Reversible Polymer Research Articles

Effects of Cure on the Ionic Conductivity and Relaxation Strength of a Reversible Polymer Network Studied by Dielectric Spectroscopy

Effects of Cure on the Ionic Conductivity and Relaxation Strength of a Reversible Polymer Network Studied by Dielectric Spectroscopy

Unlocking the Impact of “Cell Position” on Solid‐State Hydrogen Storage: Investigations on an Activated Carbon Electrode Integrated in a Modified Reversible Polymer Electrolyte Membrane Fuel Cell

Unlocking the Impact of “Cell Position” on Solid‐State Hydrogen Storage: Investigations on an Activated Carbon Electrode Integrated in a Modified Reversible Polymer Electrolyte Membrane Fuel Cell

Towards Sustainable Materials: A Review of Acylhydrazone Chemistry for Reversible Polymers.

Transitioning towards a circular economy, extensive research has focused on dynamic covalent bonds (DCBs) to pave the way for more sustainable materials. These bonds enable debonding and rebonding on demand, as well as facilitating end-of-life recycling. Acylhydrazone/hydrazone chemistry offers a material with high stability under neutral and basic conditions making it a promising candidate for materials research, though the material is susceptible to acid degradation. However, this degradation under acidic conditions can be exploited, making it widely applicable in self-healing and biomedical fields, with potential for reprocessing and recycling. This review highlights studies exploring the reversibility of acylhydrazone/hydrazone bonds in various polymers, altering their properties, and utilizing them in applications such as self-healing, reprocessing, and recycling. The review also focuses on how the mechanical properties are affected by the presence of dynamic linkages, and methods to improve the mechanical performance.

Stretchable Piezoresistive Pressure Sensor Array with Sophisticated Sensitivity, Strain-Insensitivity, and Reproducibility.

This study delves into the development of a novel 10 by 10 sensor array featuring 100 pressure sensor pixels, achieving remarkable sensitivity up to 888.79kPa-1, through the innovative design of sensor structure. The critical challenge of strain sensitivity inherent is addressed in stretchable piezoresistive pressure sensors, a domain that has seen significant interest due to their potential for practical applications. This approach involves synthesizing and electrospinning polybutadiene-urethane (PBU), a reversible cross-linking polymer, subsequently coated with MXene nanosheets to create a conductive fabric. This fabrication technique strategically enhances sensor sensitivity by minimizing initial current values and incorporating semi-cylindrical electrodes with Ag nanowires (AgNWs) selectively coated for optimal conductivity. The application of a pre-strain method to electrode construction ensures strain immunity, preserving the sensor's electrical properties under expansion. The sensor array demonstrated remarkable sensitivity by consistently detecting even subtle airflow from an air gun in a wind sensing test, while a novel deep learning methodology significantly enhanced the long-term sensing accuracy of polymer-based stretchable mechanical sensors, marking a major advancement in sensor technology. This research presents a significant step forward in enhancing the reliability and performance of stretchable piezoresistive pressure sensors, offering a comprehensive solution to their current limitations.

Dynamically reversible cross-linked polymer electrolytes with highly ionic conductivity for dendrite-free lithium metal batteries

High-safety PEO-based electrolytes have attracted widespread attention, but their inefficient conduction of Li ions and poor contact with electrode interfaces deteriorate the performances of rechargeable lithium metal batteries. Herein, we design a vitrimer polymer electrolyte (V-SPE-PEG) with abundant dynamic imine bonds via Schiff base reaction between aldehyde and ammonia, which achieves high ionic conductivity and good interfacial compatibility with lithium anode. The dynamic polymer network in V-SPE-PEG exhibits solid-state plasticity because reversible imine bonding reactions enable the integrity of the polymer network to be maintained while altering the cross-linked points under external stimuli. Therefore, this 3D dynamic cross-linked network effectively facilitates the polymer chain dynamics and meanwhile enhances ionic conductivity. Additionally, dynamic bond exchange fosters electrolyte flowability and self-healing during lithium deposition, promoting a tightly integrated electrode/electrolyte interface while inhibiting lithium dendrites growth. Consequently, lithium symmetric cells utilizing the V-SPE-PEG electrolyte demonstrate exceptional long-term cycling stability, surpassing 1100 h and exhibit outstanding ionic conductivity of 2.7 × 10−4 S cm−1 at 30 °C. The LiFePO4||Li battery maintains stable cycling performance at both 40 °C and 60 °C. This study introduces an innovative approach to designing solid-state electrolytes for lithium-metal batteries.

