Pulley Effect Research Articles

Bispillar[5]arene-Based Slide-Ring Polyrotaxanation Enables Enhanced Toughness, Recyclability, Impact, and Puncture Resistance of Polyisoprene Elastomers.

A series of slide-ring polyrotaxanes (SRPs) have been constructed by the solvent-free blending of a ditopic pillar[5]arene (DP5A) and polyisoprene (PIP) after thermal annealing. Solid-state 13C NMR experiments supported the fact that the pillar[5]arene rings of DP5A were threaded by PIP chains to afford physically interlocked networks. Tensile tests revealed that 1% of DP5A can improve the elongation at break from 50 to 239%, the tensile modulus from 2.1 to 3.9 MPa, and the toughness from 0.35 to 4.5 MJ/m3. Impact and puncture resistance experiments show that the DP5A-doped materials exhibit remarkable enhancement of protective and impalement-resistant performance. The samples can be also recycled repeatedly due to their physical crosslinking nature. The important stress delocalization effects have been attributed to the pulley effect of DP5A in the SRP materials, which represents a supramolecular approach for improving the performance of PIP elastomers.

Pulley Effect in the Capture of DNA Translocation through Solid-State Nanopores.

Nanopores are powerful single-molecule sensors for analyzing biomolecules such as DNA and proteins. Understanding the dynamics of DNA capture and translocation through nanopores is essential for optimizing their performance. In this study, we examine the effects of applied voltage and pore diameter on current blockage, translocation time, collision, and capture location by translocating λ-DNA through 5.7 and 16 nm solid-state nanopores. Ionic current changes are used to infer DNA conformations during translocation. We find that translocation time increases with pore diameter, which can be attributed to the decrease of the stall force. Linear and exponential decreases of collision frequency with voltage are observed in the 16 and 5.7 nm pores, respectively, indicating a free energy barrier in the small pore. Moreover, the results reveal a voltage-dependent bias in the capture location toward the DNA ends, which is explained by a "pulley effect" deforming the DNA as it approaches the pore. This study provides insights into the physics governing DNA capture and translocation, which can be useful for promoting single-file translocation to enhance nanopore sensing.

Multifunction composite phase change material with inorganic flame retardant and organic form stability for improving battery thermal safety

<p>Phase change materials (PCMs) with superior cooling capacity and temperature equalization have great potential to mitigate thermal accumulation, benefiting the safety of electric vehicles (EVs) drivers. Although the composite phase change materials (CPCMs) with organic form stable addition can prevent leakage, they are still restricted in battery module due to easy flammable performance. Another challenge is that the inorganic flame retardants always distribute unevenly in organic CPCMs. Herein, to overcome the drawback of uneven additives dispersion within paraffin, we proposed a novel CPCM with inorganic flame-retardant and organic form stable material, composed of Paraffin/Styrene-Ethylene-Butylene-Styrene/AmmoniumPolyphosphate/Silicon dioxide/Carbon micro-nano aggregates (PS/APP/SiO<sub>2</sub>@C). The prepared material exhibits anti-leakage property with 99.5 % mass retention after heating for 10 h at 70 ��C, and the smoke generation rate is only 0.01 m<sup>2</sup>��s<sup>-1</sup>. The total heat releasing time is extended to 700 s, three times longer than that of PS. As for battery thermal management system, the maximum temperature and the temperature difference of battery module with PS/APP are 81.2 ��C and 5.6 ��C at 5 C discharge rate, respectively. In comparison, the maximum temperature and maximum temperature difference can be controlled to 58.5 ��C and 1.5 ��C, respectively, without heat accumulation during the twenty cycles. It indicates that the temperature is lower than the critical one to avoid thermal runaway of EVs. Therefore, this study presents CPCMs as an advanced thermal management approach that can enhance the thermal safety of battery packs, resulting in a significant impact on millions of drivers of EVs around the world.</p>

Topological Hydrogels for Long-Term Brain Signal Monitoring, Neuromodulation, and Stroke Treatment.

