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In the present study, we have investigated the effect of nature of surfactant, chain length and counter-ion on the mixed micellization behaviour ofvarious cationic surfactants, tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylammonium chloride (DTAC) and cationic gemini surfactant, bis(tetradecyldimethylammonium)hexane dibromide(C14-6-C14,2Br) with surface active ionic liquid (SAIL) tetradecylisoquinolinium bromide [C14iQuin][Br]. The interactions and mixed micellar behaviour of cationic surfactants and SAIL in aqueous medium have been studied by employing conductometry measurements and 1H NMR technique. The critical micelle concentration (cmc) and various thermodynamic parameters like standard Gibbs free energy of micellization (ΔGm0), change in standard enthalpy (ΔHm0) and entropy of micellization (ΔSm0) have been calculated from conductometry measurements. Mixed micellar parameters such as ideal cmc (cmc*), micellar mole fraction (X1m), micellar interaction parameter (βm) and activity coefficients, (f1 and f2) have been evaluated by applying Clint, Rubingh and Motomura theoretical models. Synergistic and non-ideal interactions have been found between SAIL and surfactants.

Here, the complex formation among anionic surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecylbenzenesulfonate [C4mim][DBS] and non-ionic polymer polyvinylpyrollidone (PVP) in aqueous solution has been studied. An attempt has been made to study the interactions in bulk and at interface via different techniques such as tensiometry, conductivity, dynamic light scattering (DLS) and nephelometric turbidity. From tensiometric measurements, some important surface parameters have been derived. From conductometric measurements, different thermodynamic parameters have been calculated and interpreted in terms of physicochemical interactions prevailing into the system. The aggregate formation has been tracked with DLS and nephelometric turbidity to understand the complexation dynamics.

Surface-active ionic liquids (SAILs) can modify the physiological properties of conventional surfactants. Mixed micelles of isoquinoline-based SAILs, dodecylisoquinolinium bromide [C12iQuin][Br], tetradecylisoquinolinium bromide [C14iQuin][Br] and cationic surfactant, dodecyltrimethylammonium bromide (DTAB) in aqueous medium and their interactions have been studied by employing conductometry and 1H NMR technique. The critical micelle concentration (cmc) and various thermodynamic parameters have been calculated from conductometry measurements. Mixed micellar parameters such as ideal cmc (cmc*), micellar mole fraction ( $$ {X}_1^m $$ ), micellar interaction parameter (βm) and activity coefficients (f1) and (f2) of component 1 (SAIL) and component 2 (DTAB) have been evaluated by applying Clint, Rubingh and Motomura theoretical models. The interaction between SAILs and surfactant has been found synergistic and non-ideal. The peak merging and broadening of protons suggests the growth of micelles. Use of SAILs as an additive effectively reduce the cmc that is indicated by negative value of interaction parameter (βm).

Two surface active ionic liquids (ILs) having 1-alkyl-3-methylimidazolium cationic moiety and dodecylbenzenesulfonate based anionic moiety i.e. [C5mim][DBS] and [C7mim][DBS], have been synthesized....

Densities and speeds of sound of l ‑glutamic acid and l ‑aspartic acid in aqueous and aqueous solution of 1-methylimidazolium chloride [mim][Cl] have been measured at T = (288.15, 298.15 and 308.15) K under atmospheric pressure. The apparent molar volumes (Vϕ), apparent molar volume at infinite dilution (Vϕ0), apparent molar isentropic compression (Kϕ, S) and the apparent molar isentropic compression at infinite dilution (Kϕ, S0) have also been computed from density and speed of sound data. Furthermore, limiting apparent molar expansion, Eϕ0, and hydration numbers, nH have been evaluated to support the conclusions obtained from the volumetric and acoustic studies. These parameters are helpful to study the structure nurturing, solvation behavior and various interactions present in the ternary solutions of (amino acid + [mim][Cl] + water).

The thermodynamics and interfacial behavior of the mixed micellization of a trisubstituted imidazolium based surface active ionic liquid (SAIL), 1-dodecyl-2,3-dimethylimidazolium chloride [C12bmim][Cl], with an antidepressant amphiphilic drug amitriptyline hydrochloride (AMT) have been studied by employing surface tension measurements at 298.15 K and from conductance at 288.15, 298.15 and 308.15 K. Critical micelle concentration (cmc), degree of ionization (α), and other thermodynamic parameters like Gibbs free energy of micellization (∆Gmic.°), standard enthalpy of micellization (∆Hmic.°) and standard entropy of micellization (∆Smic.°) were derived from conductivity measurements. The respective surface active parameters like surface tension at cmc (γcmc), minimum surface area per ionic liquid molecule (Amin), adsorption efficiency (pC20), maximum surface excess concentration (Гmax), effectiveness of surface tension reduction (Πcmc), and cmc of the mixed systems of SAIL and AMT have been cognized using surface tension measurements. The negative values of ∆Gmic.° and the standard Gibbs free energy of adsorption at the air/water interface (∆Gad.°) indicate the feasibility of the micellization behavior of the mixed systems and confirm the feasibility of drug-SAIL interactions. The micellar interaction parameter (βm) have also been analyzed to get detailed insights of the interactions between the amphiphilic drug and the SAIL by applying theoretical model introduced by Rubingh and Motomura. The negative value of this parameter indicates the presence of synergistic interactions of SAIL-AMT binary mixtures. A comparative study has been done between disubstituted and trisubstituted SAILs and it has been found that the surface activity of trisubstituted SAIL is better than their disubstituted analogue due to the high hydrophobicity and hydrophilicity of trisubstituted SAIL.

