Binary Solvent Systems Research Articles

Intercalation Behavior of a Spiro-bipyrrolidinium Cation into a Graphite Electrode from Dimethyl/Propylene Carbonates.

Quaternary ammonium-graphite intercalation compounds (QA+-GICs) are promising negative electrode materials in dual-carbon batteries by virtue of safety, low cost, and environmental friendliness. However, the intercalation behavior of QA+ into graphite electrodes in mixed solvents has never been reported. Herein, spiro-(1,1')-bipyrrolidinium tetrafluoroborate dissolved in a dimethyl/propylene carbonate (DMC/PC) binary solvent system was employed in graphite/activated carbon (AC) capacitors. The storage behavior of the spiro-(1,1')-bipyrrolidinium cation into graphite is very related to the solvent composition of the electrolyte solutions. In situ X-ray diffraction tests revealed that the graphite electrodes can form different QA+-GICs during cycling, which is a key factor influencing the electrochemical performance of graphite/AC capacitors. Besides, the reversible thickness change of graphite in graphite/AC capacitors with different electrolytes during the charge-discharge process was also addressed. These findings provide sound evidence for the co-intercalation of the solvent with the cation.

Environmentally stable and multi-functional conductive gelatin/PVA/black wattle bark tannin based organogel as strain, temperature and bioelectric sensor for multi-mode sensing

Conductive hydrogels are regarded as ideal candidates for the application of flexible sensors owing to their excellent flexibility, portability and conductivity. However, it is still challenging and meaningful to prepare multifunctional (self-healing, adhesion, anti-freezing, biocompatibility, antibacterial and conductivity properties) and multi-mode sensing hydrogel-based sensors. Herein, we developed an environmentally stable and multi-functional conductive organogel via dynamic crosslinks based on biomass materials gelatin, black wattle bark tannin and PVA in the propylene glycol/water binary solvent system. Thanks to the dynamic interactions in the system, the good mechanical strength and self-healing performance of the obtained organogel are simultaneously realized. Meanwhile, the organogel integrates many crucial properties such as adhesion, environmental stability (anti-freezing and water retention), biocompatibility, antibacterial behavior and conductivity capacity. Significantly, the organogel can be assembled as three-mode sensors for strain, bioelectricity and temperature sensing. This three-mode sensor can effectively monitor human health data, resulting in providing supplement human health information and conditions. This work displays an interesting approach to construct an intelligent multi-functional conductive biomass organogel based multi-mode flexible sensors.

The effect of water on the crystallization of phytosterols and phytostanols in organic solutions

Phytosterols (C29H50O), also known as plant sterols and stanols, are valuable biomolecules with a variety of applications in the pharma, food, and cosmetics industries. Phytosterols are typically manufactured from vegetable oil and tall oil feedstocks through a cooling crystallization process. Depending on the feedstock used, the composition regarding individual phytosterols and phytostanols (saturated analogs of phytosterols), also varies to a large extent. In the current research it was observed that by adding a small amount of water to the organic solvent [i.e., n(water)/n(acetone) of 0.17, n(water)/n(ethanol) of 0.13, and n(water)/n(ethyl acetate) of 0.10], the final phytosterol profile regarding phytosterol and phytostanol concentrations can be modified. This can be explained by the different solubility behavior of phytosterols and phytostanols in the studied solvent systems, based on experimental results obtained from transmissivity measurements. Phytostanols have surprisingly low solubility when compared to phytosterols in all the studied solvent systems. However, in the presence of water, phytosterol solubility decreased more compared to phytostanols. To the best of our knowledge, this is the first time that phytostanol solubility has been systematically studied. Moreover, phytosterol and phytostanol concentrations in a crystallized product with varying binary solvent systems containing water has not previously been reported. The measured experimental solubility data correlated well with the studied solubility models (van't Hoff, modified Apelblat, Buchowski-Ksiazaczak (λh), and polynomial equations). Understanding the solubility behavior of phytosterols and phytostanols allows to optimize the crystallization process itself toward a broader raw material selection, and better yield and quality in the production of phytosterols from plant-based raw materials. In addition, these findings can potentially be further utilized in phytosterol formulations for various applications.

