Synthesis of Branched Polyethylene via Bulky α-Diimine Nickel(II)-Catalyzed Ethylene Chain-Walking Polymerization

The catalysis of olefin polymerization through the chain-walking process is a subject of great interest. In this contribution, the successful synthesis of a Brookhart-type unsymmetrical α-diimine nickel catalyst Ni, which contains both dibenzhydryl and phenyl groups, was determined by X-ray crystallography. The compound has a pseudo-tetrahedral geometry at the Ni center, showing pseudo-C2-symmetry. Upon activation with modified methylaluminoxane (MMAO), Ni1 exhibits high catalytic activity up to 1.02 × 107 g PE (mol Ni h)−1 toward ethylene polymerization, enabling the synthesis of high molecular weight branched polyethylene. The molecular weights and branching densities could be tuned over a very wide range. The polymerization results indicated the possibility of precise microstructure control, depending on the polymerization temperature. The branching densities were decreased with increasing the polymerization temperature.

3D printing encouraging desired in-situ polypyrrole seed-polymerization for ultra-high energy density supercapacitors

The tireless pursuit of supercapacitors with high energy density entails the parallel advancement of wellsuited electrode materials and elaborately engineered architectures.Polypyrrole(PPy)emerges as an exceedingly conductive polymer and a prospective pseudocapacitive materials for supercapacitors,yet the inferior cyclic stability and unpredictable polymerization patterns severely impede its real-world applicability.Here,for the first time,an innovative seed-induced in-situ polymerization assisted 3D printing strategy is proposed to fabricate PPy-reduced graphene oxide/poly(vinylidene difluoride-cohexafluoropropylene)(PVDF-HFP)(PPy-rGO/PH)electrodes with controllable polymerization behavior and exceptional areal mass loading.The preferred active sites uniformly pre-planted on the 3D-printed graphene substrates serve as reliable seeds to induce efficient polypyrrole deposition,achieving an impressive mass loading of 185.6 mg cm^(-2)(particularly 79.2 mg cm^(-2)for polypyrrole)and a superior areal capacitance of 25.2 F cm^(-2)at 2 mA cm^(-2)for a 12-layer electrode.In agreement with theses appealing features,an unprecedented areal energy density of 1.47 mW h cm^(-2)for a symmetrical device is registered,a rarely achieved value for other PPy/rGO-based supercapacitors.This work highlights a promising route to preparing high energy density energy storage modules for real-world applications.

Effect of solvent on the initiation mechanism of living anionic polymerization of styrene:A computational study

For living anionic polymerization(LAP),solvent has a great influence on both reaction mechanism and kinetics.In this work,by using the classical butyl lithium-styrene polymerization as a model system,the effect of solvent on the mechanism and kinetics of LAP was revealed through a strategy combining density functional theory(DFT)calculations and kinetic modeling.In terms of mechanism,it is found that the stronger the solvent polarity,the more electrons transfer from initiator to solvent through detailed energy decomposition analysis of electrostatic interactions between initiator and solvent molecules.Furthermore,we also found that the stronger the solvent polarity,the higher the monomer initiation energy barrier and the smaller the initiation rate coefficient.Counterintuitively,initiation is more favorable at lower temperatures based on the calculated results ofΔG_(TS).Finally,the kinetic characteristics in different solvents were further examined by kinetic modeling.It is found that in benzene and n-pentane,the polymerization rate exhibits first-order kinetics.While,slow initiation and fast propagation were observed in tetrahydrofuran(THF)due to the slow free ion formation rate,leading to a deviation from first-order kinetics.