In this work, the effects on micellar behavior of long chain cationic surfactant tetradecyltrimethylammonium bromide (TTAB) upon the addition of trisubstituted ionic liquid (IL), 1, 2-dimet...

In this study, an understanding of interactions among the anionic surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecylbenzenesulfonate [C4mim][DBS] and non-ionic low molecular weight polymer polyethylene glycol 400 (PEG 400) in aqueous solution has been developed systematically. Various techniques such as tensiometry, conductivity, dynamic light scattering (DLS), nephelometric turbidity and rheology have been employed to understand the exquisite interplay of different competing mechanisms prevailing between these unlike molecules in bulk as well as in the interfacial region. Surface activity of the current systems at air-aqueous interface have been evaluated using by deriving various important surface parameters, such as surface excess concentration (Гmax), surface pressure at interface (Πcmc), minimum area occupied by one molecule of SAIL at air-solvent interface (Αmin), adsorption efficiency (pC20) and surface tension at critical micelle concentration (cmc) (γcmc). Also, the thermodynamic parameters such as standard free energy of micellization (ΔGm°), standard enthalpy of micellization (ΔHm°) and standard entropy of micellization (ΔSm°) have been evaluated from conductivity measurements. The process of micellization has been found to be exothermic and spontaneous thermodynamically in presence of PEG supported by gain in entropy. The values of critical micelle concentration (cmc) decrease with increase in concentration of PEG which signals towards the predominance of ion-dipole interactions as well as hydrophobic interactions. However, at the higher concentration (0.045 g/L PEG), the cmc has been found to increase due to modification in surface and bulk structure of system. These results have been confirmed by the electrical conductivity measurements. The aggregate formation has also been tracked with the help of dynamic light scattering and nephelometric turbidimetry which provides useful information regarding the complexation dynamics. The rheological measurements have been carried out with the intent of understanding the complex behavior of these SAIL-polymer systems.

In the present communication, the physicochemical properties between an anionic surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecyl sulfate [C4mim][C12SO4] and nonionic polymers poly(vinylpyrrolidone) (PVP)/poly(ethylene glycol) (PEG) have been investigated by conductance and surface tension measurements. From these measurements the critical aggregation concentration (cac), critical micelle concentration (cmc), and degree of ionization (α) have been estimated. To understand the aggregation and interfacial behaviour of [C4mim][C12SO4] towards PVP and PEG, various thermodynamic and surface parameters have also been derived and discussed. The results exhibit that [C4mim][C12SO4] interacts strongly with PVP as compared to PEG.

Thermodynamic and physicochemical properties of lysine and arginine in aqueous and aqueous solution of 1-heptyl-3-methyl imidazolium tetrafluoroborate [C7mim][BF4] have been studied by measuring density and speed of sound data at T = (288.15–308.15 K) under atmospheric pressure. The measured data has been further used to calculate limiting partial molar volume, V ϕ 0 , the limiting partial molar compression K ϕ , S 0 , and limiting partial molar volumes of transfer, Δ tr V ϕ 0 , and limiting partial molar isentropic compression of transfer Δ tr K ϕ , S 0 . Furthermore, structure making and structure breaking ability of solute has been discussed by evaluation of apparent molar expansivity, E ϕ 0 , Hepler's constant values, ∂ E ϕ 0 ∂ T P and hydration numbers, n H .

The complex formation of anionic copolymer poly(4-styrenesufonic acid-co-maleic acid) sodium salt (PSSA-co-MA) with surfactant tetradecyltrimethylammonium bromide (TTAB) and surface active ionic li...

The binding interactions of an anionic surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecylsulfate [C4mim][C12SO4] with cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDAC) in aqueous media have been critically assessed using multitechnique approaches, viz. conductometry, tensiometry, fluorimetry, dynamic light scattering, rheometry, and turbidity. A strong complex formation has been observed between PDAC and [C4mim][C12SO4] at the air-solution surface. At higher concentration of SAIL, [C4mim][C12SO4] interacts with PDAC to form [C4mim][C12SO4]-PDAC networks that precipitate out in bulk. The size determination measurements, i.e., DLS data, prove that the PDAC chains compress prior to the cmc and spread out after cmc due to interactions with SAIL. Fluorescence measurements endow aggregation number of SAIL with or without PDAC. The surface and thermodynamic parameters of micellization have been obtained for all the systems. This investigation gives information about the forces leading to the complexation between PDAC and [C4mim][C12SO4].

The mixed micellization behavior of surface active ionic liquids (SAILs), 1-dodecyl-3-methylimidazolium chloride, [C12mim][Cl], and 1-tetradecyl-3-methylimidazolium chloride, [C14mim][Cl] with an amphiphilic drug amitriptyline hydrochloride (AMT) have been studied using surface tension and conductance. Interfacial parameters obtained from surface tension were beneficial in deciphering the phenomenon taking place at the interface. Critical micelle concentration (cmc), and various thermodynamic parameters were achieved from conductance. The negative values of Δ G mic . ∘ and Δ G ad . ∘ indicate the feasibility of the mixed micellization process. Rubingh and Motomura introduced theoretical model for micellar interaction parameter ( β m ) have been examined to investigate the interactions between AMT and the SAILs.