Oiling out and solubility measurement, molecular simulation and thermodynamic properties of d-tagatose in four aqueous binary solvent systems at 283.15 to 323.15 K

Solubility of D-Tagatose in four aqueous binary solvent systems from 278.15 K to 323.15 K was determined using the anti-solvent assisted gravimetric method. The solubility increases with temperature in all four binary solvents, with water, a good solvent, exhibiting a similar trend. In addition, the dissolution process generally follows the ’like dissolves like’ rule. The study indicates that the oiling out occurs when water exhibits a high molar fraction in water + 1-propanol, and water + isopropanol. Furthermore, we study the charge of the molecule using the molecular electrostatic potential surface (MEPS), aiming to analyze the molecular interactions. Then, to explain the dissolution behaviors of D-tagatose, the radial distribution function (RDF) by molecular dynamics simulations (MD) revealed a strong correlation between solute–solvent interactions and solubility, with significant solvent–solvent interactions. The solubility data was correlated using the modified Apelblat equation, Van’t Hoff equation, λh equation, and Jouyban-Acree model, with demonstrating the high consistency in the data. Finally, the thermodynamic properties revealed that the dissolution process of D-Tagatose is endothermic, and entropy-driven based on all positive values for ΔsolHo, ΔsolSo, ΔsolGo.

Kinetic study on bimolecular photochemical quenching of tris(2,2'-bipyridyl)ruthenium(II) complex in water-ethylene glycol binary media.

The bimolecular photochemical quenching of the tris(2,2'-bipyridyl)ruthenium (II) complex by ferricyanide ions in water-ethylene glycol binary media was investigated using a spectrophotometric approach, as previously reported by our research group. Time-resolved spectroscopy revealed that dynamic photochemical quenching occurred via a diffusion-dominated pathway. The static quenching process was found to occur significantly when the concentration of ethylene glycol was greater than 40 wt%. The analysis of the Stern-Volmer plots revealed that the emitters and quenchers tended to show ionic associations in water-ethylene glycol compared to our previous results with a water-glycerol binary solvent system. This is attributed to hydrophobicity, which is consistent with pioneering works that report that the addition of ethylene glycol to pure water forms hydrophobic regions, leading to dehydration of the complex ions.

Solubility determination and thermodynamic modelling of verapamil hydrochloride in methanol-water binary solvent systems from 293.15 K to 323.15 K

Verapamil Hydrochloride is a key calcium channel blocker used to treat cardiovascular disorders and prevent cluster headaches by inhibiting calcium influx, thus improving cardiovascular health. The solubility of Verapamil Hydrochloride (VH) in methanol + water binary solvent systems were studied using a gravimetric method at temperatures from 293.15 K to 323.15 K under atmospheric pressure. The solubility increased with temperature and methanol content, with the highest mole fraction solubility at a 0.90 methanol mole fraction and the lowest at 0.10. Various models, including Apelblat, Van't Hoff, modified Jouyban–Acree, and CNIBS/R-K, were used to calculate theoretical solubility, with RAD and RMSD assessing the model accuracy. Thermodynamic analysis indicated that VH dissolution is endothermic and entropy-driven. This data is valuable for optimizing VH purification and crystallization processes in the pharmaceutical industry.

Lignin sulfonate induced ultrafast fabrication of polypyrrole-based conductive organohydrogel for high performance flexible strain and temperature sensor

