Phase‐Separation Kinetics and Mechanism in a Methylcellulose/Salt Aqueous Solution Studied by Time‐Resolved Small‐Angle Light Scattering (SALS)

Villetti, Marcos A.; Soldi, Valdir; Rochas, C.; Borsali, Rédouane

doi:10.1002/macp.201000697

Cited by 28 publications

(22 citation statements)

References 52 publications

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“…In principle, the early stage of spinodal decomposition should be signaled by a maximum in SANS scattering I(q) at a finite q. 45 As some of us have shown for MC previously, 7 with slow heating, there is no maximum in I(q) at any finite q for the measured range of 0.003 < q < 0.1 Å −1 . Furthermore, preliminary SANS measurements on the samples described in this paper also show no hint of a scattering peak (data not shown).…”

Section: ■ Results and Discussionmentioning

confidence: 96%

Interplay of Phase Separation and Thermoreversible Gelation in Aqueous Methylcellulose Solutions

et al. 2012

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Rheology and turbidity measurements were performed under similar thermal histories to probe the relationship between thermoreversible gelation and phase separation for a set of three methylcellulose (MC) materials with similar degrees of substitution (DS) and contrasting molecular weights after hydration in cold water. Frequency-independent loss tangents were used to identify the gel point (T gel ) in MC solutions well over the chain overlap concentration (c ≥ 10c*). Transmittance of 633 nm laser light through the solutions revealed that all MC solutions cloud upon gelling, with a relative transmittance of 86% closely associated with the gel point. The gelation temperature of MC solutions was found to decrease with increasing MC concentration and the results for all molecular weights superposed. Using gel and cloud points, a phase diagram was constructed which reveals that clear MC solutions transition directly into turbid gels. Frequency-independent storage moduli of fully developed MC gels scaled with φ 2.3 , consistent with theory and experiment of entangled systems. Gelation of MC has strong dependence on heating rate while the melting of the gel has little dependence on cooling rate, suggesting that thermogelation of MC proceeded by a nucleation and growth mechanism rather than spinodal decomposition.

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Section: ■ Results and Discussionmentioning

confidence: 96%

Interplay of Phase Separation and Thermoreversible Gelation in Aqueous Methylcellulose Solutions

et al. 2012

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“…Yushmanov et al [ 27 ] performed T-jump NMR spectroscopy for PNIPAM and revealed that intermolecular aggregation (demixing) takes place faster than 1 s, being followed by a slow reorganization ( < 100 s). Villetti et al [ 28 ] also found a slow relaxation component for a methylcellulose/salt aqueous solution by means of a small-angle light-scattering measurement. Furthermore, it should be particularly noted that Ye et al [ 29 ] performed T-jump fl uorescence spectroscopy to reveal two stages (two temporal regimes, 0.1 and 0.8 ms) in the coil-globule phase transition process.…”

Section: Methodsmentioning

confidence: 99%

Phase Separation Dynamics of Aqueous Poly [(2‐ethoxy) ethoxy ethyl vinyl ether] Solutions as Explored using the Laser T‐Jump Technique Combined With Photometry

Tsuboi

Kikuchi

Kitamura

et al. 2011

Macro Chemistry & Physics

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Poly[(2‐ethoxy) ethoxy ethyl vinyl ether] (poly(EOEOVE)) is a representative thermoresponsive polymer in aqueous solution for which the time constants of the phase separation (PS) are determined with high accuracy. It is revealed that the PS dynamics of the polymer are entirely different from those of the poly(N‐isopropylacrylamide) (PNIPAM) system, which is an alternative representative thermoresponsive polymer. Poly(EOEOVE) exhibits complicated PS behavior that is described using double exponential functions. The PS of poly(EOEOVE) is much faster than the PS of PNIPAM in aqueous solutions and becomes faster with increasing concentration of the polymer. PS behavior that is particular to the present system is successfully understood within the framework of the aggregation mechanism.

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“…One strategy for creating such solutions at room temperature is the use of NaCl. The addition of NaCl has been widely reported to impact the gelation temperature, such that gel temperature decreases monotonically with increasing concentration of NaCl. − The results from CaBER experiments demonstrate that the addition of MC fibrils into MC solutions causes a transition from a shear-thinning power-law fluid behavior to an elastic-like fluid deformation.…”

mentioning

confidence: 99%

Extensional Flow Behavior of Methylcellulose Solutions Containing Fibrils

et al. 2018

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The extensional properties of semidilute aqueous methylcellulose (MC) solutions have been characterized. Pure aqueous MC solutions are shear-thinning liquids at room temperature. With the addition of 8 wt % NaCl, a fraction of MC self-assembles into long fibrils, which modify the rheological properties of the original MC solution. Capillary Breakup Extensional Rheometry (CaBER) was used to characterize salt-free and 8 wt % NaCl solutions of MC at room temperature. The salt-free solutions exhibit only power-law behavior whereas solutions with NaCl exhibit both power-law and elastic regimes. As MC concentration increases, the extensional relaxation time also increases strongly, from 0.04 s at 0.5 wt % to 4 s at 1 wt %. In addition, the apparent extensional viscosity rapidly increases as a function of increasing MC concentration, from 40 Pa•s at 0.5 wt % to 1300 Pa•s at 1 wt %. This behavior is attributed to the presence of fibrils in the MC solutions containing NaCl.

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Phase‐Separation Kinetics and Mechanism in a Methylcellulose/Salt Aqueous Solution Studied by Time‐Resolved Small‐Angle Light Scattering (SALS)

Cited by 28 publications

References 52 publications

Interplay of Phase Separation and Thermoreversible Gelation in Aqueous Methylcellulose Solutions

Interplay of Phase Separation and Thermoreversible Gelation in Aqueous Methylcellulose Solutions

Phase Separation Dynamics of Aqueous Poly [(2‐ethoxy) ethoxy ethyl vinyl ether] Solutions as Explored using the Laser T‐Jump Technique Combined With Photometry

Extensional Flow Behavior of Methylcellulose Solutions Containing Fibrils

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