Ultrasensitive polymer actuators are prepared, which can sense a very small amount (0.25 mol%) of acetone solvent in water, discriminate butanol isomers, and perform cooperative actuation.

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Highly charged porous polymer membranes with adjustable pore size and gradient pore structure along the membrane cross-section were prepared by ammonia-triggered electrostatic complexation between an imidazolium-based cationic poly(ionic liquid) (PIL) and multivalent benzoic acid derivatives. The PIL and the acid compound were first dissolved homogeneously in DMSO, cast into a thin film onto a glass plate, dried, and finally immersed into an aqueous ammonia solution. The diffusion of ammonia from the top to the bottom into the film neutralized the acid and introduced the gradient pore structure and in situ electrostatic cross-linking to fix the pores. The pore size and its distribution of the membranes were found controllable in terms of the multivalency of the acids, the imidazolium/carboxylate ratio, and the nature of the PIL counteranion.

Porous polymer membranes made via electrostatic complexation are fabricated from a water-soluble poly(ionic liquid) (PIL) for the first time. The porous structure is formed as a consequence of simultaneous phase separation of the PIL and ionic complexation with an acid, which occurred in a basic solution of a nonsolvent for the PIL. These membranes have a stimuli-responsive porosity, with open and closed pores in isopropanol and in water, respectively. This property is quantitatively demonstrated in filtration experiments, where water is passing much slower through the membranes than isopropanol.

Porous poly(ionic liquid) membranes that were prepared via electrostatic cross-linking were subsequently covalently cross-linked via formation of a 1,3,5-triazine network. The additional covalent cross-links do not affect the pore size and pore size distribution of the membranes and stabilize them towards salt solutions of high ionic strength, enabling the membranes to work in a broader environmental window.Porous polymer membranes are a field of growing interest both in academia and industry. [1][2][3][4][5][6][7] Such membranes are composed of polyelectrolytes, where the charge character of the polymer affords a wide range of applications such as sensing, separation and catalysis. [8][9][10][11][12][13][14][15][16][17][18][19] From a structural point of view, the porous morphology of the membrane is important, especially considering the pore size, pore size distribution, and pore stability that dictate the transport behaviour of the membranes. 20In order to generate porosity inside polyelectrolyte membranes, there have been several strategies developed, such as layer-by-layer deposition, templating, etc. It is also possible to take advantage of interpolyelectrolyte complexation between two oppositely charged polyelectrolytes (or a polyelectrolyte and an oppositely charged species) to construct porous polyelectrolyte membranes if a phaseseparation process can arise simultaneously. 8,21 Our group previously exploited this complexation technique to create porous membranes based on two components, (i.e. an imidazolium poly(ionic liquid) (PIL), which is a polyelectrolyte built up from ionic liquid (IL) monomers, 22 and a multiacid compound that is usually organic compounds with multiple carboxylic acid units or poly(acrylic acid)). [23][24][25] These PIL membranes are versatile because by changing the IL moiety, its polymer characteristics, or the multiacid type that electrostatically cross-links the PIL, it is possible to confer different pore size to target different separation or transport applications. [25][26][27][28][29] Nevertheless, the first generation of porous PIL membranes suffered from a stability issue, as the interpolyelectrolyte complex membrane is ionic in nature and in a highly ionic environment undergoes partial, if not full, dissociation. This instability issue restricts the porous PIL membranes to be used in the absence of liquid electrolytes either in aqueous or organic solution. To address this issue, an easy strategy is to introduce covalent cross-links in addition to the existing electrostatic, noncovalent ones. This concept has already been exploited in covalently cross-linked amino-and carboxylat-containing polymer chains, forming an amide linkage for a better control over the swelling properties of the resulting membranes. [30][31][32] Taking advantage of the "click-"chemistry represents another way to covalently cross-link membranes forming a 1,2,3-triazole ring.33 Moreover, diols have been proven to be able to covalently cross-link carboxylate groups upon ester formation. 34...