Flexible Crosslinking Research Articles

Optically clear pressure‐sensitive adhesive with flexible crosslinking agent for high recovery efficiency, low energy storage modulus, and excellent folding resistance

AbstractOptically clear pressure‐sensitive adhesive (OCA) possesses exceptional optical properties and exhibits pressure‐sensitive adhesion, making it widely utilized in the adhesive layers of various electronic display devices. However, the increasing popularity of foldable mobile phones in recent years has imposed new requirements on the overall performance of OCA. Conventional pressure‐sensitive adhesives can enhance recoverability through cross‐linking but often demonstrate inadequate adhesive strength. In this study, three long‐chain crosslinking agents (CL) were synthesized using hydroxyethyl acrylate (HEA), dicyclohexylmethane diisocyanate (HMDI), polypropylene glycol (PPG), polyether amine (PEA), and hydroxyl‐terminated polybutadiene (R45V). The long‐chain CL agent contains numerous flexible segments that improve the recovery capability of the OCA while maintaining a certain level of adhesion. The optical clear pressure‐sensitive adhesive, crosslinked by three flexible crosslinkers, exhibits a low glass transition temperature (−60 to −40°C) and a low storage modulus (<0.1 MPa), along with an appropriate 180° stripping force (6–8 N/25 mm). Optically transparent pressure‐sensitive adhesives demonstrate excellent recovery properties (>85%), high light transmittance (>92%), and exceptional flexibility. Moreover, compared to market products, the optically transparent pressure‐sensitive adhesive shows superior folding resistance (>100,000 times). This indicates its suitability for applications in flexible optical displays such as foldable mobile phones and wearable electronics.

Effect of one- and two-dimensional nanomaterials on polysulfone-based anion exchange membranes for fuel cells

To investigate nanoparticle morphology's impact on the performance of composite anion exchange membrane (AEM), one-dimensional quaternized branched polyethyleneimine @multi-walled carbon nanotubes (QBPEI@MWCNTs) and two-dimensional quaternized branched polyethyleneimine @graphene oxide sheets (QBPEI@GO) were prepared and incorporated into quaternized polysulfone (QPSF) matrices to form QQ-x-MWCNTs and QQ-x-GO AEMs. These AEMs exhibited superior mechanical properties due to the flexible QBPEI cross-linking and nanoparticle reinforcement. Moreover, QBPEI facilitated microphase separation and ion cluster formation along the surface of nanoparticles, enhancing OH− transport. As a result, QQ-1.0%-MWCNTs and QQ-0.7%-GO AEMs both showed high ionic conductivity (83.19 mS/cm and 76.14 mS/cm at 80 °C). QQ-x-MWCNTs AEMs displayed higher conductivity than QQ-x-GO AEMs over the entire temperature range (20–80 °C) at the same level of ion exchange capacity. QQ-0.7%-MWCNTs AEM excelled, achieving a peak power density of 102.44 mW/cm2 in an H2/O2 fuel cell (80 °C, 40 % RH), surpassing QQ-0.5%-GO AEM (86.50 mW/cm2). Evidently, one-dimensional MWCNTs are effective for establishing long-range interconnected ion transport channels, making them excellent AEM fillers.

High selectivity molecularly imprinted polymer based on short amylose as bio-based functional monomers for selective extraction of λ-cyhalothrin

Nowadays, the development of sustainable molecularly imprinted polymers (MIPs) with high selectivity is still challenging due to the limitations of bio-based functional monomers. In this study, the highly selective and porous MIPs (LC-TMIPs) were designed and prepared on short amylose (SAM) as bio-based functional monomers, λ-cyhalothrin (LC) as a template molecule, and tetrafluoroterephthalonitrile as a rigid crosslinking agent. Static, dynamic, and selective adsorption experiments were conducted to investigate the adsorption performance. The results indicated that, compared to MIPs prepared using epichlorohydrin as flexible crosslinking agents, LC-TMIPs exhibited higher imprinting factor (3.93), selectivity (5.78), and adsorption capacity (35.79 mg g−1), as well as faster adsorption/desorption kinetics. The LC-TMIPs were used as sorbents for the selective determination of LC in both apple and cucumber samples by high-performance liquid chromatography. Under the optimal extraction conditions, the recoveries of the method reached 92.1–106.1 %, with a linear range of 1.5–30 ng g−1 and a detection limit of 0.5 ng g−1. The proposed preparation method of LC-TMIPs is expected to open a new way to prepare highly selective and sustainable MIPs for hydrophobic compounds.

