Cationic Gemini Surfactants Research Articles

Rheological and thermo-responsive characteristics of the mixed aqueous solution of gemini cationic surfactant and hydroxyl naphthalene carboxylic acid sodium

ABSTRACTThe new thermo-switchable wormlike micellar systems were developed by mixing the gemini cationic surfactant, 2-hydroxypropyl-1,3-bis (dimethylmyristylammonium chloride) (14-3(OH)-14(2Cl) and sodium 1-hydroxynaphthalene-2-carboxylate (1SHNC) and sodium 2-hydroxynaphthalene- 3-carboxylate (2SHNC) in a certain concentration range. Their viscoelastic and thermos-responsive behaviors as a function of the salts concentration or temperature were investigated via rheological and cryo-TEM investigations. The results demonstrated that the zero-shear viscosity (η0) significantly increased while raising salt concentrations above a threshold concentration (CS*) until reaching maximum and then decreased. For the mixed solutions before the maximum, the zero-shear viscosity linearly decreased with increasing temperature and conformed to the Arrhenius law. However, for those mixed systems displaying thermo-responsive characteristic after the summit, the curve of η0 as a function of temperature exhibited a maximum over the whole temperature range, namely, the systems showed thermo-thickening and thermo-thinning behaviors at low and high temperatures. The abovementioned phenomena were explained by the formation of hydrogen bond in 14-3(OH)-14(2Cl) molecules and the different solubility of SHNC under different temperatures, and the transition mechanisms of the aggregates were analyzed accordingly.

Reutilization of thickener from fracturing flowback fluid based on Gemini cationic surfactant

Due to the high cost and environmental damage characteristics of the viscoelastic surfactant (VES) fracturing, a method for recycling the VES from the flowback fluid was proposed in this study. Herein, such VES could be prepared easily and it can be recovered from the flowback fluid based on phase separation by adding a certain amount of hydrochloride acid. Based on this proposed method, the VES in the flowback fluid can be recycled to the greatest extent and the waste fluid can be effectively handled by the base neutralization process. The recycled VES can form wormlike micelles in the aqueous solution, and the fracturing fluid prepared from the recycled VES showed good elasticity and thermal stability. The molecular structure analysis showed that the recycled VES molecules maintained good integrity, which provided a solid basis for recycling the VES from the VES-M fracturing fluid. This technique not only can largely increase the utilization rate of thickener of VES fracturing fluid but also promote the treatment of the flowback fluid in hydraulic fracturing.

An intermittent amyloid phase found in gemini (G5 and G6) surfactant induced β-sheet to α-helix transition in concanavalin A protein

Surfactant-induced amyloid fibrillation has many implications in laboratory and industry. Previously, cetyltrimethylammonium bromide (CTAB; C19H42BrN) induced amyloid formation in concanavalin A (ConA) has been reported by authors (Khan, JM et al., 2016 A). In this work, cationic gemini surfactants pentanediyl‑1,5‑bis (dimethylcetylammonium bromide); 16-5-16 (G5), and hexanediyl‑1,6‑bis (dimethyl cetyl ammonium bromide); 16-6-16 (G6) were found to induce amyloid-like aggregation in ConA as studied with turbidity at 350 nm, Rayleigh scattering and Thioflavin T (ThT) binding assay and Far UV CD. The sizes of the aggregates were characterized with dynamic light scattering (DLS) and atomic force microscopy (AFM). Hydrodynamic radii (Rh) of the aggregates were found to be 74 nm and 122 nm with 50 μM of G5 and G6 respectively. Even at 7.5 μM, gemini surfactants seems disrupting hydrophobic pockets of ConA and result in aggregation. On the contrary, aggregation disappeared around 250 μM surfactant concentration with β-sheet → α-helix transition. The re-establishment of intra-molecular hydrogen bonding may have resulted in the formation of non-native α-helical structures. Alcohols, predominantly 2,2,2‑trifuloroethanol (TFE), have been reported to induce α-helices in β-sheet proteins by solvent engineering. There are very few reports of β-sheet to α-helix transition induced by non-alcoholic substances. Our lab is pioneer in reporting surfactant (CTAB) induced β-sheet to α-helix transition in ConA (Khan, JM et al., 2016 A). This is the first report of G5 and G6 gemini surfactant induced β-sheet to α-helix transition, as per our knowledge. ConA being apoptotic to cancerous cells and having potential therapeutic effect on hepatoma, the observations done in this work could be of immense interest in vesicular delivery of ConA.

