Synthesis of 2-mercaptobenzimidazole from the reaction of o-phenylene diamine and carbon disulfide in the presence of potassium hydroxide

The reaction of o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI) enhanced by potassium hydroxide was carried out in a homogeneous solution. No catalysts are required in the reaction. In addition to the reaction of carbon disulfide and hydrogen sulfide to produce S²⁻ and CS₃²⁻, potassium hydroxide is also acted as the enhancer to promote the reaction of synthesizing MBI. A mixture of organic solvent (protic or aprotic solvent) and water is used as the reaction solution in order to obtain a homogeneous phase. The effects of the reaction conditions, including the amount of o-phenylene diamine, amount of carbon disulfide, organic solvents, volume ratio of organic solvent to water, and temperature, on the conversion of o-phenylene diamine were investigated in detail. An appropriate amount of KOH is recommended to produce a high yield of MBI and a high reaction rate in using protic solvent/water as the mixed solution. Nevertheless, the conversion is increased with the increase in the amount of KOH using aprotic solvent. This behavior is different from that of the KOH effect on the conversion of o-phenylene diamine using protic solvent/water as the mixed solution.     

A facile preparation of highly interconnected macroporous poly(d,l-lactic acid-co-glycolic acid) (PLGA) scaffolds by liquid-liquid phase separation of a PLGA-dioxane-water ternary system

Regular and highly interconnected macroporous scaffolds ranging in size from 50 to 150 μm were fabricated from poly(d,l-lactic acid-co-glycolic acid) (PLGA)-dioxane-water ternary systems via thermally induced phase separation (TIPS) without any surfactant or other additives. The effect on scaffold morphology of processing parameters including quenching temperature, polymer concentration, solvent composition and molecular weight, was investigated as a function of quenching time. The cloud-point temperature of the polymer solution was found to depend on polymer concentration, solvent composition, and polymer molecular weight. The water content in the solvent mixture had the greatest effect on the cloud-point temperature. The optimal quenching temperature for preparing macroporous inter-connected scaffolds from a 9 wt% PLGA solution (dioxane-water=87/13, by wt) was less than −7 °C. In low viscosity PLGA solutions, sedimentation of the polymer rich phase occurred due to the segregation of the separated phases under gravity. This led to the formation of scaffolds with irregular and closed pores.     

Influence of trisamide-based additives on the morphological and mechanical properties of isotactic polypropylene

The influence of two different trisamide-based additives on the morphological and mechanical behavior of isotactic polypropylene (PP) is investigated. Morphological investigations by wide-angle X-ray scattering (WAXS) show that only 0.04 wt.-% of one of the additives is enough to induce 80% beta modification in the crystalline part of the polymer. The materials are investigated with quasistatic (tensile testing) as well as short-time dynamic (Charpy impact strength) methods and for the first time fatigue crack growth measurements are performed on alpha- and beta-nucleated PP. In all cases a much higher toughness of the material containing the beta-nucleating agent (beta NA) can be observed. The crack growth propagation rate is one order of magnitude smaller with the use of the beta-nucleating agent compared to the alpha polymer. Scanning electron microscopy (SEM) pictures are used to support the correlation of the mechanical behavior with the morphological changes.     

Application of thermo-responsive poly(methyl vinyl ether) containing copolymers in combination with ultrasonic treatment for pigment surface modification in pigment dispersions

The process of surface modification of hydrophobic organic (copper phthalocyanine (CuPc)) as well as hydrophilic inorganic pigments (titanium dioxide) in aqueous dispersions by employing tailor-made thermo-responsive copolymers and the colloidal stability have been studied as a function of temperature. The pigment surface modification is achieved by conventional adsorption and by thermoprecipitation of amphiphilic methyl vinyl ether (MVE) containing block and graft copolymers, exhibiting a lower critical solution temperature (LCST), with poly(isobutyl vinyl ether) blocks and poly(ethylene oxide) side chains, respectively. The effect of mechanical treatment of the pigment dispersion by ultrasonic power alone or in combination with the LCST property was investigated. The course of the pigment surface coating process was followed by the electrokinetic sonic amplitude (ESA) method. The temperature-controlled sorption of PMVE-g-PEO graft copolymers on both inorganic and organic pigment surfaces was investigated. It was found that ultrasonic treatment together with LCST thermoprecipitation is a promising method for the surface modification of pigments with regard to dispersion stability.     

