A viscometric study of the micelles of sodium dodecyl sulfate in dilute solutions

Abstract

The viscosities of solutions of sodium dodecyl s ulfate of concentratio ns up to 0.8 per ce nt in distilled water and in 0.01-to 0.12-iVI sodium chloride have been measmed . By int roducing t he concept of a m onomer saturation concentration i t is possible to determi ne t he intrinsic viscosity of the micelles at each concentratio n of sodium chloride. A method for t he experiment a l determination of the monomer saturation concent ration is prese nted. The dependence of t he intrinsic viscosity on the sal t concent rat ion is disc ussed in te rms of eJectrovi sco us a nd hy dration effects . The data indicate tile presence of spherical micelles in t he solu t ions investigated. Introd u ctionSince th e early exp erimen ts of . K rafft [1]1 and McBain [2] on soap solu tions, and th e subscqucnt intcrpretaLjon of th ejr r es ults in terms of th e existence of micelles i n su ch solutions, m any r esearch es [3, 4] h ave b een under ta ken. to investigate th e size and shape of these particles . It is now generally assumed that th ere are at least two types of micelles .In th e concentration range b eL",veen th e onset of micelle formation (about 0.1 to 0.25 percent by weight) and a~out 1 to 2 p er cent! a s~all, highly charo·ed and hIghly conductll1g mlCelle I S though t t o e~ist. This typ e of micelle h as b een discussed at some len.gth by Hartley [5,6]. H e considered them as spher es, but th ere has been 1~0 general ~gree nient on th eir shape. A large mIcelle, havmg a structure discernible by X-ray diffraction, exists at high er concentrations (about 10 pOl·cen t 0:· gr eater). They h ave been diseussed and mvestigated by M cBain [2], H ess [7], Philippoff [8], and others [9]. Harkins [1 0] and his coworkers interpret th eir lat~r X-ray diffraction data for co ncentrated solutJOns III terms of cylindrical micelles. Brady [11], however, utilizing a treatment considered b y 90r1"1n [12], interprets hi~ da~a for concentrate~ sodlUm d<?decyl sulfate solutIOns m terms of a radial dIstnbu tIOn of sphOl'ical. micelles. Recent light-scattering investigations by Debye [13] indicate that in the presence of higb concentrations of electrolyte, the mIcelles of h exadecyl trimethyl ammonium bromide are rodlike.Th e purpose of this r esearch was to invest igate the viscometric b ehavior of dilute solutions of a pure, well-defined detergent, sodium dodecyl sulfate. Detergent concentrations up to 0.8 per cent by weio·h t were used. Distilled "lvater and 0.01 to 0.12 M ~odiLlln chloride solutions were used as solvents. MaterialsThe· soc!ium dodecyl sulfate was synthesi~ed., as described by Sh ecllovsky [14], from a vacuum-dlstlll~d s~mple of n-dodecyl a~cohol. .T~e c~lorosu~fol1J c acid used in the synthesls was chstllledl1nmedlately befor e use. All other reagents u sed in the synthesis and subsequent purification conformed '\vith Ameri- can Chemical Society specifications. Prior to making up solutions for the measurements, the detergent was extracted with diethyl eth er for about 8 hI' III a Soxhlet extractor.After a m...

Exploring hydrophobicity limits of polyproline helix with oligomeric octahydroindole‐2‐carboxylic acid

“…As seen from the diffusion (Figure A) of the detergent, the micelle formation was overall not perturbed by the presence of the peptides except for the samples close to the CMC (5 and 10mM), where the most hydrophobic peptides slowed down the detergent diffusion. The peptide diffusion coefficients log D are indicative of the individual particle sizes, and these can be relatively well calculated using previously derived Equation assuming water viscosity, since presence of SDS changes water viscosity only slightly . The monomeric peptide diffusion was calculated using peptide molecular weights, whereas the whole micelle diffusion was calculated assuming SDS micelles composed of 64 anions and complete inclusion of the peptide (see Section 2.3.3).…”

“…The peptide diffusion coefficients logD are indicative of the individual particle sizes, and these can be relatively well calculated using previously derived Equation 1 29 assuming water viscosity, since presence of SDS changes water viscosity only slightly. 62 The monomeric peptide diffusion was calculated using peptide molecular SCHEME 2 Preparation of the oligomeric peptides (oligo-Oic) At the SDS concentrations 1 to 2mM (below the CMC) all the peptides were found in the monomeric form in the aqueous solution ( Figure 5B). Increase of the detergent concentration did not affect the peptide diffusion in the case of the hexaproline references, showing that the peptides are residing in the aqueous phase.…”

Phase and rheological behavior of the polymerizable surfactant CTAVB and water

“…There are several reports that the viscosity of water is reduced by the addition of surfactants in the premicellar range [28][29][30]. That the viscosity of surfactant solutions is lower than that of water below the cmc can be explained in terms of the theory developed by Némethy and Scheraga about hydrophobic hydration cages [31,32].…”

Phase and Rheological Behavior of Cetyldimethylbenzylammonium Salicylate (CDBAS) and Water

“…At low surfactant concentrations below the cmc, the viscosity decreases slightly with increasing concentration and it is smaller than the viscosity of pure water. There are several reports about the reduction of water viscosity due to the addition of surfactants in the premicellar range [56][57][58]. This behavior was explained in terms of the theory developed by Némethy and Scheraga [59,60].…”