Recycling of Polyurethane Foams via Glycolysis: A Review.

Polyurethane foams constitute highly problematic waste due to their low density and consequently large volume. Among the most promising recycling approaches, the glycolysis of polyurethane waste stands out and was extensively discussed in this article. Existing literature reviews lack a detailed analysis of glycolysis processes and a clear presentation of the most important data. However, in this review, the scientific literature on glycolysis has been thoroughly examined and updated with the latest research in the field. The article provides an overview of glycolysis methods, categorized into rigid and flexible foams, along with a review of the catalysts and process conditions employed. Additionally, this study offers a comprehensive analysis of industrial methods protected by active patents, which has not been previously explored in the literature. This detailed examination of patent information adds significant value to the review and distinguishes it from others. Furthermore, this review also aims to introduce the main types of polyurethanes and their properties. It outlines the fundamentals of recycling strategies, thermomodernization trends, and environmental considerations, highlighting the critical role of recycling in the industry. The article serves as a complete foundation for exploring new alternative methods in this field.

Flame Retardancy and Thermal Stability of Rigid Polyurethane Foams Filled with Walnut Shells and Mineral Fillers.

Recently, the influence of the concept of environmental sustainability has increased, which includes environmentally friendly measures related to reducing the consumption of petrochemical fuels and converting post-production feedstocks into raw materials for the synthesis of polymeric materials, the addition of which would improve the performance of the final product. In this regard, the development of bio-based polyurethane foams can be carried out by, among other things, modifying polyurethane foams with vegetable or waste fillers. This paper investigates the possibility of using walnut shells (WS) and the mineral fillers vermiculite (V) and perlite (P) as a flame retardant to increase fire safety and thermal stability at higher temperatures. The effects of the fillers in amounts of 10 wt.% on selected properties of the polyurethane composites, such as rheological properties (dynamic viscosity and processing times), mechanical properties (compressive strength, flexural strength, and hardness), insulating properties (thermal conductivity), and flame retardant properties (e.g., ignition time, limiting oxygen index, and peak heat release) were investigated. It has been shown that polyurethane foams containing fillers have better performance properties compared to unmodified polyurethane foams.

Vanillic Acid-based Pro-coagulant Hemostatic Shape Memory Polymer Foams with Antimicrobial Properties against Drug-resistant Bacteria.

Uncontrolled bleeding is the primary cause of trauma-related death. For patients that are brought to the hospital in time to receive treatment, there is a great risk of contracting drug-resistant bacterial wound infections. Therefore, low-cost hemostatic agents with procoagulant and antibacterial properties are essential to reduce morbidity and mortality in patients with traumatic wounds. To that end, we introduced vanillic acid (VA) into shape memory polymer (SMP) foams through a dual incorporation mechanism to make dual vanillic acid (DVA) foams. The dual mechanism increases VA loading while allowing burst and sustained delivery of VA from foams. DVA foams exhibit antimicrobial and antibiofilm properties against native and drug-resistant Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis. Also, DVA foams inhibit the growth rate of both methicillin-sensitive and -resistant S. aureus colonies to limit their size and promote small colony variants. DVA SMP foams induce primary and secondary hemostasis in in vitro blood interaction studies. As a proof of concept, we demonstrated easy delivery and rapid clotting in a porcine liver injury model, indicating DVA foam feasibility for use as a hemostatic dressing. Thus, the inexpensive production of DVA SMP foams could enable a cost-effective procoagulant hemostatic dressing that is resistant to bacterial colonization to improve short- and long-term outcomes for hemorrhage control in traumatically injured patients. STATEMENT OF SIGNIFICANCE: Uncontrolled bleeding is the primary cause of preventable death on the battlefield. Of patients that survive, ∼40% develop polymicrobial infections within 5 days of injury. Drug-resistant infections are anticipated to cause more deaths than all cancers combined by 2050. Therefore, novel non-drug-based biomaterials strategies for infection control in wound care are increasingly important. To that end, we developed hemostatic polyurethane foams that include antimicrobial and pro-coagulant vanillic acid, a plant-based antimicrobial species. These foams provide excellent protection against native and drug-resistant bacteria and enhanced coagulation while remaining cytocompatible. In a pilot porcine liver injury model, vanillic acid-containing foams stabilized a bleed within <5 minutes. These biomaterials provide a promising solution for both hemorrhage and infection control in wound care.

