Adhesive Polymer Research Articles

Repeatable adhesion of bio-based polymer derived from tetrafunctional epoxides and polyhydric carboxylic acid

Bio-based network polymers were synthesized by cross-linking diastereomeric tetrafunctional epoxides, tetra-trans-LO (1) and tetra-cis-LO (2), with polyhydric carboxylic acid in the presence and absence of a catalyst. The cross-linking ability of 1 was higher than that of 2 and afforded to higher polymer yields, thermal stability, and mechanical strength. Repeatable adhesion with a moderately high recovery strength was achieved using 1 and polyhydric carboxylic acid in the presence of Zn(acac)2.

Bioinspired superhydrophobic surfaces with silver and nitric oxide-releasing capabilities to prevent device-associated infections and thrombosis

Bacteria-associated infections and thrombus formation are the two major complications plaguing the application of blood-contacting medical devices. Therefore, functionalized surfaces and drug delivery for passive and active antifouling strategies have been employed. Herein, we report the novel integration of bio-inspired superhydrophobicity with nitric oxide release to obtain a functional polymeric material with anti-thrombogenic and antimicrobial characteristics. The nitric oxide release acts as an antimicrobial agent and platelet inhibitor, while the superhydrophobic components prevent non-specific biofouling. Widely used medical-grade silicone rubber (SR) substrates that are known to be susceptible to biofilm and thrombus formation were dip-coated with fluorinated silicon dioxide (SiO2) and silver (Ag) nanoparticles (NPs) using an adhesive polymer as a binder. Thereafter, the resulting superhydrophobic (SH) SR substrates were impregnated with S-nitroso-N-acetylpenicillamine (SNAP, an NO donor) to obtain a superhydrophobic, Ag-bound, NO-releasing (SH-SiAgNO) surface. The SH-SiAgNO surfaces had the lowest amount of viable adhered E. coli (> 99.9 % reduction), S. aureus (> 99.8 % reduction), and platelets (> 96.1 % reduction) as compared to controls while demonstrating no cytotoxic effects on fibroblast cells. Thus, this innovative approach is the first to combine SNAP with an antifouling SH polymer surface that possesses the immense potential to minimize medical device-associated complications without using conventional systemic anticoagulation and antibiotic treatments.

Model Based on the River Meander Curve for Simulating the Adhesion of Cross-Linked Polymers to Rough Surfaces

Model Based on the River Meander Curve for Simulating the Adhesion of Cross-Linked Polymers to Rough Surfaces

Direct‐Current Triboelectric Nanogenerators Based on Contact–Separation Mode and Conductive–Adhesive Interface

AbstractDirect‐current triboelectric nanogenerators (DC‐TENGs), which are used in smart electronics and energy storage, have attracted tremendous scientific interest owing to their rectification‐free and high energy utilization efficiency. In this study, the authors propose a new type of DC‐TENG that operates in the contact–separation mode with a unique adhesive–conductive interface for the first time. The results demonstrate that the TENG output increases with increasing interfacial adhesion strength; both the adhesive polymer and conductive tribomaterial are essential factors for the DC output. The proposed mechanism is based on mechanoion generation via covalent bond cleavage during material transfer and the charge leakage effect. Specifically, the DC‐TENG exhibits unique frequency‐decreasing and force‐enhancing output characteristics. It can directly drive LEDs or charge commercial capacitors. By integrating a stretchable electrode, an adhesive‐based single‐electrode TENG can be used as a strain sensor or material detector. This work presents a new type of DC‐TENG with a conventional two‐electrode configuration and provides new perspectives on the fundamental research and applications of DC‐TENGs.

Neutrophils bearing adhesive polymer micropatches as a drug-free cancer immunotherapy.

