Movement Of Molecular Chains Research Articles

Review on Crystallization Strategies for Polymer Single Crystals

Polymer physics has evolved significantly over the past century, transitioning from the early recognition of the chain structure of polymers to a mature field integrating principles from statistical mechanics, thermodynamics, and condensed matter physics. As an important part of polymer physics, polymer single crystals are crucial for understanding molecular structures and behaviors, enhancing material properties, and enabling precise functionalization. They offer insights into polymer crystallization kinetics, serve as templates for nanofabrication, and have applications in electronics, sensors, and biomedical fields. However, due to the complexity of molecular chain movement, the formation of polymer single crystals is still very difficult. Over the decades, numerous researchers have dedicated themselves to unraveling the mysteries of polymer single crystals, yielding substantial findings. This paper focus on the historical evolution and advancements in polymer single crystal research, aiming to offer valuable insights and assistance to fellow researchers in this field.

Effect of Interfacial Modification on the Low-Temperature Fatigue Properties of Polymer/MXene Flexible Pressure Sensors.

Maintaining an excellent force-electric response under cyclic bending at low temperatures is still challenging for resistive-type electrically conductive polymer composite-based pressure sensors. In this study, the effect of low temperature on the fatigue failure of flexible MXene/polymer pressure sensors was systematically investigated through the silane functionalization of MXene nanosheets embedded with different polymer matrixes. The results show that the MXene/polymer interfaces are the primary factors affecting the temperature-dependent bending fatigue of the Cu/MXene/polymer/Cu sensor. Using finite element analysis and theoretical calculations, we reveal that the MXene/polymer interfaces are affected by free volume changes and the molecular chain motion under different temperatures. At room temperature, the well-distributed free volume in the polydimethylsiloxane (PDMS) matrix permits local segmental mobility that promotes the affinity between the polymer and MXene. As the temperature decreases, the free volume in the matrix shrinks with less space left for molecular chains to slide relatively, weakening the polymer/MXene interfacial bonding strength. However, for PDMS/MXene sensors with the interface modified using the silane coupling agent KH550, the nanoconstrained structure formed by strong hydrogen bonds and covalent bonds at the PDMS/MXene interface can hinder the mobility of polymer chains, which greatly helps to dissipate the inter/intrachain friction. It thus alleviates the debonding energy dissipation during cyclic bending at subzero temperatures.

The effect of boron carbide doping content on the mechanical properties of polyethylene

ABSTRACT This paper presents Martin Buber‘s unpublished manuscript ‘Fragen und Antworten. Die jüdische Besiedlung Palästinas’ in the original German with English translation and contextualizes it within the main stations of Buber‘s Zionist thinking: cultural Zionism, religious Zionism, and Zionism of realization. It problematizes Buber‘s reflection on Jewish settlements in Palestine with reference to the significance of Zionism for humanity as well as the possibility of reconciliation between Jews and Arabs in the Middle East. It also addresses the problem of Jewish terror, framing it in correlation with the restrictions on Jewish migration to Palestine and the catastrophe of the Shoah.

Effect of viscosity and thermal properties on mechanical properties of PLA materials

Mechanical properties are regularly motivated by the physical and chemical properties of materials. Fundamentally, they are determined by molecular weight, the movement of molecular chains and the interaction between molecules. As we all known, thermal properties (the glass transition temperature, the melting and cooling temperatures) and rheological property (viscosity) are influenced by these factors as well. Therefore, there should be specific relationship between them. In this work, we employed three kinds of materials: PLA3051D, PLA3052D and PLA4032D to scrutinize the relationship between mechanical properties and thermal properties, mechanical properties with rheology property. In agreement with the results, the effect of thermal properties and viscosity on mechanical properties are exhibited to mathematical equations.

