Jiayin Yuan

Water-soluble organo-silica hybrid nanowires.

There has been growing interest in the past decade in one-dimensional (1D) nanostructures, such as nanowires, nanotubes or nanorods, owing to their size-dependent optical and electronic properties and their potential application as building blocks, interconnects and functional components for assembling nanodevices. Significant progress has been made; however, the strict control of the distinctive geometry at extremely small size for 1D structures remains a great challenge in this field. The anisotropic nature of cylindrical polymer brushes has been applied to template 1D nanostructured materials, such as metal, semiconductor or magnetic nanowires. Here, by constructing the cylindrical polymer brushes themselves with a precursor-containing monomer, we successfully synthesized hybrid nanowires with a silsesquioxane core and a shell made up from oligo(ethylene glycol) methacrylate units, which are soluble in water and many organic solvents. The length and diameter of these rigid wires are tunable by the degrees of polymerization of both the backbone and the side chain. They show lyotropic liquid-crystalline behaviour and can be pyrolysed to silica nanowires. This approach provides a route to the controlled fabrication of inorganic or hybrid silica nanostructures by living polymerization techniques.

A pillar[5]arene/imidazolium [2]rotaxane: solvent- and thermo-driven molecular motions and supramolecular gel formation

Based on the pillar[5]arene/imidazolium recognition motif, a [2]rotaxane was effectively prepared. Solvent/temperature triggered molecular motions of the pillar[5]arene ring on the imidazolium axle were successfully realized. By comparison of proton NMR spectra of the [2]rotaxane in different solvents, we found that if we increased the solvent polarity, the pillar[5]arene ring gradually moved away from the imidazolium part. In DMSO, we also could adjust the binding site of the pillar[5]arene ring by changing the temperature. Furthermore, in DMSO, the [2]rotaxane self-assembled to form a supramolecular gel, which showed multiple stimuli-responsiveness.

Poly(ionic liquid) Complex with Spontaneous Micro-/Mesoporosity: Template-Free Synthesis and Application as Catalyst Support

A facile, template-free synthetic route is reported toward poly(ionic liquid) complexes (PILCs) which for the first time exhibit stable micro-/mesoporous structure. This is accomplished via in situ ionic complexation between imidazolium-based PILs and poly(acrylic acid) in various alkaline organic solvents. The PILC can be highly loaded with copper salts and can be used as a catalytic support for effective aerobic oxidation of activated hydrocarbons under mild conditions.

25th Anniversary Article: “Cooking Carbon with Salt”: Carbon Materials and Carbonaceous Frameworks from Ionic Liquids and Poly(ionic liquid)s

This review surveys recent work on the use of ionic liquids (ILs) and polymerized ionic liquids (PILs) as precursors to synthesize functional carbon materials. As solvents or educts with negligible vapour pressure, these systems enable simple processing, composition, and structural control of the resulting carbons under rather simple and green synthesis conditions. Recent applications of the resulting nanocarbons across a multitude of fields, such as fuel cells, energy storage in batteries and supercapacitors, catalysis, separation, and sorption materials are highlighted.

Hierarchically Structured Nanoporous Poly(Ionic Liquid) Membranes: Facile Preparation and Application in Fiber-Optic pH Sensing

Nanoporous polyelectrolyte membranes with hierarchical and unique pore architectures can be readily made via electrostatic complexation between imidazolium-based poly(ionic liquid)s and poly(acrylic acid) in a variety of morphologies. Coating the membrane onto the surface of an optical fiber resulted in a device with high pH-sensing performance in terms of the response rate and the sensitivity, due to the charge and porous nature of the membrane layer.

Improving Hydrothermal Carbonization by Using Poly(ionic liquid)s

Pores for thought: Porous nitrogen-doped carbon materials (HTC Carbon with PILs) composed of spherical nanoparticles, and also those with Au-Pd core-shell nanoparticles embedded (Au-Pd@N-Carbon) were synthesized. These materials can be prepared from sugars by hydrothermal carbonization (160-200 °C) in the presence of poly(ionic liquid)s (PILs), which act as a stabilizer, pore-generating agent, and nitrogen source.

LCST‐Type Phase Behavior Induced by Pillar[5]arene/Ionic Liquid Host–Guest Complexation

The host-guest complex of dipropoxypillar[5]arene and an ionic liquid 1,3-dimethylimidazolium iodide is found to exhibit a lower critical solution temperature (LCST)-type phase transition in chloroform. This LCST-type phase behavior can be conveniently modulated by experimental parameters and can be easily combined with the ionic liquid for potential application in product and educt separation.

Undulated Multicompartment Cylinders by the Controlled and Directed Stacking of Polymer Micelles with a Compartmentalized Corona

Like a bamboo rod: Long, bamboo-like undulated cylinders with distinct branch points and end groups (see picture) were obtained by the stacking of block terpolymer micelles that contain a fluorinated polybutadiene core and a compartmentalized corona of poly(4-tert-butoxystyrene) and poly(tert-butyl methacrylate). Stacking of the polymer micelles, which can be reversed, occurred when the solvent was changed from dioxane to ethanol.

Thermoresponsive polyelectrolytes derived from ionic liquids

Ionic liquid (IL)-based polyelectrolytes (PILs), referred to as polymeric ILs, polymerised ILs, or poly(IL)s are a new subclass of polymer materials. They are distinct from conventional polyelectrolytes due to their unique physico-chemical properties originated from a dense packing of ILs in the macromolecular architecture. Mixtures of PILs and solvents, in particular, water have attracted a great deal of interest especially in terms of their compatibilities depending on temperature, namely, thermoresponsiveness of PIL/solvent mixtures. Apart from static compatibility, such as the compatibility of PILs with solvents, which do not change largely by a temperature change, there are mainly two types of dynamic phase changes, an upper critical solution temperature (UCST)- and a lower critical solution temperature (LCST)-type phase behaviour. Some PILs dissolved in solvents homogenise upon heating; this behaviour is classified as UCST behaviour. On the other hand, only in the last two years have PIL/water mixtures with LCST been discovered. This article summarises rapidly growing studies on the design of thermoresponsive PIL systems with water or organic solvents. The hydrophobicity/hydrophilicity balance of the starting IL monomers features the phase behaviour of the resulting polyelectrolytes, and some IL monomers that show thermoresponsive phase behaviour in solvents were found to maintain their thermoresponsiveness even after the polymerisation. Based on their unique combination of properties derived from an ionic and thermoresponsive nature, these thermoresponsive PILs will attract considerable interest, and their wide applications are expected in the fields of separation, sensing and desalination.

Sensing Solvents with Ultrasensitive Porous Poly(ionic liquid) Actuators

We introduced a new concept for fabricating solvent stimulus polymer actuators with unprecedented sensitivity and accuracy. This was accomplished by integrating porous architectures and electrostatic complexation gradients in a poly(ionic liquid) membrane that bears ionic liquid species for solvent sorption. In contact with 1.5 mol% of acetone molecules in water, the actuator membrane (1 mm x 20 mm x 30 um) bent into a closed loop. While the interaction between solvents and the polymer drives the actuation, the continuous gradient in complexation degree combined with the porous architecture optimizes the actuation, giving it a high sensitivity and even the ability to discriminate butanol solvent isomers. The membrane is also capable of cooperative actuation. The design concept is easy to implement and applicable to other polyelectrolyte systems, which substantially underpins their potentials in smart and sensitive signaling microrobotics/devices.