STABILITY OF EMULSIFIER-FREE EMULSION COPOLYMERIZATION OF METHYL METHACRYLATE/BUTYL ACRYLATE/SODIUM MONO(ETHYL POLYOXYETHYLENE)MALEATE

A series of new water-soluble bifunctional comonomers having both carboxyl and alkyl polyoxyethylene groups, such as sodium mono(ethyl polyoxyethylene) maleate (ZE series) with various molecular weights of polyoxyethylene ethyl ether, were synthesized and characterized. The effects of the structural factor, the amount and feeding mode of the comonomers, the initiator concentration and polymerization temperature on the stability of emulsifier-free emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) in the presence of a small amount of ZE with potassium persulfate as initiator were investigated. Stable, almost monodispersed MMA/BA/ZE emulsifier-free latex particles were prepared.

Semibatch Emulsifier-free Emulsion Copolymerization of Methyl Methacrylate and n-Butyl Acrylate in the Presence of 2-Hydroxyethyl Methacrylate

The semibatch emulsifier-free emulsion copolymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA) in the presence of 2-hydroxyethyl methacrylate (HEMA) initiated by K2S2O8 (PSP) was studied. The average particle diameter increases with an increase of total solids content, HEMA content, PSP content, ionic strength of the system and monomer feed rate, and decreases with the monomer feed ratio from 3/1 (MMA/BA mole.) to 1/3. The stability of this reaction system is improved by adding HEMA as nonionic comonomer. The high solids content (50%) latex with monodisperse particle can be obtained using this process.

EFFECT OF 2-HYDROXYETHYL METHACRYLATEON SEMIBATCH EMULSIFIER-FREE EMULSION COPOLYMERIZATION OF METHYLMETHACRYLATE AND BUTYL ACRYLATE

The semibatch emulsifier-free emulsion copolymerization of methyl methacrylate(MMA and butyl acrylate (BA) in the presence of 2-hydroxyethyl methacrylate (HEMA)initiated by K2S2O8 (PSP) was studied. The latex particles can maintain an appreciablestability during the emulsifier-free emulsion copolymerization of MMA and BA in thepresence of HEMA The average particle diameter increase with an increase of totalsolids content, HEMA content, PSP content, ioniC strength of the system and monomerfeed rate, and decrease with the monomer feed ratio From 3/1(MMA/BA;molar ratio.)to1/3. The stability of this reaction system is improved by adding HEMA as nonioniccomonomer High solids content (50%) latex with monodisperse particle can beobtained using this process.

EFFECTS OF ω-ACRYLOYL POLY (ETHYLENE OXIDE) MACROMONOMER ON EMULSIFIER-FREE EMULSI0N COPOLYMERIZATION OF METHYL METHACRYLATE AND n-BUTYL ACRYLATE

Well-defined nonionic hydrophilic ω-acryloyl poly(ethylene oxide) macro-monomer (PEO-A) has been prepared by living anionic polymerization of ethylene oxidewith diphenyl methyl potassium as the initiator and acryloyl chloride as the reaction termi-nating agent. The polymer was characterized by FTIR and SEC. The emulsifier-free emul-sion polymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA) containingvarious concentrations of PEO-A was studied. In all cases stable emulsion coplymerizationsof MMA and BA were obtained. The stabilizing effect was found to be dependent on themolecular weight and the feed amount of the macromonomer.

CATALYTIC COPOLYMERIZATION OF STYRENE AND ETHYLENE BY NEUTRAL NICKEL(Ⅱ) COMPLEXES IN EMULSION

Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(Ⅱ) complexes was carried out in an aqueous system to give high-molecular-weight copolymers.The copolymers and emulsions were characterized by an array of techniques including NMR,GPC,TEM,WAXD and DSC.The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units,and their M_W is in the range of 10~5-10~6.By enhancing the electron withdrawing of the s...