The ultrafast preparation of electrically conductive hydrogels to endow high sensing performance and temperature tolerance remains a critical challenge. Herein, lignosulfonate sodium-templated polypyrrole (LS-PPy) nanofillers were rapidly introduced into polyacrylic acid (PAA) hydrogel through ultrafast free radical polymerization in a glycerol/water binary solvent system. The resultant LS-PPy/PAA electrically conductive organohydrogel possesses satisfactory mechanical performance (strength of 56 kPa at a tensile strain of 800 %), strong adhesion, and a desirable low freezing point (−35 °C). Furthermore, this organohydrogel exhibits high strain sensitivity (gauge factor = 2.65), fast response time (~160 ms), low signal hysteresis, and excellent cyclic stability (over 1200 cycles). And the wearable LS-PPy/PAA organohydrogel sensor could accurately and real-time monitor various intense or subtle human movements, such as joint bending, facial expression and hand writing. Besides, the developed LS-PPy/PAA temperature sensor can respond to environmental temperature variations over a wide range of −20–100 °C. High resolution of 0.5 °C with remarkable sensitivity (−0.80 %/°C and linearity of R2 = 0.99) and repeatability were achieved within 36.5–40 °C, which makes it suitable for human body temperature monitoring. All these results demonstrate the substantial prospective value of the LS-PPy/PAA hydrogel in wearable sensors and other associated fields.

One-pot preparation of strong, tough, frost-resistant and recyclable organohydrogels via Hofmeister effect and its application for electronic devices

Conductive hydrogels have shown a great potential in the field of flexible electronics. However, it is difficult to combine high strength and high toughness in conductive hydrogels prepared by conventional methods, which limits their applications in various fields. In this work, we pioneered a facile and cost-effective strategy to prepare soy protein isolate/poly(vinyl alcohol) (SPI/PVA) conductive hydrogels with high strength, toughness, low-temperature resistance, and recyclability by introducing all the salts into the prescuor solution directly. To solve the problem of unable to directly introducing high concentration Na3Cit into the soy protein isolate/PVA solution, MgCl2 was used to alleviate the strong salting-out effect of Na3Cit. Thus the stable SPI/PVA/EG/MgCl2/Na3Cit complex solution was obtained and the SPI/PVA/EG/MgCl2/Na3Cit (SPEMS) organohydrogel was prepared by the freezing/thawing process. The optimum tensile strength of the SPEMS organohydrogel was 1.1±0.07 MPa, and the elongation at break was 701.3±23.67 %, respectively. Meanwhile, the ionic conductivity of the organohydrogel was as high as 1.7±0.01 S/m. Finally, the EG/H2O binary solvent system endowed the organohydrogel with excellent low-temperature resistance (freezing point of −19.4 °C). The strain sensors assembled with SPEMS organohydrogels were characterized by high sensitivity (GF = 3.2, strain range from 20 %-500 %) and long-term stability. The flexible all-solid-state supercapacitor assembled with SPEMS organohydrogel as the electrolyte and activated carbon as the electrodes has a high area specific capacitance (113.76 mF/cm2) and good cycling stability (capacitance retention of 81.62 % after 1,000 charging and discharging cycles) at room temperature.

Lignin-modified cellulose nanofibers hydrogel under adjustable binary solvent systems with excellent adhesion, self-healing and anti-freeze properties

Hydrogels with remarkable flexibility have gained popularity as materials for current research. However, the unfavorable properties of short-term adhesion, susceptibility to damage, and freezing in low-temperature presented by conventional hydrogels have become bottlenecks for further applications. In this work, an anti-freezing hydrogel with excellent mechanical, adhesion, and self-healing properties were developed by constructing a persistent semiquinone/quinone-catechol redox equilibrium environment. The introduction of lignin-modified cellulose nanofibers (LCNFs) significantly improved the overall mechanical properties of the material, driven by strong hydrogen bond interactions. This enhancement was evident in the tensile properties (97.74 ± 1.72 kPa, 783 %) and compression properties (> 90 %). Within the internal network of the gel, the synergistic action of lignin and ammonium persulfate resulted in the production of catechol, which imparted the gel with excellent adhesion properties (28.26 ± 2.13 KPa) and broad adhesion applicability. In addition, the incorporation of ethylene glycol (EG) positively contributed to the strengthening of the gel while endowed with tunable anti-freezing properties. Given the exceptional advantages of the prepared hydrogels, they were used to assemble flexible strain sensors with outstanding sensitivity for monitoring human motions.