Complex formation between the anesthetic drug, procaine hydrochloride and a surface active ionic liquid (SAIL), 1-tetradecyl-3-methylimidazolium chloride, [C14mim][Cl], in aqueous medium has been investigated using surface tension, fluorescence and DLS measurements at 298.15 K and conductance at 288.15, 298.15 and 308.15 K. Critical aggregation concentration (CAC), degree of ionization (α), and various thermodynamic parameters were determined using the conductivity measurements. The interfacial behavior of SAIL at different concentrations of the drug was evaluated from surface tension measurements by calculating a series of surface parameters and CAC values. Fluorescence spectroscopy was used to evaluate the binding constant (K) and the standard state Gibbs energy change (ΔG°) for the formation of drug–SAIL complexes, which confirms the existence of cation–π interactions between the drug molecules and imidazolium ring of the SAIL molecules. The CAC values were found to decrease with increase in the concentration of the drug, which is due to the balancing between hydrophobic and electrostatic interactions. Dynamic light scattering provides sufficient information about the size of the aggregates and the variation in the hydrodynamic diameters pertaining to the changes in the drug concentration. The results from above methods show that the aggregation process of SAIL is favored by increases in the concentration of the drug. It is demonstrated that with the better understanding of the interactions, [C14mim][Cl] can be judiciously utilized in making use of procaine hydrochloride.

The spectral characteristics of different drugs i.e. sulfanilamide, sulfanilic acid, sulfosalicylic acid dihydrate (SSAD) and sulfamethoxazole in aqueous α-cyclodextrin (CD) have been investigated at neutral pH. The formation of inclusion complexes of sulfa drugs with α-CD leads to the changes in fluorescence and absorption spectra which further enable the calculation of association constant of the bind processes by implementing the non-linear regression on the experimental data. The standard Gibbs energy ΔG was also calculated for the systems in which complex formation was observed. The α-CD study indicates that the sulpha drugs form 1:1 inclusion complex with α-CD.

Thermodynamic and spectroscopic properties of α-cyclodextrin and β-cyclodextrin in aqueous solution sulfathiazole have been investigated by volumetric, ultrasonic measurements at T = (288.15–308.15 K) along with absorption spectra and fluorescence studies. The apparent molar volumes at infinite dilution, V ϕ 0 and the apparent molar isentropic compression at infinite dilution K ϕ , S 0 , have been calculated from density and speed of sound data. Furthermore, partial molar volumes of transfer, Δ tr V ϕ 0 , partial molar isentropic compression of transfer, Δ tr K ϕ , S 0 , apparent molar expansivity, E ϕ 0 , Hepler’s constant values, ∂ E ϕ 0 ∂ T P and thermal expansion coefficient, α have also been evaluated to support the conclusions obtained from the volumetric and acoustic studies. These parameters are helpful to study the solvation behavior and various interactions present in the ternary solutions of (α-cyclodextrin/β-cyclodextrin + sulfathiazole + water). Further, absorption and emission spectra has been recorded for aqueous sulfathiazole solution in α-cyclodextrin to analyze the host-guest interactions. The inclusion complex of sulfathiazole with α-cyclodextrin is investigated by UV–visible spectroscopy and fluorescence. The study indicates that sulpha drug forms 1:1 inclusion complexes with α-cyclodextrin.

In the present study, we have reported a comprehensive assessment of interactional behavior between the surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecylbenzene sulfonate [C4mim][DBS] and cationic polyelectrolyte poly(diallyldimethylammonium chloride) [PDADMAC] solution in aqueous solution. Various techniques such as surface tension, isothermal titration calorimetry (ITC), conductivity, dynamic light scattering (DLS) and turbidity have been employed to get insight into interactions among [C4mim][DBS] and polyelectrolyte in the interfacial region. Then surface parameters such as surface excess concentration (Γcmc), surface pressure at interface (Πcmc), minimum area occupied by one molecule of SAIL at air-solvent interface (Αmin), adsorption efficiency (pc20) and surface tension at critical micelle concentration (cmc) (γcmc) have been calculated from tensiometric measurements. The values of cmc decrease with increase in concentration of polyelectrolyte indicating towards the predominance of electrostatic interactions except at intermediate concentration (0.01 g/L PDADMAC) for which hydrophobic interactions can be held responsible. The standard enthalpy of micellization (∆Hm°) has been obtained from ITC measurements. Further, thermodynamic parameters i.e. standard free energy of micellization (∆Gm°) and standard entropy of micellization (∆Sm°) have been evaluated from conductivity measurements. The size of complexes formed among [C4mim][DBS] and polyelectrolyte have been characterized using DLS and turbidity measurements. Overall, the electrostatic interactions play a major role among SAIL and polyelectrolyte which is generally expected from oppositely charged systems. The process of micellization has been found to be exothermic and spontaneous thermodynamically in presence of PDADMAC supported by gain in entropy.

