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•The encapsulation of piracetam in nonionic micellar system to calculate partition coefficient and binding constant.•Tween 80 and Triton X – 100 are utilized to enhance the solubility ...and bioavailability of piracetam.•The encapsulation of piracetam in tween 80 micelles is more prominent and more spontaneous.•Mixed micellization is more favorable and effective than single surfactant micellization.
Nonionic surfactants have drawn tremendous attention for micellar solubilization, sustained release of the drug, encapsulation of pharmaceutically active ingredients, and permeabilization due to their distinct physicochemical characteristics. Concise solubility investigations are required for the appropriate selection of nonionic surfactant that is to be used for a formulation. In the present research, a cluster of micelles was developed that relies on trapping and stabilizing piracetam by balancing the hydrophilic and hydrophobic forces of nonionic surfactants. Tween 80 and Triton-X 100 and a mixture of these surfactants were used to clarify the drug-surfactant interaction in an aqueous and micellar medium. The interaction was investigated in premicellar, micellar, and post-micellar regions by using UV/Visible spectroscopy. Spectroscopic parameters were calculated to determine the degree of solubilization in terms of the partition coefficient (Kx), binding constant (Kb), and their respective energies in terms of Gibbs free energy of partition (ΔGp) and Gibbs free energy of binding (ΔGb) for piracetam. The solubilization of piracetam is enhanced by mixing an adequate amount of both nonionic surfactants. The obtained results demonstrated that solubilization is spontaneous and entropically favorable and the cluster of micelles in both single and mixed micellar mediums are stable due to the presence of a much more hydrophobic and hydrophilic culture which provides a synergistic link between the two surfactants.
The comparison of theoretical values of ΔG of interactions with those obtained by different experimental methods. Display omitted
► There is no direct correlation between the dissociation degree and ...aggregation number. ► Tendency of surfactants micellization can be predicted from their surface tension data. ► Klevens equation constants can be calculated from the surfactant interactions through the water phase.
Measurements of density, viscosity, conductivity and light scattering of aqueous solutions of sodium dodecylsulfate (SDDS), sodium hexadecylsulfonate (SHS), sodium N-lauryl sarcosinate (SDSa), cetyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPyB), dodecyldimethyethylammonium bromide (DDEAB), tetradecyltrimethylammonium bromide (TTAB), benzyldimethyldodecylammonium bromide (BDDAB) and Triton X-100 (TX-100), Triton X-114 (TX-114), Triton X-165 (TX-165) were carried out at different temperatures. On the basis of the results obtained from these measurements critical micelle concentration, aggregation number, apparent and partial molar volume, standard Gibbs energy, enthalpy and entropy were calculated. In the case of ionic surfactants the degree of surfactant dissociation in micelle was taken into account. There was also determined the standard Gibbs energy of micellization using hydrophobic tail-water, hydrophilic head-water interfacial free energy and electrostatic intermolecular interactions. Then the results were compared with those obtained by other methods and the literature data. The presence of micelles at the concentration of aqueous surfactant solutions determined by the above mentioned methods was confirmed by the light scattering measurements.
Inclusion complexation of surfactant with β-cyclodextrin (β-CD) is an active research topic in supramolecular chemistry. For the mixed system of β-CD and cationic/anionic surfactants, the ...thermodynamic and molecular dynamics (MD) simulation studies can provide valuable information about synergism between cationic and anionic surfactants and competition between inclusion complexation and mixed micellization. Experimental results indicated a synergistic effect between CTAB and SL in surface tension reduction efficiency and effectiveness, and in mixed micelle formation. The surface tension experiments indicated that for single surfactant CTAB or SL, the binding stoichiometry was β-CD:surfactant = 1:1. For the 1:1 β-CD/surfactant inclusion complexes, umbrella sampling simulation results indicated that SL bound preferentially to the wide rim of β-CD, while, CTAB had a similar probability of binding to either rim of β-CD. Both experimental and simulation results indicated that the inclusion affinity of β-CD with CTAB was significantly stronger than that of β-CD with SL. Due to the electrostatic attraction between the oppositely charged headgroups, the distance between adjacent CTA+ and L− ions was significantly shorter than that between two adjacent CTA+ (or L−) ions. It encouraged us to explore whether the 1:1:1 β-CD/CTAB/SL inclusion complex could form. The MD simulation results indicated that all four possible initial 1:1:1 conformations were unstable. The final stable inclusion complexes were in 1:1 β-CD/CTAB and 1:1 β-CD/SL forms consistent with the umbrella sampling simulation results of the single surfactant. The results suggested that the inclusion interaction becomes less competitive with mixed micellization as the composition approaches the equimolar ratio of CTAB and SL.
