Macromolecular Theory and Simulations最新文献

Lignin, a renewable aromatic polymer, has great potential as a synthetic building block for functional materials. The effects of quaternary ammonic methylation of alkali lignin (AL) on the morphologies and ofloxacin antibiotic (OA) removal application from water are investigated by using the dissipative particle dynamics (DPD) simulation method. Untreated AL can form spherical aggregates, but the phenylpropane units of untreated AL and loaded broad-spectrum OA molecules are randomly distributed in aggregates. However, if quaternary ammonic groups are grafted onto all orthopositions of the phenolic hydroxyl groups (100-QAMAL), then multilamellar spherical aggregates are obtained and OA molecules are entrapped in the aggregates. To prepare multilamellar spherical aggregates with an ordered and regular layered structure, <15 v% of 100-QAMAL and low molecular weights of AL (≈4700–9400 Da) are suggested to be used. Lignin-based multilamellar spherical aggregates can be adopted as potential functional carriers for removing pollutant OA from water.

Solid polymer electrolytes are being explored as replacements for organic electrolytes in lithium-ion batteries due to their less flammable nature and high mechanical strength. However, challenges remain, such as low ionic conductivity, and significant interfacial impedance with electrodes. Understanding the structure and dynamics of ions within polymer electrolytes and near the anode is crucial for enhancing battery performance and safety. In this study, the structural and dynamic properties of lithium cation (Li⁺) and bis(trifluoromethane sulfonyl)imide anion (TFSI⁻) in poly(ethylene oxide) matrix are examined in bulk PEO-LiTFSI electrolyte and in the presence of a graphite surface using molecular dynamics simulations. The findings suggest that the presence of graphite surface does not affect the coordination of oxygen atoms around the Li⁺ ions. Results also show that the dynamics of the ions and ether oxygen is hindered near the graphite surface compared to the region away from the graphite surface.

In order to investigate the effect of rheological parameter of blends on mixing performance of dynamic mixers, the flow of virtual material (VM)/thermoplastic polyurethanes (TPU) with high and low viscosities in it are simulated. The effect of rheological parameter ratios, including zero shear viscosity ratio (η_0VM/η_0TPU), relaxation time ratio (λ_VM/λ_TPU) and non-Newtonian index ratio (N_VM/N_TPU) on pressure drop (Δp), segregation scale (S), and power consumption (P) are analyzed using Taguchi Orthogonal Method, and the effects of rotation speed (n) of the rotor and flow rate ratio (Q_VM/Q_TPU) are studied using single factor method. The results indicate η_0VM/η_0TPU is the most significant factor affecting Δp, S, and P. When η_0VM/η_0TPU = 1, λ_VM/λ_TPU = 1, N_VM/N_TPU = 1, S of blends reach the minimum value. With n increasing, the influences of Q_VM/Q_TPU and viscosity of TPU on S are reduced.

An improved viscoelastic spring lattice model is used to analyze the mechanical properties of polymer composites containing different microstructures, as exemplified by hydroxyl-terminated polybutadiene-based solid propellants. A drop-on-demand structural model is programmed using the C language to simulate the real solid propellant microstructure. The results show that increasing the particle content has a positive effect on the tensile strength of the propellant, but is detrimental to the ductility. The increase in particle size decreases the maximum tensile strength of the material, reflecting the importance of the dewetting process in the microstructure analysis. Finally, the model accurately predicts that initial defects have a destructive effect on the mechanical properties of the material.

Front Cover: Schematic illustration showing the structural inhomogeneities of the interphase in a polymer nanocomposite. The large surface area of aggregates creates adsorbed localized sites at which chains can hardly move and can be viewed as permanent links tying individual aggregates. On a molecular scale, the crystalline and amorphous regions are interconnected by chains that participate in both regions. More details can be found in article number 2400009 by Christian Brosseau.