Tumour-associated neutrophils can exert antitumour effects but can also assume a pro-tumoural phenotype in the immunosuppressive tumour microenvironment. Here we show that neutrophils can be polarized towards the antitumour phenotype by discoidal polymer micrometric 'patches' that adhere to the neutrophils' surfaces without being internalized. Intravenously administered micropatch-loaded neutrophils accumulated in the spleen and in tumour-draining lymph nodes, and activated splenic natural killer cells and T cells, increasing the accumulation of dendritic cells and natural killer cells. In mice bearing subcutaneous B16F10 tumours or orthotopic 4T1 tumours, intravenous injection of the micropatch-loaded neutrophils led to robust systemic immune responses, a reduction in tumour burden and improvements in survival rates. Micropatch-activated neutrophils combined with the checkpoint inhibitor anti-cytotoxic T-lymphocyte-associated protein 4 resulted in strong inhibition of the growth of B16F10 tumours, and in complete tumour regression in one-third of the treated mice. Micropatch-loaded neutrophils could provide a potent, scalable and drug-free approach for neutrophil-based cancer immunotherapy.

Viscoelasticity, stiffness gradient and their effects on adhesion of an epoxy shape memory polymer

The shape memory polymer based adhesives have demonstrated excellent programmable switchable adhesion, in which the material properties play an important role. Here, the viscoelasticity, stiffness gradient, and their effects on adhesion of an epoxy shape memory polymer (ESMP) were studied. The ESMP sample and polydimethylsiloxane control sample were fabricated firstly by mold casting and curing techniques. The sample was fixed on an electric heating plate with double-sided tape to conduct the adhesion measurements against a hemispherical glass indenter under different temperature and displacement conditions by using an adhesion tester and the temperature measurements on the double-sided tape and ESMP sample surfaces by using a digital thermodetector. Based on the measured force–displacement–time data, the hysteresis behavior and internal dissipation were evaluated; the peak force relaxation was studied; the reduced modulus was calculated and the stiffness gradient features were evaluated. The results show that the ESMP sample exhibits strong viscoelasticity and significantly enhanced adhesion that strongly depends on the compressive displacement in the glass-rubber transition zone near it is glass transition temperature ( Tg ), while weaker viscoelasticity and lower adhesion in the soft rubbery state. The reduced modulus of the ESMP sample obviously decreases with the increasing compressive displacement at a preset temperature below 70 °C. It is found that there exists a linear relation between the pull-off force, effective work of adhesion, reduced modulus, and contact area. This study helps deeply understand the material properties and adhesion mechanism of the ESMP, which can guide the design of switchable adhesives.

Fully Printable and Reconfigurable Hufu-type Electroluminescent Devices for Visualized Encryption.

Hufu, serving as evidence of imperial authorization in ancient China, comprises two parts in the form of tiger-shaped tallies that only become effective when matched. Drawing inspiration from the concept of Hufu, a reconfigurable electroluminescent (EL) device is designed by separating conventional integral devices into two parts that contain the EL layer (part A) and the transparent electrode (part B), respectively. The key to realizing such strategy is employing an adhesive and stretchable polymer gel composite as the transparent electrodes for the EL devices. The polymer gel composite facilitates robust yet reversible contact between the EL layer and transparent electrode, enabling high-performance and stretchable EL devices that can be readily disassembled and reassembled: the EL devices can maintain ≈81% of their initial luminance after 1000 times of repeated disassembly and reassembly. Moreover, the precursor ink of the polymer gel composite is compatible with a wide variety of coating and printing technologies, such as spin-coating, inkjet printing, dispensing, and brush painting. Importantly, the reconfigurable feature of the devices opens up a new path to encryption display systems, and as a proof-of-concept, EL encrypted password, and content-changeable digital clock are demonstrated.

