The article consists of two parts, introducing the field of mechanical bond chemistry, followed by the research activities of the Supramolecular Organic Chemistry Group at the University of Wrocław. The first, literature-based section introduces the concept of the mechanical bond, outlining its structural and chemical consequences. The main classes of mechanically interlocked molecules, i.e., rotaxanes, catenanes, and molecular knots, are briefly characterized, with particular attention given to how mechanical bonding influences their stereochemistry, reactivity, and dynamic behavior. The second part presents an overview of the Supramolecular Organic Chemistry Group, established in 2021 at the Faculty of Chemistry, University of Wrocław. It summarizes the group’s history, growth, and major research interests, which focus on the design, synthesis, and investigation of novel mechanically interlocked molecules. Special emphasis is placed on ongoing projects concerning functional rotaxanes, catenanes, and dynamic systems that form the basis for exploring new types of molecular machines. The article aims to highlight both the broader significance of mechanical bond chemistry and its specific role in the current research directions developed within the Wrocław group.

Aiming to deepen the fundamental understanding of how hierarchical molecular packing governs the overall photophysical properties in multi-chromophore systems, engineering pyrene stacking with mechanical bonds has been successfully realized, leading to the construction of a novel family of pyrene-functionalized [1]rotaxanes, particularly ones with tunable triple-layered pyrene stacking. The precisely controlled pyrene excimer conformations in these structures enable adjustable photophysical behaviors, particularly in circularly polarized luminescence (CPL), including tunable luminescence dissymmetry factors (glum), invertible handedness, and programmable emission wavelengths. Notably, introducing a third pyrene unit into tris-pyrene-functionalized [1]rotaxanes further modulates CPL properties through synergistic or antagonistic interactions, as further confirmed by time-dependent density functional theory (TD-DFT) simulations, revealing a previously unobserved stacking effect. This correlation between spatial stacking and photophysical response not only provides more in-depth fundamental insights for pyrene excimer emissions but also offers critical design principles for developing advanced chiral luminescent materials.

The prevalence of mechanical structures in industrial sectors has increased thanks to 3D printing technology. This technology requires fewer mechanical bonds to assemble structures, but challenges arise due to material differences and cost. One impactful approach to enhancing mechanical characteristics is to design sandwich structures. This study used ASA and ABS to produce a sandwich composite, exploiting each material's positive attributes. The mechanical properties of the composite sandwich plates were investigated to assess their use as structural parts. The outer parts of the sandwich structure are made of ASA material resistant to external factors and the inner part is made of ABS material with flexural strength. Layer thickness was utilised as a variable printing parameter. In the present study, tensile and flexural tests were conducted, with the objective of comparing the mechanical characteristics of components fabricated from pure ASA and ABS materials, and from sandwich composite parts. The findings of the study demonstrated that the maximum tensile strength of 33.18 MPa and the maximum flexural strength of 57.78 MPa were observed in the sandwich samples produced with an ASA/ABS/ASA layer thickness of 0.15 mm. The study is of significance to industries such as automotive and aviation, insofar as it explores the potential areas of use for functional sandwich structures produced from different materials and increases their use.

Mechanically interlocked polymers (MIPs) are a class of polymer structures in which the components are connected by mechanical bonds instead of covalent bonds. We measure the single-molecule rheological properties of polyrotaxanes, daisy chains, and polycatenanes under steady shear and steady uniaxial extension using coarse-grained Brownian dynamics simulations with hydrodynamic interactions. We obtain key rheological features, including tumbling dynamics, molecular extension, stress, and viscosity. By systematically varying structural features, we demonstrate how MIP topology governs flow response. Compared to linear polymers, all three MIP architectures exhibit enhanced tumbling in shear flow, weaker shear thinning, and lower normal stress differences in extensional flow. While polyrotaxanes show higher shear and extensional viscosities, polycatenanes and daisy chains have lower viscosities. In extensional and shear flows, MIPs typically extend more in the flow direction and at weaker flow strengths than linear polymers. These effects arise from the mechanically bonded rings in MIPs, which expand the polymer profile in the gradient direction and increase backbone rigidity due to ring-backbone repulsions. This study provides key insights into MIP flow properties, providing the foundation for their systematic development in engineering applications.