Self-assembling and interactional behavior of a trisubstituted imidazolium based surface active ionic liquid (SAIL), 1-dodecyl-2,3-dimethylimidazolium chloride [C12bmim][Cl], with anesthetic drugs lidocaine hydrochloride (HCl) and procaine hydrochloride (HCl) have been screened using surface tension and fluorescence measurements at 298.15 K and from conductance at 288.15, 298.15 and 308.15 K. Critical aggregation concentration (CAC), ionization degree (α), and various thermodynamic parameters were achieved using conductivity measurements. The various associated interfacial parameters of IL at different compositions of the drugs have been evaluated using surface tension. A detailed analysis of the microenvironment of the aggregates and the size of the aggregates was done by using fluorescence spectroscopy technique. The CAC values decreases as the concentration of the drug increases, which is due to the balancing between hydrophobic and electrostatic interactions. This study confirms the presence of strong synergistic interactions between SAIL and drugs and formation of highly stable drug-SAIL complexes by a conjunction of hydrophobic, hydrophilic, electrostatic and cation-π interactions with 1:1 stoichiometry. A comparative study between disubstituted and trisubstituted SAILs with lidocaine HCl have also been discussed in this paper. Surface activity of trisubstituted SAIL has been found better than their disubstituted analogue due to the high hydrophobicity and hydrophilicity of the former.

In the present study, we have reported a detailed assessment of interactional behavior between the surface active ionic liquid (SAIL) lauryl isoquinolinium bromide ([C12iQuin][Br]) and anionic polyelectrolyte poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSS-co-MA) in aqueous media. Various techniques such as surface tension, conductance, dynamic light scattering, and turbidity have been employed to get insight into interactions among [C12iQuin][Br] and polyelectrolyte in the interfacial region. Then, surface parameters such as surface excess concentration (Γcmc), surface pressure at interface (Πcmc), minimum area occupied by one molecule of SAIL at air–solvent interface (Αmin), adsorption efficiency (pC20), and surface tension at critical micelle concentration (cmc) (γcmc) have been calculated from tensiometric measurements. Further, thermodynamic parameters, i.e., standard enthalpy of micellization $$ \left(\Delta {H}_{\mathrm{m}}^{{}^{\circ}}\right) $$ , standard free energy of micellization ( $$ \Delta {G}_{\mathrm{m}}^{{}^{\circ}} $$ ), and standard entropy of micellization ( $$ \Delta {S}_{\mathrm{m}}^{{}^{\circ}} $$ ) have been evaluated. The size and shape of complexes formed among [C12iQuin][Br] and polyelectrolyte have been characterized using DLS and turbidity measurements.

The micellization behaviour of biamphiphilic surface active ionic liquid (BAIL), 3-methyl-1-pentylimidazolium dodecylsulfate [C5mim][C12SO4] with anionic surfactant, sodium dioctylsulfosuccinate (AOT) was investigated using different techniques in an aqueous solution. The values of critical micelle concentration (cmc) and thermodynamic parameters have been ascertained by employing conductometric measurement at (298.15, 308.15 and 318.15) K. The interfacial parameters viz. surface pressure, maximum surface excess concentration, and minimum surface area per surfactant molecule evaluated by using the surface tension measurement at 298.15 K shows the less effectiveness of mixtures to reduce the surface tension. The size and turbidity of the mixed aggregates were investigated using dynamic light scattering (DLS) and turbidimetry. The turbidity results show the existence of micelles as well as mixed aggregates. Different proposed theoretical models like Clint, Rubingh and Motomura was employed for the evaluation of mixed micellar parameters (ideal values of cmc, activity coefficients of the components in the mixed micelle, and interaction parameters etc.) at different compositions. The existence of both the interactions (synergistic and antagonistic) has been inferred in the studied system. The mixed micelle formation was found dependent on micellar composition.

Aim of the present investigation is to broaden an understanding of the interactions between imidazolium based cationic surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide [C 12 mim][Br] and an anionic polyelectrolyte poly(4-styrenesufonic acid- co -maleic acid) sodium salt (PSSA-co-MA) in aqueous media by using fluorimetry, conductometry and tensiometry techniques. The various states of interaction and critical micelle concentration (cmc) have been reviewed due to the strong hydrophobic and electrostatic interactions. Also degree of ionization, α, cmc and various thermodynamic parameters were determined by conductivity measurement in the temperature range 298.15–318.15 K. The surface tension curve displays the presence of pronounced knap in the surface tension at SAIL concentrations below cmc of the SAIL. The various surface parameters are calculated from surface tension measurement. Aggregation number ( N agg ) and cmc were determined by fluorimetric measurements at temperature 298 K. In all cases it was observed that the cmc values were decreased with increase in the concentration of polyelectrolyte this is attributed to the strong electrostatic interactions between SAIL and polyelectrolyte. Also the aggregation behaviour of SAIL begins shifting from entropy-driven to enthalpy-driven with increasing the concentration of polyelectrolyte and increase in temperature. The results obtained from different measurements are in good agreement with each other.

The effect of addition of 3-methyl-1-pentylimidazolium tetrafluoroborate ([C5mim][BF4]) on the micellization of a nonionic surfactant, Triton X-100 (TX-100), has been investigated. The techniques employed to study the aggregation behavior are fluoremetry, dynamic light scattering (DLS), and transmission electron microscopy (TEM) and the concentration range covered is 0–2 wt% [C5mim][BF4]. The probes, viz. pyrene and pyrene-1-carboxaldehyde (PyCHO), have been used for fluorescence analysis. According to the findings, the addition of pentyl-chained ionic liquid (IL) to aqueous TX-100 results in a dramatic increase in critical micelle concentration (cmc) decrease in micellar size, and aggregation number pointing toward an overall “unfavorable” aggregation process.

