Cross-linked Architecture Research Articles

Reaction of β-Ketoester and 1,3-Diol to Access Chemically Recyclable and Mechanically Robust Poly(vinyl alcohol) Thermosets through Incorporation of β-(1,3-dioxane)ester.

The development of mechanically robust, chemically stable, and yet recyclable polymers represents an essential undertaking in the context of advancing a circular economy for plastics. Here, we introduce a novel cleavable β-(1,3-dioxane)ester (DXE) linkage, synthesized through the catalyst-free reaction of β-ketoester and 1,3-diol, to cross-link poly(vinyl alcohol) (PVA) for the formation of high-performance thermosets with inherent chemical recyclability. PVA, modified with β-ketoester groups through the transesterification reaction with excess tert-butyl acetoacetate, undergoes cross-linking reactions with the unmodified 1,3-diols within PVA itself upon thermal treatment. The cross-linking architecture improves PVA's mechanical properties, with Young's modulus and toughness that can reach up to 656 MPa and 84 MJ cm-3, i.e. approximately 3- and 12-fold those of linear PVA, respectively. Thermal treatment of the cross-linked PVA polymers under acid conditions leads to deconstruction of the networks, enabling the excellent recovery (>90 %) of PVA. In the absence of either thermal or acidic treatment, the cross-linked PVA maintains its dimensional stability. We show that the recovery of PVA is also possible when the treatment is performed in the presence of other plastics commonly found in recycling mixtures. Furthermore, PVA-based composites comprising carbon fibers and activated charcoal cross-linked by the DXE linkages are also shown to be recyclable with recovery of the PVA and the fillers.

Superstrong and tough silk fibers cross-linked with functionalized graphene

Natural silkworm silks with an intriguing integration of good strength, modulus, toughness and biocompatibility, have been widely used in textile and medical industry. However, the strength of silkworm silks is inferior to that of spider dragline silks, which are the strongest natural silks but extremely low yield. Herein, we develop a feasible strategy to continuously produce superstrong and tough regenerated silk fibers (RSFs) through the reconstruction of hierarchical and cross-linked architectures. Amine functionalized graphene (NH2-G) has been introduced to improve the content of β-sheet and crystalline orientation, and glutaraldehyde (GA) has been used to bridge NH2-G and silk micro/nanofibrils (SNFs) to form a highly interconnected and closely packed network, resulting in the remarkably improvement of mechanical properties. The resultant fibers exhibit an excellent tensile strength of 1029.6 ± 144.8 MPa, a Young's modulus of 16.8 ± 1.5 GPa, and a toughness of 277.4 ± 17.0 MJ/m3, exceeding those of the natural silkworm silks, spider dragline silks and most other previously reported regenerated silk fibers. We believe that the high-performance silk-based fibers are promising applications in lightweight and advanced structural materials.

Construction of three-dimensional porous graphene with N,S co-doping in KOH-K2CO3 eutectic active molten salt system for supercapacitors

We prepared a three-dimensional porous graphene (3DPG) with N or/and S doping (N-3DPG, S-3DPG, NS-3DPG) in the KOH-K2CO3 eutectic active molten salt system. Graphene oxide, urea, and 3-mercaptopropionic acid are adopted as the 3DPG, nitrogen, and sulfur precursors, respectively. As a result, a continuous 3D network with dense cross-linked architecture is gained because the KOH-K2CO3 medium works as template to accelerate the conversion of GO to 3D architecture. A specific capacitance of 521 F/g is obtained for the NS-3DPG, which is much larger than that of 3DPG, N-3DPG, S-3DPG. A symmetric supercapacitor NS-3DPG||NS-3DPG delivers an energy density of 21.7 Wh/kg at a power density of 300 W/kg, and displays the capacitance retention ratio of 98.0 % after 10,000 cycles. An asymmetric supercapacitor 3DPG||NS-3DPG is assembled, which shows an energy density as high as 33.6 Wh/kg at a power density of 400 W/kg and little capacitance fading for 10,000 cycles. Outstanding supercapacitor performances of the 3DPG||NS-3DPG are attributed to its excellent 3D hierarchical porous structure and the synergistic effect of N,S co-doping.