Strengthening-Durable Trade-Off and Self-Healing, Recyclable Shape Memory Polyurethanes Enabled by Dynamic Boron-Urethane Bonds.

Addressing the demand for integrating strength and durability reinforcement in shape memory polyurethane (SMPU) for diverse applications remains a significant challenge. Here a series of SMPUs with ultra-high strength, self-healing and recyclability, and excellent shape memory properties through introducing dynamic boron-urethane bonds are synthesized. The introducing of boric acid (BA) to polyurethane leading to the formation of dynamic covalent bonds (DCB) boron-urethane, that confer a robust cross-linking structure on the SMPUs led to the formation of ordered stable hydrogen-bonding network within the SMPUs. The flexible crosslinking with DCB represents a novel strategy for balancing the trade-off between strength and durability, with their strengths reaching up to 82.2MPa while also addressing the issue of durability in prolonged usage through the provision of self-healing and recyclability. The self-healing and recyclability of SMPU are demonstrated through rapid dynamic exchange reaction of boron-urethane bonds, systematically investigated by dynamic mechanical analysis (DMA). This study sheds light on the essential role of such PU with self-healing and recyclability, contributing to the extension of the PU's service life. The findings of this work provide a general strategy for overcoming traditional trade-offs in preparing SMPUs with both high strength and good durability.

Highly flexible carbon nitride-polyethylene glycol-cellulose acetate film with photocatalytic antibacterial activity for fruit preservation

Cellulose acetate film, as a biodegradable and biomass-derived material, has great potential applications in food packaging. However, the poor mechanical and antibacterial properties limit its applications. Herein, a highly flexible carbon nitride-polyethylene glycol-cellulose acetate (CN-PEG-CA) film was successfully prepared by combining graphitic carbon nitride (g-C3N4) photocatalyst with cellulose acetate (CA). The g-C3N4 enables the film with antibacterial activity, as a green photocatalyst. PEG softens the rigid polymer CA and crosslinks CA, PEG, and g-C3N4 together by hydrogen bonding, as a flexible crosslinker. X-ray diffractometer (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectrum (FT-IR) characterizations confirmed the successful preparation of the CN-PEG-CA film. The mechanical property tests demonstrated that adding PEG increased the elongation at break of the film by about 4 times. The composite film had high antibacterial activity, and the bactericidal rates on Escherichia coli and Staphylococcus aureus were 99.98 % and 99.89 %, respectively. It effectively extended the shelf life of strawberries to 96 h and effectively maintained the quality of strawberries during storage. After 96 h, the weight loss rate of strawberries packaged with 15 % CN-PEG-CA film was 21.83 %, vitamin C content was 45.47 %, titratable acidity content was 0.89 %, and color, hardness and total soluble solids were well maintained. And biocompatibility test results showed that the film was safe and nontoxic. From the ecological and economic point of view, the highly flexible and biodegradable films with efficient photocatalytic antibacterial activity synthesized in this paper have great potential in the field of food packaging.