ABSTRACTMechanically interlocked molecules (MIMs), specifically rotaxanes, have been demonstrated to have immense utility as sensing materials with a wide array of analytes, owing to their unique topologies and properties afforded by the presence of a mechanical bond. Among other more conventional sensor compounds, aromatic amide functionalities have been employed to induce intramolecular charge transfer (ICT) processes, where a crown ether donor oxygen atom donates electron density to an aromatic amide acceptor, resulting in reduced or no emission; this methodology has received less attention for its application in rotaxanes, particularly to detect anionic species. Hence, in this work, we were inspired to construct a novel kinetically stable [1]rotaxane comprising dibenzo[24]crown‐8 donor and N‐benzylbenzamide acceptor moieties, namely 1‐H(Rot)·PF6, using a template‐directed “slippage” approach. Before [1]rotaxane formation, the linear molecule showed ICT response. Fluorescence response was restored after the [1]rotaxane formed as the dialkylammonium group threaded through the crown ether, inhibiting ICT from the oxygen atoms to the aromatic amide. The [1]rotaxane showed marginal fluorescence quenching when titrated with different metal cations by a photoinduced electron transfer (PeT) mechanism; however, when titrated against various inorganic anions, 1‐H(Rot)·PF6 exhibited substantial emission quenching (up to ca. 50%) in the presence of phosphate (PO43‒).

Efficient routes to [2]rotaxanes are often compromised by formation of irrecoverable, non-interlocked byproducts. Herein, we report a thermodynamically steered, atom-economical strategy that couples a Cu(i)-templated, low-strain Sauvage-type [2]catenane with di-stoppered olefin via ring-opening double cross-metathesis (RO-DCM), implementing dynamic covalent chemistry to bias the system toward the most stable interlocked architecture. The transformation proceeds through ring opening of the metalated [2]catenane and its in situ “insertion” into the axle, engaging internal olefins on both partners. Optimization of metathesis parameters (Grubbs II, DCM, 40 °C) identified the stoichiometry of the di-stoppered olefin as the key lever; using ten equivalents furnished the metalated [2]rotaxane 6 in up to 88% isolated yield while suppressing mono-stoppered byproducts. Subsequent demetalation cleanly delivered [2]rotaxane 9. Analytical size-exclusion chromatography across the full component set provided diagnostic retention times, confirming product identity and the absence of catenane contamination. No dethreading of macrocycle 1 from 9 was detected under conventional heating in DCM or DMSO over 12–48 hours, underscoring kinetic persistence of the mechanical bond. Overall, this RO-DCM platform minimizes non-interlocked waste streams while providing a concise, high-yield entry to [2]rotaxanes from metathesis-addressable, copper-templated interlocks. Beyond the single-molecule level, the approach establishes a general ring-chain equilibration blueprint that should translate to sequence-defined, mechanically interlocked oligomers and polymers.

Background. Traditional socket prostheses suffer from several limitations, including skin complications, unstable fixation, and restricted patient mobility. Osseointegrated exoprostheses represent a promising alternative as they attach to the human body via an implant surgically placed in the residual bone. This solution provides secure fixation and is particularly effective for patients with short or pathological residual limbs. The aim of the study — to evaluate the biocompatibility and safety of a domestically developed osseointegration system for femoral exoprosthetics using a large animal model. Methods. A customized titanium osseointegrated implant, adapted based on CT data, was placed in one sexually mature minipig using a two-stage surgical protocol. During the 3-month observation period, a comprehensive set of clinical, laboratory, and radiographic examinations was performed. The study also involved routine stoma care and bacteriological monitoring. At the end of the period, an implant pull-out test was conducted. Results. The animal was able to endure weight-bearing on the prosthesis while standing and walking. Body weight increased by approximately 10 kg. The implant pull-out force was 400 N, indicating the formation of a mechanical bond with the bone. Manageable complications were noted during the observation, specifically the development of anemia and asymptomatic bacterial colonization of the stoma with Staphylococcus spp. at 107 CFU/ml. There were no clinical signs of infection or systemic inflammatory response. Conclusion. The study demonstrated the feasibility of the successful and safe application of the evaluated osseointegration system in a large animal model. The observed complications were not critical. The findings confirm the biocompatibility and functionality of the system, justifying the need for further expansive preclinical studies.

