A thermally stable 2D array of spheres and their morphology control become important for the fabrication of novel nanostructures. Here, a simple method is presented for fabrication of large‐area and well‐ordered arrays of carbonized polystyrene (PS) hollow spheres with a controlled (close‐packed or non‐close‐packed hexagonal) morphology, prepared by combining the self‐assembly of PS‐grafted silica nanoparticles, etching, electron irradiation, and subsequent thermal annealing. Fine control in the 2D or 3D nanostructure of carbon materials can open up new opportunities for high‐performance nanoscale applications that require an efficient fabrication method for preparation of the porous carbon array.
Cationic polyelectrolytes showing an upper critical solution temperature (UCST) are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization in water at a temperature well above the UCST. The polymerization is well controlled by the RAFT process, with excellent pseudo‐first‐order kinetics. The cloud point is highly dependent on the polyelectrolyte concentration, molecular weight, and presence of added electrolyte. Alkylation of a neutral polymer is also conducted to obtain polyelectrolytes with different hydrophobic groups, which are shown to increase the cloud point.
In this study, mechanically strong hydrogels are synthesized by photopolymerization of 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine, poly(ethylene glycol) methacrylate, and disulfide‐containing cross‐linker, N′N‐bis(acryloyl)cystamine. The bilayer hydrogel with distinct cross‐linking density is shown to self‐roll into a 3D tube, which could still be well reinforced by hydrogen bondings, upon exposing reductants such as 1,4‐dithio‐DL‐threitol (DTT) or L‐glutathione (GSH), because the redox‐induced cleavage of disulfide bonds results in the imbalanced internal shrinking stress between two layers. At an intracellular level of GSH, model L929 cells‐seeded bilayer gel sheet could curl up into a 3D tubular scaffold where the cells maintained good viability.
Thin, phenylboronic acid‐containing polymer coatings are potentially attractive sensory layers for a range of glucose monitoring systems. This contribution presents the synthesis and properties of glucose‐sensitive polymer brushes obtained via surface RAFT polymerization of 3‐methacrylamido phenylboronic acid (MAPBA). This synthetic strategy is attractive since it allows the controlled growth of PMAPBA brushes with film thicknesses of up to 20 nm via direct polymerization of MAPBA without the need for additional post‐polymerization modification or deprotection steps. QCM‐D sensor chips modified with a PMAPBA layer respond with a linear change in the shift of the fundamental resonance frequency over a range of physiologically relevant glucose concentrations and are insensitive toward the presence of fructose, thus validating the potential of these polymer brush films as glucose sensory thin coatings.
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.
A new and easy method of stimuli‐triggered growth and removal of a bioreducible nanoshell on nanoparticles is reported. The results show that pH or temperature could induce the aggregation of disulfide‐contained branched polymers at the surface of nanoparticles; subsequently, the aggregated polymers could undergo intermolecular disulfide exchange to cross‐link the aggregated polymers, forming a bioreducible polymer shell around nanoparticles. When these nanoparticles with a polymer shell are treated with glutathione (GSH) or d,l ‐dithiothreitol (DTT), the polymer shell could be easily removed from the nanoparticles. The potential application of this method is demonstrated by easily growing and removing a bioreducible shell from liposomes, and improvement of in vivo gene transfection activity of liposomes with a bioreducible PEG shell.
Multivalent binding is a key for many critical biological processes and unique recognition and specificity in binding enables many of different glycans and proteins to work in a great harmony within the human body. In this study, the binding kinetics of synthetic glycopolypeptides to the dendritic cell lectin DC‐SIGN and their inhibition potential for DC‐SIGN interactions with the gp120 envelope glycoprotein of HIV‐1 (gp120) are investigated.
Here, a novel method is demonstrated for the preparation of three‐arm branched microporous organic nanotube networks (TAB‐MONNs) based on molecular templating of three‐arm branched core–shell bottlebrush copolymers and Friedel–Crafts alkylation reaction. The unique three‐arm branched bottlebrush copolymers are synthesized by a combination of atom transfer radical polymerization, reversible addition‐fragmentation chain transfer polymerization, and ring‐opening polymerization techniques. In this approach, the length and diameter of branched tube units can be well‐controlled by rational molecular design. Moreover, the as‐prepared TAB‐MONNs possess a high surface area and exhibit a superior adsorption capacity for Rhodamine 6G (R6G) and p‐cresol.
Polyurethane (PU) monomer mixtures containing commercially available o‐nitrobenzyl‐based photocleavable monomers have been formulated and tested as low‐cost positive tone photoresists. The photolysis reaction is studied by UV spectroscopy. Well‐defined micropatterns on 2 μm thick photodegradable PU films are obtained using 365 nm light exposure. This strategy is also extended to improved formulations based on synthesized o‐nitrobiphenylpropyl derivatives with enhanced photochemical properties for single photon excitation and high two‐photon absorption cross‐sections. Improved pattern resolution in 2D and the capability of 3D resolution using a scanning laser at 780 nm is demonstrated. This work demonstrates the potential of PUs as readily available, versatile, and easy‐to‐use photoresist materials for low‐cost lithography applications.
A new method for fabricating hydrogels with intricate control over hierarchical 3D porosity using microfiber porogens is presented. Melt electrospinning writing of poly(ε‐caprolactone) is used to create the sacrificial template leading to hierarchical structuring consisting of pores inside the denser poly(2‐oxazoline) hydrogel mesh. This versatile approach provides new opportunities to create well‐defined multilevel control over interconnected pores with diameters in the lower micrometer range inside hydrogels with potential applications as cell scaffolds with tunable diffusion and transport of, e.g., nutrients, growth factors or therapeutics.