Thermodynamics of self-aggregation of mixed cationic gemini/sodium deoxycholate surfactant systems in aqueous solution

Thermodynamics of interaction between cationic gemini surfactants [C12H25(CH3)2N(CH2)sN(CH3)2C12H25]Br2, (s = 2, 6 or 10, assigned as C12CsC12Br2) and sodium deoxycholate (NaDC) in aqueous solution has been investigated by isothermal titration calorimetry (ITC), fluorescence and turbidity measurements. The critical micelle concentrations for NaDC-rich mixture (cmcmix,12-s-12) were determined by fluorescence method. The cmcmix,12-s-12 values are much smaller than those for pure C12CsC12Br2 surfactants, and decrease as the spacer length ‘s’ increases. There is a strong synergistic effect between two surfactants in the NaDC-rich region. In the higher C12CsC12Br2 concentration range above cmcmix,12-s-12, we did obtain from ITC and turbidity measurements the critical parameters for different events that occur as the C12CsC12Br2 concentration increases, including the critical concentrations (CP, CR, CM) of formation and redissolution for LC of the mixed C12CsC12Br2/NaDC systems and transition to gemini-rich micelles. In comparison with the mixed C12CsC12Br2/NaC systems reported with sodium cholate (NaC), the mixed systems with NaDC have lower cmcmix,12-s-12, CP, CR and CM, and thus different self-aggregation processes are well controlled by surfactant concentration and molar fraction. Importantly, ITC allowed us to directly measure the enthalpy changes corresponding to different self-aggregation processes—redissolution enthalpy (∆HR) of LC of mixed surfactants and transition enthalpy (∆HM) from LC to gemini-rich micelles. Eventually, we discussed the cross-linking effect on NaDC-rich micelles of the gemini surfactant (C12CsC12Br2) with double hydrophobic chains and cationic head groups linked through a methylene spacer.

Studies of interaction between ninhydrin and Gly-Leu dipeptide: Influence of cationic surfactants (m-s-m type Gemini)

Herein, we have reported the studies of interaction between ninhydrin and glycylleucine (Gly-Leu) dipeptide in cationic Gemini surfactants (m-s-m; m = 16; s = 4, 5, 6) by using spectrophotometric technique. The rate constant values, kψ, were determined at different temperatures and pH. The effect of concentration of reactants and surfactants was also carried out on the title reaction. It was also observed that the reaction was accelerated and catalyzed by 16-s-16 Gemini surfactants even at low critical micelle concentration (cmc) value of surfactants. The variation of Gemini surfactants on the reaction of ninhydrin with glycylleucine has been analyzed with the help pseudo-phase model of surfactants proposed by Menger and Portnoy and developed by Bunton. The binding constants for reactants (ninhydrin and Gly-Leu) have been computed using a computer based program.

Influence of different counterions on gemini surfactants with polyamine platform as corrosion inhibitors for stainless steel AISI 304 in 3 M HCl

The corrosion inhibition efficiency of two cationic gemini surfactants with different counterions with polyamine platform on AISI 304 stainless steel in 3 M HCl was investigated by polarisation measurements and electrochemical impedance spectroscopy (EIS). The surface of the samples was characterised before and after the corrosion experiments using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that the effectiveness of corrosion inhibiton depends on counterion belongs to surfactant molecule. The dimeric surfactant with the iodine counterion out–performs its bromine counterpart with respect to providing corrosion inhibition of stainless steel, in 3 M HCl. In the present study, the Langmuir adsorption isotherm was found to be suitable parameter for the correlating the experimental results with a possible mechanism of protection. In the case of two tested compounds the highest inhibition efficiency was found around the critical micelle concentration. Critical micelle concentration was determined using conductometric titration.

Comparative effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability of phospholipase A2

Herein, we have investigated the effect of cationic gemini surfactant (hexanediyl-α,ω-bis-(N-(2-hydroxyethyl)N-methylhexadecylammonium bromide), (16-6-16MEA) and its monomeric counterpart (N-(2-hyroxyethyl)N, N-dimethylhexadecylammonium bromide), (16MEA) on the conformational stability of phospholipase A2 (PLA2). The interaction of gemini surfactant and its monomeric counterpart with PLA2 was characterized by utilizing steady-state fluorescence, time-resolved fluorescence, CD spectroscopy, and computational methods. The steady-state fluorescence results suggested the involvement of static quenching mechanism which was further supported by time resolved fluorescence measurements. The Stern-Volmer equation was utilized to calculate the value of Stern-Volmer quenching constant KSV. The stoichiometric binding ratio of PLA2 with 16MEA and 16-6-16MEA was observed to be 1:1. The far-UV CD spectra for PLA2 revealed similar alteration in secondary structure, in presence of 16MEA and 16-6-16 MEA, which was further supported by computational methods.