Indole and 5-chloroindole as inhibitors of anodic dissolution and cathodic deposition of copper in acidic chloride solutions

The effect of indole, IN, and 5-chloroindole, Cl-IN, on the anodic dissolution of copper in acidic sodium chloride solutions was studied using voltammetry on a rotating disc electrode (RDE). Both compounds used at 10^–3 M concentration act as strong inhibitors on the copper dissolution, but indole exhibits better inhibiting properties. The inhibitory action substantially increases with decreasing solution pH. The influence of these organic additives on the electrodeposition of copper on platinum was also investigated using RDE and electrochemical quartz crystal microbalance (EQCM) techniques. The EQCM measurements show that a sparingly soluble layer of the inhibitor is responsible for the protective effects observed in chloride solutions.     

Influence of Some Organic Additives on the Extractive Separation of Americium(III) by Sulfoxides

Abstract

The solvent extraction behavior of americium(III) from aqueous nitrate media by two long-chain aliphatic sulfoxides has been examined systematically in the presence of several water-miscible organic solvents to study their possible synergistic effect on metal ion extraction. Methanol, ethanol, n- and isopropanol, n-butanol, dioxane, acetone, as well as acetonitrile, were employed as the organic component of the mixed (polar) phase. These additives affected the extraction to varying degrees. Extractability of Am increased 5 to 10-fold with increasing concentration of some of these additives, with the maximum enhancement being observed in the presence of acetone or acetonitrile. However, alcohols are generally very poor in this respect. Possible reasons for such behavior are briefly discussed. The distribution of several common contaminants was also investigated at the optimum condition for americium extraction.     

Effects of Membrane-Making Conditions and Shrinkage Treatment on Morphology and Performance of Cellulose Acetate Butyrate Membranes

Abstract

The functions of additives in cellulose acetate butyrate (CAB) membrane casting solution, effect of thermal shrinkage treatment on porous CAB membranes, and the changes of CAB membrane surface morphology during the solvent evaporation step have been investigated. Additives (glycerol and lactic acid) in CAB membrane casting solution function only as pore number promoting agents when used at low concentration and function both as pore number and pore size promoting agents when used at higher concentrations. Triethyl phosphate in CAB membrane casting solution functions both as a pore number promoting agent and as a secondary solvent for CAB. Three distinct phases can be observed in the solvent evaporation step in making CAB membranes. With the increase in solvent evaporation time, the number of pores in the first pore size distribution increases in the initial small pore-forming phase and decreases in the large pore-forming phase, and the number of pores in the second pore size distribution always increases with solvent evaporation time. These changes in pore numbers, pore sizes, and pore number ratio in two pore size distributions as well as the membrane skin layer thickness together govern the ultimate membrane performance and result in a maximum solute separation which, in the case of CAB/ acetone membranes, falls at 60 seconds of solvent evaporation time. Significant improvement of the performance of a porous CAB membrane can be achieved by thermal shrinkage treatment. Equally high CAB membrane performance can also be achieved by using a lower concentration of additives in the membrane casting solution.     

Electrolyte additives for enhanced thermal stability of the graphite anode interface in a Li-ion battery

The influence of electrolyte additives on the thermal stability of graphite anodes in a Li-ion battery has been investigated. The selected additives are: ethyltriacetoxysilane, 1,3-benzoldioxole, tetra(ethylene glycol)dimethylether and vinylene carbonate. These compounds were added in 4% to an electrolyte consisting of 1M LiBF₄ ethylene carbonate (EC)/diethyl carbonate (DEC) solvent mixture. Differential scanning calorimetry (DSC) was used to investigate the thermal stability. The electrochemical performance was investigated by galvanostatic cycling and the formed solid electrolyte interphase (SEI) was characterised by photoelectron spectroscopy (PES) using Al Kα and synchrotron radiation (SR). The onset temperature for the thermally activated reactions was found to increase for all electrodes cycled with additives compared to electrodes cycled without additives. The onset temperature increased in the order: no additive < tetra(ethylene glycol)dimethyl ether < 1,3-benzoldioxole < ethyl-triacetoxysilane < vinylene carbonate. Features in the PES spectra found to be associated with high onset temperatures for thermally activated reactions are: (i) no discernible graphite peak, (ii) small amount of salt species of the type LiF and Li_xBF_yO_z and (iii) larger amounts of organic compounds preferably with a high oxygen content.     

