Article
Polymer Science
Sojeong Kim, Won Bo Lee, Nicolas R. de Souza, Soo-Hyung Choi
Summary: The segmental dynamics of complex coacervates were studied using quasi-elastic neutron scattering. It was found that the number of mobile chain segments and their dynamics increase with salt concentration in ammonium-based coacervates, whereas guanidinium-based coacervates show slow and comparable segmental relaxation regardless of salt concentration, possibly due to non-electrostatic interactions. The combination of chemical structure, salt concentration, and temperature plays a significant role in determining polymer chain dynamics influenced by the strength of ionic bonding.
Article
Multidisciplinary Sciences
Shensheng Chen, Zhen-Gang Wang
Summary: There is a discrepancy between experiments and model studies regarding the thermodynamic driving force in polyelectrolyte complex coacervation. This study combines molecular dynamics simulation with thermodynamic analysis to explore the potential of mean force in key stages of the coacervation pathway. The results show that the temperature dependence in the dielectric constant of water gives rise to a substantial entropic contribution in the electrostatic interaction, providing an explanation for the thermodynamic behavior observed in experiments.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Chemistry, Physical
Chelsea E. R. Edwards, Kareem L. Lakkis, Yimin Luo, Matthew E. Helgeson
Summary: The non-equilibrium processing of aqueous polyelectrolyte complex coacervates is crucial for many applications. This study reveals the influence of flow conditions on the coarsening mechanism of the complex and demonstrates that flow conditions can control the formation of rough, precipitate-like aggregates. The results also show that these aggregates undergo micron-scale coarsening with a mixing time-dependent aging time scale.
Article
Polymer Science
Marcos Vinicius Aquino Queiros, Watson Loh
Summary: The study reports the phase behavior of polyelectrolyte complex coacervates in the presence of inorganic salts, specifically poly(acrylate) and poly(diallyldimethylammonium). It was found that poly-ion segregation in these mixtures depends on the type of anion present. The results demonstrate a strong segregation phenomenon for both poly(acrylate) and poly(diallyldimethylammonium) accompanied by their small counterions.
Article
Multidisciplinary Sciences
Wei Guo, Andrew B. Kinghorn, Yage Zhang, Qingchuan Li, Aditi Dey Poonam, Julian A. Tanner, Ho Cheung Shum
Summary: The synthetic pathways of life's building blocks are envisioned to go through a series of complex prebiotic reactions and processes. However, compartmentalizing and concentrating biopolymers under prebiotic conditions remains a challenge. Liquid-liquid phase separation has been proposed as a potential mechanism for prebiotic compartmentalization, but the interaction between RNA and polycations could inhibit RNA folding and functioning inside coacervates. A prebiotically plausible pathway for non-associative phase separation within an evaporating all-aqueous sessile droplet is presented, demonstrating the formation of prebiotic membraneless compartments with the ability to localize and store nucleic acids, enhance ribozyme activity, and facilitate chemical processes required for the RNA world hypothesis.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Carsten Donau, Fabian Spaeth, Michele Stasi, Alexander M. Bergmann, Job Boekhoven
Summary: This study describes a model based on a complex coacervate gel, which regulates the affinity and liquidity of droplets in membraneless organelles by controlling the chemical reaction cycle. The findings reveal the regulatory mechanism of subcompartments in membraneless organelles, providing new insights into the importance of active processes inside cells.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Polymer Science
Christian C. M. Sproncken, Berta Gumi-Audenis, Sanam Foroutanparsa, Jose Rodrigo Magana, Ilja K. Voets
Summary: By modulating the pH, weak polyelectrolytes can be complexed to achieve temporal control over their coassembly. In this study, oppositely charged poly(allylamine hydrochloride) and poly(sodium methacrylate) were mixed in a (bi)sulfite buffer, resulting in the formation of nanoscopic complex coacervates. The addition of formaldehyde triggered the formaldehyde-sulfite clock reaction, which affected the polyelectrolyte assembly by changing their charge density and inducing chemical modifications on the polymer. Interestingly, core-shell polymeric nanoparticles were produced, which remained colloidally stable for months.
