Greffage de styrene et de styrene-acrylonitrile sur polybutadiene—comparaison des masses moléculaires

Polymerization of styrene in the presence of different types of polybutadiene leads to polystyrene (PS) grafted on to rubber and to free PS. It is shown that a difference in molecular weight exists between grafted and free PS; the molecular weight of grafted PS is systematically higher than that of free PS. A comparison to ABS systems has been made by grafting styrene and styrene-acrylonitrile in the same conditions on to polybutadiene. It appears that the difference in molecular weight between grafted and non-grafted polymer is much more pronounced in the case of ABS. These results can be explained by considering a decrease of the termination rate constant (k_t) in consequence of the local viscosity variations near the polybutadiene coils and by taking into account its preferential solvation by monomer and initiator.     

新型室温酯化法接枝聚合物改性SiO_2纳米微粒

提出了一种在室温、大气环境等温和条件下通过酯化反应将端羧基聚合物链接枝到纳米SiO2微球表面从而制备有机/无机复合纳米微粒的新方法.该方法通过以下两个步骤得以实现,即第一,用3-环氧丙基三甲氧基硅烷对纳米SiO2微球表面进行改性处理,接着将引入到纳米SiO2表面的环氧基团转化为烷羟基基团;第二,通过引入到纳米SiO2微球表面的烷羟基与聚合物中的端羧基在室温下发生酯化反应,从而将聚合物接枝到纳米SiO2表面制得复合微球.利用XPS、FTIR、TEM和TGA等测试手段对纳米SiO2的改性过程以及聚合物接枝后得到的复合微球进行了表征.研究结果表明,该室温酯化接枝方法具有较高的接枝率,接枝到无机纳米微粒表面的聚合物占复合微球质量的55wt%～70wt%;接枝聚合物后,纳米SiO2微球的粒径从40nm增加到64～75nm,从而得到了以SiO2为核、以聚合物为壳的有机-无机复合微球.     

Effect of GMA polymer compatibilizers on highly filled composites of low density polyethylene/magnesium hydroxide

Functional polymers such as polyethylene grafted glycidyl methacrylate （PE-g-GMA） and ethylene-methyl acrylate-glycidyl methacrylate terpolymer （E/MA/GMA） were used as compatibilizers in the preparation of highly filled composites of polyethylene/magnesium hydroxide（PE/MH）. Comparative studies were performed on the effect of magnesium hydroxide and stearic acid on the interface within polymer and magnesium hydroxide composites. The effect of polymeric compatibilizers on the properties of the composites was studied using tensile and impact tests, torque rheological analysis, differential scanning calorimetry and environmental scanning electron microscopy （ESEM）. The microstructure of highly filled PE/MH composites changed after the addition of functional polymers. The mechanical properties of the composite material increased after compatibilization. The compatibilization processes of PE-g-GMA and E/MA/GMA were different. The grafted polymer was more compatible with polyethylene, which led to a polar polymer phase. In contrast, the tercopolymer tended to adhere to the surface of MH particles.     

The morphology of composite polymer particles produced by multistage soapless seeded emulsion polymerization

 Composite polymer particles which contain poly(methyl methacrylate) (PMMA) and polystyrene (PS) components (PMMA/PS composite particle) were synthesized by the method of multistage soapless seeded emulsion polymerization. In this study, the process of multistage soapless seeded emulsion polymerization included two-stage polymerization, three-stage polymerization or four-stage polymerization. The morphologies of the PMMA/PS composite particles were studied. The kinetic factor was the main force to control the morphology of the linear PMMA–PS composite particles which were synthesized by the method of two-stage reaction. Both the kinetic factor and the thermodynamic factor decide the morphology of the linear composite particles which were synthesized by the method of either three-stage or four-stage reaction. However, the thermodynamic factor cannot influence the morphology of the PMMA/PS composite particles with a cross-linked structure which were synthesized by the method of three-stage reaction. The cross-linked composite polymer particles had the morphology of a multilayer structure, which showed that the polymer layers accumulated in their order of production. Received: 9 January 2001 Accepted: 14 June 2001     

