Synthetic Hydrophilic Materials with Tunable Strength and a Range of Hydrophobic Interactions

The ability to vary, adjust, and control hydrophobic interactions is crucial in manipulating interactions between biological objects and the surface of synthetic materials in aqueous environment. To this end a grafted polymer layer (multi‐component mixed polymer brush) is synthesized that is capable of reversibly exposing nanometer‐sized hydrophobic fragments at its hydrophilic surface and of tuning, turning on, and turning off the hydrophobic interactions. The reversible switching occurs in response to changes in the environment and alters the strength and range of attractive interactions between the layer and hydrophobic or amphiphilic probes in water. The grafted layer retains its overall hydrophilicity, while local hydrophobic forces enable the grafted layer to sense and attract the hydrophobic domains of protein molecules dissolved in the aqueous environment. The hydrophobic interactions between the material and a hydrophobic probe are investigated using atomic force microscopy measurements and a long‐range attractive and contact‐adhesive interaction between the material and the probe is observed, which is controlled by environmental conditions. Switching of the layer exterior is also confirmed via protein adsorption measurements.     

Producing Supramolecular Functional Materials Based on Fiber Network Reconstruction

Here, the creation of new supramolecular functional materials based on the reconstruction of three‐dimensional interconnecting self‐organized nanofiber networks by a surfactant is reported. The system under investigation is N‐lauroyl‐L ‐glutamic acid di‐n‐butylamide in propylene glycol. The architecture of networks is implemented in terms of surfactants, e.g. sorbitan monolaurate. The elastic performance of the soft functional material is either weakened or strengthened (up to 300% for the current system) by reconstructing the topology of a fiber network. A topology transition of gel fiber network from spherulite‐like to comb‐like to spherulite‐like is performed with the introduction of this surfactant. The Span 20 molecules are selectively adsorbed on the side surfaces of the crystalline fibers and promote the nucleation of side branches, giving rise to the transformation of the network architecture from spherulite‐like topology to comb‐like topology. At high surfactant concentrations, the occurrence of micelles may provide an increasing number of nucleation centers for spherulitic growth, leading to the reformation of spherulite‐like topology. An analysis on fiber network topology supports and verifies a perfect agreement between the topological behavior and the rheological behavior of the functional materials. The approach identified in this study opens up a completely new avenue in designing and producing self‐supporting supramolecular functional materials with designated macroscopic properties.     

Temperature‐Switchable Assembly of Supramolecular Virus–Polymer Complexes

Here a method is presented for the temperature‐switchable assembly of viral particles into large hierarchical complexes. Dual‐functional diblock copolymers consisting of poly(diethyleneglycol methyl ether methacry­late) (poly(DEGMA)) and poly((2‐dimethylamino)ethyl methacrylate) (poly(DMAEMA)) blocks self‐assemble electrostatically with cowpea chlorotic mottle virus (CCMV) particles into micrometer‐sized objects as a function of temperature. The poly(DMAEMA) block carries a positive charge, which can interact electrostatically with the negatively charged outer surface of the CCMV capsid. When the solution temperature is increased above 40 °C, to cross the cloud point temperature (T_cp) of the DEGMA block, the polymer chains collapse on the surface of the virus particle, which makes them partially hydrophobic, and consequently causes the formation of large hierarchical assemblies. Disassembly of the virus–polymer complexes can be induced by reducing the solution temperature below the T_cp, which allows the poly(DEGMA) blocks to rehydrate and free virus particles to be released. The assembly process is fully reversible and can sustain several heating–cooling cycles. Importantly, this method relies on reversible supramolecular interactions and therefore avoids the irreversible covalent modification of the particle surface. This study illustrates the potential of temperature‐responsive polymers for controlled binding and releasing of virus particles.     

