Synthesis of natural rubber-g-maleic anhydride and its use as a compatibilizer in natural rubber/short nylon fiber composites

Natural rubber grafted maleic anhydride (NR-g-MAH) was synthesized by mixing maleic anhydride (MAH) and natural rubber (NR) in solid state in a torque rheometer using dicumyl peroxide (DCP) as initiator. Then the self-prepared NR-g-MAH was used as a compatibilizer in the natural rubber/short nylon fiber composites. Both the functionalization of NR with MAH and the reaction between the modified rubber and the nylon fiber were confirmed by Fourier transform infrared spectroscopy (FTIR). Composites with different nylon short fiber loadings (0, 5, 10, 15 and 20 phr) were compounded on a two-roll mill, and the effects of the NR-g-MAH on the tensile and thermal properties, fiber-rubber interaction, as well as the morphology of the natural rubber/short nylon fiber composites were investigated. At equal fiber loading, the NR-g-MAH compatibilized NR/short nylon fiber composites showed improved tensile properties, especially the tensile modulus at 100% strain which was about 1.5 times that of the corresponding un-compatibilized ones. The equilibrium swelling tests proved that the incorporation of NR-g-MAH increased the interaction between the nylon fibers and the NR matrix. The crosslink density measured with NMR techniques showed that the NR-g-MAH compatiblized composites had lower total crosslink density. The glass transition temperatures of the compatibilized composites were about 1 K higher than that of the corresponding un-compabilized ones. Morphology analysis of the NR/short nylon fiber composites confirmed NR-g-MAH improved interfacial bonding between the NR matrix and the nylon fibers. All these results signified that the NR-g-MAH could act as a good compatilizer of NR/short nylon fiber composites and had a potential for wide use considering its easy to be prepared and compounded with the composites.     

Heat-resistant and strong glassy network copolymers of aromatic ethers (Rolivsans) containing terminal vinyl and methacrylate groups with maleic anhydride

Three-dimensional radical copolymerization of multicomponent systems consisting of vinylaromatic ethers and methacrylates of secondary alkylaromatic alcohols (diols) with maleic anhydride was studied. Heat-resistant and strong polymeric materials and composites were prepared from copolymers of Rolivsans with maleic anhydride.     

Covalent immobilization of chitosan on surfaces with anchoring layers of poly(glycidyl methacrylate) and maleic anhydride copolymers

The method for producing chitosan coatings on solid surfaces with anchoring layers of poly(glycidyl methacrylate) and maleic anhydride copolymers has been proposed. It is shown that, owing to a high reactivity of epoxy and anhydride groups, the efficiency of immobilization and the stability of the coatings are considerably higher than those prepared by the conventional method of chitosan grafting onto the surface modified by poly(acrylic acid). The properties of chitosan coatings are examined via atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, and electrokinetic measurements. Depending on the anchoring layer used, the total thickness of the coatings is 6–16 nm with an rms roughness less than 1.2 nm, while the isoelectric points of the surfaces modified with chitosan are located in the pH range 5–6.     

Synthesis and characterization of tin telluride inorganic/organic composite materials with nanoscale periodicity through solution-phase self-assembly: a new class of composite materials based on Zintl cluster self-oligomerization

In this work, we demonstrate the synthesis of semiconducting tin telluride inorganic/organic composite materials with nanoscale periodicity prepared using solution phase self-assembly. Oligomerization of anionic SnTe ₄ ^4? clusters by halogen-mediated tellurium elimination in the presence of surfactant leads to the formation of a meosotructured composite. The composites initially forms as a mixture of mesophases, usually some combination of a layered phase and a phase based on cylindrical building blocks. Post synthetic treatment leads to a solid-state structural change which converts the composites to a single mesophase architecture with a hexagonal honeycomb (p6mm) morphology on the nanometer length scale. A by product of this reaction, however, is bulk tellurium. Changes in the electronic structure of the materials during synthesis and solid-state restructuring are probed using electron spin resonance (ESR) spectroscopy.     