Investigation of the rheological behaviour for improved extrusion-based additive manufacturing of polymer composites based on dissociative dynamic covalent bonds

More complex 3D structures were manufactured out of reversible covalent polymer networks using multi-material extrusion-based additive manufacturing. The rheological behaviour of reversible polymer networks based on the thermoreversible Diels-Alder reaction was optimized through the addition of different types of nanoclays and carbon black. The extrudability and deposition of the composites improved up to 5 wt% nanoclay, as the viscosity behaviour increased by an order of magnitude in the nozzle and by two orders of magnitude at the print bed temperature, without affecting the reversible gel transition temperature and the healing performance. An electrically conductive composite with 20 wt% carbon black and 1 wt% nanoclay could be printed using nozzle sizes down to 0.3 mm, resulting in higher resolution and accuracy than the pristine polymer networks. The percolating filler network enabled the printing of overhangs and hollow structures without the need for support material with perfect mechanical and electrical isotropy. Multi-material printing combining the electrically conductive and non-conductive composites enabled manufacturing self-healing deformation and force sensors that could recover their sensing performance upon damage healing at 90 °C for one hour.

Versatile room temperature phosphorescence polymer with luminophore content as low as 0.05 wt%

To impart processability and practical serviceability to organic room temperature phosphorescence (RTP) molecules, and address phase separation and rigid confinement environment of conventional RTP polymers, a small amount of Schiff base bonds crosslinked tetraphenylene luminescence networks are pinned to the borate ester bonds crosslinked epoxy networks producing reversible interlocked polymer networks-based halogen-free RTP material. By taking advantage of the conjugation interaction of Schiff base linkages, and phase separation inhibition/molecular confinement effects of the interlocking networks, excellent fluorescence quantum yield (up to 78.9 %), RTP lifetime (660 ms) and quantum yield (16.7 %) are achieved with ultra-low concentration of luminophores (0.05 wt%). Moreover, the resultant acquires decent tensile strength (3.8 MPa) and a high elongation-at-break (365 %) owing to its unique molecular design. The phosphorescence lifetimes (457 ∼ 602 ms) are only slightly affected even after cyclic stretching (at 50 % strain for 100 cycles), or soaking in water (for 30 days), or heating (90 °C). The built-in reversible covalent bonds and the topological network reorganization further enable injection molding and self-healing of the material. Having been repeatedly crushed/hot-pressed, the recycled material still shows RTP lifetime and quantum yield of 398 ms and 14.6 %, respectively. The present work provides a feasible approach to fabricate multifunctional robust organic phosphorescent materials with application prospects.

3D printed micro-structured hydrogel device with transmittance-changeable soft ‘armor’ camouflage for dual-encryption

Hydrogel-based physical dual-encryption typically relies on the reversible shape-deformation of polymer chains for the decryption. However, the stored information is confronted by indecipherability at the microscale because the intrinsic relaxation of polymer chains would disrupt the fidelity of encoded information. Inspired by female Doryteuthis opalescens squid’s camouflage strategy (i.e., switching a stripe on its mantle from nearly transparent to opaque white), we devised a reversible transmittance-changeable hydrogel layer to fully cover the mono-encrypted information layer for dual-encryption. The micro-structured hydrogel was manufactured via 3D printing to encode the information, which can be decoded by UV-induced fluorescent emission. Then, the white camouflage hydrogel was constructed to conceal the mono-encrypted layer, which will not affect the information encoding layer during the reversible polymer chain mobility. The information can be decoded with alkaline solution and UV irradiation in a rapid speed, i.e., in 4 min, with good reusability. Moreover, the information was accurately unveiled even at microscale resolution, holding great promise for high-level encryption at the device level.