Mechanical Bonds Enable Stretchability–Strength Balance in Graphene-Based Fibers

Epoxy resins, while indispensable for their excellent mechanical strength, face fundamental limitations due to their inherent brittleness. Here we present a novel advancement in epoxy toughening through the strategic incorporation of [2]rotaxane-based mechanical bond as mechanically interlocked cross-linker, whose unique intramolecular motion enables efficient energy dissipation and stress redistribution under external force. As a result, the as-prepared mechanically interlocked epoxy networks (MINEP) exhibit elongation of 272% and toughness of 37.9MJ m-3, both representing an order-of-magnitude improvement over the conventional counterpart while showcasing notable properties compared to other epoxy materials. Further, we capitalize on the adhesive effect and good toughness of MINEP to toughen graphene films. Compared to pristine graphene films, the MINEP-bonded films show significantly enhanced toughness (30.2versus 3.4MJ m-3), elongation (26.5%versus 9.9%), and maximum strength (237versus 72.3MPa). This work not only provides an effective strategy for the development of high-performance epoxy resins, but also exploits their application potential in toughening two-dimensional (2D) materials.

ConspectusAs a typical class of mechanically interlocked molecules (MIMs), rotaxanes reveal unique interlocked structures, as well as controllable dynamic behaviors that originate from the mechanical bonds. Owing to such attractive structural and dynamic features, rotaxanes have proven to be not only privileged candidates for the construction of diverse artificial molecular machines such as molecular shuttles, molecular muscles, and molecular pumps but also versatile platforms for wide applications in sensing, drug delivery, and catalysis. In particular, aiming at the construction of novel rotaxanes with intriguing (chir)optical properties, the rapid development of luminescent rotaxanes, particularly ones with attractive circularly polarized luminescence (CPL), has been witnessed. On the one hand, the unique interlocked structures of rotaxanes enable the facile introduction of various luminogens into different components with well-defined and tunable chiral arrangements. This makes the resultant integrated luminescent rotaxanes not only attractive candidates for the development of novel CPL-active materials with desirable and tunable CPL performances but also promising platforms for investigations of structure-property relationships. On the other hand, the controllable dynamic features of rotaxanes could lead to the successful construction of novel smart chiral luminescent materials with precisely switchable CPL emission states, including the handedness, emission wavelength, photoluminescence quantum yield (PLQY), and dissymmetry factor (glum). This further extends their applications in diverse fields, such as smart devices and sensors. Considering all the above broad potential applications, the design and construction of novel CPL-active rotaxanes, particularly ones with tunable and switchable CPL performances, are of great importance.During recent years, through the rational design and synthesis of chiral rotaxanes with precisely arranged luminogens, we realized the successful synthesis of a series of CPL-active rotaxanes. We first confirmed the unique role of mechanical bonds in boosting the CPL performance of chiral pillar[5]arene wheels upon the formation of rotaxanes, highlighting that rotaxanes can serve as promising platforms for the design and construction of novel CPL emitters. Furthermore, through the rational design and synthesis of mechano-stereoisomers, including both static and dynamic ones, the precise tuning and switching of the CPL performances of diverse chiral rotaxanes were successfully realized. In addition to individual chiral rotaxanes, we also showed an interesting generation-dependent CPL performance of rotaxane-branched dendrimers with multiple chiral rotaxane units as branches and realized further enhancement of their CPL performances through sequential light harvesting. In this Account, we summarize our above exploration of rotaxanes with tunable and switchable CPL performances, and we hope that it will inspire scientists from various disciplines to explore these appealing and versatile platforms for wide applications.

