Anatoli Serghei

Reprocessing and Recycling of Highly Cross-Linked Ion-Conducting Networks through Transalkylation Exchanges of C–N Bonds

Exploiting exchangeable covalent bonds as dynamic cross-links recently afforded a new class of polymer materials coined as vitrimers. These permanent networks are insoluble and infusible, but the network topology can be reshuffled at high temperatures, thus enabling glasslike plastic deformation and reprocessing without depolymerization. We disclose herein the development of functional and high-value ion-conducting vitrimers that take inspiration from poly(ionic liquid)s. Tunable networks with high ionic content are obtained by the solvent- and catalyst-free polyaddition of an α-azide-ω-alkyne monomer and simultaneous alkylation of the resulting poly(1,2,3-triazole)s with a series of difunctional cross-linking agents. Temperature-induced transalkylation exchanges of C-N bonds between 1,2,3-triazolium cross-links and halide-functionalized dangling chains enable recycling and reprocessing of these highly cross-linked permanent networks. They can also be recycled by depolymerization with specific solvents able to displace the transalkylation equilibrium, and they display a great potential for applications that require solid electrolytes with excellent mechanical performances and facile processing such as supercapacitors, batteries, fuel cells, and separation membranes.

Nanofluidics Approach to Separate between Static and Kinetic Nanoconfinement Effects on the Crystallization of Polymers

Here we report a nanofluidics approach that allows one to discriminate, for the first time, between static and kinetic effects on the crystallization of polymers in 2-dimensional nanoconfinement. Nanofluidics cells designed to monitor in real time, via permittivity measurements, the flow process of polymers into cylindrical nanopores were employed to investigate the crystallization of poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) under static and under kinetic confinement conditions. A significant separation between static confinement effects and flow effects in confinement is reported. A characteristic time is deduced, to quantify the impact of flow on the crystallization process of polymers taking place under conditions of 2D geometrical nanoconfinement.

1,2,3-Triazolium-Based Epoxy-Amine Networks: Ion-Conducting Polymer Electrolytes

A diepoxy-functionalized 1,2,3-triazolium ionic liquid is synthesized in three steps and used in combination with a poly(propylene glycol) diamine to obtain ion-conducting epoxy-amine networks (EANs). The curing kinetics are followed by Fourier transform infrared spectroscopy, while the physical, mechanical, and ion-conducting properties of the resulting networks are studied by swelling experiments, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, and broadband dielectric spectroscopy. The curing kinetics and thermomechanical properties of this system are relatively similar to those of conventional DGEBA- (bisphenol A diglycidyl ether)-based EANs with low glass transition temperature (Tg = -44 and -52 °C, respectively) characteristic of rubbery polymer networks. The anhydrous ionic conductivity of the pure network at 30 °C reaches a remarkably high value of 2 × 10(-7) S cm(-1) that could be further increased to 10(-6) S cm(-1) by the addition of 10 wt% LiTFSI.

Cationic and dicationic 1,2,3-triazolium-based poly(ethylene glycol ionic liquid)s

We report the synthesis of two novel poly(ionic liquid)s having poly(ethylene glycol) main chains and side chains having either one or two 1,2,3-triazolium cations with triethylene glycol spacers and bis(trifluoromethylsulfonyl)imide counter anion(s). Both ion conducting polymers are obtained by post-polymerization sequential modifications, i.e. copper-catalyzed azide–alkyne cycloaddition and N-alkylation of the 1,2,3-triazole group(s), starting from a common poly(ethylene glycol) (PEG) having azidomethyl side groups. The structures of the obtained polymers are supported by 1H NMR spectroscopy and size exclusion chromatography (SEC). The impact of the number of 1,2,3-triazolium groups and the structure of the spacer are discussed based on solubility, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and broadband dielectric spectroscopy (BDS) measurements. The dicationic derivative has a lower glass transition temperature (Tg = −27 °C) as well as higher thermal stability (Td10 = 369 °C) and ionic conductivity (σDC ∼ 10−5 S cm−1 at 30 °C under anhydrous conditions) than the monocationic analogue.

Guar gum as biosourced building block to generate highly conductive and elastic ionogels with poly(ionic liquid) and ionic liquid

In this study, we report on the simple and straightforward preparation of ionogels arising from the addition of guar gum (a plant-based polysaccharide) in a solution of precisely-defined poly(ionic liquid) chains (PIL) in imidazolium-based ionic liquid (IL). The development of intermolecular polar interactions (mainly hydrogen bonds) and topologic chain entanglements induces the formation of physical biohybrid ionogels, whose elastic properties can be easily tuned by varying the composition (up to 30000Pa). The combined presence of guar gum and PIL confers excellent dimensional stability to the ionogels with no IL exudation combined with high thermal properties (up to 310°C). The resulting materials are shown to exhibit gel scattering profiles and high conductivities (> 10-4S/cm at 30°C). The benefit linked to the formation of guar/PIL associations in IL medium enables to find a good compromise between the mechanical cohesion and the mobility ensuring the ionic transport.

1,2,3-Triazolium-based linear ionic polyurethanes

We report the synthesis of a series of ionic polyurethanes (PUs) issued from the polyaddition of a 1,2,3-triazolium-functionalized diol monomer having a bis(trifluoromethylsulfonyl)imide counter-anion with four aliphatic, cycloaliphatic or aromatic commercial diisocyanates. The obtained polymers were characterized using 1H, 13C and 19F NMR spectroscopy, size exclusion chromatography (SEC), solubility, differential scanning calorimetry, thermogravimetric analysis, broadband dielectric spectroscopy, as well as CO2 uptake and permeability measurements. These new ionic PUs exhibit glass transition temperatures ranging from −25 to 28 °C, temperatures at 10% weight loss ranging from 307 to 320 °C, ionic conductivities at 30 °C under anhydrous conditions up to 10−6 S cm−1 and CO2 uptake of ca. 2.6 mg g−1 at 2 bars.

Two-step formation mechanism of Acetobacter cellulosic biofilm: synthesis of sparse and compact cellulose

AbstractClassical studies concerning “Acetobacter xylinum” focus on bacterial ncellulose “BC” yield and rate in broth, after a long period of incubation (7–14xa0days). Such observations do not highlight bacterial physiology in the first incubation hours and its impact on BC production. In this study, the growth of a wild strain of Acetobacter was monitored in the first incubation hours. We showed the presence of two different physiologies; nthe first extends from the incubation moment till the formation of a sparse BC. Sparse BC modifies surface viscosity, and stabilizes hydrodynamic conditions to initiate compact BC production that marks the second physiology. Two containers, of different shapes, were used to confirm our findings, one of which is a culture tube with high drift currents on the broth-air interface, and the other is a conical flask with more stable hydrodynamic conditions at the culture’s surface. We showed that Acetobacter always follows two physiologies independent of the container shape. Logistic model, FTIR, XRD and SEM analysis are used to confirm the results.n