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.
We report the first mass spectrometric analysis of poly(ionic liquid)s (PILs) containing weakly coordinating anions introduced by a fast, simple, and quantitative postmodification method on the example of the hydrophilic, well‐defined poly(vinylbenzylpyridinium chloride) p([VBPy]Cl) species, analyzed with an in‐source collision induced dissociation‐Orbitrap mass spectrometry (MS) protocol. Using the MS approach allows for the precise structural elucidation of ion‐exchanged p([VBPy]Cl) utilizing AgX (X = NO3−, CF3CO2−, BF4−) salts. The anion exchange is shown to be quantitative – without observing residual chlorinated PIL – on rapid time scales, using only filtration as a standard procedure during sample preparation. In addition, the influence of weakly coordinating anions on the ionization behavior of PILs is studied in detail.
The synthesis of poly(ionic liquid) (PIL) nanoparticles grafted with a poly(N‐isopropyl acrylamide) (PNIPAM) brush shell is reported, which shows responsiveness to temperature and ionic strength in an aqueous solution. The PIL nanoparticles are first prepared via aqueous dispersion polymerization of a vinyl imidazolium‐based ionic liquid monomer, which is purposely designed to bear a distal atom transfer radical polymerization (ATRP) initiating group attached to the long alkyl chain via esterification reaction. The size of the PIL nanoparticles can be readily tuned from 25 to 120 nm by polymerization at different monomer concentrations. PNIPAM brushes are successfully grafted from the surface of the poly(ionic liquid) nanoparticles via ATRP. The stimuli‐responsive behavior of the poly(ionic liquid) nanoparticles grafted with PNIPAM brushes (NP‐g‐PNIPAM) in aqueous phase is studied in detail. Enhanced colloidal stability of the NP‐g‐PNIPAM brush particles at high ionic strength compared to pure PIL nanoparticles at room temperature is achieved. Above the lower critical solution temperature (LCST) of PNIPAM, the brush particles remain stable, but a decrease in hydrodynamic radius due to the collapse of the PNIPAM brush onto the PIL nanoparticle surface is observed.
The controlled folding of a single polymer chain is for the first time realized by metal‐ complexation. α,ω‐Bromine functional linear polymers are prepared via activators regenerated by electron transfer (ARGET) ATRP (,SEC = 5900 g mol−1, Đ = 1.07 and 12 000 g mol−1, Đ = 1.06) and the end groups of the polymers are subsequently converted to azide functionalities. A copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction is carried out in the presence of a novel triphenylphosphine ligand and the polymers to afford homotelechelic bis‐triphenylphosphine polymeric‐macroligands (MLs) (,SEC = 6600 g mol−1, Đ = 1.07, and 12 800 g mol−1, Đ = 1.06). Single‐chain metal complexes (SCMCs) are formed in the presence of Pd(II) ions in highly diluted solution at ambient temperature. The results derived via 1H and 31P{1H} NMR experiments, SEC, and DLS unambiguously evidence the efficient formation of SCMCs via metal ligand complexation.
The developments in membranes based on tailored block copolymers are reported with an emphasis on isoporous membranes. These membranes can be prepared in different geometries, namely flat sheets and hollow fibers. They display narrow pore size distributions due to their formation by self‐assembly. The preparation of these membranes and possibilities to further functionalize such membranes will be discussed. Different ways to control the pore size will be addressed, and the potential of block copolymer blends to fabricate membranes with tailored pore sizes will be shown.
Novel polysulfone membranes with bunch‐like tertiary amine groups are synthesized with high ion selectivity and outstanding chemical stability for vanadium redox flow batteries (VRFBs). The bunch‐like tertiary amine groups simultaneously act as an ionic conductor for proton hopping and vanadium ion transport obstacles. The performance of the membrane is tuned via controlling the grafting degree of the chloromethylated polysulfone. The results show that membranes show increasing proton over vanadium ion (σ/p ) selectivity with increasing functional tertiary groups. VRFBs assembled with the prepared membranes demonstrate an impressive Coulombic efficiency of 98.9% and energy efficiency of 90.9% at a current density of 50 mA cm−2. Furthermore, the prepared membrane reported in this work shows excellent stability in 1 m VO2+ solution at 35 °C over 240 h. Overall, the synthesized polymers provide a new insight into the design of high‐performance membranes toward VRFB applications.
