Adsorption of nile red by poly(N‐isopropylacrylamide) gels in binary water/tetrahydrofuran mixtures

The adsorption of Nile Red by poly(N‐isopropylacrylamide) (PNIPAM) gels in binary water/tetrahydrofuran solutions was investigated using absorption spectrophotometry as a function of the volume fraction of THF, φ. Due to the cononsolvency abilities of such binary solvent mixtures, deswelling of the PNIPAM gels is observed in water‐rich mixtures, 0 ≤ φ ≤ 0.6, while the gels reswell for φ > 0.6. The position of the absorption band of Nile Red before and after equilibration with the PNIPAM gels indicates that the composition of the external solvent mixture is not practically influenced by the swelling process. On the other hand, it is found that the gels can effectively adsorb Nile Red in water‐rich mixtures (φ < 0.6), whereas no significant adsorption was observed in tetrahydrofuran‐rich mixtures. In fact, about 80% of the dye is adsorbed by the PNIPAM gels, at φ = 0.2. Under these conditions, the rather shrunk PNIPAM gel offers a more convenient less polar environment for Nile Red than the water‐rich bulk solvent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Molecular Simulation‐Assisted Solvent Selection for Separation of 1,2,4‐Trimethylbenzene

Extractive distillation is an alternative for processes where normal distillation is difficult, such as separation of close‐boiling mixtures, but solvent selection for distillation is laborious, and its selection pool is narrow. An innovative selection process using molecular simulation is proposed, and the performance of the selected solvent, 1,2,4‐trichlorobenzene, for the separation of 1,2,4‐trimethylbenzene from a C9 mixture is reviewed. The proposed process requires less investment and leads to lower operating expenses than the conventional two‐column process. The computed vapor‐liquid equilibrium determined from the molecular simulation is close to the HYSYS estimation in two ternary systems.     

The Meyer‐Neldel rule in layered silicone‐silver nanocomposites

X‐Ray diffraction and X‐ray photoelectron spectroscopy studies, applied on some silicone‐silver nanocomposites, revealed the influence of the solvent used in preparation on the morphology of the resulted materials. It has been emphasized that dimethylformamide solvent favors the formation of silver nanoparticles and their migration at the surface, while water solvent favors the formation of a homogeneous composite with small silver nanoparticles. The places occupied by Ag nanoparticles (some prevent their oxidation and others that favor the oxidation process) are dependent on the mixture used in sol‐gel technique and have influence on the nanocomposite electrical conductivity. The temperature dependence of the electrical conductivity is investigated. A linear relationship between the pre‐exponential factor (σ₀) and activation energy (E_a) was observed, in the high temperature range (T > 315 K), for all the samples, indicating that the conductivity data obey Meyer‐Neldel rule. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Modeling of asphaltene and water associations in petroleum reservoir fluids using cubic‐plus‐association EOS

Asphaltene is a group of complex compounds commonly present in petroleum reservoir fluids. It is conceivable that asphaltenes strongly interact with water through hydrogen bonding, affecting phase behavior of water/oil mixtures with/without forming an asphaltene‐rich phase. In this research, the cubic‐plus‐association equation of state (CPA EOS) is applied to multiphase behavior resulting from self‐ and cross‐associations of asphaltenes and water in petroleum fluids. This article also presents a new correlation for binary interaction parameters for water with n‐alkanes for the CPA EOS by using three‐phase data for water/n‐alkane binaries. A method is proposed to characterize mixtures of asphaltene‐containing oil with water using the CPA EOS. Results show that the CPA EOS can represent multiphase behavior for water/oil mixtures with up to four equilibrium phases: asphaltene‐rich, solvent‐rich, aqueous, and vapor phases. Case studies include bitumen/water mixtures, involving asphaltene‐water emulsion, water solution in bitumen, and their continuous transition with varying temperature. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3429–3442, 2018     

Volume phase transition of a polymer gel induced by phase separation of mixed solvents of water and 2‐butoxyethanol

The occurrence of the volume phase transition triggered by the phase separation of mixed solvents is investigated using polyacrylamide gels in mixtures of water and 2‐butoxyethanol. When the water content of the mixtures is lower than that of the critical composition, the temperature‐dependent swelling curves show a steep change around the phase separation temperatures but remain continuous, although the solvent inside the gel undergoes a discontinuous composition change. This continuous change originates from the critical concentration fluctuation below the spinodal temperature. Hysteresis‐like behavior is also observed for the heating and cooling curves. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46366.     