Solution intercalation of polystyrene and the comparison with poly(ethyl methacrylate)

Polystyrene nanocomposites have been prepared via solution intercalation method. Combination of wide-angle X-ray diffraction and thermogravimetric analysis is used to study the effect of solvents on the morphology of the nanocomposites as a function of the amount of residual solvent. d-Spacing of the polystyrene nanocomposites has a minimum value when the residual solvent concentration is between 2 and 4 wt%. Different interaction level between the solvent molecules and polymer chains is considered to be the reason for this special d-spacing change behavior. By comparing the solution intercalation of polystyrene and poly(ethyl methacrylate) from different solvents, it is concluded that the interactions between polymer-surfactant, solvent-surfactant, and polymer-solvent play important role for the solution intercalation of polymers.     

Capacitance properties of electrochemically deposited polyazulene films

Polyazulene films formed by electrochemical oxidation of azulene have been studied as active components in electrochemical capacitors. The film shows reversible electrochemical behavior in the positive potential range and exhibits p-doping properties. The influence of film formation conditions on the films electrochemical properties has been investigated. A strong effect of solvent on the polyazulene deposition has been observed. The highest yield of film deposition was found for dichloromethane. Polyazulene films also exhibit stable voltammetric properties in aprotic solvents. The voltammetric response of the film is affected by the size of the anion of the supporting electrolyte. In solutions containing tetra(alkyl)ammonium perchlorates, tetrafluoroborates or hexafluorophosphates, reversible oxidation of polyazulene is obtained. In the presence of large tetra(phenyl)borate anions, polyazulene is irreversibly oxidized upon electrochemical oxidation. The capacitance properties of these materials have been investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The polyazulene film displays a relatively high specific capacitance close to 400 F g⁻¹. Such high value of C_s locates this material among very good polymeric redox pseudo-capacitors.     

Hollow fiber formation using Lewis acid : Base complex in the polymer solution

In the present work, hollow fiber formation was investigated by using Lewis acid : base complexes in the polymer solution. The studied systems consisted of poly(ether sulfone); N‐methyl‐2‐pyrrolidone (NMP) as solvent and Lewis base, and acetic, propionic, n‐caproic, and adipic acids as additives and Lewis acids. Bore liquid was formed by water/NMP solutions, as well as vaseline; whereas water was used as external precipitation bath. The spinneret and precipitation bath distance (i.e., air gap) also varied. The membranes were characterized by scanning electron microscopy and pure gas permeation tests. The influence of the complex dissociation rate was observed mainly when a reduction to water inflow from the bore liquid to the polymer solution occurred, because in this case, dissociation rate was inhibited. Therefore, stability was favored in the sublayer for a longer period, allowing macrovoid formation. These results are also evidenced by the permeability coefficients, which increased as fast as the polymer solution reaches water (i.e., the kinetics of precipitation was accelerated). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 908–917, 2001     

Crystallization kinetics and affecting parameters on polycaprolactone composites with inorganic and organic additives

The isothermal crystallization and mechanical behavior of biodegradable polycaprolactone (PCL) composites with organic (oleic acid and glycerol monooleate) and inorganic (zinc oxide, organoclay, and hydroxy apatite) additives used alone or simultaneously were investigated. The effect of all additives on the degree of crystallinity percentage (DOC%), isothermal crystallization kinetics parameters, and mechanical test results of PCL composites was studied. The PCL composite films were prepared by solvent casting by using dichloromethane as the solvent. The films were characterized by X‐ray diffraction, differential scanning calorimetry (DSC), and tensile tests. DSC of the first melting and X‐ray diffraction DOC% results (for composites by solvent casting) are compatible. The values by DSC of the second melting (for composites by extrusion method) are lower. Organoclay gives the highest crystallinity among the other inorganic additives used. Small amounts of inorganic additives act as a nucleating agent and increase the crystallinity; the higher amounts decrease. The organic additives act as the plasticizer. When used alone, it lowers the crystallinity, but when used with inorganic additives, it improves the dispersion of inorganic particles in the polymer matrix. The isothermal crystallization kinetics parameters by Avrami analysis showed that crystallization was controlled by nucleation and the crystals had spherical structure. The nucleation type changed between thermal and athermal nucleation. The Pukanzky model interaction parameter B indicated that the organic additives improved the dispersion of inorganic particles in the polymer matrix. Statistically significant, eight correlations (F > 6) were obtained for the crystallinity, crystallization parameters, Young's modulus, and tensile strength as a function of concentration of additives. J. VINYL ADDIT. TECHNOL., 21:174–182, 2015. © 2014 Society of Plastics Engineers     