Thermodynamic properties of l -threonine and l -valine in aqueous solution of 1-methyl-3-pentylimidazolium chloride, [C5mim][Cl] have been investigated by volumetric and ultrasonic properties at three different temperatures (T = (288.15, 298.15 and 308.15) K). Other properties at infinite dilution like apparent molar volume, Vϕ0 and the apparent molar isentropic compression Kϕ , S0, have also been calculated from the measured data. Conclusion drawn from volumetric and ultrasonic properties have been further supported by calculating apparent molar expansion, Eϕ0, Hepler's constant values, ∂ E ϕ 0 ∂ T P , hydration numbers, nH and specific volume, vϕ. The calculated parameters are worthwhile in studying structure nurturing, solvation as well as taste behavior on the basis of various kinds of interactions present in such solutions.

In the present study, we reported the effect of sodium carboxymethylcellulose (NaCMC), an anionic polyelectrolyte on the aggregation morphological variations of cationic surface active ionic liquids (SAILs) for example 1-tetradecyl-3-methylimidazolium bromide [C14mim][Br] and 1-hexadecyl-3-methylimidazolium bromide [C16mim][Br]. The measurements have been carried out by utilizing techniques such as surface tension, conductance, fluorescence, dynamic light scattering and rheology. The results obtained from surface tension measurements shows that surface properties and aggregation process of SAILs have been extensively influenced by the addition of polyelectrolyte. So, the humps have been observed in the tensiogram corresponding to different states of interaction. The various surface parameters such as surface excess concentration (Γmax), surface pressure at the interface (Πcmc), minimum area occupied by single SAIL molecule at air-solvent interface (Amin), adsorption efficiency (pC20) and surface tension at critical micelle concentration (cmc) (γcmc) have been calculated from surface tension measurements. The results obtained from tensiometric and conductometric measurements have been further confirmed by fluorescence, dynamic light scattering and rheology results. It has been observed that the cmc values of both the SAIL systems increases with increasing concentration of NaCMC.

The effect of hydrophilic ionic liquids (ILs), 1-butyl-2,3-dimethylimidazolium bromide [bdmim][Br] and 1-butyl-3-methylimidazolium bromide [bmim][Br] on the aggregation and surface active properties of non-ionic surfactant, Triton X-45 (TX-45) has been investigated in aqueous media. The surfactant properties such as critical micelle concentration (cmc), aggregation number (Nagg), surface and adsorption parameters were determined by surface tension and fluorescence techniques in TX-45 + IL/water systems. The cmc values were found to be varying at different wt% of IL than in water. The cmc value of TX-45 slightly decreases at lower (0.1) wt% of IL [bdmim][Br] in the medium. In general, with increasing concentration of both ILs in the solution the cmc of surfactant solution increases, thus the surface activity decreases. The surface activity is much lower in aqueous TX-45/IL than in water. The IL [bmim][Br] is found to increase the cmc of surfactant more rather than IL [bdmim][Br]. The aggregation number of aqueous TX-45 solution decreases with increase in wt% of IL. The hydrogen bonding interactions prevailed in presence of IL [bmim][Br] than IL [bdmim][Br], this led to better solubilisation of surfactant monomers in the former. It is demonstrated that ILs [bdmim][Br] and [bmim][Br] can be judiciously used at different wt% for modifying the aggregation properties of TX-45.

Densities and speeds of sound of glycine and glycyl dipeptide (glycylglycine) in aqueous 1-butyl-3 methylimidazolium bromide, [C4mim][Br] solutions have been measured at T = (288.15, 298.15 and 308.15) K. From the experimental data of density and speed of sound, the apparent molar volumes (Vϕ), apparent molar volumes at infinite dilution (Vϕ0), apparent molar isentropic compression (Kϕ , s) and apparent molar isentropic compression at infinite dilution (Kϕ , S0) have also been determined. Further, the partial molar volumes of transfer (ΔtrVϕ0) and partial molar isentropic compression of transfer (ΔtrKϕ , S0) of glycine and glycyl dipeptide from water to aqueous [C4mim][Br] solutions were calculated to enlighten the interactions such as solute–solute, solute–solvent and solvent–solvent present in these solutions. The apparent molar expansivity (Eϕ0), Hepler's constant values ∂ E ϕ 0 ∂ T P , thermal expansion coefficient (α) and hydration number (nH) have been evaluated to assist the interpretations earned from the volumetric and acoustic analysis. The Hepler's constant values were found negative for glycine and glycyl dipeptide at all concentrations of ionic liquid except at lower concentration with glycyl dipeptide. The negative sign indicates the co-solutes act a structure breaker.

