Shear stabilization of critical fluctuations in bulk polymer blends studied by small angle neutron scattering

Nakatani, Alan I.; Kim, Hongdoo; Takahashi, Yoshiaki; Matsushita, Yushu; Takano, Atsushi; Bauer, Barry J.; Han, Charles C.

doi:10.1063/1.459533

Cited by 75 publications

(30 citation statements)

References 50 publications

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“…The behavior of polymer blends under shear flow has recently been a subject of considerable interest from both the view point of theoretical research and industrial application because shear field is unavoidable in many polymer‐processing steps such as injection and extrusion moldings. Recent studies1–15 of polymer blends under shear field have shown the existence of shear‐induced mixing (SIM) and demixing (SID). Lyngaae‐Jorgensen and Sondergaard4, 5 found that in poly(methyl methacrylate) (PMMA)/poly(styrene‐co‐acrylonitrile) (SAN) at a critical shear rate, a light scattering pattern disappeared and SIM existed.…”

Section: Introductionmentioning

confidence: 99%

“…For polystyrene/polyvinyl methyl ether (PS/PVME), one of the extensively investigated polymer blends,3, 6–8, 11–15 it has been known that the phenomena of mixing, demixing, and two cloud points could occur under shear according to the applied shear rate and the experimental temperature. Mazich and Carr3 first reported that in a PS/PVME binary blend, shear flow increased the lower critical solution temperature (LCST) of the blend by 2–7 K. In their experiments, the abrupt change in the slope of the viscosity curve verse temperature was interpreted as an indication of the phase‐transition point.…”

Section: Introductionmentioning

confidence: 99%

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Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

Lei¹,

Li²,

Yang³

et al. 2003

J Polym Sci B Polym Phys

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The phase behavior and phase‐separation dynamics of polystyrene/polyvinyl methyl ether (PS/PVME) blend with a critical composition of 70 vol % PVME were examined with a light scattering technique under a shear‐rate range of 0.1–40 s−1. If the shear rates were less than 8 s−1 and the starting temperatures of the measurement were 343 and 383 K, respectively, two cloud points were observed, whereas after the shear rate was higher than 8 s−1, only one cloud point existed, 20 K higher than that of the static state of the blend. Investigation of the phase‐separation dynamics at 443 K suggested that in the vorticity direction the phase‐separation behavior at the early stage and the later stage can be explained by Cahn–Hilliard linearized theory and the exponent growth law, respectively. Phase separation occurs after a shearing time, which was called a delay time τd. The delayed time τd, the apparent diffusion coefficient, and the exponent term of the blend show strong dependence on shear rates. A theoretical prediction of the phase behavior of PS/PVME under a shear flow field by introducing an elastic energy term into Flory's equation‐of‐state theory was made, and the prediction was consistent with the experimental results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 661–669, 2003

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

Lei¹,

Li²,

Yang³

et al. 2003

J Polym Sci B Polym Phys

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“…In miscible blends, flow can affect the phase equilibrium; that is, it can change the phase diagram of the system 1. Although most of the studies indicate flow‐induced miscibility for such systems,2, 3 some researchers observed the opposite effect, flow‐induced demixing 4. Flow can also change the morphology of the polymer blends, causing breakup or coalescence of the dispersed‐phase droplets 5…”

Section: Introductionmentioning

confidence: 99%

“…A design by Keates et al7 was used to study structural changes in solutions of hydroxypropyl cellulose during flow with X‐ray scattering. A small‐angle neutron scattering instrument at the National Institute of Standards and Technology was used to study concentration fluctuations in polymer blends near their critical solubility temperature3 and to study shear‐induced order–disorder transitions in block copolymers 8. The size of the features that can be detected by neutron and X‐ray scattering is much smaller than that detectable by light scattering, which makes these techniques particularly attractive for certain applications.…”

Section: Introductionmentioning

confidence: 99%

In‐line monitoring of immiscible polymer blends in a rheometer with a fiber‐optics‐assisted fluorescence detection system