Two-photon polymerization lithography for imaging optics

Optical imaging systems have greatly extended human visual capabilities,enabling the observation and understanding of diverse phenomena.Imaging technologies span a broad spectrum of wavelengths from x-ray to radio frequencies and impact research activities and our daily lives.Traditional glass lenses are fabricated through a series of complex processes,while polymers offer versatility and ease of production.However,modern applications often require complex lens assemblies,driving the need for miniaturization and advanced designs with micro-and nanoscale features to surpass the capabilities of traditional fabrication methods.Three-dimensional(3D)printing,or additive manufacturing,presents a solution to these challenges with benefits of rapid prototyping,customized geometries,and efficient production,particularly suited for miniaturized optical imaging devices.Various 3D printing methods have demonstrated advantages over traditional counterparts,yet challenges remain in achieving nanoscale resolutions.Two-photon polymerization lithography(TPL),a nanoscale 3D printing technique,enables the fabrication of intricate structures beyond the optical diffraction limit via the nonlinear process of two-photon absorption within liquid resin.It offers unprecedented abilities,e.g.alignment-free fabrication,micro-and nanoscale capabilities,and rapid prototyping of almost arbitrary complex 3D nanostructures.In this review,we emphasize the importance of the criteria for optical performance evaluation of imaging devices,discuss material properties relevant to TPL,fabrication techniques,and highlight the application of TPL in optical imaging.As the first panoramic review on this topic,it will equip researchers with foundational knowledge and recent advancements of TPL for imaging optics,promoting a deeper understanding of the field.By leveraging on its high-resolution capability,extensive material range,and true 3D processing,alongside advances in materials,fabrication,and design,we envisage disruptive solutions to current challenges and a promising incorporation of TPL in future optical imaging applications.

Nickel catalysts with asymmetric steric hindrance for ethylene polymerization

α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics.A series ofα-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization.In this work,we synthesized a series of asymmetricα-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization.These nickel catalysts have high ethylene polymerization activity,up to 6.51×10^(6)g·mol^(−1)·h^(−1),and the prepared polyethylene has a moderate melting point and high molecular weight(up to 38.2×10^(4)g·mol^(−1)),with a branching density distribution between 7 and 94 branches per 1000 carbons.More importantly,the polyethylene prepared by these catalysts exhibits excellent tensile properties,with strain and stress reaching 800%and 30 MPa,respectively.

Lithium Salt Combining Fluoroethylene Carbonate Initiates Methyl Methacrylate Polymerization Enabling Dendrite-Free Solid-State Lithium Metal Battery

This work demonstrates a novel polymerization-derived polymer electrolyte consisting of methyl methacrylate,lithium bis(trifluoromethanesulfonyl)imide and fluoroethylene carbonate.The polymerization of MMA was initiated by the amino compounds following an anionic catalytic mechanism.LiTFSI plays both roles including the initiator and Li ion source in the polymer electrolyte.Normally,lithium bis(trifluoromethanesulfonyl)imide has difficulty in initiating the polymerization reaction of methyl methacrylate monomer,a very high concentration of lithium bis(trifluoromethanesulfonyl)imide is needed for initiating the polymerization.However,the fluoroethylene carbonate additive can work as a supporter to facilitate the degree of dissociation of lithium bis(trifluoromethanesulfonyl)imide and increase its initiator capacity due to the high dielectric constant.The as-prepared poly-methyl methacrylate-based polymer electrolyte has a high ionic conductivity(1.19×10^(−3)S cm^(−1)),a wide electrochemical stability window(5 V vs Li^(+)/Li),and a high Li ion transference number(t_(Li^(+)))of 0.74 at room temperature(RT).Moreover,this polymerization-derived polymer electrolyte can effectively work as an artificial protective layer on Li metal anode,which enabled the Li symmetric cell to achieve a long-term cycling performance at 0.2 mAh cm^(−2)for 2800 h.The LiFePO_(4)battery with polymerization-derived polymer electrolyte-modified Li metal anode shows a capacity retention of 91.17%after 800 cycles at 0.5 C.This work provides a facile and accessible approach to manufacturing poly-methyl methacrylate-based polymerization-derived polymer electrolyte and shows great potential as an interphase in Li metal batteries.