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•Strong synergism exists between cetyltrimethylammonium bromide and sodium laurate.•Competition between inclusion complexation and mixed micellization weakens synergism.•Sodium laurate (SL) binds preferentially to the wide rim of β-cyclodextrin (β-CD).•CTAB has a similar probability of binding to either rim of β-CD.•All the four possible initial 1:1:1 β-CD/CTAB/SL inclusion complexes are unstable.
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The micellization of block copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) is driven by the dehydration of PPO at elevated temperatures. At low ...concentrations, a viscous solution of isolated micelles is obtained, whereas at higher concentrations, crowding of micelles results in an elastic gel. Alternating PEO-PPO multiblock copolymers are expected to exhibit different phase behavior, with altered phase boundaries and thermodynamics, as compared to PEO-PPO-PEO triblock copolymers (Pluronics®) with equal hydrophobicity, thereby proving the pivotal role of copolymer architecture and molecular weight.
Multiple characterization techniques were used to map the phase behavior as a function of temperature and concentration of PEO-PPO multiblock copolymers (ExpertGel®) in aqueous solution. These techniques include shear rheology, differential and adiabatic scanning calorimetry, isothermal titration calorimetry and light transmittance. The micellar size and topology were studied by dynamic light scattering.
Multiblocks have lower transition temperatures and higher thermodynamic driving forces for micellization as compared to triblocks due to the presence of more than one PPO block per chain. With increasing concentration, the multiblock copolymers in solution gradually evolve into a viscoelastic network formed by soluble bridges in between micellar nodes, whereas hairy triblock micelles jam into liquid crystalline phases resembling an elastic colloidal crystal.
Herein, we have checked the interaction between the imipramine hydrochloride (IMH, an antidepressant drug) and anionic surfactant dioctyl sulfosuccinate sodium salt (AOT) mixed system through a ...conductometric method in aqueous medium along with electrolyte solutions at different temperatures (288.15 to 303.15 K). Considerable changes were obtained in the different physicochemical parameters estimated in the current system. The AOT has an exceptional surface activity together with a very low critical micelle concentration (cmc) value as compared with other anionic surfactants, therefore, having much less toxicity. The deviations between observed cmc and ideal critical micelle concentration (cmcid) values point to an interaction between IMH and AOT. The value of cmc of the mixed system reduces through the increase of the mole fraction of AOT. With a rise in the temperature, the cmc value of pure IMH along with IMH–AOT mixtures increases first and then decreases with a further rise in the temperature. In the presence of 50 mmol·kg−1 NaCl, the observed cmc of the individual constituents along with IMH–AOT mixtures was clearly lower than that in an aqueous system. The micellar mole fraction values according to different proposed models X1Rub (Rubingh), X1Mot (Motomura), X1Rd (Rodenas) and X1ideal (ideal mole fraction) were estimated and the results obtained reveal the high contribution of AOT in the mixed micellization and the values increase through the rise in the mole fraction of AOT. At all studied temperatures the magnitudes of free energy of micellization (∆Gm0), interaction parameter (β) along with excess free energy (∆Gex) evaluated for the current studied system were obtained to be negative. The value of the activity coefficients (f1 and f2) were also computed by employing the method specified in the literatures. The negative values of enthalpy (ΔHm0) of the systems at lower temperature indicate the micellization is exothermic while at higher temperature negative values of ΔHm0 becomes positive, which means the micellization process becomes endothermic. The values of entropy (ΔSm0) were found to be positive in all cases. All of the estimated results imply a strong interaction among the studied constituents.
