Thermosensitive core-shell particles as model systems for studying the flow behavior of concentrated colloidal dispersions

Crassous, Jérôme J.; Siebenbürger, Miriam; Ballauff, Matthias; Drechsler, Markus; Henrich, Oliver; Fuchs, Matthias

doi:10.1063/1.2374886

Cited by 105 publications

(160 citation statements)

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“…The typical entropy change for deformed grafted chains is $10 3 times smaller than for free chains [18]. The estimated order of $10 6 monomers in the grafted layer agrees with the value $3 Â 10 6 based on the known composition of our system [9]. To conclude, we have presented a kinetic model that can account for spontaneous dimer dissociation which, combined with light-scattering experiments, provides a robust protocol for quantifying the dissociation rate and the reversible association (dimerization) energy of mutually attractive Brownian molecules and nanoparticles.…”

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confidence: 74%

“…As this value is mostly independent of the surface chemistry [14], we take it here as the width of the effective well. Furthermore, this value is much larger than the molecular roughness of the PNIPAM shell, which is of the order of 1 nm [9,10], such that the attractive hydrophobic force dominates over repulsive entropic protrusion forces which are much shorter-ranged [14]. There is now only one free parameter in our model, the depth of the effective attraction well, V min , i.e., the binding energy of the dimers.…”

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confidence: 99%

“…It is a well-established fact that these particles become Published in " " which should be cited to refer to this work. attractive above T c [9]. This is due to the hydrophobic interaction between the PNIPAM-network for which water has become a poor solvent under these conditions.…”

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confidence: 99%

“…In the T interval where the turnover in V min occurs, the PNIPAM network grafted on the particle surface undergoes a transition from a hydrophilic (L) to a hydrophobic (B) state with increasing T. The transition is associated with a volume change from V L to V B . In the thermodynamic limit, this would be a first-order phase transition [9] with the volume as the order parameter, but now it is smeared due to the finite size of a nanoparticle [15]. On a phenomenological level, this transition is captured by a partition function…”

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confidence: 99%

“…The thermosensitive particles have been synthesized and characterized as described in [9]. Core-shell particles with 5 mol.…”

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confidence: 99%

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Quantifying the Reversible Association of Thermosensitive Nanoparticles

et al. 2011

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Under many conditions, biomolecules and nanoparticles associate by means of attractive bonds, due to hydrophobic attraction. Extracting the microscopic association or dissociation rates from experimental data is complicated by the dissociation events and by the sensitivity of the binding force to temperature (T). Here we introduce a theoretical model that combined with light-scattering experiments allows us to quantify these rates and the reversible binding energy as a function of T. We apply this method to the reversible aggregation of thermoresponsive polystyrene/poly(N-isopropylacrylamide) core-shell nanoparticles, as a model system for biomolecules. We find that the binding energy changes sharply with T, and relate this remarkable switchable behavior to the hydrophobic-hydrophilic transition of the thermosensitive nanoparticles.The association and self-organization of biomolecules [1] and nanoparticles [2] play a fundamental role in many physiological processes [3], such as protein amyloid formation which is responsible for neuro-degenerative diseases [4], as well as in technological processes. In particular the assembly of nanoparticles has become a key step in the synthesis of nanomaterials with new optical and mechanical properties [5]. In order to understand and control all these association processes, it is essential to understand and control the association kinetics [3,4]. This is challenging in the case of biomolecules and nanoparticles where often the microscopic binding energy, which directly determines the rate of dimer formation, is comparable to the thermal energy k B T. This poses two major difficulties: (i) the experimental detection of the binding energy has to be accurate down to the k B T scale, and (ii) the association kinetics is affected by dissociation events [6,7] since the binding energy is comparable with the average kinetic energy of the particles/molecules. It has been recently shown that a clear understanding of protein aggregation under physiological conditions cannot be achieved without the understanding of aggregate dissociation [7]. A further complication arises from the fact that the binding energy can be very sensitive to changes of the solution parameters, such as T and pH [3].In this Letter we propose a detection strategy that can overcome many of the difficulties to date in extracting quantitative information about the intrinsic rates of association and dissociation processes. The essence of the strategy is to combine a kinetic model with the analysis of dynamic light scattering (DLS) data of aggregation kinetics. Dynamic light scattering has proven to be a reliable tool for analyzing irreversible aggregation [8].Here we show that it can be used for measuring reversible processes as well, but the data analysis requires a new model fully accounting for dissociation processes. Here we introduce such a model and demonstrate its applicability in light scattering experiments of thermosensitive nanoparticles in aqueous suspension. We also show how to quantify the T-dependent int...

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supporting

confidence: 74%

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

“…The thermosensitive particles have been synthesized and characterized as described in [9]. Core-shell particles with 5 mol.…”

mentioning

confidence: 99%