Mesoscopic conductivity and trap distribution characteristics in the interfacial region of polypropylene/MgO nanocomposites with high energy storage density

Polymer dielectric materials are crucial for storage devices in power and electronic systems, as well as electric vehicles, due to their high energy density and fast discharge rates. Polymer nanocomposites (PNCs) possess superb electrical and energy storage properties, making them highly promising as next-generation thin-film dielectrics for energy storage. The excellent performance of PNCs derive from the interfacial region introduced by nano-doping. However, the current measurement equipment and technology make it difficult to accurately obtain the mesoscopic scale distribution characteristics of the conductivity of the interfacial region, and are also impossible to clarify the formation mechanism of deep traps in the interfacial region. We employed high-throughput simulation and experiment to investigate the mesoscopic conductivity and trap distribution properties of the interfacial region in PNCs. Furthermore, we developed a three-dimensional mesoscopic conductivity distribution simulation model of PNCs containing polymer matrix, nanoparticles, and interfacial region. The interfacial region size and conductivity distribution of the PNCs were determined by comparing with the experimental results, and the mesoscopic distribution characteristics of the interfacial traps in PNCs were obtained. It is proved that the nanofillers form a condensed structure with high order and compactness by restraining the movement of molecular chains, which deepens the trap energy in the interfacial region and restricts the free volume expansion. This results in the formation of interfacial regions with low conductivity, contributing to enhancing energy storage performance.

Carboxyl-modified nanocellulose (cNC) enhances the stability of cNC/pullulan bio-nanocomposite hard capsule against moisture variation

The quality of polysaccharide-based films and hard capsules is often affected by changes in relative humidity, manifesting as unstable water content, and changes in mechanical strength that make them brittle or soft. Herein, carboxyl-modified nanocellulose (cNC) was prepared and used as a new component to successfully improve the moisture resistance of cNC/pullulan/high-acyl gellan bio-nanocomposite hard capsules (NCPGs). Homogenously dispersed cNC in the pullulan/high-acyl gellan matrix could render the formation of more hydrogen bonds that provided additional water-binding sites and limited the free movement of pullulan and high-acyl gellan molecular chains within NCPGs. This contributed to a decreased amount of pooling adsorption water and an increased amount of Langmuir adsorption water in NCPGs, as compared to pullulan/high-acyl gellan hard capsules (PGs) without cNC. Therefore, the equilibrium moisture content (EMC) values of NCPGs decreased at 83 % relative humidity and increased at 23 % relative humidity compared to those of PGs. Together with enhanced mechanical and barrier properties, NCPGs effectively protected encapsulated amoxicillin and probiotic powder from changes in the outside humidity. Additionally, NCPGs exhibited faster drug release. This study presents a new mechanism and strategy for fabricating films and hard capsules with enhanced stability against moisture variation.

Effect of water-induced changes in molecular structure and vapor pressure on the heterogeneous hygrothermal degradation of konjac glucomannan

The heterogeneous hygrothermal degradation (HHTD) method can simply and efficiently prepare depolymerized konjac glucomannan (KGM). The degradation rate was significantly improved when the KGM powder moisture was below 20%, but basically no longer increased after the moisture was above 20%. This study systematically examined the influence of the initial moisture content of powder on the molecular structure of KGM and the vapor pressure of degradation system to elucidate the association of these changes with hygrothermal degradation. The results indicated that with the increase of powder moisture, the disorder of KGM amorphous region increased dramatically, and the ordering degree of aggregate structure decreased. Water notably enhanced the freedom of KGM molecular chain motion by reducing the intermolecular hydrogen bond interaction and expanding the free volume. Furthermore, powder moisture markedly promoted the degradation of KGM by increasing the vapor pressure and mass transfer rate of the closed degradation system. The system reached saturated vapor pressure when the moisture content was above 20%. Consequently, the synergistic effect of the water-induced changes in KGM molecular structure and system vapor pressure significantly accelerated the hygrothermal degradation rate of KGM. The promotion effect of powder moisture on degradation reached the upper limit when the moisture content was higher than 20%, thus moderately solvated KGM-20% powder can achieve an efficient hygrothermal degradation effect. This work is expected to provide theoretical bases for the industrial application of HHTD as a controllable and efficient degradation method of KGM.

Investigation of the Microstructure of PAN Precursor Fibers Obtained at Various Processing Stages

The production of high-performance carbon fibers relies heavily on the structural transformations of polyacrylonitrile (PAN) fiber during processing. In this article differential scanning calorimetry (DSC), synchrotron small-angle X-ray scattering (SAXS), and synchrotron wide-angle X-ray diffraction (WAXD) were used to study the changes of the thermal properties, voids and crystal structure of the PAN precursor fibers on industrial lines during the continuous processing stages, i.e., after the treatment in the coagulation bath, after stretching in boiling water and after stretching in high-temperature steam. The findings of this study suggest that after boiling water stretching the molecular chain motion of the PAN precursor fiber weaken, resulting in the expansion of the voids. After high-temperature steam stretching the voids became elliptical and oriented in the stretching direction. Although the boiling water stretching process partially damaged the (100) crystal planes of the PAN precursor fibers, it does not hinder their overall crystalline structure. The high stretching ratio primarily affected the orientation of the molecular chains. This orientation, even in the context of partial crystal plane disruption, further promoted the crystallization of the (100) crystal planes in the fibers. These experiments explored the correlation between the processing technology and fiber structure transformation of PAN-based carbon fibers, resulting in producing a guide for the preparation of high-performance carbon fibers with fewer defects.