The apparent molar volume and isentropic compression of glycylglycine in aqueous 1-methylimidazolium chloride, [mim][Cl], 1-ethyl-3-methylimidazolium chloride [C2mim][Cl], and 1-methyl-3-octylimidazolium chloride [C8mim][Cl] solutions have been calculated from the measured experimental data on density and speed of sound at temperature, T = 288.15, 298.15 and 308.15 K. The apparent molar volumes at infinite dilution, Vϕ0 and the apparent isentropic molar compression at infinite dilution Kϕ , S0, were also calculated. Furthermore, apparent specific volumes, apparent molar expansivity, Eϕ0, Hepler's constant values, ∂ E ϕ 0 ∂ T P and hydration numbers, nH, have been evaluated to support the conclusions obtained from the volumetric and acoustic studies. The Hepler's constant values were found negative which indicating the peptide under study is predominantly a structure breaker due to hydrophobic hydration of small peptide in aqueous ionic liquid.

Thermodynamic properties of glycine and its dipeptide diglycine in aqueous solution of 1-pentyl-3-methylimidazolium chloride, [C5mim][Cl] have been investigated by volumetric and ultrasonic properties at T = (288.15–308.15 K). The apparent molar volumes at infinite dilution, Vϕ0 and the apparent molar isentropic compression at infinite dilution Kϕ , S0, have been calculated from density and speed of sound data. Furthermore, apparent molar expansivity, Eϕ0, Hepler's constant values, ∂ E ϕ 0 ∂ T P and hydration numbers, nH have been evaluated to support the conclusions obtained from the volumetric and acoustic studies. These parameters are helpful to study the structure nurturing, solvation behavior and various interactions present in the ternary solutions of (amino acid/dipeptide + [C5mim][Cl] + water).

The influence of alkali salt [NaBr] on complex formation between anionic polyelectrolyte poly(sodium-4-styrenesulfonate) [NaPSS] and surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide [C 12 mim][Br] in aqueous media has been investigated by isothermal calorimetry, surface tension, fluorescence and 1 H NMR spectra. It was observed that the [C 12 mim][Br]-NaPSS complexes were effected markedly with the increased addition of salt. At lower concentration, NaBr smooth the path of formation of micelle-like aggregates between [C 12 mim][Br] and NaPSS above the critical aggregate surfactant concentration. But at high concentration of NaBr there is no [C 12 mim][Br]-NaPSS complex formation because of complete salt screening of the electrostatic attraction between NaPSS chains and the [C 12 mim][Br] micelles. A range of surface parameters akin as surface excess concentration (Γ cmc ), surface pressure at the interface (Π cmc ), minimum area occupied by single SAIL molecule at air-solvent interface (Α min ), the adsorption efficiency (pC 20 ) and surface tension at critical micelle concentration (cmc) ( γ cmc ) are calculated from surface tension measurement for both with and without NaBr. The aggregation number (N agg ) and cmc is also derived from fluorescence probe behavior and cmc obtained from all above techniques are in proper consent with each other. The interpretation of various inter-molecular interactions amid NaBr and molecules of [C 12 mim][Br] in 0.010 g/L NaPSS also have been investigated through 1 H NMR spectra.

Two surface active ionic liquids (ILs) having 1-alkyl-3-methylimidazolium cationic moiety and dodecylsulphate based anionic moiety, i.e. [C5mim][DS] and [C7mim][DS], have been synthesised. 1H-NMR, thin layer chromatography was done for their characterisation. The electrical conductivity and surface tension measurements were performed to investigate the interfacial and bulk properties of the aqueous solutions of different alkyl chain ionic liquids. These techniques were employed to study the aggregation behaviour in aqueous conditions. Various surface active parameters were evaluated at 298.15 K from the surface tension measurements. The lowest surface tension (γCMC.) and maximum surface excess concentration (τmax) values showed that [C7mim][DS] had the highest surface activity. Conductance measurements were performed at three rising temperatures (288.15, 298.15, and 308.15) K, and their thermodynamic parameters were calculated. It indicated that micellisation of both ionic liquids was entropy driven at all temperatures.

To study the molecular interactions between the ternary mixtures containing 1-heptyl-3-methyl imidazolium tetrafluoroborate [C7mim][BF4] as a common solvent with l-glutamic acid and l-aspartic acid respectively, densities and speed of sound have been measured at three different temperatures viz. T = 288.15 K, 298.15 K and 308.15 K under 0.1 MPa Pressure. The density and speed of sound data have been further utilized to calculate apparent molar volume and apparent molar isentropic compression. From the apparent molar volume and apparent molar isentropic compression, both properties at infinite dilution i.e. Vϕ0 and Kϕ,S0 have also been computed. To draw the conclusion from the volumetric and acoustic data, limiting apparent molar expansion Eϕ0, as well as hydration numbers, nH have been studied. It is quite worthwhile to study all of these derived or calculated parameters to perceive the solvation behavior, mixing aspects and various types of interactions born in the ternary solutions of (amino acid + [C7mim][BF4] + water) due to change in structure.