Formation of Mixed Micelles of the Environmentally Acceptable Oxy-Diester-Linked Gemini Surfactants with Brij 58

Abstract Three oxy-diester-linked cationic gemini surfactants (2,2′-[(oxybis(ethane-1,2-diyl))bis(oxy)]bis(N-alkyl-N,N-dimethyl-2-oxoethanaminium) dichloride, Cm-DEG-Cm (m = 12, 14, 16), were synthesized. The physicochemical properties of the gemini surfactants and their mixtures with Brij 58 were studied by surface tension measurements at various mole fractions and 30°C. The critical micelle concentration (CMC) of the gemini surfactants are smaller than that of their corresponding single-chain counterparts having the same number of carbon atoms in the hydrophobic tail versus polar head. At all investigated compositions, the experimentally obtained CMC values of the surfactant mixtures are smaller than the CMCideal (ideal CMC – CMC of the solution at ideal state); the lower CMC of the mixed systems compared to those the individual surfactants and the negative β values (for both the mixed micelles and monolayers) indicate a synergistic interaction among both the surfactant components. The interaction parameters (βm and βσ) of the mixed surfactant systems were evaluated by using theoretical models. Negative values of β imply an overall attractive force in the mixed state. Also, the free excess energy of mixing was found to be negative for all the systems.

Thermodynamic and Interfacial Properties of Cationic Gemini Surfactant in the Presence of Alcohols

Abstract The micellar properties of the cationic Gemini surfactant ethanediyl-1,2-bis(dimethyldodecyl ammonium bromide), C12H25 · (CH3)2N+–(CH2)2–N+(CH3)2C12H25 · 2Br− (12-2-12), with short chain alcohols have been studied by conductivity and surface tension measurements within the temperature range 293.15 K–313.15 K and alcohol percentage. The critical micelle concentration (CMC) of 12-2-12 solution, degree of ionization (α) and standard Gibbs free energy of micellization (ΔG°m), standard enthalpy of micellization (ΔH°m) were calculated from conductivity and surface tension data. The experimental data show that the CMC values of cationic Gemini surfactants increased with addition of methanol, ethanol and n-propanol. The thermodynamic parameters (ΔG°m), (ΔH°m) and (ΔS°m) of micellization of 12-2-12 in alcohol were also calculated from the temperature dependence of the CMC values. CMC, (α), (ΔH°m) and (ΔS°m) increased linearly with increasing temperature. In the mixture of dimeric cationic surfactant (12-2-12) and alcohol solutions, the CMC values showed a slight increase with increasing alcohol concentration. CMC, maximum surface excess concentration at the solution/air interface, Γmax, minimum area per surfactant molecule, Amin, and the surface pressure at CMC, ¶CMC, values calculated from the surface tension measurements and thermodynamic parameters have been evaluated at same temperatures.

Asymmetric cationic gemini surfactants: an improved synthetic procedure and the micellar and surface properties of a homologous series in the presence of simple salts

The micellar and morphological properties of symmetric, cationic gemini surfactants have been well studied in the literature as a function of nature and type of the spacer group and the length and type of hydrophobic chain. In this paper, we have examined the effects of tail asymmetry on the properties of a series of cationic surfactants, the N-alkyl-1-N′-alkyl-2-N,N,N′,N′-tetramethyldiammonium dibromide. A novel synthetic method is used to prepare a series of these surfactants and the consequences of asymmetry on micellar properties are presented. This new method has been shown to be more efficient, with higher yields of the asymmetric surfactants than the yields of the accepted literature method. The critical micelle concentration values and the micelle sizes of the asymmetric gemini surfactants, 12-4-12, 12-4-10, 12-4-8, and 12-4-6 gemini surfactants, were obtained from conductivity and dynamic light scattering. With increasing chain asymmetry, the size of the micelle increased due to the formation of loose micelles. The addition of NaCl and Na2SO4 to the surfactant solutions increased the aggregate size, and this effect was more pronounced with increasing salt concentrations. These results are interpreted in terms of the effect these ions have on the “compactness” of the micelle structure.

