Conventional sulfur network of epoxidized natural rubber (ENR) system is not stable as it is becoming more dense resulting in fast hardening of the matrix and therefore, practical use of sulfur-cured ENR is rather limited. Here, we report the stable and reversible ionic network formation of ENR using dicarboxylic acid and a suitable heterocyclic aromatic amine. This study investigates the effects of various aliphatic and aromatic heterocyclic amines on the cross-linking behavior of dicarboxylic acid, aiming to enhance the stability of ionic intermediates to establish reversible networks rather than covalent cross-links. Rheo-optical FTIR monitoring of the orientation function of carboxylate ions reveals reversible changes during cyclic uniaxial mechanical deformation, indicating that the carboxylate groups are grafted onto the backbone of the ENR macromolecules. Compared to sulfur-cured ENR, dodecanedioic acid in combination with 4-dimethylaminopyridine (DMAP) offers similar mechanical strength but improved aging resistance which can be attributed to the ionic carboxylate-based cross-linking structure. This combination leads to impart a considerable stable ionic network with self-healing nature of the rubber composites. In this system after self-healing, the tensile strength is found to be as much as similar to 11 MPa, a value which is rare in the literature.

The human broad ligament connects the uterus laterally to the pelvis as part of the uterine support system. Although being an integral part of this system, its role in the context of pelvic organ prolapse remains elusive. There is still limited knowledge if aging affects the composition and biomechanics of the broad ligament as observed in other uterine ligaments. Here, the mesometrium, the largest portion of the broad ligament, from young (n = 7) and aged female individuals (n = 19) was investigated ex vivo. First, extracellular matrix composition and collagen orientation were assessed using histology and immunofluorescence labeling. Second, nanoscale collagen deformation was quantified using small-angle X-ray scattering (SAXS) during macroscale biaxial tensile testing within physiological ranges. Muscle and collagen type I and III content varied between individuals but not with age. Glycosaminoglycan content was not significantly different between age groups. Histology and SAXS demonstrated two orthogonal collagen fiber/fibril families. Under SAXS, unloaded mesometrium samples showed high collagen fibril dispersion (82-121°) and no difference in median d-spacing (young: 64.96 nm (interquartile range, IQR, 64.94-64.98 nm); aged: 64.96 nm (IQR 64.92-64.97 nm)). Young samples showed no significant variance in nanoscale fibril strain, while aged samples varied notably in fibril strain response. The observed orthogonal fibril families with high dispersion underline the mesometrium's adaptation to multiaxial loading. While no age-related difference in median nanoscale collagen deformation response was observed, the variable response within aged samples indicates additional influencing factors beyond aging such as AGE accumulation. This highlights the need to examine how clinical factors and diseases impact collagen in the uterine support system. STATEMENT OF SIGNIFICANCE: The mesometrium, part of the broad ligament, supports the uterus and may be affected by aging, yet its mechanical properties remain under-researched. This research used advanced imaging (SAXS) and biaxial tension to explore how collagen, a key structural protein, responds to load in young and aged samples and mapped ECM composition using histology. Unlike other uterine ligaments, the broad ligament showed no major age-related differences in ECM composition or structure. Aged samples demonstrated a variable collagen nanoscale response suggesting changes in load transfer in the ECM co-occurring with age. This study advances understanding of the uterine support system and provides a foundation for future research on aging and pelvic health.

The remarkable toughness of double-network hydrogels (DNHs) arise from the energy dissipation due to the deformation-induced failure of the stiffer first network, while the softer second network maintains the sample's overall integrity. In this study, a new approach for strain field analysis suitable for DNHs has been developed by introducing lycopodium spores to create robust speckle patterns on the slippery hydrogel surface. Thus, digital image correlation (DIC) method was feasible for localized strain field analysis during mechanical deformation, i. e. tensile testing, exhibiting inhomogeneous deformation, e.g. during necking. Further, strain field analysis during re-swelling experiments, a straightforward and effective technique to visualize and characterize prestretched zones formed during necking in DNHs, has been improved. This DIC-based analysis, performed in a liquid, offers an innovative and complementary approach for internal fracture analysis of DNHs, without requiring complex post-processing, expensive instrumentation or sophisticated chemistry, and provides a deeper understanding of fracture resulting from irreversible damage in DNHs, which is dominated by first-network fracture.

