Particules Janus cylindriques formées par auto-assemblage de polymères en milieu aqueux

Contrôler la forme et la structure des nanoparticules est utile dans le cadre de nombreuses applications. L’objectif de cette étude était de déterminer si et comment la liaison hydrogène peut être utilisée pour contrôler la forme et la structure fine de nanoparticules de polymère formées dans l'eau par auto-assemblage. Les principaux effets démontrés sont les suivants. (1) Des particules cylindriques très stables d'une longueur de plusieurs centaines de nanomètres et d'un diamètre monodisperse de 10 nm peuvent être obtenues dans l'eau par auto-assemblage de polymères hydrophiles décorés par un motif penta-urée. Aucun domaine hydrophobe particulier n'est requis pour sa stabilité. (2) La structure de l'espaceur reliant le motif associatif au polymère a un effet précédemment sous-estimé sur la longueur des particules cylindriques. (3) Un motif associatif par liaisons hydrogène peut être associé à un polymère thermosensible, pour former des particules cylindriques à température ambiante mais qui se désassemblent à des températures plus basses. (4) Des particules cylindriques Janus (c'est-à-dire des particules non-centrosymétriques, allongées, avec deux faces de compositions différentes) peuvent être obtenues.Controlling the shape and the structure of nanoparticles is useful in the context of many applications. The objective of this study was to determine if and how hydrogen bonded self-assembly in water can be used to control the shape and the fine structure of polymer nanoparticles. The main effects that were demonstrated are the following. (1) Very stable rod-like particles with a length of several hundreds of nanometers and a monodisperse diameter of 10 nm can be obtained in water by self-assembly of hydrophilic polymers decorated by a penta-urea sticker. No obvious hydrophobic domain is required for its stability. (2) The structure of the spacer connecting the sticker to the polymer has a previously underestimated effect on the length of the nanorods. (3) The control of the shape of the nanoparticles by a hydrogen bonded sticker can be combined with the thermo-responsiveness of the polymer, so that the nanorods formed at room temperature disassemble at lower temperatures. (4) It is possible to prepare Janus nanorods (i.e. non-centrosymmetric rod-like particles with two sides of different compositions) by using unsymmetrical and complementary tris-urea stickers in water. The Janus topology is obtained independently of the actual polymers used. The versatility and scalability of this approach allows to investigate the rich properties that can be predicted for such easily functionalizable nano-objects. In particular, we show these Janus nanorods are superior stabilizers for oil in water emulsions

Oligo‐Urea with No Alkylene Unit Self‐Assembles into Rod‐Like Objects in Water

International audienceLong and rigid objects formed by self‐assembly in water are useful as templates or for their rheological or biological properties. They are usually obtained by combining hydrogen bonding and strong hydrophobic interactions brought by an alkyl or alkylene chain. A simple access to well‐defined rod‐like assemblies in water is reported based on a penta‐urea sticker directly connected to poly(ethylene oxide) side chains. These assemblies are characterized by an average length of several hundreds of nanometers and a monodisperse radius (4.5 nm) resulting from a reduced lateral aggregation of the stickers

Reversible complexation mediated living radical polymerization using tetraalkylammonium chloride catalysts

This work reports the first use of organic chloride salts as catalysts for reversible complexation mediated living radical polymerization. Owing to the strong halogen-bond forming ability of Cl−, the studied four tetraalkylammonium chloride catalysts (R4N+Cl−) successfully control the polymerizations of methyl methacrylate, yielding polymers with low dispersities up to high monomer conversion (>90%). Benzyldodecyldimethylammonium chloride is further exploited to other methacrylates and yields low-dispersity block copolymers. The advantages of the chloride salt catalysts are wide monomer scope, good livingness, accessibility to block copolymers, and good solubility in organic media. Because of the good solubility, the use of the chloride salt catalysts can prevent agglomeration of catalysts on reactor walls in organic media, which is an industrially attractive feature. Among halide anions, chloride anion is the most abundant and least expensive halide anion, and therefore, the use of the chloride salt catalysts may lower the cost of the polymerization.National Research Foundation (NRF)Submitted/Accepted versionThis work was partly supported by National Research Foundation (NRF) Investigatorship in Singapore (NRF-NRFI05-2019-0001)

