Hydrogels with wet adhesion are promising interfacial adhesive materials; however, their adhesion in water, oil, or organic solvents remains a major challenge. To address this, a pressure‐sensitive ...P(AAm‐co‐C18)/PTA‐Fe hydrogel is fabricated, which exhibits robust adhesion to various substrates in both aqueous solutions and oil environments. It is demonstrated that the key to wet adhesion under liquid conditions is the removal of the interfacial liquid, which can be achieved through rational molecular composition regulation. By complexing with hydrophilic polymer networks, phosphotungstic acid (PTA) is introduced into the hydrogel network as a physical cross‐linker and anchor point to improve the cohesion strength and drive the migration of polymer chains. The migration and rearrangement of hydrophilic and hydrophobic polymer chains on the hydrogel surface are induced by the electrostatic interactions of Fe3+, which create a surface with interfacial water‐ and oil‐removing properties. By co‐regulating the hydrophilic and hydrophobic polymer chains, the P(AAm‐co‐C18)/PTA‐Fe hydrogel is able to act as a pressure‐sensitive adhesive under water and oils with adhesion strength of 92.6 and 90.0 kPa, respectively. It is anticipated that this regulation strategy for polymer chains will promote the development of wet adhesion hydrogels, which can have a wide range of applications.
A pressure‐sensitive hydrogel exhibits robust adhesion in aqueous solution and oil environments by electrostatic‐induced hydrophilic and hydrophobic polymer chains migration and rearrangement, which realizes the removal of the interfacial liquid layer and the effective interfacial bonding during wet adhesion. This polymer‐chains‐regulated hydrogel provides a new strategy for adhesion in liquid environments, broadening the application scenarios of adhesives.
Loss factor tan δ determines the viscoelasticity of a material. Higher or lower loss factor tanδ (>1 or <1) suggests a viscous or elastic material. Most polymer pressure‐sensitive adhesives (PSAs) ...possess a limited operational temperature range (near room temperature), above which the PSAs trend to be more viscous (un‐crosslinked) or more elastic (crosslinked), and below which PSAs become more elastic. These properties are unfavorable for PSA operation. Herein, an underwater PSA possessing short hydrophobic side chains and weak hydrogen bond interactions are described. Proper modulus and stable loss factor close to 1 contributes to an efficient adhesion underwater over a temperature range of 0–100 °C. Moreover, by introducing Teflon particles, the adhesion can be operated under silicon oil from room temperature to 150 °C due to the formation of a drainage surface structure and its temperature insensitivity.
Adhesion operation under‐water/oil over a wide temperature range is achieved via a hydrophobic oil‐draining structure and temperature‐insensitive loss factor. A key point is to use methoxyethyl and thiourea groups that form hydrophobic and weak hydrogen‐bonding interactions, bringing tan δ close to 1. The other key point is to incorporate the Teflon micron particles to form an oil‐draining structure on adhesive surfaces.
Expanded polytetrafluoroethylene (ePTFE) has superior properties such as compression creep resistance and compression resilience, but it is difficult to bond with other materials due to its low ...surface energy, high crystallinity and highly symmetrical structure. In this paper, a new type of pressure‐sensitive adhesive is prepared from butyl acrylate, glycidyl methacrylate and unique pentafluorobenzyl acrylate, in which pentafluorophenyl group is introduced to provide steric hindrance to avoid clustering and increase the affinity with ePTFE simultaneously. The thermal stability of this pressure‐sensitive adhesive is approximately 250°C; the contact angle can reach 110.7°; the peel strength can reach 19 N/25 mm, comparable to literature values. The shear holding power at room temperature can be maintained over 100 h, and increases with the extension of immersion time in water, 5 times that of the literature report. This new adhesive can aptly solve the adhesion challenges with the use of ePTFE in complex environment.
The ever-increasing regulations within the adhesives industry and the continuous demand for more sustainability, have led to the development of environmentally more suitable alternatives to ...petroleum-based pressure-sensitive adhesives (PSAs). This review provides an overview of the current strategies and methods to develop sustainable, acrylic PSAs derived from renewable resources, such as vegetable oil, lignin, carbohydrates and terpenes. Herein, we emphasize some of the key concepts in the literature within the past decades, which paved the way to the current focus of improving the adhesive properties by employing the full array of natural building blocks. In this context, some recent strategies that give tailor-made adhesive properties to PSAs are also discussed, in view of the desired application. With this critical insight on the large set of research efforts in the context of biosourced acrylic PSAs, we aim to provide a guide for new researchers in this highly emerging field.
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Novel UV curable acrylic pressure-sensitive adhesives (PSAs) with exceptional flame retardancy and promising two-way shape memory effect have been developed using a commercial diethyl phosphoramidate ...as multifunctional tackifier for the first time. The abundant hydrogen bonds and high viscosity of the resultant networks contribute to the low temperature and repeatable adhesions. The PSA with 5 wt % tackifier exhibited the best overall adhesion at both 25 °C and 0 °C, especially with the relatively high peak adhesive stress and the highest work of adhesion. Owing to the synergistic effect with nitrogen containing acylate monomer, the 15 wt% diethyl phosphoramidate endowed the PSA sample with self-extinguishing ability. Moreover, the higher viscoelasticity makes the tackified PSAs with better two-way shape memory property. In particular, the elongation upon cooling and contraction upon heating are 57.2% and 55.9%, respectively.