Ultra-stretchable and highly tough ionogels with underwater repeatable adhesion and anti-swelling capacity for real-time motion detection, signal transmission and electrochemical monitoring platforms

Hydrophobic ionogels have received growing interest as a flexible underwater sensing material. However, it remains a significant challenge to improve the tensile properties, prolonged underwater repeatable adhesion, and multifunctionality of the hydrophobic ionogel due to the restricted selection of monomers and curing strategies. Herein, a hydrophobic multifunctional fluorine-rich ionogel with ultra-stretchability and superior long-term underwater repeatable adhesion is designed by virtue of the introduction of a rigid and flexible macromolecular cross-linker and a structure of rigid cationic imidazole-benzene rings in a hydrophobic ionic liquid monomer. The macromolecular cross-linker significantly improves the mechanical properties of the ionogel because of the reduction in stress concentration. And the structure of short imidazole-benzene rings with high rigidity exposes a larger amount of adhesion groups on the surface of the ionogels compared to the flexible groups, leading to enhanced long-term underwater repeatable adhesion performance of the ionogel. The ionogels are applied to real-time monitoring of exposure to water, underwater swimming motion monitoring, underwater Morse code transmission and electrochemical monitoring platforms. And this work is expected to provide ideas for the multifunctionalization of underwater sensing technology and the integration of functional units in underwater flexible electronic skin.

Enhanced molecular recognition with longer chain crosslinkers in molecularly imprinted polymers for an efficient separation of TR active substances.

Molecular imprinting technology has been widely studied as a technique to obtain molecular recognition by artificial means. Selecting functional monomers or polymerization conditions plays a key role to optimize molecularly imprinted polymer (MIP) synthesis. To date, there have been few reports well exploiting the effect of crosslinkers. Here, in this study, we synthesized the MIPs using poly(ethyleneglycol) dimethacrylate with different units of ethylene oxide (n = 1 to 23) as crosslinkers to observe the molecular recognition abilities. The MIPs were attached to the surface of mono-dispersed polymer beads. The obtained spherical MIPs and non-imprinted polymers were filled in a column for high performance liquid chromatography. Then the retention selectivity toward TR active substances was evaluated. The result revealed that the recognition ability did not improve regardless of the amount of ethylene oxide. With the crosslinker (n = 9), extremely high retention selectivity was observed, which provides at most around ten times as large imprinting factors in comparison with other MIPs. Interestingly, we obtained the highest recognition ability at around polymerization temperature from the evaluation of the recognition ability toward temperature shift using the MIP (n = 9). In general, hydrogen bonding based on MIPs provides high recognition ability at low temperature, whereas, this study indicates that the use of flexible crosslinkers may enable the synthesis of MIPs that precisely memorize the conditions of polymerization. Lastly, we simultaneously analyzed the TR active substances using the column filled with MIPs (n = 9). The result showed relatively linear correlation between the retention strength of each substance and phycological activity toward TR obtained by yeast assay. Therefore, we can conclude that an induced fit like the receptor emerged by constructing the flexible molecular recognition field.

Rigid crosslink improves the surface area and porosity of β-cyclodextrin beads for enhanced adsorption of flavonoids

Many reported β-cyclodextrin (β-CD) polymers have poor flavonoid adsorption performance due to their low surface area and porosity resulting from the compact stack of the β-CD molecules crosslinked by flexible crosslinkers. Here, we propose a rigid crosslink strategy that uses phytic acid (PA) having rigid cyclic group as crosslinkers, achieving a high-surface-area (61.42–140.23 m2/g) and porous β-CD beads. The improved surface area and porosity are attributed to the rigid cyclic groups in PA, which expand the network structure of β-CD polymers. Benefitting from the advantages, the optimized PA-crosslinked β-CD (PA-β-CD) beads have an over tenfold increased adsorption amount and an threefold increased diffusivity for rutin compared with traditional non-porous β-CD beads crosslinked by epichlorohydrin. Moreover, dynamic adsorption experiments reveal that PA-β-CD beads are able to treat about 1100 mL of rutin solution (0.05 mg/mL), over 5 times higher than that of the non-porous β-CD beads (200 mL). These results demonstrate the promise of PA-β-CD beads for rapid and high-capacity adsorption of rutin.

