Effect of particulate filler on cell size in membranes formed via liquid–liquid thermally induced phase separation

This paper discusses the effects of adding particulate filler to a system undergoing liquid–liquid thermally induced phase separation (L–L TIPS). While much is known about the growth of droplets in L–L TIPS, little is known about the effect particular fillers have on droplet growth and the final cell size in the resulting microporous membranes. In this work, zeolite particles are shown to have a significant effect on the final cell size of these microporous membranes, the extent of which depends on the particle loading and processing conditions used to form the membrane. Two polymer–diluent–zeolite systems are reported: isotactic polypropylene–diphenyl ether and poly(methyl methacrylate)–cyclohexanol, both with zeolite 4A particles.     

The utility of sulfonic acid catalysts for silane water-crosslinked network formation in the ethylene–propylene copolymer system

Catalytic effects of Brönsted acid on the early kinetics of water-crosslinking reaction in the vinyltrimethoxysilane-grafted ethylene–propylene copolymer (EPR-g-VTMS) system were investigated by means of an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) technique and gel fraction measurements. Four sulfonic acids with different substituent, including methanesulfonic acid (C1SO₃H), 1-propanesulfonic acid (C3SO₃H), 1-pentanesulfonic acid (C5SO₃H), and dodecylbenzenesulfonic acid (C12PhSO₃H), were selected to examine the progress and effect of progressive changes in the silane water-crosslinked network structure in comparison with a primary amine (n-octadecylamine, Lewis base). From the kinetic analysis using Arrhenius equation, we found that the frequency factors for both hydrolysis (ATR-FTIR) and condensation step (gel content) of EPR-g-VTMS decreased in the order of C1SO₃H > C3SO₃H > C5SO₃H > C12PhSO₃H, while the activation energy values for each reaction did not differ significantly. These relationships can be explained mainly on the basis of the diffusion factors of the sulfonic acids in EPR-g-VTMS system. Moreover, the stress–strain curve comparison between water-crosslinked EPR-g-VTMS samples containing sulfonic acid and amine compound clearly indicated the difference in their tensile properties as a result of the catalyst variation; the use of sulfonic acid as water-crosslinking catalyst eventually achieves to the soft and tough water-crosslinked EPR-g-VTMS, while the hard and strong one was produced using amine catalyst. Not only the catalytic activity but also the type of the catalyst has eventually significant effects upon the physical properties of the water-crosslinked EPR-g-VTMS.     

Liquid–liquid phase separation in aqueous solutions of poly(ethylene glycol) methacrylate homopolymers

Here, the liquid–liquid phase separation (LLPS) in aqueous solutions containing poly(ethylene glycol) (PEG) methacrylate homopolymers is reported for the first time. In this study, the thermoresponse of concentrated solutions of DEGMA₆₀ (two ethylene glycol, EG, groups) TEGMA₇₁ (three EG groups), OEGMA300_x (4.5 in average EG groups) of varying molar masses (MM), and OEGMA500₂₈ (nine in average EG groups) is discussed. Interestingly, the temperature of LLPS (T_LLPS) is controlled by the length of the PEG side chain, the MM of the OEGMA300_x and the polymer concentration. More specifically, the transition temperature decreases with: (i) Decrease in the length of the PEG side chain, (ii) increase in MM of the OEGMA300_x, and increase in concentration. In addition, LLPS is also observed in mixtures of OEGMA300_x with Pluronic® F127. In conclusion, these systems present a thermally induced LLPS, with the transition temperature being finely tuned to room temperature when DEGMA is used. These systems find potential use in numerous applications, varying from purification to “water-in-water” emulsions.     

Platinum–cadmium electrocatalyst for ethylene glycol electrochemical reaction in perchloric acid electrolyte

The electrooxidation of ethylene glycol was studied using platinum–cadmium electrocatalysts supported on high surface area carbon Vulcan XC-72. This is the first instance of Cd being used as an electrocatalyst for glycol oxidation reaction. The catalysts were prepared with various Pt:Cd atomic ratios of 90:10, 80:20, and 70:30. All the catalysts prepared were synthesized by the alcohol reduction method with 20 wt.% metal on carbon. These materials were characterized morphologically by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) and electrochemically by cyclic voltammetry and chronoamperometry. The electrochemical measurements were carried out at 25, 35, 45, and 55 °C, and the products of the electrochemical reaction were monitored by high-performance liquid chromatography (HPLC). The XRD patterns of all the PtCd catalysts presented cubic face-centered structures, and TEM revealed a homogeneous particle distribution on the carbon support with low agglomeration. The average particle size was assumed to be the maximum of the Gaussian distribution curve of particle size, at close to 2.5 nm. The presence of Cd results in an improvement in the glycol oxidation reaction, as observed by cyclic voltammetry; linear sweep voltammetry shows a lower onset potential compared to that of pure platinum. At a constant potential of 0.50 V (vs. RHE) at ambient temperature, HPLC showed glycolaldehyde to be the main byproduct formed from ethylene glycol oxidation at potential constant of 0.50 V.     