Wound microenvironment-responsive dually cross-linked nanofibrillar peptide hydrogels for efficient hemostatic control and multi-faceted wound management

The wound microenvironment-responsive hydrogel, featuring a dually cross-linked architecture, offers distinct advantages in the realm of drug delivery due to its exceptional mechanical properties and responsiveness to stimuli. In this investigation, a versatile dually cross-linked hydrogel was synthesized. The initial framework was established through non-covalent interactions employing a self-assembling peptide indomethacin-Gly-Phe-Phe-Tyr-Gly-Arg-Gly-Asp (abbreviated as IDM-1), while the second framework underwent chemical cross-linking of chitosan (CS) mediated by genipin. This dually-network arrangement significantly bolstered the structure, proving effective for hemostatic control. In addition, hydrogels can be triggered for degradation by proteases highly expressed in the wound microenvironment, releasing drugs like indomethacin (IDM) and CS. This characteristic introduced efficient multi-faceted wound management in vitro and in vivo, such as anti-inflammatory and antibacterial activities, ultimately augmenting the wound healing process. Thus, the development of a dually cross-linked hydrogel that enables smart drug release triggered by specific wound microenvironment presents considerable potential within the realm of wound management.

Fatigue-resistant and thermal insulating polyimide nanofibrous aerogels with temperature-invariant flexibility and nanofiber–lamella crosslinking architecture

The PINAs with a novel nanofiber–lamella crosslinking architecture exhibited excellent thermal insulation, flexibility and elasticity over a wide temperature range (−196 to 300 °C).

Self-wrinkling coating for impact resistance and mechanical enhancement

Protective materials are essential for personal, electronic, and military defenses owing to their efficient impact-resistant and energy-absorbing properties. Inspired by the bottom-up fabrication process and energy dissipation mechanism of natural organisms with hierarchical structures, we demonstrated a self-wrinkled photo-curing coating as a new protective material for enhancing the anti-impact property of the substrates. Owing to the self-assembly of polydimethylsiloxane (PDMS) containing polymeric photoinitiator on the surface, the liquid coating formulation was photo-cured by one-step UV irradiation with simultaneous generation of self-wrinkled surface morphology and a gradient cross-linked architecture. The maximum impact resistance height (hmax) of the glass substrate coated with plain coating increased from 120 to 180 cm when coated with wrinkled gradient coating. Furthermore, the Young’s modulus, fracture stress, and toughness of the wrinkled gradient coating film improved from 39.6 MPa, 2.4 MPa, and 74.1 MJ/cm3 to 235.0 MPa (∼5× increase), 18.5 MPa (∼6.6× increase), and 845.0 MJ/cm3 (∼10.8× increase) compared to the pure coating film as reference. The theoretical simulation and experimental results proved that the surface self-wrinkled morphology and intrinsic hierarchical architecture contribute to the energy dissipation and impact resistance of the cured coating. The photo-curing process, a bottom-up strategy, is conducted in a non-contact mode compared with nano-printing and lithography, enabling bulk materials to be engineered.

An approach to MOFaxanes by threading ultralong polymers through metal–organic framework microcrystals

Mechanically interlocked architecture has inspired the fabrication of numerous molecular systems, such as rotaxanes, catenanes, molecular knots, and their polymeric analogues. However, to date, the studies in this field have only focused on the molecular-scale integrity and topology of its unique penetrating structure. Thus, the topological material design of such architectures has not been fully explored from the nano- to the macroscopic scale. Here, we propose a supramolecular interlocked system, MOFaxane, comprised of long chain molecules penetrating a microcrystal of metal–organic framework (MOF). In this study, we describe the synthesis of polypseudoMOFaxane that is one of the MOFaxane family. This has a polythreaded structure in which multiple polymer chains thread a single MOF microcrystal, forming a topological network in the bulk state. The topological crosslinking architecture is obtained by simply mixing polymers and MOFs, and displays characteristics distinct from those of conventional polyrotaxane materials, including suppression of unthreading reactions.

