查看更多>>摘要：Polyelectrolytes are charged polymers comprising macromolecules in which substantial portions of the constituent units contain cationic(e.g.,pyridinium,ammonium)or anionic(e.g.,sulfonate,carboxylate)groups,which possess special functions from the features of coun-terions,such as dissociation to charged species,mechanical stability,phase behavior,etc.Therefore,functional polyelectrolytes have been widely applied in many fields.In this perspective,we present some progresses in the studies of poly(polyoxometalate)s,denoted as poly(POM)s,as a kind of new charged polymers/polyelectrolytes,by covalent bonding between the inorganic polyoxometalate(POM)clusters and the organic polymer chains.According to the distinct positions of POMs in polymer chain and functions of poly(POM)s,they are divided into the following four categories:crosslinked poly(POM);side-chain poly(POM);backbone poly(POM),including poly(POM)-conjugated polymer hybrid and block poly(POM)-polymer;and POM-based covalent organic framework(PCOF).This perspective introduces the synthesis methods of poly(POM)poly-electrolytes and their macromolecular and aggregate structural characteristics,while also focusing on their properties and functions.Their appli-cation areas include catalysis,thermal resistance,optical functions,fuel cells and batteries,etc.
查看更多>>摘要：The counterion-mediated hydrogen bonding(CMHB)is related to the hydrogen bonding between bound counterions and polyelec-trolyte chains in polyelectrolyte systems,where the counterions can both electrostatically bind to the charged groups of polyelectrolyte chains and act as hydrogen bond donors or acceptors to form hydrogen bonds with the hydrogen bond sites associated with polyelectrolyte chains si-multaneously.A large number of literatures illustrate that strong polyelectrolytes(SPs)are insensitive to pH,which severely limmits the applica-tions of SPs as smart materials.However,our studies have demonstrated that the CMHB makes SPs pH-responsive.This perspective discusses the mechanism of pH responsiveness of SPs and the pH-tunable properties of SPs,based on the pH-controlled CMHB effect.The future research di-rections on the pH responsiveness of SPs are also discussed here.It is anticipated that the study of the pH responsiveness of SPs not only will pro-vide a new understanding of the fundamental properties of SPs,but also will greatly expand the applications of SPs in the field of smart materials.
查看更多>>摘要：Polyelectrolyte solutions are more variable than uncharged macromolecule due to electrical interaction between charged molecules and surrounding counterions.Therefore,the subject of polyelectrolyte solutions has attracted a wide range of interests in both basic and applied research,and has also been extensively explored.However,the understanding of the molecular dynamics and conformation of polyelectrolytes in solution remains to be deepened,and universal consensus on some key issues have not been reached.Many methods have contributed to solving the above problems in different ways,including dielectric relaxation spectroscopy(DRS).In this perspective,we briefly reviewed the his-tory of dielectric spectroscopic research on polyelectrolyte solution,with emphasis on summarizing our efforts.In particular,we expound the characteristics of DRS and its ability to obtain the internal information of the system of interest.Finally,we evaluate the advantages and limita-tions of the dielectric method and discussed future prospects of this field.
查看更多>>摘要：Polymer density-functional theories(PDFTs)have distinct advantages in the study of polyelectrolyte(PE)systems over experiments and molecular simulations.Here we give an introductory review of some PDFTs recently developed for PE systems.We start with a general formal-ism of PDFTs and its relation to the widely used polymer self-consistent field theory(SCFT),then explain the various correlations that are neglect-ed in SCFT but can be accounted for in PDFTs,including those due to the excluded-volume interaction and chain connectivity of uncharged poly-mers,the electrostatic correlations of small ions,and the chain correlations in PEs.We also list some applications of PDFTs for PE systems,and fi-nally give some perspectives on future work.We hope that our review can attract more researchers to apply and further develop PDFTs as a promising class of theoretical and computational tools.