Aluminum nitride (AlN) ceramic materials are increasingly utilized in advanced electronic devices and semiconductors due to their exceptional thermal conductivity, low thermal expansion coefficient, and excellent electrical insulation properties. However, raw AlN suffers from rapid hydrolysis when exposed to atmospheric moisture and incurs high storage costs, significantly limiting its widespread application in industry. In this research, we developed a novel approach to modify raw AlN by applying parylene C coating using a rotary powder coating machine, which enhanced both hydrolysis resistance and thermal conductivity in epoxy composites. The characteristics of AlN powder before and after coating were comprehensively analyzed using microscopic mapping images, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. These analyses revealed the mechanism underlying the improved hydrolysis resistance. The parylene C modification dramatically affected surface hydrophobicity, increasing the water contact angle to 144° compared to untreated AlN. Remarkably, the modified powder remained stable without hydrolysis under severe conditions of 100% humidity at 50°C for extended periods. During the heat treatment process, pyrolyzed parylene C monomers polymerized and formed strong mechanical bonds with the AlN core, creating an ultrathin 8 nm-thick protective layer on the AlN crystal surface. This conformal coating effectively prevented water molecule penetration and inhibited the hydrolysis reaction that typically produces aluminum hydroxide and ammonia gas. Furthermore, the parylene C structure exhibited beneficial interactions with the epoxy matrix through π-π stacking and van der Waals forces, significantly enhancing the thermal conductivity of the resulting composite materials. Thermal conductivity measurements demonstrated improvements up to 8.5 W m⁻¹ K⁻¹ at 60 vol% loading in the modified composites compared to 7.1 W m⁻¹ K⁻¹ for those using untreated AlN. This study presents a straightforward, environmentally friendly, and industrially scalable strategy for simultaneously improving both the anti-hydrolysis properties of AlN powder and enhancing the quasi-isotropic thermal conductivity of polymer composites, making this approach particularly valuable for thermal management applications in next-generation electronics. Figure 1

Taming the elusive cyclo[n]carbon: how the mechanical bond stabilizes the unstable

Abstract Two-dimensional polymers (2DPs), comprising mono- or multilayer covalent polymeric networks with long-range order in two orthogonal directions, are of considerable interest due to their unique physicochemical properties. However, achieving precise thickness control from monolayer to bilayer, crucial for exploring proximity effect-driven phenomena beyond the monolayer limit, remains synthetically challenging. Here we report the on-water surface synthesis of crystalline mechanically interlocked monolayer and bilayer 2DP (MI-M2DP and MI-B2DP) films by embedding macrocyclic molecules with one and two cavities into 2DP backbones. The incorporation of bulky macrocyclic molecules introduces periodic mechanical bonds that precisely control interlayer interlocking, enabling selective monolayer or bilayer 2DP formation. Both MI-M2DP and MI-B2DP exhibit homogeneous, large-area films with ordered hexagonal pores and high modulus. MI-B2DP demonstrates an exceptionally high effective Young’s modulus of 151 ± 16 GPa (indentation method), surpassing MI-M2DP (90 ± 14 GPa), van der Waals-stacked MI-M2DPs (46 ± 11 GPa) and other reported multilayer 2DPs (<50 GPa). Modelling confirms that the mechanical interlocking minimizes interlayer sliding and reinforces the structure.

Catenated cyclocarbon: Stabilizing cyclo[48]carbon in solution with mechanical bonds

Dielectric mechanism and chemical bond characteristics of BaZn1-Cu P2O7 ceramics in MW/THz frequency bands

Abstract Laser Impact Welding (LIW) is a specialized, solid-state method for joining small metallic sheets or foils at the scale of a few millimeters using high-powered laser pulses. Unlike traditional welding methods, LIW avoids bulk melting, thereby minimizing the occurrence of associated defects and distortions. Its working mechanism involves laser-induced vaporization of a thin film to create a high-pressure plasma that propels a flyer material at high speed into a target material, creating a strong mechanical bond upon impact. The process is ideal for joining two metals having vastly different thermal properties, such as aluminum, steel, and copper, stemming from the ability to create durable mechanical bonds whose strength is reinforced by unique, wave-like, interfacial material penetrations. Accordingly, LIW is particularly attractive for electronics, aerospace, and automotive industries, wherein lightweight and strong joints or connections involving dissimilar materials are needed at a small (millimeter) scale. This review article explores the state of both experimental and computational research into LIW, with an emphasis on recent efforts to further understand the process mechanisms and to simulate the process in order to aid its practical implementation. Discussed are new insights into how the material properties, laser parameters, physical set-ups, and resulting shockwave dynamics influence the bond quality. Also discussed is continuing research on LIW, to render it more practical for widespread industrial use, and to adapt it into a novel solid-state additive manufacturing method.

