Hot Melt Super Glue: Multi-Recyclable Polyphenol-Based Supramolecular Adhesives

Coacervate-Derived Assembly of Poly(ethylene glycol) Nanoparticles for Combinational Tumor Therapy

Coacervates have garnered significant attention as potential drug carriers. However, the instability resulting from their intrinsic membrane-free nature restricts the application of coacervates in drug delivery. Herein, the engineering of poly(ethylene glycol) nanoparticles (PEG NPs) is reported using coacervates composed of PEG and polyphenols as the templates, where PEG is subsequently cross-linked based on different chemistries (e.g., thiol-disulfide exchange, click chemistry, and Schiff base reaction). The reported assembly strategy avoids the template removal process and the resultant PEG NPs exhibit excellent stability in the physiological environment compared to coacervates. The presence of polyphenols in PEG NPs enables the loading of various cargos including metal ions (i.e., Ru, Gd, Mn, Fe) and drug molecules (i.e., doxorubicin), which demonstrates their promise in magnetic resonance imaging and combinational tumor therapy. This work provides a promising strategy to promote the development of coacervate-derived NPs as a drug delivery system for biomedical applications.

Self-Healing, Electrically Conductive, Antibacterial, and Adhesive Eutectogel Containing Polymerizable Deep Eutectic Solvent for Human Motion Sensing and Wound Healing

Flexible electronic devices such as wearable sensors are essential to advance human-machine interactions. Conductive eutectogels are promising for wearable sensors, despite their challenges in self-healing and adhesion properties. This study introduces a multifunctional eutectogel based on a novel polymerizable deep eutectic solvent (PDES) prepared by the incorporation of diallyldimethylammonium chloride (DADMAC) and glycerol in the presence of polycyclodextrin (PCD)/dopamine-grafted gelatin (Gel-DOP)/oxidized sodium alginate (OSA). The synthesized eutectogel has reversible Schiff-base bonds, hydrogen bonds, and host-guest interactions, which enable rapid self-healing upon network disruption. GPDO-15 eutectogel has significant tissue adhesion, high stretchability (419%), good ionic conductivity (0.79 mS·cm-1), and favorable antibacterial and self-healing properties. These eutectogels achieve 90% antibacterial effect, show excellent biocompatibility, and can be used as sensors to monitor human activities with strong stability and durability. The in vivo studies indicate that the eutectogels can improve the wound healing process which makes them an effective option for biological dressings.

Rigid-Flexible Coupled Dendritic Molecule Doping: General Approach to Activate Commercial Polymers into Harsh Condition-Tolerant Multi-Reusable Strong Supramolecular Adhesives

Developing functional adhesives combining strong adhesion, good recyclability and diverse harsh-condition adaptability is a grand challenge. Here, we introduce a general dendritic molecule doping strategy to activate commercial polymers into a new family of supramolecular adhesives integrating high adhesion strength, ultralow temperature, water resistant and multi-reusable properties. Our method involves rational design of a new rigid-flexible coupled dendritic molecule-M4C8OH as a versatile dopant, while simple M4C8OH doping into commercial polymers can modulate internal and external non-covalent interaction to enable H-bonding enhanced interchain cross-linking for tough cohesion along with enhanced interphase interaction. This endows 20 wt % M4C8OH-doped polycaprolactone (PCL) adhesives (PCL-M4C8OH) with improved adhesion strength on various substrates with the maximum increase up to 2.87 times that of PCL. In particular, the adhesion strengths of PCL-M4C8OH on polymethyl methacrylate at 25 °C and -196 °C reach 4.67 and 3.58 MPa-1.9 and 2.3 times those of PCL and superior to diverse commercial adhesives and most reported adhesives. PCL-M4C8OH also displays markedly-improved multi-usability and tolerance against ultralow temperature and diverse wet environments. Mechanism studies reveal the crucial role of M4C8OH molecular structures toward superior adhesion. Our method can be expanded to other polymer matrices, yielding diverse new supramolecular adhesives.

Freezing-Tolerant Supramolecular Adhesives from Tannic Acid-Based Low-Transition-Temperature Mixtures

Natural polyphenols like tannic acid (TA) have recently emerged as multifunctional building blocks for designing advanced materials. Herein, we show the benefits of having TA in a dynamic liquid state using low-transition-temperature mixtures (LTTMs) for developing freezing-tolerant glues. TA was combined with betaine or choline chloride to create LTTMs, which direct the self-assembly of guanosine into supramolecular viscoelastic materials with high adhesion. Molecular dynamics simulations showed that the structural properties of the material are linked to strong hydrogen bonding in TA-betaine and TA-choline chloride mixtures. Notably, long-term and repeatable adhesion was achieved even at -196 °C due to the binding ability of TA's catechol and gallol units and the mixtures' glass transition temperature. Additionally, the adhesives demonstrated injectability and low toxicity against fibroblasts in vitro. These traits reveal the potential of these systems as bioadhesives for tissue repair, opening new avenues for creating multifunctional soft materials with bioactive properties.