STUDY ON THE FORMATION MECHANISM OF MONODISPERSE PARTICLES IN THE EMULSIFIER-FREE EMULSION POLYMEAIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerizationof methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formationmechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be thecoagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with highsurface charge density and sufficient stability. It had been proved by a special experiment that the early latex particles formedby the coagulation were stable. The primary particles grow by absorbing monomers and radicals in the polymerization systemand then become colloidally unstable again due to the understandable decrease of particle surface charge density, which leadsto the aggregation of the growing particles and the formation of larger latex pedicles therefrom. Aner the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards auniform size and narrower particle size distribution. The coexistence and competition of homogeneous nucleation,coagulation, propagation and aggregation result in the increase of the polydispersity index (U = D_(43)/D_(10)) in the first Stage,then its decrease in the later stage because of the competition of propagation and aggregation, and the gradual formation ofthe monodisperse particles.

SOAPLESS EMULSION COPOLYMERIZATION IN THE PRESENCE OF BARIUM SULFATE POWDER

To investigate soapless emulsion copolymerization in the presence of a solid phase, copolymerization experiments were carried out for the styrene-butyl acrylate-K_2S_2O_8-water system by using barium sulfate powder,which is assumed to be chemically inert.Reaction conditions were varied with respect to barium sulfate powder quantity,initiator concen- tration and temperature.These factors were investigated with respect to the effect on reaction rate and conversion,polymer particle number and diameter,and latex stability.

Self-assembly of Gradient Copolymer Synthesized by Spontaneous Batch RAFT Emulsion Polymerization and Its Application on Encapsulating Ag Nanoparticles

The gradient copolymers of acrylic acid and trifluoroethyl methacrylate（coded as P（TFEMAgrad-AA）） were synthesized via reversible addition-fragmentation transfer（RAFT） emulsifier-free emulsion polymerization. The spontaneous batch feeding approach was used to control the gradient chain sequence. Transmission electron microscopy（TEM） analysis revealed that the P（TFEMA-grad-AA） can self-assemble to form spherical micelles, rodlike micelles or vesicles in selective solvents. Morphological transition of the P（TFEMA-grad-AA） micelles was sensitive to the water content of the dioxane/water mixed solvent. More interestingly, Ag nanoparticles（NPs） were encapsulated by the P（TFEMA-grad-AA） micelles during the selfassembly process. The gradient chain sequence made the Ag NPs easily enter the core of the micelles, even when P（TFEMA-grad-AA） had less hydrophobic fluoro-units and more hydrophilic units. TEM images with energy dispersive spectrometer indicated that the nanocomposite micelles consisted of a Ag NPs core and a gradient copolymer shell.

Study on N-Phenylmaleimide/Styrene /Acrylonitrile Copolymer Prepared by Emulsion Polymerization

The emulsion polymerization of N-phenylmaleimide, Styrene and acrylonitrile was studied. The thermal property of this copolymer was measures by dynamic thermomechanical analysis(DMA). The mechanical properties, such as tensile strength, hardness and fie-cural Strength were StUdied experimentally. The results indicated that not only the monomer component but also the polymerization technologies have effect on the properties of the copolymer. The optimum monomer content and suitable polymerization method were obtained.

Synthesis of submicron-sized composite particles with unique morphology by emulsifier-free seeded emulsion copolymerization

Polystyrene （PSt） microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate （KPS） as initiator in ethanol-water mixed solvents. Emulsifier-free seeded emulsion copolymerization of styrene （St） with acrylonitrile （AN） was carried out in the presence of poly（ethylene glycol） monomethoxymonomethacrylate （PEGm） macromonomer as reactive stabilizer and 2,2＇-azobisisobutyronitrile （AIBN） as initiator to obtain submicron-sized PEGm graft poly（styrene-coacrylonitrile） （PEGm-g-PSAN） composite particles with unique morphology. Scanning electron microscopy （SEM） indicated that St and AN together contributed to forming the unusual morphology. The concentration of St and AN, total monomer concentration, initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles.