Sunlight Stimulated Photochemical Self-Healing Polymers Capable of Re-Bonding Damages up to a Centimeter Below the Surface Even Out of the Reach of the Illumination.

The development of photochemical self-healing polymers faces the the following bottlenecks: i) only the surface cracks can be restored and ii) materials' mechanical properties are lower. To break these bottlenecks, cross-linked poly(urethane-dithiocarbamate)s carrying photo-reversible dithiocarbamate bonds covalently linked to indole chromophores and benzyl groups are designed. The conjugated structure of the chromophore and benzyl enhances the addition reactivity of thiocarbonyl moiety and facilitates photo-cleavage of CS bond, so that transfer of the created radicals among dithiocarbamate linkages is promoted. Accordingly, reshuffling of the reversibly cross-linked networks via dynamic exchange between the activated dithiocarbamates is enabled in both surface layer and the interior upon exposure to the low-intensity ultraviolet (UV) light from the sun. It is found that the damages up to a centimeter below the surface can be effectively recovered in the sunshine, which greatly exceeds the maximum penetration distance of UV light (hundreds of microns). Besides, tensile strength and failure strain of the poly(urethane-dithiocarbamate) are superior to the reported photo-reversible polymers, achieving the record-high 33.8 MPa and 782.0% owing to the wide selectivity of soft/hard blocks, multiple interactions, and appropriate cross-linking architecture. The present work provides a novel paradigm of photo self-healing polymers capable of re-bonding cracks even out of the reach of the illumination.

Self-catalyzed Gelling Synthesis of Aerogels with Inorganic and Organic Nanocomponents for Thermal Insulation and CO2 Capture

Silica aerogels have already been recognized as potential candidates in the fields of thermal insulation, sorption, and separation, but the intrinsic brittleness and cumbersome preparation process limit their broad applications. In this work, a simple self-catalyzed gelling strategy was applied to prepare organic–inorganic in situ hybrid aerogels (OIHAs) derived from bis[3-(triethoxysilyl)propyl]amine (BTPA) and methyltrimethoxysilane (MTES). The Si–CH3 groups from MTES make it possible for OIHAs to be prepared through ambient drying and exhibit good hydrophobicity. Owing to the alkalinity of the amine groups from BTPA, self-catalyed hydrolyzation and condensation reactions occur between two silicon precursors to build a uniform pearl-chain nanoporous structure. The high specific surface area and amine groups existing on the nanoskeleton surface of the obtained OIHAs endow them with fascinating CO2 capture ability up to 5.89 mmol/g at 298 K and 100 kPa, which are significantly higher than the values of other aerogels reported under the similar conditions. Furthermore, ultralow thermal conductivity (as low as 20.1 mW/(m·K) at 25 °C), high strength (up to 2.38 MPa), and great elasticity (fully recoverable elastic strain of 14%) are achieved together for the OIHAs due to the organic–inorganic in situ cross-linked architecture. The as-prepared OIHAs with versatile properties have great application prospects in the fields of building thermal insulation and CO2 capture. The self-catalyzed gelling strategy provides an alternative routine for the simple preparation of silica-based aerogels.

