Ring Shuttling Controls Macroscopic Motion in a Three-Dimensional Printed Polyrotaxane Monolith

Advanced biomedical and electronic dual-function skin patch created through microfluidic-regulated 3D bioprinting

Artificial skin involves multidisciplinary efforts, including materials science, biology, medicine, and tissue engineering. Recent studies have aimed at creating skins that are multifunctional, intelligent, and capable of regenerating tissue. In this work, we present a specialized 3D printing ink composed of polyurethane and bioactive glass (PU-BG) and prepare dual-function skin patch by microfluidic-regulated 3D bioprinting (MRBP) technique. The MRBP endows the skin patch with a highly controlled microstructure and superior strength. Besides, an asymmetric tri-layer is further constructed, which promotes cell attachment and growth through a dual transport mechanism based on hydrogen bonds and gradient structure from hydrophilic to superhydrophilic. More importantly, by combining the features of biomedical skin with electronic skin (e-skin), we achieved a biomedical and electronic dual-function skin patch. In vivo experiments have shown that this skin patch can enhance hemostasis, resist bacterial growth, stimulate the regeneration of blood vessels, and accelerate the healing process. Meanwhile, it also mimics the sensory functions of natural skin to realize signal detection, where the sensitivity reached up to 5.87 kPa-1, as well as cyclic stability (over 500 cycles), a wide detection range of 0-150 kPa, high pressure resolution of 0.1 % under the pressure of 100 kPa. This work offers a versatile and effective method for creating dual-function skin patches and provide new insights into wound healing and tissue repair, which have significant implications for clinical applications.

Granular polyrotaxane microgels as injectable hydrogels for corneal tissue regeneration

Corneal diseases, a leading cause of global vision impairment, present challenges in treatment due to corneal tissue donor scarcity and transplant rejection. Hydrogel biomaterials in the form of corneal implants for tissue regeneration, while promising, have faced obstacles related to cellular and tissue integration. This study develops and investigates the potential of granular polyrotaxane (GPR) hydrogels as a scaffold for corneal keratocyte growth and transparent tissue generation. Employing host-guest driven supramolecular interactions, we developed injectable, cytocompatible hydrogels. By optimizing cyclodextrin (CD) concentrations in thiol-ene crosslinked PEG microgels, we observed improved mechanical properties and thermoresponsiveness while preserving injectability. These microgels, adaptable for precise defect filling, 3D printing or tissue culture facilitate enhanced cellular integration with corneal keratocytes and exhibit tissue-like structures in culture. Our findings demonstrate the promise of GPR hydrogels as a minimally invasive avenue for corneal tissue regeneration. These results have the potential to address transplantation challenges, enhance clinical outcomes, and restore vision.

Mechanical Stretch α-Cyclodextrin Pseudopolyrotaxane Elastomer with Reversible Phosphorescence Behavior

Polyethylene glycol chains in two terminals of the naphthalene functional group are threaded into α-cyclodextrin cavities to form the pseudopolyrotaxane (NPR), which not only effectively induces the phosphorescence of the naphthalene functional group by the cyclodextrin macrocycle confinement, but also provides interfacial hydrogen bonding assembly function between polyhydroxy groups of cyclodextrin and waterborne polyurethane (WPU) chains to construct elastomers. The introduction of NPR endows the elastomer with enhanced mechanical properties and excellent room temperature phosphorescent (RTP) emission (phosphorescence remains in water, acid, alkali, and organic solvents, even at 160 °C high temperatures). Especially, the reversible mechanically responsive room temperature phosphorescence behavior (phosphorescence intensity increased three times under 200% strain) can be observed in the mechanical stretch and recover process, owing to strain-induced microstructural changes further inhibiting the non-radiative transition and the vibration of NPR. Therefore, changing the phosphorescence behavior of supramolecular elastomers through mechanical stretching provides a new approach for supramolecular luminescent materials.

