Ethanol-water Solvent Mixtures Research Articles

Improvement of mechanical properties and water resistance of bio-based thermal insulation material via silane treatment

Buildings, whether commercial or residential, consume a huge proportion of the energy produced globally to maintain livable conditions within their walls. It is estimated that 40% of the energy produced is devoted for buildings, which represents around 30% of global CO2 emissions. Most of buildings are equipped with heat insulation materials to reduce the energy loss and help in maintaining the desired conditions. However, most of these heat insulators are derived from fossil fuel or have environmental and safety concerns. Herein, the effect of two different silane treatments on enhancing the compatibility between date palm wood fibers (DPWF) and polylactic acid (PLA) to produce green biodegradable composites was investigated. The composites were fabricated for the use of heat insulation panels in construction, with filler percentage ranging from 0 to 40 wt%. To the best of our knowledge, this is the first work that examines silane treatment on PLA-wood composites in heat insulation for construction and buildings. The DPWFs were treated with aminopropyl triethoxysilane (APTES) using two different solvents: acetone-water solvent mixture (SA), and ethanol-water solvent mixture (SE). The composites were examined to evaluate the effect of treatments on the physical, thermal, and mechanical properties. Furthermore, the composite structure was characterized by FTIR and SEM techniques. The mechanical properties and water resistance of treated composites showed tremendous improvements compared to untreated composites (PLA-UTDPWF). The 20 wt% composites tensile strength increased from 8.6 MPa for PLA-UTDPWF, to 16.5 and 22.4 MPa for PLA-SA and PLA-SE composites, respectively. Nevertheless, the thermal conductivity slightly increased upon fibers treatment, but remained in a low range of values that are appropriate for heat insulation, varying from 0.085 to 0.105 W/(m⋅K). Overall, the SE treatment achieved the best improvements by enhancing preferred features such as the mechanical strength and minimizing undesirable features such as water retention, while maintaining low thermal conductivity. The treatments helped in producing clean and biodegradable heat insulations.

Solubility of 4-Chloro-2,5-dimethoxynitrobenzene, 4-Chloro-2,5-dimethoxyaniline, and 2,5-Dimethoxyaniline in Binary and Pure Solvents: Determination and Modeling

Using the dynamic method over the temperature range of (277 to 340) K at atmosphere pressure, solubility of 4-chloro-2,5-dimethoxynitrobenzene (CDMB) and 4-chloro-2,5-dimethoxyaniline (CDMA) in methanol–water and ethanol–water solvent mixtures, where solute-free mass fraction of methanol and ethanol range from 0.2 to 0.8, and solubility of CDMB, CDMA, and 2,5-dimethoxyaniline (DMAn) in 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, and diethylene glycol have been investigated. In all solvents, there exists a direct relationship between solubility and temperature. In mixture solvents, the experimental data are correlated using the Wilson and the NRTL models. The solubility of CDMB and CDMA increases with the added amount of methanol or ethanol. In pure organic solvents, significant differences are discerned for the solubility of CDMB, CDMA, and DMAn, and data are correlated with the Wilson, the NRTL, the modified Apelblat, and the λh models. The solubility of DMAn is strongly dependent on tempera...

Chiral Discrimination By Porphyrin Supramolecular Aggregates Based Chemical Sensors

The study of the formation of porphyrin aggregates characterized by supramolecular chirality is an important issue amenable to wide applications. One approach to prepare these architectures takes advantage by the presence of chiral substituents on the periphery of the macrocycles acting as specific chiral effectors during the molecular recognition event. We have exploited a tetraphenylporphyrin bearing a peripheral proline group in ethanol–water solvent mixtures (Figure 1 a); the aggregation led to the formation of extended J-type aggregates, featuring supramolecular chirality. The aggregates have been grafted onto ZnO nanoparticles and then QMB sensor surfaces have been coated with a thick film of such hybrid materials. Sensing properties of such hybrid materials have been extensively studied and results show that they have promising features for the development of reliable and efficient sensors based on the implementation of large chiral surfaces. Figure 1