Vacuum‐free lamination via controlled polymer adhesion for selective photogeneration and photodetection

AbstractThis study attempts to develop a reproducible thin‐film formation technique called vacuum‐free (VF) lamination, which transfers thin films using elastomeric polymer‐based laminating mediators. Precisely, by controlling the interface characteristics of the mediator based on the work of adhesion, VF lamination is successfully performed for various thicknesses (from 20 to 240 nm) of a conjugated photoactive material composed of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐bʹ]dithiophene))‐alt‐(5,5‐(1ʹ,3ʹ‐di‐2‐thienyl‐5ʹ,7ʹ‐bis(2‐ethylhexyl)benzo[1ʹ,2ʹ‐c:4ʹ,5ʹ‐cʹ]dithiophene‐4,8‐dione)] (a polymer donor) and 2,2ʹ‐((2Z,2ʹZ)‐((12,13‐bis(2‐butyloctyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2ʹʹ,3ʹʹ:4ʹ,5ʹ]thieno[2ʹ,3ʹ:4,5]pyrrolo[3,2‐g]thieno[2ʹ,3ʹ:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (a nonfullerene acceptor). Interestingly, the organic photovoltaic and photodetecting applications, prepared by the VF lamination process, showed superior performance compared to those of devices prepared by conventional spin‐coating. This is due to the overturned surface morphology, which led to enhanced charge transport ability and blocking of the externally injected charge. Thus, the reproducible VF lamination process, exploiting an adhesion‐based elastomeric polymer mediator, is a promising thin‐film formation technique for developing efficient next‐generation organic optoelectronic materials consistent with the solution process.

New twisted van der Waals fabrication method based on strongly adhesive polymer

Observations of emergent quantum phases in twisted bilayer graphene prompted a flurry of activities in van der Waals (vdW) materials beyond graphene. Most current twisted experiments use a so-called tear-and-stack method using a polymer called polypropylene carbonate (PPC). However, despite the clear advantage of the current PPC tear-and-stack method, there are also technical limitations, mainly a limited number of vdW materials that can be studied using this PPC-based method. This technical bottleneck has been preventing further development of the exciting field beyond a few available vdW samples. To overcome this challenge and facilitate future expansion, we developed a new tear-and-stack method using a strongly adhesive polycaprolactone. With similar angular accuracy, our technology allows fabrication without a capping layer, facilitating surface analysis and ensuring inherently clean interfaces and low operating temperatures. More importantly, it can be applied to many other vdW materials that have remained inaccessible with the PPC-based method. We present our results on twist homostructures made with a wide choice of vdW materials—from two well-studied vdW materials (graphene and MoS2) to the first-ever demonstrations of other vdW materials (NbSe2, NiPS3, and Fe3GeTe2). Therefore, our new technique will help expand moiré physics beyond few selected vdW materials and open up more exciting developments.

Investigation of the structural performance of continuous adhesive glass-metal connections using structural silicone and hybrid polymer adhesives

Current design standards and technical guidelines regarding structural adhesive glass-metal connections demonstrate only a narrow applicability window, resulting in constraints regarding the geometry of the adhesive joint, e.g. width-to-thickness ratio, that are tight as well. Therefore, research is conducted considering continuous adhesive glass-metal connections with joint geometries beyond the design framework of existing technical design guidelines. The structural silicones DowSil™ 993 and Sikasil® SG-500, and the hybrid polymer adhesive Soudaseal 2K are used during the experiments as such types of adhesives have already demonstrated their durability over the last 50 years in structural sealant glazing systems. This paper reports on the mechanical performance of continuous adhesive glass-metal connections with varying width-to-thickness ratios. Numerical models are validated based on experimental data, which are then used for parametric studies. From the generated data basic relationships between joint stiffness and geometrical parameters are derived, such as width-to-thickness ratio. A mechanical model of continuous adhesive glass-metal joints as proposed in literature is used to perform analytical calculations to predict the deformations and stresses in the adhesive layer, which shows good agreement with the numerical results. The existing mechanical model predicts the stiffness of these continuous connections as function of geometrical and material parameters (here for DowSil™ 993) significantly accurate. Therefore, this research can serve as a basis for the expansion of current design methods to adhesive joint geometries outside their current framework.