Preparation and Characterization of Fluorinated Acrylate and Epoxy Co-Modified Waterborne Polyurethane.

Conventional waterborne polyurethane (WPU) has poor water resistance and poor overall performance, which limits its application in outdoor coatings. A solution to this problem is urgently needed. The introduction of fluorine-containing groups can effectively improve the water resistance of WPU. In this study, a new fluorinated chain extender (HFBMA-HPA) synthesized by free radical copolymerization and epoxy resin (E-44) were used to co-modify WPU, and five waterborne fluorinated polyurethane (WFPU) emulsions with different fluorine contents were prepared by the self-emulsification method. The effects of HFBMA-HPA content on the emulsion particle properties, coating surface properties, mechanical properties, water resistance, thermal stability, and corrosion resistance were investigated. The results showed that the WFPU coating had excellent thermal stability, corrosion resistance, and mechanical properties. As the content of HFBMA-HPA increased from 0 wt% to 14 wt%, the water resistance of the WFPU coating gradually increased, the water contact angle (WCA) increased from 73° to 98°, the water absorption decreased from 7.847% to 3.062%, and the surface energy decreased from 32.8 mN/m to 22.6 mN/m. The coatings also showed impressive performances in the adhesion and flexibility tests in extreme conditions. This study provides a waterborne fluorinated polyurethane material with excellent comprehensive performance that has potential application value in the field of outdoor waterproof and anticorrosion coatings.

Flexible Ti3C2Tx-Polyurethane Electrodes for Versatile Wearable Applications.

With the development of science and technology, wearable electronics are increasingly widely used in medical, environmental monitoring, and other fields. Thus, the demand for flexible electrodes is increasing. The two-dimensional material Ti3C2Tx has attracted much attention in the manufacture of flexible electrodes due to its excellent mechanical and electrical properties. However, the brittleness of pure Ti3C2Tx films has become a major obstacle for their use as flexible electrodes in wearable devices. Therefore, solving the brittleness problem of flexible electrodes based on Ti3C2Tx while maintaining the excellent performance of Ti3C2Tx has become an urgent problem. To solve this problem, Ti3C2Tx was compounded with waterborne polyurethane (WPU), and a Ti3C2Tx-WPU composite film with a hierarchical structure was constructed by evaporation-assisted self-assembly. The Ti3C2Tx-WPU composite film not only retains the excellent electrical conductivity of Ti3C2Tx (100 S m-1) but also has flexibility (20 MJ m-3). Furthermore, the Ti3C2Tx-WPU composite film is applied to functional devices such as contact pressure sensors and non-contact proximity sensors. Finally, the Ti3C2Tx-WPU composite film wearable device demonstrates its practical application potential in the field of wearable devices.

Photo-Crosslinked Polyurethane-Containing Gel Polymer Electrolytes via Free-Radical Polymerization Method.

Using a novel technique, crosslinked gel polymer electrolytes (GPEs) designed for lithium-ion battery applications have been created. To form the photo crosslink via free-radical polymerization, a mixture of polyurethane acrylate (PUA), polyurethane methacrylate (PUMA), vinyl phosphonic acid (VPA), and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) was exposed to ultraviolet (UV) radiation during the fabrication process. The unique crosslinked configuration of the membrane increased its stability and made it suitable for use with liquid electrolytes. The resulting GPE has a much higher ionic conductivity (1.83 × 10-3 S cm-1) than the commercially available Celgrad2500 separator. A crosslinked structure formed by the hydrophilic properties of the PUA-PUMA blend and the higher phosphate content from BMEP reduced the leakage of the electrolyte solution while at the same time providing a greater capacity for liquid retention, significantly improving the mechanical and thermal stability of the membrane. GPP2 shows electrochemical stability up to 3.78 V. The coin cell that was assembled with a LiFePO4 cathode had remarkable cycling characteristics and generated a high reversible capacity of 149 mA h g-1 at 0.1 C. It also managed to maintain a consistent Coulombic efficiency of almost 100%. Furthermore, 91.5% of the original discharge capacity was maintained. However, the improved ionic conductivity, superior electrochemical performance, and high safety of GPEs hold great promise for the development of flexible energy storage systems in the future.

