From nuclei to micro-structure in colloidal crystallization: Investigating intermediate length scales by small angle laser light scattering

Beyer, R. A.; Franke, Markus; Schöpe, Hans Joachim; Bartsch, E.; Palberg, Thomas

doi:10.1063/1.4928370

Cited by 11 publications

(6 citation statements)

References 93 publications

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“…Its appearance in the early S(q) during the formation of the amorphous state could therefore indicate the presence of some large scale density fluctuations. Therefore, we will in future investigate these samples also by small angle light scattering utilizing the small angle scattering experiment of Beyer [84] in a version modified for investigations on water based samples. This is clearly seen for the sample with n = 4.47 µm -3 ( = 3.9 10 -3 ) in Fig.…”

Section: Resultsmentioning

confidence: 99%

To make a glass—avoid the crystal

Palberg¹,

Bartsch²,

Beyer³

et al. 2016

J. Stat. Mech.

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Colloidal model systems allow for a flexible tuning of particle sizes, particle spacings and mutual interactions at constant temperature. Colloidal suspensions typically crystallize as soon as the interactions get sufficiently strong and long-ranged. Several strategies have been successfully applied to avoid crystallization and instead produce colloidal glasses. Most of these amorphous solids are formed at high particle concentrations. This paper shortly reviews experimental attempts to produce amorphous colloidal solids using strategies based on topological, thermodynamic and kinetic considerations. We complement this overview by introducing a (transient) amorphous solid forming in a thoroughly deionized aqueous suspension of highly charged spheres at low salt concentration and very low volume fractions.

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Section: Resultsmentioning

confidence: 99%

To make a glass—avoid the crystal

Palberg¹,

Bartsch²,

Beyer³

et al. 2016

J. Stat. Mech.

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“…Among the phenomena being researched are for example the glass transition 1-4 and particle crystallisation. [5][6][7][8][9] Of special interest are so-called hard sphere like or nearly hard sphere like particles which provide an easy theoretical treatment and easy computer simulations compared to systems with more complex interactions. 10 The most common systems under study are suspensions of sterically stabilised poly-(methylmethacrylate) (PMMA) particles, as a suspension medium, usually a mixture of organic solvents, is used to match the refractive index and the density of the particles to allow measurements using light scattering [11][12][13] and microscopy [14][15][16][17] while avoiding sedimentation.…”

Section: Introductionmentioning

confidence: 99%

“…The most common microgels are prepared from N-isopropylacrylamide cross-linked with N,N 0 -methylenebisacrylamide (PNiPAM) -well known for its temperature dependent swelling in water. 20,21 Besides the currently very popular PNIPAM microgels, PMMA 22,23 or polystyrene (PS) 7,[24][25][26][27][28] -based microgels are also frequently used as colloidal model systems. While the swelling of the microgel particles provides advantages in terms of refractive index and density matching it may also introduce a certain amount of softness to the system.…”

Section: Introductionmentioning

confidence: 99%

“…glass transition, [24][25][26][27]36 crystallisation kinetics 7,28,[37][38][39] or collective 33 and single 40 particle diffusion. While the assumption of hard sphere behaviour of the PS microgels is supported by many studies 7,36,39,40 systematic differences between particles of different cross-linking ratios can be observed in mixtures of PS microgels and free non-absorbing polymers. 41 Here it has been observed that the addition of a free PS polymer to 1 : 50 cross-linked PS microgel particles shifts the glass transition to much higher values 26 than that observed for a comparable PMMA colloid-PS free polymer system.…”

Section: Introductionmentioning

confidence: 99%

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On tuning microgel character and softness of cross-linked polystyrene particles

et al. 2017

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Polystyrene (PS) microgel colloids have often been used successfully to model hard sphere behaviour even though the term "gel" invokes inevitably the notion of a more or less soft, deformable object. Here we systematically study the effect of reducing the cross-link density from 1 : 10 (1 cross-link per 10 monomers) to 1 : 100 on particle interactions and "softness". We report on the synthesis and purification of 1 : 10, 1 : 25, 1 : 50, 1 : 75 and 1 : 100 cross-linked PS particles and their characterization in terms of single particle properties, as well as the behaviour of concentrated dispersions. We are able to tune particle softness in the range between soft PNiPAM-microgels and hard PMMA particles while still allowing the mapping of the microgels onto hard sphere behavior with respect to phase diagram and static structure factors. This is mainly due to a rather homogeneous radial distribution of cross-links in contrast to PNiPAM microgels where the cross-link density decreases radially. We find that up to a cross-link density of 1 : 50 particle form factors are perfectly described by a homogeneous sphere model whereas 1 : 75 and 1 : 100 cross-linked spheres are slightly better described as fuzzy spheres. However the fuzziness is rather small compared to typical PNiPAM microgels so that a hard sphere mapping still holds even for these low cross-link densities. Finally, by varying the reaction conditions - changing from batch to semibatch emulsion polymerization and varying the feed rate or by adjusting the monomer to initiator ratio we can tune the fuzziness or significantly alter the inner structure to a more open, star-like architecture.

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“…Several such systems have been developed, in particular Nisopropylacrylamide particles cross-linked with N,N'-methylenbisacrylamide, whose swelling ratio in water may be controlled by the temperature [18,19]. In the present study, nonthermosensitive PS microgel particles are used [20,21]. Their structure and dynamical properties [22,23] have been studied in detail and closely match that of hard sphere suspensions [24].…”

Section: System a Experimental Systemmentioning

confidence: 93%

Stress overshoot, hysteresis and Bauschinger effect in sheared dense colloidal suspensions

Kushnir¹,

Ruscher²,

Bartsch³

et al. 2022

Preprint

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The mechanical non-linear response of dense Brownian suspensions of polymer gel particles is studied experimentally and by means of numerical simulations. It is shown that the response to the application of a constant shear rate depends on the previous history of the suspension. When the flow starts from a suspension at rest, it exhibits an elastic response followed by a stress overshoot and then a plastic flow regime. Conversely, after flow reversal, the stress overshoot does not occur, and the apparent elastic modulus is reduced while numerical simulations reveal that the anisotropy of the local microstructure is delayed relative to the macroscopic stress.

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From nuclei to micro-structure in colloidal crystallization: Investigating intermediate length scales by small angle laser light scattering

Abstract: shows that further refinement and adaptation of the theoretical expressions to the sample specific boundary conditions is desired for a quantitative kinetic analysis of micro-structural evolution.

Cited by 11 publications

References 93 publications

To make a glass—avoid the crystal

To make a glass—avoid the crystal

On tuning microgel character and softness of cross-linked polystyrene particles

Stress overshoot, hysteresis and Bauschinger effect in sheared dense colloidal suspensions

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