Field‐Switchable Broadband Polarizer Based on Reconfigurable Nanowire Assemblies

Reconfigurability is one of the most critical properties of nanophotonic systems and, consequently, methods for enabling a significant degree of functionality are highly sought after. However, dynamically responsive control in top‐down fabricated photonic structures often requires extreme conditions and yields moderate modulation capability. In sharp contrast to top‐down methods, directed self‐assembly of micro‐ and nanoparticles offers a distinct avenue for reconfigurable photonics. In the present work, gold nanowire lattices are formed via electric field directed assembly in order to take advantage of their collective optical properties. The lattices are reconfigured on‐demand between two different functional states, in the form of broadband polarizers. By selectively switching the electric field between two orthogonal electrode pairs, a maximum transmission contrast of ≈50% is observed in the near‐infrared regime. Moreover, the reconfigurable transmission spectra, which are highly dependent on the nanowire size and electric field conditions, are reversible. The demonstrated proof‐of‐concept nanowire lattice polarizer provides potential for electrically reconfigurable photonic devices such as ultra‐compact polarization components, electro‐optic switches, and on‐chip modulators.     

Tough Hydrogels with Programmable and Complex Shape Deformations by Ion Dip‐Dyeing and Transfer Printing

Stimuli‐responsive hydrogels with high mechanical strength, programmable deformation, and simple preparation are essential for their practical applications. Here the preparation of tough hydrogels with programmable and complex shape deformations is reported. Janus hydrogels with different compositions and hydrophilic natures on the two surfaces are first prepared, and they exhibit reversible bending/unbending upon swelling/deswelling processes. More impressively, the deformation rate and extent of the hydrogels can further be easily controlled through an extremely simple and versatile ion dip‐dyeing (IDD) and/or ion transfer printing (ITP) method. By selectively printing proper patterns on 1D gel strips, 2D gel sheets and 3D gel structures, the transformations from 1D to 2D, 2D to 3D, and 3D to more complicated 3D shapes can be achieved after swelling the ion‐patterned hydrogels in water. The swelling‐deformable Janus and ion‐patterned hydrogels with high mechanical strengths and programmable deformations can find many practical applications, such as soft machines.     

Optically Transparent Antibacterial Films Capable of Healing Multiple Scratches

Optically transparent antibacterial films capable of healing scratches and restoring transparency are fabricated by exponential layer‐by‐layer assembly of branched polyethylenimine (bPEI)/poly(acrylic acid) (PAA) films and post‐diffusion of cetyltrimethylammonium bromide micelles encapsulated with antibacterial agent triclosan. The triclosan‐loaded bPEI/PAA transparent films can effectively inhibit the growth of gram‐positive and gram‐negative bacteria by the sustained release of triclosan molecules. Healing of multiple scratches on the triclosan‐loaded bPEI/PAA films can be conveniently achieved by immersing the films in water or spraying water on the damaged films, which also fully restores their transparency. The self‐healing ability of these transparent antibacterial films originates from the ability of bPEI and PAA to flow and recombine in the presence of water. The triclosan‐loaded bPEI/PAA films have satisfactory mechanical stability under ambient conditions, and thus show potential for application as transparent protective films with antibacterial properties.     

Stimuli‐Responsive Materials for Controlled Release of Theranostic Agents

Stimuli‐responsive materials are so named because they can alter their physicochemical properties and/or structural conformations in response to specific stimuli. The stimuli can be internal, such as physiological or pathological variations in the target cells/tissues, or external, such as optical and ultrasound radiations. In recent years, these materials have gained increasing interest in biomedical applications due to their potential for spatially and temporally controlled release of theranostic agents in response to the specific stimuli. This article highlights several recent advances in the development of such materials, with a focus on their molecular designs and formulations. The future of stimuli‐responsive materials will also be explored, including combination with molecular imaging probes and targeting moieties, which could enable simultaneous diagnosis and treatment of a specific disease, as well as multi‐functionality and responsiveness to multiple stimuli, all important in overcoming intrinsic biological barriers and increasing clinical viability.     

Photoswitchable Gas Permeation Membranes Based on Liquid Crystals

We have fabricated switchable gas permeation membranes in which a photoswitchable low‐molecular‐weight liquid crystalline (LC) material acts as the active element. Liquid crystal mixtures are doped with mesogenic azo dyes and infused into commercially available track‐etched membranes with regular cylindrical pores (0.40 to 10.0 μm). Tunability of mass transfer can be achieved through a combination of (1) LC/mesogenic dye composition, (2) surface‐induced alignment, and (3) reversible photoinduced LC‐isotropic transitions. Photo‐induced isothermal phase changes in the imbibed material afford large and fully reversible changes in the permeability of the membrane to nitrogen. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure relationship, but they show significant differences in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic—or vice versa – and can be further tuned by surface alignment. Permeability switching response times are 5 s, with alternating UV and >420‐nm radiation at an intensity of 2 mW/cm² being sufficient for complete and reversible switching. Thermal and kinetic properties of the confined LC materials are evaluated and correlated with the observed permeation properties. We demonstrate for the first time reversible permeation control of a membrane with light irradiation.     