Efficient in-situ end-functionalization of polydienes by isothiocyanate via neodymium mediated coordinative chain transfer polymerization system

End-functionalization of polydiene rubbers can not only improve its compatibility with inorganic fillers,but also enhance the overall mechanical properties.Nevertheless,for traditional neodymium(Nd)diene polymerization systems,it is highly challenging to achieve such end-functionalizations,because most of polydienyl chains are capped withη3-allyl-Nd moiety during the end of polymerization,which shows very poor reactivity with nucleophile compounds.We launched a new diene polymerization strategy calling coordinative chain transfer polymerization(CCTP)[1].In such a system,all the polydienyl chains are capped withη1-allyl-Al moieties,which reveal greater reactivity with cyclic esters and epoxide compounds,providing an effective manner to prepare polydiene-polyester amphiphilic block copolymers.Inspired by such findings,we now show herein how such types of chain-ends react with isot-hiocyanate to demonstrate an efficient in-situ manner to access end-functionalized polydienes by using CCTP.

Influence of external nitrogen-containing donors on polymerization behavior of neodymium-based cis-1,4-polybutadiene rubber

Neodymium(Nd)-based catalyst in butadiene(Bd)polymerization has drawn interests due to its availability in affording higher cis-1,4-unit selectivity than transition metal(Ti,Co,Ni,etc.)-based catalysts[1-2].Such outstanding high cis-1,4-unit selecti-vity is hypothetically originated from the presence of 4 f orbitals,that can participate in monomer coordination and thereby govern subsequent enchainment manners.This unique characteristic also renders the active species highly susceptible to Lewis bases,and may impact the overall selectivity as well as polyme-rization behavior after coordination.Nevertheless,it is still a virgin area in such a field,and the influence of Lewis bases on Nd-based diene polymerizations is still a black box.Based on this consideration,how nitrogen-containing donors(D)impacts the overall behaviors of Nd-mediated Bd polymerizations is disclosed.

Synthesis and Characterization of Poly Styrene-Co-Poly 2-Hydroxyethylmethacrylate (HEMA) Copolymer and an Investigation of Free-Radical Copolymerization Propagation Kinetics by Solvent Effects

A series of homo and copolymers of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, tetrahydrofuran, and benzene) have been investigated by free radical polymerization method. The samples obtained from the synthesis were characterized by Fourier Transform-Infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The results show that the synthesis of the polymers is more feasible under neat conditions rather than solvent directed reaction. Moreover, the DSC data shows that the polystyrene obtained is amorphous in nature and therefore displayed only a glass transition signal rather than crystallization and melting peaks. In addition, this study indicates that homolopolymerization of styrene via free radical polymerization tends to be preferable in less polar solvents like THF than in non-polar solvents like benzene. Benzene might destabilize the formation of the reactive radicals leading to the formation of the products. In summary, the homolpolymerization of styrene is more feasible than the homopolymerization 2-hydroxyethyl methacrylate under the experimental setup used. Styrene is more reactive than 2-hydroxyethyl methacrylate than free radical polymerization reaction due in part of the generation of the benzylic radical intermediate which is more stable leading to the formation of products than alkyl radical which are less stable. Furthermore, polymerization of styrene under neat conditions is preferable in solvent-assisted environments. The choice of solvent for the synthesis of these polymers is crucial and therefore the selection of solvent that leads to the formation of a more stable reaction intermediate is more favorable. It is worth noting that the structure of the proposed copolymer consists of a highly polar and hydrophilic monomer, 2-hydroxyethyl methacrylate and a highly non-polar and hydrophobic monomer, styrene. These functionalities constitute an amphiphilic copolymer with diverse characteristics. A plausible explanation underlying our observations is that the reaction conditions employed in the synthesis of these copolymers might not be the right route required under free radical polymerization.