A CNN-LSTM-based domain adaptation model for remaining useful life prediction

Remaining useful life (RUL) estimation is fundamental to prediction and health management technology. Traditional machine learning generally assumes that the training and testing sets are independent and identically distributed. As distribution differences exist in real scenarios, this assumption hinders the effectiveness of the traditional machine learning methods. Aiming at these problems, we propose a CNN-LSTM-based domain adaptation framework for RUL prediction in this work. A shared encoding network and domain adaptation mechanism is introduced to decrease the data distribution discrepancy between the source and target domains. A cross-linking architecture is also developed for feature fusion, which considers the features at different levels to guarantee that the generated fusion features contain sufficient information for prognosis. Extensive experiments are then conducted to verify the superiority of the proposed framework. The experimental results demonstrate that the proposed model has excellent performance, especially for equipment with more complex working conditions and data.

Improved stability of all-inorganic perovskite nanocrystals in hierarchical ZSM-5 zeolites for multimodal applications

All-inorganic perovskite quantum dots (PQDs) CsPbX3 (X = Cl and Br) are expected a new generation of promising luminescent materials with narrow-band emissions, color-tunability, and high photoluminescence quantum yields (PLQYs), but the instability towards humid environments and high temperatures restrict their practical applicability. In this work, a hierarchically structured zeolite (HSZ) of ZSM-5 (Si/Al = 50) featured micro-mesoporous cross-linked architecture was applied to encapsulate CsPbX3 PQDs through a simple thermal diffusion strategy. The luminescence performances of CsPbX3 PQDs hybridized ZSM-5 nanocomposites can be optimized in the hierarchical micro-mesoporous structures. Particularly, the CsPbBr3-HSZ ZSM-5 composite calcined at 700 °C exhibited highly water-stable luminescence performance with a full-width at half-maximum (FWHM) of 22 nm and a high photoluminescence quantum yield (PLQY, 62%), maintaining 92% of the initial emission intensity even after 100 days of immersion in water. The highly water-resistant and stable luminescent performance of the composite was attributed to the interconnected micro-mesoporous network of HSZ ZSM-5, in which micropores provide a shielding wall to isolate the CsPbBr3 PQDs from the external environment and mesopores help to promote the diffusivity of precursors towards the successful space-confinement of CsPbX3 (X = Cl and Br) PQDs. The temperature-dependent fluorescence intensity and spectral shift characteristics of CsPbBr3-HSZ ZSM-5 composite afford its capacity acting as dual-mode optical thermometers, and the water-stable latent fingerprint identification has been also demonstrated by applying the CsPbBr3-HSZ ZSM-5 nanocomposite.

Flexible and cross-linked carbon nanofibers based on coal liquefaction residue for high rate supercapacitors

Free-standing electrospun carbon nanofibers nonwovens (CNF) with an outstanding cross-linked architecture can be successfully achieved via a simple and practicable strategy by combining electrospinning, stabilization and carbonization. In this study, the hybrids of asphaltene extracted from coal residue liquefaction, polyacrylonitril and terephthalic acid are used as precursors. Due to the synergistic effect of efficient cross-linked structures and short charge transfer channels, flexible cross-linked asphaltene-based CNF (CLACF), as the binder-free supercapacitor electrode, exhibits a high capacity of 225 F g−1 at 0.2 A g−1 and an outstanding rate capability of 148 F g−1 at 100 A g−1. The developed symmetrical supercapacitor based on CLACF has a maximum energy density of 4.20 Wh kg−1 with a power density of 1.22 kW kg−1. It also has excellent cyclic stability with 97.3% capacitance retention after 10,000 cycles at 2 A g−1.

Co9S8 quasi-hexagonal nanoparticles coupled with WS2 nanoring anchored on 3D sulfur, nitrogen Co-doped carbon nanotubes@graphene oxide cross-linking architecture for high performance asymmetric supercapacitor

