The development of facile and versatile strategies with low-cost for hydrogel construction is of tremendous scientific interest. Herein, we demonstrate that naturally derived, cost-effective tannic acid (TA) can be an efficient gelation binder for the hydrogel formation with a series of commercially available water-soluble polymers. With a five-polyphenol-arm structure, TA molecules are able to grasp polymer chains through either hydrogen or ionic bonds and cross-link them together by coordinate bonds in the presence of Fe(III) ions. These two interactions can be elegantly balanced by tuning the weight ratios of polymer/TA and TA/ Fe 3+ , which is the key point for the construction of supramolecular hydrogels. The supramolecular hydrogels exhibit multiple functionalities including mechanical tenability, rapid self-healing, pH-stimuli responsiveness, and free radical scavenging abilities. TA as a dynamic and versatile catechol group modifier provides a simple path to the construction of multifunctional hydrogels, which shows obvious advantages such as easy and green processing, low cost, and large-scale preparation.

The cytotoxicity of 2D graphene-based nanomaterials (GBNs) is highly important for engineered applications and environmental health. However, the isotropic orientation of GBNs, most notably graphene oxide (GO), in previous experimental studies obscured the interpretation of cytotoxic contributions of nanosheet edges. Here, we investigate the orientation-dependent interaction of GBNs with bacteria using GO composite films. To produce the films, GO nanosheets are aligned in a magnetic field, immobilized by cross-linking of the surrounding matrix, and exposed on the surface through oxidative etching. Characterization by small-angle X-ray scattering and atomic force microscopy confirms that GO nanosheets align progressively well with increasing magnetic field strength and that the alignment is effectively preserved by cross-linking. When contacted with the model bacterium , GO nanosheets with vertical orientation exhibit enhanced antibacterial activity compared with random and horizontal orientations. Further characterization is performed to explain the enhanced antibacterial activity of the film with vertically aligned GO. Using phospholipid vesicles as a model system, we observe that GO nanosheets induce physical disruption of the lipid bilayer. Additionally, we find substantial GO-induced oxidation of glutathione, a model intracellular antioxidant, paired with limited generation of reactive oxygen species, suggesting that oxidation occurs through a direct electron-transfer mechanism. These physical and chemical mechanisms both require nanosheet penetration of the cell membrane, suggesting that the enhanced antibacterial activity of the film with vertically aligned GO stems from an increased density of edges with a preferential orientation for membrane disruption. The importance of nanosheet penetration for cytotoxicity has direct implications for the design of engineering surfaces using GBNs.

There is long-standing interest in developing membranes possessing uniform pores with dimensions in the range of 1 nm and physical continuity in the macroscopic transport direction to meet the needs of challenging small molecule and ionic separations. Here we report facile, scalabe fabrication of polymer membranes with vertically (i.e., along the through-plane direction) aligned 1 nm pores by magnetic-field alignment and subsequent cross-linking of a liquid crystalline mesophase. We utilize a wedge-shaped amphiphilic species as the building block of a thermotropic columnar mesophase with 1 nm ionic nanochannels, and leverage the magnetic anisotropy of the amphiphile to control the alignment of these pores with a magnetic field. In situ X-ray scattering and subsequent optical microscopy reveal the formation of highly ordered nanostructured mesophases and cross-linked polymer films with orientational order parameters of ca. 0.95. High-resolution transmission electron microscopy (TEM) imaging provides direct visualization of long-range persistence of vertically aligned, hexagonally packed nanopores in unprecedented detail, demonstrating high-fidelity retention of structure and alignment after photo-cross-linking. Ionic conductivity measurements on the aligned membranes show a remarkable 85-fold enhancement of conductivity over nonaligned samples. These results provide a path to achieving the large area control of morphology and related enhancement of properties required for high-performance membranes and other applications.

The graft-through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self-assembly of GBCPs resulted in ordered nanostructures with ultra-small domain sizes down to 2.8 nm (half-pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self-assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.

Membrane separations are critically important in areas ranging from health care and analytical chemistry to bioprocessing and water purification. An ideal nanoporous membrane would consist of a thin film with physically continuous and vertically aligned nanopores and would display a narrow distribution of pore sizes. However, the current state of the art departs considerably from this ideal and is beset by intrinsic trade-offs between permeability and selectivity. We demonstrate an effective and scalable method to fabricate polymer films with ideal membrane morphologies consisting of submicron thickness films with physically continuous and vertically aligned 1 nm pores. The approach is based on soft confinement to control the orientation of a cross-linkable mesophase in which the pores are produced by self-assembly. The scalability, exceptional ease of fabrication, and potential to create a new class of nanofiltration membranes stand out as compelling aspects.

