Oxidative Cross-linking Research Articles

Synergy stabilization of vitamin E and D-sorbitol on crosslinked ultrahigh molecular weight polyethylene for artificial joint under in-vitro clinically relevant accelerated aging

Maintaining reliability remains a great challenge for ultrahigh molecular weight polyethylene (UHMWPE) bearings due to oxidation in biological environments. This work aimed at inspecting the efficacy of the hybrid antioxidant strategy in stabilizing crosslinked UHMWPE under an in vitro clinically relevant accelerated aging condition. The hybrid antioxidant system was composed of vitamin E (VE) and D-sorbitol (DS) as primary and secondary antioxidants, respectively. The already established in vitro clinically relevant accelerated aging was performed via squalene absorption and subsequent thermal oxidation treatment. Compared to the use of VE alone, the combination of VE and DS significantly protracted the oxidation induction time of UHMWPE with no apparent oxidation after aging, showing a notable synergistic effect on the oxidative stability of UHMWPE. The crosslink density was higher for VE/DS/UHMWPE than VE/UHMWPE at each aging period. It revealed that the hybrid antioxidant strategy settled the longstanding contradiction between oxidation stability and crosslinking of UHMWPE. Attributed to improved oxidation stability, there was a positive reversal in the tensile property between VE/DS/UHMWPE and VE/UHMWPE after aging, where comparable ultimate tensile strength and higher elongation at break were observed. These findings underline the high potential of the hybrid antioxidant strategy for developing artificial joint materials with desired ability to resist oxidation and balanced performance.

Effects of antimony exposure on DNA damage and genome-wide variation in zebrafish (Danio rerio) liver

Antimony (Sb) is a potentially toxic and carcinogenic cumulative contaminant that poses a serious threat to aquatic ecosystems. To better clarify the genotoxicity of Sb and its mechanism of action. In this study, we investigated DNA damage and genome-wide variation in the liver of a model organism, zebrafish (Danio rerio), under subacute Sb exposure and explored its potential toxicological mechanisms. The results showed that medium and high concentrations of Sb significantly reduced the total antioxidant capacity and increased the content of reactive oxygen species in zebrafish liver, and further studies revealed that it increased oxidative DNA damage and DNA-DNA cross-link (DDC), but had little effect on DNA-protein cross-link (DPC). The result of resequencing showed that the mutation sites of the genes with high concentrations of Sb were higher than those with medium concentrations, and the mutation was mainly a single nucleotide. The pathways significantly enriched for nonsynonymous single nucleotide polymorphisms (SNPs) and insertion/deletion mutations (InDels) variant genes in the coding regions of both the medium and high Sb-treated groups were ECM-receptor interactions, and the high Sb-treated group also included lysine degradation, hematopoietic cell lineage, and cytokine-cytokine receptor interactions. This suggests that ECM-receptor interactions play an important role in the mechanism of antimony toxicity to the liver of zebrafish.

Direct and Efficient Incorporation of DOPA into Resilin-Like Proteins Enables Cross-Linking into Tunable Hydrogels.

3,4-Dihydroxyphenylalanine (DOPA), a naturally occurring yet noncanonical amino acid, endows protein polymers with diverse chemical reactivities and novel functionalities. Although many efforts have been made to incorporate DOPA into proteins, the incorporation efficiency and production titer remain low and severely hinder the exploration of these peculiar proteins for biomaterial fabrication. Here, we report an efficient biosynthetic strategy to produce large amounts of DOPA-incorporated structural proteins for the fabrication of hydrogels with tunable mechanical properties. First, synthetic genes were constructed that encode repetitive resilin-like proteins (RLPs) with varying proportions of tyrosine residues and molecular weights (Mw). Decoding of these genes into RLPs incorporated with DOPA was achieved via mis-aminoacylation of DOPA by endogenous tyrosyl-tRNA synthetase (TyrRS) in recombinant Escherichia coli cells. By developing a stoichiometry-guided two-phase culture strategy, we achieved independent control of the bacterial growth and protein synthesis phases. This enabled hyperproduction of the DOPA-incorporated RLPs at gram-per-liter levels and with a high DOPA incorporation yield of 76-85%. The purified DOPA-containing RLPs were then successfully cross-linked into bulk hydrogels via facile DOPA-Fe3+ complexations. Interestingly, these hydrogels exhibited viscoelastic and self-healing properties that are highly dependent on the catechol content and Mw of the RLPs. Finally, exploration of the molecular cross-linking mechanisms revealed that higher DOPA contents of the proteins would result in the concomitant occurrence of metal coordination and oxidative covalent cross-linking. In summary, our results suggest a useful platform to generate DOPA-functionalized protein materials and provide deeper insights into the gelation systems based on DOPA chemistry.