Ether-/Ester-/Fluorine-Rich Binding Emulsion Formula for Lithium-Ion Batteries

Practical application of a Si anode in a high-energy-density battery cannot be achieved due to the huge volume expansion of these anodes.Researchers have focused on binders of the anode to restrict volume expansion in order to address this issue,as the hydrogen bonds and mechanical properties of binders can be used to enhance adhesion and accommodate the volume changes of a Si anode.Herein,we comprehensively consider binders’hydrogen bonds,mechanical properties,stability,and compatibility with the electrolyte solution,and design an ether-/ester-/fluorine-rich composite polymer,named P(TFEMAco-IBVE).The proposed binder formula possesses outstanding stability,adhesion,and mechanical strength;moreover,it can accommodate the dramatic volume changes of a Si electrode and exhibits excellent electrochemical performance,achieving a high areal capacity of about 5.4 mA·h·cm^(-2).This novel polymer design may be applied to other electrode materials in the next generation of lithium-ion batteries.

INFLUENCES OF ACID POST-TREATMENT ON THE MORPHOLOGY OF SOAP-FREE P(MMA-EA-MAA)PARTICLES PREPARED BY SEEDED EMULSION POLYMERIZATION

Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.

Emulsion confined block copolymer self-assembly:Recent progress and prospect

In the past few decades,significant progress in block copolymer self-assembly has been achieved in many fields,and with the development of nanoscience and nanotechnology,more and more complex situations need block copolymer self-assembly based nanoplatforms having more complex structures for specific multimodal or multiplexed applications.Through the combination of emulsification and self-assembly of the block copolymer,different materials with exotic architectures and functions could be combined within an entity,such as controlled vesicles,Janus particles,and composite particles which are more like ideal nanoplatforms.Various designs can show their different desired properties depending upon the application situation,including molecular delivery,surfactants,and multicolor encoding.This review will provide a complete summary of the optimization and the synthesis method for the recently designed emulsion confined block copolymer assemblies,and also the challenges and limitations this method faces,and the potential solutions in this field.

Oxidation-responsive framboidal triblock copolymer vesicles prepared by photoinitiated RAFT seeded emulsion polymerization

Stimulus-responsive vesicles have broad applications in a variety of areas. Herein, oxidation-responsive framboidal triblock copolymer vesicles are prepared by photoinitiated RAFT seeded emulsion polymerization of a thioether-functionalized monomer using diblock copolymer vesicles as seeds. The obtained framboidal vesicles can transform into worms or spheres in the presence of reactive oxygen species,which can be further used for controlled release of cargos(e.g., silica nanoparticles).

Engineering the Morphologies of Block Copolymer Particles from the Confined Self-assembly within Emulsion Droplets

Block copolymers(BCPs)can automatically assemble into various regulated nanoparticles when they are confined within the emulsion droplet be-cause of the structural frustration of polymer chains and the soft template effect of the oil/water interface.In the past few years,great efforts have been made to regulate the morphologies of the resulting BCP particles.In this review article,various strategies for tuning oil/water interfacial prop-erties to engineer the as-formed BCP particles were summarized.Then,the comprehensive scenarios of the applications of the resulting BCP parti-cles were discussed.Finally,the future tendency and challenge of the self-assembly of BCPs confined in emulsion droplet were suggested.

One-step synthesis of self-healable hydrogels by the spontaneous phase separation of linear multi-block copolymers during the emulsion copolymerization

Self-healable polyacrylamide-based hydrogels were prepared at room temperature via a one-step emulsion copolymerization of acrylamide（AM）,dodecyl 2-methacryIate（DM）,and 5-acetylaminopentyl acrylate（AAPA） using sodium dodecyl sulfonate（SDS） as the emulsifier and ammonium persulfate（APS）as the initiator.The produced linear multi-block copolymer chains are composed of randomly-linked hydrophilic polyacrylamide segments（PAM） and hydrophobic segments constituted by DM and AAPA units（P（DM-co-AAPA））.The P（DM-co-AAPA） segments will self-aggregate into hydrophobic microdomains during the polymerization process driven by the hydrophobic interactions,and finally separate from water phase,acting as the crosslinks and leading to the formation of strong hydrogels with a storage modulus as high as 400 Pa.These hydrophobic microdomains will be dissolved in water when the temperature increases to 70℃,resulting in a temperature-responsive reversible sol-gel transition of the prepared hydrogels.Furthermore,the prepared hydrogels have excellent self-healing ability.The broken hydrogels can be automatically healed into a body with a same strength within 2-min＇s contact.This work provides a new simple way to prepare reversible physical crosslinked hydrogel with high strength and self-healing efficiency.