The role of ethanol-water solvent mixtures in N719 sensitization of electrodeposited ZnO nanorods

Water plays an important role in N719 sensitization of ZnO films for application as photoanodes in DSC devices. The role of water content in ethanolic N719 sensitization solutions was examined resorting to N719-solvent interaction studies based on Kamlet-Taft solvatochromic parameters. Results show that as the water content increases, solvent’s HBA ability decreases, hindering dye aggregation in solution and increasing the fraction of dye carboxylic groups available for anchorage onto the charged ZnO surface. The impact of dye-dye-solvent equilibria in solution on ZnO nanorod films sensitization and device behavior was evaluated. Devices assembled with films sensitized in N719 solutions containing equal parts of ethanol and water showed a twofold increase in short-circuit current densities when compared to those sensitized in ethanol only, despite exhibiting significantly less stained films. Data indicate that the presence of water in the sensitization solution reduces the amount of dye aggregates in solution and on the ZnO surface.

Preparation and Characterization of Cabamazepine Cocrystal in Polymer Solution.

In this study, we attempted to prepare carbamazepine (CBZ) cocrystal through the solution method in ethanol-water solvent mixture (volume ratio 1:1) and polyvinyl pyrrolidone (PVP) solution. Nicotinamide (NIC) and saccharin (SAC) were selected as cocrystal coformers. Cocrystal screening products were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Powder X-ray Diffraction (PXRD) techniques. Characterization results show that in ethanol-water solvent mixture, pure CBZ-NIC cocrystal can be prepared, while CBZ-SAC cocrystal cannot be obtained. The addition of PVP can inhibit CBZ-NIC cocrystal formation and facilitate CBZ-SAC cocrystal formation.

Shape Transition of TiO2 Nanocube to Nanospindle Embedded on Reduced Graphene Oxide with Enhanced Photocatalytic Activity

In this study, we report a facile synthetic route for the transition of anatase TiO2 nanocube to nanospindle with coexposed {001} and {101} facets on a reduced graphene oxide (rGO) platform. Initially, a TiO2 nanocubes/graphene oxide suspension in an ethanol–water solvent mixture was hydrothermally treated at 180 °C for various reaction durations to perform the in situ growth of TiO2 and simultaneous reduction of graphene oxide to rGO. All composites resulted in the formation of anatase TiO2 with a surface heterojunction formed by coexposed {101} and {001} facets embedded on an rGO sheet. Interestingly, it was observed that 4 h of hydrothermal treatment resulted in the formation of a TiO2 nanospindle with enhanced {001} high energy facet % embedded on an rGO sheet. The photocatalytic performance of the products was evaluated for the photodegradation of malachite green under simulated solar irradiation. All TiO2@ rGO composites exerted enhanced activity as compared to the native TiO2 cube owing to enhanced...

Impregnation of medicinal plant phytochemical compounds into silica and alginate aerogels

Herbal medicinal plants are important sources of bioactive, medicinal compounds. In this work, impregnation of phytol as a model compound and multicomponent Clinacanthus nutans (C. nutans) plant extracts into alginate and silica aerogels was investigated, applying two different methods: wet impregnation and supercritical impregnation. Two types of C. nutans extracts were prepared by microwave-assisted extraction (MAE) using either ethanol-water solvent mixtures or pure ethanol as solvent. The impregnated compounds were analyzed by Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and chromatography (HPLC and UPLC–MS/MS). Results showed that supercritical impregnation method yielded the highest loading content with silica aerogels, with a content of 30.1±0.6wt% of the model compound phytol, and 11.5±0.4 and 23.9±1.0wt% of the extracts obtained with ethanol/water and pure ethanol solvents, respectively. In the wet impregnation method, alginate aerogels exhibited higher loading than the silica aerogels regardless of their surface area properties, indicating that in this case other properties of carrier materials and the nature of compounds have a stronger influence on the compounds loading than the surface properties of the carrier. Impregnation in alginate aerogels yielded higher total phenols and flavonoids contents than in silica aerogels. Plasticized alginate biopolymer was formed when the supercritical impregnation was performed with excess of phytol at 200bar and 40°C, indicating that the swelling and/or plasticizing effect of SCCO2 was remarkable combined with the effect of excess solute. Release kinetics results indicate that the alginate aerogel impregnated with the extract obtained with pure ethanol is suitable for controlled drug release whereas the alginate aerogel impregnated with the ethanol/water extract is more appropriate for fast release purposes. The release kinetics results were fitted into several mathematical models: zero order, first order and Higuchi model, to evaluate the mechanism of the release. Results showed that diffusion and erosion and/or swelling control the release of extract from the aerogels.