Hydrophobic Cross-Linked Chains Regulate High Wet Tissue Adhesion Hydrogel with Toughness, Anti-hydration for Dynamic Tissue Repair.

Hydrogel adhesion materials are widely reported for tissue engineering repair applications, however, wet tissue surface moisture can reduce the wet-adhesion properties and mechanical strength of hydrogels limiting their application. Here, anti-hydration gelatin-acrylic acid-ethylene dimethacrylate (GAE) hydrogels with hydrophobic cross-linked chains are constructed. The prepared GAE hydrogel is soaked in PBS (3 days) with a volume change of 0.6 times of the original and the adhesive strength, Young's modulus, toughness, and burst pressure are maintained by ≈70% of the original. A simple and universal method is used to introduce hydrophobic chains as cross-linking points to prepare hydrogels with anti-hydration, toughness, and high wet state adhesion. The hydrophobic cross-linked chains not only restrict the movement of molecular chains but also hinder the intrusion of water molecules. Antihydration GAE hydrogels exhibit good biocompatibility, slow drug release, and dynamic oral wet-state tissue repair properties. Therefore, the anti-hydration hydrogel has excellent toughness, wet tissue adhesion properties, and good prospects for biological applications.

Preparation of solvent-resistant polyimide membranes for efficient separation of dyes and salts via an “internal drive” strategy

It is extremely difficult to separate salts and dyes from high-salinity printing and dyeing wastewater. In this study, modified montmorillonite (EPTAC-CD-MMT) was obtained by intercalation of 2,3-epoxypropyltrimethylammonium chloride (EPTAC) modified cyclodextrin (CD). PI/EPTAC-CD-MMT membrane was prepared by blending EPTAC-CD-MMT with polyimide (PI). The addition of EPTAC-CD-MMT could inhibit the motion of PI molecular chains and increase the solvent resistance of the membrane. Additionally, EPTAC-CD-MMT exhibited spontaneous “internal drive” during the phase transition and segregated to the membrane surface. The pore structure of the membrane was adjusted to a well-developed “side pore” structure. Thus, solvent-resistant membranes for dye/salt separation with high flux were finally obtained. The successful modification of MMT was demonstrated by FTIR, XRD, TGA and XPS. EDX and SEM were used to characterize the surface segregation phenomena and well-developed pore structures of the membranes. When EPTAC-CD-MMT was added at 3 wt%, the membranes showed a significant increase in pure water flux (138.0 L·m−2·h−1·bar−1), high dye rejection (>98.5 %), low salt rejection (<10.0 %), and good solvent resistance in six organic solvents. This demonstrated the potential of PI/EPTAC-CD-MMT separation membranes for the treatment of dye wastewater containing sophisticated organic solvents.

Substantial improvement of thermal conductivity and mechanical properties of polymer composites by incorporation of boron nitride nanosheets and modulation of thermal curing reaction

AbstractThermal conductive polymer‐based composites synchronously with stable dielectric and excellent mechanical properties are urgently needed for high‐temperature‐resistant electronic devices. Here, a significant improvement in the thermal conductivity (TC), thermal stability, dielectric, and mechanical performance was simultaneously achieved in the polyarylene ether nitrile (PEN)/divinyl siloxane‐bisbenzocyclobutene (BCB) matrix through the incorporation of boron nitride nanosheets (BNNS) combined together with the post‐solid phase chemical reaction technique. The significant increase in the effective filler‐filler and filler‐crystal contacts in the composites was the main reason for the improvement in TC and dielectric constant. Besides, glass transition temperature (Tg) and mechanicals were enhanced in the presence of cross‐linked networks. By synchronously adding 15 vol% BNNS, the TC of composites after treatment reached up to 5.582 W/m.K, enhanced by 4.4 times higher than untreated. The dielectric constant was down to 2.93 at 1 MHz and the loss remained at a relatively low level. Meanwhile, the composite showed significantly enhanced thermal stability, mechanicals, and hydrophobicity (Tg = 336°C, T5% = 529°C, tensile strength and modulus was 94.5 MPa and 5.3 GPa, respectively, the contact angle was 101.76°). Thus, it promotes an effective strategy for fabricating a high‐performance‐polymer composite, which has the potential used in electronic materials.Highlights Crystallization‐crosslinking strategy optimizes overall performance. Crystals fill gaps between BNNS layers and connect thermal conductive pathway. Crosslinked networks limit molecular chain motion to reduce phonon scattering. The highest TC of the PEN/BCB/BNNS composite is up to 7.451 W/m.K. Thermal property shows significant improvement after crosslinking especially Tg.