AQUEOUS STABLE FREE RADICAL POLYMERIZATION PROCESSES

An overview of aqueous polymerizations, which include emulsion, miniemulsion and suspension polymerizations, under stable free radical polymerization (SFRP) conditions is presented. The success of miniemulsion and suspension SFRP polymerizations is contrasted with the difficulties associated with obtaining a stable emulsion polymerization. A recently developed unique microprecipitation technique is referenced as a means of making submicron sized particles that can be used to achieve a stable emulsion SFRP process.

Mechanistically Novel Frontal-Inspired In Situ Photopolymerization:An Efficient Electrode|Electrolyte Interface Engineering Method for High Energy Lithium Metal Polymer Batteries

The solvent-free in situ polymerization technique has the potential to tailor-make conformal interfaces that are essential for developing durable and safe lithium metal polymer batteries(LMPBs).Hence,much attention has been given to the eco-friendly and rapid ultraviolet(UV)-induced in situ photopolymerization process to prepare solid-state polymer electrolytes.In this respect,an innovative method is proposed here to overcome the challenges of UV-induced photopolymerization(UV-curing)in the zones where UV-light cannot penetrate,especially in LMPBs where thick electrodes are used.The proposed frontal-inspired photopolymerization(FIPP)process is a diverged frontal-based technique that uses two classes(dual)of initiators to improve the slow reaction kinetics of allyl-based monomers/oligomers by at least 50%compared with the conventional UV-curing process.The possible reaction mechanism occurring in FIPP is demonstrated using density functional theory calculations and spectroscopic investigations.Indeed,the initiation mechanism identified for the FIPP relies on a photochemical pathway rather than an exothermic propagating front forms during the UV-irradiation step as the case with the classical frontal photopolymerization technique.Besides,the FIPP-based in situ cell fabrication using dual initiators is advantageous over both the sandwich cell assembly and conventional in situ photopolymerization in overcoming the limitations of mass transport and active material utilization in high energy and high power LMPBs that use thick electrodes.Furthermore,the LMPB cells fabricated using the in situ-FIPP process with high mass loading LiFePO_(4)electrodes(5.2 mg cm^(-2))demonstrate higher rate capability,and a 50%increase in specific capacity against a sandwich cell encouraging the use of this innovative process in large-scale solid-state battery production.

In Situ Directional Polymerization of Poly(1,3-dioxolane)Solid Electrolyte Induced by Cellulose Paper-Based Composite Separator for Lithium Metal Batteries

In traditional in situ polymerization preparation for solid-state electrolytes,initiators are directly added to the liquid precursor.In this article,a novel cellulose paper-based composite separator is fabricated,which employs alumina as the inorganic reinforcing material and is loaded with polymerization initiator aluminum trifluoromethanesulfonate.Based upon this,a separator-induced in situ directional polymerization technique is demonstrated,and the extra addition of initiators into liquid precursors is no longer required.The polymerization starts from the surface and interior of the separator and extends outward with the gradually dissolving of initiators into the precursor.Compared with its traditional counterpart,the separator-induced poly(1,3-dioxolane)electrolyte shows improved interfacial contact as well as appropriately mitigated polymerization rate,which are conducive to practical applications.Electrochemical measurement results show that the prepared poly(1,3-dioxolane)solid electrolyte possesses an oxidation potential up to 4.4 V and a high Li+transference number of 0.72.After 1000 cycles at 2 C rate(340 mA g^(−1)),the assembled Li||LiFePO_(4)solid battery possesses a 106.8 mAh g^(−1)discharge capacity retention and 83.5%capacity retention ratio,with high average Coulombic efficiency of 99.5%achieved.Our work may provide new ideas for the design and application of in situ polymerization technique for solid electrolytes and solid batteries.