Three tetrasiloxane-tailed cationic gemini surfactants: The effect of different spacer rigidity on surface properties and aggregation behaviors

Gemini cationic surfactant with tetrasiloxane-tailed has potential to improve performance and biocompatibility in a range of applications. With different rigidity spacers, structure effects on their self-assembling behavior and interface properties are obvious. Hence, it should be possible to tune system surface properties and aggregation morphology in aqueous solution by changing rigidity of spacers. A series of novel cationic tetrasiloxane Gemini surfactants MR8M, MDM, MDOM were designed and synthesized by a simple process. Their surface property, hydrolysis resistance ability, wetting ability, aggregation behavior as well as antibacterial activity in aqueous solutions were studied. These three surfactants exhibited high hydrolysis resistance in both acidic and neutral aqueous solutions. On one hand, surface tension of MR8M (γCMC = 19 mN/m) and MDOM (γCMC = 23 mN/m), significantly lower than C8-PSi-C8 (γCMC = 37 mN/m) with siloxane spacer and pure hydrocarbon equivalents. On the other hand, MR8M can wet the highly hydrophobic PTEF plate completely at low concentration (0.4 mM). In addition, different aggregations, MDM with only vesicle, MDOM with spherical micelle and vesicle micelle and MR8M spherical micelle, wormlike micelle and vesicle were observed to assemble. Moreover, the antibacterial activity of these surfactants increased as the rigidity of spacer increased and MDM exhibited best antibacterial activity.

A New Phase Transfer Strategy to Convert Protein-Capped Nanomaterials into Uniform Fluorescent Nanoclusters in Reverse Micellar Phase.

A new phase transfer strategy to convert aqueous phase protein-protected nanomaterials into fluorescent nanoclusters in the reverse micellar environment is introduced using bovine serum albumin (BSA)-protected silver nanoclusters (AgNCs) and nanoparticles (AgNPs) as an example. The basic pH employed in the fabrication of protein-protected nanoclusters induces the the protein capping to be negatively charged and facilitates the transfer process of the nanomaterials from aqueous phase to a cationic gemini surfactant (16-2-16)/hexane/hexanol/water reverse micelle (RM) phase. The original fluorescence characteristics of the seed nanocluster is retained after the transfer process. Strikingly, when both the nanomaterials (AgNCs and AgNPs) coexist in the aqueous feed solution, they are exclusively converted into uniform nanoclusters in the RM extract with enhanced fluorescence intensity.

Solubility Enhancement of Polycyclic Aromatic Hydrocarbons by an Eco-Friendly Ester-Linked Gemini Surfactant and its Mixtures with Conventional Surfactants

AbstractThe present study deals with the solubility enhancement of the two polycyclic aromatic hydrocarbons (PAHs) anthracene and pyrene in the aqueous micellar system of the cationic ester-containing cleavable gemini surfactant ethane-1,2-diyl-bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride (14-E2-14 = C14H29(CH3)2N+(CH2COOCH2)2N+(CH3)2C14H29 · 2Cl−)), and its equimolar binary mixtures with some typical conventional cationic, anionic and non-ionic surfactants. The surface tension and conductivity measurements were used to evaluate the physicochemical parameters such as the critical micelle concentration (CMC), the interaction parameter (βm) and Gibbs excess free energy of micellization (ΔGexm) of the systems. The extent of solubilization of the micellar systems towards PAHs has been quantified in terms of molar solublization ratio (MSR), micellar/water partition coefficient (ln Km) and the standard Gibbs free energy of solubilization (ΔGs0). Above the CMC, all studied single as well as binary gemini-conventional surfactant systems show an increase in solubilization of the PAHs. For pure systems, the MSR value of Brij 58 was found to be significantly higher than that of the other amphiphiles. Amongst the mixed surfactant systems, the solubility enhancement of anthracene is found to be maximum in the 14-E2-14 + SDS/SDBS system whereas the system14-E2-14 + Brij 58 shows a higher solubility for pyrene.