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•A multifunctional tackifier for acrylic pressure-sensitive adhesives is reported.•The PSAs integrate UV curability, flame retardancy, and two-way shape memory effect.•A condensed phase flame retardant mechanism of phosphoramidate is proposed.•The higher viscoelasticity suggests better two-way shape memory property.•Two-way shape memory effect in cyclic freezing and thawing scenario is demonstrated.
An adhesive is a non-metallic substance used for the joining of two separate objects by applying it either on one side or both the sides of objects. One of the classifications of adhesives is based ...on the chemical nature, i.e. it can either be reactive or non-reactive, while the other segregates them depending upon the origin like natural or synthetic. The pressure-sensitive adhesives (PSAs) are one of the important classes following the mechanism of curing of the adhesive which do not undergo any chemical reaction or physical change during the adhesion process. PSAs are greatly replacing many conventional types of adhesive and are considered safe to use. The application of the hybrid polymers in the field of PSAs that consists of silane-curing organic compounds having wide formulation tolerance and outstanding mechanical properties is a major class in the upcoming PSA market. The present article discusses the various types of PSAs, their recent trends based on the various application properties with the structure–property relationship and their synthesis techniques.
Pressure‐sensitive adhesives (PSAs), which achieve instantaneous adhesion with the application of light pressure, are used in a large range of commodity applications. In this work, PSAs enriched with ...cellulose nanocrystals (CNCs) and stabilized with a reactive surfactant (Hitenol AR‐1025, AR) were synthesized via in situ emulsion polymerization. Incorporation of CNCs into AR‐stabilized PSAs lead to improvements of peel strength, shear strength, and loop tack with significant increases observed at a CNC concentration of 0.75 parts per hundred monomer (phm). A comparative investigation of PSAs stabilized with reactive (AR) and non‐reactive (sodium dodecyl sulfate) surfactant revealed that the enhanced performance can be attributed to the synergistic combination of CNCs and reactive surfactant, as only modest improvements can be attributed to surfactant type. In contrast to previous studies that report a trade‐off in adhesive properties, we present a well‐rounded PSA with exceptional peel strength, shear strength, and loop tack.
Acrylic pressure-sensitive adhesives (PSAs) are extensively used to fasten display layers. Although PSAs must show sufficient adhesion for application to existing displays, PSAs must utilize ...stretching and recovery to mitigate the effects of deformation for application to flexible displays. Therefore, in this study, an ultraviolet (UV)-patterned acrylic PSA was prepared by incorporating a region showing variable degrees of crosslinking achieved using a contrasting UV-patterned film. The gel fraction was measured to confirm the degree of crosslinking, and the adhesion was measured by peel strength, pull-off, and lap shear tests. Dynamic mechanical analysis (DMA) stress relaxation was used to measure the recovery. The highest gel fraction was obtained at a crosslinker content of 1 part per hundred resin (phr) and a UV dose of 1600 mJ/cm2. The low-crosslink-density area was optimized using the 50% gray patterned film. The acrylic PSA prepared with 0.001 phr of 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT), a light-emitting compound used to visualize the pattern formation, showed the clearest pattern. Although the adhesion of the UV-patterned acrylic PSA initially decreased, it gradually increased for the 2 mm pattern. However, the shear adhesion was maintained without appreciably changing. Although the acrylic PSA could not withstand certain deformation conditions during UV patterning, it was stretchable at a pattern size of 4 mm, and the recovery increased to approximately 60% at a pattern size of 2 mm. The results confirmed that the UV-patterned PSA is suitable for application to flexible displays.
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•UV-patterned PSA was prepared by incorporating variable crosslinking.•Gel fraction was measured to determine degree of crosslinking.•Adhesion was measured by peel strength, pull-off, and lap shear tests.•Optimal crosslinker content and UV dose were 1 phr and 1600 mJ/cm2, respectively.•UV-patterned PSA is suitable for application to flexible displays.
The practical application of lithium (Li) metal battery is impeded by the Li dendrite growth and unstable solid electrolyte interphase (SEI) layer. Herein, an ultra‐stretchable and ionic conducting ...chemically crosslinked pressure‐sensitive adhesive (cPSA) synthesized via the copolymerization of 2‐ethylhexyl acrylate and acrylic acid with poly(ethyleneglycol)dimethacrylate as crosslinker (short for 70cPSA), is developed as both artificial SEI layer and solid polymer electrolyte (SPE) for stable Li‐metal electrode, enabling all‐solid‐state Li metal batteries with excellent cycling performance. As an artificial SEI layer, the 70cPSA‐modified electrodes exhibit excellent electrochemical performance in Li|70cPSA@Cu half cells and 70cPSA@Li|70cPSA@Li symmetric cells. In full cells with LiFePO4 (LFP) as cathode, the 70cPSA@Li|LFP cell exhibits stable cycling performance over 250 cycles. Utilized as SPE, the all‐solid‐state Li|SPE|LFP cell delivers excellent cycling stability with a capacity retention of 86% over 500 cycles. With high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) as cathode, the Li|SPE|NMC811 cell exhibits a discharge capacity of 124.3 mAh g−1 with a capacity retention of 71% after 200 cycles. The rational design of PSAs and investigation of their dual role for stable and safe Li‐metal batteries may shed a light on adhesive polymers for battery applications.
An ultra‐stretchable and ionic conducting chemically crosslinked pressure‐sensitive adhesive is developed that serves a dual‐role as artificial solid electrolyte interface layer and solid polymer electrolyte. The integration of spontaneous adhesion, high extensibility, and homogenous ionic conducting channels to a single polymer matrix enables efficient regulation of Li+ transport and greatly improves dendrite resistance.