Natural rubber (NR) is a biopolymer consisting of cis-1,4-isoprene units extracted from the sap of rubber trees, mainly Hevea Brasiliensis. This rubber is widely used in the automotive and other industries due to its performance and elasticity. However, synthetic rubber has largely replaced natural rubber in many applications because of the poor heat resistance of natural rubber. On the other hand, non-recyclable sulfur-based synthetic rubber composites pose a major environmental issue from the viewpoint of sustainability. In this report, a flexible (non-directional) crosslinking network based on ionic bonds in modified natural rubber (epoxy-modified NR) using dicarboxylic acid and dimethylimidazole (DMI) is presented, which eliminates the disadvantages of natural rubber and outperforms synthetic rubber without compromising its mechanical performance. Accelerated aging, temperature scanning stress relaxation, compression set, and temperature-dependent FT-IR analyses confirm the high thermal stability of ionically crosslinked natural elastomer. The ionic crosslinked rubber shows a significant improvement in initial degradation temperature (196 degrees C) compared to thermally stable synthetic elastomers, such as NBR (acrylonitrile butadiene rubber), CR (polychloroprene rubber), and peroxide-cured EPDM (ethylene propylene diene monomer). Unlike sulfur-cured elastomers, the ionically crosslinked natural rubber exhibits superior cut growth resistance and self-repairing capabilities, as demonstrated by X-ray microtomography. These findings, along with the natural origin of the developed crosslinked elastomers, can reduce environmental damage and the carbon footprint associated with sulfur-cured and petroleum-based synthetic rubber products.

Significant progress has been made in the field of dynamic reversible networks in polymers, especially in unfilled systems. However, achieving similar reversibility in highly filled and mechanically robust elastomers with restricted chain mobility remains a formidable challenge. Furthermore, characterization techniques for assessing network reversibility are not significantly advanced beyond the traditional evaluation of mechanical properties before and after healing. To this end, a dynamic interaction was studied for bromobutyl rubber (BIIR) mixed with alkyl imidazole, which facilitates the formation of reversible ionic clusters within the elastomer matrix. Moreover, a special type of carbon black with graphitic microstructure was used as a filler not only to reinforce the elastomer, but also to form reversible bonds with the alkyl imidazolium ions by cation-pi and pi-pi interactions. Through the synergistic effect of these interactions, the 1-butylimidazole-treated BIIR achieved excellent mechanical properties, including a tensile strength of 14 MPa and an elongation at break exceeding 1000 % with a self-healing efficiency of 71 %. X-ray microtomography studies provided compelling evidence of network reversibility in ionically treated BIIR. 3D reconstructions revealed that approximately 72 % of microcavities disappeared after healing, indicating enhanced material durability. The macro-scale durability was further assessed through tear-fatigue analysis, revealing significantly enhanced resistance to crack growth of the 1-buty-limidazole-treated BIIR compared to its sulfur-cured counterpart. The formation of dual dynamic interaction in combination with advanced characterization techniques provides a comprehensive approach for the development of reversible materials and access to their reversibility for real-world scenarios.

Natural rubber (NR) vulcanizates show deformation-induced structure evolution, e.g., crystallization, explaining the outstanding mechanical performance compared to other elastomers. In this study, combined in situ experiments were realized by synchronizing wide-angle X-ray scattering (WAXS) and infrared (IR) thermography on uniaxially deformed NR vulcanizates reinforced with different carbon black content. Thus, new experimental results were generated that characterize the structural evolution under deformation by a crystallization index and temperature change as a function of mechanical stress and stretch. Owing to the coupled methods, the following findings can be summarized: (i) deformation-induced crystallization is primarily controlled by the mechanical stress; (ii) at cyclic loading, hysteresis occurs and crystallites melt within a narrow stress range; (iii) IR thermography allows to follow crystallization as a function of deformation; (iv) the onset of crystallization causes a rapid increase in temperature, however, only a slight increase in stress; (v) deformation-induced crystallization shows a saturation plateau, which hardly changes with ongoing deformation; (vi) surface temperatures show a certain fluctuation that may indicate a non-uniform crystallite distribution.

To get strong and anti-freezing hydrogel with multiple contact and non-contact sensing performance, a facial method is proposed in this work using multiple physical bonding crosslinking and glycerol (GL) immersing strategy. The obtained hydrogels show a tensile stress at break of 5.4 MPa, an elongation at break of 1420 %, and a compression strength of 12.2 MPa at 80 % strain. Additionally, benefiting from the GL immersing the hydrogel shows superior anti-freezing (no ice formation at -60 degree celsius) and water retention ability (water loss less than 17 % after storing at 50 degree celsius for 7 h). Furthermore, the volume resistance of hydrogels exhibits excellent responses against humidity, temperature, strain, and stress. The variation of the resistance against temperature can be well described by the Arrhenius equation with an activation energy of 501.3 meV, verifying a band-gap dominated diffusion hopping conductive mechanism of the hydrogel. The sufficient humidity and temperature responses make the hydrogel applicable as a non-contact sensor, and the wide temperature strain sensing (-40 to 50 degree celsius) and stress sensing capability ensures that the hydrogel can be used as a contact sensor, ensuring that the hydrogel can be used as perfect flexible sensor for monitoring human motion and physiological signals.