Aggregation Behavior of Monomeric Surfactants and a Gemini Cationic Surfactant by NMR and Computer Simulation Data

Aggregation of decyltrimethylammonium bromide and cetyltrimethylammonium bromide (CTAB) in D2O has been studied. Spin–lattice relaxation time and self-diffusion coefficient of surfactant molecules were measured at concentrations below and above surfactant critical micelle concentration. The aggregation properties of conventional surfactant, CTAB, examined by nuclear magnetic resonance (NMR) and molecular dynamic (MD) simulation, were compared with the properties of double-tail analog, N,N,N′,N′-tetramethyl-N,N′dihexadecyl-1,4-butan di-ammonium di-bromide (BCTA). Both NMR and computer simulation methods suggest that micellization is a stepwise process and the pre-micellar aggregates take place in a solution at concentration below critical micelle concentration. According to MD simulation Gemini surfactant, BCTA, forms worm-like micelles, whereas CTAB, which may be considered as its “monomer”, forms only elongated micelles.

Effect of monovalent anions on cationic Gemini micro-emulsion

Micro-emulsion usually consists of water, oil, surfactants and co-surfactants, and each component has an effect on the phase behavior and solubilization of the micro-emulsion. When the surfactant in the micro-emulsion system is quaternary ammonium cationic Gemini surfactant, the surfactant mainly combines with the anions in the salt. With the increase of salt concentration, the phase transformation of Winsor I → Winsor III → Winsor II occurred, but the optimum salinity and salt width are different because of the type of salt. The effects of 5 different kinds of monovalent anions, including C6H5SO3−, I−, Br−, NO3− and Cl−, on the phase behavior and solubilization of quaternary ammonium cationic Gemini micro-emulsion are researched by Winsor phase diagram. It is found that the effects of organic anions C6H5SO3− and I− on the phase behavior and solubilization of quaternary ammonium cationic Gemini micro-emulsion are most significant, and the effects of Br−, NO3− and Cl− are less significant. Meanwhile, when the optimum solubilization is achieved, the amount of sodium benzoate is the least, indicating that the organic anion has stronger self-organization behavior with quaternary ammonium cationic Gemini surfactants.

Corrosion of mild steel in hydrochloric acid solution in the presence of two cationic gemini surfactants with and without hydroxyl substituted spacers

The corrosion inhibition mechanism of mild steel in acidic solution and in the presence of two cationic gemini surfactants have been studied. These are two surfactants having 12-carbon hydrophobic tails: one with a tetramethylene spacer and the other one with the same spacer containing two hydroxyl groups. EIS and polarization and electrochemical noise measurements revealed superior corrosion inhibition of hydroxyl functional surfactant compared with its counterpart with no hydroxyl group. Surface analysis including AFM, and SEM confirmed less corrosion attacks on the sample exposed to hydroxyl functional surfactant solution. Quantum chemical parameters revealed a good correlation with electrochemical results.

Effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability and esterase activity of human serum albumin

The binding effect of gemini surfactant, hexanediyl-α,ω-bis-(N-(2-hydroxyethyl)–N-methylhexadecylammonium bromide) (16-6-16 MEA) and its monomeric counterpart N-(2-hyroxyethyl)-N,N-dimethylhexadecylammonium bromide (16-MEA) on the structure and esterase like activity of human serum albumin (HSA) was unravelled by using UV–visible, fluorescence, three dimensional fluorescence, time resolved fluorescence and circular dichroism techniques in combination with molecular docking and molecular dynamic simulation methods. Fluorescence quenching mechanism was employed to estimate the Stern–Volmer quenching constants, Ksv, and the corresponding thermodynamic parameters like ∆G, ∆S and ∆H for HSA-16 MEA/16-6-16 MEA systems. The results showed the static quenching mechanism and spontaneous binding of 16 MEA/16-6-16 MEA with HSA. In addition to other interactions, the hydrophobic interaction (which is more effective in case gemini surfactant) plays major role in the process of binding of both the surfactants with HSA. Synchronous fluorescence reveals that there is a slight effect of 16 MEA/16-6-16 MEA on the fluorescence intensity of tyrosine but a significant effect on tryptophan. UV–visible results obtained, suggest the complex formation between HSA and 16MEA/16-6-16 MEA through static quenching mechanism. Circular dichroism results confirmed that the decrease in the α-helical content of HSA is more on interaction with 16-6-16 MEA as compared to 16 MEA. In addition, the esterase activity of HSA was also done, which was found to decrease in presence of both 16 MEA and 16-6-16 MEA. Additionally, we also utilized computational approaches for deep insight into the binding of 16 MEA/16-6-16 MEA with HSA and the results well matched with our experimental results.