Triggering dynamics of acetylene topochemical polymerization

Topochemical reactions are a promising method to obtain crystalline polymeric materials with distance-determined regio-or stereoselectivity.It has been concluded on an empirical basis that the closest intermolecular C⋅⋅⋅C distance in crystals of alkynes,d(C⋅⋅⋅C)min,should reach a threshold of∼3Åfor bonding to occur at room temperature.To understand this empirical threshold,we study here the polymerization of acetylene in the crystalline state under high pressure by calculating the structural geometry,vibrational modes,and reaction profile.We find d(C⋅⋅⋅C)min to be the sum of an intrinsic threshold of 2.3Åand a thermal displacement of 0.8Å(at room temperature).Molecules at the empirical threshold move via several phonon modes to reach the intrinsic threshold,at which the intermolecular electronic interaction is sharply enhanced and bonding commences.A distance–vibration-based reaction picture is thus demonstrated,which provides a basis for the prediction and design of topochemical reactions,as well as an enhanced understanding of the bonding process in solids.

Scale-up and thermal stability analysis of fluidized bed reactors for ethylene polymerization

A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode operation.The thermal stability of open-loop controlled FBRs is investigated by the homotopy continuation method.And the Hopf bifurcation point is selected as an index of the thermal stability similarity.The simulation results show the similarity in state variables,operation parameters,the space-time yield(STY),and the thermal stability of FBRs with different scales.Furthermore,the thermal stability behaviors and similarity of the closed-loop controlled FBRs with different scales are analyzed.The observed similar trend of Hopf bifurcation curves reveals the similarity in the thermal stability of closed-loop controlled FBRs with different scaling ratios.In general,the results of the thermal stability similarity confirm that the hydrodynamics scaling laws proposed in the work are applicable to the scale-up of FBRs under the condensed mode operation.

Preparation of Poly-α-Olefin Microcapsule Particles Coated with Polyurethane as a Drag Reducer Based on Interface Polymerization

The molecular behavior of polyurethane(PU)coating materials during the surface adsorption of poly-α-olefin as a drag reducing polymer was explored by a molecular dynamics simulation.Three different PU capsule wall materials were synthesized using two reaction monomers,and a poly-α-olefin/PU drag reducer microcapsule was prepared based on interface polymerization.The structure,morphology,thermal stability,compressive strength,and drag reduction performance of the microcapsules were characterized and compared.The results showed that a non-bonding interaction induced the adsorption of the PU coating material,poly-α-olefin and PU then fused at the interface,and the PU coating material was embedded into the inner grooves of poly-α-olefin in the form of a local mosaic,thereby forming a stable core–shell structure.The morphological characterization indicated that PU and poly-α-olefin could form microcapsule structures.The thermal decomposition temperature of the microcapsule was dependent on the type of capsule wall material.The microcapsule structure had a slight effect on poly-α-olefin drag reduction.The system enabled poly-α-olefin to exist in powdered particles through microcapsulation,and had a good dispersion effect that facilitated storage and transport processes.The method effectively inhibited the accumulation and bonding of poly-α-olefin at room temperature.

Apparent Kinetics of 1-Decene Polymerization Catalyzed Using the Ionic Liquid[Bmim]_(x)[C_(2)H_(5)NH_(3)]_(1-x)[Al_(2)Cl_(7)]

Poly-α-olefin(PAO)synthetic oil,a regular long-chain alkane produced from the catalytic polymerization ofα-olefin,is a high-quality lubricating base oil with huge market potential.In this study,PAO synthesis based on the catalytic polymerization of 1-decene using the ionic liquid(IL)[Bmim]_(x)[C_(2)H_(5)NH_(3)]_(1-x)[Al_(2)Cl_(7)]as the catalyst was studied.Compared with the conventional catalyst[Bmim][Al_(2)Cl_(7)],the obtained PAO product incorporates more trimers and tetramers of 1-decene and contains few double-bond end groups,demonstrating a better catalytic system for PAO-10 production.The apparent polymerization kinetics of 1-decene in this catalytic system were studied based on the 1-decene concentration,catalyst concentration,and reaction temperature.An apparent kinetic equation for PAO formation was determined,providing a promising strategy for PAO production using 1-decene polymerization.