Facile, catalyst-free, and high enthalpy PEG-based phase change composite for use in photothermal conversion and waste heat recovery

The poor shape stability, low thermal storage density, and complex process confronted in fabricating high-performance phase change composites (PCCs) via the chemical cross-linking technology. Herein, PEG-based shape stability PCC (SSPCC) with high enthalpy and good shape stability was obtained using a facile one-pot method without additional catalysts. The reliable three-dimensional cross-linked structure formed by the interaction of epoxy resin and curing agent binds the movement of PEG molecular chains, which simultaneously in coupled with the stronger hydrogen bonding between PEG and cross-linked products to endow the as-prepared SSPCC with excellent shape stability, thermal stability, durability, and high thermal storage density (160.8 J/g). Moreover, the Raman spectra clearly presented the interaction force and phase morphology distribution between PEG and the skeleton structure. SSPCC with the high relative enthalpy efficiency and melt enthalpy can play an essential role in photothermal applications, while the facile manufacturing process free from additional organic solvents or high temperature, highlighting its green and sustainable features. Additionally, the photothermal transport and thermostatic effects of the SSPCCs show great potential for application in waste heat recovery, which can maintain higher temperatures for a long time. Totally, such SSPCC with reliable and distinguished phase change properties ensure a wide range of potential applications, while the easy-to-prepare and low-cost fabrication method provides an inspiring strategy for alternative SSPCC development.

Lotus starch/bamboo shoot polysaccharide composite system treated via ultrasound: Pasting, gelling properties and multiscale structure

This study investigated the effects of ultrasound treatment on the physicochemical properties, digestion properties, and multiscale structure of a lotus root starch (LS) and bamboo shoot polysaccharide (BSP) composite system. It also preliminarily revealed the mechanism underlying the modification effect of ultrasound treatment. After 180–360 W ultrasound treatment, the viscosity, thixotropy, and gel viscoelasticity of the LS/BSP paste increased. However, treatment with the ultrasound power of 540 and 720 W decreased viscoelasticity. After 14 days of retrogradation, the hardness and cohesiveness of the LS/BSP gel increased under 180 and 360 W ultrasound treatment but decreased under 540 and 720 W ultrasound treatment. After 540 W ultrasound treatment, RDS content decreased by 17.2 % and resistant starch content increased by 32.5 %. After 180 min of in vitro digestion, the hydrolysis rate of LS/BSP decreased from 97.82 % to 93.13 % as the ultrasound power increased to 540 W. Ultrasound promoted the uniform dispersion of BSP in the starch paste and the movement, orientation, rearrangement, and aggregation of starch and BSP molecular chains. These effects further enhanced the interaction between BSP and starch, resulting in the formation of a dense paste structure with strong resistance to digestive enzymes. This work revealed the mechanism of the effects of ultrasound treatment on LS/BSP and found that 360–540 W ultrasound treatment could improve the physicochemical properties and digestion properties of LS/BSP.

Characterization of material degradation mechanism of carbon fiber reinforced epoxy resin composites under ultraviolet radiation and salt‐fog synergistic environment