Multifunctional Flexible Pressure Sensor Based on a Cellulose Fiber-Derived Hierarchical Carbon Aerogel

Flexible pressure sensors have attracted widespread attention in recent years due to their potential applications for health monitoring and human–machine interfaces. However, the fabrication of environmentally friendly and well-performing pressure sensors using biobased materials remains a great challenge. Herein, a compressible carbon aerogel was prepared by sequential microfibrillation, periodate oxidization, and tannic acid (TA) cross-linking of cellulose fibers (CFs) followed by freeze-drying the as-prepared CF suspension and high-temperature pyrolysis of the obtained CF aerogel. The microfibrillation endows the carbon aerogel with a hierarchical structure, which improves the bonding strength and compressibility of the carbon aerogel. Periodate oxidation and TA cross-linking improved the mechanical properties of the carbon aerogel, while pyrolysis endowed the carbon aerogel with excellent conductivity, enabling the carbon aerogel to be a good pressure-sensing material. When assembled into a pressure sensor, the sensor shows a high sensitivity of 4 kPa–1, a fast response/recovery time of 32/30 ms, a low-pressure detection limit of 0.8 Pa, and good stability and excellent reproducibility (3000 cycles at 0.5 kPa). Moreover, the pressure sensor can be used to accurately monitor various human activities and also spatially resolve pressure variations when integrated into a sensor array. The pressure sensor also responds linearly to increased temperature and humidity. These results suggest that this hierarchical carbon aerogel-based pressure sensor has great potential for application as a multifunctional sensor.

A switch in FXYD proteins dysregulates NKA in dilated cardiomyopathy.

In the heart, Na+ homeostasis is established by the Na+/K+-ATPase (NKA). Because NKA is functionally linked to the Na+/Ca2+ exchanger, changes in NKA activity influence Ca2+ levels and cardiac contractility. It is well known that NKA in the heart is inhibited by FXYD1, a member of the FXYD protein family. However, the cardiac expression of other FXYDs has not been determined. In this study, western blot analysis revealed that FXYDs 5, 6 and 7 are also expressed in the human myocardium. In patients with dilated cardiomyopathy (DCM), FXYD1 expression was decreased and FXYD6 expression was increased. Furthermore, immunofluorescence staining showed that upregulation of FXYD6 in DCM patients occurs in the cardiomyocytes, which are the cells primarily responsible for cardiac contraction. FXYD6, like FXYD1 inhibits NKA. Thus, FXYD6 upregulation may be compensating for FXYD1 downregulation in order to maintain cardiac contractility. However, we observed that FXYD6 is expressed as dimers in the heart, but binds to NKA as monomers. Using fluorescence resonance energy transfer (FRET) and western blotting, we found that FXYD6 dimerization occurs due to oxidative crosslinking of cysteine residues (C9, C60 and C62). Additionally, mutation of FXYD6 cysteine residues decreased FXYD6 dimerization and increased binding with NKA, as measured by FRET. Together, these results suggest that in DCM, NKA is dysregulated by a switch from FXYD1 to FXYD6, which can become oxidized to form dimers, sequestering monomeric FXYD6 away from NKA. Decreased inhibition of NKA would lead to decreased Ca2+ levels and cardiac contractility, both of which are features of DCM.

