Micellar Weight Research Articles

The size, shape and hydration of cetomacrogol 1000 micelles.

Abstract Cetomacrogol solutions have been studied by three techniques. The micellar weight in water has been found from light-scattering experiments to be 101,000; the micelles appear to be spherical. Viscosity measurements can be interpreted in terms of micellar hydration, and 1.96 g. water appear to hydrate 1 g. of cetomacrogol. A similar amount of hydration (1.92 g. water per g. cetomacrogol) can be calculated from the diffusion coefficient. A check on the micellar weight was obtained from the diffusion and viscosity results, giving 96,000, in good agreement with the result from light-scattering.

Micelle Formation by Lecithin in Some Aliphatic Alcohols

Abstract Lecithin has been studied in methanol, ethanol, butanol, and hexanol using light scattering and viscosity techniques. A new type of light scattering cell was employed. Micelles were present in all solvents, the micellar weights being 2,300; 7,100; 18,000, and 22,000 in the four alcohols respectively. It appeared that as the polarity of the solvent decreased, the micellar size increased. Dissymmetry measurements showed that no dimension of the micelles exceeded 270Å (λ/20), but high observed depolarisations showed that the particles were anisotropic. Viscosity measurements also gave an idea of the shape of the micelles, giving intercepts of plots of specific viscosity/solute volume fraction against solute volume fraction of 4.29, 4.26, 4.26, and 3.56 for the four alcohols respectively. Using the dimensions of the lecithin molecule, and the number of monomers present in the micelle, calculations of the theoretical viscosity intercept have been made for each solvent, and compared with values obtained experimentally

Effects of structural variations on non-ionic surfactants on micellar properties and solubilization: surfactants containing very long hydrocarbon chains.

Polyoxyethylene mono-ethers of dotriacontanol (C32E41) and 4,9-dimethyltritriacontanol (C35E40) have been synthesized. The micellar weights in water at 298K were 4.82 x 10(5) and 5.90 x 10(5), the aggregation numbers 212 and 260, and the levels of hydration 290 and 283 mol water mol-1 surfactant, respectively. The solubilization of azobenzene, cortisone acetate, griseofulvin, sulphadiazine, phenylbutazone, betamethasone, tolbutamide, and menaphthone was studied in 2% solutions of the above surfactants. The presence of large micelles did not result in increased solubilization; C32E41 and C35E40 had a lower solubilizing capacity than that of cetomacrogol.

Membrane osmometry of solubilized systems.

Abstract The solubilization of decane, ethyl p-hydroxybenzoate, methyl anisate and p-hydroxybenzoic acid by aqueous micellar solutions of cetomacrogol 1000 has been examined by membrane osmometry and viscosity techniques. The effect of the solubilizates on the number-average micellar molecular weight, Mn, has been related to their site of incorporation in the micelle. Decane and methyl anisate are solubilized in the hydrocarbon core of the micelles and both compounds produce an increase in Mn up to a maximum value of 2·0 times 105, at a solubilizate concentration of approximately 80% of the saturation limit for each compound. This increase is shown to result from an increase in the number of molecules of both solubilizate and of surfactant per micelle. Further addition of solubilizate, to produce a saturation level in excess of 80%, results in a decrease in micellar size in both systems. The solubilization of ethyl p-hydroxybenzoate and p-hydroxybenzoic acid is thought to involve the oxyethylene region of the micelle and both solubilizates cause an increase in Mn owing to the inclusion of solubilizate into the micelle, the number of molecules of surfactant per micelle being unaffected by the solubilization process. Viscosity studies on the decane-ceto-macrogol-water system are interpreted as indicating no change in either micellar symmetry or hydration as a result of solubilization. A spherical model for the micelles is shown to be consistent with the experimental data.

Light scattering studies of the solubilization of some esters of p-aminobenzoic acid by lysophosphatidylcholine.

Light scattering equipment has been constructed using a vertically polarized helium-neon laser and a phase-sensitive detection system. The apparatus has been used to determine the micellar weight of lysophosphatidylcholine (LPC), giving values of 1.33 x 105 in water and 1.47 x 105 in 0.05 M sodium chloride; the sols showed some degree of polydispersity. The light scattering apparatus has also been used to study the solubilization by LPC of three n-alkyl esters of paraminobenzoic acid. These compounds caused a considerable increase in the scattered light, particularly at higher LPC concentrations.

The micellar weights of the series dioctyl-to-didodecyl phosphatidylcholine.

Journal Article The micellar weights of the series dioctyl-to-didodecyl phosphatidylcholine Get access W John Pugh, W John Pugh Department of Physical Chemistry, School of Pharmacy, University of London, Brunswick Square, London, WC1, UK Search for other works by this author on: Oxford Academic Google Scholar Leonard Saunders Leonard Saunders Department of Physical Chemistry, School of Pharmacy, University of London, Brunswick Square, London, WC1, UK Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 26, Issue 4, April 1974, Pages 286–288, https://doi.org/10.1111/j.2042-7158.1974.tb09277.x Published: 12 April 2011 Article history Received: 05 November 1973 Published: 12 April 2011

Ultrasonic irradiation of some phospholipid sols.