Mechanically interlockedpeptides (MIPs) possess exceptional biologicalstability, making them promising scaffolds for therapeutic development.However, despite advances in biological and chemical synthesis, theiraccessible chemical space remains limited. In particular, practicalmethodologies and rational design principles for mechanically interlockingand stabilizing conventional linear peptides are still underdeveloped.Here, we present a robust strategy for peptide interlocking and stabilizationusing active-template Cu­(I)-catalyzed azide–alkyne cycloaddition(AT-CuAAC). Through systematic exploration of amino acid side chains,macrocycle size, peptide length, and reaction conditions, we establisheddesign guidelines and constructed a diverse library of interlockedshort peptides. This approach was further applied to longer peptidesequence, [Y]6-AngII, using both convergent and iterativeassembly routes, significantly broadening its applicability. Furtherbiological experiment demonstrated that mechanical interlocking confersexceptional stability, with interlocked peptides maintaining >95%integrity in plasma after 48 h and 20% in whole blood after 24 h,far outperforming noninterlocked counterparts. Metabolite profilingreveals the mechanical bond protects ≥8 contiguous residues,with terminal hydrolysis dominating degradation while core regionsremain shielded. Collectively, this work provides a robust and broadlyapplicable approach for MIP construction, offering key insights intothe mechanistic basis of mechanical stabilization, and expands thetoolkit for designing robust peptide therapeutics.

Abstract Epoxy resins, while indispensable for their excellent mechanical strength, face fundamental limitations due to their inherent brittleness. Here we present a novel advancement in epoxy toughening through the strategic incorporation of [2]rotaxane‐based mechanical bond as mechanically interlocked cross‐linker, whose unique intramolecular motion enables efficient energy dissipation and stress redistribution under external force. As a result, the as‐prepared mechanically interlocked epoxy networks (MINEP) exhibit elongation of 272% and toughness of 37.9 MJ m−3, both representing an order‐of‐magnitude improvement over the conventional counterpart while showcasing notable properties compared to other epoxy materials. Further, we capitalize on the adhesive effect and good toughness of MINEP to toughen graphene films. Compared to pristine graphene films, the MINEP‐bonded films show significantly enhanced toughness (30.2 versus 3.4 MJ m−3), elongation (26.5% versus 9.9%), and maximum strength (237 versus 72.3 MPa). This work not only provides an effective strategy for the development of high‐performance epoxy resins, but also exploits their application potential in toughening two‐dimensional (2D) materials.

DNA catenanes are molecular structures composed of two interlocked circular DNA molecules, held together by a mechanical bond─a topological constraint arising from their mutual interlocking. Using all-atom molecular dynamics simulations, we investigated the structural and dynamical properties of DNA catenanes formed by small double-stranded DNA minicircles. In homocatenanes with mild torsional stress (82 bp-82 bp and 92 bp-92 bp), the minicircles largely retain circular conformations, and the mechanical bond exhibits constrained fluctuations in both bond length and twist angle. Rotational diffusion occurs on the microsecond time scale. In the heterocatenane (76 bp-82 bp), elevated torsional stress promotes kink formation in the 76-bp minicircle, leading to a distorted elliptical shape, enhanced DNA-DNA contacts, and anisotropic relaxation characterized by double-exponential decay in both relative translation and twist. Ion distribution analysis shows Na+ enrichment in the interstitial region between the two DNA minicircles, indicating that counterion condensation also occurs within the interlocked structures. Taken together, these results provide quantitative characterization of relative translation, twisting, and rotation in homocatenanes, while for the heterocatenane the emphasis is placed on qualitative interpretation of anisotropic relaxation. This study highlights how DNA conformation and topological constraints shape the structural and dynamic behavior of DNA catenanes.

Influence of bionic microstructures on the bond strength of additively manufactured zirconia.