Numerical Investigation of Fracture Behaviour of Polyurethane Adhesives under the Influence of Moisture.

The mechanical behaviour of polymer adhesives is influenced by the environmental conditions leading to ageing and affecting the integrity of the material. The polymer adhesives have hygroscopic behaviour and tend to absorb moisture from the environment, causing the material to swell without applying external load. The focus of the work is to investigate the viscoelastic material behaviour under ageing conditions. The constitutive equations and the governing equations to numerically investigate the fracture in swollen viscoelastic material are discussed to describe the numerical implementation. Phase-field damage modelling has been used in numerical studies of ductile and brittle materials for a long time. The finite-strain phase-field damage model is used to investigate the fracture behaviour in aged viscoelastic polymer adhesives. The finite-strain viscoelastic model is formulated based on the continuum rheological model by combining spring and Maxwell elements in parallel. Commercially available post-cured crosslinked polyurethane adhesives are used in the current investigation. Post-cured samples of crosslinked polyurethane adhesives are prepared for different humidity conditions under isothermal conditions. These aged samples are used to perform tensile and tear tests and the test data are used to identify the material parameters from the curve fitting process. The experiment and simulation are compared to relate the findings and are the first step forward to improve the method to model crosslinked polymers.

Polymer Bionanocomposites Based on a P3BH/Polyurethane Matrix with Organomodified Montmorillonite-Mechanical and Thermal Properties, Biodegradability, and Cytotoxicity.

In the present work, hybrid nanobiocomposites based on poly(3-hydroxybutyrate), P3HB, with the use of aromatic linear polyurethane as modifier and organic nanoclay, Cloisite 30B, as a nanofiller were produced. The aromatic linear polyurethane (PU) was synthesized in a reaction of diphenylmethane 4,4'-diisocyanate and polyethylene glycol with a molecular mass of 1000 g/mole. The obtained nanobiocomposites were characterized by the small-angle X-ray scattering technique, scanning electron microscopy, Fourier infrared spectroscopy, thermogravimetry, and differential scanning calorimetry, and moreover, their selected mechanical properties, biodegradability, and cytotoxicity were tested. The effect of the organomodified montmorillonite presence in the biocomposites on their properties was investigated and compared to those of the native P3HB and the P3HB-PU composition. The obtained hybrid nanobiocomposites have an exfoliated structure. The presence and content of Cloisite 30B influence the P3HB-PU composition's properties, and 2 wt.% Cloisite 30B leads to the best improvement in the aforementioned properties. The obtained results indicate that the thermal stability and mechanical properties of P3HB were improved, particularly in terms of increasing the degradation temperature, reducing hardness, and increasing impact strength, which were also confirmed by the morphological analysis of these bionanocomposites. However, the presence of organomodified montmorillonite in the obtained polymer biocomposites decreased their biodegradability slightly. The produced hybrid polymer nanobiocomposites have tailored mechanical and thermal properties and processing conditions for their expected application in the production of biodegradable, short-lived products for agriculture. Moreover, in vitro studies on human skin fibroblasts and keratinocytes showed their satisfactory biocompatibility and low cytotoxicity, which make them safe when in contact with the human body, for instance, in biomedical applications.

Molecular Simulation Analysis of Polyurethane Molecular Structure under External Electric Field.