A double-crosslinked cyclodextrin-based porous polymer for effective removal of bisphenol A: Preparation, adsorption behavior and mechanism

As a sort of typical endocrine-disrupting chemical, bisphenol A (BPA) brings potential harm to the aquatic ecosystem and human health. Cyclodextrin-based polymer adsorbents have attracted increasing attention due to their high affinity for BPA. In this study, we demonstrated a double cross-linking adsorbent BDE-T-CDP(B) prepared at an optimal ratio, which was green synthesized by simultaneous ring-opening and nucleophilic substitution reaction of beta-cyclodextrin (β-CD), a rigid crosslinker (tetrafluoroterephthalonitrile, TFTPN) and a flexible crosslinker (1,4-butanediol diglycidyl ether, BDE) in the alkaline aqueous system, avoiding the involvement of organic solvents. The combined effects of cavity inclusion, π-π interaction, and hydrogen bonding endowed BDE-T-CDP(B) to exhibit superior adsorption capacity (71.30 mg⋅g−1) toward grabbing BPA, which was visualized by IGM analysis. BDE-T-CDP(B) with porous structures was found to rapidly achieve adsorption equilibrium governed by the pseudo-second-order kinetic model (R2 > 0.99) within 30 min. Besides, BDE-T-CDP(B) could still reach 94.7% of the saturated adsorption capacity after five successive regeneration cycles. Further, during the treatment of practical plastic factory wastewater with trace BPA pollutants, the satisfactory adsorption performance of BDE-T-CDP(B) was evidently observed. Thus, BDE-T-CDP(B) is a promising engineering adsorbent owing to its green preparation, excellent adsorption performance, and good recyclability.

Extrudable, robust and recyclable bio-based epoxy vitrimer via tailoring the topology of a dual dynamic-covalent-bond network

Vitrimers offer possibilities for sustainable materials due to their reprocessability and recyclability. However, enhancing both their mechanical strength and network dynamics simultaneously remains a challenge. Previous attempts to address this issue have not achieved the desired mechanical strength comparable to traditional cured resins and have also fallen short in dynamic performance during compression molding and extrusion processing. In our study, we have successfully created an epoxy vitrimer, EOCY, by a rational design of the topology of a dual dynamic-covalent-bond (D-DCBs) network based on disulfide and imine bonds. The network of this design incorporates a high density of DCBs through the combined utilization of a rigid monomer containing imine bonds and a flexible crosslinker that carries disulfide bonds. The rigid epoxy monomers in EOCY result in superior tensile strength (85.35 MPa), high Tg (112.01 °C), high Young's modulus (2.01 GPa) and improved solvent resistance. Moreover, the flexibility of the curing agent and plentiful D-DCBs lead to reduced activation energy (Ea = 42.23 kJ/mol) and short relaxation time (τ = 4.84 s at 140 °C), enabling EOCY to withstand multiple cycles of compression molding and continuous extrusion processing. Our vitrimer also demonstrates recyclability through various chemical methods, leveraging the unique properties of disulfide and imine bonds. In summary, this study presents a rational approach to network structure design for vitrimers with exceptional mechanical and dynamic properties.

High stretching tuned GO decorated non-shrinkable polyacrylic acid-based composite fiber and its excellent performance as a Fenton catalyst

Mixed valent iron ions were used to create a flexible ionic crosslinking network through coordination, making PAA fiber highly stretchable, and the fiber was highly stretched to tear graphene oxide (GO) sheets into discontinuously-dispersed monolayer sheets. The monolayer sheets could construct many hydrogen bonds with PAA chains to serve as knots to hinder chain movement, controlling the shrinkage of stretched fiber. Co-solvent formamide could improve the heat resistance of PAA fiber through special calorific effect; thus the highly-stretched fiber could tolerate high temperature heat setting. Due to the advanced structure induced by stretching, internal force relaxation caused by heat setting, and the existence of knots, the resulting fiber possessed the features of high strength and no shrinkage. High strength made the fiber mechanically applicable, and the unshrinkability could help it to maintain large specific surface area and strong iron ions-immobilizing capability. As a result, the catalytic activity of non-shrinkable fiber was increased by 25% compared with that of shrinkable fiber for methylene blue (MB) decolorization, and iron ion loading ratio was increased by 174.5%; however, iron ion leaching ratio was decreased by 76.5%, which was conducive to reusability improvement. Thereby, the resulting fiber could be repeatedly used to decolorize MB.

