Surface Modification of Aramid Fibers by Catechol/Polyamine Codeposition Followed by Silane Grafting for Enhanced Interfacial Adhesion to Rubber Matrix

Metal-polyphenol networks-modified tantalum plate for craniomaxillofacial reconstruction

Using three-dimensional (3D) printing technology to make the porous tantalum plate and modify its surface. The physicochemical properties, cytocompatibility, antioxidant capacity, and histocompatibility of the modified materials were evaluated to prepare for the repair of craniomaxillofacial bone defects. The porous tantalum plates were 3D printed by selective laser melting technology. Tantalum plates were surface modified with a metal polyphenol network. The surface-modified plates were analyzed for cytocompatibility using thiazolyl blue tetrazolium bromide and live/dead cell staining. The antioxidant capacity of the surface-modified plates was assessed by measuring the levels of intracellular reactive oxygen species, reduced glutathione, superoxide dismutase, and malondialdehyde. The histocompatibility of the plates was evaluated by animal experiments. The results obtained that the tantalum plates with uniform small pores exhibited a high mechanical strength. The surface-modified plates had much better hydrophilicity. In vitro cell experiments showed that the surface-modified plates had higher cytocompatibility and antioxidant capacity than blank tantalum plates. Through subcutaneous implantation in rabbits, the surface-modified plates demonstrated good histocompatibility. Hence, surface-modified tantalum plates had the potential to be used as an implant material for the treatment of craniomaxillofacial bone defects.

Catechol-tetraethylenepentamine co-deposition modified cellulose filter paper for α-glucosidase immobilization and inhibitor screening from traditional Chinese medicine

Cellulose filter paper (CFP) is expected to be an ideal carrier for enzyme immobilization due to its sustainability and biocompatibility. However, the interaction between the carrier and enzyme might change the spatial conformation of the enzyme and its microenvironment, and thus the flexibility of the enzyme molecule or the transport of the substrate to the active site would be hampered. In this work, a two-component system of catechol and tetraethylene pentamine was used to replace dopamine, and a polydopamine-like composite layer was deposited on the surface of CFP to introduce amino groups, which was similar to the self-polymerization-adhesion behavior of dopamine. Using polyethylene glycol diglycidyl ether with flexible spacer arms as the cross-linking agent, α-glucosidase was covalently bonded to amino-modified CFP through an epoxy ring-opening reaction. The immobilized α-glucosidase exhibited greater tolerance to pH and high temperature. After 10 repeated uses, the immobilized α-glucosidase maintained relatively high enzyme activity. Its kinetic behavior was investigated to illustrate the reliability for enzyme inhibitor screening. Finally, a screening method combining an immobilized enzyme and capillary electrophoresis analysis was proposed and applied to screening inhibitors from 11 kinds of traditional Chinese medicines, among which Chebulae Fructus, Phyllanthi Fructus and Terminaliae Relliricae Fructus exhibited strong enzyme inhibitory activities.

Highly Strong Interface Adhesion of Polyester Fiber Rubber Composite via Fiber Surface Modification by Meta-Cresol/Formaldehyde Latex Dipping Emulsion

As a skeleton material, polyester (PET) fiber can significantly improve the strength and durability of rubber composites, but the interfacial adhesion between polyester fiber and rubber is poor due to the chemical inertia of PET fiber surface. Resorcinol-formaldehyde-latex (RFL) impregnating solution is usually used to treat PET fibers, but RFL contains toxic components such as resorcinol, which is harmful to the human body. A simple and less toxic resin-impregnating system cresol-formaldehyde-latex (CFL) was obtained by alternating resorcinol with low-toxicity cresol and m-cresol formaldehyde resin was synthesized from m-cresol and formaldehyde. CFL (m-cresol formaldehyde resin latex) systems with different C/F mole ratios and CF resin/latex ratios were adopted to modify the surface of PET fibers. The strip peeling adhesive and the H pull-out test results indicated that the PET fiber/rubber adhesion strength increased with the increase in the formaldehyde dosage and the CF resin content, and the peeling force value and the H-pull-out force of treated PET/rubber composites reached 7.3 N/piece and 56.8 N, respectively. The optimal choice of CFL adhesive system was obtained, when the C/F mole ratio was 1/2 and the CF resin/latex weight ratio was 0.23. This environment-friendly CFL dipping emulsion can be used as a new surface modification strategy as it can remarkably enhance the interfacial adhesion of PET/rubber composites.