•Association behavior of IMH-AOT mixtures has been evaluated.•Different theoretical models were employed to know environment of interaction.•In the presence of NaCl aggregation occurs at lower concentration.•Gibbs free energy (∆G0m) valued for all studied systems were obtained to be negative.•The ∆H0m, ∆S0m and ΔGex values were also evaluated and discussed.
This review highlights recent advances in the micellization of synthetic graft copolymers and those based on natural precursors, particularly polysaccharides. Synthesis and characterization of a ...broad range of architectures are discussed, along with different micellization procedures and fundamental micellar characteristics, such as morphology and size. Micelle formation by synthetic graft copolymers in aqueous media is examined in detail for different architectures of nonionic, ionic, and temperature and pH stimuli-responsive “double hydrophilic” copolymers. In this context, the problems associated with unimolecular micelles and the correlations between molecular characteristics are further addressed. In addition to backbone and side chain molecular weights, grafting density and topology are the major parameters that directly influence graft copolymer micellization. A similar overview is provided for graft copolymers based on polysaccharides, such as cellulose, chitosan, dextran, and starch. Finally, an outlook is given on the prospects for further development in this area.
Measurements of density, viscosity and light scattering of aqueous solutions of food additive antimicrobial surfactants: sucrose capric acid ester (SMD) and sucrose lauric acid ester (SML) and some ...other sugar-based ones (n‑octyl‑β‑d‑glucopyranoside (OGP), n‑dodecyl‑β‑d‑glucopyranoside (DDGP), n‑dodecyl‑β‑d‑maltoside (DM)) as well as the fluorescence intensity of 8‑Anilino‑1‑naphthalene-sulfonic acid (ANS) and pyrene (Py) in aqueous solutions of the studied surfactants were carried out at different temperatures. On the basis of the obtained results the critical micelle concentration, average aggregation number, apparent and partial molar volume as well as the standard Gibbs free energy, standard enthalpy and entropy of micellization were determined. From the obtained thermodynamic parameters of micellization of studied sugar surfactants under different conditions, the temperature and type of surfactant impact on their aggregation properties were deduced. From the changes of the standard Gibbs free energy of micellization it results that the tendency of studied surfactants molecules to form micelles comes down as the temperature and surfactant tail length decrease. The presence and strength of the hydrogen bonds between the water molecules and sugar moiety in a surfactant molecule plays a decisive role in the micellization process of the studied sugar-based surfactants.
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•Effect of temperature on aggregation properties depends on head group polymerization degree.•Sugar surfactant micelles are not spherical.•∆Smic0 indicates what during the micellization process the chemical bonds are broken.•Entropy is the main driving force for micelle formation by sugar surfactants.
•The CMC values increased with increasing temperature, while decreased with increasing hydrocarbon chain length.•Increasing ethanol concentration reduced CMC up to a certain value.•ΔGm0 and ΔHm0. ...values showed micellizations were spontaneous and exothermic.•Enthalpic contributions in mixed water–ethanol systems predominated with increasing ethanol concentrations and temperature.