Reversible color-changing polymer hydrogels mediated by urea-urease clock reaction for temporary information display

Inspired by the natural world's fascinating capacity for color change, researchers have developed various responsive hydrogels that shift colors. Among these, hydrogels that react to pH changes are particularly notable for their unique properties. The urea-urease autocatalytic reaction, a key pH clock reaction, is especially effective in temporarily adjusting these hydrogels' properties and enabling color changes in response to stimuli. In this study, we synergize the urea-urease clock reaction with the pH-sensitive color transformation of neutral red (NR), thereby establishing an NR-urea-urease clock reaction system. This system exhibits a dynamic color cycle from yellow to red and back to yellow. By incorporating this color transition mechanism into polymer hydrogels, we successfully initiate a pH change within the system. This innovation paves the way for a smart material capable of displaying temporary information through enzymatic reactions. The temporal variation in information display is finely tuned by adjusting the urea and urease concentrations. Such reversible color-changing hydrogels hold promising prospects for applications in secure information transmission and dynamic camouflage, marking a significant step forward in systems chemistry and materials science.

Thermochromic Polymer Nanocomposites for the Heat Detection System: Recent Progress on Properties, Applications, and Challenges.

Reversible thermochromic polymers have emerged as compelling candidates in recent years, captivating attention for their application in heat detection systems. This comprehensive review navigates through the multifaceted landscape, intricately exploring both the virtues and hurdles inherent in their integration within these systems. Their innate capacity to change colour in response to temperature fluctuations renders reversible thermochromic nanocomposites promising assets for heat detection technologies. However, despite their inherent potential, certain barriers hinder their widespread adoption. Factors such as a restricted colour spectrum, reliance on external triggers, and cost considerations have restrained their pervasive use. For instance, these polymer-based materials exhibit utility in the domain of building insulation, where their colour-changing ability serves as a beacon, flagging areas of heat loss or inadequate insulation, thus alerting building managers and homeowners to potential energy inefficiencies. Nevertheless, the limited range of discernible colours may impede precise temperature differentiation. Additionally, dependency on external stimuli, such as electricity or UV light, can complicate implementation and inflate costs. Realising the full potential of these polymer-based materials in heat detection systems necessitates addressing these challenges head-on. Continuous research endeavours aimed at augmenting colour diversity and diminishing reliance on external stimuli offer promising avenues to enhance their efficacy. Hence, this review aims to delve into the intricate nuances surrounding reversible thermochromic nanocomposites, highlighting their transformative potential in heat detection and sensing. By exploring their mechanisms, properties, and current applications, this manuscript endeavours to shed light on their significance, providing insights crucial for further research and potential applications.

Reversible polymer networks based on polylactide with tetraphenylethane thermally dissociating groups in crosslinks

AbstractPolylactide (PLA)‐based reversible/dynamic polymer networks were synthesized by coupling 4‐arm PLA stars containing reversible tetraphenylethane (TPE) groups in the core using diisocyanate. Star‐shaped PLAs with molecular weights of 3200 and 6400 g/mol were obtained by the original method involving UV coupling of linear PLAs containing benzophenone moieties in the chain middle. The efficient formation of networks with gel content close to 100% was confirmed by FTIR spectroscopy. Networks with different densities of reversible groups exhibited tensile strength in the range of 35–50 MPa. Their reversible character was demonstrated by stress relaxation measurements performed at different temperatures (120–150°C). The prepared networks were capable of very fast stress relaxation due to radical exchange reactions between TPE groups placed in crosslinks, in contrast to a reference network without TPE groups. It was shown in the repairing experiment that networks were capable of processing.

