Amine Oxides: A Review - J-Stage

1 Introduction

Although, amine oxides were known and studiedbefore 1900, it was not until 1939, with the issuance ofan I.G. Farbenindustrie patent that material such asdimethyldodecyl amine oxide were recognized as sur-factant. After a further 22 years their utility in liquidhousehold formulations was disclosed and widespreadinterest was generated. The substitution for the tradi-tional fatty alkanolamides as foam booster in dishwash-ing was the specific example which brought recognitionto the amine oxides. Their favourable weight/effectratio offsets the considerably higher cost in this applica-tion (1).

Reaction of hydrogen peroxide with secondary orprimary amines does not result in commercially usefulmaterials (2), but with tertiary amines a variety of com-mercial useful materials obtained which are used notonly in various types of cleaning formulations but also,proving their utilities in liquid bleach products (surfac-tant basis), textile industry (anti-static agent), rubberindustry (foam stabilizer), polymer industry (polymer-ization catalyst), anti-corrosion compositions, lime soap

dispersant, and in deodorant bars (anti-bacterial agent),due to their compatible synergistic effect and environ-ment friendly nature. Amine oxides are exothermic,second order reaction products of tertiary amines andhydrogen peroxide (3). The nature of tertiary amine inamine oxides may be aliphatic, aromatic, heterocyclic,alicyclic or combination thereof. In current amineoxides the surfactant precursor is generally a C12 - C18

alkyldimethyl amine (4).Amine oxides come under the special class of surfac-

tant known as amphoteric surfactant. The basic reasonbehind that is, amine oxide changes from net cationicvia zwitterionics to nonionics on going from low tohigh pH; which confirms it’s amphoteric nature.

This paper presents a detailed review on amineoxides, with special emphasis on the chemistry of oxi-dation, physico-chemical studies, various applicationsand anti-microbial activity with variation in chainlength. The last part of this paper is briefly focused onthe safety of amine oxides.

99

＊Correspondence to: V.K. TYAGI, Department of Oil and Paint Technology, Harcourt Butler Technological Institute, Kanpur - 208002, INDIA

E-mail: [email protected], [email protected]

JOS

Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online

http://jos.jstage.jst.go.jp/en/

Sudhir Kumar SINGH, M. BAJPAI and V.K. TYAGI＊

JOURNAL OF OLEO SCIENCECopyright ©2006 by Japan Oil Chemists’ SocietyJ. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Abstract: Amine oxides are amine-based surfactants, represent one of the smaller classesof surfactants as compared to alcohol ethoxylates and sulfonated and sulfated anionicsurfactants. However, the uniqueness of the hydrophile in such surfactants provides specificproperties that are difficult, if not impossible, to replicate by the use of classic nonionic andanionic surfactants. The aim of the present paper is to survey the most important developmentsand understandings of the chemistry of amine oxide production, it’s physico-chemical studies,applications and environmental properties.

Key words: amine oxide, amine-based surfactant, hydrophile, physico-chemical,environmental

REVIEW

Amine Oxides: A Review

Edited by M. Iwahashi, Kitasato Univ., and accepted September 20, 2005 (received for review August 29, 2005)

Department of Oil and Paint Technology, Harcourt Butler Technological Institute (Kanpur-208 002, INDIA)

S.K. Singh, M. Bajpai and V.K. Tyagi

2 The Chemistry of Oxidation for Amine

Oxide Formation

The generally accepted mechanism for oxidation oftertiary amines with hydrogen peroxide involves theammonium peroxide as an intermediate followed bysplitting off water. Previous work (3) strongly suggeststhe reversibility of the formation of the ammonium per-oxide. The proposed mechanism is as follows:

From the above proposed mechanism, the rate of for-mation of amine oxide can be derived; using “steady-state approximation”. The rate of formation of amineoxide can be written as,

･･･････････････････（I）

Since, the concentration of intermediate is so smallthat it can’t be measured, so, it has to be replaced by theconcentrations that can be measured.

From proposed mechanism we have,

･･(II)

Now, because the concentration of (R3N. H2O2)* isalways extremely small, one may assume that it’s rateof change be zero {This is called “steady-state approxi-mation” (5)}.