AbstractUltrasonic irradiation of turbid sols of egg lecithin and of highly unsaturated synthetic lecithins, breaks down the large particles in the sols into micelles of micellar weight of about 5 × 106. The irradiated sols are clear and do not show any great increase of turbidity over a period of several days; they are capable of solubilising large quantities of cholesterol. The size and shape of micelles in the irradiated sols has been studied by means of viscosity and diffusion measurements and by determination of sedimentation coefficients in the ultra-centrifuge.

Solubilization of Indomethacin by Polysorbate 80 in Mixed Water-Sorbitol Solvents

The effect of indomethacin on the micellar properties of the non-ionic surfactant, polysorbate 80, in water-sorbitol mixtures containing up to 25% w/v sorbitol has been investigated by light scattering, photon correlation spectroscopy and viscometric techniques. The molecular weight of polysorbate 80 micelles containing solubilized indomethacin increased linearly with increase of sorbitol concentration. Solubilization of indomethacin resulted in an increase of micellar weight due not only to the incorporation of solubilizate but also to an increase in the number of polysorbate molecules per micelle. The micelles in all systems were most satisfactorily represented as oblate ellipsoids, the asymmetry and hydration of which increased with increase of sorbitol concentration. Indomethacin solubilization caused a restructuring of the micelle to produce a more symmetrical micelle of increased hydration.

Effects of structural variations of non-ionic surfactants on micellar properties and solubilization: variation of oxyethylene content on properties of C22 monoethers.

Studies on erucyl alcohol ethoxylated with 40 and 47 units, and on behenyl alcohol ethoxylated with 33 and 43 units, gave values of 106, 101, 271, and 304 (all X 10(3)) for the micellar weight, 51,42,152, and 137 for the aggregation numbers, and 257,362,209, and 311 moles water mol-1 surfactant for the micellar hydration, respectively. Measurements of the solubilization of azobenzene, cortisone acetate, griseofulvin, sulphadiazine, phenylbutazone, betamethasone, tolbutamide, and menaphthone showed that the erucyl derivatives were better solubilizers than the behenyl compounds, and that solubilization increased as the polyoxyethylene chain was shortened; this change was more pronounced with the erucyl compounds.

Micellar size and surface activity of some C18 alpha-monoglycerides in benzene.

Abstract Some C18 α-monoglycerides in benzene have been studied by the light-scattering and surface tension methods. The glycerol esters of stearic, oleic and linoleic acids had micellar weights of less than 7,000; glycerol monoricinoleate had a micellar weight of over 18,000. All the mono-glycerides showed some surface activity in benzene, glycerol monoricinoleate having the greatest, the other unsaturated monoglycerides the least.

Laser light scattering evidence for a common wormlike growth structure of mixed micelles in bile salt- and straight-chain detergent-phosphatidylcholine aqueous systems: relevance to the micellar structure of bile.

We employed quasielastic and static light scattering to measure apparent values of the mean hydrodynamic radii (Rh)app, molecular weights (Mapp), and radii of gyration (Rg)app in solutions containing mixed micelles composed of bile salts (cholate and taurochenodeoxycholate, both cholanoyl derivatives) and the glycoacyl chain detergent, octyl glucoside, with egg yolk phosphatidylcholine (EYPC) as functions of total lipid concentration (0.1-10 g/dL), EYPC/detergent molar ratio (0-1.2), and ionic strength (0.15-0.4 M NaCl) at 20 degreesC and 1 atm. As the mixed micellar phase boundaries were approached by dilution, (Rh)app, Mapp, and (Rg)app values increased markedly by up to 20-fold. For each micellar system, the scaling ratios (Rh)app/Mapp1/2 and (Rg)app/(Rh)app remained essentially constant at 0.018 nm/(g/mol)1/2 and 1.5 (dimensionless), respectively, despite large variations in total lipid concentration, detergent molecular species, and ionic strength. Refined data analysis is inconsistent with a flat "mixed-disc" model for bile salt-EYPC micelles [Mazer, N. A., Benedek, G. B., and Carey, M. C. (1980) Biochemistry 19, 601] and octyl glucoside-EYPC micelles principally because the numerical value of (Rh)app/Mapp1/2 corresponds to a hypothetical disk thickness of approximately 1 nm, which is 4-fold smaller than the bimolecular width of EYPC molecules, and for a disk, (Rg)app/(Rh)app ratios should be close to 1 at low total lipid concentrations. Assuming disc-shaped micelles, we show that intermicellar excluded volume interactions would have only a minor effect on Mapp and cannot account for the unrealistic disk thickness. Instead, locally cylindrical, semiflexible wormlike micelles of diameter d = 4 nm and persistence length xip = 17 nm in solution are compatible with the observed (Rh)app/Mapp1/2 and (Rg)app/(Rh)app values when intermicellar excluded-volume interactions are considered. With EYPC/taurochenodeoxycholate = 0.6 and EYPC/cholate = 1.0 in 0.15 M NaCl, independent micelles grow upon dilution and use of the second virial coefficient [Egelhaaf, S. U., and Schurtenberger, P. (1994) J. Phys. Chem. 98, 8560] is adequate for estimating micellar weights. The systems EYPC/cholate = 1.0 in 0.4 M NaCl, EYPC/cholate = 1.2 in 0.15 M NaCl, and EYPC/octyl glucoside = 0.13 in 0.15 M NaCl all form highly overlapping, semidilute polymer solutions, which mimic the observed scaling ratios. In such semidilute systems, use of the second virial coefficient alone to account for intermicellar interactions is inadequate for estimating micellar weights. The results of the present study, in combination with locations of known phase boundaries of the ternary bile salt-EYPC-water phase diagram at high dilution, suggest that elongation, as well as entanglement of wormlike mixed micelles may occur at concentrations approaching the micellar phase limit.