AbstractThe influence of harsh environment conditions on carbon fiber reinforced polymer composites (CFRP) restricts their popularization and usage in outdoor marine applications. Although many studies have been conducted on the service characteristics of CFRP under different conditions, the effect of ultraviolet (UV) radiation and salt‐fog synergistic aging has not been researched in detail. The primary focus of this work is to understand the aging degradation mechanism and mechanical response of CFRP in this harsh environment. The test samples were exposed to UV and salt‐fog synergistic environment. Then the physicochemical properties, dynamic/static mechanical behavior of all samples were characterized. The results show that the CFRP exposed to UV and salt‐fog environment represent noticeable synergistic aging effects. The matrix plasticization and particle washing caused by UV radiation and water condensation will intensify the erosion effect of chloride ions, thus leading to significant deterioration of the fiber‐matrix interface and interlaminar bonding. After aging, the deformation resistance of the material reduces, the molecular chain movement intensifies, the cross‐linking density of the resin matrix decreases, and the maximum decline of glass transition temperature reaches 32.36%. Compared with the tensile performance, the degradation of interlaminar shear performance is more serious, of which the interlaminar shear performance are mainly determined by the matrix and interlaminar properties. Besides, for the aged samples, more serious irreversible deformation appears during the loading process.Highlights The CFRP shows noticeable synergistic aging effects under UV and salt‐fog aging, which the matrix plasticization and particle washing caused by ultraviolet radiation and water condensation will intensify the erosion effect of chloride ions. The decrease of the cross‐linking density of CFRP materials is the primary cause for the deformation resistance reduction and properties degradation. Compared with the tensile performance, the degradation of interlaminar shear performance is more serious.

Ladderlike Polyphenylsesquioxane‐Doped Cellulose Insulation Paper with Upgraded Mechanical Strength

Ladderlike polyphenylsesquioxane (L‐PPSQ) with special planar ladder structure is significant to upgrade the mechanical strength of cellulose insulation paper. In this study, the effect of different content of L‐PPSQ on mechanical properties and dielectric properties of cellulose is first investigated by molecular simulation, and then insulation paper doped with L‐PPSQ is prepared for experimental verification. It is indicated in the simulation results that the elastic modulus, bulk modulus, and shear modulus of the cellulose are enhanced up to 36.82%, 27.96%, and 41.80%, respectively, when L‐PPSQ is added at 3 wt%, and the cellulose model with 3 wt% L‐PPSQ possesses the lowest dielectric constant. The reason is that L‐PPSQ can enhance the hydrogen bonding network of cellulose, weaken the degree of molecular chain motion, and strengthen the strength of molecular chains, which in turn manifests as the enhancement of mechanical strength. It is shown in the experimental results that the tensile strength and elongation at break of the composite insulation paper can be enhanced by 16.7% and 35.09% when the L‐PPSQ content is 3 wt%, which is consistent with the simulation results. The short‐term aging test shows that L‐PPSQ can also upgrade the mechanical strength of the insulation paper at high temperatures.

Constraining effects on polymer chain relaxation in crosslinked supramolecular dual networks

Polymer networks containing transient physical and permanent chemical cross-links exhibit unique mechanical properties due to the intrinsic reassociating ability of supramolecular functional groups. Similar to supramolecular gels, these networks allow the controlled release of stored energy and can extend the life of polymer networks in practical applications. In this study, we investigated the rheology, dielectric spectroscopy, stress–strain behavior, and dynamic mechanical analysis of networks based on long polybutylene oxide (PBO) chains functionalized with randomly placed thymine (Thy) side groups. A transient network was formed by proportionally mixing this matrix with short non-entangled linear 1,3,5-diaminotriazine (DAT) head–tail modified PBO chains, exploiting the hetero-complementarity of the DAT–Thy triple hydrogen bond. This transient polymer network was further cross-linked to a dual network via a thiol-ene click reaction to form static covalent bonds. In PBO, the similar polarity of the PBO matrix and the DAT–Thy functional groups ensures that the molecular chain motion is not affected by segregation, resulting in a homogeneous polymer phase without microphase-separated functional group domains. Dielectric relaxation spectroscopy was combined with rheology to quantify the relaxation processes of the interconnected polymers and the strength of the DAT–Thy bonding interactions in the melt. The results showed two distinct plateaux in the relaxation modulus due to contributions from hydrogen and permanent bonds. In the case of the dual network, the lifetime of the hydrogen bond was prolonged and higher activation energy was observed due to the physical cross-link preventing the movement of the long chain.