Polydopamine and Mercapto Functionalized 3D Carbon Nano-Material Hybrids Synergistically Modifying Aramid Fibers for Adhesion Improvement

In order to solve the problem of poor interfacial adhesion between aramid fibers and a rubber matrix, an efficient and mild modification method was proposed via polydopamine and mercapto functionalized graphene oxide (GO) and carbon nanotube (CNTs) hybrids synergistically modifying aramid fibers. GO and CNTs were firstly stacked and assembled into unique 3D GO-CNTs hybrids through π-π conjugation. Then, the mercapto functionalization of the assembled 3D GO-CNTs hybrids was realized via the dehydration condensation reaction between the hydroxyls of GO and the silanol groups of coupling agent. Finally, the mercapto functionalized 3D GO-CNTs hybrids were grafted onto the aramid fibers, which were pre-modified by polydopamine through the Michael addition reaction mechanism. The surface morphology and chemical structures of GO-CNTs hybrids and fibers and the interfacial adhesion strength between fibers and rubber matrix were investigated. The results showed that the modification method had brought about great changes in the surface structure of fibers but not generated any damage traces. More importantly, this modification method could improve the interfacial strength by 110.95%, and the reason was not only the reactivity of functional groups but also that the 3D GO-CNTs hybrids with excellent mechanical properties could effectively share interfacial stress. The method proposed in this paper was universal and had the potential to be applied to other high-performance fiber-reinforced composites.

Fabrication of Highly Conductive Silver-Coated Aluminum Microspheres Based on Poly(catechol/polyamine) Surface Modification

A novel and cost-effective method for the fabrication of highly conductive Al/Ag core-shell structured microspheres was proposed and investigated. The oxidative co-deposition of catechol and polyamine was firstly performed to modify the surface of the aluminum microsphere. Then, a two-step electroless plating was conducted to fabricate the Al/Ag microspheres. During the first step of the electroless plating process, the surface of the aluminum microsphere was deposited with silver nanoparticle seeds using n-octylamine and ethylene glycol. Then, during the second step of the electroless plating process, silver particles grew evenly to form a compact silver shell on the surface of aluminum via a silver mirror reaction. According to the scanning electron microscope and energy dispersive X-ray results, a compact and continuous silver layer was successfully generated on the surface of the aluminum. The valence of the sliver on the surface of the aluminum was confirmed to be zero, based on the X-ray photoelectron spectrometer and X-ray diffractometer analyses. As a result, the as-prepared Al/Ag microspheres exhibited a high conductivity of 10,000 S/cm. The Al/Ag/MVQ composite demonstrated low electrical resistivity of 0.0039 Ω·cm and great electromagnetic interference shielding effectiveness at more than 70 dB against the X-band, and this result suggests that the as-prepared composite is a promising conductive and electromagnetic shielding material.

Bioinspired polydopamine deposition and silane grafting modification of bamboo fiber for improved interface compatibility of poly (lactic acid) composites

The surface of bamboo fiber (BF) has poor interface compatibility with the surface of the poly (lactic acid) (PLA), which compromises composite performance. In this study, a bioinspired polydopamine (PDA) function coating was constructed on a BF surface to act as a bridge to introduce an epoxy-functionalized silane layer (KH560). The results of the test confirmed that KH560 was successfully grafted onto the surface of the BF. Therefore, the flexural, tensile, and impact strength of the modified composites increased by 37.22%, 49.64%, and 26.66%, respectively, compared with that of the untreated composites. Furthermore, the PDA-KH560-modified BF enhanced the PLA composites' thermal stability. This strategy is assumed to provide a simple and green method for improving interface adhesion strength and potentials for future manufacturing of high-performance composites.

Enzymatic treatment of phenolic pollutants by a small laccase immobilized on APTES-functionalised magnetic nanoparticles

In this study, we have successfully synthesized magnetic nanoparticles (MNPs), functionalised them by silanization and used them for the covalent immobilization of a recombinant small laccase (rSLAC) from Streptomyces coelicolor. The immobilized recombinant laccase (MNP-rSLAC) was subsequently used for the treatment of phenol, 4-chlorophenol (4-CP) and 4-fluorophenol (4-FP). The enzyme completely degraded 80 µg/mL of the selected phenolic compounds within 2 h in the presence of a natural mediator, acetosyringone. The MNP-rSLAC retained > 73% of initial activity (2,6-dimethoxyphenol as substrate) after 10 catalytic cycles and could be easily recovered from the reaction mixture by the application of magnetic field. Furthermore, immobilised rSLAC exhibited better storage stability than its free counterpart. The Michaelis constant (K_m) value for the immobilised rSLAC was higher than free rSLAC, however the maximum velocity (V_max) of the immobilised SLAC was similar to that of the free rSLAC. Growth inhibition studies using Escherichia coli showed that rSLAC-mediated treatment of phenolic compounds reduced the toxicity of phenol, 4-CP and 4-FP by 90, 60 and 55%, respectively. Interestingly, the presence of selected metal ions (Co²⁺, Cu²⁺, Mn²⁺) greatly enhanced the catalytic activity of rSLAC and MNP-rSLAC. This study indicates that immobilized small laccase (MNP-rSLAC) has potential for treating wastewater contaminated with phenolic compounds.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02854-0.

