flow at high shear rates where the flow curves overlaps regardless of salt concentration and length and diameter of capillary. This fact suggests that micellar network structures are broken at the high shear rates.

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“…Their centers of mass are randomly aligned along the z axis as illustrated in part (c 0 ) in row (C) and as actually shown by the OM images in part (c) in row (C) in Figure 3. [15,17,26,27] Rheology exhibits the shear thinning in Regime II and III (Figure 1a). [18,19,21,[28][29][30] The sheared solutions show almost no birefringence up to Regime III ( Figure 1a, 2b), indicating that polymer chains are essentially in relaxed random coils even under the shear flow.…”

Section: Resultsmentioning

confidence: 99%

“…This process is very important to obtain good scattering data. [17] If we omit this process, intense scattering arising from the particles will disturb the genuine light scattering from the semidilute solutions. , M w /M n ¼ 1.06, c/c Ã % 30) in DOP at 21 8C [18] : part a presents viscosity h, birefringence Dn 0 , and form dichroism Dn 00 ; part b presents the normalized integrated scattered intensities parallel (//) and perpendicular (?)…”

Section: Experimental Partmentioning

confidence: 99%

Shear‐Induced Phase Separation of Entangled Polymer Solutions: Formation of Optically Anisotropic Strings as Precursor Structures of Shish‐Kebab

Hashimoto

Murase

Ohta

2009

Macromolecular Symposia

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Summary: Shear-induced structures were investigated for both ultrahigh molecular weight atactic polystyrene (UHMWaPS) and linear polyethylene (UHMWPE) solutions, which were entangled but homogeneous without shear flow, as a function of shear rate ( _ g) or time after a step-up shear flow. For the PE solutions, the shear flow was imposed at 124 8C which is higher than the nominal melting temperature T nm of the solution without shear flow. At sufficiently high shear rates both solutions commonly formed highly optically anisotropic string-like structures which are composed of a series of phase-separated domains interconnected by bundles of stretched chains and aligned along the flow direction. After cessation of the shear flow the string-like structures completely disappeared in the UHMWaPS solution, recovering a homogeneous solution, while the UHMWPE solution exhibited shish-kebab structure. The results reveal a new kinetic pathway for shish-kebab formation for the entangled crystallizable solution sheared at T > T nm which involves first formation of the phaseseparated string-like domains and subsequent crystallization into shish from the bundles of stretched chain and then kebab in the demixed domains composed of essentially random coils.

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Shear-Induced Concentration Fluctuations in Ultrahigh Molecular Weight Polyethylene Solutions. 1. Observation above the Melting Point

Cited by 36 publications

References 4 publications

Cascading time evolution of dissipative structures leading to unique crystalline textures

Cascading time evolution of dissipative structures leading to unique crystalline textures

Flow Property and Micellar Structures in Capillary Flows of Surfactant Solutions

Shear‐Induced Phase Separation of Entangled Polymer Solutions: Formation of Optically Anisotropic Strings as Precursor Structures of Shish‐Kebab

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