Effect of stirring on preparation of hollow copolymer particles by alkali/cooling method

Hollow particles were prepared by the treatment of styrene-methacrylic acid copolymer particles with alkali/cooling method. The influences of stirring position (in aqueous phase or at the interface of O/W) and stirring speed (90, 110 and 240 r/min) on the formation of hollow particles were investigated. It is found that the soft stirring in aqueous phase at 90 r/min leads to the formation of monohollow particles, while the violent stirring at the interface of O/W and 240 r/min gives non-hollow products. In contrast, the weak stirring in aqueous phase at 110 r/min results in sterically heterogeneous dispersion of methacrylic acid-rich regions within the original particles, and hence the formation of multihollow particles. Further investigation indicates that the change of stirring efficiency provides a way to tune the diffusion behavior of monomer styrene, and therefore influences the distribution of methacrylic acid units in the original particles as well as the morphology of the treated particles.

共聚改性聚偏氟乙烯水性乳液制备及应用研究

为了制备高固含量、长期贮存稳定、可常温固化的含氟聚合物水性乳液,借鉴无皂乳液聚合技术在偏氟乙烯聚合过程中加入全氟或多氟烷基氧化胺型表面活性剂,以偏氟乙烯-六氟丙烯(VDF-HFP)共聚物为种子乳液,丙烯酸类单体共聚物为壳层,通过优化共聚组分含量、聚合工艺条件,共聚改性制备高固含量聚偏氟乙烯水性乳液。结果表明:制备的水性PVDF乳液固含量40%~53%,放置4个月仍保持颗粒原始状态,高速搅拌剪切未出现凝聚现象,常温固化后的漆膜外观平整光滑,表面无缺陷。经施工及涂膜性能测试评价,共聚改性PVDF水性乳液喷涂、辊涂施工正常,漆膜综合性能与溶剂型PVDF涂料相当。

用丙烯腈接枝改性脱蛋白天然胶乳及其自修复性能

采用乳液接枝共聚法,以脱蛋白天然橡胶(DPNR)为基体,丙烯腈(AN)和丙烯酸(AA)为单体,在叔丁基过氧化氢/四乙烯五胺引发体系下,合成了DPNR接枝AN和AA共聚物[DPNR-g-P(AN-coAA)]。通过红外光谱、核磁共振波谱等验证了AN及AA单体的接枝,研究了单体总量及m(AN)/m(AA)对改性DPNR力学性能的影响,以及修复条件对其自修复性能的影响。结果表明,在单体总量为10份(以干胶质量计)、m(AN)/m(AA)为10/1的条件下,DPNR-g-P(AN-co-AA)的最大拉伸强度和扯断伸长率分别为9.22 MPa和1365%,分别是初始DPNR的376%和133%。此外,体系中聚丙烯酸链段间的氢键相互作用使得DPNR-g-P(AN-co-AA)兼具优异的自修复性能,在50℃时愈合2 h可达到75.3%的自修复效率。

Emulsion Binders with Multiple Crosslinked Structures for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries suffer a lot from the huge volume change and the shuttle effect. However, conventional poly(vinylidene fluoride) binder has intrinsic drawbacks, such as low ion conductivity, weak polysulfide-trapping ability, poor mechanical properties, and requirement of organic solvents. Herein, we designed a functional emulsion binder with multi crosslinked structure. Such a structure was formed by the covalent crosslinking within and between the emulsion particles, which facilitates the adapting of the volume expansion of sulfur cathode, thereby ensuring the integrity of electrodes. Besides, the polar functional groups endow the binder with strong chemisorption of lithium polysulfide and fast lithium-ion migration ability. Thus, the assembled lithium-sulfur battery displayed a high initial discharge capacity of 1246 mAh·g^(−1) at 0.1 C, and a capacity fading rate of 0.04% per cycle after 500 cycles at 0.5 C. Even at a high sulfur mass loading of 4.8 mg·cm^(−2), a high capacity of 956 mAh·g^(−1) was still obtained at 0.2 C.