Understanding the self-polymerization mechanism of dopamine by molecular simulation and applying dopamine surface modification to improve the interfacial adhesion of polyimide fibers with epoxy resin matrix

The object of this paper is to interpret the self-polymerization mechanism of dopamine by molecular simulation and use dopamine polymerization to modify the surface properties of polyimide fibers for improving its interfacial adhesion strength with the epoxy resin matrix. Theoretically, the molecular simulation results of calculated energy band gaps and infrared spectrum of the intermediate products generated in the dopamine self-polymerization process confirmed that the spontaneity of self-polymerization of dopamine and the occurrence of intramolecular cyclization and intermolecular polymerization in the self-polymerization process of dopamine. Moreover, the interaction between polyimide and poly(dopamine) was simulated, and the calculated results showed that the interaction between them depended on hydrogen bonding and was verified by ultrasound treatment. Experimentally, the effect of dopamine treatment concentration on the surface properties of polyimide fibers was investigated. Obviously, after a relatively high dopamine concentration treatment, the surface roughness and surface energy of polyimide fibers were largely improved and the number of active groups on polyimide fibers surface were increased, which were altogether conducive to enhance the adhesion strength of polyimide fibers with the epoxy resin matrix.

Toward high-performance nanofibrillated cellulose/aramid fibrid paper-based composites via polyethyleneimine-assisted decoration of silica nanoparticle onto aramid fibrid

Flexible paper-based nanocomposites dielectrics are of crucial importance in electrical insulation and advanced electrical power systems. In this work, a novel nanofibrillated cellulose/aramid fibrid (NFC/AF) composite was fabricated by vacuum-assisted filtration process. In order to improve the dielectric property of the composites, carboxylated nano-SiO₂ was chemically coated onto aramid fibrid via molecular self-assembly with the aid of phosphoric acid (PA) pretreatment and subsequent polyethyleneimine (PEI) functionalization. It was found that composites prepared by NFC and (PEI/SiO₂)-modified AF (after crosslinking) ((PEI/SiO₂)-AF) showed dense structure, which was mainly due to enhanced interfacial interaction between AF and NFC. Consequently, NFC/(PEI/SiO₂)-AF paper-based composites showed better tensile toughness (∼6 % elongation at break) and mechanical strength (∼36.28 MPa), in comparison with NFC/AF. More importantly, the electrical insulation performance and thermal stability of the composites were significantly improved. Accordingly, this work provides a facile approach to fabricate high-performance dielectric composites especially for high-temperature electrical insulation applications.

Thermally Conductive Elastomer Composites with Poly(catechol-polyamine)-Modified Boron Nitride

Effective heat dissipation has become a major concern with the rapid development of microelectronic devices. In general, thermally conductive fillers are incorporated into the polymeric matrix to increase the thermal conductivity of polymer composites. Herein, poly(catechol-polyamine) (PCPA) is employed to modify boron nitride (BN) platelets, referred to as BN-PCPA, and improves the interfacial compatibility between a thermally conductive filler and elastomer matrix, resulting in carboxylated acrylonitrile-butadiene rubber (XNBR) composites filled with BN-PCPA platelets with enhanced thermal conductivity. The influence of PCPA thickness on the mechanical properties, thermal conductivity, and dielectric properties of BN-PCPA/XNBR composites is systematically studied. Briefly, the interfacial compatibility between the BN-PCPA filler and XNBR matrix increases with increasing PCPA thickness, leading to enhanced thermal conductivity. The maximum thermal conductivity of 0.399 W/(m·K) has been rendered by the BN-PCPA-12h/XNBR composite, which is about 2.5 times of pure XNBR. This work provides an easy route to develop polymer composites with a relatively high thermal conductivity and high dielectric constant for potential application in practical electronic packaging.

Development in Additive Methods in Aramid Fiber Surface Modification to Increase Fiber-Matrix Adhesion: A Review

This review article highlights and summarizes the recent developments in the field of surface modification methods for aramid fibers. Special focus is on methods that create a multifunctional fiber surface by incorporating nanostructures and enabling mechanical interlocking. To give a complete picture of adhesion promotion with aramids, the specific questions related to the challenges in aramid-matrix bonding are also shortly presented. The main discussion of the surface modification approaches is divided into sections according to how material is added to the fiber surface; (1) coating, (2) grafting and (3) growing. To provide a comprehensive view of the most recent developments in the field, other methods with similar outcomes, are also shortly reviewed. To conclude, future trends and insights are discussed.

