Study On The Preparation And Properties Of Polymer Nanocomposites Of Molecular Cluster From Electrostatic Interaction

Polymer nanocomposites have the functions of nanoparticles and the advantages of polymers in mechanical properties,providing more possibilities for the preparation of multifunctional materials.However,the multi-dispersion of its structure seriously hinders the study of common scientific problems such as its structure-activity relationship.Polyoxometalates（POMs for short）are a kind of single-molecule clusters with a clear structure and nanoscale,it have a rich topological structure and diverse functionalities.On the other hand,molecular dynamics can be used to explain the connections that exist between the microstructure and macroscopic properties of polymers.Although scholars have done a lot of research on the structure and morphological distribution of polymer nanocomposites,the understanding of the relationship between microstructure and molecular dynamics is still lacking.In this context,based on the principle of electrostatic action,this paper designs two polymer nanocomposites,which proves that the prepared materials have the characteristics of uniform distribution through a series of chemical structure and microstructural characterization.Combining Differential Scanning Calorimetry and Broadband Dielectric Spectroscopy to study the dynamic behavior of each system.The main research contents and achievements of this paper are as follows:（1）Based on the principle of electrostatic bonding and reversible addition-fracture chain transfer（RAFT）polymerization,this paper design two different synthetic routes（“Grafting-from”and“Grafting-to”）that combine Keplerate-type polyoxometalates{Mo₁₃₂}(（NH₄）₄₂[Mo₁₃₂O₃₇₂（CH₃COO）₃₀（H₂O）₇₂]·（H₂O）₃₀₀·（CH₃COONH₄）₁₀)and the end with the positively charged polystyrene is compounded to form an inorganic-organic hybrid nanocomposite material.The characteristics of the two synthetic routes are analyzed through a series of structural characterizations,and the effect of the restricted effects of nanoparticles on the polymerization environment was studied.The study found that for the“Grafting-to”grafting route,that is,the preparation route of positively charged polystyrene polymerized by RAFT first and then electrostatically bound with{Mo₁₃₂},the prepared composite materials have the characteristics of uniform dispersion.However,for the“Grafting-from”grafting route,that is,the chain transfer agent modification on the surface of the{Mo₁₃₂}nanoparticles and then through the RAFT polymerization at this macromolecular chain transfer agent as the reaction site,the dispersion of the prepared polymer nanocomposites is poor.Finally,the characteristics of the two grafting methods of“Grafting-to”and“Grafting-from”are experimentally verified.The results show that the restricted effect of nanoparticles has an impact on the polymerization chemical environment,which in turn affects the structure of the composite material.（2）For single-charge polymer/polyoxometalates nanocomposite systems,the effect of restriction on microscopic dynamic behavior and the relationship between restriction dynamic and polymer molecular weight are studied.It is found that nanoparticles have a restrictive effect on the relaxation of polymer segments,which is reflected in the relaxation of the glass transition platform in the DSC in the direction of high temperature,and the platform has a clear trend of widening.As the molecular weight increases,the vitrification transition behavior gradually tends to be pure polymer.Dielectric testing also reflects restricted behavior:the polymer segments close to the surface of the nanoparticles are restricted by adding nanoparticles,so that the ability of the polymer segments to move is reduced,the segment relaxation peaks moves to the low frequency direction relative to the pure polymer.It was also found that the larger the molecular weight,the smaller the offset of the dielectric loss,and gradually tended to the dielectric loss characteristics of pure polymers.In addition,the application of AFM test methods in the modulus of nanocomposite materials is also studied.It is found that the modulus of pure polymers and composites increases with the increase of molecular weight,and the modulus of composites of the same molecular weight increases relative to pure polymers.（3）For multi-charge polymer/polyoxometalates nanocomposite systems,three random copolymers with different proportions of charged monomers（P（VBTAC-co-S））are prepared by simple modification of the polymeric monomers.By combining the multi-charge polymer with Preyssler-type polyoxometalate{NaP₅W₃₀}(K_12.5Na_1.5[NaP₅W₃₀O₁₁₀]·15H₂O)by electrostatic action principle,three composites with different nanoparticle content(P（VBTAC-co-S）-{NaP₅W₃₀})are prepared.Through a series of chemical structures and microstructures,the integrity of composite structures and the uniform distribution of nanoparticles in the system are characterized.Combining differential scanning calorimetry and broadband dielectric method to study the effect of restriction on the dynamic behavior of the system,it is found that the dynamics of the three composite chain segments have different temperature dependence.That is,with the increase of nanoparticle content,the segment relaxation behavior of composite materials changed from the VFT trend to the Arrhenius trend.This paper focuses on the principle of electrostatic bonding,designs two polymer nanocomposites with different structures（unit point system and multi-point system）,the structural characteristics of each composite are characterized by a series of chemical structures and microstructures.The effect of molecular weight of grafted polymers on confined relaxation dynamics in the unit point system is systematically studied.In addition,the effect of copolymer cationicity on confined relaxation dynamics in multi-point systems is also studied.This paper provides reference significance for explaining the dynamic behavior of polymer nanocomposites of molecular cluster from electrostatic interaction.