Hydrogen bond‐mediated self‐assembly and supramolecular structures of diblock copolymer mixtures

This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self‐assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self‐assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry     

Influence of the Solvent Content on the Phase Transformation of Sulfadiazine N‐Methyl Pyrrolidone Solvate

The influence of the solvent content on the solution‐mediated phase transformation of sulfadiazine (SD) N‐methyl pyrrolidone (NMP) solvate into SD was investigated for process development. The solubility results of the NMP solvate and SD in NMP solvent/water mixtures supported by the analysis of solvent‐solvent interactions between NMP solvent molecules were used to understand and optimize the transformation of the NMP solvate into SD. Needle‐on‐rhombic‐like aggregated crystals and rod‐like single crystals of SD were obtained and reported for the first time. By combining Raman spectroscopy, focused‐beam reflectance measurements, and scanning electron microscopy, the phase transformation of NMP solvate into SD was tracked. Higher temperatures and stirring rates accelerate the transformation process and have a negative influence on the final SD product quality.     

Monitoring production process of cisplatin‐loaded PLGA nanoparticles by FT‐IR microspectroscopy and univariate data analysis

Cisplatin‐loaded PLGA nanoparticles for drug delivery have been prepared using a well‐established water/oil/water double emulsion‐solvent evaporation method. The production process has been monitored by using Fourier Transform Infrared (FT‐IR) microspectroscopy without using KBr tablets and any preliminary sample preparation. Significant spectra have been obtained for all chemical compounds and for samples at different steps of production process. The use of a linear or univariate approach using a R² determination coefficient has been proposed for discriminating among FT‐IR spectra even when small differences are present. The obtained results confirm that new geometries of data acquisition contribute to make infrared microspectroscopy a very useful tool for a rapid and detailed monitoring of production processes of pharmacological interest. Moreover, morphological and physiological characterizations have been performed on cisplatin‐loded samples showing results in good agreement with those reported in literature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41305.     

High performance liquid chromatography study of water‐soluble complexes and covalent conjugates of polyacrylic acid with bovine serum albumin

Polycomplex formation of bovine serum albumin (BSA) and polyacrylic acid (PAA) was studied by pH titration, fluorescence, and HPLC methods in water solutions. It was shown that the complex formation and the solubility (phase state) of the polycomplexes depended on pH of the solutions and ratio of the components. The stability of PAA‐BSA complexes was negligibly weak when pH = 6.0–7.0 [pH > pI (isoelectric pH)]. Stable water‐soluble polycomplexes formed at pH = pI (pH 5.0) in a wide range of n_BSA/n_PAA ratios (0.05–50) and coexisted with free protein molecules at the higher ratios of components. Existence of water‐soluble and insoluble PAA‐BSA complexes has been observed at pH ≤ 4.5. The soluble to insoluble state transition of polycomplexes has been confirmed and binding mode of polyelectrolytes to proteins was assumed dependent on the ratio of components as a result of formation of soluble polycomplexes, complex coacervation, or amorphous precipitates. Soluble complexes were formed as fully homogenized mixtures. Fraction composition of the mixtures and insoluble complexes depended on the protein/polymer ratio and over the critical protein/polymer ratio, the soluble polycomplexes coexisted with free BSA molecules. On the other hand, the comparision of covalent conjugate formation and complexation of PAA with BSA has been revealed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Self‐assembly of novel architectural nanohybrid multilayers and their selective separation of solvent‐water mixtures