Copolymer-grafted silica phase from a cation–anion monomer pair for enhanced separation in reversed-phase liquid chromatography

This work reports a new imidazolium and l-alanine derived copolymer-grafted silica stationary phase for ready separation of complex isomers using high-performance liquid chromatography (HPLC). For this purpose, 1-allyl-3-octadecylimidazolium bromide ([AyImC₁₈]Br) and N-acryloyl-l-alanine sodium salt ([AAL]Na) ionic liquids (IL) monomers were synthesized. Subsequently, the bromide counteranion was exchanged with the 2-(acrylamido)propanoate organic counteranion by reacting the [AyImC₁₈]Br with excess [AAL]Na in water. The obtained IL cation–anion monomer pair was then copolymerized on mercaptopropyl-modified silica (Sil-MPS) via a surface-initiated radical chain-transfer reaction. The selective retention behaviors of polycyclic aromatic hydrocarbons (PAHs), including some positional isomers, steroids, and nucleobases were investigated using the newly obtained Sil-poly(ImC₁₈-AAL), and octadecyl silylated silica (ODS) was used as the reference column. Interesting results were obtained for the separation of PAHs, steroids, and nucleobases with the new organic phase. The results showed that the Sil-poly(ImC₁₈-AAL) presented multiple noncovalent interactions, including hydrophobic, π–π, carbonyl–π, and ion–dipole interactions for the separation of PAHs and dipolar compounds. Only pure water was sufficient as the mobile phase for the separation of the nucleobases. Ten nucleosides and bases were separated, using only water as the mobile phase, within a very short time using the Sil-poly(ImC₁₈-AAL), which is otherwise difficult to achieve using conventional hydrophobic columns such as ODS. The combination of electrostatic and hydrophobic interactions are important for the effective separation of such basic compounds without the use of any organic additive as the eluent on the Sil-poly(ImC₁₈-AAL) column.

Thermal stability of phosphorus-containing styrene–acrylic copolymer and its fire retardant performance in waterborne intumescent coatings

Phosphorus-containing styrene–acrylic copolymers are synthesized by free radical seeded emulsion polymerization with the monomers of MMA/St/BA/MAA and phosphorus-containing vinyl monomer (SIPOMER PAM100). The properties of copolymer films are characterized by water adsorption test, thermogravimetry, Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS), etc. The copolymer emulsions are used as the binder in an intumescent coatings formulation, and the fire-retardant performances of the coatings are determined by an instrument which the furnace temperature is analoging the cellulose fire temperature. The water adsorption of copolymer film increases remarkably owing to the increasing of phosphoric acid group in the polymer chain. The thermal decomposition stability and thermal-oxidative decomposition stability of the copolymer are improved when PAM100 is introduced into its chain, which is strongly supported by the FTIR and EDS results of copolymer residual treated at different temperature. The EDS results also illustrate that the fire retardancy enhanced by PAM100 during combustion owing to the condensed-phase mechanism. The fire-retardant test results show that the intumescent coatings using StA-P_1.5 copolymer emulsion as the binder obtains the best fire retardant performance. We suggested that StA-P_1.5 presents the lower reactivity with the acid source (APP) in 275–400 °C, and the higher reactivity with APP when the temperature is greater than 500 °C would be benefit for the swelling–charring process and the final fire retardant performance. The exorbitant crosslinking in StA-P₇ brings a negative effect on the fire-retardant performance of intumescent coatings, even if it introduces a densy swollen char layer.     

Preparation of modified γ-alumina as stationary phase in gas–solid chromatography and its separation performance for hydrogen isotopes

On the basis of impregnation method, several stationary phases were prepared using γ-Al₂O₃ with the solution of transition metal salts and the breakthrough curves of gas chromatograph for H₂ isotopes were analyzed under the temperature of liquid nitrogen. The effects of carrier gas, flow rate and doping concentration on the separation performance for H₂ and D₂ were systematically investigated. The overall results showed that the surface areas and adsorptive capacities of modified γ-Al₂O₃ were slightly lower than unmodified one while the separation performance and symmetry of chromatographic peaks of the former were more excellent. In addition, the chromatographic peaks of ortho- and para-H₂ were no longer separated and the retention time shortened to half on columns of modified γ-Al₂O₃. All the magnetic transition metal ions modified γ-Al₂O₃ did very well for the separation of H₂/D₂ under the conditions of neon as carrier gas with a flow rate of 60 mL/min and column lengths of 1.0 m and injection amounts of 0.1 mL. Especially, the MnCl₂ modified γ-Al₂O₃ exhibited the best performance for separating H₂/D₂ with an optimum doping concentration of 20 wt%.     