Degradation of Various Organic Coatings via UV-Generated Sulfate Radicals.

Degradation of organic coatings is essential for recycling valuable substrates. Despite the development of strategies for this purpose, the resulting degradations are typically constrained by the composition of the coating. This paper presents a simple strategy utilizing radicals induced by UV for the degradation of diverse organic coatings. The sulfate radicals, generated from UV-exposed ammonium persulfates, induce the degradation of various organic coatings, including layer-by-layer assembled coating composed of alginate and chitosan polymers as well as polydopamine coating. This strategy also facilitates the separation of two adhered substrates by degrading the adhesive polymer layer positioned between them. This novel approach enables the complete degradation of various organic coatings in aqueous conditions without imposing restrictions on their composition, leading to the recovery of the original surface properties of the substrate.

Adhesion of polymer and cementitious overlays to ultra high performance concrete substrate

Overlays are used in bridges atop of ultra high performance (UHPC) components despite the lack of data regarding overlay-UHPC bond performance. To address this knowledge gap, this study evaluated the adhesion of polyester polymer concrete (PPC), latex modified concrete (LMC) and modified concrete type D (MCD) overlays bonded to UHPC substrate via the bond pull-off test method. The test variables included coring depth into the UHPC, overlay age, and surface preparation method (grinding and sandblasting, surface retarder treatment, and hydrodemolition). PPC exhibited superior bond performance, followed by LMC and MCD. The overall better performance of PPC and LMC over MCD was accredited to enhanced chemical adhesion enabled by polyester and latex, respectively. Surfaces prepared via surface retarder and hydrodemolition exposed fibers in UHPC which resulted in fiber-bridging effect across the interface.

Multifunctional Acrylic Polymers with Enhanced Adhesive Property Serving as Excellent Edge Encapsulant for Stable Optoelectronic Devices.

Pendant groups in acrylic adhesive polymers (Ads) have a profound influence on adhesive and cohesive properties and additionally on encapsulant application. However, a systematic investigation to assess the impact of the pendant groups' length and bulkiness is rare, and there is not even a single report on applying Ads as interfacial adhesion promotors and encapsulation materials simultaneously. Herein, we have developed a series of multifunctional methacrylic polymers, namely, R-co-Ads, with varying pendant length and bulkiness (R = methyl (C1), ethyl (C2), propyl (C3), butyl (C4), pentyl (C5), hexyl (C6), isobutyl (iC4), and 2-ethylhexyl (2EH)). The adhesion-related experimental results reveal that R-co-Ads have high transparency, strong adhesion strength to the various contact surfaces, and a fast cure speed. In particular, C1-co-Ad shows a superior adhesion performance with an improved cross-cut index of 4B and a shear bonding strength of 1.56 MPa. We also have adopted C1-co-Ad for encapsulation of various emerging optoelectronic applications (e.g., perovskite solar cell-, charge transport-, and conductivity-related characteristics), demonstrating its excellent edge encapsulant served to improve the device stability against ambient air conditions. Our study establishes the structure-adhesion-surface relationships, advancing the better design of adhesives and encapsulants for various research fields.

Salicylhydroxamic acid containing structural adhesive.