Vorobyova

Winnik

2001

J Polym Sci B Polym Phys

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In‐line studies of the initial stages of shear‐induced coalescence in two‐phase polymer blends were carried out with a home‐built device combining a cone and plate rheometer and a fiber‐optic‐assisted fluorescence detection system. A blend of 90 wt % poly(2‐ethylhexyl methacrylate) (PEHMA) and 10 wt % poly(butyl methacrylate) (PBMA) was prepared by the casting of films onto a solid substrate from mixed aqueous latex dispersions of the two polymers. The dispersions were prepared via emulsion polymerization under conditions in which both components were formed as spherical particles with a very narrow size distribution. By using a 14:1 particle ratio of PEHMA to PBMA, we obtained films in which 120‐nm PBMA particles were surrounded by a PEHMA matrix. The blend contained phenanthrene‐labeled PBMA particles and anthracene‐labeled PBMA particles in a ratio of 4:1, whereas the PEHMA matrix polymer was unlabeled. We monitored the anthracene‐to‐phenanthrene fluorescence intensity ratio (I470/I360) as a measure of direct nonradiative energy transfer from phenanthrene to anthracene, whereas the blend was sheared at different shear rates and temperatures. Under no‐shear conditions, the results of in‐line experiments were in good agreement with the results of off‐line measurements of energy transfer by conventional techniques. In blends under shear, the two sets of experiments, in‐line and off‐line, did not agree with each other. The cause of this disagreement was associated with normal forces in the blend under shear that affected the optical path length and the relative intensities of the fluorescence signals of the phenanthrene and anthracene groups in the blend. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2302–2316, 2001

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The flow light-scattering method 18 has been used to investigate shear effects in a ternary system consisting of polystyrene͑PS͒, polybutadiene͑PB͒, and dio-ctylphthalate͑DOP͒ in previous reports. [8][9][10]13,19,20 DOP was chosen as an approximately neutral solvent to PS and PB.…”

Section: Introductionmentioning

confidence: 99%

Shear-flow effects on self-assembly of semidilute solutions of off-critical polymer mixtures: Shear-hysteresis effects

Asakawa

Hashimoto

1996

The Journal of Chemical Physics

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We use flow light scattering to study the phase transitions in semidilute solutions of polystyrene and polybutadiene in dioctylphthalate under simple shear flow. The phase-separated solution was brought into a single-phase state by increasing the shear rate, ␥ , above a critical shear rate, ␥ c,i . The solution was then brought back into a two-phase state by lowering ␥ below a critical shear rate, ␥ c,d . We previously reported a large hysteresis effect in solutions with off-critical compositions; ␥ c,i is always higher than ␥ c,d . Shear-drop experiments were conducted to illuminate the origin of this hysteresis effect. The experimental results showed that at temperatures close to the cloud point temperature the formation of phase separated structures did not occur until up to 22 h after lowering the shear rate below ␥ c,i . Thus the hysteresis effect was found to be due to a surprisingly slow ordering process at ␥ close to ␥ c,i . The ordering induced by the shear drop needs a much longer time than the homogenization induced by increasing shear. If the time scale of observation is sufficiently long, the hysteresis effect disappears, yielding the drop of cloud point temperature with shear, ⌬T c (␥ ), given by ⌬T c (␥ )ϰ␥ 1.0Ϯ0.1 for the off-critical mixtures, rather than ⌬T c (␥ )ϰ␥ 0.5Ϯ0.1 found previously for the near critical mixtures. Finally, the incubation time was found to initially increase with ␥ and then decrease with a further increase of ␥ , suggesting that the ordering mechanisms are different in the low and high shear-rate regimes.

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Shear stabilization of critical fluctuations in bulk polymer blends studied by small angle neutron scattering

Cited by 75 publications

References 50 publications

Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

In‐line monitoring of immiscible polymer blends in a rheometer with a fiber‐optics‐assisted fluorescence detection system

Shear-flow effects on self-assembly of semidilute solutions of off-critical polymer mixtures: Shear-hysteresis effects

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