Synthesis and surface properties of self-crosslinking core–shell acrylic copolymer emulsions containing fluorine/silicone in the shell

Stable emulsions of a core–shell acrylic copolymer (non-crosslinkable V0, and crosslinkable V2, V4, V6, and V8, where the numbers indicate the wt% of crosslinking agent based on the total acrylate monomer content) containing butyl acrylate (BA, 45 wt%), glycidyl methacrylate (GMA, 45 wt%), heptadecafluorodecyl methacrylate (PFA, 10 wt%), and various contents of crosslinking agent (vinyltriethoxysilane, VTES) were synthesized using a three-stage seeded emulsion polymerization process with a small amount of surfactant. The average particle size and viscosity of emulsions increased significantly with increasing VTES content. This study examined the effects of the VTES content on the surface/mechanical properties of self-crosslinked copolymer film samples containing a fixed acrylate monomer content to find the optimum VTES content. XPS showed that the film–air surface of the copolymer samples had a higher fluorine/silicone content than the film–dish interface. The tensile strength/modulus, thermal stability, and two Tgs (α and β Tgs) of the film samples increased significantly with increasing VTES content. The contact angle of the film samples increased with increasing VTES content up to approximately 6 wt%, and then decreased slightly. The optimum VTES content was approximately 6 wt% based on the total acrylate monomer content to obtain a high water/oil repellent coating material (V6) with the highest water/methylene iodide-contact angles (118.2°/81.8°) and lowest surface energy (18.4 mN/m).     

Developments in electrochemical processes for recycling lead–acid batteries

The lead–acid battery recycling industry is very well established, but the conventional pyrometallurgical processes are far from environmentally benign. Hence, recent developments of lead–acid battery recycling technologies have focused on low-temperature (electro)hydrometallurgical processes, the subject of this review, covering modified electrolytes, improved reaction engineering, better reactor design and control of operating conditions.     

Microencapsulated oleic–capric acid/hexadecane mixture as phase change material for thermal energy storage

Journal of Thermal Analysis and Calorimetry - Thermal energy storage systems provide efficiency in order to have better utilization of energy sources while protecting the environment. Thermal...     

Overcoming acid–base copolymer neutralization using mesoporous carbon and its catalytic activity in the tandem deacetalization–Knoevenagel condensation reaction

Research on Chemical Intermediates - Acid–base copolymer materials are of considerable interest because of their fundamental implications for acid–base bifunctional catalysis...     

Salicylaldoxime-functionalized poly(ethylene glycol)-grafted dicationic ionic liquid as a water-soluble and recyclable ligand for palladium-catalyzed Mizoroki–Heck reactions in aqueous phase

A water-soluble salicylaldoxime-functionalized poly(ethylene glycol)-grafted dicationic ionic liquid was successfully developed as an efficient ligand for palladium acetate-catalyzed Mizoroki–Heck reactions in water. A series of aryl bromides and terminal olefin were applied to this catalytic system and the corresponding coupling products were produced in high yields. The reusability tests demonstrated that the catalyst system could be recycled for six runs with only a slightly decreased activity.     

Rapid magnetic solid-phase extraction based on magnetite/silica/poly(methacrylic acid–co–ethylene glycol dimethacrylate) composite microspheres for the determination of sulfonamide in milk samples

A novel magnetic solid-phase extraction (MSPE) sorbent, magnetite/silica/poly (methacrylic acid–co-ethylene glycol dimethacrylate) (Fe₃O₄/SiO₂/P(MAA-co-EGDMA)), was developed. This MSPE material was prepared by distillation–precipitation polymerization of MAA and EGDMA in the presence of Fe₃O₄/SiO₂ microspheres with the surface containing abundant reactive double bonds. The resultant sorbent material was characterized by elemental analysis, electron microscopy, X-ray diffraction and Fourier-transformed infrared spectroscopy. In this work, eleven sulfonamides (SAs) were selected as model analytes to validate the extraction performance of this new MSPE sorbent. Noticeably, the extraction can be carried out quickly, the extraction time for the SAs onto Fe₃O₄/SiO₂/P(MAA-co-EGDMA) sorbent can be clearly shortened to 0.5 min. The desorption solution of SAs was analyzed by LC–MS/MS, and the results showed that the recoveries of these compounds were in the range of 87.6–115.6%, with relative standard deviations ranging between 0.9% and 10.8%; the limit of detection were in the range of 0.5–49.5 ng/L.     