Reversibly-regulated drug release using poly(tannic acid) fabricated nanocarriers for reduced secondary side effects in tumor therapy

Numerous nanocarriers with pH-responsive properties have been designed and fabricated to reduce the adverse side effects of traditional chemotherapeutics, but these traditional nanocarriers are rarely reversible; this may cause "secondary" side effects on normal tissues, because the nanocarriers cannot be sealed again to prevent the leakage of incompletely released drugs after re-entering blood circulation. To overcome these limitations, we report herein the synthesis of a reversibly pH-responsive drug delivery system, which can achieve regulated drug release in a "release-stop-release" manner corresponding to changes in pH. Specifically, poly(tannic acid) as the "gatekeeper" was firstly deposited and polymerized on the surface of mesoporous silica nanoparticles (MSNs) via a modified mussel-inspired method similar to dopamine, and the formed polymer shell can be easily decorated with a targeting ligand HER2 antibody for the selective delivery of drugs to specific cells. The resulting nanocomposites exhibited good colloidal stability, good biocompatibility, high drug loading capacity and accurate HER2 antibody mediated targeting ability. Interestingly, a series of experiments fully demonstrated that the fabricated nanocomposites possessed intelligent reversible pH-responsive controlled release behavior through adjusting the density of the "gatekeeper" under different pH conditions, thereby achieving reversible switching from "on" to "off". Furthermore, in vitro and in vivo experiments verified that the fabricated targeting nanoparticles could efficiently inhibit tumor growth with minimal side effects. Meanwhile, these nanocarriers exhibited excellent reusability, in vitro cytotoxicity and minimal in vivo myocardial damage. Collectively, the reversible pH-operated nanovalve on the MSNs constructed here could serve as a nanoplatform to solve the problem of "secondary" side effects caused by residual drugs in irreversible "gatekeeper" systems.

Development, Validation, and Performance of Chitosan-Based Coatings Using Catechol Coupling

The use of long-lasting polymer coatings on biodevice surfaces has been investigated to improve material-tissue interaction, minimize adverse effects, and enhance their functionality. Natural polymers, especially chitosan, are of particular interest due to their excellent biological properties, such as biocompatibility, non-toxicity, and antimicrobial properties. One way to produce chitosan coating is by covalent grafting with catechol molecules such as dopamine, caffeic acid, and tannic acid, resulting in an attachment ten times stronger than that of simple physisorption. Caffeic acid presents an advantage over dopamine because it allows direct chitosan grafting, due to its terminal carboxylic acid group, without the need of a linking arm, as employed in the dopamine approach. In this study, the grafting of chitosan using caffeic acid, over surfaces or in solution, is compared with dopamine grafting using poly(ethylene glycol) as a linking arm. The following coating properties are observed; covering and homogeneity are assessed by X-ray photoelectron spectroscopy and atomic force microscopy analyses, hydrophilicity with contact angle measurements, stability with aging tests, anticorrosion behavior, and coating non-toxicity. Results show that grafting using caffeic acid/chitosan in solution over a metallic surface may be advantageous, compared to traditional dopamine coating.

A Simple Low-Cost Method to Prepare Lignocellulose-Based Composites for Efficient Removal of Cd(II) from Wastewater

The fabrication of functional lignocellulose-based materials has drawn considerable attention because it acts as a green separation/absorption material owing to its multi-porous mesostructure. In this study, a surface functionalized lignocellulose-based adsorbent for the highly efficient capture of Cd(II) ions was prepared through facile in situ co-deposition of wood waste-derived saw powder (SP) in the presence of tannic acid (TA) and aminopropyltriethoxysilane (APTES) mixed aqueous solution. The SP was first modified using TA-APTES coating to synthesize the functional SP substrate (SP-(TA-APTES)). The SP-(TA-APTES) hybrids served as reactive platforms, which enabled further decoration with amino-rich polyethylenimine (PEI) due to the outstanding secondary reactions of the TA-APTES layer. The surface morphology of the resulting SP-(TA-APTES)-PEI (SP-TAPI) composites were investigated using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Significantly, the combined advantages of the lignocellulosic skeleton, the layer-particle structure, and the hybrid coating contributed to the enhanced adsorption capacity of Cd(II) (up to 22.66 mg/g at pH = 5.0). This removal capacity was higher than that of most reported agricultural waste-based or lignocellulose-based materials. The Cd(II) adsorption mechanism of the surface-modified SP-TAPI composites was studied in detail. These results provide new insights into the high value-added utilization of agricultural waste for water purification applications.