Few-layered graphene from cathodic exfoliation in binary solvents and application as a protective layer for lithium metal anodes

Electrochemical exfoliation is a top-down method recognized for its environmentally friendly and scalable approach for producing solution-processable graphene. Among its variation, cathodic exfoliation stands out for its potential in generating few-layer graphene with minimal defects. In this study, we developed a cathodic exfoliation method for graphite foil using a binary solvent system to produce graphene with a reduced number of layers. By employing a 0.1 M LiClO4 solution in a dimethyl sulfoxide and dimethyl carbonate solvents mixture at a 1:2 vol ratio, we enhanced the intercalation of solvated lithium ions into graphite, successfully exfoliating graphene with 5–6 layers. The exfoliated graphene exhibited a low defect density (ID/IG ∼0.05) and a C/O ratio of 33.2. Furthermore, when used as a coating on a separator, the exfoliated few-layered graphene (FLG) sheets demonstrated notable performance as a protective layer for Li metal anode in Li metal battery technology.

Optimization of solvent system for chitosan/polylactic acid/nanocellulose nanofibers using needleless electrospinning

AbstractNeedless electrospinning (NES) is the most advanced and robust method to generate biopolymeric nanofibers. NES overcomes the needle clogging and low throughput issues of conventional needle based electrospinning (ES). However, the issue with all ES techniques is the absence of generalized methods in the literature, and most of the work is being done empirically. The solvent system dictates the feasibility of the ES process, and solvent system based studies can help create more generalized ES methods. The current work provides a systematic approach to fabricating tribiopolymeric nanofibers. NES was used to fabricate chitosan (CS)/polylactic acid (PLA)/nanocellulose (NCC) based nanofibers by optimizing the solvent system using dichloromethane (DCM) and trifluoroacetic acid (TFA). Biopolymeric blend PLA/CS/NCC (10:0.1:0.05 w/v %) in various formulated solvent systems were made and analyzed for their physical properties (sedimentation rate, particle size, viscosity, and surface tension) and subjected to NES. The binary solvent system SS91 (DCM (90):TFA (10) %) showed the lowest sedimentation rate and viscosity while the highest particle size and surface tension, resulting in the beads free nanofibers. The viscosity and surface tension comparison were used to determine a critical point for the feasibility of nanofiber fabrication. Overall, the study showed a systematic approach for fabricating complex tri‐biopolymeric nanofibers in future.

Binary solvent-reinforced poly (vinyl alcohol)/sodium alginate double network hydrogel as a highly ion-conducting, resilient, and self-healing gel polymer electrolyte for flexible supercapacitors

We present a reliable approach for producing high-performance ion-conducting gel polymer electrolytes (GPEs) based on the sodium chloride (NaCl)-integrated dual network hydrogel of poly (vinyl alcohol)/sodium alginate (PVA/SA) using a binary solvent system of ethylene glycol (EG) and water, providing exceptional ionic conductivity, mechanical strength, and self-healing properties. Different GPEs were produced via the freezing-thawing method using different v/v% of EG and water (named PVA/SA/EG). The best PVA/SA/EG GPE provided a maximum ionic conductivity of 25 mS cm−1, astonishing mechanical strength of 0.42 MPa, exceptional stretchability of 462 %, and remarkable self-healing properties. The binary solvent system- and water-based GPEs were utilized in the construction of symmetric supercapacitors (SSCs) using carbon cloth electrodes and their electrochemical performance were compared. At a current density of 0.5 mA cm−2, the SSC prepared using the best PVA/SA/EG GPE demonstrated a high specific capacity of 577.21 mF cm−2, maintained 94.5 % capacitance after 5000 cycles at 1 mA cm−2, and provided an energy density of 80.14 mWh cm−2 while operating at a power density of 293.3 mW cm−2. The flexible SSC prepared based on this GPE demonstrated outstanding flexibility, while no significant decline in capacitive performance and ionic conductivity was detected when it was bent.