Neutron spin echo spectroscopy of entangled polymer melts [M. Zamponi, et al. J. Phys. Chem. B 2008, 112, 16220], and of tracer diffusion of short polymer chains in highly entangled polymer melt [M. Zamponi et al. Phys. Rev. Lett. 2021, 126, 187801.] and [M. Kruteva et al. Macromolecules 2021, 54, 11384] found the center-of-mass mean-square displacements at shorter times are subdiffusive, heterogeneous, non-Gaussian, and cooperative. These properties contradict the assumption of reptation within the tube in the tube-reptation (TR) model, but are in accord with the predictions from the many-chain cooperative dynamics in the theory of Guenza. The inadequacy of the TR model revealed by the microscopic experiments and theory motivates the author to reexamine previously published data of diffusion of entangled polymer chains from experiments and simulations used to test the TR model. The results reported in this study lead to the conclusion that the key predictions of the TR model are at variance with experimental and simulation data. The cause lies in the reptation hypothesis contradicting the cooperative nature of entangled chain diffusion proven by its dynamics being isomorphic to cooperative diffusion in other materials. The Coupling Model has predictions consistent with the cooperative diffusion properties in interacting materials [Prog. Mater. Sci., 2023, 139, 101130.]. Applied to the entangled polymers, the predictions successfully explain the data, especially those contradicting the TR model. Thus, diffusion of entangled polymer chains is a cooperative many-chain process in having the universal properties of many-body cooperative diffusion established in many other interacting materials, and the reptation hypothesis is unwarranted.

The double quench phase separation is a simplified type of continuous cooling process that is widely seen in industrial processes for polymeric membrane formation. Uncommon quenching conditions can lead to the creation of novel membrane microstructures. This study aims to theoretically investigate the impact of nonisothermality on the morphology formation during the double-quench thermally-induced phase separation process. First, quench is employed during different stages of phase separation to observe the possibility of secondary morphology formation. Next, two initial quench temperatures are selected, one shallow and the other deep. The initial solution temperature and the secondary quench temperature are kept constant to inspect the impact of the initial quench temperature on the structure formation. Lastly, the results of the secondary quench are compared with and without employing the enthalpy of demixing. Results verified that the stage of phase separation, the initial and secondary quench temperatures, cooling rate, and the secondary quench composition are the most important parameters in the the nonisothermal double quench phase separation process. The morphology should be well-developed in order for the secondary structure formation. In addition, it is shown that heat generation during demixing in the primary and secondary quenches significantly influences the secondary morphology formation.

Swelling experiments are conducted on nonfiller natural rubber using four solvents (toluene, cyclohexane, tetrahydrofuran (THF), and methylethylketone (MEK)) over temperatures from 10 to 70 °C. Toluene, cyclohexane, and THF, classified as effective solvents, show swelling ratios between 3 and 7, influenced by the crosslink density of the rubber. MEK, however, has a lower ratio of 1.5 to 2. Temperature has a minor impact on swelling compared to the crosslink density. The study evaluates the Extended Modified Double Lattice (EMDL) model for its mixing contribution in polymer network swelling, aiming to improve the Flory–Hüggins (FH) model. The superiority of EMDL above FH is in the boundary condition at the unvulcanized state, the former aligning its interaction energy with values from solvent activities in primary linear polymer/solvent solutions, unlike the FH model. The EMDL model also accounts for oriented interactions in polar solvents through a secondary lattice, linking specific interaction energy with solvent dipole moments. The study observes a nonlinear correlation between crosslinking density and sulfur amount, proposing a nonrandom mixing at lower sulfur concentrations. This model shows strong alignment with experimental data, suggesting that replacing the FH model's mixing contribution with the EMDL model could improve results with minimal additional complexity.

The coating process is widely used in various industries to enhance the production quality and efficiency. This study gives a comprehensive analysis of non-isothermal blade coating of non-Newtonian nanofluid incorporating magnetic, thermophoresis, and Brownian effects. The mathematical equations derived from mass, momentum, and energy conservation laws are initially streamlined by means of lubrication approximation theory (LAT). Subsequently, these dimensionless equations are solved in dimensionless form numerically using fourth order Runge–Kutta and Newton–Raphson methods. This study includes the effects of the slip parameter, magnetohydrodynamic (MHD) and other material parameters on the coating thickness ($�h_1$), blade load, velocity, temperature, concentration, and pressure profiles through graphs and tables. The velocity of molten polymer increases near the substrate while it decreases near the blade surface as the slip parameter increases. The temperature distribution increases as the Brinkman number rises, with the maximum temperature occurring in the nip region of the flow. The coating thickness and load-carrying force for both plane and exponential coater increase with higher values of the magnetohydrodynamic (MHD) parameter.