Mechanistic Insights into Selectivity Control for Heterogeneous Olefin Oxidation: Styrene Oxidation on Au(111)

We demonstrate that intermolecular interactions, controlled by both oxygen and styrene coverage, alter reaction selectivity for styrene oxidation on oxygen‐covered Au(111). Several partial oxidation products are formed—styrene oxide, acetophenone, benzoic acid, benzeneacetic acid, and phenylketene—in competition with combustion. The maximum ratio of the yields of styrene oxide to the total CO₂ produced is obtained for the maximum styrene coverage for the first two layers (0.28 ML) adsorbed on Au(111) precovered with 0.2 ML of O. Furthermore, our reactivity and infrared studies support a mechanism whereby styrene oxidation proceeds via two oxametallacycle intermediates which, under oxygen‐lean conditions, lead to the formation of styrene oxide, acetophenone, and phenylketene. Benzoate, identified on the basis of infrared reflection absorption spectroscopy, is converted into benzoic acid during temperature‐programmed reaction. These results demonstrate the ability to tune the epoxidation selectivity using reactant coverages and provide important mechanistic insight into styrene oxidation reactions.     

Complexation of chitosan with maleic acid copolymers

The complexation of chitosan with alternating copolymers of maleic acid with N-vinylpyrrolidone, ethylene, or styrene is studied. It is found that the process is of a cooperative character and that the binding constants and the Hill parameters are dependent on the nature of a nonionogenic comonomer maleic acid in the synthetic polyanion and on the conditions of complexation. The data of atomic force microscopy and turbidimetric titration confirm the effect of temperature on the conformation of interacting macromolecules and the size of macromolecular aggregates. It is shown that the composition and yield of insoluble interpolyelectrolyte complexes at constant pH are determined by the reactant ratio, the temperature, and the initial concentration of polyelectrolytes.     

Colloidal Systems on the Basis of Novel Reactive Surfmers

Summary: New anion surfmers of the family of maleic acid asymmetrical esters have been synthesized. Some of its features in the process of emulsion copolymerization with styrene have been studied. The characteristics of covering, obtained on the basis of such latexes of new generation have been investigated as well.     

Contribution to the study of the mechanism of curing of unsaturated polyester resins

The mechanism of copolymerization of monomethyl and dimethyl maleates and fumarates with styrene was studied by analysis of the conformation of the acid units of the resulting copolymers. The absorption bands for C?O stretching and OH stretching in the spectra of the copolymers are fully identical. They are quite different from the spectra of the copolymers obtained from maleic anhydride and styrene that are subsequently treated with absolute methanol to give the monoester which is then esterified with diazomethane to give the diester. The acid units of the copolymers derived from maleic anhydride exist in a gauche configuration; copolymers derived from fumaric units exist in a trans conformation. The identity of copolymers derived from maleic units with those derived from fumaric units but not with those derived from maleic anhydride indicates that the first step in the copolymerization of the maleic units is an isomerization to fumaric units, which are actually the genuine comonomers.     

Amphiphilic maleic acid-containing alternating copolymers—1. Dissociation behavior and compositions

The dissociation of the two adjacent carboxylic acids in maleic acid-containing copolymers is expected to differ from those of poly(acrylic acid) and poly(methacrylic acid) where the acids are separated by two carbons on the backbone. In this work, we have employed potentiometric titration and NMR spectroscopy to characterize the dissociation behavior and chemical compositions of several water-soluble maleic acid-containing copolymers. A distinct two-step process corresponding to the dissociation of the two adjacent carboxylic acids is observed in aqueous CaCl₂ (0.02 N) solution for copolymers of maleic acid and isobutylene, diisobutylene, and styrene. Such a two-step ionization process is less recognizable, however, for the copolymers of maleic acid and linear alkenes ranging from n-hexene to n-octadecene. Nevertheless, the compositions of all copolymers, including the extent of neutralization and the ratio of the comonomer moieties, are estimated from the titration curves. The chemical composition derived from potentiometry and NMR spectroscopy for all copolymers are approximately 1 : 1 (maleic acid : comonomer). With the exception of the hydrophobically modified copolymer of isobutylene-maleic acid, no obvious conformational transition was observed over the whole range of ionization for these hydrophobic maleic acid-containing copolymers. This is related to the aggregated state of these copolymers in aqueous media. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3571–3583, 2004     

苯乙烯和马来酸酐包夹硅胶弱阳离子色谱柱的制备及其应用

用马来酸酐包夹硅基制备出一种新型弱阳离子色谱柱填料,它具有良好的色谱性能,可同时分离一价、二价金属阳离子。论述了固定相的制备条件。采用所制备的固定相对热电厂锅炉水样中的阳离子进行了测定。     

Processing of Acetophenon Bottoms from Distillation of Styrene with Maleic Acid

The kinetic features of dehydration of maleic acid during preparation of a copolymer based on the styrene distillation bottoms from joint production of styrene and propylene oxide were studied. The potential application fields for the copolymer synthesized were analyzed.     