Construction of self-healing multifunctional hyper-crosslinked hyperbranched polymer @ metal–organic polyhedra (HHMOP) membranes

The preparation of hybrid membranes composed of polymer matrix and porous materials is a hot topic. Herein, a highly reversible hyper-crosslinked hyperbranched polymer @ metal–organic polyhedra (HHMOP) membrane was designed and synthesized using hyperbranched polyamide amine (HPMA), UiO-66-NH2, diethylenetriamine, and terephthalaldehyde through a multi-component Schiff-base condensation reaction of aldehyde and amine groups. The structures of HHMOP membranes were characterized by FTIR, XRD, and SEM. The mechanical properties, thermal properties, reversible self-healing properties, and biological activity of the membranes were studied. Introducing HPMA as hyper-crosslinking monomer and UiO-66-NH2 as porous comonomers into the network resulted in HHMOPs membranes with multiple functionalities: flexibility, humidity sensitivity, self-healing capacity, antibacterial capacity and better mechanical properties than the original polyimine films. The tensional intensity and breaking elongation of HHMOP membrane has been remarkably ameliorated, with the maximum tensile strength reached 54.64 MPa. The membranes showed humidity-sensitive mechanical properties and excellent self-healing performance, with 91.35 % strength revovered after 24-hours at room temperature and a relative humidity of 60 %, indicating that HPMA has a significant impact on the humidity responsiveness and self-healing performance of HHMOP membranes. The HHMOP membrane also demonstrated good antibacterial activity against common food lethal bacteria like the gram-positive Staphylococcus aureus and gram-negative Escherichia coli. This work will greatly enrich the devise and preparation of versatile membranes and broaden the use of MOFs.

Publisher Correction: Fast and reversible thermoresponsive polymer switching materials for safer batteries

Publisher Correction: Fast and reversible thermoresponsive polymer switching materials for safer batteries

Supramolecular Polymer Network based on Electrophilic Substitution (ES) Adduct of Furan-Triazolinedione.

Polymers with furan functionality have been the subject of extensive research on developing sustainable materials applying a limited number of dynamic covalent approaches. Herein, we introduce a facile, dynamic non-covalent approach to make a furan polymer readily accessible for self-healing applications based on its electrophilic substitution (ES) with a commercially available 1,2,4-triazoline-3,5-dione (TAD) derivative, 4-phenyl-TAD (PTAD). A tailor-made furan polymer, poly(furfuryl methacrylate) (PFMA), considering it an initial illustrative example, was rapidly ES modified with PTAD to produce furfuryl-tagged triazolidine that subsequently associated via inter-molecular hydrogen (H-) bonding to produce a thermally reversible supramolecular polymer network under ambient conditions. The H-bonded network was experimentally quantified via ATR-IR analysis and theoretically rationalized via the density functional theory (DFT) study using smaller organic model compounds analogous to the macromolecular system. Thermoreversible feature of the H-bonded triazolidine-derived supramolecular polymer network enabled the solution reprocessing and self-healing of the polymer material.

Bio-based conductive polyurethane composites derived from renewable castor oil with enhanced self-healing ability for flexible supercapacitors