The influence of core-shell structured modifiers on the toughness of poly (vinyl chloride)

The core-shell structured grafted copolymer particles of polybutadiene grafted polymethyl methacrylate (PB-g-PMMA, MB) were prepared by emulsion polymerization. The MB particles were used to modify poly (vinyl chloride) (PVC) by melt blending. The mechanical properties of the PVC blends were investigated. The micro-morphology of the PVC blends was observed by scanning electron microscopy (SEM). The results indicated that the samples with the best impact strength could be obtained when the core-shell weight ratio of PB to PMMA is lower than 93:7, the mechanical properties correlated well with SEM morphologies, the addition of modifier with the ratio core to shell of 93:7 could reduce the domain size of the dispersed phase. Furthermore, the compatibility and properties of the blends were greatly enhanced and improved. The modifier particles could be well dispersed in the PVC matrix.     

XPS characterisation of core-shell silica-polymer composite particles synthesised by atom transfer radical polymerisation in aqueous media

Near-monodisperse, siloxane-functionalised silica particles are used as a colloidal substrate for the surface-initiated polymerisation of various hydrophilic methacrylates: oligo(ethylene glycol) methacrylate (OEGMA), 2-(N-morpholino)ethyl methacrylate (MEMA), and ammonium 2-sulfatoethyl methacrylate (SEM) by atom transfer radical polymerisation in aqueous media at room temperature. The bulk and surface compositions of the resulting composite particles were assessed using various techniques. Thermogravimetric analysis of the resulting silica-polymer composites indicated polymer loadings of 5.4-8.6%, depending on the nature, structure and target degree of polymerisation (D_p). Dynamic light scattering studies indicate increases in hydrodynamic diameter of 14-87 nm compared to the reference silica particles. FT-IR spectroscopy confirmed additional features characteristic of the carbonyl group and pendant end-chain functionalities of the methacrylic polymer chains. The elemental and chemical surface compositions of the initial silica particles and final polymer-grafted composite particles were extensively investigated by X-ray photoelectron spectroscopy (XPS). The composite particles had appreciably higher C/Si atomic ratios, compared to the original initiator-functionalised silica particles, and these ratios increased with increasing target D_p. In addition, close inspection revealed that the relative intensities of the various components of the peak-fitted C1s envelopes varied significantly, depending on the target degree of polymerisation and the chemical structure of the methacrylic monomer. Moreover, in the case of the MEMA and SEM polymerisations, new nitrogen (MEMA) and sulfur (SEM) XPS signals were detected. This XPS study confirmed the presence of a thin outer layer of grafted polymer chains surrounding the silica particles.     

Characterization of bimodal bigraft ABS

In the final product of a bimodal bigraft ABS, consisting of crosslinked polybutadiene particles (diameter 100 nm) with grafted and ungrafted poly (styrene-co-acrylonitrile) (=SAN) with an acrylonitrile (=AN) content of 28 weight %, crosslinked polybutadiene particles (diameter 300 nm) with grafted and ungrafted SAN with an AN content of 12 weight % and an added SAN with an AN content of 28 weight % the following parameters can be determined: degree of grafting of the small polybutadiene particles, degree of grafting of the large polybutadiene particles, acrylonitrile content of the grafted chains of the small polybutadiene particles, acrylonitrile content of the grafted chains of the large polybutadiene particles, grafting efficiency of the large particles, average particle diameter and particle diameter distribution of the small particles, average particle diameter and particle diameter distribution of the big particles, molar mass distribution of the ungrafted chains of the large particles, chemical distribution of the ungraftd chains of the large particles, molar mass distribution of the SAN resin added, chemical distribution of the SAN resin added.Preparative differential ultracentrifugation in acetone/-butyrolacrone (volume ratio 0.550.45), FTIR spectrometry and electron microscopy of the floating and sedimentating fraction yield the degree of grafting and AN content of the graft chains of the large particles and the degree of grafting and AN content of the graft chains of the small particles.Preparative differential centrifugation, FTIR spectrometry and electron microscopy of the fractions give nearly equivalent results. Fractional demixing with the demixing solvents ethylene carbonate/tetraline of the acetone-soluble part yields the SAN with 12 weight % AN in the upper-phase and the SAN with 28 weight % AN in the lower phase.Size exclusion chromatography (SEC) and high-performance precipitation liquid chromatography (HPPLC) of the fractions yield the molecular distribution and chemical distribution of the different SAN resins. SEC, coupled with turbidimetric titration of the acetone-soluble fractions withn-hexane as precipirant, indicates SAN resin with lower AN content in addition to the SAN resin with 28 weight % AN.Dedicated to Prof. Dr. Dr. h.c. mult. Karl Heinz Büchel on the occasion of his 60th birthday     

