Synthesis and LCST-type phase separation behavior in organic solvents of poly(vinyl ethers) with pendant imidazolium or pyridinium salts

Thermal Responsiveness of 1,2,4-Triazolium-Based Poly(ionic liquid)s and Their Applications in Dye Extraction and Smart Switch

Triazoliums are a family of five-membered heterocyclic cations that contain three nitrogen and two carbon atoms. In contrast to the widely studied imidazolium cations, triazoliums are less explored. In terms of the chemical structure, triazolium replaces a carbon atom in the imidazolium cation ring with an electron-withdrawing nitrogen atom, which makes the triazolium more polarized. Among the many physical properties, the thermal responsiveness of triazoliums is of particular interest to us but has been rarely investigated. In this contribution, we prepared a series of 1,2,4-triazolium-based poly(ionic liquid)s (PILs) with varying alkyl substituents and counteranions and studied their thermal-responsive behavior. We found that 1,2,4-triazolim-based PILs with a polymeric backbone structure similar to that of polyimidazoliums exhibited opposite thermal phase transition processes in solvents. For example, methyl-substituted 1,2,4-triazolium-based PILs exhibited an upper-critical-solution-temperature (UCST)-type phase transition in methanol when the counterion was I- and a lower-critical-solution-temperature (LCST)-type phase transition in acetone when the counterion was PF6 -. The thermal responsiveness was reversible and concentration-dependent. Interestingly, the thermal response of 1,2,4-triazolim-based PILs could be retained in the organogel form, which was applied in the pretreatment of anion-containing organic waste liquids and temperature-controlled "smart" switches.

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.

Precise synthesis of amphiphilic diblock copolymers consisting of various ionic liquid-type segments and their influence on physical gelation behavior in water

Appropriately designed amphiphilic diblock vinyl ether (VE) copolymers consisting of an ionic liquid-type segment and a hydrophobic segment were demonstrated to undergo physical gelation in water at extremely low concentrations. The precursor diblock copolymers were synthesized by the living cationic polymerization of 2-chloroethyl VE with a hydrophobic VE through an appropriately designed initiating system such as optimized temperature and catalyst. A relatively high temperature such as 20 °C was important for controlled polymerization of octadecyl VE. Ionic liquid moieties with imidazolium salt structures were subsequently introduced into the side chains of the diblock copolymers via chemical modifications of the 2-chloroethyl groups. The physical gelation behavior of the obtained diblock copolymers was examined in water, with a particular focus on the influence of the hydrophobic VEs, the hydrophilicity of the counteranions and the substituents on the ionic liquid-type segments, and the length of each segment. Based on this systematic investigation, physical gelation at concentrations as low as 0.2 wt% was achieved with diblock copolymers with a suitable balance of these factors.

Amphiphilic diblock copolymers of hydrophobic and imidazolium salt-containing vinyl ethers were synthesized via living cationic polymerization. The influence of hydrophobic and the ionic-liquid moieties on physical gelation in water was examined.

Precise synthesis of UCST-type amphiphilic diblock copolymers with pendant imidazolium ionic liquid segments and their thermosensitive physical gelation at extremely low concentrations in water

UCST-type amphiphilic diblock copolymers were synthesized via living cationic polymerization and subsequent polymer reaction and they exhibited thermosensitive physical gelation behavior at an extremely low concentration in water.

Preparation and UCST-Type Phase Behaviours of Poly(γ-4-methylbenzyl-L-glutamate) Pyridinium Tetrafluoroborate Conjugates in Methanol or Water

Polymers with ionic liquid (IL) moieties can undergo thermally induced solution phase transitions by adjusting the balance of hydrophilicity and hydrophobicity between the cations and anions of the IL moieties, thus making them attractive candidates towards various applications such as separation, sensing, and biomedicine. In the present study, a series of poly(γ-4-methylbenzyl-l-glutamate) pyridinium tetrafluoroborate conjugates (P1–P4) containing various pyridinium moieties (i.e. pyridinium, 2-methylpyridinium, 3-methylpyridinium, and 4-methylpyridinium) were prepared by nucleophilic substitution between poly(γ-4-chloromethylbenzyl-l-glutamate) and pyridine or methylpyridines with different substituent positions, followed by ion-exchange reaction in the presence of NaBF4. 1H NMR spectroscopy and Fourier transform infrared spectroscopy analyses confirmed the molecular structures of P1–P4. 1H NMR analysis additionally revealed that P1–P4 showed high grafting efficiency in the range of 93–97 %. P1, P3, and P4 exhibited reversible UCST-type phase behaviours in both methanol and water, whereas P2 showed a reversible UCST-type phase behaviour in water only. Variable-temperature UV-visible spectroscopy was used to characterize the solution phase behaviours and UCST-type phase transition temperature (Tpt) values of P1–P4, which were in the range of 24.9–37.2°C in methanol (3 mg mL–1) and 40.9–55.7°C in water (10 mg mL–1). Tpt decreased significantly with decreasing polymer concentrations.

Synthesis and UCST-type phase behavior of α-helical polypeptides with Y-shaped and imidazolium pendants

UCST-type thermoresponsive polypeptides with Y-shaped and ionic liquid pendants were synthesized by a multi-step post-polymerization method.

Unexpected LCST-type phase behaviour of a poly(vinyl thiazolium) polymer in acetone

A poly(vinyl thiazolium) polymer in acetone solution exhibited an unexpected lower critical solution temperature (LCST)-type phase transition.

LCST-Type Phase Separation of Poly[poly(ethylene glycol) methyl ether methacrylate]s in Hydrofluorocarbon

Poly[poly(ethylene glycol) methyl ether methacrylate]s [poly(PEGMA)s] sharply and reversibly exhibited lower critical solution temperature (LCST)-type phase separation in 2H,3H-perfluoropentane (2HPFP). The cloud points decreased from 52 to 41 °C with increasing the PEG pendant length [-(CH₂CH₂O)_mCH₃: m = 4.5, 9, 19]. The cloud point was precisely controlled via the addition of perfluoroalkanes (e.g., perfluorooctane) to the 2HPFP solution: typically, it was inversely proportional to the amount of perfluorooctane in the mixture. The unique thermoresponsive solubility further afforded the temperature-mediated micellization of a block copolymer of PEG19MA and methyl methacrylate (MMA) in 2HPFP to uniquely give a PEG-core micelle with PMMA shell. Therefore, the LCST phase separation properties in the hydrofluorocarbon would open new vistas for thermoresponsive polymeric materials.

Thermoresponsive polyelectrolytes derived from ionic liquids

In this review we summarise recent progress on the design, properties, and potential applications of ionic liquid-derived polyelectrolytes showing thermoresponsive phase behaviour after mixing with water or other organic solvents.

Synthesis and characterization of glycidyl-polymer-based poly(ionic liquid)s: highly designable polyelectrolytes with a poly(ethylene glycol) main chain

Glycidyl-polymer-based poly(ionic liquid)s with different spacers and ionic moieties were synthesized by click functionalization of a glycidyl azide polymer.