Thermal and viscoelastic properties of novel epoxy-dicyclopentadiene-terminated polyesters-styrene copolymers

This article presents the studies on the thermal and viscoelastic properties of novel epoxy-dicyclopentadiene-terminated polyesters-styrene copolymers. The novel materials were prepared during a three step process including the addition reaction of maleic acid to norbonenyl double bond of dicyclopentadiene; polycondensation of acidic ester of dicyclopentadiene, cyclohex-4-ene-dicarboxylic anhydride, maleic anhydride, and suitable glycol: ethylene, diethylene, or triethylene glycol; and the epoxidation process of prepared polyesters. It allowed obtaining novel epoxy-dicyclopentadiene-terminated polyesters which were successfully used as a component of different styrene content (10?C80?mass%) copolymers. The influence of the structures of polyester and styrene content on the cross-linking density (v _e), tg?? _max, tg?? _max height, storage modulus (E?? _20?°C), FWHM values as well as the thermal stability of copolymers was evaluated by TG, DSC, and DMA analyses and discussed.     

Microwave Assisted Synthesis of Diosgenin Esters of Maleic and Itaconic Acids

Diosgenin monomaleate and diosgenin monoitaconate were prepared by the esterification of diosgenin with maleic and itaconic anhydride, respectively, in toluene using p-toluenesulphonic acid as catalyst. A domestic microwave oven was modified and used for the synthesis of both products. The reaction time for consuming all the diosgenin according to thin-layer chromatography (TLC) was reduced by around 90% in the synthesis of monomaleate of diosgenin as well as in the synthesis of monoitaconate of diosgenin in comparison with conventional heating, whereas the monomaleate of diosgenin yield increased from 43 to 80–85% and the monoitaconate of diosgenin yield from 34 to 95% under the same experimental conditions. It was easier to purify the diosgenin monoitaconate than the diosgenin monomaleate. Both products were characterized by NMR and FTIR spectroscopy.     

A Comparative Study of Modified and Unmodified High-Density Polyethylene/Borassus Fiber Composites

In this work, composite samples were prepared using Borassus fibers and a high-density polyethylene matrix. Alternatively, a chemically modified matrix (maleic anhydride grafted HDPE) was also used to improve fiber-matrix compatibility. The effect of fiber loading on the mechanical properties was investigated. Borassus fiber/modified HDPE composites exhibited improved mechanical performance as compared to pure HDPE composites. SEM studies on the fractured specimens of unmodified HDPE fiber composites reveal the poor fiber-matrix interaction, whereas the interaction is strong with enhanced mechanical properties for modified HDPE fiber composites. This is due to an improvement of the chemical bonding between the modified HDPE matrix and the Borassus fiber as also supported by Fourier transform infrared spectroscopy results. Thermal stability was also found to be enhanced slightly for modified HDPE composites.     

Kapok/cotton fabric–polypropylene composites

Kapok/cotton fabric has been used as reinforcement for conventional polypropylene and maleic anhydride grafted polypropylene resins. Treating the reinforcement with acetic anhydride and sodium hydroxide has modified the fabric (fibres). Thermal and mechanical properties of the composites were investigated. Results show that fibre modification gives a significant improvement to the thermal properties of the plant fibres, whereas tests on the mechanical properties of the composites showed poor tensile strength. Mercerisation and weathering were found to impart toughness to the materials, with acetylation showing slightly less rigidity compared to other treatments on either the fibre or composites. The modified polypropylene improved the tensile modulus and had the least toughness of the kapok/cotton reinforced composites. MAiPP reinforced with the plant fibres gave better flexural strength and the same flexural modulus at lower fibre content compared with glass fibre reinforced MAiPP.     

Preparation of poly(glycidylmethacrylate‐divinylbenzene) weak acid cation exchange stationary phases with succinic anhydride,phthalic anhydride,and maleic anhydride for ion chromatography

In this work, poly(glycidylmethacrylate‐divinylbenzene) microspheres were prepared and applied for the preparation of weak acid cation exchange stationary phases. Succinic anhydride, phthalic anhydride, and maleic anhydride were selected as carboxylation reagents to prepare three weak acid cation exchangers by direct chemical derivatization reaction without solvent or catalyst. The diameters and dispersity of the microspheres were characterized by scanning electron microscopy; the amount of accessible epoxy groups and mechanical stability were also measured. The weak acid cation exchangers were characterized by Fourier transform infrared spectroscopy; the content of carboxyl groups was measured by traditional acid base titration method. The chromatographic properties were characterized and compared by separating alkali, alkaline earth metal ions and ammonium and polar amines. The separation properties enhanced in the order of succinic anhydride, phthalic anhydride, and maleic anhydride modified poly(glycidylmethacrylate‐divinylbenzene) cation exchangers.     