查看更多>>摘要：Polyelectrolyte brushes(PEBs)are commonly used to modify surface that have attracted great research interest.The dielectric permit-tivity of the grafted surface is typically significantly different from that of solution,which results in surface polarization(SP)effect with a jump of electric field.It is thus important to study how SP alters the PEB's structure and properties.In this work,the SP effects on PEB structure was stud-ied using a statistical thermodynamic theory.The free energy functional to describe SP effect was constructed by using the image-charge method.Meanwhile,the electrostatic potential was solved from a modified Poisson-Boltzmann equation taking the ion solvation effect into con-sideration.In the absence of SP,the thickness of PEB exhibited a continuous collapse transition when decreasing the solvent quality.In the pres-ence of SP,the collapse became a jump-like transition.Free energy analysis showed that the long-range Coulombic interaction dominated the transition because of the enhanced counterion condensation in the presence of SP.The theory provides an effective tool to study SP effect on PEBs,and the results explain the underlying physics in PEB collapse transition.
查看更多>>摘要：We investigate the solution self-assembly of a mixture of positively charged homopolymers and AB diblock copolymers,in which the A blocks are negatively charged,and the B blocks are neutral.The electrostatic complexation between oppositely charged polymers drives the for-mation of many ordered phases.The microstructures and phase diagrams are calculated using self-consistent field theory(SCFT)based on an ion-pair model with an equilibrium constant K to characterize the strength of binding between positively and negatively charged monomers.The ef-fects of the charge ratio,representing the ratio of charges from the homopolymer over all charges from polymers in the system,on the ordered structure are systematically studied,both for hydrophobic and hydrophilic A blocks.The charge ratio plays an important role in determining the phase boundaries in the phase diagram of salt concentration versus polymer concentration.We also provide information about the varying ten-dency of the domain spacing and core size of the spherical phase when the charge ratio is changed,and the results are in good agreement with experiments.These studies provide a deep understanding of the self-assembled microstructures of oppositely charged diblock copolymer-homopolymer systems.
查看更多>>摘要：The liquid-liquid phase separation of biopolymers in living cells contains multiple interactions and occurs in a dynamic environment.Resolving the regulation mechanism is still a challenge.In this work,we designed a series of peptides(XXLY)6SSSGSS and studied their complexa-tion and coacervation behavior with single-stranded oligonucleotides.The"X"and"Y"are varied to combine known amounts of charged and non-charged amino acids,together with the introduction of secondary structures and pH responsiveness.Results show that the electrostatic in-teraction,which is described as charge density,controls both the strength of complexation and the degree of chain relaxation,and thus deter-mines the growth and size of the coacervates.The hydrophobic interaction is prominent when the charges are neutralized.Interestingly,the sec-ondary structures of peptides exhibit profound effect on the morphology of the phases,such as solid phase to liquid phase transition.Our study gains insight into the phase separation under physiological conditions.It is also helpful to create coacervates with desirable structures and func-tions.
查看更多>>摘要：We utilize molecular dynamics simulations to investigate the microstructures of ions and polyelectrolytes in aqueous solutions under external electric fields.By focusing on the multi-body interactions between ionic components and H2O molecules,as well as their responses to the external electric fields,we clarify several nontrivial molecular features of the ionic and polyelectrolyte solutions,such as the solvations of cations and anions,clustering of the ions,and dispersions/aggregations of polyelectrolyte chains,as well as the corresponding responses of H2O molecules in these contexts.Our simulations illustrate the variations in structures of ionic solutions caused by reversing the charge sign of the ions,and elucidate the disparity in structures between anionic and cationic polyelectrolyte solutions in the presence of the external electric fields.This work clarifies the mechanism for the alternations in complex multi-body interactions in aqueous solutions caused by the application electric field,which can contribute to the fundamental understanding of the physical and chemical natures of ion-containing and charged polymeric sys-tems.
查看更多>>摘要：Understanding how supercoiled DNA releases intramolecular stress is essential for its functional realization.However,the molecular mechanism underlying the relaxation process remains insufficiently explored.Here we employed MD simulations based on the oxDNA2 model to investigate the relaxation process of a 336-base pair supercoiled minicircular DNA under double-strand breaks with two fixed endpoints.Our sim-ulations show that the conformational changes in the DNA occur continuously,with intramolecular stress release happening abruptly only when the DNA chain traverses the breakage site.The relaxation process is influenced not only by the separation distance between the fixed ends but al-so their angle.Importantly,we observe an inhibitory effect on the relaxation characterized by small angles,where short terminal loops impede DNA conformational adjustments,preserving the supercoiled structure.These findings elucidate the intricate interplay between DNA conforma-tional change,DNA motion and intramolecular stress release,shedding light on the mechanisms governing the relaxation of supercoiled DNA at the molecular level.
万方数据
维普