A Novel Method for Deposition of Multi-Walled Carbon Nanotubes onto Poly(p-Phenylene Terephthalamide) Fibers to Enhance Interfacial Adhesion with Rubber Matrix

In order to enhance the interfacial adhesion of poly(p-phenylene terephthalamide) (PPTA) fibers to the rubber composites, a novel method to deposit multi-walled carbon nanotubes (MWCNTs) onto the surface of PPTA fibers has been proposed in this study. This chemical modification was performed through the introduction of epoxy groups by Friedel⁻Crafts alkylation on the PPTA fibers, the carboxylation of MWCNTs, and the ring-opening reaction between the epoxy groups and the carboxyl groups. The morphologies, chemical structures, and compositions of the surface of PPTA fibers were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that MWCNTs were uniformly deposited onto the surface of PPTA fibers with the covalent bonds. The measurement of contact angles of the fibers with polar solvent and non-polar solvent indicated that the surface energy of deposited fibers significantly increased by 41.9% compared with the untreated fibers. An electronic tensile tester of single-filament and a universal testing machine were utilized to measure the strength change of the fibers after modification and the interfacial adhesion between the fibers and the rubber matrix, respectively. The results showed that the tensile strength had not been obviously reduced, and the pull-out force and peeling strength of the fibers to the rubber increased by 46.3% and 56.5%, respectively.

Low-cost mussel inspired poly(Catechol/Polyamine) modified magnetic nanoparticles as a versatile platform for enhanced activity of immobilized enzyme

Owing to dopamine's excellent adhesion ability and easy modification, it has been widely applied for enzyme immobilization, while the high cost of dopamine and low activity recovery of immobilized enzyme highly impede large-scale application of immobilized enzyme. We herein developed a low-cost and ideal activity recovery enzyme immobilization strategy based on magnetic nanoparticles by replacing dopamine with cheap Catechol/tetraethylene pentamine (CPA) binary system and introducing spacer-arms. In brief, CPA was first polymerized and deposited on the surface of magnetic nanoparticles with a modified mussel-inspired method, and the generated poly(CPA) layer was further functionalized with ethylene glycol diglycidyl ether (EGDE) molecules as spacer-arms for enzyme immobilization. Subsequently, lipases as model enzymes were firmly immobilized on the surface of such amino-epoxy functionalized magnetic materials through ion exchange and covalent attachment with 180.6 mg/g support of loading capacity and 69.2% of activity recovery under the optimized conditions. Furthermore, the immobilized lipase exhibited the improved tolerance rang of pH, temperature and storage stability as well as excellent reusability. Most strikingly, the theoretical simulation and secondary structure analysis of immobilized lipase revealed that the biocompatible microenvironment and flexible tethering at interface could effectively improve performance of the immobilized enzyme and stability. Thus, this novel immobilized enzyme strategy will open up a new perspective for the development of enzyme immobilization and lower the cost of immobilized enzyme in large-scale industrial application.

Green synthesis of tannin-hexamethylendiamine based adsorbents for efficient removal of Cr(VI)

Newly developed adsorbents, poly(tannin-hexamethylendiamine) (PTHA), were fabricated by varying the mole ratio of tannin (TA) and hexamethylendiamine (HA) under one-pot reaction. The specific forming process of the adsorbent which had undergone the transition from hydrogen bonds to covalent bonds was subsequently explored. Based on the efficiency of Cr(VI) removal from aqueous solution over all prepared adsorbents, the PTHA-4 (mole ratio of TA/HA = 1:12.5) exhibited an excellent adsorption behavior. Adsorption experiments affected by contact time and ionic strength have been conducted successively by PTHA-4, and the equilibrium was reached at 24 h. The kinetic data revealed that the adsorption was good agreement with pseudo-second order model and needed to undergo the rate-controlling step. The maximum adsorption capacity was 283.29 mg/g at 30 °C, relying on the isothermal curve suitably described by Langmuir model. Furthermore, toxic Cr(VI) had been reduced to the low toxic Cr(III) during adsorption process. The structures and adsorption performance of adsorbent were confirmed by means of SEM, FT-IR, XPS etc. Thus, the cheap-sustainable adsorbents have a superior feature for Cr(VI)-wastewater purification in future.

Fabrication of free-standing membranes with tunable pore structures based on the combination of electrospinning and self-assembly of block copolymers

Polydopamine could improve interface performance of composite membranes with tunable structures which were developed by combining electrospinning and BCP self-assembly.