Solubility Reinforcement using Binary Solvent Mixtures and its use in Development and Validation of UV-Spectrophotometric Method for Posaconazole

Objectives: To develop a method that meets the requirements as per ICH guidelines for validation and can be used as simple, specific, economical, and repeatable for routine quality control analysis of formulations containing Posaconazole. Materials and Methods: The maximum absorbance of Posaconazole was successfully recorded using a precise 1:1 ratio of binary solvent system Methanol: Buffersolution pH 7.4 at 262nm. Results: After a preliminary physicochemical investigation the precipitation of the Posaconazole issue was resolved using a precise 1:1 ratio of binary solvent system Methanol: Buffersolution pH 7.4. Development and validation of the analytical method was done using the same binary solvent system. The maximum absorbance with this solvent system was found at 262nm, while the calibration curve shows a Regression coefficient (R2) of about 0.9984 for its linearity in the concentration range of 2.5 to 15µ/ml. The developed method was validated and meets the requirements as per ICH (International Conference for Harmonization) guidelines where the Limit of Detection (LOD) as well as Limit of Quantification (LOQ) were noted as 0.74µ/ml and 2.25µ/ml. Percentage recovery was within the permissible range (with a % relative standard deviation of less than 2.0). Conclusion: The results from validation parameters specifically accuracy or % recovery and robustness study reveal that the developed method meets the requirements and can be used as simple, specific, economical, and repeatable for routine quality control analysis of formulations containing Posaconazole.

Thermodynamic properties of β-HMX in binary mixed solvent systems and its microscopic mechanisms

Octogen (HMX) is the most powerful military explosive in current use. However, the unclear thermodynamic molecular mechanisms severely limit the development of its production process. In this paper, the solubility of β-HMX in three binary mixed solvent systems (acetone + ethanol, acetone + dichloromethane, acetone + toluene) was measured via a dynamic method at temperature ranging from 283.15 to 313.15 K under atmospheric pressure. The experimental results reveal that the solubility of β-HMX in these binary mixed solvent systems is positively correlated with acetone molar fraction and temperature, and the solvent composition has a greater impact on its solubility compared with the temperature. Moreover, the solubility of β-HMX is further correlated with the Van’t Hoff equation, modified Apelblat equation, CNIBS/R-K model, Jouyban-Acree-Van’t Hoff model, Jouyban-Acree-Apelblat model and NRTL model, and the modified Apelblat equation can give better fitting result (ARD = 8.101 × 10−3, RMSD = 1.065 × 10−5). Finally, the microscopic mechanism of the thermodynamic properties of β-HMX in binary mixed solvents is revealed by investigating the types, intensity and interaction sites of interactions based on density functional theory (DFT) and molecular dynamic (MD) simulation. The results demonstrate that both acetone molecules and ethanol molecules can form certain intermolecular interactions with β-HMX molecules, which are the main driving force of solubilization. In contrast, solvent–solvent interactions have an antagonistic effect on the solubility of β-HMX in mixed solvents. This work can further be informative for researchers in the field of energetic material for the solubility evaluations and provide a reference for the industrial production and performance enhancement of HMX in the future.

Preferential Solvation of Cyclosporin in Aqueous Mixtures of Some Polymeric Cosolvents

Background: Cyclosporin is a cyclic peptide-drug used as immunosuppressant for the prophylaxisof transplant rejection whose physicochemical properties in mixed aqueous solvent systems isstill not well understood. The preferential solvation parameters of cyclosporin in aqueous binarymixtures of diethylene glycol monoethyl ether (DEGME), polyethylene glycol 200 (PEG 200) andpolyethylene glycol 400 (PEG 400) were computed. Methods: Reported mole fraction solubilities of cyclosporin in DEGME-aqueous mixtures,PEG 200-aqueous mixtures, and PEG 400-aqueous mixtures were processed by following theinverse Kirkwood-Buff integrals (IKBI) method as suggested by Marcus and Ben-Naim using somethermodynamic parameters reported in the literature for these aqueous-polymeric mixtures at298.15 K. Results: It is observed that cyclosporin is sensitive to preferential solvation effects in theseaqueous-polymeric binary solvent systems. The preferential solvation parameter by DEGME (δx1,3)is negative in water-rich mixtures but positive in mixtures of 0.12<x1<1.00. It is conjecturablethat hydrophobic hydration around the non-polar methyl and methylene groups of this drug thatcould be present in water-rich mixtures can significantly impact the drug solvation. Otherwise,in mixtures of 0.12<x1<1.00 in DEGME-aqueous mixtures, as well as in almost all the mixtureswith PEGs, the preferential solvation by polymeric cosolvents could be due to the acidic behaviorof cyclosporin in front of ether and hydroxyl oxygen atoms of these polymeric cosolvents. Conclusion: Cyclosporin is preferentially solvated by the polymeric solvents in almost all thestudied mixtures of these aqueous-polymeric binary solvent systems.

