Adhesive Polymer Research Articles

Super‐Tough and Fast Adhesion of Soft Elastomer Based on Strong Noncovalent Interaction in Diverse Environments

AbstractSoft polymer adhesives to achieve high adhesion energy on both dry and wet surfaces in a simple and universal way is a significant challenge. Here, this work introduces an inherently adhesive and transparent elastomer that exhibits in situ adhesion capabilities across a variety of surfaces. These surfaces include, but are not limited to, glass, steel, aluminum, polyethylene terephthalate (PET), and poly(tetrafluoroethylene) (PTFE) sheets, with the remarkable feature of requiring no chemical reaction for adhesion. The elastomer adhesive achieves a super‐high adhesion force above 3000 N m−1 within 10 min, far superior to previously reported intrinsically adhesive polymers. The strong adhesion derives from the increase in hydrogen bonding density between the adhesive elastomer and adherend, high mobility of polymer chains, and matrix hysteresis during interfacial separation. Moreover, the noncovalent interactions can weaken at low temperatures, allowing the intrinsically adhesive elastomer to be easily removed when frozen. The development of intrinsically adhesive and transparent elastomer with super‐high adhesion force on both dry and wet surfaces provides a meaningful way for a wide range of applications.

Influence of Chemical Pretreatment on the Mechanical, Chemical, and Interfacial Properties of 3D-Printed, Rice-Husk-Fiber-Reinforced Composites

This article explores using biomass, namely rice husks, as a reinforcement material in thermoplastic copolyester (TPC) composites. Rice husks were subjected to three chemical pretreatments: single-stage sulfuric acid hydrolysis, first-stage sulfuric acid hydrolysis followed by a second-stage methanesulfonic acid (MSA) treatment, and first-stage sulfuric acid hydrolysis followed by a second-stage sodium hydroxide alkali treatment. We studied the effects of these treatments on the rheological, thermal, interfacial, and mechanical properties of composites. The fibers were mixed with polymers at high shear rates and temperatures, and 3D-printed filaments were produced using a desktop 3D printer. The printed parts were analyzed using tensile tests, torque and viscosity measurements, and thermogravimetric analysis to obtain their mechanical, rheological, and thermal properties. SEM imaging was performed to understand the fiber–polymer interface and how it affects the other properties. The results showed that first-stage sulfuric acid hydrolysis followed by a second-stage pretreatment of the fibers with MSA showed better fiber–polymer adhesion and a 20.4% increase in stress at 5% strain, a 30% increase in stress at 50% strain, and a 22.6% increase in the elastic modulus as compared to untreated rice husk composites. These findings indicate that readily available and inexpensive rice husks have significant potential for use in natural fiber-reinforced composites when pretreated using dilute sulfuric acid followed by methane sulfonic acid hydrolysis.

Wettability, Adsorption and Adhesion in Polymer (PMMA)-Commercially Available Mouthrinse System.

The study concerns the evaluation of the physicochemical and thermo-adsorptive surface properties of six commercially available mouthrinses, particularly surface tension, surface activity, partitioning coefficient, critical micellar concentration, Gibbs excesses at interfaces, surface entropy, and enthalpy. The aim was to quantify their effect on the adhesion and wettability of a model poly(methyl methacrylate) (PMMA) polymer. The adsorptive and thermal surface characteristics were derived from surface tension (γLV) vs. concentration and temperature dependences. Polymer surface wettability was characterized by the contact angle hysteresis (CAH) formalism, using the measurable advancing ΘA and receding ΘR dynamic contact angles and γLV as the input data. Further, wettability parameters: Young static angle (Θ), film pressure (Π), surface free energy (γSV) with its dispersive and polar components, work of adhesion (WA), and adhesional tension (γLV cosΘA) were considered as interfacial interaction indicators. The mouthrinse effect demonstrated the parameter's evolution in reference to the PMMA/pure water case: Θ, ΘA and ΘR↓, CAH↑, Π↓, WA↓, γSV↓, and γLVcosΘA↑. Furthermore, the variations of the surface excess ratio pointed to the formation of multilayered structures of surfactants composing the mouthrinse mixtures considered. The contact angle data allowed for the penetration coefficient and the Marangoni temperature gradient-driven liquid flow speed to be estimated.