Polyurethane (PU) materials are extensively utilized in power equipment. This paper introduces a comprehensive evaluation method that combines electromagnetics and computational chemistry based on the Density Functional Theory (DFT) to elucidate the impact of external electric fields on the molecular structure of PU during electrical contact. The study focuses on the microstructural and molecular energy changes in the hard (HS) and soft (SS) segments of PU under the influence of an electric field of uniform intensity. Findings indicate that the total energy of HS molecules decreases markedly as the electric field intensity increases, accompanied by a significant rise in both the dipole moment and polarizability. Conversely, the total energy and polarizability of the SS molecules decrease, while the dipole moment experiences a slight increase. Under the influence of a strong electric field, HS molecules tend to stretch towards the extremities of the main chain, leading to structural instability and the cleavage of hydroxyl O-H bonds. Meanwhile, the carbon chain of the SS molecules twists towards the center under the electric field, with no chemical bond rupture observed. At an electric field intensity of 8.227 V/nm, the HOMO-LUMO gap of the HS molecule narrows sharply, signifying a rapid decline in the molecular structure stability, corroborated by infrared spectroscopy analysis. These findings offer theoretical insights and guidance for the modification of PU materials in power equipment applications.

Motion Sensing by a Highly Sensitive Nanogold Strain Sensor in a Biomimetic 3D Environment.

Recent advancements in flexible electronics have highlighted their potential in biomedical applications, primarily due to their human-friendly nature. This study introduces a new flexible electronic system designed for motion sensing in a biomimetic three-dimensional (3D) environment. The system features a self-healing gel matrix (chitosan-based hydrogel) that effectively mimics the dynamics of the extracellular matrix (ECM), and is integrated with a highly sensitive thin-film resistive strain sensor, which is fabricated by incorporating a cross-linked gold nanoparticle (GNP) thin film as the active conductive layer onto a biocompatible microphase-separated polyurethane (PU) substrate through a clean, rapid, and high-precision contact printing method. The GNP-PU strain sensor demonstrates high sensitivity (a gauge factor of ∼50), good stability, and waterproofing properties. The feasibility of detecting small motion was evaluated by sensing the beating of human induced pluripotent stem cell (hiPSC)-derived cardiomyocyte spheroids embedded in the gel matrix. The integration of these components exemplifies a proof-of-concept for using flexible electronics comprising self-healing hydrogel and thin-film nanogold in cardiac sensing and offers promising insights into the development of next-generation biomimetic flexible electronic devices.

[Research progress of electrospinning polyurethane fiber in the field of biomedical tissue engineering].

Polyurethane materials have good biocompatibility, blood compatibility, mechanical properties, fatigue resistance and processability, and have always been highly valued as medical materials. Polyurethane fibers prepared by electrostatic spinning technology can better mimic the structure of natural extracellular matrices (ECMs), and seed cells can adhere and proliferate better to meet the requirements of tissue repair and reconstruction. The purpose of this review is to present the research progress of electrostatically spun polyurethane fibers in bone tissue engineering, skin tissue engineering, neural tissue engineering, vascular tissue engineering and cardiac tissue engineering, so that researchers can understand the practical applications of electrostatically spun polyurethane fibers in tissue engineering and regenerative medicine.

Polycyclic aromatic hydrocarbon derivatives onto polar microplastics of polyurethane: equilibrium, thermodynamics, and kinetics of monolayer-multilayer adsorption.

The study of the adsorption of polycyclic aromatic hydrocarbons on microplastics (MPs) has attracted much attention as to how microplastics can act as carriers of these pollutants. Polyurethane (PU) is one of the MPs found in aquatic environments, containing different functional groups it can interact with polar and nonpolar molecules. PAH derivatives (dPAHs) present different properties and thus can be adsorbed by different interactions; thus, this study investigated the adsorption of fluorene (FLN), dibenzothiophene (DBT), dibenzofuran (DBF), and carbazole (CBZ) onto PU MP. The Langmuir, Freundlich, and BET isotherm models were examined, and the BET model best fitted. The adsorption was a nonspontaneous process, exothermic for mono- and multilayer formation for FLN, DBT, and CBZ, and endothermic for DBF monolayer formation. The adsorption monolayer was formed by van der Waals forces, H─bonding, and π─π interactions, while the formation of the multilayer can be explained by π─π and hydrophobic interactions. The pseudo-second-order model proved to be more consistent for the adsorption of dPAHs. The adsorption in artificial seawater shows no significant differences for the monolayer but favored the adsorption multilayer due to the salting-out effect. Due to the existence of several adsorption mechanisms, PU MP interacts with dPAHs in greater quantities when compared to a MP with a simpler structure.