Hence, ･･･････････････････････････(III)

From equations (I), (II) and (III) we get,

or････････････････････(IV)

where K is overall rate constant and K = k1k3 / (k2 + k3)So, from equation (IV) it is evident that overall order

of reaction for amine oxide formation is 2, and is incomplete agreement with the experiment.

It has been observed that the degree of conversion oftertiary amines to its amine oxides is dependent on thepurity of the tertiary amines. With commercially avail-able undistilled tertiary amine yields in the range of85% to 87% are obtained. But with freshly redistilledtertiary amine and with 10% molar excess hydrogenperoxide the yield may go upto 99% (1).

During the synthesis of amine oxides information onthe amount of unreacted tertiary amine present is need-ed in order to follow the reaction. A number of analyti-cal procedure including chromatographic procedureshave been devised to obtain this information. But all ofthese procedures have some limitations. Wang and Met-calfe (6) developed a simple, rapid, non aqueous titra-tion procedure that makes use of the “anamalous salt”behaviour of amine oxides. A modified solvent andtitrant is used to obtain two potential breaks in the titra-tion. The first break corresponds to half of the amineoxide. The second break represents the second half ofthe amine oxide plus any unreacted amine. With thisinformation the amine oxide and unreacted amines canbe calculated.

3 Synthesis of Amine Oxides

3･1 Synthesis of Dimethylalkyl Amine

Oxides and Cyclic Amine Oxides

Friedli et al. (3) prepared dimethyllauryl amine oxide,N-laurylmorpholine oxide, N-laurylpiperidine oxideand N-lauryl-3- methyl piperidine oxide with theirrespective amines by reacting with 51% aqueous hydro-gen peroxide at 75℃. Their rates of formation indicatesthat the reaction is of second order and two piperidineversions form slower than dimethyl-lauryl amine oxide,while lauryl morpholine reacts much faster.

3･2 Synthesis of 2-alkoxy-N, N-

dimethylethyl Amine N-oxides

Hayashi et al. (7) prepared 2-lauryloxy-N,N-dimethylethyl amine N-oxide with it’s amine by react-ing with 30% aq hydrogen peroxide at room tempera-ture. The amine oxide was concentrated in a drying boxunder reduced pressure resulted into a crystalline solidamine oxide. Such amine oxides are stable up to 100℃,but decomposes rapidly to vinyl ethers at 150℃. At lowtemperature they deoxygenated to their tertiary amine.Hygroscopic property decreases as length of the alkylchain increases.

3･3 Synthesis of Alkyl Benzene Derived

Amine Oxides

Marmer and Linfield (8) prepared aromatic amineoxides via a three step route from a variety of pure 1-phenylalkanes and also from a commercial detergentalkylate mixture. The process includes (i) sulfonation of

γ R NO K R N H O3 3 2 2= [ ][ ]

γ R NO

k k R N H O

k k3

1 3 3 2 2

2 3

= [ ][ ]+

γ R N H O3 2 20..( )∗ =

γ R N H O k R N H O k R N H O

k R N H O

3 2 2 1 3 2 2 2 3 2 2

3 3 2 2

. .

.

( )∗= [ ][ ] − [ ]∗− [ ]∗

γ R NO k R N H O3 3 3 2 2( ) = [ ]∗.

R N H O R N H O R NO H O3 2 2 3 2 2 3 2+ ⇔ ( )∗ → +.k1 k3

k2 rxn.intermediate

100J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)


the phenylalkane with chlorosulfonic acid in 1,2-dichloroethane. (ii) reaction of resulting alkarylsulfonylchloride with H2N(CH2)3NMe2 (Me is for -CH3 group)or H2N(CH2)3N(CH2CH2OH)2 under anhydrous condi-tions at room temperature, and (iii) oxidation of result-ing tertiary amines with 30% aqueous hydrogen perox-ide at 65℃. Such aromatic amine oxides were found tobe thermally stable below 125℃.