Study on kinetics of propylene polymerizationat different temperatures via Monte Carlo simulation

The elementary reactions of propylene polymerization catalyzed by conventional Ziegler-Natta catalysts was proposed according to the comprehensive view and without considering the effect of any impurity in the material on propylene polymerization. The Monte Carlo simulation technique was employed to investigate the kinetics of propylene polymerization in order to determine the validity of the stationary state assumption and the effects of the polymerization temperature on the polymerization. The simulated total amount of active species, which only increases quickly at the beginning of the polymerization, indicates that the stationary state assumption in the studied system is valid. Moreover, significant effects of polymerization temperature on the polymerization conversion, and the molecular weight and its distribution were also analyzed. The simulated results show that the consumption rate of propylene increases with the increase of polymerization temperature; the maximum values of the number-average degree of polymerization are constant at different polymerization temperatures, however, the peak appears earlier with the higher temperature; as the polymerization temperature increases, the average molecular weight decreases and the molecular weight distribution changes greatly.

THE EFFECTS OF MONOMER STRUCTURE OF CYCLIC KETENE ACETALS ON THE BEHAVIOR OF CONTROLLED RADICAL RING-OPENING POLYMERIZATION

Polymerization of three cyclic ketene acetals: i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4phenyl-1,3-dioxolane (MPDO) and 4,7-dimethyl-2-methylene-1,3-dioxepane (DMMDO) were carried out in the presence of ethyl alpha -bromobutyrate/CuBr/2,2'-bipyridine respectively. The structures of poly(BMDO), poly(MPDO) and poly(DMMDO) were characterized by H-1 and C-13-NMR spectra. The effects of monomer structure on the behavior of atom transfer free radical ring-opening polymerization were investigated and the mechanism of controlled free radical ring-opening polymerization was discussed.

NARROW-DISPERSED CROSSLINKED CORE-SHELL POLYMER MICROSPHERES PREPARED BY SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

Grafting of polystyrene with narrowly dispersed polymer microspheres through surface-initiated atom transferradical polymerization(ATRP)was investigated.Polydivinylbenzene(PDVB)microspheres were prepared by dispersionpolymerization with poly(N-vinyl pyrrolidone)(PVP)as stabilizer.The surfaces of PDVB microspheres werechloromethylated by chloromethyl methyl ether in the presence of zinc chloride as catalyst to form chloromethylbenzeneinitiating core sites for subsequent ATRP grafting of styrene using CuCl/bpy as catalytic system.Polystyrene was found to begrafted not only from the particle surfaces but also from within a thin shell layer,resulting in the formation of particles sizeincreased from 2.38-2.58 μm,which can further grow to 2.93 μm during secondary grafting polymerization of styrene.Thisdemonstrates that grafting polymerization proceeds through a typical ATRP procedure with living nature.All of the preparedmicrospheres have narrow particle size distribution with coefficient of variation around 10%.

Polymerization Mechanism of α-Linear Olefin

The density functional theory on the level of B3LYP/6-31G was empolyed to study the chain growth mechanism in polymerization process of α-linear olefin in TiCl3/AlEt2Cl catalytic system to synthesize drag reduction agent. Full parameter optimization without symmetry restrictions for reactants, products, the possible transition states, and intermediates was calculated. Vibration frequency was analyzed for all of stagnation points on the potential energy surface at the same theoretical level. The internal reaction coordinate was calculated from the transition states to reactants and products respectively. The results showed as flloes： （i） Coordination compounds were formed on the optimum configuration of TiCl3/AlEt2Cl.（ii） The transition states were formed. The energy di？erence between transition states and the coordination compounds was 40.687 kJ/mol. （iii） Double bond opened and Ti-C（4） bond fractured, and the polymerization was completed. The calculation results also showed that the chain growth mechanism did not essentially change with the increase of carbon atom number of α-linear olefin. From the relationship between polymerization activation energy and carbon atom number of the α-linear olefin, it can be seen that the α-linear olefin monomers with 6-10 carbon atoms had low activation energy and wide range. It was optimum to synthesize drag reduction agent by polymerization.