Designing advanced hybrid supercapacitors (SCs) electrode materials with 3D cross-linking hierarchical porous architecture has desirable structural advantages, which can facilitate ion transport and provide excellent reaction site. Herein, a unique nanostructure consisting of Co9S8 quasi-hexagonal nanoparticles coupled with WS2 nanoring anchored on 3D sulfur, nitrogen Co-doped carbon nanotubes@graphene oxide (Co9S8@WS2-NS-15mlGO@CNTs) was obtained using a facile solvothermal strategy. This cross-linking and hierarchical porous nanostructure can maximize the electrical conductivity of entirety, which provides a favorable transport and permeability for the ions and electrons of the electrolyte environment. Benefiting from the structural compositional advantages and full play of the synergetic coupling effect, the as-prepared Co9S8@WS2-NS-15mlGO@CNTs electrode material exhibits absolutely the topmost specific capacitance of 1820.8 F g−1 at a current density of 1 A g−1 and outstanding cycle stability with a capacitance retention of 90.2% after 10000 cycles at 30 A g−1. Moreover, an asymmetric supercapacitor (ASC) fabricated by Co9S8@WS2-NS-15mlGO@CNTs (positive electrode) and NS-15mlGO@CNTs (negative electrode) presents an ultra-high energy density of 95.3 Wh kg−1 at a power density of 600 W kg−1, and long cycle life with 86.7% specific capacity retention at a current density of 20 A g−1 after 10000 cycles. It is believed that the presented work may open a new perspective to fabricate future competitive high-performance energy storage devices.

Hierarchical bismuth composite for fast lithium storage: Carbon dots tuned interfacial interaction

• Carbon dots (CDs) are utilized as “structure-directing agent” to tailor Bi 2 Se 3 /CDs composites with highly interconnected 3D architecture. • CDs-induced Bi-O-C bond is proved to effectively regulate the interfacial electronic structure. • The lithium storage mechanism of Bi 2 Se 3 /CDs anode is revealed by in-situ XRD. • Bi 2 Se 3 /CDs anode delivers fast-charging capability and durable cycling life. CDs are utilized as crucial structure-directing agents to elaborately design 3D cross-linked rod-like structured Bi 2 Se 3 /CDs composites. Computational simulations combined with experiments demonstrate that such robust 3D framework and the existence of interface Bi-O-C bond can simultaneously enhance the intrinsic sluggish kinetics and structural stability, endowing Bi 2 Se 3 /CDs anode with fast-charging capability and durable cycling life. Advanced electrode materials for fast-charging lithium-ion batteries are of great significance to next-generation energy-storage systems. Herein, three-dimensional (3D) hierarchical rod-structured Bi 2 Se 3 /carbon dots (Bi 2 Se 3 /CDs) composite is elaborately designed for fast-kinetics lithium storage. It is proposed that CDs-induced self-assembly growth and site-selective ion-exchange transform nanosheets into cross-linked architecture. Such robust 3D framework provides efficient channels for electron/ion transport and sufficient inner space for volume variation as confirmed by theoretical prediction. Notably, the existence of interface Bi-O-C bond would effectively enhance its inherent bulk electronic conductivity and accelerate ionic transportation by narrowing the bandgap and reducing the Li + migration energy barriers. Consequently, intrinsic sluggish kinetics and structural stability are simultaneously improved, endowing Bi 2 Se 3 /CDs composite electrode fast charging/discharging capability of 165 mAh g −1 at 20 A g −1 (corresponding to charge in ≈27 s) and excellent long-term durability with the capacity of 502 mAh g −1 over 950 cycles at 1 A g −1 . Moreover, the intercalation-conversion-alloying type lithium storage mechanism of Bi 2 Se 3 /CDs is revealed by in-situ XRD. This work provides a train of thoughts for other CDs-tailored composites with tunable morphology and structure.