A new architectural nanohybrid multilayer has been explored and built on various substrates. The building blocks of positive and negative charged polyelectrolyte‐coated nanoparticles (NPs) could be obtained by tuning the electrical properties of the amphoteric oxide NPs in acid and basic environments. The nanohybrid films were, thereafter, formed by layer‐by‐layer (LbL) assembly of polycation‐ and polyanion‐coated NPs. It was demonstrated that this approach could incorporate single component NPs into both polycation and polyanion layers, and in turn improve the NP loading, maintain good dispersion of NPs within the film. For separation applications, a dynamic LbL assembly was attempted as a means of fabricating such nanohybrid multilayers on both 2‐D and 3‐D polymeric porous substrates. The nanohybrid multilayer membrane renders both much higher selectivity and flux in the separation of solvent‐water mixtures. Moreover, such assembly of nanohybrid multilayers allows us to efficiently simplify the procedures by reducing 30–40‐fold process cycles. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Simultaneous lower and upper critical solution temperature‐type co‐nonsolvency behaviour exhibited in water–dioxane mixtures by linear copolymers and hydrogels containing N‐isopropylacrylamide and N,N‐dimethylacrylamide

The co‐nonsolvency behaviour in water–dioxane mixtures of linear copolymers and hydrogels consisting of N‐isopropylacrylamide (NIPAM) and N,N‐dimethylacrylamide (DMAM) was studied as a function of solvent composition and temperature. The composition of the copolymers, P(NIPAM‐co‐DMAMx), in DMAM units, x, varies from x = 0 up to x = 100%. It is shown that the copolymers combine the lower critical solution temperature (LCST)‐type co‐nonsolvency behaviour of poly‐NIPAM with the upper critical solution temperature (UCST)‐type co‐nonsolvency behaviour of poly‐DMAM. Depending on x, both the LCST‐ and UCST‐type co‐nonsolvency behaviour may be simultaneously observed in water‐rich and dioxane‐rich solvent mixtures, respectively. Due to this complex phase separation behaviour, the variation of the reduced viscosity of the linear copolymers, as well as the swelling–deswelling behaviour of the respective hydrogels, are shown to be temperature‐ and solvent‐sensitive. Copyright © 2006 Society of Chemical Industry     

Melt‐rheological behavior of high‐solid cement‐in‐polymer dispersions

The rheological behavior of a series of poly(ethylene oxide) melts containing nonhydrated cement is investigated using stress‐sweep measurements. The influence of the polymer end‐group—diol, monomethyl ether, and dimethyl ether—, molecular weight, and the particle volume fraction is examined. The data suggests that monomethyl ethers adsorb with their single OH group head‐on on the cement surface, which reduces the interparticle friction and the viscosity, but mixtures based on monomethyl ethers exhibit shear‐thickening behavior. The diols cause the formation of hydrogen‐bonded particle networks leading to high viscosities, but these mixtures exhibit shear‐thinning behavior due to the collapse of the network upon shearing. On increasing the particle volume fraction, the samples feature a nonlinear increase in viscosity. Fitting these data indicated that the maximum particle volume fraction is close to the random packing density of spheres and decreases with decreasing shear stress. As coating for glass rovings, the mixtures match the reinforcing performance of solvent‐based systems despite lower cement content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Extraction of lipids from a specialist dairy stream

In this work a process for the extraction of neutral and complex lipids from the specialist dairy stream ‘beta-serum’ is described. Beta-serum is a proprietary product obtained from dairy streams containing greater than 60% fat that have been through phase inversion from an oil-in-water to a water-in-oil emulsion. It is an enriched source of milk fat globular membrane proteins and complex lipids, and is distinct from buttermilk in this respect. In the process described here a total lipid extract could be obtained from liquid beta-serum using a continuous near-critical dimethyl ether (DME) antisolvent fractionation process. Protein and water are precipitated from solution when mixed with the DME, whilst lipid and some water are extracted into the DME-rich phase. The extraction yield of lipids depended on the solids content of the feed and the feed to DME flow ratio, but did not depend on the lactose content. Lipids were also extractable from spray dried beta-serum powder, but only when the lactose content had been reduced below 45% by mass. A two step extraction process is described in which neutral lipids are extracted with supercritical CO₂, and then polar lipids using near-critical DME. The polar lipid extract was enriched in phospholipids (∼70% by mass), which included phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin. Other complex lipid components extracted included gangliosides and cerebrosides. Unlike the antisolvent process, proteins were not denatured during either CO₂ or DME processing of the spray dried powders, and the de-fatted powders are therefore suitable for a range of functional foods. A polar lipid extract could also be produced from spray dried powder by extracting first with DME to obtain a mixed neutral/complex lipid extract, then re-extracting the lipid extract with CO₂ to remove neutral lipids.     