Synthesis,characterisation and solution thermal behaviour of a family of poly (N-isopropyl acrylamide-co-N-hydroxymethyl acrylamide) copolymers

Thermo-responsive copolymers of poly (N-isopropyl acrylamide-co-N-hydroxymethyl acrylamide)p(NIPAAm-co-HMAAm) with a range of content of hydroxy groups have been synthesised by free radical polymerisation. The polymers were characterised by NMR, FTIR and GPC. A detailed study of the solution thermal properties showed that polymers with up to about 50 wt.% hydroxy monomer show lower critical solution temperature (LCST) properties in water. Polymers with higher hydroxy monomer content are fully soluble at all temperatures up to 100 °C. The effect of pH, salts and solvent additives on the solution thermal behaviour of the copolymers was investigated, showing that “salting-out” salts lowered the LCST and “salting-in” salts caused an initial increase in LCST at low concentrations, but reduced LCST at higher concentrations, in line with the Hoffmeister series. The LCST of any copolymer composition from this family in pure water can be predicted from the empirical equation; LCST = 0.015x² + 0.25x + 31.76, where x is the fraction of the hydroxy monomer. Due to differences in polarity and the length of the carbon chain, methanol and ethanol altered LCST of p(NIPAAm) and its hydroxyl copolymers in different manners, showing a transition from cononsolvency to cosolvency as the hydroxyl content of the copolymer increased. A more complex polyhydroxy compound, sucrose, had very little effect on LCST for either p(NIPAAm) or its hydroxyl copolymers.     

The influence of chloride and sulphate ions on the corrosion behavior of Ti and Ti-6Al-4V alloy in oxalic acid

The electrochemical behavior of pure Ti and Ti-6Al-4V alloy was investigated in oxalic acid solution using various electrochemical techniques, i.e. open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance measurements (EIS) and surface examination via scanning electron microscope (SEM) technique. The influence of concentration and temperature on the electrochemical behavior of TI and its alloy were also studied. The results of polarization measurements showed that corrosion current density (i_corr) increases with increasing either temperature or oxalic acid concentration for both samples. Moreover, the value of i_corr for Ti was found to be lower than that for Ti-6Al-4 V alloy, where the corrosion resistance for titanium was always higher. The effect of additives as SO₄²⁻ and Cl⁻ ions was studied; results indicated that the oxide film resistance (R_ox) value decreases with increasing the concentration of SO₄²⁻ ion. However, for Cl⁻ ion, the value of R_ox decreases with increasing Cl⁻ ion concentration up to 1 mM before it starts to increase at higher concentrations. EIS and polarization results are in good agreement with each other. The obtained results were confirmed by surface examination.     

聚乙烯吡咯烷酮添加剂对聚醚砜制膜体系的影响

本文考察了不同ＰＶＰ／ＰＥＳ比率对ＰＥＳ／ＰＥＳ／ＰＶＰ／ＤＭＡｃ／Ｈ２Ｏ制膜体系热力学平衡关系、成膜动力学因子Ｄｅ以及膜分离性能的影响，揭示了亲水性聚合物添加剂ＰＶＰ在ＰＥＳ膜形成过程中所起的作用。结果表明：ＰＶＰ不是单纯的致孔剂，它改变了制膜液相平衡关系及浸入沉淀进非溶剂侵入速速度而延迟或促进相分离，从而影响了成膜的结构和分离性能。     

Preparation of porous PVC membrane via a phase inversion method from PVC/DMAc/water/additives

Poly(vinyl chloride) membranes were prepared via a phase inversion method, using N,N‐dimethylacetamide (DMAc) as solvent, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and sucrose as three typical additives and water as the coagulation medium. The phase diagrams of the PVC/DMAc/additives/water quaternary systems were constructed using cloud‐point experimental data. With the addition of the different additives, the effect of dope solution temperature on the dope solution viscosity and the structure of membranes were investigated. It indicates that the viscosity of the PVC/DMAc dope solution with the additive increase compared with the dope solution without any additive and the addition of the additives into the dope solution alter the morphology and structure of the resultant membranes during the phase‐inversion process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of aliphatic esters on the formation and degradation behavior of PLGA-based in situ forming system