Effect of the direct introduction of disulfide groups with 2-iminothiolane hydrochloride on wrinkle recovery of natural protein fibers

To develop environmentally friendly natural protein fibers with good wrinkle recovery without changing their excellent physical properties, thiol groups were directly introduced into silk and wool fibers by chemical modification using 2-iminothiolane hydrochloride. Thereafter, disulfide (–SS–) groups were introduced by oxidative cross-linking. The wrinkle recovery of the wool fabrics improved with the increase in 2-iminothiolane hydrochloride concentration. In particular, introducing the reduction process between the 2-iminothiolane hydrochloride treatment and the oxidation process improved the wrinkle recovery of wool fabrics. In contrast, the silk fabrics treated with 0.04 wt% 2-iminothiolane hydrochloride exhibited good wrinkle recovery. In addition, combustion-ion chromatography revealed that sulfur was introduced into the silk fabrics by oxidation after 2-iminothiolane hydrochloride treatment. According to these experiments, directly introducing –SS– groups using 2-iminothiolane hydrochloride into silk and wool fibers effectively improves wrinkle recovery without changing the physical properties of natural protein fabrics.

Exploring the Flexibility of the Glycopeptide Antibiotic Crosslinking Cascade for Extended Peptide Backbones.

The glycopeptide antibiotics (GPAs) are a clinically approved class of antimicrobial agents that classically function through the inhibition of bacterial cell-wall biosynthesis by sequestration of the precursor lipid II. The oxidative crosslinking of the core peptide by cytochrome P450 (Oxy) enzymes during GPA biosynthesis is both essential to their function and the source of their synthetic challenge. Thus, understanding the activity and selectivity of these Oxy enzymes is of key importance for the future engineering of this important compound class. Recent reports of GPAs that display an alternative mode of action and a wider range of core peptide structures compared to classic lipid II-binding GPAs raises the question of the tolerance of Oxy enzymes for larger changes in their peptide substrates. In this work, we explore the ability of Oxy enzymes from the biosynthesis pathways of lipid II-binding GPAs to accept altered peptide substrates based on a vancomycin template. Our results show that Oxy enzymes are more tolerant of changes at the N terminus of their substrates, whilst C-terminal extension of the peptide substrates is deleterious to the activity of all Oxy enzymes. Thus, future studies should prioritise the study of Oxy enzymes from atypical GPA biosynthesis pathways bearing C-terminal peptide extension to increase the substrate scope of these important cyclisation enzymes.

Modification of plant cell walls with hydroxycinnamic acids by BAHD acyltransferases.

In the last decade it has become clear that enzymes in the "BAHD" family of acyl-CoA transferases play important roles in the addition of phenolic acids to form ester-linked moieties on cell wall polymers. We focus here on the addition of two such phenolics-the hydroxycinnamates, ferulate and p-coumarate-to two cell wall polymers, glucuronoarabinoxylan and to lignin. The resulting ester-linked feruloyl and p-coumaroyl moities are key features of the cell walls of grasses and other commelinid monocots. The capacity of ferulate to participate in radical oxidative coupling means that its addition to glucuronoarabinoxylan or to lignin has profound implications for the properties of the cell wall - allowing respectively oxidative crosslinking to glucuronoarabinoxylan chains or introducing ester bonds into lignin polymers. A subclade of ~10 BAHD genes in grasses is now known to (1) contain genes strongly implicated in addition of p-coumarate or ferulate to glucuronoarabinoxylan (2) encode enzymes that add p-coumarate or ferulate to lignin precursors. Here, we review the evidence for functions of these genes and the biotechnological applications of manipulating them, discuss our understanding of mechanisms involved, and highlight outstanding questions for future research.