A Mathematical Approach to a More Accurate Determination of Critical Micelle Concentration and Other Thermodynamic Parameters of 14‐2‐14 Gemini Surfactant in Water–Organic Solvent Mixed Media at Variable Temperatures

To explore how the solvent characteristics influence the self‐aggregation of the cationic gemini surfactant dimethylene‐1,2‐bis(tetradecyldimethylammonium bromide) (14‐2‐14) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures in the presence of commonly used organic solvents; formamide (FA), acetonitrile (AN) and 2‐methoxyethanol (ME) in aqueous solutions at varying temperatures (298.15–323.15 K) and compositions. The procedure suggested by Carpena et al. has been utilized to analyze conductivity–concentration plots in order to obtain critical micelle concentration (CMC) and degree of counterion dissociation (α) of the micelles. This method provides more accurate results as compared to conventional treatments, and the experimental error for the evaluation of micellar parameters is reduced significantly. The results revealed that, although the process of micellization becomes less favorable with the increase in composition of FA, AN and ME in mixed systems, the increase in CMC at compositions lower than 20% (v/v) of the organic solvents is relatively less, indicating that water character is dominant in the bulk phase. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy–entropy compensation phenomenon has been observed for 14‐2‐14 in all the mixtures within the studied temperature range.     

Rapid detection of vegetable oils in milk fat by on‐line LC‐GC analysis of β‐sitosterol as marker

On‐line liquid chromatography‐gas chromatography (LC‐GC) has been applied to the detection of vegetable oils in milk fat using β‐sitosterol as marker. The method involves transesterification of the fat, pre‐separation of the sterol fraction from other lipid constituents and on‐line transfer to the capillary GC system. The on‐line approach avoids time‐consuming sample preparation steps prior to GC analysis. The suitability of this analytical approach was tested with model mixtures of milk fat with cotton and rapeseed oil. The method allows the detection of adulterations at low levels. Simultaneous quantification of cholesterol in milk fat is also possible. Considering the rapid sample preparation, the described method can be applied for screening of large sample numbers.     

Bioerodible hydrogels based on 2‐hydroxyethyl methacrylate: Synthesis and characterization

Biocompatible polymers with specific shape and tailored hydrogel properties were obtained by polymerization of mixtures of 2‐hydroxyethyl methacrylate (HEMA) with 1–8 wt % ethylene glycol dimethacrylate (EGDMA) or tetra(ethylene glycol) diacrylate (TEGDA) as crosslinking agents, by using a redox initiator. Introduction of charged positive and negative groups was easily achieved by direct polymerization of appropriate monomer mixtures and by chemical transformation of preformed hydrogels. Investigation of the swelling behavior of the prepared hydrogels evidenced an appreciable dependence on both solvent type and polymer chemical structure. Additionally, the solvation process resulted in being controlled by solvent diffusion, according to a Fickian II mechanism. The presence of several types of water with different melting behavior was observed in fully swollen hydrogels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2729–2741, 2002     

Fast synthesis of 1,3‐DAG by Lecitase® Ultra‐catalyzed esterification in solvent‐free system