Stroke is the primary cause of disability without effective rehabilitation methods. Emerging brain-machine interfaces offer promise for regulating brain neural circuits and promoting the recovery of brain function disorders. Implantable probes play key roles in brain-machine interfaces, which are subject to two irreconcilable tradeoffs between conductivity and modulus match/transparency. In this work, mechanically interlocked polyrotaxane is incorporated into topological hydrogels to solve the two tradeoffs at the molecular level through the pulley effect of polyrotaxane. The unique performance of the topological hydrogels enables them to acquire brain neural information and conduct neuromodulation. The probe is capable of continuously recording local field potentials for eight weeks. Optogenetic neuromodulation in the primary motor cortex to regulate brain neural circuits and control limb behavior is realized using the probe. Most importantly, optogenetic neuromodulation is conducted using the probe, which effectively reduces the infarct regions of the brain tissue and promotes locomotor function recovery. This work exhibits a significant scientific advancement in the design concept of neural probes for developing brain-machine interfaces and seeking brain disease therapies.

Controlled Degradation and Erosion of Polyrotaxane Solids via the Formation of Multivalent Hydrogen Bonding in Water

AbstractBiodegradable polyrotaxanes (PRXs) are important scaffolds for the development of biomaterials. However, the degradation behavior of PRXs constructed via physical crosslinking remains largely unexplored. Herein, a degradable PRX exhibiting physical hydrogen bonds as crosslinks between α‐cyclodextrins (α‐CDs) as the cyclic molecules is synthesized by introducing hyperbranched polyglycerol (HPG) containing numerous terminal 1,2‐diols into the α‐CDs with an incorporation ratio of HPG (HPG/PRX) varying from 2 to 19 via anion ring‐opening polymerization of glycidol. Rheological analysis by a frequency sweep test reveals that a typical HPG‐PRX forms hydrogels by physical crosslinking via hydrogen bonding, whereas a low branched degree of HPG in HPG‐PRX weakens the physical crosslinking. The obtained gels recover their original shape upon pulling and releasing, which is consistent with a pulley effect. Degradation and erosion tests in water show that increasing the molecular weight of the introduced HPG changes the degradation behavior from bulk degradation to surface erosion. Owing to its controllable degradation or erosion by tuning the rate of water ingress according to the number of hydrogen bonds and the branched degree, this HPG‐modified PRX paves the way for the development of new biodegradable/erodible gels.

Enhanced Pulley Effect for Translocation: The Interplay of Electrostatic and Hydrodynamic Forces.

Solid-state nanopore sensors remain a promising solution to the rising global demand for genome sequencing. These single-molecule sensing technologies require single-file translocation for high resolution and accurate detection. In a previous publication, we discovered a hairpin unraveling mechanism, namely, the pulley effect, in a pressure-driven translocation system. In this paper, we further investigate the pulley effect in the presence of pressure-driven fluid flow and an opposing force provided by an electrostatic field as an approach to increase single-file capture probability. A hydrodynamic flow is used to move the polymer forward, and two oppositely charged electrostatic square loops are used to create an opposing force. By optimizing the balance between forces, we show that the single-file capture can be amplified from about 50% to almost 95%. The force location, force strength, and flow rate are used as the optimizing variables.

Silent elongation of polyrotaxane and its composites

Polyrotaxanes (PR) have attracted great interest due to their unique mechanical properties, exhibiting the pulley effect, via their slide-ring topological structure. Flexible and functional composite materials consisting of PR and inorganic particles, particularly those with plasma-surface modifications, have also shown higher toughness, even with large amounts of inorganic particles present. In this study, we verified the effect of neat PR and its composites with graphene nanoplates or carbon nanofibers by measuring acoustic emission (AE). Simultaneous AE and tensile measurements were tested several times for each sample, and AE signals during elongation were acquired. It revealed that the conventional fixed cross-linked elastomer materials showed AE signals in the entire tensile region, while the movable-cross-linked materials of PR showed almost no AE signal counts. This suggests that neat PR had almost no microscopic fracture before final breakage via the pulley effect. PR composites with plasma-surface-modified fillers showed a lower number of AE signals than that with unmodified fillers. This might be due to the surface modification of fillers, which improved filler dispersibility and/or prevented a large drop in the mobility of cross-linking points.

Pressure-Sensitive Supramolecular Adhesives Based on Lipoic Acid and Biofriendly Dynamic Cyclodextrin and Polyrotaxane Cross-Linkers.

Slide-ring materials are polymer networks with mobile cross-links that exhibit impressive stress dissipation and fracture resistance owing to the pulley effect. On account of their remarkable ability to dissipate the energy of deformation, these materials have found their way into advanced materials such as abrasion-resistant coatings and elastic battery electrode binders. In this work, we explore the role of mobile cross-links on the properties of a biofriendly pressure-sensitive adhesive made using composites of cyclodextrin-based macromolecules and poly(lipoic acid). We modify cyclodextrin-based hosts and polyrotaxanes with pendant groups of lipoic acid (a commonly ingested antioxidant) to incorporate them as cross-links in poly(lipoic acid) networks obtained by simple heating in open air. By systematically varying the adhesive formulations while probing their mechanical and adhesive properties, we uncover trends in structure-property relationships that enable one to tune network properties and access biofriendly, high-tack adhesives.