To alleviate the pressure on the petrochemical industry and address environmental concerns, the utilization of polyurethane (PU) derived from castor oil (CO) (as an ester polyol replacement of petrochemical-based materials) has garnered significant attention in recent decades. Extending the service life of materials requires imparting self-healing properties to vegetable oil-based polymers, an aspect that has received limited attention in current studies. However, low self-healing efficiency still poses a significant challenge, and non-conductivity also remains an obstacle in current research, crucial for their application in electronic devices. In this work, we present the first series of electrically self-healing biopolymer composites constructed by incorporating carbon nanotube (CNT) networks into crosslinked castor oil-based polyurethane (BPU) through a simple curing process. These materials address the challenges mentioned above and exhibit improved mechanical, electrical, and self-healing capabilities compared to other bio-based self-healing materials. The resulting BPU/CNT composite demonstrated exceptional repeated self-healing capacity, restoring both mechanical properties and electrical performance even after experiencing severe mechanical damage. Notably, this composite served as a conductive substrate in flexible solid-state supercapacitor (FSSC) devices. Consequently, the FSSC derived from the composite conductive substrate achieved an impressive 92.4 % self-healing efficiency even after undergoing 7 cutting/healing cycles. The device remained virtually unchanged even after being bent at a 180° angle with a bending radius of 1.6 mm, indicating excellent repeatability and durability. The exceptional self-healing ability, with ∼98 % electrical recovery at 100 °C for 70 s and 93 % at 80 °C after 6 min, of these composites was attributed to the synergistic interactions of the dynamic exchange reactions of disulfide bonds and dense hydrogen bonds within the BPU matrix, which provide a reversible dynamic polymer network. The healing efficiency of these dynamic bonds was evaluated by adjusting the composition ratio of the long linear chain of pTHF in hybrid polyols of the crosslinked polymer network. Overall, this work highlights a series of green, simple, and highly efficient self-healing polymer composites derived from renewable castor oil, and it establishes an essential framework for future sustainable polymer composite design.

Fully Recyclable Cured Polymers for Sustainable 3D Printing.

The most prevalent materials used in the Additive Manufacturing era are polymers and plastics. Unfortunately, these materials are recognized for their negative environmental impact as they are primarily nonrecyclable, resulting in environmental pollution. In recent years, a new sustainable alternative to these materials has been emerging: Reversible Covalent Bond-Containing Polymers (RCBPs). These materials can be recycled, reprocessed, and reused multiple times without losing their properties. Nonetheless, they have two significant drawbacks when used in 3D printing. First, some require adding new materials every reprinting cycle, and second, others require high temperatures for (re)printing, limiting recyclability, and increasing energy consumption. This study, thus, introduces fully recyclable RCBPs as a sustainable approach for radiation-based printing technologies. This approach enables multiple (re)printing cycles at low temperatures (50°C lower than the lowest reported) without adding new materials. It involves purposefully synthesized polymers that undergo reversible photopolymerization, composed of a tin-based catalyst. An everyday microwave oven quickly depolymerized these polymers, obtaining complete reversibility.

The amount of improvement and therapeutic effect of sports health by increasing the viscosity of peach juice through reverse osmosis and polymer membrane

In this study, the performance of polyamide membranes embedded with synthesized silica nanoparticles was evaluated for pomegranate juice concentration using the reverse osmosis (RO) process. The research aims to explore the potential therapeutic benefits and measurable improvements in sports health achieved by employing RO and a polymer membrane to enhance the viscosity of peach juice. The membranes utilized in this study feature a multi-layer structure comprising a non-woven polyester layer for strength, a sulfone polyether polymer sheet, and a polyamide layer synthesized through the copolymerization of m-phenylenediamine and benzene tricarboxylic chloride. To enhance the membrane properties, silica nanoparticles were incorporated into the second layer. The experiment was designed using Design Expert software, considering three parameters: weight percentage of polyether sulfone at three levels (12%, 16%, and 20%), weight percentage of silica nanoparticles at three levels (0%, 0.1%, and 0.2%), and the process pressure at three levels (20, 25, and 30 bar). The optimal membrane configuration obtained from this experimental design consisted of a sulfone polyether polymer content of 16%, silica nanoparticles concentration of 2%, and a working pressure of 23.24 bar. Furthermore, the findings of this study suggest that the application of polymer materials and nanoparticles for membrane modification holds potential benefits for the juice industry in the future. However, it is essential to consider the wide range of factors that can influence the properties of nanocomposite membranes.