3･4 Synthesis of N, N-dimethylalkyl Amine

N-oxide by Micellar-Autocatalysis

Rathman and Kust (9) investigated the synthesis ofN,N-dimethyldodecyl amine N-oxide in aqueous solu-tions by micellar autocatalysis. The lipophilic reactant,dimethyl dodecylamine was initially solubilized inmicellar solutions of the amine oxide surfactant, result-ing in substantially higher reaction rates. Amine con-versions of 90-100% were obtained within 2 h at 70℃.The effects of reactant concentrations, temperature, andinitial surfactant concentration were studied. Thismethod is important because of two main reasons: (I)Micellar auto catalysis provides a method for synthesiz-ing surfactants without employing volatile organic sol-vents in the reaction medium, providing potential eco-nomic and environmental benefits and (II) studies ofmicellar auto catalysis can refine and extend the under-standing of the other types of reactions in aqueous sur-factant solutions.

4 Analysis of Amine Oxides

Pinazo and Domingo (10) investigated turbidimetricanalysis of amine oxides and amine oxide - anionic sur-factant mixtures. This automatic analysis has beenshown to be a simple and accurate method to determinethe actives in anionic surfactants as well as the activesin amine oxides. This technique has been applied todilute solutions of these surfactants in the mM range.

Turney and Cannell (11) determined a method knownas alkaline methylene blue method for determination ofanionic surfactants, also this method in conjunctionwith the acid methylene blue titration may be used todetermine the amount of amine oxides in formulatedproducts like detergents etc, based on the cationicnature of amine oxides at low pH and nonionic nature athigh pH. For concentrations of less than 100 PPM aspectrophotometric method was used.

5 Physico-Chemical Studies on

Amine Oxides

It is well known that the dissociation constant K ofweak electrolytes at the charged interface are differentfrom those in their solutions. Funasaki (12) were meas-ured the dissociation constant K of acid -base indicatorsin aqueous solutions of 20 mM dodecyldimethyl amineoxide (DDAO), 1% Brij 35 (C12H25-(O-CH2-CH2-)23-OH), and 20 mM cetyltrimethylammonium bromide(CTAB) spectroscopically and also determined theapplicability of the equation pK = pKi－ (0.4343 e0y0/kT),to the micelle-solubilizate systems. The surface poten-tial Y0 of mixed micelles of sodium dodecyl decaoxyethylene sulfate and dodecyldimethylamine oxide in thepresence of 0.1 M sodium chloride at 25℃ have foundby Tokiwa and Ohki is somewhat unreasonable.Funasaki (13) evaluated more reasonably the surfacepotential of these mixed micelles.

It has been known that micelle of ionic surfactantsgrows with increasing concentration of added salt. Theelectric repulsion between charged headgroups is amain size - limiting factor in micelle formulation, andthe effect of added salt on the micele size has been

101J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 1 Molecular Structures of Respective Amine Oxidesof Section 3.


attributed to the electrostatic shielding effect of counter-ions on the charged micelle. Ikeda et al. (14) studied the effects of ionization on micelle size of aqueousNaCl solution of dimethyldodecyl amine oxide, byusing the light-scattering method for the determinationof molecular weight, from the Debye plot.

Imae and Ikeda (15) measured angular dependence oflight-scattering from micellar solutions of dimethyl-oleyl amine oxide in water and 10-4 M NaCl at differentmicelle concentrations from the critical micelle concen-tration (CMC) to 0.15 × 10-2 g cm-3. The intensity oflight scattered from the micellar solutions increaseswith an increase in scattering angle, in contrast to theusual behaviour. This is caused by the effect of externalinterference which is stronger than that of internal inter-ference.

Dimethyldodecyl amine oxide and dimethyltetrade-cyl amine oxide are known to form spherical micellesin water and 0.20 M NaCl solutions; but, if the hydro-carbon part of nonionics with amine oxide head groupis made longer for e.g. dimethyloleyl amine oxide,forms rod like micelles in dilute aqueous solutionsdetermined from light-scattering measurements. RitsuKamiya et al. (16) presented electron micrographs ofrod like micelles regenerated from aqueous solutions ofdimethyloleyl amine oxide and gave support for theresults from the light scattering measurements.