Hierarchically Templated Synthesis of 3D-Printed Crosslinked Cyclodextrins for Lycopene Harvesting

Plants produce a wide range of bioactive phytochemicals, such as antioxidants and vitamins, which play crucial roles in aging prevention, inflammation reduction, and reducing the risk of cancer. Selectively harvesting these phytochemicals, such as lycopene, from tomatoes through the adsorption method is cost-effective and energy efficient. In this work, a templated synthesis of 3D-printed crosslinked cyclodextrin polymers featuring nanotubular structures for highly selective lycopene harvesting is reported. Polypseudorotaxanes formed by triethoxysilane-based telechelic polyethylene glycols and α-cyclodextrins (α-CDs) are designed as the template to (1) synthetically access urethane-based nanotubular structures at the molecular level, and (2) construct 3D-printed architectures with designed macroscale voids. The polypseudorotaxane hydrogels showed good rheological properties for direct ink writing, and the 3D-printed hydrogels were converted to the desired α-CD polymer network through a three-step postprinting transformation. The obtained urethane-crosslinked α-CD monoliths possess nanotubular structures and 3D-printed voids. They selectively adsorb lycopene from raw tomato juice, protecting lycopene from photo- or thermo-degradations. This work highlights the hierarchically templated synthesis approach in developing functional 3D-printing materials by connecting the bottom-up molecular assembly and synthesis with the top-down 3D architecture control and fabrication.

Machine Learning in Predicting Printable Biomaterial Formulations for Direct Ink Writing

Three-dimensional (3D) printing is emerging as a transformative technology for biomedical engineering. The 3D printed product can be patient-specific by allowing customizability and direct control of the architecture. The trial-and-error approach currently used for developing the composition of printable inks is time- and resource-consuming due to the increasing number of variables requiring expert knowledge. Artificial intelligence has the potential to reshape the ink development process by forming a predictive model for printability from experimental data. In this paper, we constructed machine learning (ML) algorithms including decision tree, random forest (RF), and deep learning (DL) to predict the printability of biomaterials. A total of 210 formulations including 16 different bioactive and smart materials and 4 solvents were 3D printed, and their printability was assessed. All ML methods were able to learn and predict the printability of a variety of inks based on their biomaterial formulations. In particular, the RF algorithm has achieved the highest accuracy (88.1%), precision (90.6%), and F1 score (87.0%), indicating the best overall performance out of the 3 algorithms, while DL has the highest recall (87.3%). Furthermore, the ML algorithms have predicted the printability window of biomaterials to guide the ink development. The printability map generated with DL has finer granularity than other algorithms. ML has proven to be an effective and novel strategy for developing biomaterial formulations with desired 3D printability for biomedical engineering applications.

Enhanced Bacterial-Infected Wound Healing by Nitric Oxide-Releasing Topological Supramolecular Nanocarriers with Self-Optimized Cooperative Multi-Point Anchoring

Polymeric systems that provide cationic charges or biocide-release therapeutics are used to treat the bacteria-infected wound. However, most antibacterial polymers based on topologies with restricted molecular dynamics still do not satisfy the clinical requirements due to their limited antibacterial efficacy at safe concentrations in vivo. Here a NO-releasing topological supramolecular nanocarrier with rotatable and slidable molecular entities is reported to provide conformational freedom to promote the interactions between the carrier and the pathogenic microbes, hence greatly improving the antibacterial performance. With improved contacting-killing and efficient delivery of NO biocide from the molecularly dynamic cationic ligand design, the NO-loaded topological nanocarrier achieves excellent antibacterial and anti-biofilm effects via destroying the bacterial membrane and DNA. MRSA-infected rat model is also brought out to demonstrate its wound-healing effect with neglectable toxicity in vivo. Introducing flexible molecular motions into therapeutic polymeric systems is a general design to enhance the healing of a range of diseases.