Syntheses and reactions of functional polymers. XCIII. Syntheses of polymers containing the N-(4-hydroxy-3-nitrophenyl)succinimide structure in the chain and the use of these activated polymer esters of N-blocked amino acids or peptides

Polymers containing the N-(4-hydroxy-3-nitrophenyl)succinimide residue were designed in order to achieve acyl activation of a reacting carboxylic acid in the solid phase. These polymers were prepared through the following three routes: (a) styrene was allowed to copolymerize with N-(4-hydroxy-3-nitrophenyl)- or N-(4-acetoxy-3-nitrophenyl)maleimide, (b) styrene was copolymerized with N-(4-acetoxyphenyl)maleimide in the presence of divinylbenzene (DVB), and the copolymer obtained was hydrolyzed and nitrated, (c) a copolymer of maleic anhydride and styrene was reacted with p-aminophenol, followed by nitration. The polymers prepared by routes b and c were converted to the activated polymer esters of N-blocked amino acids and peptides by using dicyclohexylcarbodiimide (DCC). The acylated polymers thus obtained were treated with amino acid esters and found to give peptides quantitatively without racemization.     

Application of polymerized bottoms from styrene rectification to producing polybutadiene

Polymeric materials are obtained by high-temperature copolymerization of bottoms from styrene rectification with maleic acid, which can be used for preparation of antioxidant solutions for further adding at the polybutadiene processing before passing the latter to the step of isolation.     

Interaction of polyanions with electroneutral liposomes in a slightly acidic medium

In this study, the interaction between poly(styrene sulfonic acid), polyacrylic acid, poly(meth-acrylic acid), poly(L-glutamic acid), poly(vinyl sulfate), and ternary copolymer of styrene with maleic anhydride and methacrylic acid (3: 2: 1), as well as DNA with lipid vesicles composed of zwitterion (electroneutral) lipid phosphatidylcholine, has been investigated. The methods of centrifuge ultrafiltration and dynamic light scattering reveal that, at pH 4.2, all polyacids under study are effectively adsorbed on the phospholipid membrane. The polymer-membrane complex is stabilized by hydrogen bonds and hydrophobic interactions in addition to electrostatic bonds. Even though, to a greater or lesser extent, all polyacids are capable of undergoing adsorption on the membrane in a slightly acidic medium, their effect on the membrane permeability is substantially different and is correlated with the ability of a polymer to form multiple interactions with phospholipid molecules. Poly(acrylic acid), poly(methacrylic acid), poly(styrene sulfonic acid), and the ternary copolymer of styrene with maleic anhydride and methacrylic acid can produce the membrane pores that are permeable to low-molecular-mass compounds. At the same time, poly(L-glutamic acid), poly(vinyl sulfate), and DNA exert no effect on the membrane permeability, although they are sorbed on the membrane surface.     

Shell-crosslinked nanostructures from amphiphilic AB and ABA block copolymers of styrene-alt-(maleic anhydride) and styrene: polymerization, assembly and stabilization in one pot

Shell-crosslinked nanostructures having unusual rosette morphologies have been produced by a simple process from styrene and maleic anhydride.     

Copolymerization of Maleic Acid with Acetophenone-Containing Bottoms from Styrene Distillation

The feasibility was studied for producing polymeric materials by high-temperature copolymerization of maleic acid with styrene distilation bottoms from joint production of styrene and propylene oxide. Regression equations were derived to predict the conditions for preparing the copolymer with the required properties. The structure, properties, and fields of possible application of the copolymer were studied.     

Novel copolymers via nitroxide mediated controlled free radical polymerization of vinyl chloride

Controlled free radical polymerization (CFRP) of vinyl chloride (VCM) and copolymerization with several comonomers have been studied in aqueous suspension. Therefore di-tert-butylnitroxide and three novel nitroxyl radicals were used as mediating agents. Copolymerization of VCM with styrene, partly combined with acrylonitrile, maleic acid anhydride and maleic acid imide as well as methyl methacrylate, n-butyl methacrylate, butyl acrylate and butadiene have been achieved, demonstrating an efficient route for novel vinyl chloride copolymer architecture.     