Imae and Ikeda (17) investigated the pH dependenceof upper and lower consolute phase boundaries foraqueous NaCl solutions of dimethyloleyl amine oxideat temperatures between 5 and 85℃ for pH less than 8at different NaCl concentrations. The consolute phaseboundary is also given as a function of surfactant con-centration. Toyoko Imae et al. in their another investi-gation (18) found that aqueous solutions of dimethyl-alkyl amine oxides (CnDAO, n = 16,18) present the iri-descence at surface concentrations of 0.3 - 2 wt%, whenthe temperature of the solutions is lower than 23℃ forC16 DAO and 46℃ for C18 DAO. The Colour changesfrom yellowish red to blue with an increase in surfac-tant concentration, and disappears at pH below Ca. 6.5 for C16 DAO and below Ca. 4.5 for C18 DAO (seeFigs. 2 & 3).

Polymer-micelle complexes have found applicationsin many industrial products, such as paints and coat-ings, laundry detergent, and cosmetic products and theyalso play a role in tertiary oil recovery. Brackman andEngberts (19) studied the influence of the nonionic

water soluble polymers poly (vinyl methyl ether)(PVME), poly (propylene oxide) (PPO), and poly (ethy-lene oxide) (PEO) on the aggregation behaviour of n-dodecyldimethyl amine oxide (DDAO), at variousstages of protonation.

Hoffman et al. (20) reported the phase diagram of theternary surfactant system tetradecyldimethyl amineoxide / heptanol / water for small surfactant concentra-tions. With increasing cosurfactant / surfactant ratio, thegenerally observed sequence of the phases L1, La andL3 is found. These single phases are separated by nar-row two phase regions. In all these phases the L3 or so-called sponge phase has drawn much attention. It is alow viscous, slightly turbid, and optically isotropic

102J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 2 The Phase Diagram under the Visual Inspection forAqueous Solutions of C16 DAO. I, Transparent andIsotropic Solution; II, Turbid Solution; III,Iridescent Solution.Reprinted from J. Colloid Interface Sci., Vol. 131, 601-602,

Copyright with permission from Elsevier.

Fig. 3 The Phase Diagram under the Visual Inspection andthe Crossed Nicol for Aqueous Solutions ofC18DAO.――, visual inspection; ―-―-―-―,crossed nicol. I, transparent and isotropic solution;II, turbid solution; III, iridescent solution; IV,weakly birefringent solution; V, stronglybirefringent solution.Reprinted from J. Colloid Interface Sci., Vol. 131, 601-602,



phase which shows flow birefringence under shear.The interactions between water and nonionic surfac-

tants are important in both fundamental and appliedsurface chemistry. Mol et al. (21) determined the struc-tural parameters of the hexagonal and lamellar phase ofthe dimethyldodecyl amine oxide (DDAO)- water sys-tems using X-ray diffraction. The result obtained arediscussed in the light of the on going debates about (i).The relative importance of steric / protrusion forces andhydration forces between surfactant bilayers and (ii) themolecular origin of the temperature dependence of theinteractions displayed in several nonionic water sys-tems.

The electrostatic potential is one of the importantfactors for the stabilization of dispersed colloidal parti-cles in aqueous medium. The electrokinetic phe-nomenon such as electrophoresis, which may be evalu-ated by mobility, is in close connection with electrostat-ic potential. Imae and Hayashi (22) performed elec-trophoretic light scattering measurements for aqueousNaCl solutions of dodecyl-, tetradecyl-, andoleyldimethyl amine oxides (C12DAO, C14DAO &ODAO). It was observed that Electrophoretic mobilitychanged with the degree of protonation (see Figs. 4 to7).

It is very interesting to investigate the behaviour ofsurfactant mixtures, which have different head groupswith synergistic interactions but also different chainswith antagonistic interactions. Hoffman and Possnecker(23) investigated the mixing behaviour of surfactants byusing the phase separation model. In their investigationthey used pairs of nonionic hydrocarbon surfactants andperfluorinated anionic surfactants; in one example theytook the tetradecyldimethyl amine oxide as nonionicsurfactant with the mentioned anionic surfactants. Withthis anionic surfactant it was possible to reach nearlyidentical CMC values of the nonionic and the anionicsurfactant. To create special starting conditions, theyused a hydrophobic tetraethyl ammonium counterion ofthe anionic surfactant (see Figs. 8 & 9).

