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Synthetic Features and Mechanism for the Preparation of Vinyl Chloride-co-Butyl Acrylate-co-Vinyl Acetate Terpolymer via Precipitation Polymerization

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Chinese Journal of Polymer Science 2023年第11期41卷 1714-1724,I0006页

作者： Chang-Tong Song Xian-hong Zhang Dong Chen Yu-Hong Ma Wan-Tai Yang State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing 100029China College of material Science and Engineering Beijing University of Chemical TechnologyBeijing 100029China

Without any type of su rfactant or dispersing agent,precipitation polymerization has great superiorities in both polymer synthesis and applications.In the present work,the polymerization of vinyl chloride(VC),n-butyl acrylate(BA),and vinyl acetate(VAc)are conducted in the precipitation polymerization system and series of their random terpolymers poly(vinyl chloride-co-n-butyl acrylate-co-vinyl acetate)(PCBV)are synthesized successfully.The effects of various polymerization conditions,including solvent polarity,temperature,initiator concentration,and monomer feed ratios on the polymerization kinetics,number-average molecular weight(M_(n)),and terpolymer composition are investigated systematically.The solvent and the monomer feed ratio are crucial factors not only for the polymer morphology,but also for the reaction kinetic.In the non-polar solvent such as n-hexane,the PCBV displays particle morphology when the composition of BA ratio lower than 10 wt%.Otherwise,the PCBV forms a uniform polymer phase and precipitates out from the mixture.In the polar solvent,e.g.,dimethyl carbonate(DMC)and ethanol,the PCBV polymer maintains a slurry state either in low or in high monomer feed ratio.Impressively,VC based ternary copolymer that obtained in n-hexane has much lower M_(n)(mass fraction(>40 wt%)compared with emulsion and suspension polymerization.Additionally,the terpolymer can be easily sepa rated by simple centrifugation.

关键词： Precipitation polymerization Copolymerization Vinyl chloride Low molecular weight

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Stabilizing interface of SmCo_(5)/Co nanocomposites by graphene shells

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Rare Metals 2022年第4期41卷 1223-1229页

作者： Zhen-Hui ma hong-yu Du Department of Physics Beijing Technology and Business UniversityBeijing 100048China

In this work,we proposed a novel chemical strategy to synthesize exchange-coupled SmCo_(5)/Co nanocomposites by using graphene shells to stabilize the interface.In our synthesis,the SmCo-OH/GO(graphene oxide)precursor prepared by co-precipitation method could be first reduced by calcium to yield 15-nm SmCo_(5)/GN(graphene)single-crystal nanoparticles,and then 8-nm Co particles were deposited on the surface of SmCo_(5)/GN to yield SmCo_(5)/GN/Co nanocomposites.

关键词： graphene shells interface

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Conventional Radical and RAFT Alternating Copolymerizations of Hydroxyalkyl Vinyl Ethers and Dialkyl maleates

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Chinese Journal of Polymer Science 2023年第12期41卷 1856-1867,I0006页

作者： Yan-Xin Zhang Dong Chen Gao-Fei Hu Yu-Hong Ma Wan-Tai Yang Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers College of materials Science and Engineering Beijing University of Chemical TechnologyBeijing 100029China Analytical and Testing Center Beijing University of Chemical TechnologyBeijing 100029China

The alternating copolymerization of hydroxyalkyl vinyl ethers and dialkyl maleates is investigated by conventional radical polymerization and reversible addition-fragmentation chain transfer polymerization(RAFT).The influence of comonomer structure,comonomer feeding ratios,and monomer concentrations on the copolymerization and the copolymer structure have been investigated systematically.With 2-hydroxyethyl vinyl ether(HEVE)and dimethyl maleates(DMM)as comonomers,a well-defined alternating copolymer is prepared with M_(n)=3400 and M_(w)/M_(n)=1.93 up to 71.6% monomer.The alternating sequential chain structure of the copolymers has been proved by both NMR and matrixassisted laser desorption/ionization time-of-flight mass spectrometry(maLDI-TOF MS).The experimental reactivity ratios and theoretical calculated highest occupied molecular orbital and the lowest unoccupied molecular orbital of vinyl ethers and alkyl maleates support that these monomer pairs have tendency to form alternating copolymers.With 2-cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)carbamodithioate as the RAFT agent,the molecular weight of HEVE and DMM copolymer increases with the monomer conversion,demonstrating a controlled radical polymerization feature with well-controlled molecular weight and relatively narrower molecular weight distribution.With alternating copolymer of HEVE and DMM as macro-CTA(M_(n)=5200 and M_(w)/M_(n)=1.46),both the chain extension with HEVE and DMM(M_(n)=10400 and M_(w)/M_(n)=1.72)and block copolymerization with vinyl acetate have been successfully achieved(M_(n)=8500 and M_(w)/M_(n)=1.52).

