Jérémy Brassinne

Polymer Gels Constructed Through Metal–Ligand Coordination

In the past few years, combining supramolecular and macromolecular chemistries has become of great interest to yield dynamic and responsive assemblies with self-restructuring abilities. Among them, polymer networks, that are held together by one or a combination of supramolecular interactions, offer new possibilities to scientists for the creation of artificial materials with self-healing properties. In particular, incorporating coordination complexes into polymeric architectures opens up the possibility of imparting the physicochemical properties of both partners to the resulting material. Here, recent achievements in the field of supramolecular gels that are formed via self-assembly of oligo- and polymeric units through reversible metal–ligand interactions are reviewed. The different strategies and routes for the elaboration of those materials are reported as well as the properties that the coordination centers confer to the supramolecular assemblies.

Chemically anchored liquid-PEO based block copolymer electrolytes for solid-state lithium-ion batteries

Solid-state electrolytes are being considered the keystone element for the development of safer all-solid-state lithium-ion batteries. While poly(ethylene oxide) (PEO) solid-state polymer electrolytes are known to support a Li+ flux, satisfying conductivities are reached only above the melting point of the PEO crystallites (>65 °C) rendering PEO unpractical. Herein, by means of block-copolymer engineering, we design a mechanically clamped liquid-PEO electrolyte that combines the high ionic conductivity of a low molecular mass PEO while retaining the dimensional integrity of a solid material. Attractive ionic conductivities of about 0.01 mS cm−1 are attained at room temperature without compromising mechanical properties. The electrolyte shows a wide electrochemical stability window and help in building a stable interface with lithium metal. Competitive performances are attained when integrating the developed materials into operational/functional prototype batteries highlighting the provided potential.

Metallo-supramolecular hydrogels based on copolymers bearing terpyridine side-chain ligands

A well-defined amphiphilic poly(triethyleneglycol methylether methacrylate)-block-polystyrene (PTEGMA-b-PS) block copolymer with terpyridine groups randomly distributed within the water-soluble block has been sequentially synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Its self-assembly into micellar structures was analyzed in dilute aqueous solution by dynamic light scattering measurements (DLS). Metallo-supramolecular hydrogels were obtained after the addition of Ni(II) ions to either the precursor PTEGMA homopolymer solution or the PTEGMA-b-PS micellar solution. The PTEGMA-b-PS micelles formed gels at a much lower concentration than the corresponding PTEGMA homopolymer, thus evidencing the influence of the hydrophobic PS block on the critical gelation concentration. The mechanical properties of both hydrogels were finally investigated by rotational rheometry.

Tuning micellar morphology and rheological behaviour of metallo-supramolecular micellar gels

Well-defined polystyrene-block-poly(tert-butylacrylate) diblock copolymers end-functionalized by a terpyridine ligand (PS-b-PtBA-[) were synthesized by nitroxide mediated polymerization (NMP) in the presence of an initiator bearing a terpyridine moiety. These materials were then hierarchically organized over two levels of self-assembly to yield metallo-supramolecular micellar gels. The first level of self-assembly is the formation of micelles in the dilute regime. Spherical or cylindrical micelles were obtained depending on the block copolymer composition as well as the method of preparation. The second level of self-assembly was triggered upon addition of Ni(II) ions to the concentrated micellar solutions. Rotational rheometry was used to probe the impact of the micellar morphology and the presence of a co-solvent on the mechanical properties of the gel.

Revealing the supramolecular nature of side-chain terpyridine-functionalized polymer networks

Nowadays, finely controlling the mechanical properties of polymeric materials is possible by incorporating supramolecular motifs into their architecture. In this context, the synthesis of a side-chain terpyridine-functionalized poly(2-(dimethylamino)ethyl methacrylate) is reported via reversible addition-fragmentation chain transfer polymerization. By addition of transition metal ions, concentrated aqueous solutions of this polymer turn into metallo-supramolecular hydrogels whose dynamic mechanical properties are investigated by rotational rheometry. Hence, the possibility for the material to relax mechanical constrains via dissociation of transient cross-links is brought into light. In addition, the complex phenomena occurring under large oscillatory shear are interpreted in the context of transient networks.