Desnoyers et al. (24) studied the thermodynamicmicellar properties of n-octyldimethyl amine oxidehydrochloride (OAO.HCl) in water. The apparent molarvolumes and heat capacities of OAO. HCl were meas-

103J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 4 Electrophoretic Light Scattering Power Spectra for0.1 M NaCl Solutions of C14DAO at SurfactantConcentration of 0.5×10-2 g cm-3 with VariousDegrees of Protonation.Reprinted from Langmuir, Vol. I, 3385-3388, Copyright with

permission from Am. Chem. Soc.

Fig. 5 Electrophoretic Mobility as a Function of Degree ofProtonation for 0.1 M NaCl Solutions of C14DAO atSurfactant Concentration of 0.5×10-2 g cm-3.Reprinted from Langmuir, Vol. I, 3385-3388, Copyright with


Fig. 6 Electrophoretic Mobility as a Function of Degree ofProtonation for 0.03 M NaCl Solutions of ODAO atSurfactant Concentration of 0.1×10-2 g cm-3.Reprinted from Langmuir, Vol. I, 3385-3388, Copyright with



ured in water as a function of concentration between 2and 55℃ and the apparent molar relative enthalpies ofthe same system at 25℃. Also, the apparent molarexpansibilities were calculated from the temperaturedependence of the volumes (see Figs. 10 to 14).

Okamura et al. (25) investigated supramolecularassemblies in ternary systems of alkyldimethyl amineoxide (CnDAO, n=12, 16)/Cinnamic acid/ water bysmall angle neutron scattering(SANS). The fine struc-tures of molecular assemblies were quantitativelyexamined for solutions with different mixing ratios.Since SANS is operated at the neutron radiation of 1-16 Å wavelength, it results in distances of nanometerscale such as the shape of small micelles, the crossec-tion of rod like micelles, and the lamellar thickness anddistance. Such data have never been obtained fromTEM and light scattering experiment. The moleculararrangement in supramolecular assemblies is discussedin relation to the structure geometry (see Figs. 15 to20).

The influence of thermodynamic parameters on themechanism of self-organization of surfactants in aque-ous solutions are of deep interest giving a deep insightinto the “new science of complex fluids”. The rich phasebehaviours of complex fluid systems is associated withthe fact that particles are molecular aggregates ratherthan simple molecules. The aggregates are thermody-namically stable structures, which change their size andshape in response to changes in concentration, compo-sition, counterion species, temperature, pressure andother conditions. Garski et al. (26,27) studied by meansof small angle neutron scattering (SANS) experiments,

the dependence on concentration and temperature (26),and pressure (27) of the mean aggregation number (N)of rodlike tetradecyldimethyl amine oxide micelles inD2O. Small angle scattering with neutrons (SANS) orwith X-rays (SAXS) is one of the most direct methodsfor obtaining information about structural details andtheir changes and also may help to clarify the resultsobtained by other experimental techniques. The combi-nation of pressure, temperature and SANS or SAXS inthe study of physical properties of micellar systemsopens up new prospects for examining amphiphilicsolutions on a microscopic level.

Zimmerman and Schnaare (28) extended the methodof Rathman and Christian for determining the micellaractivities of dimethyldodecyl amine oxide by pH titra-tion in the presence of swamping electrolyte to accom-modate non swamping electrolyte conditions.Dimethyltetradecyl amine oxide was used as a model

104J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 7 Electrophoretic Mobility as a Function of Degree ofProtonation for 0.05 M NaCl Solutions of C12DAOat Surfactant Concentration of 10-2 g cm-3. Squaresigns are data for 0.1 M NaCl solutions of C12 DAO.Reprinted from Langmuir, Vol. I, 3385-3388, Copyright with


Fig. 8 Plot of the Surface Tension vs the Logarithm of theTotal Surfactant Concentration of the System (I)C14DMAO/NEt4-PFOS in 10 mM NEt4OH Solutionat Different Mixing Ratios C14DMAO/NEt4

PFOS: a, 9:1; b,7:3; c, 3.5:6.5; d, 2:8.Reprinted from Langmuir, Vol. 10, 381-389, Copyright with


Fig. 9 cmc as a Function of the Mole Fraction a ofNEt4PFOS for the Mixtures (I) C14DMAO/NEt4

PFOS in 10 mM NEt4OH Solution.Reprinted from Langmuir, Vol. 10, 381-389, Copyright with



surfactant in this study. Amine oxide surfactants exist insolution either as the unprotonated, electrically neutralZwitterionic form (AO±) or as the protonated, cationicform (HAO+).