Novel Design of Eco-Friendly High-Performance Thermoplastic Elastomer Based on Polyurethane and Ground Tire Rubber toward Upcycling of Waste Tires.

Waste rubber tires are an area of global concern in relation to reducing the consumption of petrochemical products and environmental pollution. Herein, eco-friendly high-performance thermoplastic polyurethane (PU) elastomers were successfully in-situ synthesized through the incorporation of ground tire rubber (GTR). The excellent wet-skid resistance of PU/GTR elastomer was achieved by using mixed polycaprolactone polyols with Mn = 1000 g/mol (PCL-1K) and PCL-2K as soft segments. More importantly, an efficient solution to balance the contradiction between dynamic heat build-up and wet-skid resistance in PU/GTR elastomers was that low heat build-up was realized through the limited friction between PU molecular chains, which was achieved with the help of the network structure formed from GTR particles uniformly distributed in the PU matrix. Impressively, the tanδ at 60 °C and the DIN abrasion volume (Δrel) of the optimal PU/GTR elastomer with 59.5% of PCL-1K and 5.0% of GTR were 0.03 and 38.5 mm3, respectively, which are significantly lower than the 0.12 and 158.32 mm3 for pure PU elastomer, indicating that the PU/GTR elastomer possesses extremely low rolling resistance and excellent wear resistance. Meanwhile, the tanδ at 0 °C of the above-mentioned PU/GTR elastomer was 0.92, which is higher than the 0.80 of pure PU elastomer, evidencing the high wet-skid resistance. To some extent, the as-prepared PU/GTR elastomer has effectively solved the "magic triangle" problem in the tire industry. Moreover, this novel research will be expected to make contributions in the upcycling of waste tires.

Study on Grouting Performance Optimization of Polymer Composite Materials Applied to Water Plugging and Reinforcement in Mines.

With the increasing drilling depth of mines, the cross-complexity of fissures in the rock body, and the frequent occurrence of sudden water surges, polymer slurry, with its advantages of good permeability and strong water plugging, is increasingly used in mine grouting projects. Additional research is needed in order to further improve the grouting performance of polymer slurry, ensure the safety of mining operations, and reduce the grouting cost. In this paper, a polymer composite grouting material was prepared with diphenyl methyl diisocyanate, polyether polyol, and fly ash, as the main raw materials, with coupling agent and catalyst as auxiliary reagents. The performance of the composite grouting material in terms of mechanical properties, thermal stability, hydrophobicity, and bonding was explored. This study's findings indicated that incorporating fly ash led to notable enhancements in the thermal stability and water resistance of the polymer slurry. Furthermore, the introduction of fly ash notably raised the starting degradation temperature of the polymer, boosted the water contact angle of the composite material, and reduced the density and reaction temperature of the composite material. In addition, the catalyst and coupling agent as auxiliary reagents affected the polymers in terms of mechanical properties; in this paper, dibutyltin dilaurate was used as the catalyst, and organosilanes were used as the coupling agent. The catalyst successfully sped up the polymer's gel time, however, an excessive quantity of catalyst compromised the polymer's mechanical characteristics. The addition of organosilanes has a positive effect on the dynamic mechanical properties of the composites, fracture toughness, compression, bending, and bond strength. The research can offer a theoretical direction for creating polymer mixtures in mine grouting projects.

Eco-Friendly Waterborne Polyurethane Coating Modified with Ethylenediamine-Functionalized Graphene Oxide for Enhanced Anticorrosion Performance.