We describe a combination of molecular templating and directed self-assembly to realize highly selective vertically aligned nanopores in polymer membranes using sustainably derived materials. The approach exploits a structure-directing molecule to template the assembly of plant-derived fatty acids into highly ordered columnar mesophases. Directed self-assembly using physical confinement and magnetic fields provides vertical alignment of the columnar nanostructures in large area (several cm) thin films. Chemically cross-linking the mesophase with added conventional vinyl comonomers and removing the molecular template results in a mechanically robust polymer film with vertically aligned 1.2-1.5 nm diameter nanopores with a large specific surface area of ∼670 m/g. The nanoporous polymer films display exceptional size and charge selectivity as demonstrated by adsorption experiments using model penetrant molecules. These materials have significant potential to function as high-performance nanofiltration membranes and as nanoporous thin films for high-density lithographic pattern transfer. The scalability of the fabrication process suggests that practical applications can be reasonably anticipated.

unlike human tissues with rather complex and hierarchical structures, most of currently reported artificial ionic conductors, involving hydrogels, organohydrogels, ionogels, and ionic elastomers, were synthesized on the basis of a homogeneous solvent-swollen or salt-plasticized soft chain network. [4,[7][8][9][10][11] Despite high stretchability and optical transparency, such a soft network shows negligible or very small modulating effect on ion transportation; as a result, the ionic conductivity does not change or only slightly increases as stretched due to the preferential orientation of elastic chains. Generally, the mechanoelectric response of the current ionic conductors is just between conductivityconstant conductors (e.g., ionic liquids, [12] liquid metals, [13] viscoelastic gels, [11] etc.; conductivity change, σ/σ 0 = 1) and resistance-constant conductors (e.g., buckling sheath-core fibers, [14] liquid metal-elastomer composites, [15] etc.; σ/σ 0 = λ 2 , λ is the deformation ratio) (Figure 1a). It is well-known that the output resistance (R) is governed by Pouillet's Law (R = L/(σ•A)), with A designating the cross-sectional area and L the length (during stretch, L increases while A is reduced). Understandably, the moderate electrical response of ionic conductors not only limits their strain sensing applications toward high gauge factors as do percolating electronic conductors with strain-induced deteriorated conductivity, [16] but also goes against interconnect applications that require straininsensitive resistance to maintain stable electrical transmission. So far, it remains a formidable challenge for stretchable ionic conductors to overcome the seemingly inherent yet tardy mechanoelectric response arising from the poor modulating ability of soft chain network for ionic conduction.It is reported that the network topology of ionic conductors at nanometer scales is of paramount importance in altering the mobility of ionic species. [17,18] In nanofluidics, tortuosity is defined as the ratio of actual ion pathway length to the straight end-to-end distance. Highly ordered or longitudinally aligned ion-insulating nanostructures can afford low-tortuosity pathways to promote ion transport and thus significantly reduce apparent resistance. [19] Therefore, it could be feasible to introduce large amounts of ion-insulating rigid molecular units into the elastic network of ionic conductors to modulate ion transport via tortuosity changes. We consider that, liquid crystal elastomers (LCEs) might be one of the best candidate materials for this purpose, as they encompass the properties of polymeric Stretchable ionic conductors are appealing for tissue-like soft electronics, yet suffer from a tardy mechanoelectric response due to their poor modulation of ionic conduction arising from intrinsic homogeneous soft chain network. Here, a highly robust ionotronic fiber is designed by synergizing ionic liquid and liquid crystal elastomer with alternate rigid mesogen units and soft chain spacers, which shows an unprecedented s...

Self-assembled materials are attractive for next-generation membranes. However, the need to align self-assembled nanostructures (e.g. cylinders, lamellae) and the narrow stability windows for ordered bicontinuous systems present serious challenges. We propose and demonstrate a novel approach that circumvents these challenges by exploiting size-selective transport in the water-continuous medium of a nanostructured polymer templated from a self-assembled lyotropic H1 mesophase. Optimization of the mesophase composition enables high-fidelity retention of the H1 structure on photoinduced cross-linking. The resulting material is a mechanically robust nanostructured polymer possessing internally and externally cross-linked nanofibrils surrounded by a continuous aqueous medium. Fabricated membranes show size selectivity at the 1- to 2-nm length scale and water permeabilities of ~10 liters m−2 hour−1 bar−1 μm. Moreover, the membranes display excellent antimicrobial properties due to the quaternary ammonium groups on the nanofibril surfaces. These results represent a breakthrough for the potential use of polymerized lyotropic mesophase membranes in practical water purification applications.