External Stimuli-Induced Welding of Dynamic Cross-Linked Polymer Networks

Thermosets have been crucial in modern engineering for decades, finding applications in various industries. Welding cross-linked components are essential in the processing of thermosets for repairing damaged areas or fabricating complex structures. However, the inherent insolubility and infusibility of thermoset materials, attributed to their three-dimensional network structure, pose challenges to welding development. Incorporating dynamic chemical bonds into highly cross-linked networks bridges the gap between thermosets and thermoplastics presenting a promising avenue for innovative welding techniques. External stimuli, including thermal, light, solvent, pH, electric, and magnetic fields, induce dynamic bonds’ breakage and reformation, rendering the cross-linked network malleable. This plasticity facilitates the seamless linkage of two parts to an integral whole, attracting significant attention for potential applications in soft actuators, smart devices, solid batteries, and more. This review provides a comprehensive overview of dynamic bonds employed in welding dynamic cross-linked networks (DCNs). It extensively discusses the classification and fabrication of common epoxy DCNs and acrylate DCNs. Notably, recent advancements in welding processes based on DCNs under external stimuli are detailed, focusing on the welding dynamics among covalent adaptable networks (CANs)

Crucial Role of the Spacer in Tuning the Length of Self-Assembled Nanorods

International audiencePolymeric supramolecular nanorods were prepared in toluene by self-assembly of tris(urea) stickers connected on both sides through alkyl spacers of different lengths to short polystyrene (PS) arms. Several tris(urea) initiators or chain transfer agents were synthesized straightforwardly and used to grow well-defined PS arms via atom transfer radical polymerization (ATRP) or reversible addition fragmentation chain transfer (RAFT) polymerization. Self-assembly was investigated by means of Fourier-transform infrared (FTIR) spectroscopy and light/neutron scattering. A dramatic impact of the spacer separating the tris(urea) sticker from the PS arms on the extent of self-assembly was observed in toluene as long as the degree of polymerization of the PS arms (x) was kept short (x ∼ 10). Indeed, supramolecular nanorods several hundreds of nanometers in length for a few nanometers in radius were obtained with a spacer consisting of nine atoms, whereas five times shorter nanorods were obtained for a spacer of only five atoms, and spherical particles were found in the absence of any spacer, all other parameters remaining unchanged. These results reveal the possibility to tune the length of polymer-decorated supramolecular nanorods with minimal modification of the assembling sticker and without affecting the functionality of the rods

Straightforward Preparation of Supramolecular Janus Nanorods by Hydrogen Bonding of End-Functionalized Polymers

Janus cylinders are one-dimensional colloids that have two faces with different compositions and functionalities and are useful as building blocks for advanced functional materials. Such anisotropic objects are difficult to prepare with nanometric dimensions. Here we describe a robust and versatile strategy to form micrometer long Janus nanorods with diameters in the 10-nanometer range, by self-assembly in water of end-functionalized polymers. For the first time, the Janus topology is not a result of the phase segregation of incompatible polymer arms, but is driven by the interactions between unsymmetrical and complementary hydrogen bonded stickers. It is therefore independent of the actual polymers used and works even for compatible polymers. To illustrate their applicative potential, we show that these Janus nanorods can efficiently stabilize oil-in-water emulsions

Supramolecular design of Janus nanocylinders in solution

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Straightforward preparation of supramolecular Janus nanorods by hydrogen bonding of end-functionalized polymers

International audienceJanus cylinders are one-dimensional colloids that have two faces with different compositions and functionalities, and are useful as building blocks for advanced functional materials. Such anisotropic objects are difficult to prepare with nanometric dimensions. Here we describe a robust and versatile strategy to form micrometer long Janus nanorods with diameters in the 10-nanometer range, by self-assembly in water of end-functionalized polymers. The Janus topology is not a result of the phase segregation of incompatible polymer arms, but is driven by the interactions between unsymmetrical and complementary hydrogen bonded stickers. Therefore, even compatible polymers can be used to form these Janus objects. In fact, any polymers should qualify, as long as they do not prevent co-assembly of the stickers. To illustrate their applicative potential, we show that these Janus nanorods can efficiently stabilize oil-in-water emulsions