Molecular characterization of a copolymer of 2-allylphenoxyorganocyclotriphosphazene with styrene, methyl methacrylate and vinylbenzyl chloride

The monomer 2-allylphenoxyorganocyclotriphosphazene was synthesized by reacting hexachlorocyclotriphosphazene with 2-allylphenol, phenol and 2,2,2-trifluoroethanol by phase transfer catalysis in a dichloromethane/alkaline solution. The copolymerizations of 2-allylphenoxyorganocyclotriphosphazene with styrene, methyl methacrylate and vinylbenzyl chloride were investigated. Nine copolymers of 2-allylphenoxyorganocyclotriphosphazene were identified in the solution. These copolymers were characterized by using light scattering, viscometry and 31P n.m.r. spectroscopic techniques. The micelles were observed to hydrodynamically and thermodynamically behave as impermeable spheres. The structure of the micellar shell was determined. The translational diffusion coefficient, Mark-Houwink constants, hydrodynamic radius, micellar weight, aggregation number, characteristic ratio and intrinsic viscosity were obtained. The chains of copolymer were observed to have a high degree of stiffness and a lack of rotational freedom in solution.

Fundamental Properties of Aqueous Solutions of Nonionic Surfactants Prepared from Oleic Acid of High Purity

Fundamental properties such as micellar weight, critical micelle concentration and cloud point were determined for aqueous solutions of polyoxyethylene (20) sorbitan monooleate (POESO) and polyoxyethylene (n) oleyl ether [POEOE and POE (10) 0E for n=20 and 10, respectively] recently prepared from oleic acid of high (>99%) and low purity. HPLC analysis and measurement of hydroxy value were conducted to clarify the distribution of the oxyethylene chain. For POESO and POEOE, no significant correlation between the above properties and oleic acid purity could be found. For POE (10) OE, however, the cloud point was higher for greater purity. This was confirmed by the temperature dependence of light scattering intensity.

Significance of β-sheet formation for micellization and surface adsorption of surfactin

It was found that surfactin, an anionic lipopeptide biosurfactant, forms large rod-shaped micelles (micellar weight, 179 000, aggregation number n = 173) having a critical CMC of 9.4 × 10 −6 M and a surface tension at the CMC γ CMC of 30 mN m −1 in 0.1 M NaHCO 3 (pH 8.7). This excellent surface-active behaviour was attributed to the ease of piling of surfactin molecules organized by β-sheet formation. Surfactin also showed a possible organization between molecules due to β-sheet structure at the air-water interface under forced experimental conditions.

Effect of chain length on the micellization and gelation of block copoly(oxyethylene/oxybutylene/oxyethylene) E mB nE m

Three triblock copoly(oxybutylene/oxyethylene)s, E 58B 17E 58, E 71B 28E 71 and E 132B 53E 132, with similar composition (75–80 wt% E) but different chain lengths, were prepared by sequential anionic copolymerization, and their micellar and gelation properties in aqueous solution were determined. The methods used were light scattering intensity, photon correlation spectroscopy and gel permeation chromatography, together with observation of gelation. Measurements were made at 30°C over the full concentration range from dilute solution into the gel. The lower and upper temperature boundaries of the gel regions were identified. Phase separation was observed in dilute solutions of the copolymer of longest chain length (E 132B 53E 132). Critical micelle and gel concentrations decreased markedly as chain length was increased, and micellar weights and sizes increased.