Myrzakozha et al. (29) reported the molecular orien-tation and structure in one and multilayer Langmuir -Blodgett (LB) films of octadecyldimethyl amine oxide(C18 DAO) and dioctadecyldimethyl ammonium chlo-ride (2C18DAO) on gold and silver-evaporated glassslides. It was found that the structures of LB films showclear dependence upon the number of monolayers andsubstrates. The most important finding was that the ori-

entation and order of alkyl chains in the first layers arechanged largely upon the deposition of the second lay-ers. In their another investigation (30), they reported the

105J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 10 Apparent Molar Volumes of OAOHCl at VariousTemperatures; Full Lines are from the Mass-ActionModel.Reprinted from Langmuir, Vol. 11, 1905-1911, Copyright

with permission from Am. Chem. Soc.

Fig. 11 Apparent Molar Heat Capacities of OAOHCl atVarious Temperatures; Full Lines are from theMass-Action Model.Reprinted from Langmuir, Vol. 11, 1905-1911, Copyright


Fig. 12 Apparent Molar Expansibilities of OAOHCl andOAO at 25℃; Full Lines are from the Mass-ActionModel.Reprinted from Langmuir, Vol. 11, 1905-1911, Copyright


Fig. 13 Apparent Molar Relative Enthalpies of OAOHCl,OAO, and OABr at 25℃; Broken Lines are fromthe Mass-Action Model.Reprinted from Langmuir, Vol. 11, 1905-1911, Copyright


Fig. 14 Temperature Dependence of Volume Parameters ofOAOHCl and OAO from the Mass-Action Model;＋’s are from the Second Series of Measurements.Reprinted from Langmuir, Vol. 11, 1905-1911, Copyright



thermal behaviour of the one - and five - monolayer LBfilms of C18DAO and 2C18 DAC on the gold and silverevaporated glass slides. It has been generally recog-nized that the interaction between a head group and asubstrate and the longitudinal interaction betweenmonolayers are two important factors which control thethermal stability of LB films. LB films have been amatter of keen interest because of their fundamentalimportance in surface science as well as their potentialapplication in optoelectronics.

Because the elucidation of the relationship betweenthe structure and function of the films is essential forboth basic studies and applications, structural character-

ization has been made for LB films of various com-pounds from simple fatty acids to complicated organicdyes by use of IR, UV-Vis, and Raman spectroscopiesand atomic force microscopy (AFM). Structuralchanges in the films induced by aging, doping andvariations in pH and temperature have also beenexplored extensively. Myrzakozha et al. (31) presentedan IR study of structure and aging -behaviour of one-layer LB films of C18DAO and 2C18DAC. The IR meas-urements suggests that the alkyl chains of one-layer LB film of C18DAO on a gold-evaporated glass slides

106J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 15 SANS Data for the C12DAO/Cinnamic Acid/D2OSystem. Mixing Ratio: ○, X=0; ●, X=0.2; △,X=0.4; ▲, X=0.6.Reprinted from J. Colloid Interface Sci., Vol. 180, 98-105,


(“Q” is Bragg wave number and “I” is SANS intensity)

Fig. 16 Replots of SANS Data for the C12DAO/CinnamicAcid/D2O System at Mixing Ratios X=0 and 0.2.Reprinted from J. Colloid Interface Sci., Vol. 180, 98-105,



Fig. 17 Replots of SANS Data for the C12DAO/CinnamicAcid/D2O System at Mixing Ratios X=0.45. 0.6and 1.Reprinted from J. Colloid Interface Sci., Vol. 180, 98-105,



Fig. 18 SANS Data for the C16DAO/Cinnamic Acid/D2OSystem. Mixing Ratio: ●, X=0; ○, X=0.2; ▲,X=0.4; □, X=0.6.Reprinted from J. Colloid Interface Sci., Vol. 180, 98-105,




have some gauche conformers i.e., less ordered thanthat of 2C18 DAC. It was also noted that the molecularorientation and structure in the film showed strong pHdependence, presumably because of the strong interac-tion between the headgroups and the substrates (seeFigs. 21 to 26).

