Macromolecular Theory and Simulations最新文献

Coating techniques are broadly used in the production of sticky tapes, plastic films, books, wallpapers and magazines, adhesive tapes as well as the textiles and metals preservation, packaging, materials protection and X-ray films. The modeling of roll-over web coating technique is investigated to report the magneto-hydrodynamic (MHD) viscous hybrid nanofluid impact on the final coating thickness. In the coating industry, the application of nanomaterial over the sheet/substrate has better non-Newtonian like rheological features as opposed to the ordinary fluid. The dimensionless governing equations are reduced using lubrication approximation theory (LAT) and the exact solutions for velocity and pressure gradient are acquired. To find the flow rate, coating thickness and other mechanical quantities, numerical technique is utilized. The graphs and tables briefly study the impacts of hybrid nanomaterial volume fraction and Hartmann number on the flow and engineering quantities in detail. Hybrid nanomaterial volume fraction under MHD results in higher shear stress and pressure profile, which triggers decline in coating thickness, which may help in achieving efficient coating process and protecting the substrate life.

Blade coating is a process in which a fluid is applied to a surface using a fixed blade, offering economic benefits over other coating techniques. It is commonly employed in paper production, information preservation, and the manufacturing of photographic films and magnetic storage devices. This article explores the non-isothermal blade coating process using the Bingham plastic fluid model with non-linear slip effects. The 2D incompressible flow in the blade coating process is modeled with conjunction of the continuity, momentum, and energy equations. The modeled flow equations are converted into the dimensionless using dimensionless variables and parameters. The simplified non-linear differential equations are solved numerically using boundary value problem fourth order collocation (bvp4c) method. This work explores how changes in physical parameters affect flow characteristics and mechanical properties of the blade coating process are investigated with the help of various graphs and tables. It is observed that the pressure and velocity of the molten polymer increase with increasing the values of the Bingham plastic parameter. It is also observed, when the value of the slip parameter is ($��\gamma �=�0.8�)�,�$ the coating thickness increased by 41.6279% (for plane coater) and 53.4030% (for exponential coater), and blade load force decreased by 14.2272% (for plane coater) and 15.0107% (for exponential coater) form the Newtonian values.

This review discusses methods for calculating the equilibrium interfacial tension in strongly immiscible polymer blends compatibilized with copolymers. The discussion is focused on typical polymer blends with fine phase structures; in these polymer blends, the volume of the interfacial layer is generally not negligible with respect to the volume of the bulk phases. The main models and calculation procedures that are predominantly used are compared, and their practicalities are discussed. Neither the expressions derived using the dry brush approximation nor those derived using the wet brush approximation are applicable to blends compatibilized with copolymers that have block lengths comparable to those of the compatibilized homopolymers. The amount of a copolymer in the interfacial layer of a polymer blend is generally not negligible with respect to its amount in the bulk phases. Therefore, approximations that are successfully used for the calculation of the interfacial tension measured by common methods cannot be applied to calculation of the interfacial tension in the polymer blends.

The behavior of (athermal) mobile doubly tethered polymers (ring-like in 3D) is investigated, on a 2D substrate using the bond fluctuation model. The end-monomers can move laterally within a constrained distance range. Conformational properties of loop polymers are analyzed and specifically the ordering of the 2D system of end-monomers. For this, the director is considered between the end-monomers for local ordering. As tethering density increases, a transition from mushroom-like conformations to nearly upright structures is observed, as is the case for linear grafted polymers. The effects of loop repulsion are explored, i.e., entropic repulsion, and tethering density on the order parameter and orientational correlations of the directors in 2D. Despite the lack of a global phase transition, local orientational order emerges in 2D due to loop interactions in 3D.

In the present work, a phenomenological model built to represent the suspension polymerization of vinyl chloride in a continuous oscillatory baffled reactor is presented for the first time. Following a previous work (Silva et al., Chemical Engineering Science, 288, 119845, 2024), a tanks-in-series model is employed to represent the reactor and a backflow stream is also considered to simulate backmixing. The intrinsic heterogeneous behavior of vinyl chloride polymerization adds model complexity in comparison to vinyl acetate polymerization reported in the literature. Moreover, the stronger gel effect also makes the temperature control difficult since a higher number of cooling jackets is required to keep a uniform temperature profile. The influence of residence time on reactor operation is investigated. Furthermore, the effects of initiator type and injection points on the polymerization rates and polymer properties are evaluated and shown to influence the process operation significantly.

Utilizing ionic liquids in proton exchange membranes can greatly enhance the performance of fuel cells, enabling their application in high-temperature and dry conditions. Further advancements in this field depend on a fundamental comprehension of their structural characteristics. This study focuses on the sulfonated poly(ether ether ketone) (SPEEK)-1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIm][OTf] composite membrane system. Effects of sulfonation degree, ionic liquid content, and temperature on the structure and conductivity of the composite membrane are investigated by dissipative particle dynamics (DPD) and molecular dynamics (MD) simulations. Results show that [BMIm][OTf] is predominantly distributed around the sulfonic acid groups of SPEEK. At an optimal sulfonation degree and ionic liquid content, interconnected ionic liquid channels can be formed. Nevertheless, an excessively high sulfonation degree may jeopardize the stability of the membrane structure. Moreover, the aggregation of ionic liquid occurs at a high level of ionic liquid content, which hinders the efficient transfer of protons. Generally, increasing the temperature is more conducive to the formation of monodisperse ionic liquid channels within the SPEEK-[BMIm][OTf] composite membrane; however, overhigh temperature may compromise the integrity of the composite membrane structure. The findings of this study offer molecular insights for the development of high-temperature proton exchange membrane fuel cell systems.