All Poly(ionic liquid)-Based Block Copolymers by Sequential Controlled Radical Copolymerization of Vinylimidazolium Monomers

Solution and Film Self-Assembly Behavior of a Block Copolymer Composed of a Poly(ionic Liquid) and a Stimuli-Responsive Weak Polyelectrolyte

Cu(0)-mediated atom transfer radical polymerization was used to synthesize a poly(ionic liquid), poly[4-vinylbenzyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] (PVBBImTf2N), a stimuli-responsive polyelectrolyte, poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA), and a novel block copolymer formed from these two polymers. The synthesis of the block copolymer, poly[2-(dimethylamino) ethyl methacrylate]-block-[poly(4-vinylbenzyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] (PDMAEMA-b-PVBBImTf2N), was examined to evaluate the control of "livingness" polymerization, as indicated by molecular weight, characterizations of degree of polymerization, and 1HNMR spectroscopy. 2D DOSY NMR measurements revealed the successful formation of block copolymer and the connection between the two polymer blocks. PDMAEMA-b-PVBBImTf2N was further characterized for supramolecular interactions in both the bulk and solution states through FTIR and 1H NMR spectroscopies. While the block copolymer demonstrated similar intermolecular behavior to the PIL homopolymer in the bulk state as indicated by FTIR, hydrogen bonding and counterion interactions in solution were observed in polar organic solvent through 1H NMR measurements. The DLS characterization revealed that the PDMAEMA-b-PVBBImTf2N block copolymer forms a network-like aggregated structure due to a combination of hydrogen bonding between the PDMAEMA and PIL group and electrostatic repulsive interactions between PIL blocks. This structure was found to collapse upon the addition of KNO3 while still maintaining hydrogen bonding interactions. AFM-IR analysis demonstrated varied morphologies, with spherical PDMAEMA in PVBBImTf2N matrix morphology exhibited in the region approaching the film center. AFM-IR further revealed signals from silica nano-contaminates, which selectively interacted with the PDMAEMA spheres, demonstrating the potential for the PDMAEMA-b-PVBBImTf2N PIL block copolymer in polymer-inorganic nanoparticle composite applications.

RAFT polymerization-induced self-assembly of poly(ionic liquids) in ethanol

Poly(ionic liquids) (PILs) exhibit better durability, processability, and mechanical stability than ionic liquids. PIL self-assembly in green solvents is a well-established strategy for preparing polyelectrolytes. Reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) has proven to be the most controllable method for synthesizing polyelectrolytes. However, there have been few reports on preparing high-order morphology PILs by RAFT-PISA. A new type of ionic monomer, 1-butyl-3-(4-vinylbenzyl)imidazolium hexafluorophosphate ([BVBIm][PF6]), was prepared from substitution reaction and ion exchange reaction of 1-butylimidazole and 4-vinylbenzyl chloride. Herein, various morphologies, including spheres, worms, and vesicles, were easily obtained via RAFT ethanolic dispersion polymerization using poly(N,N-dimethylacrylamide) (PDMA43) as the macromolecular chain transfer agent and [BVBIm][PF6] as the monomer. Dispersion polymerization kinetic experiments, dynamic light scattering, transmission electron microscopy, and differential scanning calorimetry were used to investigate the PDMA43-b-P([BVBIm][PF6]) x block nanoparticles. This efficient RAFT-PISA method for preparing functionalized PIL nano-objects with controlled morphologies represents significant progress in this field.

Dual-Cationic Poly(ionic liquid)s Carrying 1,2,4-Triazolium and Imidazolium Moieties: Synthesis and Formation of a Single-Component Porous Membrane

Both imidazolium and 1,2,4-triazolium cations are important functional moieties widely incorporated as building blocks in poly(ionic liquid)s (PILs). In a classical model, a PIL usually contains either imidazolium or 1,2,4-triazolium in its repeating unit. Herein, via exploiting the slight reactivity difference of alkyl bromide with imidazole and 1,2,4-triazole at room temperature, we synthesized dual-cationic PIL homopolymers carrying both imidazolium and 1,2,4-triazolium moieties in the same repeating unit, that is, an asymmetrically dicationic unit. We investigated their fundamental properties, for example, thermal stability and solubility, as well as their unique function in forming supramolecular porous membranes via a water-initiated phase-separation and cross-linking process. With such knowledge, we identified a water-based fabricate strategy toward air-stable porous membranes from single-component PILs. This study will enrich the design tools and chemical structure library of PILs and expand their application spectrum.