Preparation,characterization and application of maleic anhydride-modified polylactic acid macromonomer based on direct melt polymerization

A one-pot two-step method based on direct melt polymerization (DMP) for the synthesis of polylactic acid (PLA) macromonomer and its further functionalized application has been developed. The first stage of the reaction is a copolycondensation of lactic acid (LA) and maleic anhydride (MAH) to obtain the macromolecule poly(lactic acid-co-maleic anhydride) (PLAM) with reactive double bonds, and the second stage is a radical copolymerization of different acrylates with PLAM to afford the modified PLA functional materials. The influences of the acrylates have been investigated. The results show that the species with substituted methyl groups in acrylate can polymerize relatively stable. On the other hand, the more carbon atoms in the ester segment of acrylate, the higher intrinsic viscosity [η] and terminal decomposition temperature for the acrylate-modified PLAMs. Among six kinds of acrylates used as the third monomer, such as acrylic acid (AA), methyl acrylate (MA), butyl acrylate (BA), methacrylic acid (MAA), methyl methacrylate (MMA), and butyl methacrylate (BMA), the BMA-modified PLAM has the biggest [η] (0.7566 dL/g) and the terminal decomposition temperature (418 °C) for there are more carbon atoms in BMA. Due to excellent reactivity of the intermediate PLAM, the final modified product can have the anticipated properties for the PLA material by the controllable regulating as different purposes. Thus, this strategy as a green and simple method provides well application prospect for PLA materials in industrial plastics, biomedicine etc.     

聚(苯乙烯-马来酸酐)/Fe3O4纳米杂化材料的制备与表征

采用2,2,6,6-四甲基-1-哌啶氧化物(TEMPO)的溴盐对化学共沉淀法制备的Fe3O4纳米粒子进行表面修饰,以该粒子为过氧引发剂,苯乙烯(St)、马来酸酐(MA)为单体,采用"活性"/可控自由基聚合技术在粒子表面原位引发聚合,制备了聚(苯乙烯-马来酸酐)/Fe3O4纳米杂化材料,并对纳米Fe3O4及杂化材料进行了FT-IR、XRD、TGA、TEM和GPC表征。结果表明,所制备的纳米杂化材料的平均粒径约为70 nm,磁性粒子表面的聚合物分子链随着聚合时间的增长而增长。振动样品磁强计测试结果显示,在室温、外加磁场下,该纳米杂化材料呈现超顺磁性,饱和磁化强度随着包覆聚合物量的增加而降低。     

Chitosan aerogel containing silver nanoparticles: From metal-chitosan powder to porous material

The work presents a synthetic approach that combines methods of metal vapor synthesis (MVS), gelation and supercritical drying in order to obtain chitosan aerogels containing silver nanoparticles. On the first stage, two types of silver organosols were prepared via the eco-sustainable MVS method. Then the prepared silver organosols were used to modify chitosan powders for producing metal-chitosan powder composites. Gelation of the powder composites was performed in oxalic acid at elevated temperatures. Supercritical drying of the gels was implemented in order to preserve the formed porous structures. Thus, the chitosan powders modified with MVS-produced silver nanoparticles were used to prepare metal-chitosan aerogels. Characterization of the structure and the morphology of both powder and aerogel silver-chitosan composites was conducted by means of low temperature nitrogen adsorption, X-ray photoelectron spectroscopy, X-ray powder diffraction, small-angle X-ray scattering, SEM and TEM. Changes in the structure and morphology of silver nanoparticles between powder and aerogel composites were analyzed.     