Enhanced cycle loading stability of shock transmission units via adjusting boron content of polyborosiloxanes

Polyborosiloxanes (PBSs)-based shock transmission units (STUs) play a vital role in the seismic resistance of the bridge due to the large output damping force and simple structure without the use of a valve structure. However, Dow Corning 3179 (DC3179)-based STU had poor locking performance under cyclic loads and filling processability due to excessive viscosity, which was unfavorable for engineering applications. In order to achieve the locking of the PBS-based STUs with low complex viscosities of PBSs under cyclic loading, three PBSs with different boron content were synthesized via the reaction of hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and boric acid (H3BO3). The results showed that the variation of the silicon-boron ratios would affect the complex viscosity, storage modulus, and loss modulus. The essence is that the formation of a non-bonding crosslink between boron atoms with vacancies and oxygen atoms with lone electron pairs in adjacent chains affects the movement of molecular chains. PBSs with low complex viscosity and high storage modulus were prepared by adjusting the silicon-boron ratios, which could enhance the cyclic loading stability of PBS-based STUs.

New insights into the effects of starch-oleic acid-chlorogenic acid interactions on structural formation by hot-extrusion 3D printing: From perspective of nonlinear rheology

Nonlinear rheology can be used to monitor the molecular chain movement of polymer materials under large strain conditions. In this work, we firstly set up large amplitude oscillatory shear (LAOS) conditions simulating the hot-extrusion 3D printing (HE-3DP) process and attempted to match the structural formation of wheat starch (WS) by starch-oleic acid (OA)-chlorogenic acid (CA) interactions during HE-3DP from perspectives of nonlinear rheology. Results showed that when compared with WS system, the b value and zero-strain nonlinearity (Q0) of WS-OA system increased with OA addition, and it exhibited obvious strain hardening and shear thinning behaviors, which were ascribed to that OA interacted with starch to form single helix and V-type crystalline structure through hydrophobic force, and it obstructed the integrality of gel network. For WS-CA system, the b value and Q0 decreased with CA addition and the shear thickening behavior was increased which could be explained that CA interacted with starch chains through hydrogen bonding following the formation of aggregates structure, thus improving the integrity of network structure. Notably, when compared to above two binary systems, the early emergence of strain thickening and the weakening of strain stiffening for WS-OA-CA system declared that CA contributed to inhibiting the aggregation and assembly of the single helix formed by WS-OA interactions. Overall, this study provided important information for the application of nonlinear rheology in the structure evolution of starch system during HE-3DP.

PEO-based solid-state electrolyte modified by cationic covalent organic frameworks enabling high-performance all-solid-state Li metal and graphite anode batteries

Covalent organic frameworks (COFs) with regular and ordered channels have been proved that they could offer extra space to accommodate ions and fast conduction pathways for ion motion. However, the ion conductivities of their own are not high because of most of them have no enough active segmental motion of polymer chains for ion transport. Polyethylene oxide (PEO) is the most typical and efficient solid-state polymer material for Li+ migration by the segmental motion of molecular chains. Herein, we propose a simple and effective strategy of introducing a small quantity of cationic COF additive EB-COF-TFSI into the PEO of low glass transition temperature to obtain high-performance solid-state electrolyte (SSEs) and Li batteries. The cationic COF structure not only provides fast pathway for Li+ but also these cations on it accelerate Li salt dissociation and Li+ conduction. As a result, the cycling time of Li symmetrical cells increases to triplication at a same test condition; the corresponding all-solid-state LFP and NMC//Li metal cells are stimulated to release higher specific capacities, exhibit an enhanced cycling stability and better rate capability. It is surprising that all-solid-state LFP//graphite cells show excellent charging and discharging performance no matter on longtime cycling or rate performance test which are both much better than that of Li metal cells and provide a great strategy for building commercial all-solid-state Li battery based the current structure of it.

Effect of Cross-Linking Density on Non-Linear Viscoelasticity of Vulcanized SBR: A MD Simulation and Experimental Study.

In recent years, there has been a growing interest in changes in dynamic mechanical properties of mixed rubber during dynamic shear, yet the influence of vulcanized characteristics on the dynamic shear behavior of vulcanized rubber, particularly the effect of cross-linking density, has received little attention. This study focuses on styrene-butadiene rubber (SBR) and aims to investigate the impact of different cross-linking densities (Dc) on dynamic shear behavior using molecular dynamics (MD) simulations. The results reveal a remarkable Payne effect, where the storage modulus experiences a significant drop when the strain amplitude (γ0) exceeds 0.1, which can be attributed to the fracture of the polymer bond and the decrease in the molecular chain's flexibility. The influence of various Dc values mainly resides at the level of molecular aggregation in the system, where higher Dc values impede molecular chain motion and lead to an increase in the storage modulus of SBR. The MD simulation results are verified through comparisons with existing literature.