The Effect of Cyclodextrins in Polymer Particles Synthesis

The free radical polymerization of styrene in water in the presence of β-cyclodextrin (β-CD) is described.It is found that β-CD could greatly accelerate the polymerization,enhance the final conversion of monomer.The particle-size distribution of the final polymer is also improved than that without β-CD in the system.     

Stability of Suspensions of Bioactive Particles Using Hybrid Organic–Inorganic Solutions as Dispersing Media

Functional coatings incorporating different types of particles developed by the sol–gel method have been proposed in the last few years for diverse applications. This work focuses on the preparation of homogeneous coatings prepared from stable suspensions with 10 wt% of glass and glass ceramic particles in a hybrid organic–inorganic solution as dispersing media. For this purpose, the pH was shifted up to 6–7 by adding tetrapropylammonium hydroxide (TPAH) which behaves as a cationic surfactant being probably adsorbed on the particles surface, while the sol maintains stable. Rheological measurements were performed to study the stability of the suspensions prepared at different conditions such as the kind and concentration of dispersant and the pH conditions. After sintering at 450^∘C/30 min, coatings around 2 μ m in thickness were obtained.     

Viscosity of Polymer–Bitumen Binders

Polymer–bitumen binders for the highway engineering were obtained by the addition of a ternary ethylene–propylene rubber to a bitumen. The addition of a vulcanizing agent to a polymer–bitumen composition caused the structuring of the system through cross-linking of rubber molecules in the bitumen matrix that was confirmed by the study of structural viscosity of the polymer–bitumen compositions, as well as molecular mobility by the methods of NMR-relaxation and pulsed field gradient NMR-relaxation (self-diffusion).     

Synthesis of Molecularly Imprinted Polymer Particles by Suspension Polymerization in Silicon Oil

Molecular imprinting is a method to prepare polymers with recognition site of desired and predetermined selectivity1. Molecularly imprinted polymers (MIP) are prepared by copolymerizing functional and cross-linking monomers in the presence of a molecular …     

Dowex Polymer–Mediated Protection of Carbonyl Groups

Dowex (strongly acidic cationic exchange resin) polymer is employed as solid acid catalyst for the clean and less hazardous protection of carbonyl compounds as phenylhydrazones and 2,4‐dintrophenylhydrazones in ethanol under reflux conditions. The reactions proceed very smoothly and the yields of the derivatives are excellent.     

Studies of the Atrazine Aqueous Suspension Stability in the Presence of an Anionic Polymer—Influences of Polymer Molecular Weight and Solution pH

The influence of the molecular weight of sodium salt of styrene/methacrylic acid (SSMA) copolymers and solution pH value (range of 3–11) on the stability of the atrazine suspension was studied. SSMA with different molecular weights was synthesized by emulsion polymerization. Adsorption, zeta potential measurements, microscopy, and suspension stability measurements were carried out. The obtained results indicate that the adsorption of SSMA on the surfaces of atrazine particles decreases with the increase of the molecular weight, and the hydrogen bonding is the main adsorption force. The presence of SSMA improves the stability of the atrazine suspension. The stability of the atrazine suspension decreases with the increase of the molecular weight of SSMA. On the other hand, the stability of the atrazine suspension with SSMA increases firstly and then decreases with the increase in solution pH in the range of 3–11.     

Stability and Structure of Silver–l-methionine Complexes

Journal of Solution Chemistry - Stability and structure of complexes between silver (I) and l-methionine (L) deduced from potentiometric and 1H NMR measurements allow to assume the prevailing of...     

Stability of mechanical properties of molecular layer–deposited alucone

We report on the effect of aging on the mechanical properties of molecular layer–deposited (MLD) thin films. We studied the mechanical failure of the films during uniaxial tensile testing and observed a sixfold difference in the crack-onset strain (COS) and related flexibility within the first two days after the samples were exposed to ambient air. The MLD films made using trimethylaluminum and ethylene glycol are notorious for exhibiting structural changes after the fabrication; we show that these changes are detrimental for mechanical robustness of the films. This information aids to plan the handling or the protection of these films to achieve better performance with these materials. The interfacial shear strains and COSs of the shortly air-exposed 300-nm-thick films were observed to be roughly 0.3% and 1.8%, respectively. These values are the highest reported so far for hybrid organic–inorganic MLD thin films and would extrapolate to about 14% COS for 5-nm-thick film, indicating potential applications as interfacial adhesion layer for films on polymer substrates and as a protective coating in battery applications.     