This study explores the potential of graphene oxide (GO) as an additive in waterborne polyurethane (WPU) resins to create eco-friendly coatings with enhanced anticorrosive properties. Traditionally, WPU's hydrophilic nature has limited its use in corrosion-resistant coatings. We investigate the impact of incorporating various GO concentrations (0.01, 0.1, and 1.3 wt%) and functionalizing GO with ethylenediamine (EDA) on the development of anticorrosive coatings for carbon steel. It was observed, by potentiodynamic polarization analysis in a 3.5% NaCl solution, that the low GO content in the WPU matrix significantly improved anticorrosion properties, with the 0.01 wt% GO-EDA formulation showing exceptional performance, high Ecorr (-117.82 mV), low icorr (3.70 × 10-9 A cm-2), and an inhibition corrosion efficiency (η) of 99.60%. Raman imaging mappings revealed that excessive GO content led to agglomeration, creating pathways for corrosive species. In UV/condensation tests, the 0.01 wt% GO-EDA coating exhibited the most promising results, with minimal corrosion products compared to pristine WPU. The large lateral dimensions of GO sheets and the cross-linking facilitated by EDA enhanced the interfacial properties and dispersion within the WPU matrix, resulting in superior barrier properties and anticorrosion performance. This advancement underscores the potential of GO-based coatings for environmentally friendly corrosion protection.

A Biodegradable Shape Memory Polyurethane Film as a Postoperative Anti-adhesion Barrier for Minimally Invasive Surgery.

Postoperative adhesions commonly form in various tissues, resulting in serious implications and an increased risk of secondary surgery. The application of anti-adhesion films as physical barriers has proven effective in reducing adhesion incidence and severity. However, existing anti-adhesion films require manual deployment during minimally invasive surgery, posing inconvenience and possibility of further injury. To address these limitations, we have developed an intelligent anti-adhesion film based on shape memory polyurethane. In this work, a linear shape memory polyurethane (ISO2-PU), incorporating hexamethylene isocyanate and isosorbitol as hard segments and poly(D, L-lactic acid) macrodiol as soft segments, was fabricated into an anti-adhesion film. The favorable shape memory effect of the ISO2-PU film ensures its convenient delivery and automatic unfolding, as revealed by a simulation experiment for endoscopic surgical implantation. Furthermore, the glass transition temperature (Tg) close to body temperature endows the ISO2-PU film with good mechanical compliance, thus ensuring a reliable fit with the wounded tissue to avoid undesired folding. Finally, in vivo experiments using a rat cecal abdominal wall injury model demonstrated that the combination of reliable fit, appropriate degradation rate, and good cytocompatibility promises the ISO2-PU film with high anti-adhesion efficacy. This work validates the concept of shape memory anti-adhesion barrier and expands future directions for advanced anti-adhesion biomaterials. STATEMENT OF SIGNIFICANCE: Postoperative adhesions are a common complication that occurs widely after various surgeries. This work developed an intelligent anti-adhesion film based on a linear shape memory polyurethane (ISO2-PU). This film is featured with remarkable shape memory effect and mechanical compliance at body temperature, appropriate degradability, and good cytocompatibility. These merits ensure convenient delivery and smart unfolding of ISO2-PU film during minimally invasive surgery and favorable postoperative anti-adhesion efficacy. The results validate the concept of shape memory anti-adhesion barrier and paves a way for designing next-generation anti-adhesion biomaterials.

Cross-linking manipulation of waterborne biodegradable polyurethane for constructing mechanically adaptable tissue engineering scaffolds.

Mechanical adaptation of tissue engineering scaffolds is critically important since natural tissue regeneration is highly regulated by mechanical signals. Herein, we report a facile and convenient strategy to tune the modulus of waterborne biodegradable polyurethanes (WBPU) via cross-linking manipulation of phase separation and water infiltration for constructing mechanically adaptable tissue engineering scaffolds. Amorphous aliphatic polycarbonate and trifunctional trimethylolpropane were introduced to polycaprolactone-based WBPUs to interrupt interchain hydrogen bonds in the polymer segments and suppress microphase separation, inhibiting the crystallization process and enhancing covalent cross-linking. Intriguingly, as the crosslinking density of WBPU increases and the extent of microphase separation decreases, the material exhibits a surprisingly soft modulus and enhanced water infiltration. Based on this strategy, we constructed WBPU scaffolds with a tunable modulus to adapt various cells for tissue regeneration and regulate the immune response. As a representative application of brain tissue regeneration model in vivo, it was demonstrated that the mechanically adaptable WBPU scaffolds can guide the migration and differentiation of endogenous neural progenitor cells into mature neurons and neuronal neurites and regulate immunostimulation with low inflammation. Therefore, the proposed strategy of tuning the modulus of WBPU can inspire the development of novel mechanically adaptable biomaterials, which has very broad application value.