Multicomponent latex IPN materials. I. Morphology control

A series of novel structured latex particles with interpenetrating polymer network (IPN) cores and glassy SAN shells were developed in an attempt to investigate the feasibility of these polymers as both toughening and damping agents in thermoplastics. The IPN cores were composed of one impact part (polybutadiene based) and one damping part (acrylic based, with T_g around +10°C). The particle morphologies of these polymers were determined by TEM. The glass transitions and mechanical behavior of the polymers were characterized from DMS. The effect of different components on the final core/shell particle morphologies and mechanical properties was studied. The mechanical behavior of core/shell particles with IPN cores was also compared with that of separate core/shell and multilayered core/shell particles. In addition, normal core/shell synthesis (rubbery part first then the glassy part) and inverted core/shell synthesis (glassy part first then the rubbery part) were performed to provide another access for morphology control. It was found that the core/shell latex particles with poly(butyl acrylate) based copolymers are more miscible than poly(ethylhexyl methacrylate)-based copolymers. The high grafting efficiency of poly(butyl acrylate) plays an important role in governing phase miscibility. The latex particles synthesized by the inverted core/shell mode showed higher miscibility than the normal synthesized ones. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2193–2206, 1997     

Pickering emulsion polymerization of graphene oxide-stabilized styrene

Polystyrene (PS) particles were prepared via Pickering emulsion polymerization using graphene oxide (GO) as the stabilizer. The results show that pH is an important factor in the stability of Pickering emulsions. The effects of two different phase initiators, the water phase initiator potassium persulfate and the oil phase initiator azobisisobutyronitrile, on the morphology of PS particles in Pickering emulsion polymerization had been investigated in detail. Wrinkled particles were prepared using the water phase initiator, and spherical particles were prepared using the oil phase initiator. In addition, hexadecane was used as the auxiliary stabilizer in the polymerization, which narrowed the diameter distribution of the PS spheres, and the hollow PS spheres were fabricated. The size of the GO particles also influenced the final morphology of the particles. Nano-sized polymer particles were grafted onto the surface of micro-sized GO. Small GO particles were suitable for Pickering emulsion polymerization to prepare the composite particles. The thermogravimetric analysis of the prepared particles confirmed that they were PS/GO composite particles, which could have a wide range of potential applications, such as in catalysts, sensors, environmental remediation, and energy storage.     