Elasticity of Slide-Ring Gels.

Slide-ring gels are polymer networks with cross-links that can slide along the chains. In contrast to conventional unentangled networks with cross-links fixed along the chains, the slide-ring networks are strain-softening and distribute tension much more uniformly between their strands due to the so-called "pulley effect". The sliding of cross-links also reduces the elastic modulus in comparison with the modulus of conventional networks with the same number density of cross-links and elastic strands. We develop a single-chain model to account for the redistribution of monomers between network strands of a primary chain. This model takes into account both the pulley effect and fluctuations in the number of monomers per network strand. The pulley effect leads to modulus reduction and uniform tension redistribution between network strands, while fluctuations in the number of strand monomers dominate the strain-softening, the magnitude of which decreases upon network swelling and increases upon deswelling.

A simple preparation method of rotaxane cross-linker based on γ-cyclodextrin and its application in hydrogel materials

Currently, preparation of rotaxane cross-linker (RC) requires at least two-step or more complex chemical reactions. Therefore, a simple and efficient method is proposed to prepare RC based on γ-Cyclodextrin (γ-CD), which requires only one-step chemical reaction. This means that it is more convenient to apply RC to prepare hydrogels with pulley effect. The structures of RC are characterized by 1 H NMR, 2D NOESY NMR, DOSY NMR, XRD and thermal gravimetric analysis. And the effects of reaction conditions on the yield of RC are studied. RC and traditional cross-linker (N, N’-Methylenebis(acrylamide), MBA) are, respectively, can be copolymerized with acrylamide (AM) to prepare hydrogels to compare the swelling ratios and deformation properties of hydrogels. Furthermore, the effect of mineralization degrees on the swelling ratios of hydrogels and the effect of hydrogels prepared with different content of cross-linker on deformation properties are explored. After absorbing water for 200 h, the swelling ratio of slip-ring hydrogel 0.5% (% is the weight percentage of cross-linker to AM) is 79.05, while that of traditional hydrogel 0.5% is 8.8. The elongation at break of traditional hydrogel 0.6% (211%) is much smaller than that of slip-ring hydrogel 0.6% (6467%) and the compression modulus of traditional hydrogel 0.6% (0.20 MPa) are greater than that of slip-ring hydrogel 0.6% (0.11 MPa). Thus, the swelling ratios and deformation properties of hydrogel prepared by RC are better than that of hydrogel prepared by traditional cross-linker. Lastly, the seepage properties of hydrogel dispersions in porous media are also investigated. The hydrogel dispersion prepared by RC has lower injection pressure and higher residual resistance coefficient than that of traditional cross-linker.

Imparting Pulley Effect and Self-healability to Cathode Binder of Li-S Battery for Improvement of the Cycling Stability

Imparting Pulley Effect and Self-healability to Cathode Binder of Li-S Battery for Improvement of the Cycling Stability

Hybrid Knot and Knotless Suture Anchor Repair for Patellar Tendon Rupture

Background: Patellar tendon ruptures are the third-most common injury involving the knee extensor mechanism. They typically occur in men under 40 years old as a result of eccentric quadriceps contraction while the knee is flexed and the foot is planted.1 The optimal treatment is surgical repair within 2 weeks of injury to prevent scar formation, degeneration, and loss of tendon excursion. Indications: Operative management is generally indicated for patellar tendon ruptures. In this case, a physically active, healthy 24-year-old man presented with acute pain, extensor lag, and patella alta related to a basketball injury. He was diagnosed with acute patellar tendon rupture/extensor mechanism disruption and indicated for surgery. Technique description: We describe a technique for primary patellar tendon repair which uses both knot-based and knotless suture anchor fixation. Using a pulley effect, sutures in the inferior patellar anchors are used to reduce and repair the patellar tendon back to its bony origin. Patellar anchor-based tapes and a suprapatellar traction suture are affixed with knotless anchors to the proximal tibia to reinforce the repair. Anchor-based suture limbs are used to repair the medial and lateral retinacula. Results: The senior authors’ experience with this technique has been excellent restoration of extensor mechanism function, with rehabilitation permitting early range of motion and no major complications or failures. This patient returned to unassisted activities of daily living between 8 and 12 weeks and had returned to gym workouts and recreational sports at 12 months. Discussion/conclusion: Biomechanical studies have demonstrated that compared with transosseous repair, suture anchor repair decreases gap formation and improves ultimate load to failure. Advantages of suture anchor repair include smaller incision, less tissue dissection, shorter operative time, and improved repair biomechanics. Our technique follows a principle of tendon repair using a high number of suture and tape limbs to span the repair. In addition, this technique incorporates a “double row” of suture anchors and spans the primary repair with a suture and tape “internal brace.” The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Slidable Cross-Linking Effect on Liquid Crystal Elastomers: Enhancement of Toughness, Shape-Memory, and Self-Healing Properties.