Advanced supramolecular design for direct ink writing of soft materials

The exciting advancements in 3D-printing of soft materials are changing the landscape of materials development and fabrication. Among various 3D-printers that are designed for soft materials fabrication, the direct ink writing (DIW) system is particularly attractive for chemists and materials scientists due to the mild fabrication conditions, compatibility with a wide range of organic and inorganic materials, and the ease of multi-materials 3D-printing. Inks for DIW need to possess suitable viscoelastic properties to allow for smooth extrusion and be self-supportive after printing, but molecularly facilitating 3D printability to functional materials remains nontrivial. While supramolecular binding motifs have been increasingly used for 3D-printing, these inks are largely optimized empirically for DIW. Hence, this review aims to establish a clear connection between the molecular understanding of the supramolecularly bound motifs and their viscoelastic properties at bulk. Herein, extrudable (but not self-supportive) and 3D-printable (self-supportive) polymeric materials that utilize noncovalent interactions, including hydrogen bonding, host-guest inclusion, metal-ligand coordination, micro-crystallization, and van der Waals interaction, have been discussed in detail. In particular, the rheological distinctions between extrudable and 3D-printable inks have been discussed from a supramolecular design perspective. Examples shown in this review also highlight the exciting macroscale functions amplified from the molecular design. Challenges associated with the hierarchical control and characterization of supramolecularly designed DIW inks are also outlined. The perspective of utilizing supramolecular binding motifs in soft materials DIW printing has been discussed. This review serves to connect researchers across disciplines to develop innovative solutions that connect top-down 3D-printing and bottom-up supramolecular design to accelerate the development of 3D-print soft materials for a sustainable future.

Control of the assembly of a cyclic hetero[4]pseudorotaxane from a self-complementary [2]rotaxane

The self-association of a ditopic [2]rotaxane with two macrocycles mainly leads to a [4]pseudorotaxane which can be reversibly disassembled by adding competitive binders, varying the solvent polarity and changing a binding site affinity.

Mechanically interlocked polymers based on rotaxanes

The nature of mechanically interlocked molecules (MIMs) has continued to encourage researchers to design and construct a variety of high-performance materials. Introducing mechanically interlocked structures into polymers has led to novel polymeric materials, called mechanically interlocked polymers (MIPs). Rotaxane-based MIPs are an important class, where the mechanically interlocked characteristic retains a high degree of structural freedom and mobility of their components, such as the rotation and sliding motions of rotaxane units. Therefore, these MIP materials are known to possess a unique set of properties, including mechanical robustness, adaptability and responsiveness, which endow them with potential applications in many emerging fields, such as protective materials, intelligent actuators, and mechanisorption. In this review, we outline the synthetic strategies, structure-property relationships, and application explorations of various polyrotaxanes, including linear polyrotaxanes, polyrotaxane networks, and rotaxane dendrimers.

Rigidity and Flexibility in Rotaxanes and Their Relatives; On Being Stubborn and Easy-Going

Rotaxanes are an emerging class of molecules composed of two building blocks: macrocycles and threads. Rotaxanes, and their pseudorotaxane and polyrotaxane relatives, serve as prototypes for molecular-level switches and machines and as components in materials like elastic polymers and 3D printing inks. The rigidity and flexibility of these molecules is a characteristic feature of their design. However, the mechanical properties of the assembled rotaxane and its components are rarely examined directly, and the translation of these properties from molecules to bulk materials is understudied. In this Review, we consider the mechanical properties of rotaxanes by making use of concepts borrowed from physical organic chemistry. Rigid molecules have fewer accessible conformations with higher energy barriers while flexible molecules have more accessible conformations and lower energy barriers. The macrocycles and threads become rigidified when threaded together as rotaxanes in which the formation of intermolecular interactions and increased steric contacts collectively reduce the conformational space and raise barriers. Conversely, rotational and translational isomerism in rotaxanes adds novel modes of flexibility. We find that rigidification in rotaxanes is almost universal, but novel degrees of flexibility can be introduced. Both have roles to play in the function of rotaxanes.