Article
Chemistry, Physical
Anna Bratek-Skicki, Margot Van Nerom, Dominique Maes, Peter Tompa
Summary: Biomolecular condensates are membraneless organelles formed through liquid-liquid phase separation that can concentrate a variety of molecules in cells. They are highly dynamic and play crucial roles in cellular organization and physiology, with links to diseases like neurodegenerative disorders and cancer. This review discusses the mechanisms, dynamics, and evolution of these biological colloids, particularly focusing on their surface properties and interactions with other cellular components. Experimental approaches for characterizing the formation, interactions, and functions of these cellular colloidal organelles are also summarized.
ADVANCES IN COLLOID AND INTERFACE SCIENCE
(2022)
Article
Food Science & Technology
Chen Cheng, Zongcai Tu, Hui Wang
Summary: The aim of this study was to investigate the phase behavior and structural properties of fish gelatin complex coacervation with carboxylated chitosan. Zeta potential indicated that electrostatic interaction drove the complex coalescence of fish gelatin and carboxylated chitosan. The study found that the addition of carboxylated chitosan changed the tertiary conformation of fish gelatin and resulted in a shift in its structure.
FOOD RESEARCH INTERNATIONAL
(2023)
Article
Chemistry, Multidisciplinary
Dongwook Kim, Hideki Matsuoka, Yoshiyuki Saruwatari
Summary: The study investigated the behavior of micelle formation in the sulfobetaine-containing entirely ionic block copolymer/ionic homopolymer system and its temperature responsivity. The block-/cationic homopolymer system exhibited temperature responsivity of upper critical solution temperature type, while the block-/anionic homopolymer system showed a core-shell structure at low concentration but lacked temperature responsiveness.
Article
Biochemistry & Molecular Biology
Abraham Garcia-Jimenez, Angelica Roman-Guerrero, Cesar Perez-Alonso, Benoit Fouconnier
Summary: This study investigates the effect of pH and ionic strength on the association interactions and phase separations in polyelectrolyte systems. The results show that the structure and phase transitions can be controlled by modifying the ionization degree, pKa, and charge screening. The findings provide insights into the functional properties of complexed polysaccharides.
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2022)
Article
Nanoscience & Nanotechnology
Lei Liu, Guocheng Wang, Yuanyou Xiao, Zhuo Zhao, Zhanbing Yang
Summary: In this study, the formation of Cr-N clusters as precursor of Cr2N phase along grain boundaries under aging at 1023 K was simulated using LAMMPS molecular dynamics approach. The variation of calculated diffusion coefficients with time suggests the formation of Cr-N clusters is controlled by the diffusion of Cr, N and Cr-N clusters. Furthermore, the calculated radius of pair gyration of Cr-N clusters indicates a transition from chaotic to more orderly structure at grain boundaries. The mechanism of Cr-N clusters revealed in this study can provide guidance for the optimization design of controlling Cr2N precipitation.
SCRIPTA MATERIALIA
(2023)
Article
Chemistry, Physical
Jingjing Qing, Simon Lekakh, Mingzhi Xu, Daniel Field
Summary: The study investigated the complex nature of nodular graphite nuclei in spheroidal graphite iron with small graphite nodules, revealing the nucleation sites, chemistry, and crystallographic orientations inside the graphite nodules. The research also discovered the presence of oxide, sulfide, and nitride compounds within the graphite nodules, providing insights into the formation and behavior of complex nodular graphite nuclei.
Article
Biochemistry & Molecular Biology
Fotini Plati, Christos Ritzoulis, Eleni Pavlidou, Adamantini Paraskevopoulou
Summary: This study investigated the intermolecular interactions and structure formation between hemp protein isolate (HPI) and gum Arabic (GA), revealing their complexation mechanisms under different pH and protein to polysaccharide ratios. The results showed that critical phase transition pH shifted to higher values with the increase in ratio (R), until reaching a plateau at ratio 10:1, where complexes were formed even in regions where both biopolymers were negatively charged. Maximum coacervation occurred at ratio R = 2:1 and pHopt = 3.5, with a yield of 92%, confirming the molecular interactions between HPI and GA primarily through electrostatic interactions with secondary stabilization of hydrogen bonds. These findings could be valuable for the development of HPI-GA coacervates as a potential bioactive encapsulation means.