Transfer Printing of Cell Layers with an Anisotropic Extracellular Matrix Assembly using Cell‐Interactive and Thermosensitive Hydrogels

The structure of tissue plays a critical role in its function and therefore a great deal of attention has been focused on engineering native tissue‐like constructs for tissue engineering applications. Transfer printing of cell layers is a new technology that allows controlled transfer of cell layers cultured on smart substrates with defined shape and size onto tissue‐specific defect sites. Here, the temperature‐responsive swelling‐deswelling of the hydrogels with groove patterns and their versatile and simple use as a template to harvest cell layers with anisotropic extracellular matrix assembly is reported. The hydrogels with a cell‐interactive peptide and anisotropic groove patterns are obtained via enzymatic polymerization. The results show that the cell layer with patterns can be easily transferred to new substrates by lowering the temperature. In addition, multiple cell layers are stacked on the new substrate in a hierarchical manner and the cell layer is easily transplanted onto a subcutaneous region. These results indicate that the evaluated hydrogel can be used as a novel substrate for transfer printing of artificial tissue constructs with controlled structural integrity, which may hold potential to engineer tissue that can closely mimic native tissue architecture.     

聚合物光诱导电荷转移光电池的研究进展

综述了以共轭聚合物作为电子施主和 C6 0 及其衍生物作为电子受主的共混与多层器件结构的聚合物光诱导电荷转移光电池的研究进展。对这类新型结构的光电池的基本性能及机制作了介绍。低生产成本、能通过简单甩膜或印刷方式就能制备大面积器件的优势使聚合物光电池在许多实际应用领域具有广阔的前景。对今后进一步提高这类光电池的能量转换效率的研究方向进行了探讨     

Tuning the Unidirectional Electron Transfer at Interfaces with Multilayered Redox‐active Supramolecular Bionanoassemblies

In this work, we present a new strategy to construct redox‐active molecular platforms to be used as molecular rectifiers with tunable and amplifiable electronic readout. The approach is based on using ligand‐receptor biological interactions to bioconjugate electroactive bio‐inorganic building blocks onto metal electrodes. The stability of the self‐assembled interfacial architecture is provided by multivalent macromolecular ligands that act as scaffolds for building‐up the multilayered structures. The ability of these electroactive supramolecular architectures to generate a unidirectional current flow and tune the corresponding electronic readout was demonstrated by mediating and rectifying the electron transfer between redox donors in solution and the Au electrode. The redox centers incorporated into the assembled architecture in a topologically controlled manner are responsible for tuning the amplification of the rectified electronic readout, thus behaving as a tunable bio‐supramolecular diode. Our experimental results obtained with these redox‐active bio‐supramolecular architectures illustrate the versatility of molecular recognition‐directed assembly in combination with hybrid bio‐inorganic building blocks to construct highly functional interfacial architectures.     

Soft Nanotubes with a Hydrophobic Channel Hybridized with Au Nanoparticles: Photothermal Dispersion/Aggregation Control of C60 in Water

Simple glycolipid N‐alkaroyl‐β‐D‐glucopyranosylamine 1(n) selectively self‐assembles into sheets in water, nanotubes in alcohols, and helical nanocoils in toluene. All self‐assemblies consist of bilayer membranes in which 1(n) packed in an interdigitated fashion. The outer surface of the sheet is covered with the hydrophilic glucose headgroup of 1(n), whereas those of the nanotube and helical nanocoil are covered with the hydrophobic alkyl‐chain tail of 1(n). Heat treatment of the nanotube in the presence of water induces a rearrangement of the molecular packing of the outermost surface that allows the nanotube to become an effective nanocontainer for the dispersion of fullerene (C60) in water, a result of the ability of the hydrophilic outer surface of the nanotube and the hydrophobic nanochannel to encapsulate C60. The nanotube also exhibits photothermal characteristics after being hybridized with Au nanoparticles (AuNPs). The photothermal effect of the AuNPs allows the nanotube to unfold its tubular morphology and leads to compulsive release of the encapsulated C60 to the bulk water. Application of other nanotubes with similar photostimulated transformation ability should facilitate control of the dispersion/aggregation of other carbon nanomaterials, functional aromatic compounds, and drugs with low solubility in water.     