Precise Control over the Rheological Behavior of Associating Stimuli-Responsive Block Copolymer Gels

“Smart” materials have considerably evolved over the last few years for specific applications. They rely on intelligent macromolecules or (supra-)molecular motifs to adapt their structure and properties in response to external triggers. Here, a supramolecular stimuli-responsive polymer gel is constructed from heterotelechelic double hydrophilic block copolymers that incorporate thermo-responsive sequences. These macromolecular building units are synthesized via a three-step controlled radical copolymerization and then hierarchically assembled to yield coordination micellar hydrogels. The dynamic mechanical properties of this particular class of materials are studied in shear flow and finely tuned via temperature changes. Notably, rheological experiments show that structurally reinforcing the micellar network nodes leads to precise tuning of the viscoelastic response and yield behavior of the material. Hence, they constitute promising candidates for specific applications, such as mechano-sensors.

One-pot synthesis of electro-active polymer gels via Cu(0)-mediated radical polymerization and click chemistry

Recently, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) has attracted intensive attention for energy storage applications. Organic radical batteries built with this polymer display high power performance. However, the solubility of PTMA in commercial electrolytes shortens the lifespan and the overall performance of the battery. To circumvent this issue, we propose to immobilize PTMA in a three-dimensional network. Indeed, an electrolyte swollen network (gel) enables a good ionic diffusion and brings good mechanical properties to the cathodic material. Here we report on the synthesis of PTMA gels by a combination of Cu(0)-mediated reversible-deactivation radical polymerization and copper-catalyzed azide–alkyne cycloaddition (CuAAC). The structure of the accordingly obtained gels is characterized by NMR, SEC and FTIR and the mechanical properties of these materials are studied by rheology. Finally, their electrochemical performances are studied in the context of organic radical batteries.

Synthesis and self-assembly of terpyridine end-capped poly(N-isopropylacrylamide)-block-poly(2-(dimethylamino)ethyl methacrylate) diblock copolymers

At the basis of smart self-assembled materials are lying small building blocks that can hierarchically assemble in response to stimuli, e.g., temperature or chemical species. In this context, the synthesis of terpyridine end-capped poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N-isopropylacrylamide) diblock copolymers via controlled radical copolymerization is reported here. The self-assembly of those copolymers is investigated in dilute aqueous solutions while varying temperature or adding transition metal ions, respectively, leading to the formation of micellar nanostructures or metallosupramolecular triblock copolymers.

Control over the assembly and rheology of supramolecular networks via multi-responsive double hydrophilic copolymers

Stimuli-responsive double hydrophilic diblock copolymers have been prepared that consist of poly(N-isopropylacrylamide)-block-poly(2-(dimethylamino)ethyl methacrylate) sequences terminated by a terpyridine ligand. These building blocks are assembled in aqueous media in a stepwise manner, by first forming metallo-supramolecular ABA triblock copolymers and then gels by thermo-induced micellar aggregation. This study sheds light on the subtle interplay that exists between the responsive behaviour of the core and corona forming blocks. Due to the intrinsic sensitivity of the constituting polymer chains and the non-covalent interactions between them, supramolecular gels respond to specific external triggers. These stimuli allow the manipulation of numerous rheological aspects of the assembled materials, including network formation and dynamics. Interestingly, an independent control over the network formation and dynamics is notably achieved via an appropriate choice of the metal ions and of the length of the associating block. By playing with the architecture of the associating copolymers and the nature of the metal ions, this work further demonstrates the possibility to build materials possessing either a mono or dual relaxation mechanism via a unique approach.

Mechanochemical Synthesis of PEDOT:PSS Hydrogels for Aqueous Formulation of Li-Ion Battery Electrodes

Water-soluble binders can enable greener and cost-effective Li-ion battery manufacturing by eliminating the standard fluorine-based formulations and associated organic solvents. The issue with water-based dispersions, however, remains the difficulty in stabilizing them, requiring additional processing complexity. Herein, we show that mechanochemical conversion of a regular poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) water-based dispersion produces a hydrogel that meets all the requirements as binder for lithium-ion battery electrode manufacture. We particularly highlight the suitable slurry rheology, improved adhesion, intrinsic electrical conductivity, large potential stability window and limited corrosion of metal current collectors and active electrode materials, compared to standard binder or regular PEDOT:PSS solution-based processing. When incorporating the active materials, conductive carbon and additives with PEDOT:PSS, the mechanochemical processing induces simultaneous binder gelation and fine mixing of the components. The formed slurries are stable, show no phase segregation when stored for months, and produce highly uniform thin (25 μm) to very thick (500 μm) films in a single coating step, with no material segregation even upon slow drying. In conjunction with PEDOT:PSS hydrogels, technologically relevant materials including silicon, tin, and graphite negative electrodes as well as LiCoO2, LiMn2O4, LiFePO4, and carbon-sulfur positive electrodes show superior cycling stability and power-rate performances compared to standard binder formulation, while significantly simplifying the aqueous-based electrode assembly.