The network structures of liquid crystal elastomers (LCEs) are crucial to impart rubbery behavior to LCEs and enable reversible actuation. Most LCEs developed to date are covalently linked, implying that the cross-links are fixed at a particular position. Herein, we report a new class of LCEs integrating polyrotaxanes (PRs) as slidable cross-links (PR-LCEs). Interestingly, the incorporation of a low loading (0.3-2.0 wt %) of the PR cross-linkers to the LCE causes a significant impact on various properties of the resulting PR-LCEs due to the pulley effect. The optimum PR loading is determined to be 0.5 wt %, at which point the toughness and damping behavior are maximized. The robust mechanical properties of the PR-LCE offers a superior actuation performance to that of the pristine LCE along with an excellent quadruple shape-memory effect. Furthermore, the incorporation of PR is useful to enhance the efficiency of shape-memory-assisted self-healing when heating above the nematic-isotropic transition.

Physical Properties of Slide-Ring Material Reinforced Ethylene Propylene Diene Rubber Composites

High-damping rubber composites were prepared by mixing ethylene propylene diene monomer rubber (EPDM) with slide-ring (SR) materials using a two-roll mill, followed by a compression molding technique. SR material has a novel supramolecular structure with unique softness and slidable crosslink junctions. The mechanical strength, thermal stability, compression set property, and damping performance of the composites were investigated. The use of the high damping SR phase dispersed in the EPDM matrix displayed improved physical properties and damping performance compared to those of virgin rubber. As SR content increases in the composites, the damping factor of SR/EPDM blends becomes higher at room temperature. In addition to this, the SR composites showed excellent improvements in the compression set properties. The composites showed a compression set improvement of 35–38% compared to virgin EPDM. These improvements are due to the “pulley effect” of slide-ring materials. Therefore, these materials present a robust platform for making novel elastomer composites for high-performance damping and sealing applications.

A Simple Synthesis Method of Water‐Soluble Pseudo‐Polyrotaxane Cross‐Linkers Based on Cyclodextrin

AbstractCurrently, preparation of polymerizable polyrotaxane cross‐linkers (PCs) or pseudo‐polyrotaxane cross‐linkers (PPCs), including water‐soluble PCs or PPCs requires at least three‐step or more complicated chemical reactions. Herein, a simple and effective method is proposed to prepare two kinds of water‐soluble pseudo‐polyrotaxane cross‐linkers based on cyclodextrin. This means it is more convenient to apply the pulley effect to a wider range of hydrogels. The structures of cross‐linkers are characterized by nuclear magnetic resonance spectroscopy, X‐ray diffraction, and atomic force microscopy. Further, two kinds of pseudo‐polyrotaxane cross‐linkers and conventional cross‐linker are, respectively, copolymerized with acrylamide to prepare hydrogels to compare the properties of hydrogels. The swelling ratios and deformation ability of hydrogel prepared by pseudo‐polyrotaxane cross‐linker are better than that of hydrogel prepared by conventional cross‐linker.

Implementation of the Pulley Effect of Polyrotaxane in Transparent Bulk Polymer for Simultaneous Strengthening and Toughening.

The fascinating pulley effect from moveable α-cyclodextrin (α-CD) based polyrotaxane favors toughening of hydrogels, but the strategy is rarely applied in bulk polymers because of the severe aggregation trend of α-CDs. Herein, the authors propose a simple approach to moderately modify the α-CDs of polyrotaxane by introducing large steric side groups and reactive CC so as to minimize the unwanted hydrogen bonds-induced aggregation of α-CDs and hydrophilicity of polyrotaxane. Accordingly, the proof-of-concept material, poly(methyl acrylate) crosslinked by the modified polyrotaxane, turns out to be rather homogeneous with optical transparency. The polyrotaxane crosslinks are movable under external force as disclosed by in situ small-angle X-ray scattering and other techniques, which is correlated to the relative amount of α-CDs. A few polyrotaxane crosslinkers prove to be sufficient to simultaneously improve strength and toughness of poly(methyl acrylate) owing to the stress equalization. The present work provides an expandable toolbox for enhancing polymers.