Using a three-dimensional hydroxyapatite/graphene aerogel as a high-performance anode in microbial fuel cells

Bioaffinity of anode materials is a key factor for the power output of microbial fuel cells (MFCs). Anode surfaces with excellent biocompatibility can facilitate bacterial adhesion, biofilm propagation, and extracellular electron transfer. In this study, three-dimensional (3D) hydroxyapatite/graphene aerogel (HA/GA) was synthesized using a facile three-step method: hydrothermal treatment, dialysis, and freeze-drying. The HA/GA anode presented the excellent biocompatibility of HA and high conductivity of graphene. Moreover, the unique edge-to-edge cross-linked architecture of the HA/GA offered a large surface area for bacterial adhesion. Shewanella putrefaciens can generate more flavins through the introduction of highly biocompatible HA nanocrystals on the graphene sheets, leading to a rapid extracellular electron transfer between the biofilm and anode. An MFC containing a HA/GA anode delivered a maximum power density of 2.38 W m− 2, which was 1.83 times the power density achieved using a GA anode. Furthermore, MFCs equipped with HA/GA anodes were successfully utilized to drive a series of electrical appliances. The HA/GA anode possessed excellent biocompatibility, large surface area, superior hydrophilicity, and high conductivity, which were conducive for enhancing the surface bioaffinity and accelerating the interfacial charge transfer, thereby improving the electricity generation performance of the MFCs. This study has proven that HA is beneficial for enhancing the interface bioaffinity and that it can be applicable to MFC for high-performance bioelectricity harvesting.

Modulating the Bioactivity of Mucin Hydrogels with Crosslinking Architecture

AbstractHydrogels made of crosslinked macromolecules used in regenerative medicine technologies can be designed to affect the fate of surrounding cells and tissues in defined ways. Their function typically depends on the type and number of bioactive moieties such as receptor ligands present in the hydrogel. However, the detail in how such moieties are presented to cells can also be instrumental. In this work, how the crosslinking architecture of a hydrogel can affect its bioactivity is explored. It is shown that bovine submaxillary mucins, a highly glycosylated and immune‐modulating protein, exhibit strikingly different bioactivities whether they are crosslinked through their glycans or their protein domains. Both the susceptibility to enzymatic degradation and macrophage response are affected, while rheological properties and barrier to diffusion are mostly unaffected. The results suggest that crosslinking architecture affects the accessibility of the substrate to proteases and the pattern of sialic acid residues exposed to the macrophages. Thus, modulating the accessibility of binding sites through the choice of the crosslinking strategy appears as a useful parameter to tune the bioactivity of hydrogel‐based systems.

Alkaline stable thermal responsive cross-linked anion exchange membrane for the recovery of NaOH by electrodialysis

We report synthesis of acrylonitrile-vinylimidazole copolymer (PVACN) as novel cross-linking agent, for the fabrication of highly conducting stable and thermal responsive cross-linked polysulfone based anion exchange membrane (AEM) for the recovery caustic soda from industrial waste by electrodialysis. Reported cross-linker (PVACN) showed synergised properties aliphatic carbon chain and grafted ionic groups, while structural features of cross-linked AEM impart conductive and stable nature. Cross-linked architecture of the AEM also formed tight and dense structure. Reported PSCr (cross-linked polysulfone) AEMs possessed imidazolium quaternized groups to avoid Hoffmann elimination reaction (E2), while relatively less number of OH− attacking sites also showed membrane stability under alkaline medium. Suitable optimized PSCr/3 AEM exhibited 1.21 meq g−1 ion-exchange capacity (IEC), 5.5 × 10−2 S/cm ionic conductivity along with 21.7% swelling ratio, and assessed to be highly suitable for alkali recovery by electrodialysis. Electrodialytic recovery of NaOH was performed by increasing the concentrations about 5-times, while about 80% of treated water was also recovered as spin-off. Electro-dialyzer showed 1.33 kWh/kg energy consumption, 75.7% current efficiency at 35 °C, which were significantly improved with increase in feed temperature. Reported AEM provides sustainable and feasible alternative for applying ED for alkali separation/recovery from the industrial waste water.

Crosslinked polymer nanocapsules for therapeutic, diagnostic, and theranostic applications.