The topical section "Advanced Testing of Soft Polymer Materials" focuses on highvalue manuscripts related to sophisticated characterization methods of soft polymer materials.Due to the increasing demands in the application of advanced technology not only in everyday life but especially in industrial applications and the increasing demands for reduction of the environmental footprint, it is necessary to replace conventional materials by soft polymers with enhanced properties and capabilities.In fact, manufacturers of soft polymer products as well as suppliers and processors of polymers, raw materials and blends or compounds are forced to apply predictive and advanced laboratory testing in the search for high-performance applications, e.g. for e-mobility (durable tires), energy generation (flexible solar or photovoltaic cells), information technology (versatile semiconductors and sensing technology), soft robotics and medical engineering (artificial tissues), or food and cosmetics industry (environmentally friendly packaging).Ideally, predictive laboratory testing balances accuracy, relevance, instrument productivity and cost-effectiveness, while providing new mechanistic insights and opportunities for modeling the overall properties of materials and products.In this context, new concepts for soft polymeric materials are of great importance, taking into account new trends in nanotechnology, multilayered and self-assembled materials, self-healing, sensor-active or functionalized polymers, biocompatibility, eco-design and recyclability.New advanced testing methods and techniques will establish links with fundamental scientific principles, even showing how test results of single pieces of uncured/cured elastomers and silicones, thermoplastic elastomer blends, (hydro-)gels or other soft polymers relate to real geometry and loading conditions, creating new opportunities to link laboratory test data to the performance of real products.Furthermore, the rapid development

For elastomers, advanced experimental techniques have been applied to better understand the impact of (micro-)structural phenomena, e.g. strain-induced crystallization (SIC), on the macroscopic fracture-mechanical properties. In this study, the formation and orientation of crystallites formed by SIC in natural rubber (NR) have been investigated at non-uniaxial tension, in fact, in "pure-shear" geometry and at crack tips, using synchrotron wide-angle X-ray scattering (WAXS).

ABSTRACT An intensive literature search shows that research in the field of self-healing rubbers is still in its infancy. By analyzing the various reviews and reports available, most of the results prove to be complicated; however, a few studies show promising self-healing properties of new elastomers. Most of these materials were prepared by relatively sophisticated chemical syntheses. Many of the studies on self-healing materials also deal with commercial rubbers, but the mechanical performance of these self-healing systems is very poor for practical application, perhaps because self-healing systems are usually prepared with an uncured or pseudo-crosslinked matrix structure. The poor mechanical properties are related to the highly viscous but inelastic nature of the uncured or only partially cured rubber compound. Importantly, most of the studies have been conducted on rubber systems without reinforcing fillers. For filler-reinforced rubber systems, the question is whether the working principle of reversible bonds is applicable. This literature review attempted to compile the current promising self-healing systems, describe their underlying chemical mechanisms, and discuss the self-healing concept from a thermodynamic perspective. In addition, this review is focused on the critical discussion of the principle and origin of self-healing behavior and finally draws conclusions on the applications and opportunities for further developments in this field.

The superlattice in a quantum dot (QD) film on a flexible substrate deformed by uniaxial strain shows a phase transition in unit cell symmetry. With increasing uniaxial strain, the QD superlattice unit cell changes from tetragonal to cubic to tetragonal phase as measured with in situ grazing-incidence small-angle X-ray scattering (GISAXS). The respective changes in the optoelectronic coupling are probed with photoluminescence (PL) measurements. The PL emission intensity follows the phase transition due to the resulting changing inter-dot distances. The changes in PL intensity accompany a redshift in the emission spectrum, which agrees with the Förster resonance energy transfer (FRET) theory. The results are essential for a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates.