Evolution of a Strategy for the Total Synthesis of (+)-Cornexistin

Herein is given a full account of the evolution of the first total synthesis of (+)-cornexistin. Initial efforts were based on masking the reactive maleic anhydride moiety as a 3,4-substituted furan and on forming the nine-membered carbocycle in an intramolecular Conia-ene or Nozaki–Hiyama–Kishi (NHK) reaction. Those strategies suffered from low yields and were jeopardized by a late-stage installation of the Z-alkene, as well as the stereocenters along the eastern periphery. These issues were addressed by employing a chiral-pool strategy that involved construction of the crucial stereocenters at C2, C3 and C8 at an early stage with installation of the maleic anhydride as late as possible. The successful approach featured an intermolecular NHK coupling to install the Z-alkene, a syn-Evans-aldol reaction to forge the stereocenters along the eastern periphery, an intramolecular allylic alkylation to close the nine-membered carbocycle, and a challenging stepwise hydrolysis of a β-keto nitrile to furnish the maleic anhydride.     

Comparative analysis of nanocomposites based on polypropylene and different montmorillonites

Nanocomposites of polypropylene (PP) were prepared by melt mixing using maleic anhydride modified polypropylene (PPg) and different organophilic montmorillonites (OMMT). The selected organo-modified clays differ in their initial particle size, amount and type of surfactant and/or their cation-exchange capacity. All composites have 80, 15 and 5 wt% of PP, PPg and OMMT, respectively. The materials were characterized using TGA, XRD, SEM and rotational rheometry. Cloisite 15A, Cloisite 93A, Nanomer I44 and a bentonite modified with octadecylammonium (B18) display intercalation and exfoliation after mixing and annealing and produce nanocomposites with different degrees of ‘solid-like’ rheological behavior. The composites based in Cloisite 15A and Nanomer I44, which use the same intercalant, show very similar phase structure and rheological response, regardless of the origin and initial characteristics of the clays. These nanocomposites are the most affected by the thermal history during rheological characterization in the molten state. On the other hand, Cloisite 10A and Cloisite 30B display collapse of the silicate layers after compounding with no evidence of exfoliation.     

New heterocycles of 2,3‐diaryl‐substituted maleic hydrazides

2,3‐Diaryl‐substituted maleic anhydrides were prepared by a modified one‐pot synthesis of Perkin condensation using mixed sodium salts of arylglyoxylic acid and arylacetic acid with acetic anhydride in 1,4‐dioxane. The treatment of these anhydrides with ammonium bicarbonate, or methanolic hydrazine, offered the corresponding 2,3‐diaryl‐substituted maleimides and maleic hydrazides (4,5‐diaryl‐substituted 1,2‐dihydropyridazine‐3,6‐dione), respectively. Evidence obtained from NMR, UV, and mass spectra suggest that 2,3‐diaryl‐substituted maleic hydrazides do not exhibit monolactim forms. Ring contraction of the diaryl‐substituted maleic hydrazide by nitrosation led to the formation of the corresponding maleimide. Interconversion between the corresponding maleic hydrazide and maleimide was observed following equilibrium reaction. Our experiment proposes that the chemistry of 2,3‐diaryl‐substituted maleic hydrazides rarely involves the function of ethylene moiety and resembles that of succinic hydrazine. J. Heterocyclic Chem.,(2011).     

Practical synthesis of four different pseudoenantiomeric organocatalysts with both cis- and trans-substituted 1,2-cis-cyclohexanediamine structures from a common intermediate

A new and convenient approach has been deviced for the practical synthesis of structurally robust, four different pseudoenantiomeric amino Tf-amido organocatalysts with the unique cis- and trans-substituted 1,2-cis-cyclohexanediamine structures. These pseudoenantiomeric organocatalysts are easily prepared by the Diels-Alder strategy of 2-phenyl-1,3-butadiene and maleic anhydride, and their chemical behavior was investigated by their application to asymmetric aldol synthesis for the practical synthesis of both enantiomeric aldols.     