关键词： Radical polymerization Vinyl ethers maleates Alternating copolymer RAFT polymerization

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Polypropylene/Silica Nanocomposites in situ Prepared via Sol-Gel Reactions Using Porous Spherical Poly(propylene-g-(styrene-alt-maleic anhydride)) Granules as Reaction Loci

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Chinese Journal of Polymer Science 2015年第12期33卷 1730-1740页

作者： Zhuo Li Yu-Hong Ma 杨万泰 The State Key Laboratory of Chemical Resources Engineering Beijing University of Chemical Technology Key Laboratory of Carbon Fiber and Functional Polymers Ministry of Education Beijing University of Chemical Technology

Using the porous polypropylene （PP） granules consisting of submicroparticles prepared by the reactor granular technology （RGT）, a facile process was developed to synthesize in situ polypropylene/silica nanocomposites where styrene- alt-maleic anhydride copolymers （PSM） were firstly grafted onto both the outer- and the inner-pore surfaces of PP granules via solid-phase grafting polymerization, and then a sol-gel reaction was conducted inside these micro-pores with the carboxyl acid derived from maleic anhydride as catalyst. TEM micrographs demonstrated that the silica nanoparticles obtained by this strategy had a size around 10-20 nm in diameter and uniformly dispersed in the PSM-based nanocomposites. More importantly, the silica nanoparticles could significantly reduce the size of PP spherulites. Consequently, the PP/silica nanocomposites with high transparency and good mechanical performance were achieved.

关键词： Nanocomposites Solid-state polymerization Silica.

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Ferrite-based composites and morphology-controlled absorbers

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Rare Metals 2022年第9期41卷 2943-2970页

作者： yu Mu Zhen-Hui ma hong-Sheng Liang Li-Min Zhang hong-Jing Wu MOE Key Laboratory of material Physics and Chemistry Under Extraordinary School of Physical Science and TechnologyNorthwestern Polytechnical UniversityXi’an710072China Department of Physics Beijing Technology and Business UniversityBeijing100037China

The exploration of lightweight and efficient electromagnetic wave(EMW)absorption materials is a crucial focus topic because the human body and precision instruments are exposed to the increasingly serious electromagnetic pollution.Ferrite,as the first type of EMW absorption material,is still the indelible superstar in the EMW absorption field due to its unique double loss mechanism,controllable morphology and high permeability.This review briefly introduces the EMW absorption and attenuation mechanism of ferrite-based composite absorbers,including dielectric loss dominated by charge transfer and polarization relaxation,and magnetic loss consisted of eddy current and resonance.Moreover,we comb the advances in synthesis of ferrite materials.In particular,this paper summarizes the advantages and defects of pure ferrite as EMW absorption material.And the approach to tackling the imbalance of impedance matching and highdensity in ferrite is also reviewed,including ion substitution,design of micro-morphology and doping with dielectric loss materials.

关键词： Electromagnetic wave absorption(EMWA) Ferrite Attenuation mechanism Synthetic method Modification

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Application of complex nonlinear modes to determine dry whip motion in a rubbing rotor system

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Chinese Journal of Aeronautics 2021年第1期34卷 209-225页

作者： Pingchao yu Yanhong ma Jie hong Guo CHEN College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Achanceci Aero-Engine Beihang UniversityBeijing 100083China

Dry whip motion is an instability of rubbing rotor system and may cause catastrophic failures of rotating machinery.Up to now,the related mechanisms of the dry whip is still not well understood.This paper aims to build the relationship between the complex nonlinear modes and the dry whip motion,and propose an effective method to predict the response characteristics and existence boundary of the dry whip through complex nonlinear modes.For the first time,the paper discusses how to use the complex nonlinear modes to predict the dry whip systematically,and as a consequence,the mechanism of the relationship between the complex nonlinear mode and the dry whip is revealed.The results show that the Backward Whirl(BW)mode motion of the rubbing rotor system dominates the response characteristics and the existence boundary of dry whip.The whirl amplitude and whirl frequency of dry whip are equal to the modal amplitude and modal frequency of the BW mode at the jump up point where the modal damping is equal to zero.The existence boundary corresponds to the critical rotation speed where the minimum of the modal damping of the BW mode motion is exactly equal to zero.Moreover,the proposed nonlinear modal method in this article is very effective for the prediction of dry whip of the more complicated practical rotor system,which has been verified by applying the predicted method into a rubbing rotor test rig.

关键词： Complex nonlinear mode Dry whip Existence boundary Response characteristics

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Interfacial phenomena of water striders on water surfaces: a review from biology to biomechanics

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Zoological Research 2020年第3期41卷 231-246页

作者： Jing-Ze ma hong-yu Lu Xiao-Song Li yu Tian State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Water striders have intrigued researchers for centuries from the viewpoints of biology to biomechanics. In this review, we introduce the basic theories and techniques of physics and force measurement for biomechanical research into water striders. Morphological and behavioral traits of water striders are summarized and discussed from biomechanical perspectives, along with comparative study. This integrated review also highlights potential directions for studies on water-walking arthropods,which might inspire future biological and biomechanical research.