Crystallizing Micronized Particles of a Poorly Water-Soluble Active Pharmaceutical Ingredient: Nucleation Enhancement by Polymeric Additives

Antisolvent precipitation aided by polymeric additives has increasingly been explored as a method to produce micron-sized/submicron particles of active pharmaceutical ingredients with low aqueous solubility—so as to enhance their dissolution rate and absorption efficiency. This work is aimed toward understanding the role of these additives in mediating crystal nucleation and the growth process. Nucleation kinetics of naproxen, a poorly water-soluble drug, from an ethanol–water solvent mixture at various solute concentrations and in the presence of additives such as polyvinylpyrolidone (PVP) and hydroxypropyl methyl cellulose (HPMC) was investigated. At a given supersaturation, the crystal nucleation rate was calculated from probability distribution of the induction times measured in stirred, small-volume batch solutions. The analysis revealed that PVP additive significantly promotes the nucleation kinetics in the entire range of supersaturation examined, whereas the effect of HPMC on the nucleation kineti...

Schizophrenic thermoresponsive block copolymer micelles based on LCST and UCST behavior in ethanol–water mixtures

The development of responsive and multiresponsive polymers is gaining interest as they enable the development of more and more complex responsive materials. In this contribution, the synthesis and solubility behavior of well-defined poly(methyl acrylate) (PMA) and poly(diethylene glycol ethyl ether acrylate) (PDEGEA) homopolymers as well as PMA-block-PDEGEA block copolymers is reported. At first, a solubility screening of the homopolymers in ethanol–water solvent mixtures was performed in a high-throughput experimentation (HTE) manner using parallel turbidimetry, which revealed that in 35wt% ethanol PMA undergoes an upper critical solution temperature (UCST) phase transition while PDEGEA undergoes a lower critical solution temperature phase transition in this solvent mixture. Moreover, the thermoresponsive self-assembly of PMA-b-PDEGEA block copolymers in water and ethanol were investigated by turbidimetry and DLS revealing UCST-induced disassembly of the micelles in ethanol and LCST-induced clustering of the micelles in water. Finally schizophrenic behavior of the PMA-b-PDEGEA block copolymers in 35wt% ethanol is demonstrated.

Thermodynamic Analysis of Dissociation Functions of Valine at 293.15–318.15 K in Ethanol–Water Mixtures

Thermodynamic constants for dissociation of valine’s carboxylic, K 1, and amino groups, K 2, and standard thermodynamic potentials of dissociation of valine in ethanol–water solvent mixtures (0, 20, 40, 60, 80 wt%) have been determined by a potentiometric method in galvanic cells without liquid junction at 293.15–318.15 K (with temperature steps of 5 K). The short-range interaction part of dissociation Gibbs energy has been obtained. Individual ion contributions of the deprotonated and protonated forms of this amino acid have been evaluated. A correlative analysis of parameters of water–methanol, water–ethanol, water–propan-2-ol solvents on the strength of valine’s carboxylic and amino groups has been made.