An alkyne‐functionalized ruthenium(II) bis‐terpyridine complex is directly copolymerized with phenylacetylene by alkyne polymerization. The polymer is characterized by size‐exclusion chromatography (SEC), 1H NMR spectroscopy, cyclic voltammetry (CV) measurements, and thermal analysis. The photophysical properties of the polymer are studied by UV–vis absorption spectroscopy. In addition, spectro‐electrochemical measurements are carried out. Time‐resolved luminescence lifetime decay curves show an enhanced lifetime of the metal complex attached to the conjugated polymer backbone compared with the Ru(tpy)22+ model complex.
Polydopamine‐based coatings are fabricated via an electric field‐accelerating and ‐directing codeposition process of polydopamine with charged polymers such as polycations, polyanions, and polyzwitterions. The coatings are uniform and smooth on various substrates, especially on those adhesion‐resistant materials including poly(vinylidene fluoride) and poly(tetrafluoroethylene) membranes. Moreover, this electric field‐directed deposition method can be applied to facilely prepare Janus membranes with asymmetric chemistry and wettability.
The synthesis of an ambipolar π‐conjugated copolymer consisting of alternating diketopyrrolopyrrole and tetrafluorobenzene via direct arylation polymerization (DAP) is reported. Two different combinations of monomers are investigated under various catalytic conditions for DAP. The target polymer obtained under an optimized catalytic condition shows minimal structural defects, a number‐average molecular weight of 33.2 kDa, and balanced electron and hole mobility of 1 × 10−2 cm2 V−1 S−1 in the organic field‐effect transistors fabricated and tested under ambient conditions.
Metal‐containing polymer hydrogels have attracted increasing interest in recent years due to their outstanding properties such as biocompatibility, recoverability, self‐healing, and/or redox activity. In this short review, methods for the preparation of metal‐containing polymer hydrogels are introduced and an overview of these hydrogels with various functionalities is given. It is hoped that this short update can stimulate innovative ideas to promote the research of metal‐containing hydrogels in the communities.
Sodium alginate (SA), acting as a trypsin inhibitor by means of electrostatic interaction, is studied. The half‐maximal inhibitory concentration (IC50 = 0.05 μg mL−1) of this natural anionic polymer is about 400 times lower than that of commercial soybean trypsin inhibitor (STI). Unlike the Ca2+‐deprivation mechanisms, its inhibition may be attributed to preventing the trypsin active site (TAS) from accessing the macromolecular substrates instead of denaturing it. SA is an efficient, innocuous, and cost‐effective inhibitory excipient that can be conveniently used in many peptide and protein dosage formulations.
Hierarchical self‐assembly of transient composite hydrogels is demonstrated through a two‐step, orthogonal strategy using nanoparticle tectons interconnected through metal–ligand coordination complexes. The resulting materials are highly tunable with moduli and viscosities spanning many orders of magnitude, and show promising self‐healing properties, while maintaining complete optical transparency.
Layer‐by‐layer (LbL) assembly has emerged as the leading non‐vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide‐based barrier films. This Feature Article is a mini‐review of LbL‐based multilayer thin films with a ‘nanobrick wall’ microstructure comprising polymeric mortar and nanoplatelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water‐based thin films exhibit oxygen transmission rates below 5 × 10‐3 cm3 m‐2 day‐1 atm‐1 and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake‐filled polymers are briefly reviewed.
Stimuli‐responsive poly(N‐isopropylacrylamide) nanogel with covalently labeled rhodamine B urea derivatives (P(NIPAM‐co‐RhBUA)) is utilized as a sensitive fluorescent probe for Cr3+ in aqueous solution, and its thermo‐induced tunable detection capacity is investigated. At 20 °C, non‐fluorescent nanogel can selectively bind with Cr3+ over some other metal ions, leading to prominent fluorescence OFF–ON switching due to the recognition of RhBUA with Cr3+. Upon heating above the phase transition temperature, enhanced fluorescence intensity is observed (≈61‐fold increase at 45 °C) for the nanogel in the presence of Cr3+, accompanied with an improved detection sensitivity, which suggest that hydrophobic microenvironment generated in the collapsed nanogel plays an active role for their detection performance.
The attempts to mediate iterative RAFT polymerization of ionic monomers through visible light irradiation in water at 20 °C is reported, in which complete conversions are attained in several tens of minutes and the propagation suspends/restarts immediately for multiple times on cycling irradiation. This technique suits the one‐pot synthesis of NH2/imidazole‐based polymers with tuned structures from homo to random, block, random‐block, and block‐random‐block, thus is robust and promising to control the sequence of the ionized water‐soluble reactive copolymers.