Weak acid–base interaction induced assembly for the formation of rambutan-like poly(styrene-alt-maleic anhydride)/silica composite microspheres

To investigate the effect of surface functionality on the morphology of polymer/silica composite, poly(styrene-alt-maleic anhydride) (SMA) spheres prepared via precipitation polymerization method was employed. In water/ethanol solution, diethanolamine (DEA) was used to catalyze the hydrolysis reaction of tetraethoxysilane (TEOS), and rambutan-like poly(styrene-alt-maleic anhydride)/silica (SMA/SiO₂) microspheres were synthesized through in situ sol–gel process. The obtained structure and morphology were characterized by FTIR, NMR, TEM, SEM, and TGA. The results showed that the hydrolyzed SMA chains on the surface was crucial to the nucleation and growth of silica, and the morphologies of SMA/SiO₂ composite microspheres can be controlled by the amount of DEA and the ratio of SMA/TEOS. In addition, the SMA/SiO₂ microspheres were used to prepare hierarchical structure of SMA/SiO₂/Ag particles, which were utilized for the construction of surface-enhanced Raman scattering substrate (SERS).     

Effects of acrylic acid incorporation on the pressure–temperature behavior and the calorimetric properties of poly(N-isopropylacrylamide) in aqueous solutions

 We studied the effects of pH on the pressure–temperature dependence of coil–collapse transition for aqueous solutions of copolymers of N-isopropylacrylamide and acrylic acid (Ac). At low pressures, the transition temperature (T _tr) increased with pressure, but T _tr decrease with increasing pressure at pressures higher than 50–100 MPa. By increasing the pH, the transition contour shifted to a higher temperature. When the Ac content was increased, the effects of pH became more evident. From a calorimetric study at atmospheric pressure, ΔH _tr was found to become smaller by increasing the portion of the ionized residues in the copolymer. The ratio to the van't Hoff enthalpy changes became larger with an increase in pH, which indicated that the production of charge decreased the cooperative domain size. Received: 19 July 1999 /Accepted in revised form: 7 September 1999     

Combined scanning electrochemical microscopy–Langmuir trough technique for investigating phase transfer kinetics across liquid/liquid interfaces modified by a molecular monolayer

The first combination of scanning electrochemical microscopy (SECM) with a Langmuir trough for liquid/liquid interfaces is described. The technique has been examined and demonstrated through investigations of the effect of monolayers of l-α-phosphatidylcholine, distearoyl (DSPC) on the kinetics of oxygen transfer from decane to water. The stability of monolayers, formed in this way, on the timescale of SECM measurements has been identified as a function of compression speed and subphase composition. Monolayers were stable over a wide range of pressures and molecular areas, but at high compression a decrease in surface pressure with time was observed. This effect was attributed to desorption of the lipid from the interface. In this situation, it was possible to perform SECM measurements (tip-interface approach curves) rapidly under surface pressure control, without causing significant disturbance to the monolayer. DSPC had no detectable effect on the oxygen transfer kinetics when the monolayer was in the liquid-expanded phase, but in the liquid-condensed phase a significant decrease in the rate of oxygen transfer was observed.     

LC–MS methods combination for identification and quantification of trans-sinapoylquinic acid regioisomers in green coffee

The present study aims to both identify and quantify trans-sinapoylquinic acid (SiQA) regioisomers in green coffee by combined UHPLC-ESI-QqTOF-MS/MS and UHPLC-ESI-QqQ-MS/MS methods. Among the various mono-acyl chlorogenic acids found in green coffee, SiQA regioisomers are the least studied despite having been indicated as unique phytochemical markers of Coffea canephora (known as Robusta). The lack of commercially available authentic standards has been bypassed by resorting to the advantages offered by high-resolution LC–MS as far as the identification is concerned. SiQA regioisomers have been identified in several samples of Robusta and Coffea arabica (known as Arabica) commercial lots from different geographical origin and, for the first time, in different samples of coffee wild species (Coffea liberica and Coffea pseudozanguebariae). Quantification (total SiQA ranging from 3 to 5 mg/100 g) let to reconsider these chlorogenic acids as unique phytochemical markers of Robusta being present in the same quantity and distribution in C. liberica as well. Gardeniae Fructus samples (fruits of Gardenia jasminoides) have additionally been characterized as this matrix is recognized as one of the few naturally occurring SiQA sources. The SiQA regioisomer content (total SiQA about 80 mg/100 mg) fully supports the proposal to use this matrix as a surrogate standard for further studies.