Thermally induced disassembly mechanism of pseudo-polyrotaxane nanosheets consisting of β-CD and a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymer

PPRNSs dissolved in two steps during heating owing to the anisotropy of the topological constraint of β-CD by axis polymers.

Macrocyclic host molecules with aromatic building blocks: the state of the art and progress

Macrocyclic host molecules play the central role in host-guest chemistry and supramolecular chemistry. The highly structural symmetry of macrocyclic host molecules can meet people's pursuit of aesthetics in molecular design, and generally means a balance of design, synthesis, properties and applications. For macrocyclic host molecules with highly symmetrical structures, building blocks, which could be described as repeat units as well, are the most fundamental elements for molecular design. The structural features and recognition ability of macrocyclic host molecules are determined by the building blocks and their connection patterns. Using different building blocks, different macrocyclic host molecules could be designed and synthesized. With decades of developments of host-guest chemistry and supramolecular chemistry, diverse macrocyclic host molecules with different building blocks have been designed and synthesized. Aromatic building blocks are a big family among the various building blocks used in constructing macrocyclic host molecules. In this feature article, the recent developments of macrocyclic host molecules with aromatic building blocks were summarized and discussed.

Self-assembled biocompatible heparin-based supramolecular hydrogel for doxorubicin delivery

An array of self-assembled biocompatible doxorubicin (DOX) loaded heparin--cyclodextrin supramolecular hydrogels (DOX@HGs) with highly encapsulated efficiency was constructed using heparin-β-cyclodextrin derivatives (Hep-β-CD), α-cyclodextrin (α-CD), pluronic F-127 and DOX via the synergy of host-guest and multiple hydrogen bonding interactions. These hydrogels were characterized by GPC measurements (GPC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Size and zeta potential determinations, X-ray diffraction (XRD), and rheological characteristics; the data confirmed successful formation of the hydrogels. Furthermore, these hydrogels demonstrated distinctive thixotropy, indicating rapid self-repairing after continuously oscillatory shear stress. Variable release of DOX from DOX @HGs was obtained at various pH after 84 h depending on the strength of the hydrogels. At pH 7.4, cumulative DOX release was approximately 49.07% for DOX@HG 1, 32.15% for DOX@HG 2, and 27.12% for DOX@HG 3. While at pH 5.5, release of DOX was increased to 59.08% for DOX@HG 1 and to 43.2% for DOX@HG 3 after 84 h (P < 0.05). This information demonstrated that a higher DOX release rate was observed under a lower pH due to strong charge expansion of CDs and weakening of electrostatic interactions between heparin and DOX. Additionally, cytotoxicity of free DOX and DOX@HGs in ovarian cancer SKOV-3 cells was studied at various exposure durations. The results revealed that cytotoxicity of DOX@HG 1-3 toward ovarian cancer SKOV-3 cells was lower than that of free DOX (P < 0.05), suggesting prolonged DOX release from the hydrogels in SKOV-3 cells.

Molecular Recognition of Fluorescent Probe Molecules with a Pseudopolyrotaxane Nanosheet

Pseudopolyrotaxane nanosheets (PPRNS) are ultrathin two-dimensional (2D) materials fabricated via supramolecular self-assembly of β-cyclodextrin (β-CD) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers. In this study, the molecular loading of various fluorescent probe molecules onto PPRNS was systematically investigated. ¹H NMR study for R6G absorption to PPRNS indicated that the small hydrophobic groups, such as the methyl group, of R6G were absorbed by PPRNS. Consistently, the fluorescent probes without methyl groups were not absorbed. These results indicate that PPRNS has a molecular recognition absorption property based on the host-guest interaction of the functional groups on probe molecules and molecular-sized spaces of PPRNS surfaces, which may be vacant β-CDs and voids between β-CD columns. The absorbed amount of the molecular probes onto PPRNS was investigated by UV-vis spectra, and the absorption behavior could be described well by the Langmuir absorption isotherm. This is consistent with the suggested model that the probes are absorbed onto the PPRNS surfaces. This study demonstrates that PPRNSs can be applied as adsorbents for toxic compounds, drug delivery systems, and 2D sensors.