All poly(ionic liquid) block copolymer nanoparticles from antagonistic isomeric macromolecular blocks via aqueous RAFT polymerization-induced self-assembly

All-poly(ionic liquid) block copolymer nanoparticles are prepared by aqueous RAFT PISA using a couple of isomeric ionic liquid monomers leading to macromolecular building blocks with antagonistic solution behavior in water.

In Situ Preparation of Crosslinked Polymer Electrolytes for Lithium Ion Batteries: A Comparison of Monomer Systems

Solid polymer electrolytes for bipolar lithium ion batteries requiring electrochemical stability of 4.5 V vs. Li/Li+ are presented. Thus, imidazolium-containing poly(ionic liquid) (PIL) networks were prepared by crosslinking UV-photopolymerization in an in situ approach (i.e., to allow preparation directly on the electrodes used). The crosslinks in the network improve the mechanical stability of the samples, as indicated by the free-standing nature of the materials and temperature-dependent rheology measurements. The averaged mesh size calculated from rheologoical measurements varied between 1.66 nm with 10 mol% crosslinker and 4.35 nm without crosslinker. The chemical structure of the ionic liquid (IL) monomers in the network was varied to achieve the highest possible ionic conductivity. The systematic variation in three series with a number of new IL monomers offers a direct comparison of samples obtained under comparable conditions. The ionic conductivity of generation II and III PIL networks was improved by three orders of magnitude, to the range of 7.1 × 10-6 S·cm-1 at 20 °C and 2.3 × 10-4 S·cm-1 at 80 °C, compared to known poly(vinylimidazolium·TFSI) materials (generation I). The transition from linear homopolymers to networks reduces the ionic conductivity by about one order of magnitude, but allows free-standing films instead of sticky materials. The PIL networks have a much higher voltage stability than PEO with the same amount and type of conducting salt, lithium bis(trifluoromethane sulfonyl)imide (LiTFSI). GII-PIL networks are electrochemically stable up to a potential of 4.7 V vs. Li/Li+, which is crucial for a potential application as a solid electrolyte. Cycling (cyclovoltammetry and lithium plating-stripping) experiments revealed that it is possible to conduct lithium ions through the GII-polymer networks at low currents. We concluded that the synthesized PIL networks represent suitable candidates for solid-state electrolytes in lithium ion batteries or solid-state batteries.

Developing New Inexpensive Room-Temperature Ionic Liquids with High Thermal Stability and a Greener Synthetic Profile

Ionic liquids (ILs) have advantageous physical properties, which resulted in a rapid growth of research in this area in the past 15 years. One of the biggest challenges preventing the widespread use of ILs is the cost of production due to complex synthetic routes and/or expensive starting materials. Keeping in mind these industrial needs for scale-up and the desirable properties for applications in the lubrification area, here, we report the design and synthesis of four novel series of hydrophobic room-temperature ILs (RTILs) achieved from cheap and commercially available starting materials, namely, silicon-based, imidazolium-based, phosphonium-based, and monomer imidazolium-based. These syntheses were developed as expedited chemistry protocols and possess a greener synthetic profile compared to previously reported ILs of similar structures. All the RTILs were characterized by 1D NMR (¹H NMR, ¹³C NMR, ³¹P NMR, ¹⁹F NMR, and ¹¹B NMR) and 2D NMR (COSY, HSQC, and HMBC) analyses, high-resolution mass spectrometry, and chemical tests (primarily the silver nitrate test). Preliminary thermal analysis tests by thermogravimetric analysis show all novel RTILs display remarkably high thermal stabilities (386-474 °C). Differential scanning calorimetry data show low glass transitions ranging from -36 to -72 °C, which suggests good free volume and ion mobility.