Lecitase® Ultra, a phospholipase, was explored as an effective biocatalyst for direct esterification of glycerol with oleic acid to produce 1,3‐DAG. Experiments were carried out in batch mode, and optimal reaction conditions were evaluated. In comparison with several organic solvent mediums, the solvent‐free system was found to be more beneficial for this esterification reaction, which was further studied to investigate the reaction conditions including oleic acid/glycerol mole ratio, temperature, initial water content, enzyme load, and operating time. The results showed that Lecitase® Ultra catalyzed a fast synthesis of 1,3‐DAG by direct esterification in a solvent‐free medium. Under the optimal reaction conditions, a short reaction time 1.5 h was found to achieve the fatty acid esterification efficiency of 80.3 ± 1.2% and 1,3‐DAG content of 54.8 ± 1.6 wt% (lipid layer of reaction mixture mass). The reusability of Lecitase® Ultra was evaluated via recycling the excess glycerol layer in the reaction system. DAG in the upper lipid layer of reaction mixture was purified by molecular distillation and the 1,3‐DAG‐enriched oil with a purity of about 75 wt% was obtained. Practical applications: The new Lecitase® Ultra catalyzed process for production of 1,3‐DAG from glycerol and oleic acid described in this study provides several advantages over conventional methods including short reaction time, the absence of a solvents and a high product yield.     

Computer simulation and comparative study on the pervaporation separation characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) to separate aqueous mixtures of 1,4‐dioxane or tetrahydrofuran

A comparative study on the pervaporation separation has been attempted for water + 1,4‐dioxane and water + tetrahydrofuran mixtures using sodium alginate and blend membranes of sodium alginate with 5, 10, and 20 mass % of poly(vinyl alcohol). Pure sodium alginate membrane has a selectivity of 111 to water at 0.35‐mol fraction of water in the feed mixture containing 1,4‐dioxane while for water + tetrahydrofuran mixture, the membrane selectivity to water was 291 at 0.31‐mol fraction of water in the feed mixture. Pervaporation results have been discussed using the solution–diffusion principles. Arrhenius activation parameters for diffusion and permeation have been computed from the temperature‐dependent pervaporation results. Furthermore, experimental results have been analyzed using the complete mixing and plug flow models to compute membrane area as well as design parameters that are useful in scale‐up operations. The plug flow model is more appropriate than the complete mixing model to analyze the pervaporation results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1827–1840, 2004     

Pressurized Nozzle‐Based Solvent/Anti‐Solvent Process for Making Ultrafine ϵ‐CL‐20 Explosive

CL‐20 explosive is one of the most recent and powerful explosives. It has very high potential in futuristic applications but at present it has limitations of sensitivity to mechanical stimuli. Among the four different polymorphs (α, β, γ, and ϵ), ϵ‐polymorph has better stability and shock/detonics properties. However, preparation of pure ϵ‐polymorph is a challenging task particularly in terms of repeatability and polymorphism. In our research work, pressurized nozzle based solvent/anti‐solvent process (PNSAP) was developed for the preparation of ultrafine ϵ‐CL‐20 explosives with high repeatability, purity, and yield. To get ultrafine particle size, shape, distribution and yield, various process parameters/ variables such as solvent type, anti‐solvent type, dosing rate, stirring rate, ultra‐sonication, and temperature were identified and prioritized using the weighted average method of Analytical Network Process (ANP) techniques. It was observed that ultrafine ϵ‐CL‐20 particle size in the range of 2 to 3 μm can be obtained using this process. The ϵ‐polymorph was confirmed by FT‐IR characterization. The main feature of this PNSAP process is that it is a laboratory scale table‐top pilot plant which is simple, cost‐effective, safe and repeatable for continuous batch production of ultrafine ϵ‐CL‐20 at the rate of 100 grams per hour.     

Solubility of N‐Guanylurea Dinitramide in Binary Solvent Mixtures

The solubility of N‐guanylurea dinitramide (GUDN, Fox‐12) in binary solvent mixtures was measured. Binary solvents such as dimethyl sulfoxide (DMSO)/water and N,N‐dimethylacetamide (DMA)/water were investigated. The temperature was in the range of 0 °C to 70 °C for DMA‐water and 20 °C to 70 °C for DMSO‐water. The temperature dependence on the solubility was higher in DMA‐water than in DMSO‐water at the same fraction of water. On the other hand, the modeling data was obtained by using the Apelblat equation. The average relative errors are less than 3 %. Supersaturation for crystallization of GUDN in solution can be easily generated by adding water in DMSO (or DMA).