Studies on Acrylic Emulsion Polymerization Containing Hydrophilic Hydroxyl Monomer in the Presence of Nano‐SiO2 Particles

Emulsion polymerization with nano‐scale SiO₂ particles as seeds composed of methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA), and acrylic acid (AA) was studied from varying reaction temperatures, level of SiO₂ particle, HEMA, and emulsifier. The morphology of the emulsion particle was examined with a transmission electron microscope (TEM). The results showed that the addition of nano‐SiO₂ particles decreased the coagulum greatly when its level was lower than 7%. The coagulum also decreased with the increasing of temperature from 65°C to 75°C. The level of HEMA and emulsifier had little influence on the coagulum in the presence of nano‐SiO₂. The particle size of the emulsion increased with the increase of level of nano‐SiO₂ and HEMA. Part of the emulsion particles connected together due to the existence of HEMA, and yet some of the nano‐SiO₂ particles were not covered with polymer.     

Size Distribution of Nematic Clusters in Oligomer–Polymer Systems

A physical prerequisite for the formation of nematic clusters in olygomer–polymer systems is considered. A simple geometrical model is proposed that allows, based on a kinetic analysis of the process, obtaining the expression for the cluster size distribution function where , K ₁ and K are the equilibrium constants of first and consecutive additions, and a _n and a ₁ are the equilibrium concentrations of clusters and elementary particles (oligomer molecules). The dependence of the distribution function on the intermolecular interaction energy and the chain rigidity is analyzed.     

Structure and Electrocatalytic Properties of Copper-Containing Aniline–Melamine–Formaldehyde Polymer Composites

Mixed aniline–melamine–formaldehyde polymer was synthesized by parallel polycondensation of the monomers with formaldehyde. Copper(II) chloride and copper oxides (CuO, Cu₂O) were introduced in situ the process. X-ray diffraction analysis revealed the presence of crystalline CuO phases at introducing CuCl₂ into the polymer and the appearance of copper particles in all the synthesized composites after using them as catalysts in electrohydrogenation of o-nitroaniline, which is caused by electrochemical reduction of copper cations from copper oxides. The use of the synthesized composites for the cathode activation in electrohydrogenation of o-nitroaniline increases the process rate by a factor of 1.5–2.5 compared to electrochemical reduction, and with 100% conversion to o-phenylenediamine.     

Solvent Dependence of the Monomer–Dimer Equilibrium of Ketone-Substituted Triscatecholate Titanium(IV) Complexes

Hierarchical helicates based on ketone-substituted titanium(IV)triscatecholates show different monomer-dimer behavior depending on different solvents. The dimerization constants of a whole series of differently alkyl-substituted complexes is analyzed to show that the solvent has a very strong influence on the dimerization. Hereby, effects like solvophobicity/philicity, sterics, electronics of the substituents and weak side-chain—side-chain interactions seem to act in concert.     

Monomer–Dimer Control and Crystal Engineering in TASPs

We have reported a template assembled synthetic protein (cavitein Q4) as an unexpected dimer in the solid state and as a monomer–dimer equilibrium in solution. We have since reported an ability to bias a cavitein’s monomer–dimer equilibrium in solution by sequence design involving histidine metal chelation or disulfide incorporation. However, little remains known about the forces contributing to dimeric cavitein crystal nucleation and lattice stabilization. We, therefore, designed glutamine variants to probe factors involved in dimeric cavitein crystallization. It was found that a key glutamate hydrogen-bonding interaction between dimers is integral to crystal formation and stabilization. Additionally, we obtained a crystal structure of a cavitein (Q4-E3H) designed to bias the dimeric structure via histidine metal coordination. The resolved structure indicates a histidine cluster interaction that likely accounts for the biased dimeric form observed in solution.     

Development of β-cyclodextrin-Modified Silica and Polyporous Polymer Particles for Solid-Phase Extraction of Methyl Jasmonate in Aqueous and Plant Samples

Two novel kinds of materials, β-cyclodextrin(CD)-modified silica and polyporous polymer particles, were prepared for solid phase extraction of methyl jasmonate (MeJA) in aqueous conditions. β-Cyclodextrin-modified silica was prepared by a sol-gel process and polyporous polymer was formed by 4-vinylpyridineas (4-VP) and ethyleneglycol dimethacrylate (EGDMA). For better extraction properties, preparation conditions were optimized. Bare silica particles were prepared for comparison of β-cyclodextrin-modified silica, and different kinds of monomers and the ratio of monomer to cross-linker were studied for polyporous polymer. To evaluate the usability of the two materials, extraction kinetics and isotherm curves were systematically studied. The extraction conditions were also optimized and both materials showed good extraction efficiency for MeJA, when evaluating by standard solution, enrichment factors of 56.5 and 75.3 were obtained for MeJA. Solid-phase extraction (SPE) -HPLC methods based on β-CD-modified silica and poly(4-VP-EGDMA) were also established for the determination of MeJA in aqueous samples. Good linearity was observed with R² ≥ 0.998, and the low detection limits were found to be 2 and 3 ng/mL by UV detection. Finally, β-CD-modified silica and poly(4-VP-EGDMA) based SPE-HPLC methods have successfully been applied to determine MeJA in the wintersweet flower; recoveries were tested and found to be in the range of 79.0 to 87.3%.     