Improving the efficiency of acidic eluents for elution of Scandium from Lewatit® VP OC 1026 and TP 272 solvent impregnated ion exchange resins

Scandium is a strategic element with exceptional applications however, its widespread application has been limited mainly due to its high price which itself originates from lack of enriched primary reserves. Mineralized waste materials and mine tailings collected from various mining activities often contain low amounts of Sc and rare earth elements (REE), along with much higher levels of contaminants such as Si, Fe and Al. Ion exchange resins, especially phosphorus containing solvent impregnated ones, show extremely high selectivity for quantitative adsorption of Sc from pregnant leach solutions. However, efficient and economical elution of Sc from these types of resins is still a challenge. In this study, a series of water miscible organic solvents including methanol, ethanol, 1-propanol, 2-propanol and acetone are explored with sulfuric acid in elution of Sc at room temperature (25 °C). With the proposed binary solvent system in this study, 98% of the adsorbed Sc was eluted from VP OC 1026 (impregnated with D2EHPA) with 4 M H2SO4 in 50 vol.% 1-propanol while negligible amount of Sc could be recovered with 2 M H2SO4 even at high temperatures. Also, exceeding 97% of the loaded Sc on TP 272 (impregnated with Cyanex 272) could be successfully eluted with 6 M H2SO4 containing 50 vol.% 2-Propanol. Nevertheless, the elution efficiency of Sc from TP 272 was notably constrained, falling below 20 %, when 2 M H2SO4 was employed as the eluent. The added organic solvents also significantly increased the performance of H2SO4 in elution of Sc from the resins in columns. The addition of just 10 vol.% 2-propanol to 2 M H2SO4 led to significant increase in the elution of Sc from TP 272. The maximum concentration of Sc in the eluted fractions increased by over threefold, going from 167.0 mg/L to 532.6 mg/L, when compared to using 2 M H2SO4 under similar elution conditions.

A “Hand‐In‐Hand” Thermal‐Responsive Cyclodextrin Material Designed for Liquid Smart Windows

AbstractThermochromic smart windows have emerged as a focal point in energy research. In this study, a novel approach is introduced for developing thermoresponsive materials for smart windows, utilizing microscopic agglomeration of molecules to regulate incident light. The groundbreaking material, β‐CD‐Val‐IBAm4, is constructed by grafting four isobutylated valines onto natural β‐cyclodextrins. This material exhibits a unique “hand‐in‐hand” effect, resulting from the interaction of isobutylated valine side chains, which leads to molecular aggregation and reduced light transmission at elevated temperatures. The hydration–dehydration process is related to molecular aggregation rather than crosslinking, ensuring the structural integrity and uniformity of the smart windows. Molecular dynamics simulations and 2D NOESY confirm the thermal response mechanism of β‐CD‐Val‐IBAm4. When dissolve in a glycerol‐water binary solvent system, the material forms a thermochromic liquid with outstanding optical performance (ΔTsol of 1 mm liquid can reach 69.8%) and long‐term stability. This innovative approach opens new avenues for the advancement of next‐generation smart window technologies.

Characterization Electrospun Nanofibers Based on Cellulose Triacetate Synthesized from Licorice Root Cellulose

Cellulose triacetate (CTA) nanofibers were formed by electrospinning using two binary solvent systems: methylene chloride/ethanol and chloroform/acetone. Previously, licorice root cellulose (LRC) with a degree of polymerization (DP) of 710 was extracted from licorice root waste by alkaline treatment and hydrogen peroxide bleaching at high temperatures. Then CTA with a degree of substitution (DS) of 2.9 and an average molecular weight of 175 kDa was synthesized from LRC using acetic acid and acetic anhydride, sulfuric acid was as a catalyst. The influence of the electrospinning process and various solvent systems on the morphology and structure of nanofibers is studied. The structure and morphology of the nanofibers were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and the sorption characteristics were also investigated. The results showed that the morphology and structure of nanofibers depended on the solvent mixture used. The average diameters of the CTA nanofibers with grooved morphology varied 200-700 nm (solvent methylene chloride/ethanol) and the dumbbell-shaped (flat ribbon) CTA nanofibers in a wide range from 200 nm to 4 mkm (solvent chloroform/acetone).

