Mandel'shtam-Brillouin spectra in the critical mixture of nitroethane-isooctane

Aref'ev, I. M.; Fabelinskiĭ, Immanuil L.; Анисимов, М. А.; Kiyachenko, Yu. F.; Voronov, V. P.

doi:10.1016/0030-4018(73)90338-6

Cited by 12 publications

(5 citation statements)

References 6 publications

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“…The amplitude is larger, but of the same order of magnitude as that predicted by the regular solution model. The fact that we find the classical exponent for the pseudo-spinodal curve is in contrast to the results of Chu et al [12]. Our experimental data, however, show that a value of P* close to the exponent of the coexistence curve is unlikely.…”

Section: --~~--~~~~~~~~~-----contrasting

confidence: 85%

“…Corrections due to double and multiple scattering are therefore not necessary. At the critical concentration those systems have been carefully studied [3,12,20]. The purpose of this work is to check on the hypothesis whether the exponent y of the susceptibility is independent on the concentration even though the type of phase transition changes from second to first order.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamic Light Scattering of the Fluid‐Fluid Phase Transition in the Vicinity of the Critical Solution Point and in the First Order Transition Region

Schröer

Rybarsch

Strojny

et al. 1988

Ber Bunsenges Phys Chem

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Critical Phenomena / Light. Scattering / Liquids / Phase Transitions / Solutions Measurements of the Rayleigh-Brillouin spectra of the binary system nitroethane-isooctane have been carried out as function of temperature and concentration. The purpose of this investigation was to study the transition of one type of phase transformation to an other. Taking the temperature as variable, the phase transformation is of second order for one specific concentration -the critical concentration, whereas for other concentrations it is of first order. Samples deviating up to 20% from the critical composition have been investigated in the temperature range 10 to 10-3 K above the transition temperature in the homogeneous region. The temperature dependence of the Rayleigh-Brillouin intensity ratio 1,/2/ b can be described by the same critical exponent y = 1.24 for all concentrations provided the critical temperature in the scaling function is replaced by another reference temperature, interpreted as pseudo-spinodal temperature T s *' The concentration dependence of T s* is found to be IX -Xci = A· tt*, where t, is the reduced temperature t, = 1 -Ts*/T c. The value ofthe exponent is found to be P* = 0.5, which is the classical exponent of the spinodal curve.

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Section: --~~--~~~~~~~~~-----contrasting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Dynamic Light Scattering of the Fluid‐Fluid Phase Transition in the Vicinity of the Critical Solution Point and in the First Order Transition Region

Schröer

Rybarsch

Strojny

et al. 1988

Ber Bunsenges Phys Chem

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“…In our work the exceptionally close difference between the refractive indices of the solvent components, nitroethane and isooctane (∼0.002), makes the critical opalescence relatively weak (while still reliably measurable very close to the critical point) [14], thus enabling us to simultaneously observe the Brownian motion of the polymer coils and the diverging correlation length of the critical fluctuations.…”

mentioning

confidence: 89%

“…The nitroethane+isooctane mixture has an upper critical solution temperature [14,15] and the addition of a polymer increases the critical temperature, thus again contradicting the major assumption in the theory of Brochard and de Gennes. The behavior of the critical temperatures for the studied systems is shown in Fig.…”

mentioning

confidence: 94%

Unusual Transformation of Polymer Coils in a Mixed Solvent Close to the Critical Point

et al. 2018

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We have discovered unusual behavior of polymer coils in a binary solvent (nitroethane+isooctane) near the critical temperature of demixing. The exceptionally close refractive indices of the solvent components make the critical opalescence relatively weak, thus enabling us to simultaneously observe the Brownian motion of the polymer coils and the diverging correlation length of the critical fluctuations. The polymer coils exhibit a collapse-reswelling-expansion-reshrinking transition upon approaching the critical temperature. While the first stage (collapse-reswelling) can be explained by the theory of Brochard and de Gennes, the subsequent expansion-reshrinking transition is a new unexpected phenomenon that has not been observed so far. We believe that this effect is generic and attribute it to micro-phase separation of the solvent inside the polymer coil.

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“…Recently, we studied the behavior of dilute polymer chains (polystyrene and poly-butyl methacrylate) of various molecular weights near the liquid-liquid critical point of a binary solvent (nitroethane+isooctane) by dynamic light scattering 17 . The mixture nitroethane+isooctane is special in that the difference between the refractive indices of the two liquid components is exceptionally small, so that the critical opalescence is weak while still measurable 18,19 . Hence, we have been able to simultaneously observe the Brownian motion of the polymers and the diverging correlation length of the critical fluctuations closer to the critical temperature than previous investigators.…”

Section: Introductionmentioning

confidence: 99%

Physical origin of the expansion of polymer coils in a binary solvent in the vicinity of its demixing critical point

2019

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Critical fluctuations are known to induce a collapse of polymer chains in a mixed solvent upon approaching its liquid-liquid critical point, as originally predicted by Brochard and de Gennes. Recently, we have found that closer to the critical point this collapse is followed by a reswelling of the polymer coils well beyond the original dimensions, a phenomenon not predicted by the theory of Brochard and de Gennes. We submit that upon approaching the critical temperature more closely, the correlation length of the critical fluctuations inside the polymer coils can no longer further increase due to the finite size of the coils, resulting in the appearance of large critical Casimir forces that cause a significant expansion of the polymer coils. Eventually, micro-phase separation inside the coils will appear and the coils will reshrink. This entire process takes place while the bulk solution is still in the one-phase region.

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Mandel'shtam-Brillouin spectra in the critical mixture of nitroethane-isooctane

Cited by 12 publications

References 6 publications

Dynamic Light Scattering of the Fluid‐Fluid Phase Transition in the Vicinity of the Critical Solution Point and in the First Order Transition Region

Dynamic Light Scattering of the Fluid‐Fluid Phase Transition in the Vicinity of the Critical Solution Point and in the First Order Transition Region

Unusual Transformation of Polymer Coils in a Mixed Solvent Close to the Critical Point

Physical origin of the expansion of polymer coils in a binary solvent in the vicinity of its demixing critical point

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