The feasibility of utilizing salicylhydroxamic acid (SHAM) as a new adhesive molecule for designing structural adhesives is investigated in this study. SHAM-containing polymers were prepared with a hydroxyethyl methacrylate (HEMA) or methoxyethyl acrylate (MEA) backbone and mixed with polyvinylidene fluoride (PVDF). PVDF was included to increase the cohesive property of the adhesive through hydrogen bond (H-bond) formation with the adhesive polymers. SHAM-containing adhesive demonstrated lap shear adhesion strength (S adh) greater than 0.9 MPa to glass, metal, and polymeric surfaces. Adhesive formulations with elevated SHAM-content also demonstrated increased adhesive properties with S adh values reaching as high as 4.8 MPa. Due to the physically crosslinked nature of these adhesives, formulations with extensive H-bonding resulted in strong adhesion and stability. HEMA consists of a terminal hydroxyl group with both H-bond donor and acceptor, which enabled HEMA-containing adhesives to demonstrate strong adhesion even without PVDF. On the other hand, MEA contains a methoxy group that lacks H-bond donors for forming H-bonding and MEA-containing adhesives required PVDF to provide H-bond acceptors to increase its cohesive property. An aging study was performed on the bonded joints. While the adhesive joints did not demonstrate any reduction in S adh values over 25 days when incubated in a dry condition, S adh values decreased by 80% over 48 h when incubated in water. This is potentially due to the hydrophilic and physically crosslinked nature of the adhesive. Nevertheless, the SHAM-containing adhesive outperformed a catechol-containing adhesive and epoxy glue and is a promising new adhesive molecule for designing structural adhesives.

Metal-phenolic network composites: from fundamentals to applications.

Composites with tailored compositions and functions have attracted widespread scientific and industrial interest. Metal-phenolic networks (MPNs), which are composed of phenolic ligands and metal ions, are amorphous adhesive coordination polymers that have been combined with various functional components to create composites with potential in chemistry, biology, and materials science. This review aims to provide a comprehensive summary of both fundamental knowledge and advancements in the field of MPN composites. The advantages of amorphous MPNs, over crystalline metal-organic frameworks, for fabricating composites are highlighted, including their mild synthesis, diverse interactions, and numerous intrinsic functionalities. The formation mechanisms and state-of-the-art synthesis strategies of MPN composites are summarized to guide their rational design. Subsequently, a detailed overview of the chemical interactions and structure-property relationships of composites based on different functional components (e.g., small molecules, polymers, biomacromolecules) is provided. Finally, perspectives are offered on the current challenges and future directions of MPN composites. This tutorial review is expected to serve as a fundamental guide for researchers in the field of metal-organic materials and to provide insights and avenues to enhance the performance of existing functional materials in applications across diverse fields.

Emergence of long-range attractive interactions between colloidal particles during curing of dispersion media.

Compared to traditional drying methods, curing processes result in lower emissions of volatile organic compounds and reduced energy consumption. Consequently, curing processes are widely used in the manufacturing of various polymer products, including inks, coatings, composites, and adhesives. In recent years, the functionality of these polymer products has been enhanced by incorporating colloids with antiviral and conductive properties. Despite the significant influence of colloidal arrangement on physical properties, the kinetics of colloidal particles during curing remains poorly understood. To explore the effective interactions between colloidal particles during curing, we investigated the dynamics of soft particles within dispersing media using molecular dynamics simulations. The likelihood of particle aggregation during curing significantly surpasses that of random contact. Our calculations reveal an effective potential, indicating a long-range attractive interaction between the large particles. This attraction results from the heterogeneity in the crosslink network of the dispersing media, distinguishing it from the classical depletion force. Since the structure of particle aggregation could be controlled by the interplay between curing rate and particle diffusion, our findings offer promising prospects for advancing the manufacturing processes of increasingly functional polymeric products.

Wetting-enhanced adhesion of photo-polymerized supramolecular adhesives for both smooth and rough surfaces.

Efficient interactions between an adhesive and a substrate surface at the molecular level are the basis for the formation of robust adhesion, which substantially relies on interfacial wetting. However, strong adhesives usually improve cohesion but compromise interfacial properties. Herein, we have reported a kind of robust supramolecular adhesive based on the outstanding mobility and interfacial wettability of adhesive precursors. In situ fast photopolymerization endows supramolecular adhesives with more outstanding adhesion for both smooth and rough surfaces in air and underwater in contrast to their counterparts from thermal polymerization. In addition to their low viscosity and high monomer concentration, supramolecular adhesive precursors without any organic solvents possess well-defined hydrogen bonding interactions. These superior properties consistently contribute to the wetting of the substrate and the formation of adhesive polymers with high molecular weights. This work highlights that enhancing interfacial wetting between an adhesive and a substrate is a promising route to achieving robust adhesion.