UV-tunable upper critical solution temperature behavior of azobenzene containing poly(methyl methacrylate) in aqueous ethanol

A series of azobenzene containing copolymers were synthesized by post-modification of poly(methyl methacrylate-co-pentafluorophenyl methacrylate) with an amine-functionalized azobenzene. Light- and thermo-responsive behavior of these copolymers was investigated in ethanol–water solvent mixtures with various amounts of ethanol. The upper critical solution temperature (UCST) of the polymer solutions, resulting from the poly(methyl methacrylate), was found to be highly tunable by the substitution degree of the copolymers as well as the ethanol content of the solvent mixture. In addition, the copolymers are light responsive based on the cis–trans isomerization of the azobenzene group under UV irradiation. The cloud point temperatures (TCP) of the polymer solutions decreased after UV-irradiation due to the higher dipole moment of the cis-isomer of the azobenzene moiety leading to better solubility in ethanol–water solvent mixtures. Furthermore, the UV responsiveness was found to strongly depend on the solvent composition, revealing a higher decrease in cloud point after UV-irradiation in ethanol–water solvent mixture with higher water content. To the best of our knowledge, this is the first reported dual responsive polymer that combines light responsiveness with UCST behavior in aqueous solvent mixtures.

Enhanced Selectivity for the Hydrolysis of Block Copoly(2‐oxazoline)s in Ethanol–Water Resulting in Linear Poly(ethylene imine) Copolymers

The ability of merging the properties of poly(2-oxazoline)s and poly(ethylene imine) is of high interest for various biomedical applications, including gene delivery, biosensors, and switchable surfaces and nanoparticles. In the present research, a methodology for the controlled and selective hydrolysis of (co)poly(2-oxazoline)s is developed in an ethanol-water solvent mixture, opening the path toward a wide range of block poly(2-oxazoline-co-ethylene imine) (POx-PEI) copolymers with tunable properties. The unexpected influence of the selected ethanol-water binary solvent mixture on the hydrolysis kinetics and selectivity is highlighted in the pursue of well-defined POx-PEI block copolymers.

Formation of Diazepam–Lanthanides(III) Complexes in the 50–50 Volume % Ethanol–Water Solvent System and Study of the Effect of Temperature on the Complex Formation Constants

Diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) is an important derivative of the 1,4-benzodiazepine compound commercially distributed as Valium. The complex formation constants of diazepam with some light lanthanide(III) metal ions have been studied by potentiometric measurements. All titrations were performed in 50–50% (volume/volume) ethanol–water solvent mixtures at constant ionic strength (0.10 mol⋅dm−3). The ionic strength was maintained by using sodium perchlorate. The complex formation constants were determined at 25.00, 35.00 and 45.00 °C. With increasing temperature, a decrease was observed in the protonation constant (pK) of diazepam.

Fine tuning of the metal–organic framework Cu3(BTC)2 HKUST-1 crystal size in the 100 nm to 5 micron range

Cu3(BTC)2 (BTC = 1,3,5-benzene tricarboxylate) was synthesized from cooled reagents in ethanol–water solvent mixtures and in ethanol solvent at room temperature involving quenching at −196 °C and freeze drying in order to limit crystal growth. These approaches are handy to synthesize this MOF with narrow particle size distribution in the range of 100 nm to 5 microns and to achieve excellent crystallinity and unprecedented porosity. The nano-version of Cu3(BTC)2 outperforms micron size crystals in catalyzing methanolysis of styrene oxide.

Self‐Assembly of Poly(2‐alkyl‐2‐oxazoline)s by Crystallization in Ethanol–Water Mixtures Below the Upper Critical Solution Temperature

Crystallization of poly(2-isobutyl-2-oxazoline) and poly(2-nonyl-2-oxazoline) is found to occur by room temperature annealing below the upper critical solution temperature in ethanol-water solvent mixtures. Both polymers produce similar self-assembled structures (see image), resembling the previously reported crystalline hierarchical structures obtained from hot aqueous poly(2-isopropyl-2-oxazoline) solutions above the lower critical solution temperature. These observations suggest that the crystallization induced self-assembly process is a rather general phenomenon occurring for semicrystalline polymers in liquid-liquid two phase systems.