Cationic ring-opening copolymerization of a cyclic acetal and γ-butyrolactone: monomer sequence transformation and polymerization–depolymerization control by vacuuming or temperature changes

Polymerization–depolymerization equilibrium is a promising strategy for the construction of polymerization systems through which sustainable polymers can undergo reversible polymer–monomer transformations. In this study, we perform monomer sequence transformation and copolymer depolymerization, which are based on transacetalization reactions and polymerization–depolymerization equilibrium, in the cationic ring-opening copolymerization of 2-methyl-1,3-dioxepane and γ-butyrolactone with a protonic acid. The removal of monomer molecules from the copolymerization solution by vacuuming with a vacuum pump caused monomer sequence to transform into pseudo-alternating copolymer chains and subsequently depolymerize into oligomers. Increasing the temperature during copolymerization also resulted in depolymerization, while copolymers were regenerated by the subsequent decrease in temperature.

Photothermal‐Driven Crawlable Soft Robot with Bionic Earthworm‐Like Bristle Structure

Remote stimuli‐responsive movable soft robots without the need for complex 3D deformation processes and specific working environments is an unsolved problem and urgent need. In this work, under the inspiration of mother nature, a novel strategy of simple combination of the bionic bristles structure and the photothermal‐driven reversible shape change liquid crystal polymer (LCP) actuator is proposed to work out this difficulty. The combination structure is designed as unique three parts with two bionic bristle units at the two ends and one LCP unit in the center with a soft connection between them. After matching the driving force and the resistance, the prepared soft robot can realize the earthworm‐like unidirectionally crawl on the paper surface upon near‐infrared light irradiation through the contracting and stretching of LCP with a maximum average speed of 4.4 mm min−1. What's more, the crawling speed of the soft robot can be regulated by varying the irradiation distance of near‐infrared light or the length of the actuators. This strategy realizes the type of remote wireless control soft robot and has potential application ability in other soft robots with various demands.

Malignant Small Round Cell Tumor: A Rare Aggressive Malignancy-Case Report

Background: Malignant Small round Cell Tumor (MSRCT) is very rare group of tumors. Malignant cells have similar histologic appearance making it difficult to distinguish one from another, and poses a diagnostic challenge with needs for a multimodal approach. Immunohistochemistry and immunophenotyping by flow cytometry, reverse transcriptase polymer chain reaction (RT-PCR) and fluorescence in situ hybridization are needed to confirm. The appropriate and best treatment in early stages of MSRCT is early surgical excision with chemoradiotherapy based on patient specification. Inspite of all these, tumors have poor prognosis and chance of recurrence are high. Method: Case study of a 27-year-old male who presented with a non-productive cough for 4 weeks, with feverish feeling with weight loss and shortness of breath and a new onset precordial chest pain non radiating and worse on exertion. On examination his vitals were: BP 121/91 mm of hg, pulse rate 114bpm, temperature 36.3 degrees Celsius, respiratory rate 24/per min, SPO2 96%.On examination, Elevated Jugular Venous Pressure, hyperactive precordium, displaced apex beat to 6th intercostal space anterior axillary line, muffled heart sounds and bilateral lower limb edema. Respiratory exam was unremarkable. Sputum gene expert was negative for mycobacterium tuberculosis and covid 19 rapid test was negative. Chest X Ray showed cardiomegaly and a transthoracic echocardiography revealed moderate-large pericardial effusion, with mild collapse of right atrium in diastole. Pericardiocentesis done showed hemorrhagic effusion with lymphocytes cell component, patient was initiated on treatment for TB pericarditis empirically. Three months later a chest CT scan done revealed extensive mediastinal/pericardial mass with lung nodules. An ultrasound guided mediastinal/Pericardial biopsy was done, revealed a poorly differentiated small round cell carcinoma. Results: Patient expired 14 weeks from the initial onset of symptoms while awaiting immunohistochemistry studies for specific diagnosis of the tumor and oncology review. Discussion: This demonstrates the complexity of establishing differential diagnosis of MSRCT in a resource limited setting with subsequent delay in treatment initiation, heralds poor prognosis. This also confirms difficulties in establishing differential diagnosis in poorly differentiated tumor.