A simple process is developed to fabricate metallo‐supramolecular nanogels (MSNs) by the metallo‐supramolecular‐coordinated interaction between histidine and iron‐meso‐tetraphenylporphin. MSNs are composed of histidine‐modified dextran (DH) and iron‐meso‐tetraphenylporphin (Fe–Por) and exhibit excellent biocompatibility and stability. MSNs show pH responsiveness in the intracellular mildly acidic environment, which has great potential for acid‐triggered drug release delivery. In vitro drug release profiles demonstrate that the pH‐dependent disassembly of MSNs to histidine and Por results in a quicker release rate of loaded‐DOX at pH 5.3, while at pH 7.4 MSNs could hinder the release of loaded‐DOX due to the enhanced stability of MSNs.
Enzymes are attractive, “green” alternatives to chemical catalysts within the industrial sector, but their robustness to environmental conditions needs optimizing. Here, an enzyme is tagged chemically and recombinantly with a self‐assembling peptide that allows the conjugate to spontaneously assemble with pure peptide to form β‐sheet‐rich nanofibers decorated with tethered enzyme. Above a critical concentration, these fibers entangle and form a 3D hydrogel. The immobilized enzyme catalyzes chemical transformations and critically its stability is increased significantly where it retains activity after exposure to high temperatures (90 °C) and long storage times (up to 12 months).
Well‐defined ABC triblock copolymers based on two hydrophilic blocks, A and C, and a hydrophobic block B are synthesized and their self‐assembly behavior is investigated. Interestingly, at the same solvent, concentration, pH, and temperature, different shape micelles are observed, spherical and worm‐like micelles, depending on the preparation method. Specifically, spherical micelles are observed with bulk rehydration while both spherical and worm‐like micelles are observed with film rehydration.
Triptycene‐based micorporous polymer is functionalized with CO2‐philic tetrazole moieties via ZnCl2‐catalyzed post‐polymerization. Gas adsorption experiments indicate that it possesses high CO2 uptake capacity, reaching 134 cm3 g−1 (26.5 wt%) at 1.0 bar and 273 K, along with high selectivity towards CO2 over N2 and CH4. The porous polymeric networks present the promising potentials as efficient adsorbents in clean energy applications.
Poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA)‐based brush poly(phosphoamidate)s are successfully synthesized by a combination of ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) following either a commutative two‐step procedure or a straightforward one‐pot process using Grubbs ruthenium‐based catalysts for tandem catalysis. Compared with the traditional polymerization method, combining ROMP and ATRP in a one‐pot process allows the preparation of brush copolymers characterized by a relatively moderate molecular weight distribution and quantitative conversion of monomer. Moreover, the surface morphologies and aggregation behaviors of these polymers are studied by AFM and TEM measurements.
Inspired by the multifunctionality of vitamin D‐binding protein and the multiple transient‐binding behavior of some intrinsically disordered proteins (IDPs), a polymeric platform is designed, prepared, and characterized for combined delivery of dermal protective and anticancer bioactive cargos on the basis of artificial single‐chain nano‐objects mimicking IDPs. For the first time ever, simultaneous delivery of folic acid or vitamin B9, and hinokitiol, a relevant natural bioactive compound that exhibits anticancer activity against human malignant melanoma cells, from these multidirectionally self‐assembled unimolecular nanocarriers is illustrated.
Supramolecular polymer networks have attracted considerable attention not only due to their topological importance but also because they can show some fantastic properties such as stimuli‐responsiveness and self‐healing. Although various supramolecular networks are constructed by supramolecular chemists based on different non‐covalent interactions, supramolecular polymer networks based on multiple orthogonal interactions are still rare. Here, a supramolecular polymer network is presented on the basis of the host–guest interactions between dibenzo‐24‐crown‐8 (DB24C8) and dibenzylammonium salts (DBAS), the metal–ligand coordination interactions between terpyridine and Zn(OTf)2, and between 1,2,3‐triazole and PdCl2(PhCN)2. The topology of the networks can be easily tuned from monomer to main‐chain supramolecular polymer and then to the supramolecular networks. This process is well studied by various characterization methods such as 1H NMR, UV–vis, DOSY, viscosity, and rheological measurements. More importantly, a supramolecular gel is obtained at high concentrations of the supramolecular networks, which demonstrates both stimuli‐responsiveness and self‐healing properties.
The coordination polymerization of silyl‐protected ω‐alkenols such as ω‐alken‐α‐oxytriisopropylsilanes 1 provides poly(ω‐alkenyl‐α‐oxytriisopropylsilalne)s with a highly isospecific microstructure ([mmmm] > 95%) when a combination of [OSSO]‐type bis(phenolato) dichloro zirconium(IV) complex 2 and dried methylaluminoxane is used as the precatalyst and activator, respectively. The resulting siloxy‐substituted polymers could be efficiently transformed into the corresponding functionalized polyolefins, which contained up to 90% acetyl groups and ≈7% hydroxy groups in the terminal side chains.
A thiofunctional thiazolidine is introduced as a new low‐molar‐mass building block for the introduction of cysteine residues via a thiol‐ene reaction. Allyl‐functional polyglycidol (PG) is used as a model polymer to demonstrate polymer‐analogue functionalization through reaction with the unsaturated side‐chains. A modified trinitrobenzenesulfonic acid (TNBSA) assay is used for the redox‐insensitive quantification and a precise final cysteine content can be predetermined at the polymerization stage. Native chemical ligation at cysteine‐functional PG is performed as a model reaction for a chemoselective peptide modification of this polymer. The three‐step synthesis of the thiofunctional thiazolidine reactant, together with the standard thiol‐ene coupling and the robust quantification assay, broadens the toolbox for thiol‐ene chemistry and offers a generic and straightforward approach to cysteine‐functional materials.
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.