Formulation and Evaluation of Mucoadhesive Beads of Dexamethasone

The goal of the current study was to formulate and evaluate mucoadhesive Dexamethasone beads to significantly lengthen the duration of the drug's stay in the GI system to treat Crohn’s disease. Dexamethasone is a corticosteroid that acts as an anti-rheumatic and anti-inflammatory. To decrease the dosage frequency Dexamethasone adhesive beads were formulated for Intimate contact with the underlying absorption surface is made possible by a prolonged stay at the location, which enhances the drug's therapeutic effectiveness. In the current study, calcium chloride and aluminium chloride were utilised as cross-linking agents to create Dexamethasone mucoadhesive beads employing adhesive polymers like sodium alginate, HPMC, and Eudragit L-100. The prepared beads' entrapment efficiencies ranged from 57.15 to 99.16%. Regarding entrapment effectiveness, particle size, surface properties, and in-vitro drug release experiments, the impact of bioadhesive polymers and cross-linking ions was assessed. The MPS-7 delayed the drug's release for 12 hours, which may be related to the cross-linking agent aluminium chloride. According to drug release kinetics, all of the formulations were more linear concerning zero order (r2=0.99) than concerning first order (r2=0.751 to 0.828). Super Case 2 Transport was discovered to be the precise release mechanism.

Robust, high-temperature and solvent tolerant, yet detachable polyimide adhesives enabled by dynamic boroxines

Detachable polymeric adhesives (DPAs) usually exhibit weak environmental reliability due to the intrinsic reversible network. Herein, such problem is solved by incorporating dynamic covalent boroxine bonds into high performance engineering polyimide (PI) network as crosslinkers. We demonstrate the boroxine crosslinked PI DPAs (denoted as PI-B3O3 DPAs) with simultaneously robust tensile strength (111.3 MPa), high interfacial bonding strength (26.0 MPa), and extremely environmental reliability including high-temperature tolerance (5% weight loss of ∼541.6 °C, adhesion strength after pretreating of 25.8 MPa at 300 °C, 22.6 MPa at 350 °C, and 18.3 MPa at 400 °C) and solvent stability (10 different solvents including acids, bases and organic solvents). Moreover, the PI-B3O3 DPAs can be further detached and recycled with the help of specific mixture solvent. The high tensile strength and extremely environmental tolerance are enabled by the rigid PI main chain and high bond energy of boroxines. Besides, the boroxine crosslinkers in PI-B3O3 network can help to balance its cohesion energy and interfacial adhesion energy, which guarantees its robust initial bonding strength in DPAs. At Last, due to the high reversibility of boroxines, the PI-B3O3 DPAs can be conveniently detached and recycled in the presence of specific mixture solvent.

Characterization and Selection of Tailorable Heat Triggered Epoxy Shape Memory Polymers for Epoxy Debondable Adhesives

AbstractThe increasing concern for environmental and economic sustainability has resulted in a growing interest in recycling the hybrid structures used in modern industries. To address the challenge of easy separation without damaging the substrates, a debondable‐adhesive incorporating shape memory polymer (SMP) filler is proposed. This study synthesizes seven types of epoxy SMPs at different stoichiometric ratios of the same chemicals. The thermomechanical, mechanical, and recovery characteristics of the SMPs are evaluated, and the most suitable candidate for debondable‐adhesive application is selected based on the selection criteria of SMP for embedding in the debondable adhesive. The results of this study offer valuable insights into the potential SMPs which can be incorporated in debondable adhesives used in modern industries.