Innovation in Cross-Linking Mass Spectrometry Workflows: Toward a Comprehensive, Flexible, and Customizable Data Analysis Platform.

Cross-linking mass spectrometry (XL-MS) is widely used in the analysis of protein structure and protein-protein interactions (PPIs). Throughout the entire workflow, the utilization of cross-linkers and the interpretation of cross-linking data are the core steps. In recent years, the development of cross-linkers and analytical software mostly follow up on the classical models of non-cleavable cross-linkers such as BS3/DSS and MS-cleavable cross-linkers such as DSSO. Although such a paradigm promotes the maturity and robustness of the XL-MS field, it confines the innovation and flexibility of new cross-linkers and analytical software. This critical insight will discuss the classification, advantages, and disadvantages of existing data analysis search engines. Take the new platinum-based metal cross-linker as an example, potential pitfalls in characterization of cross-linked peptides using existing software are discussed. Finally, ideas on developing more flexible, comprehensive, and user-friendly cross-linkers and software tools are proposed.

A Uniform Self-Reinforced Organic/Inorganic Hybrid SEI Chelation Strategy on Microscale Silicon Surfaces for Stable-Cycling Anodes in Lithium-Ion Batteries.

A promising anode material for Li-ion batteries, silicon (Si) suffers from volume expansion-induced pulverization and solid electrolyte interface (SEI) instability. Microscale Si with high tap density and high initial Coulombic efficiency (ICE) has become a more anticipated choice, but it will exacerbate the above issues. In this work, the polymer polyhedral oligomeric silsesquioxane-lithium bis (allylmalonato) borate (PSLB) is constructed by in situ chelation on microscale Si surfaces via click chemistry. This polymerized nanolayer has an "organic/inorganic hybrid flexible cross-linking" structure that can accommodate the volume change of Si. Under the stable framework formed by PSLB, a large number of oxide anions on the chain segment preferentially adsorb LiPF6 and further induce the integration of inorganic-rich, dense SEI, which improves the mechanical stability of SEI and provides accelerated kinetics for Li+ transfer. Therefore, the Si4@PSLB anode exhibits significantly enhanced long-cycle performance. After 300 cycles at 1 A g-1 , it can still provide a specific capacity of 1083 mAh g-1 . Cathode-coupled with LiNi0.9 Co0.05 Mn0.05 O2 (NCM90) in the full cell retains 80.8% of its capacity after 150 cycles at 0.5 C.

Preparation and characterisation of liquid crystal elastomer films with selective reflectivity

ABSTRACT In this paper, the liquid crystal elastomer films (A’BG series) have been prepared by grafting polymerisation, using the 4-allyloxybenzoic acid cholesteryl ester (MB) as liquid crystal monomer, dodecane-1,12-diyl bis(undec-10-enoate) (MG) as flexible cross-linker and polymethyl hydrosiloxane (containing 35 Si-H) as the main chain. The A’BG series films are cholesteric liquid crystal elastomer films (LCEs) with a liquid crystal region above 100°C. With the crosslinker content decreasing, A’BG-2 and A’BG-3 display selective reflection in UV region and visible region, respectively. The selective reflection wavelength of A’BG-3 occurs blue shift with the temperature increasing. The glass transition temperatures (Tg) of the A’BG series films are 16.4–40.8°C and A’BG series films display shape memory properties near room temperature. The A’BG series elastomer films have a high thermal stability and the temperatures of the 5% mass loss are above 300°C. The backbone siloxane structures in the A’BG series elastomer films are highly stable, and the -COOChol group is relatively easy to decompose.