Improvement in Acid Resistance of Polyimide Membranes: A Sustainable Cross-Linking Approach via Green-Solvent-Based Fenton Reaction

In this study, we present a facile surface modification method using green solvents for a commercial polyimide (PI) nanofiltration membrane to exhibit good acid stability. To enhance acid stability, the PI organic solvent nanofiltration membrane was modified using Fenton's reaction, an oxidative cross-linking process, using environmentally friendly solvents: water and ethanol. The surface properties of the pristine and modified PI membranes were investigated and compared using various analytical tools. We studied the surface morphology using scanning electron microscopy, performed elemental analysis using X-ray photoelectron spectroscopy, investigated chemical bonds using attenuated total reflectance-Fourier transform infrared spectroscopy, and studied thermal stability using thermogravimetric analysis. The acid resistances of the pristine and modified membranes were confirmed through performance tests. The pristine PI nanofiltration membrane exposed to a 50 w/v% sulfuric acid for 4 h showed an increase in the normalized water flux to 205% and a decrease in the MgSO4 normalized rejection to 44%, revealing damage to the membrane. The membrane modified by the Fenton reaction exhibited a decline in flux and improved rejection, which are typical performance changes after surface modification. However, the Fenton-modified membrane exposed to 50 w/v% sulfuric acid for 4 h showed a flux increase of 7% and a rejection increase of 4%, indicating improved acid resistance. Furthermore, the Fenton post-treatment enhanced the thermal stability and organic solvent resistance of the PI membrane. This study shows that the acid resistance of PI membranes can be successfully improved by a novel and facile Fenton reaction using green solvents.

Хімічний склад сполук-попередників та механізми утворення гумінових речовин у постседиментаційний етап еволюції органічних сполук

The publication is a review that presents in a concise form information about the chemical composition of living matter components and the mechanisms of their transformations, the result of which is the geopolymers formation. Among geopolymers, humic substances, including humic and fulvic acids, attract our attention. The relevance of this review lies in the importance of understanding multidirectional reactions, the result of which is the secondary polymerization of organic matter chemically active components that have passed the biodegradation barrier at the stage of sedimentation and diagenetic transformations. Humic substances, in their turn, are precursors of kerogen, therefore, an understanding of reaction mechanisms and their products provides complete information about the conditions of various types of kerogen formation, which are characterized by different ability to produce oil and gas. We paid special attention to polyphenols, which have high chemical activity and the ability to react with increasing molecular weight. In addition to the traditional Maillard reaction, among the condensation mechanisms we considered oxidative crosslinking of phenols, oxidative condensation of polyunsaturated fatty acids, and esterification of fatty acids with phenols. For each mechanism, the conditions for its implementation and probable contribution to the formation of humic substances are briefly considered. Analysis of probable mechanisms of formation of humic substances showed that condensation reactions can occur under geochemical conditions of sedimentation and early diagenesis. At the same time, their speeds are low, and the precursors necessary for the reactions, formed as a result of biological degradation, are contained in very small concentrations. We conclude that kerogen contains two components – primary, which enters its structure without any significant changes, and secondary, which is the result of a series of complex multidirectional reactions.

Resin-supported cyclic telluride as a heterogeneous promoter of disulfide formation under solid–liquid biphasic conditions

A resin-supported cyclic telluride effectively promoted oxidation of thiols in polypeptides as well as small molecules in a solid–liquid biphasic reaction system, providing the corresponding pure disulfide states without a purification process.

Antioxidant N-acetylcysteine removing ROS: an antifouling strategy inspired by mussels.

Marine biofouling is a thorny issue that causes serious economic losses and adverse ecological impacts on marine ecosystems. Effective and promising antifouling strategies such as surface hydration, flow shear force, and lubricant injection have been developed to address this challenge. However, for the complex marine environment, they still appear inadequate. Mussels are a common fouling organism with strong surface adhesion ability. However, when hypoxia and the oxidative cross-linking reaction of 3,4-dihydroxy phenyl-L-alanine (DOPA) in the structure of adhesion proteins are disrupted, their adhesion ability will be greatly reduced. Inspired by this, we developed an effective antifouling strategy based on reactive oxygen species (ROS) scavenging using N-acetylcysteine (NAC) and evaluated its performance. As a ROS scavenger interfered with the oxidative cross-linking reaction of DOPA in an aqueous solution, the adhesion of DOPA was also affected on the surface of NAC functionalized polyvinyl chloride (PVC) (PVC-NAC). In addition, the colonization level of mussels and the adhesion rate of marine bacteria and benthic diatoms on PVC-NAC were low. The antifouling strategy proposed in this paper was eco-friendly and broad-spectrum, and may provide a new idea for solving marine biofouling and reducing the environmental and economic impacts of fouling organisms.