Preparation of silica-PS composite particles and their application in PET

To investigate how the superfine particles disperse in the polymers, the paper presented the preparation of monodisperse silica particles by Stöber method, and then grafted by γ-methacrylic propyl trimethoxysilane (MPS) as a coupling agent. Using these modified particles, the more stable silica-PS superfine composite particles with higher monodispersity than these of previous reports are prepared and reported through dispersion polymerization (DP) method, whose morphology is investigated with transmission electron microscope (TEM). Their high stability is provided from the bonding of CC groups of MPS to the silanol groups on the surface of silica particles from FTIR.Using this DP process, the influence of different size grafted silica particles on the morphology, polystyrene (PS) encapsulation behavior and the distribution in these composite particles have been investigated. When the grafted silica size is in nanoscale or less than 54 nm, the spherical shape of neither silica particles nor their composite particles is regular, but they can homogeneously disperse in polystyrene. As the size (d_n) of grafted silica particles increase to submicrometer (or 100 nm < d_n < 1000 nm), their coefficient variance of size distribution (C_v) ranges from only 9.0% to 1.5%. These obtained particles are completely encapsulated by PS with more regular shape, and have their C_v below 7%. When the size of silica particles reaches 380 nm, their C_v obviously reduces to 2.5%, and specially, the number of grafted silica particles approaches to one in each of the composite particles. But, when the silica size reaches 602 nm, PS can hardly encapsulate grafted silica particles and free silica particles appear in reactive system.Furthermore, using the silica particles of 380 nm, a series of core-shell structured superfine composite particles of 640-1100 nm with C_v lower than 11% are obtained. Under the set conditions, the preparing factors on these composite particles using 380 nm grafted silica particles is discussed, and the best reaction condition for the well-dispersed and regular periphery silica-PS composite particles is optimized as, the additions amounts of PVP, styrene, AIBN, grafted SiO₂ and H₂O are 0.23 mmol L⁻¹, 0.60 mol L⁻¹, 6.10 mmol L⁻¹, 0.10 mol L⁻¹ and 5.50 mL, respectively. Under this case, the composite particles can be prepared with C_v below 8%.At last, these composite particles are mixed with poly(ethylene terephthalate) (PET) to investigate their nucleation effect. Results show that all different size particles can promote PET’s crystallization and enhance the crystallization rate, and PET’s crystallization temperature (T_mc) is obviously enhanced from 193 to 205 °C through differential scanning calorimetry (DSC). It is strongly suggested that different silica size level all play nucleation role in PET, and thus explain the nucleation effect of multiscale inorganic particles.     

表面引发接枝聚合法制备接枝微粒PHEMA/SiO2及其8-羟基喹啉功能化转变研究

通过用表面引发接枝聚合和高分子反应制备8-羟基喹啉型复合螯合微粒.首先使用γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行表面改性,制得改性微粒AMPS-SiO2;使改性微粒AMPS-SiO2表面的氨基与溶液中的过硫酸盐构成氧化-还原引发体系,实施了甲基丙烯酸羟乙酯(HEMA)在硅胶微粒表面的高效引发接枝聚合,制得了接枝微粒PHEMA/SiO2.又以5-氯甲基-8-羟基喹啉(CHQ)为试剂,使接枝的PHEMA发生大分子反应,实现了接枝微粒PHEMA/SiO2的8-羟基喹啉功能化转变,制得了复合微粒HQ-PHEMA/SiO2.采用多种手段对两种微粒进行了表征,重点研究了氨基-过硫酸盐表面引发接枝体系的接枝聚合机理,并研究了CHQ与接枝PHEMA的醇羟基之间取代反应的机理,还初步考察了功能微粒HQ-PHEMA/SiO2对重金属离子的螯合吸附性能.研究结果表明,氨基-过硫酸盐表面引发接枝聚合体系具有很高的引发活性,在室温(30℃)即可制得高接枝密度(40 g/100g)的接枝微粒PHEMA/SiO2;CHQ与接枝PHEMA的醇羟基之间的取代反应遵循SN1的反应历程,使用强极性溶剂有利于反应的进行.微粒HQ-PHEMA/SiO2对重金属离子呈现很强的螯合吸附能力,是一种功能复合微粒.     

Synthesis of statistical networks from liquid polybutadiene—IV. Influence of crosslinking agent

The synthesis of statistical macromolecular networks is achieved from liquid polybutadiene as precursor polymer with difunctional crosslinking agents bearing two hydrogenosilane groups. The properties of the network (extractable polymer, equilibrium swelling degree, uniaxial compression modulus) are strongly influenced by the structure of the crosslinks. Aromatic type structures are best suited to obtain high modulus networks which can be used for applications in the field of composite materials.     