Eine typische Verbindungstechnik für Glasstrukturen ist der laminierte Verbund mit weichen polymerbasierten Klebstoffen, wie Silikon. Infolge geometrischer Zwänge im laminierten Verbund, zeigen diese ein spezifisches mechanisches Verhalten: Eine sich unter Deformation einstellende überhöhte Spannungsmehrachsigkeit kann zur Kavitation führen. Zur Beschreibung dieses Schädigungsmechanismus unter praxisrelevanten Bedingungen sind angepasste, innovative Prüfmethoden wie die In situ -Dilatometrie und Röntgen-Mikrotomographie erforderlich. Diese sich ergänzenden experimentellen Ansätze ermöglichen sowohl präzise als auch ortsaufgelöste Informationen zur Entwicklung von Kavitäten in weichen Polymeren wie Elastomeren und Klebstoffen. Damage effects in soft polymeric adhesives for glass structure connections. A typical joining technique for glass structures is the laminated joint by soft polymer-based adhesives such as silicone. As a result of geometric constraints within the laminate, the polymers exhibit specific mechanical behavior: An excessive deformation-induced stress multiaxiality can lead to cavitation. To describe this damage mechanism under practically relevant conditions, advanced and innovative testing methods, such as in situ dilatometry and X-ray microtomography, are required. These complementary experimental approaches provide both precise and spatially resolved information on the development of cavities in soft polymers, such as elastomers and adhesives.

Two recently developed experimental devices for investigating soft matter deformation are presented. Both devices exploit the capabilities of a modern synchrotron beamline to enable advanced and highly precise materials-science experiments in which X-ray scattering is registered. The devices can be operated both in monotonic as well as cyclic mode and are implemented into a beamline at DESY , Hamburg (Germany). Hence, relevant experimental parameters, such as displacement, force and temperature, are recorded synchronously with the individual X-ray scattering patterns. In addition, spatial variation of materials deformation can be monitored and recorded with optical microscopy. This unique sample environment enables in situ X-ray experiments in transmission, i.e. small- or wide-angle X-ray scattering (SAXS or WAXS), and in grazing-incidence geometry, i.e. grazing-incidence (GI-) SAXS or WAXS. One device with stepper motors is designed for studies of slow, (quasi-) static deformation and the other one with pneumatic actuators can be used for fast, impact deformation. Both devices are available to external beamline users, too.

Strong, tough, and antibacterial hydrogels are promising in the fields of human motion detection and wearable electronics. However, it remains challenging to reach the antibacterial ability without losing the mechanical properties. In this work, strong and tough Fe3+-sodium alginate/poly(acrylamideco-acrylic acid)/Ag nanowire (Fe3+-SA/P(Am-co-Ac)/AgNWs) hydrogel with antibacterial ability was facially prepared using multiple physical bonds. The superior mechanical properties are ensured by the double network matrix and well-designed interface between the matrix and AgNWs. The antibacterial ability was realized by the introduction of AgNWs. The matrix contains the Fe3+-SA network and the Fe3+-P(Am-co-Ac) network, which are further united together via the shared Fe3+ based ionic interaction. The interfacial defects between AgNWs and the organic matrix were efficiently eliminated by the incorporation of bis (acryloyl)cystamine (BACA) as "bridge" molecules: the C C bond on BACA was grafted onto the main chain of P(Am-co-Ac) by free radical polymerization, and the S-S bond on BACA was anchored onto the surface of AgNWs through the Ag-S metal ligand effect. Benefiting from the multiple physical bonds and well-designed interface, the as-prepared hydrogel exhibited a stretching strength of 3.87 MPa, an elongation at break of 3127%, and a fracture energy of 112.32 MJ m(-3). The bacteriostatic ratio of the as-prepared hydrogel against E. coli and S. aureus bacteria was as high as 99.98% and 99.95%. Moreover, the hydrogel displayed a conductivity and strain sensitivity (GF) of 0.01 and 0.59, a broad working range of 0-500%, and 500 cycles of loading-unloading under a strain of 40%, enabling the hydrogel to be sensitive on a large scale and with subtle body movements and making hydrogel the perfect strain sensor to monitor various human motions.