Homogeneous asymmetric catalysis by means of chiral metal complexes of 2,3-bis(dimenthylphosphino)maleic anhydride and of 2,3-bis(dimenthylphosphino)maleimide derivatives

2,3-Bis(dimenthylphosphino)maleic anhydride and also 2,3-bis(dimenthylphosphino)maleimide derivatives have been prepared from 2,3-dichloromaleic anhydride, 2,3-dichloro-N-phenylmaleimide and 2,3-dichloro-N-methylmaleimide, respectively, and dimenthyl(trimethylsilyl)phosphine. These compounds have been used as ligands for Rh complexes in the asymmetric hydrogenation and hydrosilylation. Ni and Pd complexes of these ligands were tested in the Grignard cross-coupling reaction.

The hydrogenation of -acetamido cinnamic acid gave 70% enantiomeric excess (ee) and hydrogenation of acetophenone up to 47% ee. Hydrosilylation of acetophenone led to 42% ee.

Attempts to asymmetric cross-coupling reactions resulted in very low enantiomeric excess.     

Sn-promoting mechanism for ketone hydrogenation over Rh/SiO2

Hydrogenation of acetophenone, 2-butanone, styrene and 1-hexene over Rh---Sn/SiO₂ in heterogeneous liquid phase reaction systems was studied by in situ EXAFS, FT-IR, TEM, analytical TEM, CO and H₂ adsorption measurements. The catalytic activity of Rh/SiO₂ for hydrogenation of acetophenone and 2-butanone increased by a factor of 5–500 by Sn addition, showing a maximum activity at surface composition Sn_s/Rh_s = 1.5, whereas hydrogenation of styrene and 1-hexene decreased monotonously and drastically by Sn addition. In situ Sn K-edge EXAFS of the well characterized CVD-Rh---Sn/SiO₂ catalyst prepared by using Sn(CH₃)₄ vapor suggested that oxygen of C=O group makes a bond with Sn atom upon acetophenone adsorption.     

On the role of monomer—monomer donor—acceptor complexes in the free-radical copolymerisation of styrene and maleic anhydride

The kinetics of the free-radical copolymerisation of styrene and maleic anhydride at 60° in bulk and in several solvents have been studied. Copolymer compositions may be interpreted either in terms of a mechanism involving a penultimate group effect or in terms of a mechanism involving some propagation via styrene—maleic anhydride donor—acceptor complexes. However, experiments at various overall monomer concentrations and in which zinc chloride and phthalic anhydride have been added indicate that the penultimate group effect mechanism is to be preferred.     

Supramolecular Systems from Natural Polymers and Maleic Polyelectrolytes

Summary: The formation of polyelectrolyte complexes by interaction between chitosan and maleic acid copolymers as strong/weak dibasic polyanions was investigated. The interaction between the sodium salt of maleic acid copolymers with styrene or vinyl acetate and the chitosan hydrochloride in aqueous solution was followed by potentiometric, conductometric and turbidimetric titration. The effect of the added low molecular salt on the complex formation was also investigated. The precipitated complexes were analyzed by FTIR spectroscopy and TG analysis. Preliminary layer-by-layer deposition experiments were performed to obtain thin films.     

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.     

Free-radical multicomponent polymerization reactors and chemical composition distribution

Formulae to calculate the statistically caused instantaneous copolymer composition distribution as well as the chemical distribution of accumulated macromolecules, which is due to polymerization statistics and shifts in mean polymer composition during the reaction process, are derived on the basis of a universal model for free-radical solution polymerization with any number of monomers proceeding in a batch, semi-batch or continuous, ideally mixed vessel. The influence of the reactor type on chemical composition distributions is investigated for a copolymerization of different reactive components (methyl methacrylate/styrene/maleic anhydride), a system with nearly equal reactive monomers (methyl methacrylate/styrene), and the ternary polymerization of methyl methacrylate/styrene/maleic anhydride. Though products of constant mean composition are obtainable in a semi-batch or steady-state continuous reactors, considerable statistical dispersion cannot be removed in any case.     

3-氨丙基三乙氧基硅烷对溶胶-凝胶法苯乙烯-顺丁烯二酸酐共聚物/SiO_2杂化材料的制备与性能的影响

用３ 氨丙基三乙氧基硅烷（ＡＰＴＥＳ）作为偶联剂，通过溶胶 凝胶（Ｓｏｌ Ｇｅｌ）过程制得两相以共价键结合的透明苯乙烯 顺丁烯二酸酐共聚物／ＳｉＯ２杂化材料．通过ＦＴＩＲ分析等证实了材料有机相与无机相间是以共价键结合的．分析了材料热处理温度和分别用盐酸或氨水作催化剂时对材料溶胶分数的影响、偶联剂及其用量对溶胶 凝胶体系凝胶时间的影响、并研究了杂化材料中无机含量对材料折射率和Ｔｇ的影响