Mechanism of high-moisture extruded protein fibrous structure formation based on the interactions among pea protein, amylopectin, and stearic acid

During high-moisture extrusion (HME) processing for plant protein texturization, the interactions among proteins, starch and lipids should determine the formation of fibrous structures, which has not been confirmed systematically. In this study, the mechanism of protein fibrous structure formation during HME processing (58% moisture) was investigated based on the intermolecular interactions among the pea protein, amylopectin and stearic acid. Results suggested that the amylopectin and stearic acid synergistically contributed to improve the fibrous structures such as the hardness and fibrous degree in pea protein extrudate. In the extruder barrel, the complexation among the protein with amylopectin and stearic acid gave rise to the formation of aggregates with higher thermal stability and delayed the formation of protein gel network. In the die, the amylopectin and stearic acid weakened the hydrogen bonds between proteins and hindered the aggregation of legumin and vicilin subunits. In the cooling zone and extrudate, the amylopectin and stearic acid promoted the formation of fibrous structures through an “anchor orientation and flexible cross-linking” mechanism. Namely, the stearic acid as anchors hindered the refolding of protein molecular chains, while the amylopectin promoted the rearrangement, cross-linking and aggregation of protein molecules. The amylopectin and stearic acid synergistically weakened the interaction forces between proteins and led to the formation of more flexible structures in aggregates, which was favorable for the orientation and formation of anisotropic fibrous structures in extrudates. This study provided a theoretical basis for the development and improvement of the plant-based meat substitutes.

A novel universal strategy for fabricating soybean protein adhesive with excellent adhesion and anti-mildew performances

Soybean meal (SM) adhesive is a promising alternative to petroleum-based ones. However, the poor water resistance, low bonding strength, and susceptibility to mildew limit its industrial application. Inspired by the micro-nano micelle structure's strengthening mechanism, a facile and green method of synthesizing a high-performance soy protein adhesive by a dual cross-linking strategy was reported. The in-situ self-assembled micelles of benzyldodecyldimethylammonium bromide (BDAB) interacted with protein chains via dynamical bonds, while 1,6-hexanediol diglycidyl ether (HDE) acted as the flexible cross-linker. The BDAB micelles interact with protein chains via non-covalent electrostatic interactions, improving the cross-linking density of the network system and the micelles with numerous amino cations exhibit efficient anti-bacterial properties. The as-obtained adhesive exhibits excellent mechanical properties and stable network structure, showing strong bonding strength and water resistance (2.22 and 1.25 MPa). Especially, the incorporation of HDE and BDAB imparts the modified SM adhesive with excellent antifungal and antibacterial (E. coli and S. aureus) performances, significantly extending the adhesive storage life. Additionally, this work provides a new facile and universal strategy for fabricating formaldehyde-free, environment-friendly, and renewable protein-based adhesives, which is a promising alternative to traditional adhesives in the wood industry.

Structural mechanism for bidirectional actin cross-linking by T-plastin

To orchestrate cell mechanics, trafficking, and motility, cytoskeletal filaments must assemble into higher-order networks whose local subcellular architecture and composition specify their functions. Cross-linking proteins bridge filaments at the nanoscale to control a network's μm-scale geometry, thereby conferring its mechanical properties and functional dynamics. While these interfilament linkages are key determinants of cytoskeletal function, their structural mechanisms remain poorly understood. Plastins/fimbrins are an evolutionarily ancient family of tandem calponin-homology domain (CHD) proteins required to construct multiple classes of actin networks, which feature diverse geometries specialized to power cytokinesis, microvilli and stereocilia biogenesis, and persistent cell migration. Here, we focus on the structural basis of actin network assembly by human T-plastin, a ubiquitously expressed isoform necessary for the maintenance of stable cellular protrusions generated by actin polymerization forces. By implementing a machine-learning-enabled cryo-electron microscopy pipeline for visualizing cross-linkers bridging multiple filaments, we uncover a sequential bundling mechanism enabling T-plastin to bridge pairs of actin filaments in both parallel and antiparallel orientations. T-plastin populates distinct structural landscapes in these two bridging orientations that are selectively compatible with actin networks featuring divergent architectures and functions. Our structural, biochemical, and cell biological data highlight inter-CHD linkers as key structural elements underlying flexible but stable cross-linking that are likely to be disrupted by T-plastin mutations that cause hereditary bone diseases.