Cross-Linking and Functional Analyses for Dimerization of a Cysteine Mutant of Glycine Transporter 1.

Glycine transporter 1 (GlyT1) is responsible for the reuptake of glycine, which regulates glutamate signaling as a co-agonist with N-methyl-D-aspartic acid (NMDA) receptors in the excitatory synapse and has been proposed to be a potential target in the development of therapies for a broad range of disorders of the central nervous system. Despite significant progress in characterizing structure and transport mechanism of the transporter, the regulation of transport function through oligomerization remains to be understood. In the present work, association of two forms of GlyT1 into dimers and higher order oligomers was detected by coimmunoprecipitation. To investigate functional properties of dimers of a GlyT1 cysteine mutant L288C, we performed oxidative cross-linking of the positioned cysteine residues in extracellular loop 3 (EL3) near the extracellular end of TM6. By analyzing the effect of copper phenanthroline (CuP)-induced dimerization on transport function, cross-linking of L288C was found to inhibit transport activity. In addition, an intramolecular ion pair Lys286-Glu289 was revealed to be critical for stabilizing EL3 in a conformation that modulates CuP-induced dimerization and transport function of the GlyT1 L288C mutant. Furthermore, the influence of transporter conformation on GlyT1 L288C dimerization was investigated. The substrate glycine, in the presence of both Na+ and Cl-, significantly reduced oxidative cross-linking, suggesting a large-scale rotation of the bundle domain during substrate transport impairs interfacial interactions between L288C protomers. The present study provides new insights into structural and functional elements regulating GlyT1 transport activity through its dimerization or oligomerization.

Polymer Materials Synthesized through Cell-Mediated Polymerization Strategies for Regulation of Biological Functions

ConspectusAs essential components of living organisms, biomacromolecules construct cell scaffolds and regulate cell activities and biological functions through chemical transformations in biological systems. Inspired by the functional evolution in the formation of natural structures, in situ polymerization methods have been developed to create functional synthetic macromolecules inside or on the surface of living cells. Given the diversity of cell species and the complexity of biological pathways, selected strategies can be employed to control the synthesis of functional polymers that utilize the dynamic cellular microenvironment.In this Account, we summarize recent work in the field of designing cell-mediated in situ polymerization methods, with which we demonstrate their application prospects including tumor cell labeling and treatment, microbial photosynthetic efficiency regulation, and hydrogel generation. The purpose of these efforts is to design polymerization reactions in response to endogenous or exogenous stimuli and to describe the underlying response mechanisms. By reasonable design of molecular structures, in situ synthesized polymers in the cell microenvironment implement regulation of biological functions. For example, using specific redox activity combined with light irradiation, bacteria can mediate the generation of functional polymers as the encapsulating matrix or with antibacterial effects. Conjugated polymers synthesized on the microalgae surface expanded the spectral absorption and improved photosynthetic efficiency. Meanwhile, characteristics of the cellular microenvironment could initiate various polymerization reactions inside living cells, including oxidative thiol cross-linking, condensation polymerization, and free radical polymerization. These reactions can be selectively conducted with reactive species generated in tumor cells, and the resulting polymers showed prolonged retention inside cells for modulating cell behaviors. Further development of cell-mediated polymerization strategies would provide an innovative platform for research and applications of multifunctional biomaterials and engineered biohybrid systems.