Rheological property and rheokinetics of novel photogelling fluids

ABSTRACTA novel photorheological fluid composed of cationic Gemini surfactant N, N’-bis (octadecyl dimethyl)-1, 2-dichloride-propyl ammonium salt (C18-3-C18) and trans-ortho-methoxycinnamic acid (trans-OMCA) was investigated. When C18-3-C18 and trans-OMCA are mixed in equimolar quantities, the result is a low-viscosity Newtonian fluid with no thixotropy. After irradiation by UV light (365 nm), trans-OMCA is converted to cis-OMCA, and in turn, the solution undergoes more than 50 fold increase in the relative viscosity and exhibits shear thinning and thixotropy. The viscosity rise is associated with the formation of wormlike micellar network in the solution, which was confirmed by cryo-scanning electron microscopy (cryo-SEM). Furthermore, the rheokinetics process of the C18-3-C18/trans-OMCA solutions during UV irradiation was studied and rheokinetics equation was established, which can well describe the dynamic changing of the rheological properties. Critical packing parameter was introduced to explain the mechanism of photo-induced micelle transition.

Impact of Cationic and Neutral Gemini Surfactants on Conidia and Hyphal Forms of Aspergillus brasiliensis.

This study investigates the biological activity of two cationic gemini surfactants, hexamethylene-1,6-bis-(N,N-dimethyl-N-dodecylammonium bromide) C6 and pentamethylene-1,5-bis-(N,N-dimethyl-N-dodecylammonium bromide) C5, and their two neutral analogs, hexamethylene-1,6-bis-(N-methyl-N-dodecylamine) (A6) and pentamethylene-1,5-bis-(N-methyl-N-dodecylamine) (A5). Experiments were performed with Aspergillus brasiliensis, which is used in the standard tests for biocides. The minimal inhibitory concentration (MIC) values for conidia and mycelium were determined using the dilution method. The viability of the conidia was evaluated using the plate count method. The dry mass of the mycelium was determined using the thermogravimetric method. Ergosterol was extracted from the mycelium and evaluated by gas chromatography. The effect of gemini surfactants on fungal morphology was observed using scanning electron microscopy. Cationic gemini surfactants were found to be active at lower concentrations compared to their non-ionic analogues, rapidly reducing the total number of conidia that were able to grow. They also decreased both the ergosterol content in the mycelium and its dry weight. These results suggest that cationic gemini surfactants C6 and C5 could have a wide range of practical applications as active compounds. However, it should be remembered that usage at too low concentrations, below the MIC, will only lead to short-term disturbances in the development of conidia and mycelium.

Effect of Urea on Solvation Dynamics and Rotational Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini Surfactants with Different Spacer Groups.

The present work highlights the effect of urea on solvation dynamics and the rotational relaxation of Coumarin 480 (C-480) in the Stern layer of aqueous micelles of cationic gemini surfactants, 12-4(OH)n-12 (n = 0, 1, 2). UV–visible absorption, steady-state fluorescence and fluorescence anisotropy, time-resolved fluorescence and fluorescence anisotropy, and dynamic light scattering measurements have been carried out for this study. The formation of micelles becomes disfavored in the presence of urea at high concentration. Solvation dynamics is bimodal in nature with fast solvation as a major component. The average solvation time increases, reaches a maximum, and then decreases with increasing concentration of urea because the degree of counterion dissociation also follows the same order with the addition of urea in the micellar solution. With increased degree of counterion dissociation, the extent of clustering of water molecules is increased, resulting in slower solvation process. The −OH group present in the spacer group of gemini surfactant controls the rate of solvation by shielding the water molecules from the probe molecules forming hydrogen bond. The microviscosity of micelles is decreased with increasing concentration of urea, as a result of which the rotational relaxation process becomes faster. In the presence of the −OH group in the spacer group, the microviscosity of micelles is enhanced, resulting in longer rotational relaxation time. Rotational relaxation process is bimodal in nature with the major contribution from the fast component to the fluorescence depolarization. Slow rotational relaxation is mainly due to the lateral diffusion of C-480 molecules along the surface of the micelle. The tumbling motion of the micelle as a whole is much slower than the lateral diffusion of C-480. Wobbling motion of C-480 becomes faster with increasing concentration of urea as a result of decreased microviscosity of micelles. The alignment of C-480 molecules in micelles might change with changing microviscosity.