Micellisation and gelation of block-copoly(oxyethylene/oxybutylene/oxyethylene) E58 B17 E58

A triblock-copoly(oxybutylene/oxyethylene), denoted E58 B17 E58 (80 wt-% E), was prepared by sequential anionic copolymerisation and its micellar and gelation properties in aqueous solution were determined. The oxybutylene/oxyethylene copolymer had the advantage over comparable oxypropylene/oxyethylene copolymers of greater uniformity of composition and chain length. The methods generally used were surface tension, light scattering intensity, photon correlation spectroscopy, together with observation of gelation. Measurements were made at 30°, 40° and 55° C over a full concentration range from dilute solution into the gel (>200 g dm−3) and at specified concentrations, including the gel, over the temperature range from 10° to 70° C. The lower and upper temperature boundaries of the gel region were identified, and the occurrence of syneresis was noted. The properties investigated and discussed include critical micelle and gel concentrations, micellar weights and sizes, and structures and mobilities in the gel.

Association and surface properties of diblock and triblock copoly(oxyethylene/oxypropylene/oxyethylene)s

Oxyethylene/oxypropylene block copolymers were prepared with almost identical overall compositions (40 wt.% E) and molecular weights (Mn= 2900) but different block structures, i.e. diblock E26P29 and triblock E14P30E14. Their micellar and surface properties were studied by static and dynamic light scattering and surface tension. At a given temperature, the surface acitivity, the c.m.c., the molar micellar weight and the micellar size did not differ within the uncertainties of their determination. The only significant difference was in the area per molecule in the surface monolayer, wherein the diblock copolymer was more closely packed than the triblock copolymer.

Surface Active Properties of Heptyl β-d-Xyloside Synthesized by Utilizing the Transxylosyl Activity of β-Xylosidase

Abstract The surface-active properties of heptyl β-d-xyloside were investigated. The critical micelle concentration of this surfactant was determined to be 30 mM (M=mol dm−3). The corresponding molecular area at saturation adsorption, the micellar weight and the aggregation number were 43 Å, 20700 and 78, respectively. This surfactant was found to have a surface activity similar to that of octyl β-d-glucoside.

Block copolymer micelle solutions: 1. Concentration dependence of polystyrene-poly(ethylene propylene) in heptane

The concentration dependence of micelle formation by a diblock copolymer of polystyrene-poly(ethylene propylene) (PSPEP) in n-heptane is examined by turbidity, viscosity and photon correlation spectroscopy (p.c.s.). The critical micelle concentration (c.m.c.) as determined by p.c.s. is estimated to be 0.002 wt%. At c = 0.003%, an unusually large hydrodynamic radius is found, in agreement with the anomalous increase in hydrodynamic size near the c.m.c. previously reported by Tuzar et al. in 1985. The average micellar weight obtained from turbidity measurements and the hydrodynamic radius for non-interacting micelles as measured by p.c.s. were relatively constant for c = 0.01–0.5%. A comparison of the second virial coefficients from the turbidity and viscosity measurements suggests that the relatively large Huggins constant of k H = 2.4, obtained from viscosity measurements, may be explained in terms of an excluded-shell model. At a critical concentration above 0.5%, an increasing amount of freely dispersed polymers is present in the solution. The driving force for this change in the free chain-micelle equilibrium is believed to arise from the concentration gradient of PEP segments between the micelle corona and the dispersed phase. The amount of free chains relative to micelles is found to increase from 0.7% up to 2% based on p.c.s. results. It is not clear, however, if the equilibrium is further shifted in favour of the free chains from 3 to 5%, since the weight fractions of free chains and micelles cannot be deduced from p.c.s. data at such high concentrations. However, turbidity and viscosity data seem to suggest that the relative amount of free chains at 3% is lower than that at 2%. At even higher concentrations (4–5%), the viscosity of the micelle solutions increases drastically, presumably because of the formation of a macrolattice.

Mixed micelles of alkyltrimethylammonium bromides and chlorhexidine digluconate in aqueous solution

The size and composition of the micelles in mixtures of dodecyl- and tetradecyltrimethylammonium bromide (DTAB and TTAB); TTAB and hexadecyltrimethylammonium bromide (CTAB); DTAB and CTAB; and binary mixtures of each of these alkyltrimethylammonium bromides with the dicationic surfactant chlorhexidine digluconate (CG), have been determined as a function of the composition of the mixed systems. Application of a theoretical treatment based on excess thermodynamic quantities to critical micelle concentration (CMC) data from conductivity measurement gave micellar compositions in agreement with those derived from an empirical treatment of the conductivity results and from direct determinations by gel filtration chromatography. Static light scattering studies have shown that chlorhexidine digluconate forms small aggregates in solution (approximately 4 monomers per micelle) and that the micellar weight of mixed TTAB-CG micelles is determined essentialy by the composition of the mixed system.