Nitrile rubber/sliding graft copolymer damping material with significantly improved strength and damping performance

ABSTRACTNitrile rubber (NBR)/sliding graft copolymer (SGC) composites with significantly improved strength and damping property are successfully prepared. SGC is a novel kind of supramolecular material with sliding crosslink junctions. The micromorphology analyses of NBR/SGC composites indicate that the SGC phase with particle size less than 500 nm is fairly uniformly dispersed in the NBR matrix. As SGC content increases, the loss factors (tan δ) of NBR/SGC composites increase gradually. Specifically, the tan δ of NBR/SGC (100/40) is about 1.2 times higher than that of pristine NBR rubber. The tensile strength and elongation at break of NBR/SGC composites are unexpectedly improved after the addition of SGC. The significantly improved damping performance and tensile strength can be ascribed to the pulley effect of SGC and the strong interfacial hydrogen bonds between SGC and NBR. The high damping performance and good mechanical strength make the NBR/SGC composite a promising high‐performance damping material. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47188.

Highly Stretchable and Instantly Recoverable Slide-Ring Gels Consisting of Enzymatically Synthesized Polyrotaxane with Low Host Coverage

Gels with high mechanical performance have attracted great interest because of their potential biomedical applications. Tough gels reported thus far usually contain sacrificial species to dissipate energy, thus compromising the fatigue resistance. In this study, highly stretchable and recoverable gels can be achieved by cross-linking cyclodextrin (CD)-based polyrotaxane with a low host coverage, synthesized via a one-pot enzymatic end-capping reaction with 90% yield and ∼2% CD coverage (PR02). The low coverage allows the CD cross-links to freely slip on the axis over large distance (∼2/3 of the axis length) and thus allows the PR02 slide-ring network keep intact under large deformation via the pulley effect. The PR02-hydrogel can be stretched up to ∼1600% long, withstand ∼1 MPa stress, and fully recover instantly. PR02-DMSO gels exhibit a shape memory behavior that withstood large deformation. As the first research to control the final property of the network by precisely controlling the slide distance of...

Solving the pulley inclusion problem for a cable-driven parallel robotic system: Extended kinematics and twin-pulley mechanism

For a cable-driven parallel robot system, the robot kinematic models usually assume that the cable connection in the system comprises ideal fixed points on the base and an end-effector. However, the cables are usually guided around pulleys, so the pulley geometry can induce movable connection points when operating the robot system. Some previous studies have addressed the influence of the geometry of the guiding pulleys on the parallel cable robot’s kinematics, and extended pulley kinematics have been proposed by considering the pulley radius. However, the inverse kinematics of the extended pulley kinematics may hinder the implementation of an actual system, especially owing to the real-time computation capacity. Hence, in this study, to solve the pulley kinematic inclusion problem for a cabledriven robotic system and to improve the position control performance, we investigated the actual pulley kinematic effect and we proposed two methods for a fully constrained planar cable robot. Comparison and evaluations based on simulations and experiments using the proposed methods in terms of the end-effector posture demonstrated their validity for solving pulley inclusion problems for a cabledriven parallel robot.

Development of high damping acrylic rubber/sliding graft copolymer composites.

Aiming at fabricating high damping rubber composites, the acrylic rubber ACM was incorporated with sliding graft copolymer (SGC) materials. SGC is a novel supramolecular material with sliding crosslink junctions, and it acts as a high damping phase in ACM/SGC composites. Fourier transform infrared spectroscopy reveals the presence of two types of hydrogen bonds in ACM/SGC composites. Micro-structure analysis shows a clear sea-island phase structure. SGC particles disperse fairly uniformly in the ACM matrix. A wide interphase region exists between these two phases, indicating the good blend compatibility between ACM and SGC. The damping performance of ACM/SGC composites under dynamic shear strain and frequency condition significantly improved with the increase in SGC content. Specifically, the loss factor (tan δ) value of ACM/SGC (100/40) composite increased by 120% compared with that of neat ACM, according to the RPA results. The significantly improved damping property can be ascribed to the interfacial hydrogen bonds and the pulley effect of SGC molecules.