Extrusion 3D Printing of Polymeric Materials with Advanced Properties

3D printing is a rapidly growing technology that has an enormous potential to impact a wide range of industries such as engineering, art, education, medicine, and aerospace. The flexibility in design provided by this technique offers many opportunities for manufacturing sophisticated 3D devices. The most widely utilized method is an extrusion-based solid-freeform fabrication approach, which is an extremely attractive additive manufacturing technology in both academic and industrial research communities. This method is versatile, with the ability to print a range of dimensions, multimaterial, and multifunctional 3D structures. It is also a very affordable technique in prototyping. However, the lack of variety in printable polymers with advanced material properties becomes the main bottleneck in further development of this technology. Herein, a comprehensive review is provided, focusing on material design strategies to achieve or enhance the 3D printability of a range of polymers including thermoplastics, thermosets, hydrogels, and other polymers by extrusion techniques. Moreover, diverse advanced properties exhibited by such printed polymers, such as mechanical strength, conductance, self-healing, as well as other integrated properties are highlighted. Lastly, the stimuli responsiveness of the 3D printed polymeric materials including shape morphing, degradability, and color changing is also discussed.

Direct Ink Writing Based 4D Printing of Materials and Their Applications

4D printing has attracted academic interest in the recent years because it endows static printed structures with dynamic properties with the change of time. The shapes, functionalities, or properties of the 4D printed objects could alter under various stimuli such as heat, light, electric, and magnetic field. Briefly, 4D printing is the development of 3D printing with the fourth dimension of time. Among the fabrication techniques that have been employed for 4D printing, the direct ink writing technique shows superiority due to its open source for various types of materials. Herein, the state-of-the-art achievements about the topic of 4D printing through direct ink writing are summarized. The types of materials, printing strategies, actuated methods, and their potential applications are discussed in detail. To date, most efforts have been devoted to shape-shifting materials, including shape memory polymers, hydrogels, and liquid crystal elastomers, showing great prospects in areas ranging from the biomedical field to robotics. Finally, the current challenges and outlook toward 4D printing based on direct ink writing are also pointed out to leave open a significant space for future innovation.

100th Anniversary of Macromolecular Science Viewpoint: Macromolecular Materials for Additive Manufacturing

Additive manufacturing (AM) has drawn tremendous attention as a versatile platform for the on-demand fabrication of objects with excellent spatial control of chemical compositions and complex architectures. The development of materials that are specifically designed for AM is highly desirable for a variety of applications ranging from personal healthcare, tissue engineering, biomedical devices, self-folding origami structures, and soft robotics. Polymeric macromolecules have received increasing attention due to a wide variety of materials, the versatility for novel chemistries, and the ability to tune chemical composition and architecture. This Viewpoint highlights the development of polymeric materials for direct-ink writing and vat photopolymerization for 3D printing applications. Recent chemical innovations and polymer architectures are overviewed, which also includes recent developments in responsive and adaptive objects from AM. Polymers for biological interface and sustainability in AM are also discussed.

Structural properties of contractile gels based on light-driven molecular motors: a small-angle neutron and X-ray study

The detailed structure of active polymer gels built by integrating light-driven rotary molecular motors as reticulation units in polymer networks is discussed as a function of gel composition. Upon light-irradiation, the collective rotation of molecular motors is translated into the macroscopic contraction of the gels through polymer chains twisting. The major role of the characteristic ratio c/c* (c* being the overlap concentration of the polymer-motor conjugates before crosslinking) on the contraction efficiency is exploited. Combined small-angle neutron and X-ray scattering experiments reveal the importance of heterogeneities in the macroscopic contraction process: the mesh size of the network increases under irradiation in the whole range of c/c*, an increase that is maximal for c/c* = 1; i.e. at higher contraction efficiency. Furthermore, the mesh size of the network reaches equilibrium within a short period of time, while the heterogeneities increase in size untill the end of the contraction process. Finally, the significant motorized twisting of polymer chains within the network allows to foresee the design of new storage energy systems.