The application of aggregation behavior of a surface active ionic liquids (SAILs), 1-dodecyl-3-methylimidazolium chloride [C 12 mim][Cl] and 1-tetradecyl-3-methylimidazolium chloride [C 14 mim][Cl] in drug delivery of lidocaine hydrochloride has been investigated from surface tension and fluorescence measurements at 298.15 K and from conductance at 288.15, 298.15 and 308.15 K. Critical aggregation concentration ( CAC ), degree of ionization ( α ), and various thermodynamic parameters like Gibbs free energy of aggregation (∆ G agg . ° ) standard enthalpy of aggregation (∆ H agg . ° ) and standard entropy of aggregation (∆ S agg . ° ) are calculated using conductivity measurements. The surface activity of the ILs in various mixed solvents are examined from surface tension measurements by calculating various surface parameters like maximum surface excess concentration (Г max ), minimum surface area per ionic liquid molecule (A min ), adsorption efficiency (pC 20 ), effectiveness of surface tension reduction ( Π cac ) surface tension at CAC ( γ cac ), p (packing parameter), and CAC at different compositions. Fluorescence measurements have been employed to get detailed insight of the local microenvironment of the aggregates, and critical aggregation concentration ( CAC ). Decrease in the CAC values was observed with the increase in the amount of drug which is attributed to the balancing between electrostatic and hydrophobic interactions. This shows that the spontaneity of aggregation process of IL increases with the increase in the concentration of drug.

The effect of the hydrophilic ionic liquids (ILs) 1-butyl-2,3-dimethylimidazolium bromide [bdmim][Br] and 1-hexyl-2,3-dimethylimidazolium bromide [hdmim][Br] on the aggregation and surface active behaviour of the non-ionic surfactant Triton™ X-100 (TX-100) was studied in aqueous media. Several aggregation properties of TX-100 + IL/water systems, such as critical micelle concentration (CMC), surface active parameters, aggregation number (N agg) and aggregate size, were determined by surface tension, fluorescence and dynamic light scattering (DLS) techniques. It was found that the average micellar size and aggregation number decrease, whereas the CMC increases with increasing concentration of ILs. Interestingly, the CMC value of TX-100 is reduced slightly below 0.5 wt% of both the ILs in the medium. At higher wt% of IL in the system the CMC increases. It was demonstrated that ILs [bdmim][Br] and [hdmim][Br] can be judiciously used at different wt% for modifying the physico-chemical properties of TX-100.

In the present work, apparent molar volume and isentropic compression of glycine and diglycine in aqueous 1-butyl-3-methylimidazolium chloride, [C4mim][Cl] solutions have been calculated from the measured experimental data on density and speed of sound at temperature, T = (288.15, 298.15 and 308.15) K. The apparent molar volumes at infinite dilution, Vϕ0 and the apparent molar isentropic compression at infinite dilution Kϕ , S0, were also calculated. These results have been interpreted in terms of effect of temperature and concentration on interactions such as solute–solute, solute–solvent and solvent–solvent which exist in the mixtures. Furthermore, apparent molar expansivity, Eϕ0, and Hepler's constant values, ∂ E ϕ 0 ∂ T P have been evaluated to support the conclusions obtained from the volumetric and acoustic studies. The Hepler's constant values were found negative which indicating the amino acids under study are predominantly a structure breaker due to hydrophobic hydration of amino acid in aqueous [C4mim][Cl].

The self-organization and aggregation behavior of a surface active ionic liquid (SAIL) 1-methyl-3-octylimidazolium chloride [C8mim]Cl, was investigated in aqueous solutions of alcohols 1,2-propanediol and 1-propanol in different compositions using conductivity, surface tension and fluorescence measurements at room temperature. This surface active ionic liquid was synthesized by the reaction of 1-methylimidazole with 1-chlorooctane. Fluorescence spectroscopy was employed to get detailed insight into the local microenvironment of the aggregates, critical aggregation concentrations (CAC) and aggregation number (N agg.). Degree of ionization (α), CAC and various thermodynamic parameters like the standard Gibbs free energy of aggregation (ΔG agg. 0 ), standard enthalpy of aggregation (ΔH 0 ) and standard entropy of aggregation (ΔS agg. 0 ) were calculated using conductivity measurements at different temperatures (288.15, 298.15 and 308.15 K). The surface activity of the IL in various mixed solvents was evaluated from surface tension measurements by calculating various surface parameters like the minimum surface area occupied by a single ionic liquid molecule (A min), adsorption efficiency (pC 20), maximum excess concentration at the surface (Γ max), effectiveness of surface tension reduction(Π CAC), surface tension at CAC (γ CAC), p (packing parameter) and CAC at different compositions. Increases in the CAC values were observed with the increase in the amount of alcohols which is attributed to the balancing between electrostatic and hydrophobic interactions. The results from different techniques show that the CAC increases with increase in the amount of the alcohol which is due to the solubilization of the IL molecules which delays the aggregation process. This shows that the spontaneity of the aggregation process of IL decreases with the increase in the concentration of alcohols in water.

The structural and optical properties of the PANi films were investigated in terms of different solvent content by using X-ray diffraction (XRD), RAMAN spectroscopy, Scanning electron microscopy (SEM), Photoluminescence (PL) and optical absorption spectroscopy. The XRD results revealed that the crystallinity through films increased as the molar ratio of dimethylacetamide (DMAc and dimethylformamide (DMF) increased to 0.6:0.4, but then decreased when the molar ratio was increased from 0.6:0.4 to 0.8:0.2. It is shown that even small clusters in PANi films can explain the observed RAMAN scattering. The results of the optical experiments showed that films prepared from different molar ratio of DMAc and DMF showed good near-infrared characteristic in the range of 800-2000 nm. The optical band gap value from absorption coefficient data is found to be 3.57 eV. The SEM also showed changes in the morphology of PANi films.