Synthesis and spectroscopic study of adhesive polymer materials based on urea-formaldehyde and isoamyl alcohol

The synthesis and identification of adhesive polymer materials based on urea-formaldehyde and isoamyl alcohol represent a crucial area of research in the field of materials science and industrial applications. This theme explores the advancements, challenges, and potential applications of these adhesive formulations, leveraging techniques such as FT-IR spectra, UV-Vis spectra, and Density Functional Theory (DFT) calculations. The FT-IR and UV-Vis spectra were recorded in the ranges of 4000-600 cm−1 and 200-1100 nm, respectively, and were compared to the spectra that were theoretically obtained. The compound was optimized using the DFT/B3LYp/6–31G(d) basis set in solvents of ethanol.

Sustainable design of high-performance multifunctional carbon electrodes by one-step laser carbonization for supercapacitors and dopamine sensors.

Laser carbonization is a rapid method to produce functional carbon materials for electronic devices, but many typical carbon precursors are not sustainable and/or require extensive processing for electrochemical applications. Here, a sustainable concept to fabricate laser patterned carbon (LP-C) electrodes from biomass-derived sodium lignosulfonate, an abundant waste product from the paper industry is presented. By introducing an adhesive polymer interlayer between the sodium lignosulfonate and a graphite foil current collector, stable, abrasion-resistant LP-C electrodes can be fabricated in a single laser irradiation step. The electrode properties can be systematically tuned by controlling the laser processing parameters. The optimized LP-C electrodes demonstrate a promising performance in supercapacitors and electrochemical dopamine biosensors. They exhibit high areal capacitances of 38.9 mF cm-2 in 1 M H2SO4 and high energy and power densities of 4.3 μW h cm-2 and 16 mW cm-2 in 17 M NaClO4, showing the best performance among biomass-derived LP-C materials reported so far. After 20 000 charge/discharge cycles, they retain a high capacitance of 81%. Dopamine was linearly detected in the range of 0.1 to 20 μM with an extrapolated limit of detection of 0.5 μM (S/N = 3) and high sensitivity (13.38 μA μM-1 cm-2), demonstrating better performance than previously reported biomass-derived LP-C dopamine sensors.

Geopolymer adhesive for sustainable NSM CFRP strengthening of RC structures

Carbon fiber reinforced polymer (CFRP) composites are known to be a very effective materials for strengthening and rehabilitation of reinforced concrete (RC) structures. Near surface mounted (NSM) technique, has been used as an effective method for this purpose, over the past two decades. The conventional technique benefits from the superb properties of polymeric adhesives like epoxy resins, to ensure a successful transfer of stresses between the CFRP and concrete substrate. However, the vulnerability of polymeric matrices to high temperatures motivated researchers to focus on developing cement-based adhesives for NSM CFRP systems for special applications where fire safety is an issue. Recently, efforts led to promising outcomes for the future of these novel systems. This upgrade not only fulfills the fire safety measures but also is necessary from the environmental point of view, due to the pollution and health problems associated with the usage of epoxy resins as conventional adhesives for FRP systems. While improvements occurred in the bond performance of the NSM CFRP systems with cement-based adhesives, using innovative sand-coated CFRP strips, the alternative sustainable approaches could be also investigated. This paper is dedicated to assessing the adoption of a geopolymer adhesive, to serve as a matrix for NSM strengthening techniques, using special sand-coated CFRP strips. Bond tests have been performed in ambient and thermo-mechanical conditions, and results showed promising performance of adoption of geopolymer in this technique. Also, a brief analysis of the environmental impact of using geopolymer as an alternative sustainable matrix is discussed, compared with epoxy resin and cement-based adhesive as its competitors, for eco-friendly strengthening systems for RC structures.