Size‐selective purification of hepatitis B virus‐like particle in flow‐through chromatography: Types of ion exchange adsorbent and grafted polymer architecture

Hepatitis B virus‐like particles expressed in Escherichia coli were purified using anion exchange adsorbents grafted with polymer poly(oligo(ethylene glycol) methacrylate) in flow‐through chromatography mode. The virus‐like particles were selectively excluded, while the relatively smaller sized host cell proteins were absorbed. The exclusion of virus‐like particles was governed by the accessibility of binding sites (the size of adsorbents and the charge of grafted dextran chains) as well as the architecture (branch‐chain length) of the grafted polymer. The branch‐chain length of grafted polymer was altered by changing the type of monomers used. The larger adsorbent (90 μm) had an approximately twofold increase in the flow‐through recovery, as compared to the smaller adsorbent (30 μm). Generally, polymer‐grafted adsorbents improved the exclusion of the virus‐like particles. Overall, the middle branch‐chain length polymer grafted on larger adsorbent showed optimal performance at 92% flow‐through recovery with a purification factor of 1.53. A comparative study between the adsorbent with dextran grafts and the polymer‐grafted adsorbent showed that a better exclusion of virus‐like particles was achieved with the absorbent grafted with inert polymer. The grafted polymer was also shown to reduce strong interaction between binding sites and virus‐like particles, which preserved the particles’ structure.     

聚丁二烯－b－甲基丙烯酸甲酯共聚物的聚集态研究

聚丁二烯－ｂ－甲基丙烯酸甲酯共聚物的聚集态研究周庆业,张邦华,宋谋道,何炳林（南开大学高分子化学研究所,天津,３０００７１）关键词共聚物,相分离,聚集态结构嵌段共聚物按其组成、合成及成型条件的不同可形成丰富的相结构［１］,其动态力学性能,如在损耗模量...     

Efficient synthesis of asymmetric particles by sol-gel process

This paper presents a novel and facile method of synthesizing polymer/silica particles with controlled asymmetric morphologies. Our approach is based on the sol–gel process in which cross-linked polystyrene particles (CPS) are adopted as templates and 3-mercaptopropyltriethoxysilane is used as a single silica source. The reaction process causes silane oligomer to preferentially grow on the local surface of CPS, giving rise to polystyrene/thiol-functionalized silica composite particles with a tunable shape. It is found that the morphologies of particles can be easily tailored by changing the ratio of ethanol/water in the reaction medium. In addition, the amount of cross-linker used during the polymerization also plays a key role in the formation of various complex-shaped particles. Controlled geometries of these organic/inorganic composite particles will allow a broad range of potential applications, such as photonic crystals, Pickering emulsifier, sensors, and so on.     

Thermodynamic analysis of the morphology of monomer-adsorbed,cross-linked polymer particles prepared by the dynamic swelling method and seeded polymerization

Thermodynamic simulation of the morphology of monomer-adsorbed, cross-linked polymer particles prepared by the dynamic swelling method which the authors proposed was conducted to clarify its thermodynamic stability from the viewpoint of the total interfacial free energy. By comparing it with experimental results reported in previous articles, it was found that the morphology was controlled thermodynamically. Snowman-shaped composite polymer particles having different morphologies were prepared by seeded polymerization of the monomer-adsorbed, cross-linked polymer particles, in which the polymer particles had different cross-linking densities.     

聚合物纳米微粒静电组装行为及其表征

使用2,2′-偶氮二异丁基脒二盐酸盐自由基引发剂,改变甲基丙烯酰氧乙基十六烷基二甲基溴化铵阳离子功能单体的量与苯乙烯进行乳液聚合获得不同粒径的阳离子乳胶粒,使用十二烷基硫酸钠为乳化剂和过硫酸钾为引发剂制备阴离子聚合物乳胶粒.采用基于静电相互作用的异凝聚法将以上2种带有相反电荷的乳胶粒组装,获得了表面粗糙程度不同的复合微粒.对异凝聚过程中复合液透光率和微粒大小及分布进行跟踪测试,并用透射电子显微镜表征了阳离子微粒、阴离子微粒以及复合微粒的形态和大小.结果表明,在一定范围内可以通过控制阴离子乳胶粒与阳离子乳胶粒的复合比例改变单个复合微粒表面阳离子小微粒的数目.     