Controlled synthesis of sugar-containing poly(ionic liquid)s

A facile synthetic route is reported toward sugar-containing pyridinium-based poly(ionic liquid)s (PILs) for efficient killing of bacteria.

Linear Main-Chain 1,2,4-Triazolium Poly(ionic liquid)s: Single-Step Synthesis and Stabilization of Cellulose Nanocrystals

Linear main-chain 1,2,4-triazolium-based poly(ionic liquid)s (PILs) were synthesized in this contribution. The polymerization process is experimentally very simple and involves only a single-step polycondensation of a commercially available monomer in DMSO as solvent at 120 °C. Their thermal stability and solubility were analyzed in terms of different counteranions. Due to the ease of this synthetic route, it was readily applied to graft onto sulfonated cellulose nanocrystals (CNCs) via a one-step in situ polymerization. The as-synthesized PIL@CNC hybrid colloids exhibit adaptive dispensability in water and organic solvents.

Ionic Conductivity and Assembled Structures of Imidazolium Salt-Based Block Copolymers with Thermoresponsive Segments

Ionic liquid-based block copolymers composed of ionic (solubility tunable)⁻nonionic (water-soluble and thermoresponsive) segments were synthesized to explore the relationship between ionic conductivity and assembled structures. Three block copolymers, comprising poly(N-vinylimidazolium bromide) (poly(NVI-Br)) as a hydrophilic poly(ionic liquid) segment and thermoresponsive poly(N-isopropylacrylamide) (poly(NIPAM)), having different compositions, were initially prepared by RAFT polymerization. The anion-exchange reaction of the poly(NVI-Br) in the block copolymers with lithium bis(trifluoromethanesulfonyl)imide (LiNTf₂) proceeded selectively to afford amphiphilic block copolymers composed of hydrophobic poly(NVI-NTf₂) and hydrophilic poly(NIPAM). Resulting poly(NVI-NTf₂)-b-poly(NIPAM) exhibited ionic conductivities greater than 10-3 S/cm at 90 °C and 10-4 S/cm at 25 °C, which can be tuned by the comonomer composition and addition of a molten salt. Temperature-dependent ionic conductivity and assembled structures of these block copolymers were investigated, in terms of the comonomer composition, nature of counter anion and sample preparation procedure.

Universal mass spectrometric analysis of poly(ionic liquid)s

We introduce a universal high resolution mass spectrometric method for the analysis of poly(ionic liquid)s (PILs), which belong to the most challenging polyelectrolytes from an analytical perspective, by fusing high resolution collision-induced dissociation (CID)-Orbitrap mass spectrometry (MS) with supercharging agents as well as quadrupole time-of-flight (QToF) MS. The study includes a wide array of hydrophilic halide-containing PILs, which were analyzed in negative mode. The influence of the core structures (based on imidazolium, triazolium, ammonium, phosphonium and pyridinium moieties), and variable styrene-, acrylate- and vinyl-type IL polymers on the ionization behavior is mapped in detail. Variable end group functionalities were introduced via functional chain transfer agents (CTA) in reversible addition-fragmentation chain transfer (RAFT) polymerization to study their behavior during the MS analysis. Furthermore, the demanding class of vinylimidazolium halide IL polymers was investigated. The current contribution thus introduces a new analytical technology platform for an entire polymer class.

Controlled radical polymerization and in-depth mass-spectrometric characterization of poly(ionic liquid)s and their photopatterning on surfaces

Poly(ionic liquid)s (PILs) bearing a polystyrene backbone preparedviaRAFT polymerization and their photolithographic patterning on silicon wafers is reported.

Poly(ionic liquid)s with controlled architectures and their use in the making of ionogels with high conductivity and tunable rheological properties

We describe the preparation as well as the electrochemical and mechanical properties of a series of novel well-defined poly(ionic liquids) (PILs) featuring a finely tuned cross-linking ratio.

Direct one-pot synthesis of poly(ionic liquid) nanogels by cobalt-mediated radical cross-linking copolymerization in organic or aqueous media

Nanogels of controlled kinetic chain length were synthesized by cobalt-mediated radical cross-linking copolymerization (CMRccP) involving a vinyl monomer and a divinyl cross-linker.