The deformation and failure behavior of rubbers is significantly influenced by the chemical composition and loading conditions. Investigations on how specific loading parameters affect the mechanical behavior of rubbers are elementary for designing elastomeric products. Suitable fracture mechanical concepts describing the failure behavior of rubbers are widely accepted in industrial and academic research. However, the most common failure analyses base on macroscopic approaches which do not consider microscopic damage, although a contribution of (micro)structural changes at the network scale on the overall mechanical properties is very likely. A special phenomenon in terms of microstructural failure is cavitation due to strain constraints. Under geometrical constraints, the lateral contraction is suppressed. As a result, stress triaxiality causes inhomogeneous deformation, and internal defects, so-called cavities, appear. The formation and growth of cavities release stress and reduce the degree of constraints. Cavitation in rubbers has been studied for several decades, but the knowledge about the fundamental mechanisms triggering this process is still very limited. The present study aimed to characterize and describe cavitation in rubbers comprehensively. Hence, advanced experimental techniques, such as dilatometry and microtomography, have been used for in situ investigations on pancake specimens. Such thin disk-shaped rubber samples are characterized by a high aspect ratio. As a result, the degree of stress triaxiality is high, and the dominating hydrostatic tensile stress component causes the initiation of cavitation. Of special interest was the often suspected cavitation in unfilled rubbers. In contrast to the literature, cavitation in rubbers is not exclusively attributed to interfacial failure between the soft rubber matrix and rigid filler particles, but occurs also in unfilled rubbers. The onset of cavitation was determined precisely by highly sensitive data acquisition. Both a stress-related and an energy-based cavitation criteria were found indicating that traditional approaches predicting cavitation overestimate the material resistance against cavitation. The presented experimental methods to characterize cavitation are suitable for future studies investigating further aspects of cavitation in rubbers and other rubberlike materials, e.g., the failure behavior under dynamic loading.

Advanced experimental techniques in terms of in situ dilatometry and X‐ray microtomography as well as microscopy have been used to investigate cavitation in unfilled and carbon black reinforced styrene‐butadiene rubber vulcanizates. The work introduces into the features of multiaxial deformation and damage behavior characterized by the formation and growth of internal defects – so‐called cavities . Experimental evidence indicates that cavitation damage occurs in rubber vulcanizates subjected to constrained tensile deformation, while the number of cavities is increasing, but the average cavity size is decreasing with increasing degree of constraints.

: Despite their technological relevance, the resistance of soft thermoplastic polyurethanes (TPU) to crack propagation in cyclic fatigue has never been investigated in detail. In particular, a clear shortcoming in the literature for this class of materials is the lack of connection between the cyclic fatigue resistance and the large strain behavior that has a fundamental role in de fi ning the material ’ s resistance to crack propagation. We demonstrate here for the fi rst time that when the strain-induced sti ff ening mechanism of TPU (already observed for large deformation) is combined with the presence of the nonhomogeneous strain, as in the case of cyclic fatigue, it produces a selective reinforcement in the crack tip area, which is the key to explain the remarkable cyclic fatigue resistance of TPU. Using commercial TPU with similar modulus ( ∼ 8 MPa) but di ff erent large strain behavior, we show that the described mechanism stems from the multiphase nature of TPU and it is not necessarily linked to a speci fi c large strain property as the case of TPU, which undergoes strain-induced crystallization.

Cavitation under constrained tension is a critical failure phenomenon in rubber parts. For laboratory tests, strain constraints can be generated using disk‐shaped rubber samples, that is, pancake specimens. Due to suppressed transverse contractibility, the dominating hydrostatic tensile stress, which is the highest in the center part of a pancake specimen, causes an internal failure process controlled by the formation and growth of cavities. Laboratory X‐ray microtomography (μCT) is a powerful tool to monitor the evolution of a cavity population considering various aspects of geometrical as well as microstructural constraints. In the case of carbon black–reinforced styrene‐butadiene rubber, microscopic cavities are surrounded by a region of significantly lower material density. Due to detection limits, this region cannot be analyzed in depth with μCT. In this study, synchrotron X‐ray microtomography (SRμCT) in combination with a modular load frame is used, for the first time, to investigate the damaging phenomenon of cavitation in rubbers. Due to the high phase contrast that can be achieved only by SRμCT, the microstructure of regions of lower material density can be analyzed and, as a result, tiny satellite cavities are identified in the walls of neighboring microscopic cavities.

It is known, that under constrained tensile deformation the mechanical response and the failure behavior of rubber vulcanizates reveal unlikely features. Due to multiaxial stress concentrations, the formation of internal cracks can be initiated. For the first time, fundamental investigations on unfilled styrene-butadiene-rubber pancake specimens were performed. Via in situ dilatometry and X-ray microtomography experiments, the damage process under constrained tensile deformation is studied and discussed. Although cavitation has been often discussed for filler reinforced rubber vulcanizates, the results of this study demonstrate how it occurs also in unfilled rubbers. In fact, the stronger the geometrical constraints are, the higher is the number of small cavities. However, the integral cavity volume is not affected. Moreover, micrographs of fracture surfaces indicate that cavitation is controlled by an omnidirectional growth of radial side-cracks. Finally, an energy-based approach to describe the cavitation onset criterion initiating the damaging process is presented to revise Gent's theory.