The Future of Molecular Machines

Artificial molecular machines have captured the imagination of scientists and nonscientists alike for decades now, given their clear potential to transform and enhance all aspects of human life. In this Outlook, I use a bicycle as an analogy to explain what a molecular machine is, in my opinion, and work through a representative selection of case studies to specify the significant accomplishments made to date, and the obstacles that currently stand between these and the field's fulfillment of its great potential. The hope of this intentionally sober account is to sketch a path toward a rich and exciting research trajectory that might challenge current practitioners and attract junior scientists into its fold. Considering the progress we have witnessed in the past decade, I am positive that the future of the field is a rosy one.

Biocompatible supramolecular pseudorotaxane hydrogels for controllable release of doxorubicin in ovarian cancer SKOV-3 cells

A series of injectable and biocompatible delivery DOX-loaded supramolecular hydrogels were fabricated by using presynthesized DOX-2N-β-CD, Pluronic F-127 and α-CD through host–guest interactions and cooperative multivalent hydrogen bonding interactions. The compositions and morphologies of these hydrogels were confirmed by PXRD and SEM measurements. Moreover, the Rheological measurements of these hydrogels were studied and the studies found that they showed a unique thixotropic behavior, indicting a fast self-healing property after the continuous oscillatory shear stress. Using α-CD as a capping agent, slow and sustained DOX release was observed at different pH values after 72 h. The amount of DOX released at pH 7.4 was determined to be 49.0% for hydrogel 1, whereas the releasing amount of the DOX was increased to 66.3% for hydrogel 1 during the same period at pH 5.5 (P < 0.05), indicating a higher release rate of the drug under more acidic conditions. Taking hydrogel 1 as a representative material, the toxicities of DOX and hydrogel 1 on ovarian cancer cells (SKOV-3) at different exposure durations were examined. The results revealed that hydrogel 1 was less cytotoxic than free DOX to SKOV-3 cells (P < 0.05), suggesting sustained release by these hydrogels in the presence of ovarian cancer cells. It is anticipated that this exploration can provide a new strategy for preparing drug delivery systems.

A series of injectable and biocompatible delivery DOX-loaded supramolecular hydrogels were fabricated by using presynthesized DOX-2N-β-CD, Pluronic F-127 and α-CD through host–guest interactions and cooperative multivalent hydrogen bonding interactions.

Polyrotaxanes created by end-capping polypseudorotaxanes self-assembled from β-CDs with distal azide terminated PHEMA using propargylamine monosubstituted β-CDs

When a distal azide terminated PHEMA was allowed to self-assemble with varying amounts of β-CDs in water, followed by in situ reaction with PA-β-CDs via the CuAAC, linear polyrotaxanes (PRs) and a mixture of linear and hyperbranched PRs were obtained.

Thermo-responsive 3D-printed polyrotaxane monolith

Thermo-responsive 3D-printed hydrogels that are composed of methylated α-cyclodextrin polyrotaxanes have been synthesized through post-3D-printing methylation.

Design of Collective Motions from Synthetic Molecular Switches, Rotors, and Motors

Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.