Supramolecular Ionogels for Use in Locating Damage to Underwater Infrastructure

The capacity to self-detect and locate damage to underwater infrastructure in emergencies is vital, as materials and technologies that securely facilitate energy and information transmission are crucial in several fields. Herein, the development of a multifunctional supramolecular ionogel (SIG) and SIG-based devices for use in detecting and locating damage to underwater infrastructure is reported. The SIG is fabricated via the single-step photoinitiated copolymerization of hydroxy and fluorinated monomers in a fluorinated ionic liquid. Hydrogen-bond/ion-dipole-interaction synergy ensures that the SIG is highly ionically conductive and extremely mechanically strong, with underwater self-healing and adhesion properties. It can be used as an underwater ionic cable to provide reporting signals via changes in strain; furthermore, SIG-based devices can be fixed to underwater infrastructure to locate damage via resistance monitoring. The SIG can also be attached to the human body for use in underwater communication, thereby safeguarding maintenance personnel while repairing underwater infrastructure. This study provides a novel pathway for developing supramolecular materials and devices.

A polyethylene glycol-grafted pullulan polysaccharide adhesive improves drug loading capacity and release efficiency

In this study, polyethylene glycol was grafted onto pullulan polysaccharides, resulting in the development of a novel adhesive termed PLUPE, offering superior drug loading capacity and rapid release efficiency. The efficacy of PLUPE was rigorously evaluated through various tests, including the tack test, shear strength test, 180° peel strength test, and human skin adhesion test. The results demonstrated that PLUPE exhibited a static shear strength that was 4.6 to 9.3 times higher than conventional PSAs, ensuring secure adhesion for over 3 days on human skin. A comprehensive analysis, encompassing electrical potential evaluation, calculation of interaction parameters, and FT-IR spectra, elucidated why improved the miscibility between the drug and PSAs, that the significant enhancement of intermolecular hydrogen bonding in the PLUPE structure. ATR-FTIR, rheological, and thermodynamic analyses further revealed that the hydrogen bonding network in PLUPE primarily interacted with polar groups in the skin. This interaction augmented the fluidity and free volume of PSA molecules, thereby promoting efficient drug release. The results confirmed the safety profile of PLUPE through skin irritation tests and MTT assays, bolstering its viability for application in TDDS patches. In conclusion, PLUPE represented a groundbreaking adhesive solution for TDDS patches, successfully overcoming longstanding challenges associated with PSAs.

Upcycling Waste Thermosetting Polyimide Resins into High-Performance and Sustainable Low-Temperature-Resistance Adhesives

Thermosetting polyimide (PI) has attracted extensive attention for its excellent properties, but the approaches to its end-of-life management are not sustainable, posing great threat to the ecosystem. Herein, this work proposes a mild, sustainable, and full recovery path for recycling waste carbon fiber reinforced phenylethynyl end-capped PI resin composites. In addition to recycling reaction reagent and woven carbon fiber, degraded products (DPETI) can be fully and directly used as high-performance and sustainable adhesives. DPETI exhibits strong adhesion to various surfaces, with a maximum adhesion strength of 1.84 MPa. Due to the strong supramolecular polymerization behavior without solvent dependence, DPETI demonstrates higher adhesive strength of 2.22 MPa in the extreme environment (-196 °C), which is maintained even after 10 cycles. This work sparks a new thinking for plastic wastes recycling that is to convert unrecyclable wastes into new and sustainable materials, which has the potential to establish new links within circular economies and influence the development of materials science.

