| 1. |
- Rochette, Christophe N., et al.
(författare)
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Shell Structure of Natural Rubber Particles: Evidence of Chemical Stratification by Electrokinetics and Cryo-TEM
- 2013
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 29:47, s. 14655-14665
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (mu) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a similar to 2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of mu on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged similar to 3.5 nm thick layer (mean dissociation pK similar to 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK similar to 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.
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| 2. |
- Azari, Arash, et al.
(författare)
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Directed Self-Assembly of Polarizable Ellipsoids in an External Electric Field
- 2017
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 33:48, s. 13834-13840
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Tidskriftsartikel (refereegranskat)abstract
- The interplay between shape anisotropy and directed long-range interactions enables the self-assembly of complex colloidal structures. As a recent highlight, ellipsoidal particles polarized in an external electric field were observed to associate into well-defined tubular structures. In this study, we systematically investigate such directed self-assembly using Monte Carlo simulations of a two-point-charge model of polarizable prolate ellipsoids. In spite of its simplicity and computational efficiency, we demonstrate that the model is capable of capturing the complex structures observed in experiments on ellipsoidal colloids at low volume fractions. We show that, at sufficiently high electric field strength, the anisotropy in shape and electrostatic interactions causes a transition from three-dimensional crystal structures observed at low aspect ratios to two-dimensional sheets and tubes at higher aspect ratios. Our work thus illustrates the rich self-assembly behavior accessible when exploiting the interplay between competing long- and short-range anisotropic interactions in colloidal systems.
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| 3. |
- Cautela, Jacopo, et al.
(författare)
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Supracolloidal Atomium
- 2020
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 14:11, s. 15748-15756
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Tidskriftsartikel (refereegranskat)abstract
- Nature suggests that complex materials result from a hierarchical organization of matter at different length scales. At the nano- and micrometer scale, macromolecules and supramolecular aggregates spontaneously assemble into supracolloidal structures whose complexity is given by the coexistence of various colloidal entities and the specific interactions between them. Here, we demonstrate how such control can be implemented by engineering specially customized bile salt derivative-based supramolecular tubules that exhibit a highly specific interaction with polymeric microgel spheres at their extremities thanks to their scroll-like structure. This design allows for hierarchical supracolloidal self-assembly of microgels and supramolecular scrolls into a regular framework of “nodes” and “linkers”. The supramolecular assembly into scrolls can be triggered by pH and temperature, thereby providing the whole supracolloidal system with interesting stimuli-responsive properties. A colloidal smart assembly is embodied with features of center-linker frameworks as those found in molecular metal–organic frameworks and in structures engineered at human scale, masterfully represented by the Atomium in Bruxelles.
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| 4. |
- Crassous, Jerome, et al.
(författare)
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Advanced multiresponsive comploids: from design to possible applications.
- 2014
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 6:15, s. 8726-8735
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Tidskriftsartikel (refereegranskat)abstract
- We extend the commonly used synthesis strategies for responsive microgels to the design of novel multiresponsive and multifunctional nanoparticles that combine inorganic magnetic, metallic/catalytic and thermoresponsive organic moieties. Magnetic responsiveness is implemented through the integration of silica-coated maghemite nanoparticles into fluorescently labeled crosslinked poly(N-isopropylmethacrylamide) microgels. These particles are then employed as templates for the in situ reduction of catalytically active gold nanoparticles. In order to tune the reactivity of the catalyst through a thermally controlled barrier, an additional layer of crosslinked poly(N-isopropylacrylamide) is added in the final step. We subsequently demonstrate that these particles can be employed as smart catalysts. We show that the thermoresponsive nature of the outer particle shell not only provides control over the catalytic activity, but when combined with a magnetic core allows for very efficient removal of the catalytic system through temperature-controlled reversible coagulation and subsequent magnetophoresis in an applied magnetic field gradient. We finally discuss the use of this design principle for the synthesis of complex hybrid particles for various applications that would all profit from their multiresponsive and multifunctional nature.
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| 5. |
- Crassous, Jerome, et al.
(författare)
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Anisotropic responsive microgels with tuneable shape and interactions
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:38, s. 15971-15982
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Tidskriftsartikel (refereegranskat)abstract
- Highly monodisperse polystyrene/poly(N-isopropylmethacrylamide) (PS-PNIPMAM) core-shell composite microgels were synthesized and further nanoengineered in either ellipsoidal, faceted or bowl-shaped particles. Beside their anisotropy in shape, the microgel design enables an exquisite control of the particle conformation, size and interactions from swollen and hydrophilic to collapsed and hydrophobic using temperature as an external control variable. The post-processing procedures and the characterization of the different particles are first presented. Their potential as model systems for the investigation of the effects of anisotropic shape and interactions on the phase behavior is further demonstrated. Finally, the self-assembly of bowl-shaped composite microgel particles is discussed, where the temperature and an external AC electric field are employed to control the interactions from repulsive to attractive and from soft repulsive to dipolar, respectively.
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| 6. |
- Crassous, Jerome, et al.