Highly conductive branched poly(aryl piperidinium) anion exchange membranes with robust chemical stability

Poly(aryl piperidinium) (PAP) anion exchange membranes (AEMs) furnish an important avenue for the commercialization of anion exchange membrane fuel cells (AEMFCs), but their ionic conductivity and alkali resistance still need to be improved. Here, we report the synthesis of PAP AEMs with a branched structure by the acid-catalyzed reaction and compare them with the main-chain AEMs. The experimental results show that the branched AEMs have higher OH− conductivity and alkaline resistance than the poly(terphenyl piperidine) (PTPQ1) AEM. The alkaline stability and OH− conductivity of the AEMs were further improved by a flexible multi-cation crosslinker. The results show that the branched poly(p-terphenyl triphenylmethane 1-methyl piperidine) membrane crosslinked by multi-cation (PTTPQ4-40) shows an excellent OH− conductivity (155.3 mS cm−1) at 80 °C. The OH− conductivity of the PTTPQ4-40 membrane was maintained at 92.1% after soaking in 2 M NaOH for 1080 h at 80 °C. In addition, the peak power density (PPD) of the crosslinked PTTPQ4-40 membrane can reach 656.7 mW cm−2. Compared to the PTPQ1 AEM, the PPD of the crosslinked PTTPQ4-40 AEM is increased by 38.6% in H2-O2. All of the results confirm that the PTTPQ4-40 AEM has excellent fuel cell application prospects.

Durable and covalently attached antibacterial coating based on post-crosslinked maleic anhydride copolymer with long-lasting performance

Clinical application of silicone rubber often encounters challenges. Here a strategy of free radical polymerization with 2-ethylhexyl acrylate (2-EHA) and maleic anhydride (MAh) to introduce durable crosslinked antimicrobial coating that covalently attached on silicone rubber substrate. The 2-EHA and MAh component endow the copolymer with good flexibility and further functionalization respectively. The copolymer coating is covalently bonded to the amine functionalized silicone rubber surface using a simple dip-coating technique and the thickness is adjustable. Poly (hexamethylene biguanide) (PHMB) is covalently coupled on the coating under mild conditions, and the immobilization density of PHMB is up to 3 mg cm−2. The coating layer crosslinked by 1,4-butanediamine gas to enhance the durability of the coating and inhibit undesired swelling and remains intact after 500 bending cycles. The modified substrate exhibits excellent antibacterial activity, with 99.9 % and 95.1 % inhibition rate towards S. aureus and E. coli, respectively. It still maintained 96.2 % of inhibition activity even after 12-day-long culturing with bacteria in simulated urine environment, exhibiting excellent long-term antibacterial stability. The results show that a simple, universal and scalable method to introduce antibacterial properties on polymer substrates, which also provides a new idea for the preparation of flexible cross-linking layers.

Super-Flexibility and High-Temperature Adhesion of Epoxy Structural Adhesives Endowed by Homogeneous Rigid–Flexible Crosslinking Networks

Epoxy adhesives that combine flexibility, high-temperature adhesion property, and medium–low-temperature curing ability are an urgent need in the microelectronic device era. Unfortunately, it is still a challenge so far. In this context, two kinds of curing agents are combined to construct homogeneous rigid–flexible crosslinking networks via the stepwise curing method for preparing an epoxy adhesive with prominent deformation ability and high-temperature adhesive strength. Detailed analysis showed that the crosslinking network constructed by the stepwise curing method was higher and more homogenous than that of the one-step curing method. Benefitting from the homogeneous rigid–flexible crosslinking network, the elongation at break and high-temperature adhesion strength (200 °C) of the epoxy adhesive prepared by the stepwise method were up to about 100% and 1.60 MPa, respectively, which were about 1677.7 and 112.5% higher than those of the epoxy adhesive cured by the one-step curing method. The epoxy adhesive with medium–low-temperature curing ability, excellent flexibility, and high-temperature adhesion was first reported. It is expected that this work could provide some inspiration to design the special epoxy adhesives.