Fully Physically Crosslinked PNIPAM Ionogels with High Mechanical Properties and Temperature‐Managed Adhesion Achieved by H2O/Ionic Liquid Binary Solvents

AbstractPoly(N‐isopropylacrylamide) (PNIPAM) gels change their volume and hydrophilicity in response to temperature stimulus in flexible actuators, flexible sensors, and energy storage management. However, traditional PNIPAM gels exhibit low mechanical properties and poor self‐recovery ability due to weak intermolecular (chain) interactions and necessary covalent crosslinking. Herein, a water/ionic liquid (H2O/IL) binary solvent system that provides additional hydrogen bonding and hydrophobic interactions as well as can significantly increase the solubility (up to 60 wt.%) of NIPAM is developed. The fully physically crosslinked PNIPAM ionogel is prepared by utilizing the H2O/IL binary solvent and exhibited excellent mechanical performances, rapid self‐recovery properties, and strong adhesion strength. In addition, the lower critical solution temperature of the PNIPAM ionogel can also be tuned over a wide range (37‐70 °C) by adjusting the IL ratio in the binary solvent. Furthermore, based on the temperature sensitivity and ionic conductivity of the PNIPAM ionogel, applications of PNIPAM ionogels in smart devices, temperature‐managed adhesion, and flexible sensing are demonstrated, respectively. This work improves various performances of PNIPAM gels by using the H2O/IL binary solvent to adjust non‐covalent interactions and provided new ideas for developing high‐performance temperature‐sensitive gels.

Interaction between methyl red and cetyltrimethylammonium bromide under the influence of sodium polystyrene sulphonate in ethanol-water binary solvent systems: A spectrophotometric investigation

This research aims to comprehensively investigate and analyze the UV–visible spectroscopic behavior of the methyl red (MR)-cetyltrimethylammonium bromide (CTAB) system under the influence of sodium polystyrene sulfonate (NaPSS) in aqueous and different volume fractions (v.f.) of ethanol (EtOH)–H2O (0.1, 0.2, and 0.3) at 298.15 ± 0.2 K. In EtOH–H2O solvent systems, the triple interactions of dyes-surfactants-polyelectrolyte (DSP) complex systems are entirely novel. MR interacts with CTAB in NaPSS in the binary solvent media (0.1, 0.2, and 0.3 v.f. of EtOH–H2O) resulting in the formation of ion-pairs at very low CTAB concentrations, far below their apparent critical micelle concentration (CMC*) reducing the absorbance, and the new complexes above the CMC* due to solubilization of the MR into CTAB micelles observed by distinct spectral shifts. The CMC* values obtained from spectroscopic data increase in the order: (CMC*)water< (CMC*)0.1< (CMC*)0.2< (CMC*)0.3. This is because of the reduced polarity or dielectric constant and increased degree of water structure disruption around the hydrophobic chains of CTAB, where micelle formation occurs at somewhat higher concentrations. The Gibbs energy of micellization (ΔGmo) increases in the order: (ΔGmo=−16.89)water <(ΔGmo=−16.17)0.1<(ΔGmo=−15.62)0.2<(ΔGmo=−15.38)0.3, which further supports the inhibitory effect of increasing ethanol content towards micellization. In the post-micellar region, the decrease in hydrophobic interactions and an increase in electrostatic interactions lead to a rise in the overall binding constant value. This means that, when NaPSS is present, the stronger electrostatic interactions in the post-micellar region contribute significantly to the increased binding of CTAB micelles with MR. The tautomeric activity of MR and the solvent composition played a prime role in affecting the interaction mechanism, as evidenced by the blue and red spectral shifts.