Crosslinked polymer nanocapsules (CPNCs) are hollowed nanoparticles with network-like polymeric shells stabilized by primary bonds. CPNCs have drawn broad and significant interests as nanocarriers for biomedical applications in recent years. As compared with conventional polymeric nanoparticles systems without cavity and/or crosslinking architectures, CPNCs possess significant biomedical relevant advantages, including (a) superior structural stability against environmental conditions, (b) high loading capacity and ability for region-specific loading of multiple cargos, (c) tuneable cargo release rate via crosslinking density, and (d) high specific surface area to facilitate surface adsorption, modification, and interactions. With appropriate base polymers and crosslinkages, CPNCs can be biocompatible and biodegradable. While CPNC-based biomedical nanoplatforms can possess relatively stable physicochemical properties owing to their crosslinked architectures, various biomedically relevant stimuli-responsivities can be incorporated with them through specific structural designs. CPNCs have been studied for the delivery of small molecule drugs, genes, proteins, and other therapeutic agents. They have also been investigated as diagnostic platforms for magnetic resonance imaging, ultrasound imaging, and optical imaging. Moreover, CPNCs have been utilized to carry both therapeutics and bioimaging agents for theranostic applications. This article reviews the therapeutic, diagnostic and theranostic applications of CPNCs, as well as the preparation of these CPNCs, reported in the past decade. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

A Hybrid Assembly of MXene with NH2−Si Nanoparticles Boosting Lithium Storage Performance

A facile hybrid assembly between Ti3 C2 Tx MXene nanosheets and (3-aminopropyl) triethoxylsilane-modified Si nanoparticles (NH2 -Si NPs) was developed to construct multilayer stacking of Ti3 C2 Tx nanosheets with NH2 -Si NPs assembling together (NH2 -Si/Ti3 C2 Tx ). NH2 -Si/Ti3 C2 Tx exhibits a significantly enhanced lithium storage performance compared to pristine Si, which is attributed to the robust crosslinking architecture and considerably improved electrical conductivity as well as shorter Li+ diffusion pathways. The optimized NH2 -Si/Ti3 C2 Tx anode with Ti3 C2 Tx : NH2 -Si mass ratio of 4 : 1 displays an enhanced capacity (864 mAh g-1 at 0.1 C) with robust capacity retention, which is significantly higher than those of NH2 -Si NPs and Ti3 C2 Tx anodes. Furthermore, this work demonstrates the important effect of the MXene-based electrode architecture on the electrochemical performance and can guide future work on designing high-performance Si/MXene hybrids for energy storage applications.

Molecular description of the coil-to-globule transition of Poly(N-isopropylacrylamide) in water/ethanol mixture at low alcohol concentration

Poly (N-isopropylacrylamide), PNIPAM, is a widely studied polymer, which serves as a key constituent of nanostructured soft materials with responsive properties. Upon increasing temperature the PNIPAM polymer chain undergoes a reversible coil-to-globule transition at T~305 K, which is reflected by a volume phase transition in cross-linked architectures, such as microgels, valuable for many practical applications. The addition of a cosolvent is a simple method to tune the transition temperature according to the specific purpose. In this study, we use atomistic molecular dynamics simulations to explore the solution behavior of a PNIPAM chain in a mixture of water and ethanol, acting as cosolvent, at low alcohol concentration. Our simulations reproduce the occurrence of the coil-to-globule transition of the polymer chain at 289 K, a temperature lower than that measured in water, in full agreement with experimental findings. By monitoring the temperature evolution of structural and dynamical properties of the PNIPAM-water-ethanol ternary system, we detect a localization of ethanol molecules at the polymer interface, mainly due to interactions between isopropyl and ethyl groups. We observe that the transition occurs without a release of adsorbed ethanol molecules, but with a loss of water molecules from the surrounding of PNIPAM hydrophobic moieties that favours the aggregation of ethanol molecules close to the polymer. Our results support the idea that both the decreased chemical potential of water in the bulk of the mixture and the competition between water and ethanol molecules in the interactions with the polymer play a driving role in the transition.