关键词： Water strider Water repellency Surface tension Surface propulsion

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Investigation on nonlinear lateral-torsional coupled vibration of a rotor system with substantial unbalance

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Chinese Journal of Aeronautics 2020年第6期33卷 1642-1660页

作者： Jie hong Pingchao yu Yanhong ma Dayi ZHANG School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced Aero-Engine Beihang UniversityBeijing 100083China Beijing Key Laboratory of Aero-Engine Structure and Strength Beijing 100083China

Substantial unbalance may be caused by fan blade off during the operation period of gas turbine engines,and related dynamic problems are very critical to the safety design of rotor system in aero-engine.This article aims to understand lateral-torsional coupled vibration of the rotor system with substantial unbalance.The governing equation of a modified unbalanced rotor system is established based on Lagrangian approach.Then,a mathematical analytical method is proposed in which a linear approximation is derived and the Floquet theory and Hill’s method are incorporated,from which the modal characteristics of the unbalanced rotor are obtained.The modal characteristics of the unbalanced rotor system are revealed comprehensively for the first time.Furthermore,the relation between the modes and responses of the unbalanced rotor is discussed in detail.The results show that the lateral vibration and torsional vibration of the unbalanced rotor are coupled through the inertial terms in the governing equations.Due to the coupling,veering and lock-in phenomena occur between the frequencies of the forward whirl mode and the torsional mode.Furthermore,lock-in can lead to a kind of principal instability.With regard to the response of the unbalanced rotor,both natural vibration components and enforced vibration components appear in the lateral response,while only natural vibration components appear during torsional vibration.Moreover,natural vibration components play a crucial role in the response within the principal instability region and cause divergence of the vibration amplitudes in the lateral and torsional directions.

关键词： Instability Lateral-torsional coupled vibration Lock-in phenomenon Modes Unbalanced rotor

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Preparation of Ultralow Molecular Weight Poly(vinyl chloride) with Submicrometer Particles via Precipitation Polymerization

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Chinese Journal of Polymer Science 2019年第7期37卷 646-653页

作者： Peng Cui Chang-Tong Song Xian-hong Zhang Dong Chen Yu-Hong Ma Wan-Tai Yang State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing 100029China College of material Science and Engineering Beijing University of Chemical TechnologyBeijing 100029China

Poly(vinyl chloride), with ultralow molecular weight, produced by free radical polymerization either at high temperature or in the presence of chain transfer agents, is widely used as special resins and polymer process additives. This paper reports a new process, called self-stabilized precipitation polymerization, in which the polymerization of vinyl chloride monomer (VCM) is conducted in hydrocarbon diluents without addition of any suspending agent or emulsifier. The merits of this novel strategy include:(1) PVC resins with ultra-low number-average molecular weight (Mn) from 4000 to 15000, which is much lower than Mn of those prepared by conventional suspension and emulsion polymerizations,(2) sub-micrometer PVC particles with near spherical morphology, and (3) the very simple post-polymerization separation process. Under mild stirring, polymerization proceeds stably and smoothly. The influences of main process factors, such as solvents, initiator and monomer concentrations, polymerization time, and temperature on both particle morphology and Mn of the polymer products are investigated systematically. The molar ratio of-CH2-CHCl-/-CH=CH-CH2CHCl, a good indicator of structural defects, is about 1000/0.1 which means the low molecular weights do not result from chain transfer to the monomers. Then the mechanism of this polymerization is proposed. In summary, this novel polymerization technology provides a straightforward method for preparing PVC particulate products with low Mn.

关键词： Precipitation polymerization Vinyl chloride Ultralow molecular weight Pure product

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Bio-inspired low-tortuosity carbon host for high-performance lithium-metal anode

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National Science Review 2019年第2期6卷 247-256页

作者： Yi-Chen Yin Zhi-Long yu Zhi-yuan ma Tian-Wen Zhang yu-Yang Lu Tao ma Fei Zhou hong-Bin Yao Shu-hong yu Department of Chemistry CAS Center for Excellence in Nanoscience Hefei Science Center of CAS University of Science and Technology of China Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China CAS Key Laboratory of Mechanical Behavior and Design of materials Department of Modern MechanicsUniversity of Science and Technology of China

Lithium metal is one of the most promising anode materials for high-energy-density Li batteries. However,low stability caused by dendrite growth and volume change during cycling hinders its practical application.Herein, we report an ingenious design of bio-inspired low-tortuosity carbon with tunable vertical micro-channels to be used as a host to incorporate nanosized Sn/Ni alloy nucleation sites, which can guide Li metal’s plating/stripping and meanwhile accommodate the volume change. The pore sizes of the vertical channels of the carbon host can be regulated to investigate the structure–performance correlation. After compositing Li, the bio-inspired carbon host with the smallest pore size（～14 μm） of vertical channels exhibits the lowest overpotential(～18 mV at 1 ma cm;), most stable tripping/plating voltage profiles,and best cycling stability（up to 500 cycles） in symmetrical cells. Notably, the carbon/Li composite anode is more rewarding than Li foil when coupled with LiFePO;in full cells, exhibiting a much lower polarization effect, better rate capability and higher capacity retention（90.6% after 120 cycles）. This novel bio-inspired design of a low-tortuosity carbon host with nanoalloy coatings may open a new avenue for fabricating advanced Li-metal batteries with high performance.

关键词： bio-inspiration low-tortuosity carbon host lithium metal micro-channels nucleation sites

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