Boroxine Nanotubes: Moisture‐Sensitive Morphological Transformation and Guest Release

Boroxines, (R‐BO)₃, which can be easily synthesized via a dehydration reaction of boronic acids, R–B(OH)₂, selectively self‐assemble in toluene into nanofibers, nanorods, nanotapes, and nanotubes, depending on the aromatic substituent (R). Spectroscopic measurements show that the nanotube consists of a J‐aggregate of the boroxine. Humidification converts the morphology from the nanotube to a sheet as a result of the hydrolysis of the boroxine components and subsequent molecular‐packing rearrangement from the J‐aggregate to an H‐aggregate. Such a transformation leads to the compulsive release of guest molecules encapsulated in the hollow cylinder of the nanotube. The hydrolysis and the molecular‐packing rearrangement described above are suppressed by coordination of pyridine to the boron atom, with the resulting moiety acting as a Lewis acid of the boroxine component. The pyridine‐coordinated nanotube is transformed into a helical coil by humidification. Guest release during the nanotube‐to‐helical‐coil transformation is much slower than during the nanotube‐to‐sheet transformation, but faster than from a nanotube that did not undergo morphological transformation. The storage and release of guest molecules from the boroxine nanotubes can be precisely controlled by adjusting the moisture level and the concentration of Lewis bases, such as amines.     

Nanostructures from Single Amino Acid‐Based Molecules: Stability,Fibrillation, Encapsulation,and Fabrication of Silver Nanoparticles

The small‐sized molecules that have been developed from single hydrophobic amino acids (Phe, Trp, Tyr and Leu) by suitably protecting the –NH₂ and –CO₂H groups generate diverse nanoscopic structures – such as nanorods, nanofibrils, nanotubes, and nanovesicles – depending upon the protection parameters and solvent polarity. The vesicular structures get disrupted in the presence of various salts, such as KCl, CaCl₂, (NH₄)₂SO₄ and N(n‐Bu)₄Br. Insertion of unnatural (o/m/p)‐aminobenzoic acids as a protecting group and the lack of conventional peptide bonds in the molecules give the nanostructures proteolytic stability. The nanostructures also show significant thermal stability along with a morphological transformation upon heat treatment. Our in vitro studies reveal that the addition of micromolar concentration “curcumin” significantly reduces the formation of amyloid‐like fibrils. These diverse nanostructures are used as a template for fabricating silver nanoparticles on their outer surfaces as well as in the inner part, followed by calcination in air which helps to obtain a 1D silver nanostructure. Furthermore, the nanovesicles are observed to encapsulate a potent drug (curcumin) and other biologically important molecules, which could be released through salt‐triggered disruption of vesicles.     

Well‐Defined Pillararene‐Based Azobenzene Liquid Crystalline Photoresponsive Materials and Their Thin Films with Photomodulated Surfaces

Photoresponsive materials (PRMs) have long been a hot topic and photo‐modulated smart surface is very appealing. Particularly, liquid crystalline PRMs are able to amplify and stabilize photoinduced orientation thanks to their self‐assembling and ordering characteristics. Herein, the first pillararene‐based azobenzene liquid crystalline PRM with well‐defined structure is presented, which can avoid the usually ill‐defined composition drawback of polymer PRMs and prevent the severe H‐aggregation from suppressing or even completely blocking photoresponse in simple azobenzene derivatives. The pillar[5]arene‐based macrocyclic azobenzenes with variant length spacers show wide temperature range smectic liquid crystalline mesophases and excellent film‐formation property. The tubular pillar[5]arene macrocyclic framework provides sufficient free volume for azobenzene moieties to achieve reversible photoisomerization and photoalignment; thus, their thin films demonstrate excellent light‐triggered modulation of surface free energy, wettability, and even photoalignment‐mediated orientation of an upper layer discotic liquid crystal columnar mesophase. Such pillararene‐based azobenzene liquid crystals represent novel and promising PRMs with extensive fascinating applications.     