Upper critical solution temperature switchable micelles based on polystyrene‐block‐poly(methyl acrylate) block copolymers

AbstractThe solubility behavior of well‐defined poly(methyl acrylate) homopolymers as well as polystyrene‐block‐poly (methyl acrylate) block copolymers is discussed in this contribution. A solubility screening in ethanol–water solvent mixtures was performed in a high‐throughput manner using parallel turbidimetry revealing upper critical solution temperature behavior for poly(methyl acrylate). Moreover, the self‐assembly behavior of the block copolymers into micellar structures was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), andcryo‐TEM revealing upper critical solution temperature switchability of the micelles, which was evaluated by DLS at different temperatures. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis and characterization of porous poly(N‐isopropylacrylamide) hydrogels prepared in ethanol–water mixtures

AbstractPoly(N‐isopropylacrylamide) (PNIPAM) hydrogels were prepared by free‐radical polymerization in different ethanol–water mixtures. A scanning electron microscopy study revealed that the resulting hydrogels were macroporous. The swelling ratios of the resultant hydrogels in water at 20°C followed this order: X0.34 ≈ X0.68 > X0.48 > X0.09 > X0.04 > X0, where Xa denotes a gel prepared in an ethanol–water solvent mixture with an ethanol molar fraction of a. Below the lower critical solution temperature, the swelling ratio values of all of the hydrogels gradually decreased with increasing temperature. The complete collapse of the PNIPAM chain of all of these gels occurred at about 38°C, whereas the same was observed at about 35°C for the conventional gel prepared in water. The swelling ratio values of all of the PNIPAM gels with different molar fractions of ethanol at 20°C passed through a minimum in the cononsolvency zone. The deswelling rates of the hydrogels decreased in the following order: X0.34 > X0.48 > X0.68 > X 0.09 > X0.04 > X0. The reswelling rates of these hydrogels decreased in the following order: X0 > X0.04 ≈ X0.48 > X0.09 ≈ X0.68 > X 0.34. The freeze‐drying process decreased the swelling ratios but increased the deswelling and reswelling properties of the PNIPAM gels. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Temperature Induced Solubility Transitions of Various Poly(2-oxazoline)s in Ethanol-Water Solvent Mixtures

The solution behavior of a series of poly(2-oxazoline)s with different side chains, namely methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, phenyl and benzyl, are reported in ethanol-water solvent mixtures based on turbidimetry investigations. The LCST transitions of poly(2-oxazoline)s with propyl side chains and the UCST transitions of the poly(2-oxazoline)s with more hydrophobic side chains are discussed in relation to the ethanol-water solvent composition and structure. The poly(2-alkyl-2-oxazoline)s with side chains longer than propyl only dissolved during the first heating run, which is discussed and correlated to the melting transition of the polymers.

A schizophrenic gradient copolymer: switching and reversing poly(2-oxazoline) micelles based on UCST and subtle solvent changes

The self-assembly of hydrophobic gradient copolymers of 2-nonyl-2-oxazoline and 2-phenyl-2-oxazoline in ethanol-water solvent mixtures is demonstrated to result in structures that respond to changes in temperature as well as subtle changes in the solvent composition leading to both switching and reversing of the formed micelles.

Determination of nucleation parameters and the solid liquid interfacial energy of the KCl‐ethanol‐water system

AbstractThe kinetic parameters of homogeneous nucleation of KCl in different ethanol‐water solvent mixtures were determined at 25°C from the experimental measurements of the width of the metastable zone at different cooling rates. The ethanol mass ratio in the ethanol water solvent mixture was varied from 0‐0.9 and the metastable zone width for each solvent mixture was measured under the cooling rates of 10, 20 and 30 K/h. The influence of ethanol ratio on the activity coefficient was calculated. It was found that increasing the ethanol ratio in the solvent mixture leads to an increase in the mean molal activity coefficient. The experimental results obtained showed that the increase in the ethanol ratio in the solvent widens the metastable zone for the crystallization of KCl. Also it has inferred from the calculations based on the classical nucleation theory that increasing of the ethanol ratio in the solvent mixture resulted in an increase of the nucleation rate order, increase of the critical size of nuclei and increase of the solid liquid interfacial energy. It has been found that the solid liquid interfacial energy can be good correlated with inversely proportionality to the solubility. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)