Determination of Absolute Rate Constants for Radical Polymerization and Copolymerization of Ethyl α-Chloroacrylate: Effects of Substituents on Reaction Rates of Monomer and Polymer Radical

The propagation and termination rate constants (k_p and k_t) for the radical polymerization of ethyl a-chloroacrylate (ECA) were determined by the rotating sector method k_p = 1660 and k_t = 3.33 × 10⁸ L/mol?s at 30° C. The absolute rate constants for cross-propagations in copolymerization were evaluated from the k_p determined for ECA or those for common monomers and the monomer reactivity ratios. The reactivities of ECA and poly-(ECA) radicals estimated as the rate constants of cross-propagations were accounted for by using equations relating these rate constants to the polar and resonance effects of the substituents. ECA was highly reactive toward various polymer radicals as expected from the resonance effects of the carbethoxy and chloro substituents. The poly(ECA) radical was found to be more reactive than common polymer radicals. The reactivity of a polymer radical in cross-propagation seemed to increase with increasing electron-accepting power by facilitating electron transfer from a monomer required for the new C-C bond formation.     

Effect of Polymer on Dynamic Interfacial Tensions of Anionic–nonionic Surfactant Solutions

The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer systems against n-decane have been investigated using a spinning drop interfacial tensiometer in this paper. Two anionic–nonionic surfactants with different hydrophilic groups, C₈PO₆EO₃S (6-3) and C₈PO₆EO₆S (6-6), were selected as model surfactants. Partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed. The influences of surfactant concentration, temperature, polymer concentration, and oleic acid in the oil on IFTs have been studied. The experimental results show that anionic–nonionic surfactants can form compact adsorption films and reach ultralow IFT (10^?3 mN/m) under optimum conditions. The addition of polymer has great influence on dynamic IFTs between surfactant solutions and n-decane mainly by the formation of looser mixed films resulting from the penetration of polymer chains into the interface. The compact surfactant film will also be weakened by the competitive adsorption of oleic acid, which results in the increase of IFT. Moreover, the penetration of polymer chains will be further destroyed surfactant/polymer mixed layer and lead to the obvious increase of IFT. On the other hand, polymers show little effect on the IFTs of 6-6 systems than those of 6-3 because of the hindrance of longer EO chain of 6-6 at the interface.     

Effect of Monomer Feeding Mode on thePreparation of Hollow Latexes with High MAA Content in the Core Latex Preparation简

In order to prepare hollow latex particles with optimum morphology based on osmotic swelling principle, three- layer core/shell latex particles with 40 wt% MAA in the core were first prepared via multistep seeded emulsion copolymerization, in which monomers were added by a semi-continuous process with monomer addition under two different forms： pure monomers＇ mixture （monomer addition）, and pre-emulsified monomers （pre-emulsion addition）. Then, the hollow latex particles with different morphologies were obtained after alkali post-treatment. Influences of the monomer feeding mode on the emulsion polymerization and the particle morphology were investigated. Results showed that the pre- emulsion addition could significantly improve the polymerization stability in each step, and greatly enhance the uniformity of shell encapsulation. The sizes of the core and core/shell latex particles obtained by the pre-emulsion addition were smaller and more uniform than those synthesized by the monomer addition, and the hollow latex particles with intact morphology were generated by alkali post-treating of the core/shell latexes prepared from the pre-emulsion addition. As the core size increased, the morphology of the post-treated particles underwent evolution from hollow to collapse. Moreover, the mechanism of the particle morphological evolution was proposed.     

On the Reactivity and Stability of Iodide–Nitride–Sulfide Clusters of Neodymium and Dysprosium

The thermal decomposition of cluster Nd₃I₅(S₂)(S₂N₂)(THF)10 (I) at 50–400°C affords a mixture of products among which tetrahydrofuran (THF), sulfur, diiodine, HI, H₂S, CS₂, S₃N₆, S₃N₅, MeI, thiophene, tetrahydrothiophene, diiodobutane, iodobutene, and NdI₃ are identified. The treatment of Ln₃I₅(S₂)(S₂N₂)(THF)₁₀ (Ln = Nd (I), Dy (II)) with phenanthroline (Phen) in THF at room temperature results in the partial substitution of ТНF to form new complexes Ln₃I₅(S₂)(S₂N₂)(THF)₄(Phen)₃. The dissolution of compound I in pyridine gives a pyridine (Py) complex Ln₃I₅(S₂)(S₂N₂)(THF)3(Py)₇. The dissolution of compounds I and II in acetonitrile at 20°C is accompanied by the fast rearrangement and fragmentation of the complexes to form LnI₃(MeCN)₆, [LnI(S₂)(MeCN)], and [LnI(S₂N₂)(MeCN)]. Complex I in THF does not react with white phosphorus, carbon monoxide, fullerene C₆₀, and chromium hexacarbonyl.