Research on the vacuum aging performance of HTPB propellant based on the DSC method

The space environment has extreme conditions such as high vacuum and rapid temperature changes, which will lead to problems such as energy drop, irregular burning rate, and abnormal ignition of solid propellants. To obtain the space aging law of HTPB propellant, the aging performance of HTPB (hydroxyl-terminated polybutadiene) propellant in a vacuum environment was studied and compared with that under the atmosphere. According to the DSC test results of the propellant before and after aging, the behaviors of oxidative crosslinking, chain-scission degradation, and oxidant decomposition during the aging process of solid propellant were investigated. The research showed that the low-temperature endothermic peak and “V-type” high-temperature exothermic peak temperature of HTPB propellant increased after aging, and the high-temperature peak bifurcated into “W-type” double peaks. The right peak caused by the “decarboxylation” reaction was more obvious after atmospheric aging while the left peak caused by AP decomposition was remarkable after vacuum aging. In addition, the oxidative crosslinking reaction occurred after aging, and the activation energy characterized by low-temperature peaks continued to increase. In the later stage of atmospheric aging, chain-scission degradation occurred due to OA moisture absorption, and the activation energy decreased. It firstly increased by 126% within 93 days, and then decreased by 23.4%. No degradation and chain-scission reaction occurred in a vacuum environment, the crosslinking reaction rate was high, and the activation energy increased by 40.4% within 49 days. After the aging of the HTPB propellant, the internal AP decomposed, and the activation energy characterized by the high-temperature exothermic right peak continued to increase. The activation energy increased by 40.5% within 49 days after vacuum aging, and increased by 29.9% within 93 days after atmospheric aging, indicating that the decomposition of AP in the HTPB propellant was more obvious under a vacuum environment.

Synergistic improvement of CO2/CH4 separation performance of phenolphthalein-based polyimide membranes by thermal decomposition and thermal-oxidative crosslinking

Thermal oxidative crosslinking results in the generation of oxygen bridges among polymer chains and helps regulate the membrane microstructure. Simultaneously, any strategy to increase the crosslinking sites of polyimide (PI) can improve the crosslinking efficiency and allow precise control of the pore structure of membranes. Phenolphthalein-based PIs are potentially suitable precursors for thermal oxidative crosslinking of membranes, since thermal treatment will result in the degradation of lactone ring leading to the generation of a pair of phenyl crosslinking sites. In this work, three phenolphthalein-based diamines with different structures were designed and synthesized. The three diamines were subsequently reacted with 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) to prepare phenolphthalein-based PIs. The original membranes were post-treated by thermal oxidation crosslinking at 400 °C and 425 °C, respectively; the lactone ring underwent decomposition, and the imide ring opened at the same time, resulting in the generation of multiple crosslinking sites and correspondingly improving the crosslinking efficiency. The effect of the side groups (−CH3, –CF3 or unsubstituted) of phenolphthalein-based diamine and thermal treatment temperatures on the gas separation performance of phenolphthalein-based PI membranes were investigated. Wide-angle X-ray diffractometry (WAXD) and wide-angle X-ray scattering (WAXS) analysis demonstrated that the π-π stacking distance were improved. BTDA-FPP-425 had a CO2/CH4 selectivity of 37.68. This thermal degradation along with thermal oxidative crosslinking strategy provides a promising approach for fabrication of CO2/CH4 separation membrane.

SiOC Phase Control and Carbon Nanoribbon Growth by Introducing Oxygen at Atom Level for Lithium-Ion Batteries.

Poor intrinsic conductivity and the presence of irreversible lithiation phase affect the electrochemical performance of silicon oxycarbide anode materials. Even though it can be improved by increasing free carbon content or composition, scarification of reversible capacity and initial Coulombic efficiency (ICE) remain as challenge. Here, polycarbosilane (PCS) with alternating distribution of silicon and carbon atoms is employed as precursor of SiOC ceramics. Air oxidation cross-linking is used to regulate the content of oxygen and carbon elements in PCS at atom level, so as to explore a solution to improve the intrinsic conductivity and reversible lithium phase content of SiOC ceramics. This strategy provides extremely excellent rate capability, areal/volumetric capacity, and ICE. This is also the first concept for feasible precursor structure design to control the SiOC glass phase and regulate the growth of C nanoribbon that can improve the intrinsic conductivity and reversible capacity of SiOC ceramic anode materials.