Mechanical behaviour of contractile gels based on light-driven molecular motors

The networking of individual artificial molecular motors into collective actuation systems is a promising approach for the design of active materials working out of thermodynamic equilibrium. Here, we report the first mechanical studies on active polymer gels built by integrating light-driven rotary molecular motors as reticulation units in polymer networks. We correlate the volume ratio before and after light irradiation with the change of the elastic modulus, and we reveal the universal maximum mechanical efficiency of such gels related to their critical overlap concentration before chemical reticulation. We also show the major importance of heterogeneities in the macroscopic contraction process and we confirm that these materials can increase their internal energy by the motorized winding of their polymer chains.

Radical free crosslinking of direct-write 3D printed hydrogels through a base catalyzed thiol-Michael reaction

3D printed micelle-based hydrogels were mechanically stabilized and crosslinked through the base catalyzed thiol-Michael addition in PBS buffer, without the use of potentially cytotoxic radical chemistry.

Hydrogel Interferometry for Ultrasensitive and Highly Selective Chemical Detection

Developing ultrasensitive chemical sensors with small scale and fast response through simple design and low-cost fabrication is highly desired but still challenging. Herein, a simple and universal sensing platform based on a hydrogel interferometer with femtomol-level sensitivity in detecting (bio)chemical molecules is demonstrated. A unique local concentrating effect (up to 10⁹ folds) in the hydrogel induced by the strong analyte binding and large amount of ligands, combined with the signal amplification effect by optical interference, endows this platform with an ultrahigh sensitivity, specifically 10^-14 m for copper ions and 1.0 × 10^-11 mg mL^-1 for glycoprotein with 2-4 order-of-magnitude enhancement. The specific chemical reactions between selected ligands and target analytes provide high selectivity in detecting complex fluids. This universal principle with broad chemistry, simple physics, and modular design allows for high performance in detecting wide customer choices of analytes, including metal ions and proteins. The scale of the sensor can be down to micrometer size. The nature of the soft gel makes this platform transparent, flexible, stretchable, and compatible with a variety of substrates, showing high sensing stability and robustness after 200 cycles of bending or stretching. The outstanding sensing performance grants this platform great promise in broad practical applications.

3D-Printable Photochromic Molecular Materials for Reversible Information Storage

The formulation of advanced molecular materials with bespoke polymeric ionic-liquid matrices that stabilize and solubilize hybrid organic-inorganic polyoxometalates and allow their processing by additive manufacturing, is effectively demonstrated. The unique photo and redox properties of nanostructured polyoxometalates are translated across the scales (from molecular design to functional materials) to yield macroscopic functional devices with reversible photochromism. These properties open a range of potential applications including reversible information storage based on controlled topological and temporal reduction/oxidation of pre-formed printed devices. This approach pushes the boundaries of 3D printing to the molecular limits, allowing the freedom of design enabled by 3D printing to be coupled with the molecular tuneability of polymerizable ionic liquids and the photoactivity and orbital engineering possible with hybrid polyoxometalates.

A novel supramolecular polymer network based on a catenane-type crosslinker

A novel supramolecular mechanically interlocked crosslinker was designed and used to prepare a supramolecular polymer network.

Bistable [c2] Daisy Chain Rotaxanes as Reversible Muscle-like Actuators in Mechanically Active Gels

The implementation of molecular machines in polymer science is of high interest to transfer mechanical motions from nanoscale to macroscale in order to access new kinds of active devices and materials. Toward this objective, thermodynamic and topological aspects need to be explored for reaching efficient systems capable of producing a useful work. In this paper we describe the branched polymerization of pH-sensitive bistable [c2] daisy chain rotaxanes by using copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition ("click chemistry"). With this cross-linked topology, the corresponding materials in the form of chemical gels can be contracted and expanded over a large variation of volume (∼50%) by changing the protonation state of the system. HR-MAS ¹H NMR and neutron scattering experiments reveal that this macroscopic response of the gels results from the synchronized actuation of the mechanical bonds at the molecular level.

Hydrazone switches and things in between

This feature article surveys the various ways by which a structurally simple hydrazone can be used in accessing different functional materials, mainly photo/chemically activated switches, fluorophores and sensors.