(författare)
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Design of block copolymer micelles via crystallization
- 2015
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 62, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- This Feature Article provides an overview of the progress made over the last few years in the design of diblock copolymer micelles based on crystallization-driven self-assembly (CDSA) towards the development of novel and fascinating morphologies with crystalline-cores. Here, we describe the different approaches employed in order to engineer a large variety of semicrystalline micellar architectures. We highlight kinetic strategies that have been employed to direct morphological transitions, which can then be further tuned thus increasing the range of possible micellar structures. We then emphasize the development of complex hybrid assemblies generated by taking advantage of the self-assembly process of crystalline-corona di-BCP micelles with colloidal particles. Each section introduces and emphasizes the potential applications of this class of nanomaterials. (C) 2015 Elsevier Ltd. All rights reserved.
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| 7. |
- Crassous, Jerome, et al.
(författare)
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Field-induced assembly of colloidal ellipsoids into well-defined microtubules.
- 2014
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Current theoretical attempts to understand the reversible formation of stable microtubules and virus shells are generally based on shape-specific building blocks or monomers, where the local curvature of the resulting structure is explicitly built-in via the monomer geometry. Here we demonstrate that even simple ellipsoidal colloids can reversibly self-assemble into regular tubular structures when subjected to an alternating electric field. Supported by model calculations, we discuss the combined effects of anisotropic shape and field-induced dipolar interactions on the reversible formation of self-assembled structures. Our observations show that the formation of tubular structures through self-assembly requires much less geometrical and interaction specificity than previously thought, and advance our current understanding of the minimal requirements for self-assembly into regular virus-like structures.
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| 8. |
- Crassous, Jerome, et al.
(författare)
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Giant hollow fiber formation through self-assembly of oppositely charged polyelectrolyte brushes and gold nanoparticles
- 2013
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 9:38, s. 9111-9118
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Tidskriftsartikel (refereegranskat)abstract
- We report on the use of binary mixtures of oppositely charged gold nanoparticles (AuNPs) and spherical polyelectrolyte brushes (SPBs), consisting of a polystyrene core onto which long polystyrene sulfonate chains are grafted, as a simple model system to investigate the influence of directional interactions on self-assembly. We demonstrate that the mixing ratio, i.e., the number of AuNPs per SPB, has a profound influence on self-assembly. In particular we report on the formation of giant hollow fibers, and present a thorough characterization of these nanostructures. We speculate that the adsorption of a few AuNPs on the SPBs appears to direct the tubular self-assembly, and discuss the analogy to the case of modified proteins such as tubulin under the action of nucleotides.
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| 9. |
- Crassous, Jerome J., et al.
(författare)
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Asymmetric self-assembly of oppositely charged composite microgels and gold nanoparticles
- 2012
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 8:5, s. 1648-1656
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Tidskriftsartikel (refereegranskat)abstract
- The electrostatically driven self-assembly of oppositely charged gold nanoparticles (Au NPs) and polystyrene/poly(N-isopropylacrylamide) (PS/PNIPAm) core-shell microgels (CSMs) has been investigated. The co-assembly was accomplished by addition of smaller Au NPs to CSMs in dilute conditions up to a number ratio of about 1 : 1, when the suspension is destabilized. A combination of different techniques (i.e. turbidimetric titration, electrophoretic mobility, UV-visible spectroscopy, dynamic light scattering and microscopy techniques) were used to investigate the association between the two particles and the stability of the different mixtures. Hereby we demonstrate that the size ratio between the two particles (about 4 to 1) and the asymmetric character of the association result in the formation of electrostatic hybrid complexes, analogous to dipolar colloidal molecules, which further rearrange into finite sized clusters for number ratios N(AuNPs)/N(CSMs) < 1.
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| 10. |
- Crassous, Jerome, et al.
(författare)
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Multiscale directed self-assembly of composite microgels in complex electric fields
- 2017
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Ingår i: Soft Matter. - 1744-683X. ; 13:1, s. 88-100
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Tidskriftsartikel (refereegranskat)abstract
- This study explored the application of localized electric fields for reversible directed self-assembly of colloidal particles in 3 dimensions. Electric field microgradients, arising from the use of micro-patterned electrodes, were utilized to direct the localization and self-assembly of polarizable (charged) particles resulting from a combination of dielectrophoretic and multipolar forces. Deionized dispersions of spherical and ellipsoidal core-shell microgels were employed for investigating their assembly under an external alternating electric field. We demonstrated that the frequency of the field allowed for an exquisite control over the localization of the particles and their self-assembled structures near the electrodes. We extended this approach to concentrated binary dispersions consisting of polarizable and less polarizable composite microgels. Furthermore, we utilized the thermosensitivity of the microgels to adjust the effective volume fraction and the dynamics of the system, which provided the possibility to dynamically “solidify” the assembly of the field-responsive particles by a temperature quench from their initial fluid state into an arrested crystalline state. Reversible solidification enables us to re-write/reconstruct various 3 dimensional assemblies by varying the applied field frequency.
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