The structural and optical properties of the PANi films were investigated in terms of different solvent content by using X-ray diffraction (XRD), RAMAN spectroscopy, Scanning electron microscopy (SEM), Photoluminescence (PL) and optical absorption spectroscopy. The XRD results revealed that the crystallinity through films increased as the molar ratio of dimethylacetamide (DMAc and dimethylformamide (DMF) increased to 0.6:0.4, but then decreased when the molar ratio was increased from 0.6:0.4 to 0.8:0.2. It is shown that even small clusters in PANi films can explain the observed RAMAN scattering. The results of the optical experiments showed that films prepared from different molar ratio of DMAc and DMF showed good near-infrared characteristic in the range of 800-2000 nm. The optical band gap value from absorption coefficient data is found to be 3.57 eV. The SEM also showed changes in the morphology of PANi films.

Lidocaine HCl and procaine HCl are local anesthetics widely used in minor chirurgic procedures; nevertheless, spectral information about their behavior is not complete at present. In this context, in this paper, absorbance and fluorescence studies of both the drugs with α- and β-cyclodextrins (CDs) have been measured at 298.15 K. The thermodynamic parameters: binding constant (K) and standard state Gibbs energy (∆G°) were calculated for the systems in which complex formation was observed. The α- and β-CD study indicates that the lidocaine HCl and procaine HCl drugs form 1:1 inclusion complex with α- and β-CD. Both experimental and theoretical studies revealed that the phenyl ring with the amide group of the drug is encapsulated in the hydrophobic CD cavity. van der Waals interactions are mainly responsible for complex formation of lidocaine hydrochloride and procaine hydrochloride with CDs.

Volumetric and ultrasonic properties of ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C4mim][NTf2] and 1-butyl-3-methylimidazolium methylsulfate [C4mim][C1OSO3] with 1,2-propanediol (1,2-PD) have been investigated using density, ρ speed of sound, u measurements over the entire composition range at T = (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K. The density values were used to calculate excess molar volume, V m E whereas speed of sound results have been used to calculate deviation in isentropic compressibility, Δ κ S . Excess properties have been fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard deviations. Spectroscopic technique like Fourier transform infrared (FT-IR) has been utilized for analyzing molecular level interaction prevailing between the binary mixtures. FT-IR technique has been used to scrutinize the –OH interactions between the binary mixtures and the influence on the structural variations in the ionic liquid. The excess properties and spectroscopic data have been analyzed in terms of the effect of temperature and the change of the anion of ionic liquid.

Micellization behaviour of cetyltrimethylammonium bromide (CTAB) in the presence of ionic liquid (IL), 1-butyl-2,3-dimethylimidazolium bromide [bdmim][Br] in aqueous medium has been investigated by conductance, fluorescence, 1H NMR, dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. The temperature dependence of critical micelle concentration (cmc) obtained from conductivity measurements at different temperatures (298.15, 308.15, and 318.15) K has been used to calculate various thermodynamic parameters of micellization and the obtained parameters are further used to understand the surfactant-IL interactions for the studied (0–0.2) wt% of IL. Further fluorescence technique has been used to obtain the cmc and aggregation number from (0–30.0) wt% of added IL in the surfactant solution using different probes at 298 K. To understand the variation in micellar size at different wt% of IL, DLS and TEM techniques have been employed. Interestingly, due to presence of IL in surfactant solution in either low or high proportion, micellar size increases. IL effectively enhances the surface activity of surfactant solution until 2.0 wt% of added IL but above this wt% it starts increasing cmc. The crucial role of electrostatic interactions is clearly implied by 1H NMR studies.

Binding interactions between surface active ionic liquid (SAIL) [C8mim][Br] and sodium polystyrene sulfonate (NaPSS), an anionic polyelectrolyte were analyzed from techniques such as conductometry, tensiometry, dynamic light scattering (DLS) and fluorimetry. Typical surface tension profile shows the existence of noticeable elevation in the value of surface tension at IL concentrations before the critical micelle concentration (cmc) of the SAIL. By using conductivity measurements we have calculated the cmc and degree of ionization, α, at various temperatures from 298.15 to 318.15 K. A series of thermodynamic parameters like standard enthalpy of micellization ( Δ H m ° ) , standard free energy of micellization ( Δ G m ° ) and standard entropy of micellization ( Δ S m ° ) have been evaluated. Behavior of fluorescence probe, pyrene and DLS measurements confirm the binding interactions between SAIL and the polyelectrolyte. It has been found that the cmc values significantly increase with higher concentration of polyelectrolyte due to hydrophobic interactions. The Gibb's free energy ( Δ G m ° ) is negative for the above systems and increases with increasing polyelectrolyte concentration.

The apparent molar volumes, Vϕ, apparent molar adiabatic compressibilities, Kϕ , s, apparent molar volumes at infinite dilution, Vϕ0, and apparent molar adiabatic compressibilities at infinite dilution, Kϕ , s0 are evaluated from the measured densities, ρ, and speeds of sound, u, values, for α-cyclodextrin and β-cyclodextrin in aqueous sulfamethoxazole solutions at T = (288.15, 293.15, 298.15, 303.15, 308.15) K. Further, transfer partial molar volume, ΔVϕ0 at infinite dilution, transfer partial molar adiabatic compressibilities, ΔKϕ , s0 at infinite dilution and pairwise and triplet interaction coefficients, are discussed in terms of solute–solute and solute–solvent occurring in the ternary solution of present study.