Mussel-inspired hydrogels with UCST for temperature-controlled reversible adhesion

Achieving on-demand adhesion on different surfaces remains an adaunting challenge for polymer adhesives. Herein, we report a temperature-controlled adhesion strategy of hydrogels based on the reversible exposure and shielding of adhesive promoters regulated by microphase separation. The hydrogels are constructed by the physical crosslinking (hydrogen bonding and ion interaction) of a ternary random copolymer (PQAM) derived from the copolymerization of catechol containing quaternary ammonium salt monomer (QCA), acrylic acid (AA), and acrylamide (AAm). The physically crosslinked polymer networks can effectively toughen the hydrogels, resulting in tensile fracture strength, elongation, and energy up to 43.3 kPa, 1223%, and 9.5 kJ/m2, respectively. PQAM hydrogels exhibit upper critical solution temperature (UCST) behavior, and the transition temperature can be easily adjusted from 42.1 to 49.0 °C by changing the content of PQCA. PQAM hydrogels are non-transparent and non-adhesive at temperatures below UCST, while become transparent and highly adhesive at temperatures above UCST. By simply controlling the temperature, PQAM hydrogels can repeatedly attach to and detach from various substrates (including glass, plastics, ceramic, rock, wood, and metal) with an optimal adhesion strength up to 35.5 kPa. The strategy of hiding adhesive promoters may be interesting in the design of smart adhesives.

Comparison of adsorption ability of PAM, APAM and CPAM on Sodium-Montmorllonite surface: A molecular dynamics study

Swelling of clay minerals caused by the adsorption of water is one of the main problems encountered in oil well drilling industry during the operations of drilling with water-based fluids. Different types of chemicals can be used as inhibitor to solve the hydration of clay minerals in drilling fluids operations. So, the adsorption process of novel polymer inhibitor remained as well a complex surface phenomenon to understand. Recently, the polymer adhesion mechanism and the development of novel polymer inhibitors that can impart improved adhesion characteristics have become ultimately important to the drilling process. In this research, molecular dynamics simulations are applied to quantify and compare the adsorption density of PAM (Nonionic Polyacrylamide), APAM (Anionic Polyacrylamide) and CPAM (Cationic Polyacrylamide) on Sodium Montmorllonite (Na-MMT) Surface. And also to analyze the hydration inhibition effectiveness for solving shale swelling problem while drilling well. This work mainly explained and summarized the parameters which achieve directly the adsorption mechanism and affect the inhibition process. Including the adsorption characteristics of PAM, APAM and CPAM. The simulation results show that PAM and APAM molecules have low adsorption density on Na-MMT surface compared to CPAM molecules. PAM and APAM molecules interact more through h-bonding with their own molecules leading to a weak interaction with Na-MMT particles. CPAM molecules provide high mobility and have good attraction with Na-MMT particles through electrostatic forces, Van der Waals forces and hydrogen bonding. APAM exhibit high energy, as the distance between its molecules and MMT increase, due to high electrostatic repulsion caused by the negative charge. The adhesion of CPAM molecules affects the inhibition of Na-MMT surface hydration more than PAM and APAM.

Contact Electrification at Adhesive Interface: Boosting Charge Transfer for High‐Performance Triboelectric Nanogenerators

AbstractCharge transfer, a decisive feature for surface charge density in triboelectric nanogenerators (TENGs), differs in quantity and species at different contact interfaces. Regarded as the main electrification mechanism, electron transfer has been extensively investigated in constructing high‐performance tribo‐materials and TENGs, in which material transfer has been always neglected. Here, it is demonstrated that material transfer is a crucial electrification mechanism for adhesive polymers in contact electrification, and plays a dominant role in boosting charge transfer and TENG performance. Specifically, as a new strategy for utilizing the adhesion capability, this study introduces the stabilized poly(thioctic acid) adhesives as tribo‐materials to maximize contact electrification. With material transfer at the adhesive interface, abundant mechanoions are generated through covalent bond cleavage and higher charge density is obtained from the triboelectric pairs with larger interfacial adhesion force. Under a gentle triggering condition (5 N, 1 Hz), the TENG can achieve a high charge density of 14.65 nC∙cm−2, with a maximum output power density of 10 W∙m−2. Furthermore, the TENG exhibits unique frequency‐insensitive, pressure‐ and temperature‐enhanced output characteristics. This study provides new insight into constructing high‐performance TENGs using adhesives and highlights the indispensable role of material transfer in polymer contact electrification.