Poly(vinyl chloride) stabilization with organo-tin compounds: Part VII—Dibutyl tin maleate: Model compound studies

The reaction between dibutyl tin maleate or dibutyl tin bisbutylmaleate and chlorohexene as a model compound for allylic chloride in PVC was studied at 80°C in dichlorobutane solution. From kinetic studies by gas chromatographic analysis of the reaction medium, and also spectroscopic data (infra-red and ¹H NMR) it may be concluded that the main reaction is the substitution reaction which produces mono- and dihexenyl esters, as well as mixed diesters of maleic acid. The elimination reaction plays a minor rôle. Both activities are related to their Lewis acidities. The Diels-Alder condensation between maleates and hexadiene is not observed as a side reaction in these conditions; the main side reaction is the decomposition of monoesters of maleic acid (which is produced by the elimination reaction after one or two steps) into an alcohol and maleic anhydride—a reaction which can be catalysed by organo-tin chlorides. A Diels-Alder reaction between maleic anhydride and hexadiene takes place. The alcohol produced in the side reaction mentioned above may take part in a transesterification reaction with the organo-tin maleate and that reaction probably provides the best explanation of the earlier observation of Frye et al.,¹ according to which there is at least temporary retention of reactivity of tin labelled organo-tin maleate by PVC.     

Synthesis of mono and difunctional oligoisobutylenes—III. Modification of α-chlorooligoisobutylene by reaction with maleic anhydride

Reaction of monofunctional oligoisobutylene with maleic anhydride is described. In a preliminary study, thermal dehydrochlorination of α-chlorooligoisobutylene is examined; the double bond of the resulting olefin can be endo or exo. Ene reaction of maleic anhdride with this oligomer is first studied on a model, 2,4,4-trimethyl-1-pentene; resulting mixture is completely analysed by ¹³C- and ¹H-NMR spectroscopy: two isomeric oligomer anhydrides are formed. Ene synthesis is also carried out on α-(2-methyl-2-propenyl)oligoisobutylene; only exo bonds are able to react; the functionality of the resulting oligomeric anhydride mixture is 0.92. In the presence of a catalyst (dichloromaleic anhydride) disubstitution can take place, because the double bond formed in the first reaction is able to react a second time with maleic anhydride.     

Mechanism of phthalic anhydride formation in the oxidation of n-pentane on a vanadium-phosphorus oxide catalyst

The reaction paths of product formation in the partial oxidation of n-pentane on vanadium-phosphorus oxide (VPO) and VPO-Bi catalysts are considered. The condensed products of n-pentane oxidation were analyzed by chromatography-mass spectrometry, and the presence of C₄ rather than C₅ unsaturated hydrocarbons was detected. It was found that the concentration of phthalic anhydride in the products increased upon the addition of C₄ olefins and butadiene to the n-pentane-air reaction mixture. With the use of a system with two in-series reactors, it was found that the addition of butadiene to a flow of n-butane oxidation products (maleic anhydride, CO, and CO₂) resulted in the formation of phthalic anhydride. The oxidation of 1-butanol was studied, and butene and butadiene were found to be the primary products of reaction; at a higher temperature, maleic anhydride and then phthalic anhydride were formed. The experimental results supported the reaction scheme according to which the activation of n-pentane occurred with the elimination of a methyl group and the formation of C₄ unsaturated hydrocarbons. The oxidation of these latter led to the formation of maleic anhydride. The Diels-Alder reaction between maleic anhydride and C₄ unsaturated hydrocarbons is the main path of phthalic anhydride formation.     

Conductive Composites Based on Metallocene Isotactic Poly(propylene): Preparation and Properties

Summary: The research deals with the preparation and the further comprehensive characterization of metallocene polypropylene-based composite materials by incorporation of carbon black nanoparticles. Composites containing up to 10 wt% of carbon black were prepared by direct melt mixing in a single screw extruder Brabender Extrusiograph type 30/25D with attached static mixer at melt temperature of 200 °C and a screw speed of 30 rpm, according to a two-step process. Some composites were treated with 3 wt% maleic anhydride grafted polypropylene (MAH-PP). The rheological behaviour of the miPP nanocomposites was determined by cone/plate rheological measurements at 180 °C. The composites were characterized by SEM for morphological details and uniaxial stress-strain measurements for determining the mechanical parameters. Electric conductivity of injection molded plates from these composites was investigated. The different miPPs studied are ranked in an ascending order according to their increasing molecular weight concerning the magnitude of their rheological parameters. The maleic anhydride compatibilizer leads to lower viscosity values even at high shear gradients and to better homogenization of the nanofiller in the polymer matrix. The processing conditions, carbon black concentration and viscosity of the virgin polymer have an impact on the final conductivity of the miPP/carbon black composites.