Waterborne polyurethane with curcumin moieties for rapid responsive warnings and emergency antimicrobial action: Application in crab freshness preservation.

The ideal smart food-packaging film exhibits responsive color warnings and antimicrobial properties when food metamorphism starts. However, in practical applications, these film responses are slow, usually taking several days, which is not conducive to effective antimicrobial effects. In this study, natural plant-derived curcumin was introduced into waterborne polyurethane (WPU) dispersions through two modes: free-state and end-capping. During the film-forming process, under the influence of surface tension, the capped-end curcumin migrated to the surface and further immobilized free curcumin through π-π interactions. Consequently, curcumin accumulated on the film surface, preventing flipping in moist or hydrophobic environments, in addition to acting as a color indicator for the rapid detection of crab spoilage, thus generating ammonia for a real-time response (of approximately 60 s). Simultaneously, the curcumin degraded, producing water-soluble antimicrobial curcumin-degradation products. This study significantly advances the practical application of curcumin in smart food packaging.

Nonconventional Fluorescent Non-Isocyanate Polyurethane Foams for Multipurpose Sensing Applications.

Fluorescent foams with interconnected pores are attractive for the detection and quantification of various products. However, many fluorescent probes are suffering from aggregation-caused fluorescence quenching in their solid/aggregated state, are costly, and/or not straightforward to incorporate in foams, limiting their utility for this application. Herein, non-isocyanate polyurethane foams, prepared by the simple water-induced self-blowing process, present a nonconventional fluorescence behaviour, i.e. they are intrinsically fluorescent with a multicolor emission without requiring ex-situ traditional fluorescent probes. These foams demonstrate utility for capturing-sensing gaseous formaldehyde (an emblematic indoor air pollutant), as well as for detecting and quantifying various metal ions (Fe2+, Cu2+, Fe3+, Hg2+). They are also able to selectively sense tetracycline antibiotic in a ratiometric way with a high sensitivity. By exploiting the unique multicolor photoluminescent foam properties, a smartphone-compatible device is used for the facile antibiotic quantification. This nonconventional fluorescence behaviour is discussed experimentally and theoretically, and is mainly based on clusteroluminescence originating from multiple hydrogen bonding and hetero-atomic sub-luminophores, thus from aggregation-induced emission luminogens that are naturally present in the foams. This work illustrates that easily accessible non-conventional fluorescent NIPU foams characterized by a modular emission wavelength have an enormous potential for multiple substrates detection and quantification.

Unlocking Auxetic Behavior in Recyclable Thermosetting Foams Enabled by Dynamic Disulfide Cross-linking Strategy.

Auxetic foams with a negative Poisson's ratio (NPR) have attracted considerable attention in material engineering due to their outstanding performance in seismic and energy absorption. Nevertheless, thermoplastic auxetic foams are compromised by weak non-covalent crosslinking that diminishes the mechanical strength and durability of foams. Conversely, thermosetting foams with chemical crosslinking, although mechanically robust, face challenges in elaborating auxetic structure and in achieving recyclability. Herein, an alternative approach is proposed to tackle this dilemma by incorporating dynamic disulfide bonds into the polymer network for preparing a thermosetting polyurethane foam with covalent adaptable network. By leveraging the unidirectional multi-effect compression technique, the topological network reorganization of foam is induced, transforming the initial circular open-cell structure into a re-entrant cell structure. This structural transformation endows the foam with stable NPR capability, achieving a minimum Poisson's ratio value of -0.4 within 30% compressive strain. Benefiting from its reinforced network structure, the foam also demonstrates high compressive strength (6.47 MPa) and tensile strength (1.67 MPa). Furthermore, it is recyclable and can be recompressed into thermosetting films. This work offers a straightforward approach to making auxetic thermosetting foams with good mechanical and recyclable properties, which is interesting for the development of high-performance auxetic materials.