Control over morphology and porosity of supramolecular complexed polylactide (PLA) microparticles can be achieved by manipulation of the supramolecular interactions between their constituent polymeric building blocks. It is expected that such modular systems are ideal candidates to serve as degradable delivery carriers. In view of this goal, this study reports about a modular fabrication of biodegradable microparticles from terpyridine (TPy) and bisterpyridine (bisTPy) end‐functionalized PLAs that can be transiently extended by chain association through differently strong complexation to three metal cations: Ni2+, Co2+, or Fe2+. Further influence on the morphology of the particles can be exerted by hydrogen‐bonding association of enantiomeric l ‐ and d ‐PLA chains in the form of stereocomplexes. Both effects cause different stabilization of phase‐separating TPy and bisTPy PLA micrograins in a process of droplet‐based microfluidic particle templating, resulting in different forms of microparticle porosity. If the resulting particles are tailored such to be highly porous, they exhibit a faster release of a model drug, (S)‐(+)‐4‐(3‐amino‐pyrrolidino)‐7‐nitrobenzo‐furazan, than if they have smooth surfaces. As a result, control over the synthetic parameters, and hence, the particle porosity, can be used to tune the release profiles of drugs from the PLA microspheres.
The direct synthesis of structurally well‐defined protic polymeric ionic liquid (PIL) with controlled molecular weight and molecular weight distribution is examined using N,N‐diethyl‐N‐(2‐methacryloylethyl) ammonium bis(tri‐fluoromethylsulfonyl)imide (DEMH‐TFSI) as a monomer. Three polymerization methods, namely, atom transfer radical polymerization (ATRP), activators regenerated by electron transfer (ARGET)‐ATRP, and organotellurium‐mediated living radical polymerization (TERP) are employed in this study. While the polymerization by ATRP is slow and does not reach high monomer conversion that under ARGET‐ATRP and TERP proceeds smoothly and affords structurally well‐defined poly(DEMH‐TFSI)s. TERP is especially efficient for the control and poly(DEMH‐TFSI)s with low to high molecular weights ( = 49 100–392 500) and narrow molecular weight distributions (/ = 1.17–1.46) are obtained. These results represent the first example of synthesis of a structurally well‐defined protic, ammonium PIL by direct polymerization of the protic ionic liquid monomer. The polymerization of N,N‐diethyl‐N‐(2‐methacryloylethyl)‐N‐methylammonium bis(trifluoromethylsulfonyl)imide (DEMM‐TFSI), which possesses a quaternary ammonium salt, also proceeds in a highly controlled manner under TERP conditions. A diblock copolymer, polystyrene‐block‐poly(DEMH‐TFSI), is also successfully synthesized by TERP.
Molecular bottle‐brush functionalized single‐walled carbon nanotubes (SWCNTs) with superior dispersibility in water are prepared by a one‐pot synthetic methodology. Elongating the main‐chain and side‐chain length of molecular bottle‐brushes can further increase SWCNT dispersibility. They show significant enhancement of SWCNT dispersibility up to four times higher than those of linear molecular functionalized SWCNTs.
Temperature‐triggered switchable nanofibrous membranes are successfully fabricated from a mixture of cellulose acetate (CA) and poly(N‐isopropylacrylamide) (PNIPAM) by employing a single‐step direct electrospinning process. These hybrid CA‐PNIPAM membranes demonstrate the ability to switch between two wetting states viz. superhydrophilic to highly hydrophobic states upon increasing the temperature. At room temperature (23 °C) CA‐PNIPAM nanofibrous membranes exhibit superhydrophilicity, while at elevated temperature (40 °C) the membranes demonstrate hydrophobicity with a static water contact angle greater than 130°. Furthermore, the results here demonstrate that the degree of hydrophobicity of the membranes can be controlled by adjusting the ratio of PNIPAM in the CA‐PNIPAM mixture.
An acceleration effect and selective monomer addition during RAFT copolymerization of the oppositely‐charged ionic monomers in dilute aqueous solution at 25 °C are reported. The reaction is conducted using a non‐ionic water‐soluble polymer as a macromolecular chain transfer agent under visible light irradiation. A fast iterative polymerization can be induced, even in dilute solution, by the favorable ionic interactions and in situ self‐assembly of zwitterionic growing chains. Selelctive monomer addition is achieved in the statistical copolymerization due to the ion‐pairing of the oppositely‐charged monomers, such as precisely the same reaction rates at a 1:1 of monomer ratio, otherwise a faster reaction of the minor monomer component over the major one. These behaviors open up an avenue towards the rapid synthesis of sequence‐controlled zwitterionic polyelectrolytes that can satisfy the demands of emerging biological applications.