Assessing the effects of critical parameters in standoff bonding

In this contribution we present the effect of several parameters that are critical for bonding standoffs onto the surface of spacecrafts’ panels with polymeric adhesives. Standoffs are an integral part of the thermal management of space satellites since they ensure that the MLI blankets are mounted and maintained in the correct position during the whole mission duration, including launch. In the recent years, there have been several de-bonding problems during qualification phases, leading to long and costly delays, oftentimes caused from poor design and preparation[1]. For these reasons, we have performed a study of the bond strength of Torlon® 5030 rods bonded over sandwich panels made of an aluminium honeycomb core and CFRP skins. The bond strength was determined by mechanical tests, conducted in tensile and shear modes, both prior and after thermal cycling. Thermal analysis was also performed on the main components under study. The study consists on the following steps: first, different surface treatments of the CFRP skins have been investigated: (i) bonding standoffs with the surface as manufactured, (ii) cleaned with a solvent and (iii) mechanically sanded before cleaning. The best performing treatment was selected and used systematically in the rest of the study. Afterward, different types of adhesives (epoxy, graphene nano-enabled epoxy, polyurethane) and bond-line thicknesses were studied. The findings of this study can help to steer the industry towards better practices regarding the standoff bonding. This will improve the integrity of future space missions.

Composite Fibrin/Carbon Microfiber Implants for Bridging Spinal Cord Injury: A Translational Approach in Pigs.

Biomaterials may enhance neural repair after spinal cord injury (SCI) and testing their functionality in large animals is essential to achieve successful clinical translation. This work developed a porcine contusion/compression SCI model to investigate the consequences of myelotomy and implantation of fibrin gel containing biofunctionalized carbon microfibers (MFs). Fourteen pigs were distributed in SCI, SCI/myelotomy, and SCI/myelotomy/implant groups. An automated device was used for SCI. A dorsal myelotomy was performed on the lesion site at 1 day post-injury for removing cloths and devitalized tissue. Bundles of MFs coated with a conducting polymer and cell adhesion molecules were embedded in fibrin gel and used to bridge the spinal cord cavity. Reproducible lesions of about 1 cm in length were obtained. Myelotomy and lesion debridement caused no further neural damage compared to SCI alone but had little positive effect on neural regrowth. The MFs/fibrin gel implant facilitated axonal sprouting, elongation, and alignment within the lesion. However, the implant also increased lesion volume and was ineffective in preventing fibrosis, thus precluding functional neural regeneration. Our results indicate that myelotomy and lesion debridement can be advantageously used for implanting MF-based scaffolds. However, the implants need refinement and pharmaceuticals will be necessary to limit scarring.

Low-temperature self-healing polyurethane adhesives via dual synergetic crosslinking strategy

Abstract Damage to polymer adhesives is one of the most common reasons for structural integrity damage of composite solid propellants. The introduction of self-repairing technology into the adhesive is expected to solve this problem. However, at low temperatures, the self-repairing and mechanical properties of the materials are greatly impaired, thereby limiting the application of self-repairing adhesives in composite solid propellants. In this study, based on the dual synergistic crosslinking strategy, a polyurethane adhesive exhibiting excellent self-healing and mechanical properties at low temperatures was successfully prepared. The adhesive exhibited high self-repairing efficiency and ultra-long elongation at break at low temperatures. Specifically, at a low temperature of −40°C, the self-repair efficiency was over 70% and the elongation at break was over 1,400%, which were much higher than the results of the control group. Moreover, the strength was comparable to that of the control group. This polyurethane adhesive shows excellent self-healing and mechanical properties at low temperatures and is expected to provide the strong self-healing ability and mechanical properties for composite solid propellants, alleviating the problem of structural integrity damage.