The purpose of this study was to investigate the effect of three aliphatic esters, ethyl heptanoate, methyl heptanoate, and ethyl nonanoate on the in vitro degradation behavior of in situ forming systems. In situ forming implants based on 33% (w/w) poly (lactide-co-glycolide) (PLGA)/57% (w/w) N-methyl-2-pyrrolidone (NMP)/10% (w/w) esters were prepared after injection of the final formulation in phosphate buffer solution (pH 7.4, 0.2 M) at 37 °C. The influence of additives on the implants formation, morphology, and also on their in vitro degradation behaviors over a period of 45 days was investigated. The degraded matrices were evaluated to determine morphological analysis by SEM and ¹H-NMR study. The solution of degradation medium was studied to indicate NMP removal and altering acidity. The results showed that the additives generated a high porous structure and caused the fast phase inversion. However, the ¹H-NMR spectra indicated that ester additives remained in the matrices during degradation periods. The results of the acidity study showed that the degradation rates in the matrices containing esters were higher than the control matrix. In addition, it is shown that esters with lower molecular weight have affected the polymer degradation more efficiently than higher molecular weight esters.     

Swelling characteristics of NR/PU block copolymers and the effect of NCO/OH ratio on swelling behaviour

A series of (NR/PU) block copolymers (BCs) was prepared from toluene diisocyanate (TDI), 1,3-butane diol (1,3-BDO), and hydroxyl-terminated liquid natural rubber (HTNR), by solution polymerisation. The swelling characteristics of the BCs were investigated. Diffusion profile in various solvents and the sorption kinetics were studied. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, the influence of NCO/OH ratio on the swelling behaviour was also studied. The equilibrium sorption value (Q_∞) decreased with increasing NCO/OH ratio for all the BCs. The samples have higher uptake of solvents with solubility parameter within a small range centred about 9 (cal/cm³)^1/2. Highly polar and non-polar solvents show minimum uptake. It was observed that polarity factor predominates in the solvent transport through the present block copolymer systems. The sorption behavior is also found to vary with the NCO/OH ratio employed in the preparation of polyurethane (PU) oligomers.     

Studies on the influence of long chain acrylic esters polymers with polar monomers as crude oil flow improver additives

This study investigated the efficiency of 22 polymer additives of defined and controlled structural characteristics in improving the flow properties of crude oil. The additives were synthesized by the solution polymerization of alkyl acrylates of various alkyl chain lengths with styrene, acrylic acid and 1-vinyl-2-pyrrolidone as copolymers or terpolymers. Polymerization was performed by tert-butylperoxy-2-ethylhexanoate as initiator in xylene at 92 °C, up to high conversion. The influence of polymerization conditions on additive composition and properties, and their effect on the pour point and rheological properties of crude oil samples from the fields of ?tevkovica, Obod and ?eletovci located in the northern Croatia were studied. Additive efficiency was dominantly influenced by the alkyl acrylate chain length. The influence of component with carboxyl functional group or heterocyclic-nitrogen compound on additive quality was less obvious. Additive efficiency significantly depended on the properties of crude oil, and n-paraffin content and distribution. The main advantage of the process is that additives can be directly used without purification.     

Synthesis and micelle behavior of (PNIPAm-PtBA-PNIPAm)m amphiphilic multiblock copolymer

A linear amphiphilic multiblock copolymer (PNIPAm-PtBA-PNIPAm)_m was successfully synthesized by a two-step reversible addition-fragmentation transfer (RAFT) polymerization in the presence of a cyclic trithiocarbonate as RAFT agent. The micelle behavior of (PNIPAm-PtBA-PNIPAm)_m multiblock copolymer in aqueous solution was then investigated by means of normal TEM, cryo-TEM, static and dynamic light scattering. The morphology, size, and size distribution of (PNIPAm-PtBA-PNIPAm)_m micelles were found to be dependent on the initial concentration of multiblock copolymer in THF. Spherical micelles, associated aggregates of spherical micelles, cage-like micelles, layered structures, and vesicular micelles were experimentally observed, which were in good agreement with the prediction of theory and simulations on linear amphiphilic multiblock copolymer in selective solvent. The (PNIPAm-PtBA-PNIPAm)_m micelles also exhibit thermo-sensitive behavior in aqueous solution because of the PNIPAm blocks.