A Mesostructure Multivariant-Assembly Reinforced Ultratough Biomimicking Superglue

The imitation of mussels and oysters to create high-performance adhesives is a cutting-edge field. The introduction of inorganic fillers is shown to significantly alter the adhesive's properties, yet the potential of mesoporous materials as fillers in adhesives is overlooked. In this study, the first report on the utilization of mesoporous materials in a biomimetic adhesive system is presented. Incorporating mesoporous silica nanoparticles (MSN) profoundly enhances the adhesion of pyrogallol (PG)-polyethylene imine (PEI) adhesive. As the MSN concentration increases, the adhesion strength to glass substrates undergoes an impressive fivefold improvement, reaching an outstanding 2.5 mPa. The adhesive forms an exceptionally strong bond, to the extent that the glass substrate fractures before joint failure. The comprehensive tests involving various polyphenols, polymers, and fillers reveal an intriguing phenomenon-the molecular structure of polyphenols significantly influences adhesive strength. Steric hindrance emerges as a crucial factor, regulating the balance between π-cation and charge interactions, which significantly impacts the multicomponent assembly of polyphenol-PEI-MSN and, consequently, adhesive strength. This groundbreaking research opens new avenues for the development of novel biomimetic materials.

Robust and multifunctional natural polyphenolic composites for water remediation

The scarcity of clean water has become a global environmental problem which constrains the development of public health, economy, and sustainability. In recent years, natural polyphenols have drawn increasing interests as promising platforms towards diverse water remediation composites and devices, owing to their abundant and renewable resource in nature, highly active surface chemistry, and multifunctionality. This review aims to summarize the most recent advances and highlights of natural polyphenol-based composite materials (e.g., nanofibers, membranes, particles, and hydrogels) for water remediation, by focusing on their structural and functional features, as well as their diversified applications including membrane filtration, solar distillation, adsorption, advanced oxidation processes, and disinfection. Finally, the future challenges in this field are also prospected. It is anticipated that this review will provide new opportunities towards the future development of natural polyphenols and other kinds of naturally occurring molecules in water purification applications.

Smart Internal Bio-Glues

Although smart bio-glues have been well documented, the development of internal bio-glues for non-invasive or minimally invasive surgery is still met with profound challenges such as safety risk and the lack of deep tissue penetration stimuli for internal usage. Herein, a series of smart internal bio-glues are developed via the integration of o-nitrobenzene modified biopolymers with up-conversion nanoparticles (UCNPs). Upon irradiation by near-infrared (NIR) light, the prepared smart bio-glues can undergo a gelation process, which may further induce strong adhesion between tissues under both dry and wet conditions based on multi-interactions. Moreover, those NIR light-responsive bio-glues with deeper tissue penetration ability demonstrate good biocompatibility, excellent hemostatic performance, and the potent ability to accelerate wound healing for both external and internal wounds. This work provides new opportunities for minimally invasive surgery, especially in internal wound healing using smart and robust bio-glues.

Robust Natural Polyphenolic Adhesives against Various Harsh Environments

Although adhesive hydrogels have been extensively explored, the development of adhesives with long-term strong adhesion capacity under various harsh environments is still met with profound challenges such as sophisticated preparation, long-term curing, and low bonding strength. Herein, a series of robust adhesive hydrogels have been developed via the polyphenol-epoxy-cross-linking (PEC) reactions between natural polyphenols (extracts) and epoxy glycidyl ethers. The as-prepared natural polyphenolic adhesive hydrogels could induce strong adhesion onto several kinds of typical substrates (i.e., wood, glass, paper, PET, PMMA, and Fe) under both dry and wet conditions based on multi-interactions. Moreover, those natural polyphenolic adhesives exhibited good low-temperature and solvent resistance performances, which could be widely used in different kinds of device repairment (i.e., chemical, petroleum, wood, metal, glass, plastic, rubber, and other industries) under different conditions. This work could provide new opportunities toward natural-inspired robust adhesives in various fields ranging from chemical transportation, industrial manufacturing, architectural design, and marine engineering to daily life.

Supramolecular Polymeric Pressure-Sensitive Adhesive That Can Be Directly Operated at Low Temperatures

Low-temperature adhesion is ubiquitous in daily life and industry. However, most supramolecular adhesives are thermoplastic materials that require heating during the adhesion. Herein, a supramolecular approach is used to construct unique pressure-sensitive adhesives (PSAs) that can be directly operated at low temperatures (-60 °C). Supramolecular polymerization between phytic acid (PA) and water (H) endows poly(PA-H)s with excellent mechanical properties and low temperature adhesion capacity. Poly(PA-H)s can easily be processed into PSA tapes, pastes, and particles. Poly(PA-H)s were directly adhered to various surfaces by pressing at low temperatures (0 to -60 °C). No heating or high-temperature-induced solid-liquid transition was required for the low-temperature adhesion of poly(PA-H)s. With the help of structural water units in supramolecular polymers, poly(PA-H)s showed strong, stable, and organic solvent resistant adhesion performances at low temperatures, with adhesion strength of up to 3.61 MPa at -60 °C.