Fungal Biodegradation of a Hybrid Adhesive Polymer Containing High-Biomass Content

Fungal Biodegradation of a Hybrid Adhesive Polymer Containing High-Biomass Content

Grafted chitosan thin films of various degrees of acetylation as a reusable platform for the investigation of biological interactions

Surface treatment by adhesive polymers is a promising solution to immobilize and study bacteria cells through microscopic assays and, for example, control their growth or determine their susceptibility to antibiotic treatment. The stability of such functional films in wet conditions is crucial, as the film degradation would compromise a persistent use of the coated devices. In this work, low roughness chitosan thin films of degrees of acetylation (DA) ranging from 0.5 % to 49 % were chemically grafted onto silicon and glass substrates and we have demonstrated how the physicochemical properties of the surfaces and the bacterial response were DA-dependent. A fully deacetylated chitosan film presented an anhydrous crystalline structure while the hydrated crystalline allomorph was the preferred structure at higher DA. Moreover, their hydrophilicity increased at higher DA, leading to higher film swelling. Low DA chitosan-grafted substrate favored bacterial growth away from the surface and could be envisioned as bacteriostatic surfaces. Contrarily, an optimum of Escherichia coli adhesion was found for substrates modified with chitosan of DA = 35 %: these surfaces are adapted for the study of bacterial growth and antibiotic testing, with the possibility of reusing the substrates without affecting the grafted film – ideal for limiting single-use devices.

Mechanical and free vibrational analysis of silane functionalized aluminum stacked glass fiber/epoxy laminates

ABSTRACT This study looks at the mechanical and free vibration properties of glass laminated with functionalized aluminium reinforced epoxy. NaOH, K2Cr2O7, Fe2(SO4)3. XH2O, and C8H18O3Si were employed to functionalize aluminum. The flexural, impact, and shear strengths, as well as their failures, were investigated using electron microscope images. The impulsive hammer approach was applied to investigate laminate vibration behaviour. The results showed that the flexural strength (623.83 MPa), impact strength (76.41 J/mm2), and shear strength (55.31 MPa) of C8H18O3Si functionalized laminates outperformed those of other functionalized laminates. The improvement of mechanical properties was due to the change in interfacial adhesion. This is dependent on the functionalization of aluminium used in stacked laminates. Moreover, C8H18O3Si functionalized laminates exhibit a higher natural frequency and higher damping than other functionalized laminates. This natural frequency and damping are enhanced due to the strong mechanical interlocking between polymer and metal adhesion. It was noted that the same laminates have higher toughness than other laminates because of the high impact energy obtained.

Synthesis of photoresponsive biobased adhesive polymers via the Passerini three-component reaction

Synthesis of photoresponsive biobased adhesive polymers via the Passerini three-component reaction

Exploiting perforations to enhance the adhesion of 3D-printed lap shears

Soft polymeric adhesives capable of experiencing large deformations are used in many applications, including soft robotics, stretchable electronics, and tissue engineering. The growing use of these materials raises many questions regarding their ability to maintain adhesion under loads. This work aims to study the adhesion of soft adhesives to perforated substrates. To this end, we design lap shear-based specimens from the acrylic adhesive VHB 4910 and stiff 3D-printed perforated substrates. Substrates with four different void sizes are investigated and the lap shears are subjected to displacement-controlled and force-controlled loadings. Our experiments show that the shear response can be divided into two main regions. First, the adhesion area between the soft adhesive and the substrate is maintained such that the adhesive experiences shear. Next, a debonding process of the adhesive from the substrate begins and ends with the ultimate rupture of the elastomer. Comparison between displacement and force controlled loadings reveals that the latter is characterized by limited extensibility, since the soft adhesive cannot relax. As opposed to the standard lap shears, the perforations yield a highly heterogeneous stress state that enables one to increase adhesion strength and enhance the performance of lap shears in a variety of applications.