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2021)
Article
Chemistry, Multidisciplinary
Aoon Rizvi, Justin T. Mulvey, Joseph P. Patterson
Summary: The study investigates the formation of block-copolymer-supported bilayers using LP-TEM, revealing two formation pathways involving liquid droplets or vesicles as intermediates. The results suggest that bilayer assembly methods via liquid droplet intermediates are beneficial for forming pristine supported bilayers, and supported bilayers inside liquid cells may be useful for imaging membrane interactions with proteins and nanoparticles in the future.
Article
Chemistry, Physical
Dorian Bruch, Christopher Balzer, Zhen-Gang Wang
Summary: Electric double layers are widely used in science and engineering, but calculating thermodynamic properties from the free energy of a system with charged surfaces can be complicated. In this study, a systematic framework is presented to properly account for the different specifications on charged bodies in electrolyte solutions. The approach is demonstrated using the Poisson-Boltzmann theory and emphasizes the importance of using the proper thermodynamic potential, providing a general framework for calculating thermodynamic properties of electrolyte solutions near charged surfaces.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Baicheng Mei, Bilin Zhuang, Yuyuan Lu, Lijia An, Zhen-Gang Wang
Summary: By introducing the concept of local-average free volume, this study reveals the correlation between dynamic heterogeneity and the average local free volume in glass formers, resolving the controversy regarding the role of free volume in particle rearrangements.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Polymer Science
Shensheng Chen, Pengfei Zhang, Zhen-Gang Wang
Summary: In this study, dissipative particle dynamics was used to investigate the behavior of polyelectrolyte complexes in dilute solutions. The results show that net-charged macromolecular clusters are formed in the systems, which depends on the overall charge asymmetry. When the charge ratio reaches a threshold value, the polyions condense into a single large coacervate cluster. The addition of salt leads to salting-out and salting-in phenomena, and the length and concentration asymmetry play significant roles in polyelectrolyte complex coacervation.
Article
Polymer Science
Zhenhua Wang, Ruishu Wang, Yuyuan Lu, Lijia An, An-Chang Shi, Zhen-Gang Wang
Summary: The study found that different capture mechanisms exist for linear and ring polymers under flow induction, and the critical flux is affected by the increase in channel size. Additionally, the conformation of the polymer undergoes a flow-induced transition, and monomers inside and outside the channel exhibit independent dynamics.
Article
Polymer Science
Pengfei Zhang, Zheng Wang, Zhen-Gang Wang
Summary: Based on a minimal lattice model, this study applies the Wang-Landau Monte Carlo algorithm and a Flory-type mean-field theory to investigate the conformation of a homopolymer chain in a mixture of binary solvents A and B. The results show that adding a small amount of better solvent B in a good solvent A causes a continuous collapse transition when the difference in the solvent quality is large. Increasing the fraction of solvent B results in a smooth reswelling of the chain. These findings are explained by the delicate interplay among the mixing entropy of binary solvents, the chain conformational entropy, and the competition in the interactions between the monomer and the two solvents.
Article
Chemistry, Physical
Samuel Varner, Christopher Balzer, Zhen-Gang Wang
Summary: Implicit solvent models are commonly used to study soft materials and biophysical systems by simplifying solvent degrees of freedom into effective interaction potentials. In electrolyte and polyelectrolyte solutions, the solvent degrees of freedom are coarse-grained into an effective dielectric constant, which incorporates the entropic contributions into the temperature dependence of the dielectric constant. Properly considering the electrostatic entropy is crucial for differentiating between enthalpically and entropically driven free energy changes. In this study, we investigate the entropic origin of electrostatic interactions in a dipolar solvent and provide a clearer physical understanding of the solvent dielectric response. We calculate the potential of mean force (PMF) between oppositely charged ions in a dipolar solvent using molecular dynamics and dipolar self-consistent field theory, and find that the PMF is primarily governed by the entropy gain from dipole release, resulting from reduced orientational polarization of the solvent. We also observe a nonmonotonic temperature dependence of the relative contribution of entropy to the free energy change. Our findings are expected to be applicable to a wide range of problems involving ionic interactions in polar solvents.