Fabrication of zinc oxide/poly(styrene) grafted nanocomposite latex and its dispersion

Zinc oxide nanoparticles, with an average size of about 40 nm, were encapsulated by polystyrene using in situ emulsion polymerization in the presence of 3-methacryloxypropyltrimethoxysilane (MPTMS) as a coupling agent and polyoxyethylene nonylphenyl ether (OP-10) as a surfactant. Polymerization mechanism of nanocomposite latex was discussed. Transmission electron microscopy (TEM) proved the presence of ZnO nanoparticle appeared to be monodisperse in nanosize in polymer composite particles. ZnO/PS nanocomposites were characterized by Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results of FT-IR and XPS revealed that the surface of ZnO particle was successfully grafted by PS through the link of the coupling agent between ZnO and polymer. TGA and DSC results indicated an enhancement of thermal stability of composite materials compared with the pure polymer. SEM (scanning electron microscope) images showed a perfect dispersion of the ZnO particles in latex film. In addition, UV-visible absorption measurements demonstrated that the ZnO/PS composite coatings display a perfect performance of absorbing UV light.     

Controllable synthesis of CuS-P(AM-co-MAA) composite microspheres with patterned surface structures

Copper sulfide-poly(acrylamide-co-methacrylic acid) (CuS-P(AM-co-MAA)) composite microspheres with patterned surface structures have been synthesized in a controllable manner by means of the polymer microgel template method. The formation of CuS particles can be regulated by controlling the decomposition of thioacetamide (TAA) in acidic solution. Compared with the microgel template, the surface morphologies of the composite microspheres are characterized by compact and creased textures. The surface morphology of the composite microspheres has been found to be mainly influenced by the amount of copper sulfide precipitated and hence by the rate of H(2)S gas generation. This study might provide a potential route for controlling the synthesis of various metal sulfide-polymer composites with patterned surface structures.     

Preparation of Iminoacetic Acid-type Composite Chelating Material IAA-PEI/SiO2 and Preliminary Studies on Chelating Adsorption Property towards Heavy Metal Ions

Polyamine polyethyleneimine (PEI) was first grafted on the surfaces of micro-sized silica gel particles in the manner of the coupling graft (the manner of “grafting to”), forming the grafting particles PEI/SiO₂. Subsequently, via a polymer reaction, the nucleophilic substitution reaction between the primary and secondary amino groups of the grafted PEI macromolecule and chloroactic acid (CAA), iminoacetic acid groups were bonded onto the grafted PEI chains, and an iminoacetic acid (IAA)-type composite chelating material, IAA-PEI/SiO₂, was formed. In this work, the preparation process of IAA-PEI/SiO₂ particles was mainly researched, and the effects of the main factors on the polymer reaction, i.e., the nucleophilic substitution reaction, were examined emphatically. The adsorption behavior of IAA-PEI/SiO₂ particles towards several kinds of heavy metal ions was preliminarily evaluated. The experiments results show that it is feasible to introduce IAA groups onto PEI/SiO₂ particles via the substitution reaction between CAA and the amino groups of the grafted PEI. The reaction rate is affected greatly by the feed ratio of the amino group of PEI to CAA, so the substitution reaction between CAA and the amino groups of the grafted PEI is a bimolecular nucleophilic substitution reaction (S_N2). The reaction temperature and the used amount of acid-acceptor NaHCO₃ affect the bonding rate of IAA groups greatly. The fitting temperature was 60°C, and 1:1 of the molar ratio of NaHCO₃ to CAA was an appropriate amount of acid-acceptor NaHCO₃. Under the above optimal reaction conditions and with 3:1 molar ratio of amino group of PEI to CAA, 72% of the IAA group bonding rate (it is based on the hydrogen atoms in the primary and secondary amino groups of the grafted PEI) in 8 h can be reached. The composite chelating material IAA-PEI/SiO₂ possesses a strong chelating adsorption ability for heavy metal ions because of the increase of the ligands and formation of stable five-membered chelate rings.