Diabetic wound healing potential of silk sericin protein based hydrogels enriched with plant extracts

The complications associated with diabetic wounds make their healing process prolonged. Hydrogels could be ideal wound dressings therefore present research was conducted to prepare silk sericin (an adhesive protein polymer) based hydrogels in combination with plant extracts and to evaluate its effectiveness against wound healing process in mice with alloxan induced diabetes. Excision wounds were formed via a biopsy puncture (6 mm). Experimental hydrogels were prepared and applied topically on the diabetic wounds. All the hydrogel treatment groups showed significantly higher (P < 0.001) percent wound contraction from day 3 to day 11 as compared to the negative diabetic control group. The serum level of anti-inflammatory cytokine (Interleukin-10) and tissue inhibitor metalloproteinase (TIMP) was significantly higher (P < 0.001), while the level of pro-inflammatory cytokines (tumor necrosis factor-α, Interleukin-6) and matrix metalloproteinases (MMP-2, MMP-9) was significantly lower (P < 0.001) in hydrogels treatment groups as compared to diabetic control group. Although all the hydrogels showed effective results, however the best results were shown by 4 % sericin+4 % banyan+4 % onion based hydrogel. It can be concluded that Sericin based hydrogel enriched with banyan and onion extracts can be used as an effective remedy for the treatment of diabetic wounds due to their high healing and regenerative properties.

Molecular architecture regulation for the design of instant and robust underwater adhesives.

Development of underwater adhesives with instant and robust adhesion to diverse substrates remains challenging. A strategy taking the structural advantage of phenylalanine derivative, N-acryloyl phenylalanine (APA), is proposed to facilely prepare a series of underwater polymeric glue-type adhesives (UPGAs) through one-pot radical polymerization with commonly used hydrophilic vinyl monomers. The adjacent phenyl and carboxyl groups in APA realize the synergy between interfacial interactions and cohesion strength, by which the UPGAs could achieve instant (~5 seconds) and robust wet tissue adhesion strength (173 kilopascal). The polymers with varied hydrophobicity and substitutional groups as well as carboxyl and phenyl groups in separated components are designed to investigate the underwater adhesion mechanism. The universality of APA for the construction of UPGAs is also verified by the copolymerization with different hydrophilic monomers, and the applications of the UPGAs have been validated in diverse hemorrhage models and distinct substrates. Our work may give a promising solution to design potent underwater adhesives.

Click and bioorthogonal hyaluronic acid hydrogels as an ultra-tunable platform for the investigation of cell-material interactions.

The cellular microenvironment plays a major role in the biological functions of cells. Thus, biomaterials, especially hydrogels, which can be design to mimic the cellular microenvironment, are being increasingly used for cell encapsulation, delivery, and 3D culture, with the hope of controlling cell functions. Yet, much remains to be understood about the effects of cell-material interactions, and advanced synthetic strategies need to be developed to independently control the mechanical and biochemical properties of hydrogels. To address this challenge, we designed a new hyaluronic acid (HA)-based hydrogel platform using a click and bioorthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) reaction. This approach facilitates the synthesis of hydrogels that are easy to synthesize and sterilize, have minimal swelling, are stable long term, and are cytocompatible. It provides bioorthogonal HA gels over an uncommonly large range of stiffness (0.5-45kPa), all forming within 1-15min. More importantly, our approach offers a versatile one-pot procedure to independently tune the hydrogel composition (e.g., polymer and adhesive peptides). Using this platform, we investigate the independent effects of polymer type, stiffness, and adhesion on the secretory properties of human adipose-derived stromal cells (hASCs) and demonstrate that HA can enhance the secretion of immunomodulatory factors by hASCs.