Polymorphism in Crystalline Microfibers of Achiral Octithiophene: The Effect on Charge Transport,Supramolecular Chirality and Optical Properties

Polymorphic crystalline microfibers from an achiral octithiophene with one S‐hexyl substituent per ring are separately and reproducibly grown with the same characteristics on various solid surfaces, including the interdigitated electrodes/SiO₂ surface of a bottomcontact field‐effect transistor. The arrangement of the same molecule in two diverse supramolecular structures leads to markedly different electronic, optical, and charge mobility properties. The microfibers—straight and yellow emitting or helical and red emitting—exhibit p‐type charge transport characteristics, with the yellow ones showing a charge mobility and on/off current ratio of one and three orders of magnitude, respectively, greater than the red ones. Both forms show circular dichroism signals with significant differences from one form to the other. DFT calculations show that the octithiophene exists in two different quasi‐equienergetic conformations aggregating with diverse orientations of the substituents. This result suggests that the observed polymorphism is conformational in nature. The self‐assembly, driven by sulfur–sulfur non‐bonding interactions, amplifies the small property differences between conformers, leading to quite different bulk properties.     

Novel,Robust, and Versatile Bijels of Nitromethane,Ethanediol, and Colloidal Silica: Capsules,Sub‐Ten‐Micrometer Domains,and Mechanical Properties

Bicontinuous, interfacially jammed emulsion gels (bijels) are a class of soft solid materials in which interpenetrating domains of two immiscible fluids are stabilized by an interfacial colloidal monolayer. Such structures form through the arrest of the spinodal decomposition of an initially single‐phase liquid mixture containing a colloidal suspension. With the use of hexalmethyldisilazane, the wetting character of silica colloids, ranging in size and dye content, can be modified for fabricating a novel bijel system comprising the binary liquid ethanediol–nitromethane. Unlike the preceding water‐lutidine based system, this bijel is stable at room temperature and its fabrication and resultant manipulation are comparatively straightforward. The new system has facilitated three advancements: firstly, we use sub 100 nm silica particles to stabilize the first bijel made from low molecular weight liquids that has domains smaller than ten micrometers. Secondly, our new and robust bijel permits qualitative rheological work which reveals the bijel to be significantly elastic and self healing whilst its domains are able to break, reform and locally rearrange. Thirdly, we encapsulate the ethanediol–nitromethane bijel in Pickering drops to form novel particle‐stabilized bicontinuous multiple emulsions that we christen bijel capsules. These emulsions are stimuli responsive – they liberate their contained materials in response to changes in temperature and solvency, and hence they show potential for controlled release applications.     

Conditional DNA‐Protein Interactions Confer Stimulus‐Sensing Properties to Biohybrid Materials

Interactive materials that specifically respond to environmental stimuli hold high promise as energy‐autonomous sensors and actuators in biomedicine, analytics or microsystems engineering. However, the implementation of materials specifically responsive to a given small molecule has so far been hampered by a lack of generically applicable stimulus sensors. In this study, a novel and likely general strategy for the synthesis of biohybrid materials with desired stimulus specificity is established. The strategy is based on allosterically regulated DNA‐binding proteins, a conserved protein family that has evolved in prokaryotes to sense and respond to most diverse molecules in order to enable bacterial survival in a changing environment. The novel hydrogel design concept is demonstrated with the example of single‐chain TetR, a protein that binds the tetO DNA motif and dissociates thereof in the presence of the antibiotic tetracycline. Therefore, linear polyacrylamide is crosslinked via the TetR/tetO interaction to a biohybrid material that can subsequently be dissolved by tetracycline in a dose‐dependent manner. This drug‐induced dissolution is applied for the adjustable release of the cytokine interleukin 4 in a tetracycline‐dependent manner. The design concept developed in this study might serve as a blueprint for the synthesis of biohybrid materials responsive to drugs, metabolites or toxins by replacing TetR/tetO with another protein/DNA pair showing the desired stimulus specificity.