JOURNAL OF PHYSICAL CHEMISTRY B
(2023)
Article
Polymer Science
Zhenhua Wang, Zhen-Gang Wang, An-Chang Shi, Yuyuan Lu, Lijia An
Summary: The effects of confinement and hydrodynamic interactions on single-chain diffusion behaviors are studied using molecular dynamics and multiparticle collision dynamics simulations. It is found that long chains exhibit diffusion behavior consistent with Zimm dynamics, while short chains deviate from it. For confined chains, the diffusion behavior undergoes a crossover from Zimm to Rouse dynamics as the channel size decreases. The transition can be quantitatively described by extending the partially permeable sphere model to the blob scale.
Article
Chemistry, Physical
Christopher Balzer, Zhen-Gang Wang
Summary: End-tethered polyelectrolytes are commonly used to modify substrate properties, and external stimuli can further tune these modifications. This study investigates the structure and electroresponsiveness of weak polyacid brushes using an inhomogeneous theory, and explores the relationship between swelling behavior and differential capacitance.
EUROPEAN PHYSICAL JOURNAL E
(2023)
Article
Chemistry, Physical
Shensheng Chen, Zhen-Gang Wang
Summary: Biomolecular assembly often exhibits enthalpy-entropy compensation behavior, but its molecular origin and the contribution of water restructuring to entropy and enthalpy changes in this process have been poorly understood. This study shows that water reorganization entropy/enthalpy can be obtained by exploiting the temperature dependence in effective, implicit-solvent potentials. The temperature dependencies in hydrophobic interactions, resulting from water reorganization, significantly contribute to the variations in entropy/enthalpy change and are responsible for the observed enantioselective enrichment.
JOURNAL OF PHYSICAL CHEMISTRY B
(2023)
Article
Polymer Science
Ruochao Wang, Valeriy V. Ginzburg, Jian Jiang, Zhen-Gang Wang
Summary: The characteristics of surfaces have significant effects on polyelectrolyte adsorption. Random charge distribution results in the strongest adsorption, while uniform distribution shows the weakest. In the presence of dielectric contrast, image repulsion inhibits adsorption onto uniformly charged surfaces, while surfaces with discrete charge distributions exhibit enhanced adsorption.
Article
Polymer Science
Kevin. D. D. Dorfman, Zhen-Gang Wang
Summary: The Largecell self-consistent field theory (SCFT) solutions, initialized using the structure of a Lennard-Jones fluid, show the existence of numerous liquid-like states with higher free energies compared to the body-centered cubic (bcc) state near the order-disorder transition (ODT). The structure factor calculation indicates a slightly swollen intermicellar distance for these liquid-like states at temperatures below ODT. The presence of multiple liquid-like states and their near-degeneracy with the equilibrium bcc morphology explains the slow ordering kinetics observed in particle-forming diblock copolymer melts.
Article
Chemistry, Physical
Abbas Shirdast, Behnam Davoodi, Jamal Aalaie, Pengfei Zhang, Alireza Sharif
Summary: Grafting hydrophobic alkyl moieties onto the chain backbone can reduce the hydrophilicity of the semi-flexible polysaccharide Sclg, improving its utilization as a polymeric surfactant. In this study, the influences of grafted alkyl moieties with different lengths (C6, C10, or C18) on the adsorption behaviors of the modified Sclgs on a carbonate surface were investigated using self-consistent field theory. The results provide insights into the adsorption mechanisms and contribute to the development of advanced bio-polymeric surfactants.
Article
Chemistry, Physical
Benjamin Bobin Ye, Zhen-Gang Wang
Summary: Recent mean-field theories predict spontaneous surface charge separation in room-temperature ionic liquid electric double-layer capacitors without applied potential. In this study, a coarse-grained molecular model is constructed to directly simulate the behavior of the ionic liquid, revealing the importance of image charge interactions and enhanced in-plane ordering on electrodes, which are not considered by mean-field theories.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)