The micellization behaviors of n-decyl-4-methylpyridinium bromide, n-dodecyl-4-methylpyridinium bromide, and n-tetradecyl-4-methylpyridinium bromide were studied in water and mixed water–ethanol media by using conductivity measurements over the temperature range of 293.15–318.15 K. The critical micelle concentrations (CMC) of all n-alkyl-4-methyl pyridinium bromides studied increased with increasing temperature, but they decreased with increasing hydrocarbon chain length. Their CMC values of n-decyl-4-methylpyridinium bromide, n-dodecyl-4-methylpyridinium bromide, and n-tetradecyl-4-methylpyridinium bromide in water at the temperature range of 293.15–318.15 K were determined as in the range of 43.62–46.42, 10.45–11.57, and 2.78–3.20 mM, respectively. Moreover, the lowest CMC values of n-decyl-4-methylpyridinium bromide, n-dodecyl-4-methylpyridinium bromide, and n-tetradecyl-4-methylpyridinium bromide were found with 15, 5, and 5 vol% ethanol additions, respectively. The calculated negative ΔGm0 and ΔHm0 values proved that their micellizations in water and mixed water–ethanol media were spontaneous and exothermic. Also, ΔGm0 values became the more negative with the longer the hydrocarbon chain length. Furthermore, their micellization processes in water were determined to be entropy controlled, however enthalpic contributions in the mixed water–ethanol systems started to predominate with increasing ethanol concentrations and/or temperature.
Anhydride-modified starch micelles have great potential in the delivery of hydrophobic guest molecules. This study aimed to experimentally explore the effects of side-chain lengths on the structure ...and properties of anhydride-modified starch micelles, and to visualize the self-assembly and loading process of these micelles through Dissipative particle dynamics (DPD) simulations. Starch micelles could only form when the carbon chain length exceeded four. The highly hydrophobic C18 starch micelle exhibited the minimum particle size (65 nm) and maximum loading capability (59.10 μg/mg). For each addition carbon atom in the anhydride side chains, the critical micelle concentration (CMC) of starch micelles decreased average of 1.79 %. Thermodynamic results showed that the micellization was an entropy-dominated driven process, and longer carbon chains enhanced the stability of starch micelles. DPD results showed that the starch chains formed the small clusters then spherical aggregates and finally core-shell structure spherical micelle. Curcumin was loaded into micelles by adjoint aggregation-micellization-adsorption mechanism. Overall, this study provides microscopic insight into the micellization and drug-loading mechanisms for anhydrides modified starch micelles.
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•DPD simulation was first applied to investigate the micellization of starch micelle.•The core-shell structure of starch micelles was confirmed by DPD simulation.•Curcumin was loaded into starch micelles by adjoint aggregation and absorption step.•Longer carbon chains resulted in higher stability and smaller size of micelles.•CMC has a linear negative correlation with the number of side-chain carbon atoms.
Abstract
In this review amino acid-surfactant interactions mainly in aqueous solution has been explained. Amino acids and surfactants interactions are important in many studies because of their ...enhanced effectiveness in both living and non-living worlds. As physicochemical properties are additive, the study of interactions between amino acids and surfactants offer insights into how proteins unfold and denaturate in various media, which further alters with a change in physiological parameters like pH, additives, no of carbon in the chain and temperature. Keeping this in mind, in this review main emphasis has been on conductometric, volumetric and computational studies for detailed exploration of solute–solvent interactions of amino acids and surfactants in aqueous medium and effect of temperature on these interactions. Conductance data has been used to find the critical micelle concentration (CMC) of the surfactant. Using CMC, standard Gibbs free energy of micellization,
(
$${\Delta G}_{{\text{m}}}^{{0}}$$
Δ
G
m
0
)
, enthalpy of micellization, (
$${\Delta H}_{{\text{m}}}^{{0}}$$
Δ
H
m
0
), entropy of micellization, (
$${\Delta S}_{{\text{m}}}^{{0}}$$
Δ
S
m
0
) have been determined for surfactant in presence of amino acids. In volumetric investigation, density data has been utilized to find apparent molar volumes of amino acids, (ϕ
v
) and partial molar volume (ϕ
0
v
), which is used to find soute-solvent interaction. In computational studies the effects of carbon tail length on CMC and aggregation number, (A
g
) for the pure Gemini surfactant system were examined and these data were compared with experimental results to find the agreement between different methods.