Kato and Imae (32) investigated the surface forcesbetween glass surfaces in aqueous hexadecyldimethyl

amine oxide (C16DAO) solutions at different surfactantconcentrations and upon addition of cinnamic acid orHCl. The variation of surface forces depending on theconditions is discussed, concerning the adsorptionstructure of C16 DAO on glass surfaces. Also, the inter-surface interaction forces are compared with the forceswhich act in molecular assemblies in solutions.

Fukada et al. (33) investigated the lyotropic phasebehaviours of the nonionic and cationic (protonated)forms of dodecyldimethyl amine oxide (DDAO). Phasediagrams for DDAO + water, hydrochlric acid salt ofDDAO (DDAOHCL) + water and an equimolar mixtureof DDAO and DDAO HCl, (DDAO (1/2) HCl) + watersystems were determined on the basis of polarized lightmicroscopy, small angle x-ray diffraction, and differen-tial scanning calorimetry. Also, water activity was meas-ured to see the non ideality of water in lyotropic liquidcrystaline phases.

Kiraly and Findenegg (34) determined the materialand enthalpy balances of adsorption of the N,N-dimethyldecyl amine N-oxide (C10DAO) and n-octyl b-D-monoglucoside (C8G1) from dilute aqueous solutionsonto hydrophilic silica glass and hydrophobic graphite(graphitized carbon black) at 298.15 K up to the criticalmicelle concentration. An automated flow sorption/microcalorimeter system was used for simultaneousmeasurements of the adsorption isotherm and theenthalpy isotherm of displacement.

Barlow et al. (35) studied the internal structure of oil-in-water microemulsion dropletes by SANS using con-trast variation. The single chain surfactant used was N,N-dimethyldodecyl amine N-oxide, and the oil phasewas one of two semipolar ethyl esters, ethylhexade-canoate or ethyl octanoate.

Clays are added to many emulsions designed forindustrial applications. During the emulsification sur-face active agents adsorb onto clay and producehydrophobic colloids. Adsorption of surfactant ontoclays is also of interest for environmental issues andenhanced oil recovery. Studies of clay - surfactant inter-actions deal with ionic and neutral compounds. Geversand Grandjean (36) studied that 7Li and 23Na NMRspectrum of clay suspension in water have shown howthe smectite structure and nature of alkali counterionsmodulate the quadrupolar interaction. These probes,together with 13C and 2H nuclei, have been also used tostudy the interaction of dodecyldimethyl amine oxidewith laponite and differently charged saponites dis-

107J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 19 Replots of SANS Data for the C16DAO/CinnamicAcid/D2O System at Mixing Ratios X=0 and 0.2.Reprinted from J. Colloid Interface Sci., Vol. 180, 98-105,



Fig. 20 Replots of SANS Data for the C16DAO/CinnamicAcid/D2O System at Mixing Ratios X=0.4, 0.6, and1.Reprinted from J. Colloid Interface Sci., Vol. 180, 98-105,




108J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 21 (a) An IR RA Spectrum of One-Layer LB Film ofC18DAO on a Gold-Evaporated Glass Slide. (b) AnIR Transmission Spectrum of a One-Layer LBFilm of C18DAO on a CaF2 Plate. (c) An IR/ATRSpectrum of a One-Layer LB film of C18DAO on aGe Prism.Reprinted from Langmuir, Vol. 15, 6890-6896, Copyright


(Aqueous subphase at pH 5.8)

Fig. 22 (a) An IR RA Spectrum of One-Layer LB Film of2C18DAC on a Gold-Evaporated Glass Slide. (b)An IR Transmission Spectrum of a One-Layer LBFilm of 2C18DAC on a CaF2 Plate. (c) An IR/ATRSpectrum of a One-Layer LB Film of 2C18DAC ona Ge prism.Reprinted from Langmuir, Vol. 15, 6890-6896, Copyright


(Aqueous subphase at pH 5.8)

Fig. 23 (a) An IR RA Spectrum of an Aged One-Layer LBFilm of C18DAO on a Gold-Evaporated GlassSlide. (b) An IR Transmission Spectrum of anAged One-Layer LB Film of C18DAO on a CaF2