Metal-binding proteins and cross-linking in the defensive glue of the slug Arion subfuscus.

The role of metals in forming the primary cross-links in slug glue was investigated. Several metal-binding proteins were identified in the defensive glue produced by the slug Arion subfuscus. Notably, the C-lectins that are unique to the glue are iron-binding proteins. This is unusual for C-lectins. Dissociating these proteins from iron does not affect the glue's stiffness. Similarly, several proteins that can bind to zinc were identified, but dissociating the proteins from zinc did not weaken the glue. These results suggest that metal coordination is not involved in the primary cross-links of this hydrogel glue. The stable cross-links that provide stiffness are more likely to be created by a catalytic event involving protein oxidation. Cross-linking was unexpectedly difficult to prevent. Collecting the glue into a large volume of ice-cold buffer with reagents aimed at inhibiting oxidative cross-linking caused a slight loss of cross-linking, as demonstrated by the appearance of uncross-linked proteins in native gel electrophoresis. Notable among these was a protein that is normally heavily oxidized (asmp165). Nevertheless, this effect was not large, suggesting that the primary cross-links form before secretion.

Topologically Enhanced Cation–π Interactions for Developing High‐Performance Underwater Adhesive

AbstractCation–π interactions provide an excellent way to develop high‐performance underwater adhesives. Although numerous underwater adhesive systems are designed based on cation–π interactions, they still lack precise design of the adhesive polymer backbone and topological control of the adhesive polymer. In this study, a novel short‐chain adhesive polymer with excellent underwater adhesion is developed based on the topologically enhanced cation–π interactions. Dihydrocaffeic acid containing catechol is incorporated into a short‐chain cationic polymer of polycarbodiimides through the nucleophilic reactions between carboxyl and carbodiimide groups to produce a catechol‐decorated cationic adhesive polymer (CCAP). The unique molecular structure of the CCAP confers the adhesive system strong cohesion and topologically enhanced cation–π interactions, leading to excellent underwater adhesion. Fe3+ is introduced into the adhesive system to promote the coordination of catechol and the oxidative crosslinking of catechol to further improve the cohesion of the CCAP. In addition, based on the synergy between reversible noncovalent bonds and the irreversible oxidative crosslinking system, the prepared adhesive can also act as a high‐strength hot‐melt adhesive, which maintains nearly 90% of its adhesion strength after 10 attachment–detachment cycles, showing its great potential for use as a sustainable reusable dismountable adhesive. This study provides a novel strategy to develop high‐performance underwater adhesive with temperature sensitivity.

Fluoroalkylated-GAP copolymers (GAP-FP) as promising energetic binders

The development of a novel energetic block copolymer of glycidyl azide polymer (GAP) and fluoropolymer (FP) using a boron trifluoride-tetrahydrofuran complex/diol initiator system is reported herein. Well-defined compositions of the GAP-FP copolymers in two different GAP to FP ratios (1:1 and 1:3) were synthesized by tailoring the desired molecular weights of each block in the copolymer, demonstrating the synthetic versatility of such a copolymer system. The resultant GAP-FP copolymers represent a unique hybrid binder system with tunable energy releasing and oxidizing potentials intended for metallized formulations. Thermogravimetric analysis showed that the carbonaceous residue usually formed from the decomposition of GAP could be reduced significantly by the copolymerization with FP. Isoconversional method of kinetic analysis of the GAP-FP copolymers revealed an increasing dependence of the effective activation energy on the extent of conversion. The increasing dependence suggested a mechanism of the competing reactions that were found to be between the reactions of FP triggered oxidation and intermolecular crosslinking of the polyimine intermediates formed from GAP decomposition that ultimately resulted in the reduction of the carbonaceous residue.