Investigating the microstructure of a yield-stress fluid by light scattering

Lee, David; Gutowski, Iris A.; Bailey, Arthur E.; Rubatat, Laurent; Bruyn, John R. de; Frisken, Barbara J.

doi:10.1103/physreve.83.031401

Cited by 44 publications

(46 citation statements)

References 26 publications

(45 reference statements)

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“…The data for Carbopol ETD 2050 were qualitatively similar (Gutowski 2010) and are not presented with the same level of detail to avoid redundancy. Our results for the yield stress of ETD 2050 as a function of concentration and pH have previously appeared in Lee et al (2011). ETD 2050 and Ultrez 10 have different crosslink densities, and we compare their behavior towards the end of this section.…”

Section: Resultsmentioning

confidence: 82%

“…Light scattering studies of ETD 2050 microgels for scattering wave vectors ranging from 0.02 to 25 μm −1 have been reported by Lee et al (2011). These measurements revealed microstructure characterized by two length scales: a longer length scale (> 6 μm) that depends on Carbopol concentration and the amount of NaOH added, and a shorter length scale (≈400 nm) that is independent of sample properties.…”

Section: Resultsmentioning

confidence: 93%

“…Once the acid becomes fully dissociated, however, further addition of base simply adds ions that screen the fixed charges, decreasing the osmotic pressure and easing the compression of the polymer network. The microgel particles likely deswell in this regime, although Lee et al (2011) found that they remained too large to be detected in their light scattering measurements. This indicates that any deswelling is much less dramatic than the initial swelling and that the particles do not return to their initial sizes.…”

Section: Discussionmentioning

confidence: 93%

“…The initial increase of the pH causes the acrylic acid groups within the polymer to dissociate. The presence of mobile counter ions results in an increase in the internal osmotic pressure, causing the microgel particles to swell by at least a factor of 1,000 in volume (Lee et al 2011;Oppong and de Bruyn 2011). Once the acid becomes fully dissociated, however, further addition of base simply adds ions that screen the fixed charges, decreasing the osmotic pressure and easing the compression of the polymer network.…”

Section: Discussionmentioning

confidence: 98%

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Scaling and mesostructure of Carbopol dispersions

et al. 2012

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Rheological measurements were performed on aqueous dispersions of two commercial crosslinked polymer microgels, Carbopol Ultrez 10 and Carbopol ETD 2050, prepared over a wide range of concentration and pH. For all concentrations studied, both the yield stress and the elastic modulus initially increased dramatically with pH and displayed broad peaks at intermediate pH. This is consistent with the onset of jamming of the Carbopol particles due to a rapid increase in particle size caused by osmotic swelling in the presence of NaOH. Scaling of both yield stress and elasticity with concentration was observed only at higher concentrations, which we believe indicates a change from a percolated structure at low volume fractions to a space filling network of compressed particles at high volume fractions. This model is supported by confocal microscopy of fluorescently dyed Carbopol dispersions.

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 98%

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Scaling and mesostructure of Carbopol dispersions

et al. 2012

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“…Since the samples exhibit scattering patterns at small scattering angles, an experimental setup with a two-dimensional camera for detection was employed. This type of ultra-small-angle light-scattering setup was successfully employed previously [23][24][25]. The schematic setup is depicted in Fig.…”

Section: Methodsmentioning

confidence: 99%

Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

2014

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Recently the analysis of scattering patterns by angular cross-correlation analysis (CCA) was introduced to reveal the orientational order in disordered samples with special focus to future applications on x-ray free-electron laser facilities. We apply this CCA approach to ultra-small-angle light-scattering data obtained from two-dimensional monolayers of microspheres. The films were studied in addition by optical microscopy. This combined approach allows to calculate the cross-correlations of the scattering patterns, characterized by the orientational correlation function l (q), as well as to obtain the real-space structure of the monolayers. We show that CCA is sensitive to the orientational order of monolayers formed by the microspheres which are not directly visible from the scattering patterns. By mixing microspheres of different radii the sizes of ordered monolayer domains is reduced. For these samples it is shown that l (q) quantitatively describes the degree of hexagonal order of the two-dimensional films. The experimental CCA results are compared with calculations based on the microscopy images. Both techniques show qualitatively similar features. Differences can be attributed to the wave-front distortion of the laser beam in the experiment. This effect is discussed by investigating the effect of different wave fronts on the cross-correlation analysis results. The so-determined characteristics of the cross-correlation analysis will be also relevant for future x-ray-based studies.

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Insights into Carbopol gel formulations: Microscopy analysis of the microstructure and the influence of polyol additives

Lefrançois

Ibarboure

Payré

et al. 2015

J of Applied Polymer Sci

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International audienceCarbopol is a family of high molecular weight cross-linked poyacrylic acids widely used as thickening agents in several industrial applications. In this work, the structure of Carbopol 974P NF was investigated at pH 7.4 by means of capillary viscometry, dynamic rheology, fluorescence microscopy, and electron microscopy in the dilute and semi-dilute (hydrogel) state. Especially, high-pressure freezing technique has proved to be a technique of choice to visualize the Carbopol hydrogel microstructure through cryo-scanning electron microscopy analysis without artifacts related to the formation of ice crystals. It has been shown that the Carbopol hydrogel has a hierarchical structure made of large spherical entities of a few micrometers in size packed together and composed of much smaller agglomerated microgel particles. In addition, fluorescence and electron microscopies have pointed out that the presence of polyol additives in the gel formulation favors the formation of more dense or jammed structure, probably through hydrogen bonding. (c) 2015 Wiley Periodicals, Inc

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Investigating the microstructure of a yield-stress fluid by light scattering

Cited by 44 publications

References 26 publications

Scaling and mesostructure of Carbopol dispersions

Scaling and mesostructure of Carbopol dispersions

Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

Insights into Carbopol gel formulations: Microscopy analysis of the microstructure and the influence of polyol additives

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