AI Article Synopsis

  • The text presents a derivation of a simple hydrodynamic two-fluid model that describes phase separation in non-entangled polymer solutions with viscoelastic effects, grounded in a clear molecular framework.
  • The model is based on a free-energy functional and adheres to thermodynamic principles, incorporating both conservative and dissipative dynamics consistent with the second law of thermodynamics.
  • It comprises momentum conservation and convection-diffusion equations, treating hydrodynamic and macromolecular dynamics on the same level, leading to a new rheological constitutive equation distinct from the Oldroyd-B model.

Article Abstract

We present a detailed derivation of a simple hydrodynamic two-fluid model, which aims at the description of the phase separation of non-entangled polymer solutions, where viscoelastic effects play a role. It is directly based upon the coarse-graining of a well-defined molecular model, such that all degrees of freedom have a clear and unambiguous molecular interpretation. The considerations are based upon a free-energy functional, and the dynamics is split into a conservative and a dissipative part, where the latter satisfies the Onsager relations and the second law of thermodynamics. The model is therefore fully consistent with both equilibrium and non-equilibrium thermodynamics. The derivation proceeds in two steps: firstly, we derive an extended model comprising two scalar and four vector fields, such that inertial dynamics of the macromolecules and of the relative motion of the two fluids is taken into account. In the second step, we eliminate these inertial contributions and, as a replacement, introduce phenomenological dissipative terms, which can be modeled easily by taking into account the principles of non-equilibrium thermodynamics. The final simplified model comprises the momentum conservation equation, which includes both interfacial and elastic stresses, a convection-diffusion equation where interfacial and elastic contributions occur as well, and a suitably convected relaxation equation for the end-to-end vector field. In contrast to the traditional two-scale description that is used to derive rheological equations of motion, we here treat the hydrodynamic and the macromolecular degrees of freedom on the same basis. Nevertheless, the resulting model is fairly similar, though not fully identical, to models that have been discussed previously. Notably, we find a rheological constitutive equation that differs from the standard Oldroyd-B model. Within the framework of kinetic theory, this difference may be traced back to a different underlying statistical-mechanical ensemble that is used for averaging the stress. To what extent the model is able to reproduce the full phenomenology of viscoelastic phase separation is presently an open question, which shall be investigated in the future.

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-648X/ac0d17DOI Listing

Publication Analysis

Top Keywords

phase separation
12
viscoelastic phase
8
model
8
degrees freedom
8
non-equilibrium thermodynamics
8
interfacial elastic
8
systematic derivation
4
derivation hydrodynamic
4
hydrodynamic equations
4
equations viscoelastic
4

Similar Publications

Technologies for studying phase-separated biomolecular condensates.

Adv Biotechnol (Singap)

March 2024

Guangdong Provincial Key Laboratory of Pharmaceutical Functional Genes, MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, GuangZhou, GuangDong, China.

Biomolecular condensates, also referred to as membrane-less organelles, function as fundamental organizational units within cells. These structures primarily form through liquid-liquid phase separation, a process in which proteins and nucleic acids segregate from the surrounding milieu to assemble into micron-scale structures. By concentrating functionally related proteins and nucleic acids, these biomolecular condensates regulate a myriad of essential cellular processes.

View Article and Find Full Text PDF

Large vertebrate genomes duplicate by activating tens of thousands of DNA replication origins, irregularly spaced along the genome. The spatial and temporal regulation of the replication process is not yet fully understood. To investigate the DNA replication dynamics, we developed a methodology called RepliCorr, which uses the spatial correlation between replication patterns observed on stretched single-molecule DNA obtained by either DNA combing or high-throughput optical mapping.

View Article and Find Full Text PDF

Therapeutic drugs and multivalent vaccines based on the delivery of mRNA via lipid nanoparticle (LNP) technologies are expected to dominate the biopharmaceutical industry landscape in the coming years. Many of these innovative therapies include several nucleic acid components (e.g.

View Article and Find Full Text PDF

Understanding the interaction between nanomaterials and cellular structures is crucial for nanoparticle applications in biomedicine. We have identified a subtype of stress granules, called nanomaterial-provoked stress granules (NSGs), induced by gold nanorods (AuNRs). These NSGs differ from traditional SGs in their physical properties and biological functions.

View Article and Find Full Text PDF

Fiber Sorbents - A Versatile Platform for Sorption-Based Gas Separations.

Acc Mater Res

January 2025

School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30322, United States.

Increasing demand for high-purity fine chemicals and a drive for process intensification of large-scale separations have driven significant work on the development of highly engineered porous materials with promise for sorption-based separations. While sorptive separations in porous materials offer energy-efficient alternatives to longstanding thermal-based methods, the particulate nature of many of these sorbents has sometimes limited their large-scale deployment in high-throughput applications such as gas separations, for which the necessary high feed flow rates and gas velocities accrue prohibitive operational costs. These processability limitations have been historically addressed through powder shaping methods aimed at the fabrication of structured sorbent contactors based on pellets, beads or monoliths, commonly obtained as extrudates.

View Article and Find Full Text PDF

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!