Plate. (c) An IR/ATR Spectrum of an Aged One-Layer LB Film of C18DAO on a Ge Prism. All ofthe spectra in this figure were measured after thefilms were kept in a Desiccator for 24 h.Reprinted from Langmuir, Vol. 15, 6890-6896, Copyright


Fig. 24 (a) An IR RA Spectrum of an Aged One-Layer LBFilm of 2C18DAC on a Gold-Evaporated GlassSlide. (b) An IR Transmission Spectrum of anAged One-Layer LB Film of 2C18DAC on a CaF2

Plate. (c) An IR/ATR Spectrum of an Aged One-Layer LB Film of 2C18DAC on a Ge prism. All ofthe spectra in this figure were measured after thefilms were kept in a desiccator for 24 h.Reprinted from Langmuir, Vol. 15, 6890-6896, Copyright



persed in surfactant solutions (see Figs. 27 & 28).Kakehashi et al. (37) examined the effects of the

hydrocarbon chain length, the bulkiness of the polarhead group, the added salt concentration, the surfactantconcentration, and temperature on the hydrogen iontitrations of amine oxides. The surfactants studied arealkyldimethyl amine oxides (CnDAO) with hydrocarbonChain lengths of 10-16, and N,N-bis(2-hydroxy ethyl)alkyl amine oxide (CnDHEAO) with hydrocarbon chainlengths of 10-14. From the results of hydrogen ion titra-

tion, the surface electric potentials were estimated.Kawasaki and Maeda (38) used Fourier-transform

infrared spectroscopy (FT-IR) coupled with attenuatedtotal reflection (ATR) to investigate the proposed H-bond between the head groups of C12 DAO (a = 0.5) inboth an aqueous medium and the solid state. To clarifythis hydrogen bond (H-bond), they focused on the OHband of the headgroup of C12 DAO (a = 0.5 and 1) inthis study (see Figs. 29 to 32).

Dielectric relaxation spectroscopy is a very powerfulmethod to investigate the motion of molecules possess-ing electric dipole moments. Itatani and Shikata (39)examined the dielectric relaxation behaviour of aque-ous dodecyldimethyl amine oxide (DDAO) solutions bychanging the concentrations of DDAO, NaBr and the

109J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 25 (a) An IR RA Spectrum of a One-Layer LB Filmof C18DAO on a Gold-Evaporated Glass SlidePrepared from the Aqueous Subphase at pH 3.0.(b) An IR Transmission Spectrum of a One-LayerLB Film of C18DAO on a CaF2 Plate Prepared fromthe Aqueous Subphase at pH 3.0.Reprinted from Langmuir, Vol. 15, 6890-6896, Copyright


Fig. 26 (a) An IR RA Spectrum of a One-Layer LB Filmof 2C18DAC on a Gold-Evaporated Glass SlidePrepared from the Aqueous Subphase at pH3.0. (b)An IR Transmission Spectrum of a One-Layer LBFilm of 2C18DAC on a CaF2 Plate Prepared fromthe Aqueous Subphase at pH 3.0.Reprinted from Langmuir, Vol. 15, 6890-6896, Copyright


Fig. 277Li Double-Quantum Filtered Spectra of Lithium-Exchanged Laponite Suspended in Water (ClayContent, 17.8 g/L; Li+ Concentration, 13.0 mM)(Top, q = 90°; Bottom, q = 54.7°).Reprinted from J. Colloid Interface Sci., Vol. 236, 290-294,


Fig. 287Li Double-Quantum Filtered Spectrum (q =54.7°) of Lithium-Exchanged Saponite (Charge0.35)(Clay Content, 40.0 g/L; Li+ Concentration,37.1 mM) Suspended in Surfactant Solution (0.1M).Reprinted from J. Colloid Interface Sci., Vol. 236, 290-294,



pH value to elucidate dynamic features in micelles ofDDAO in aqueous solutions.

Adsorption and self assembly are central characteris-tics features of surfactant molecules. The adsorption ofsurfactants from solutions onto solid surfaces has beeninvestigated over many years in relation to numerouspractical applications, as well as the scientific interest.Hideya Kawasaki et al. (40) investigated the effect ofprotonation on the aggregate structures of tetradecyl-adimethyl amine oxide (C14DAO) surfactants at mica-solution and graphite - solution interfaces by atomicforce microscopy (AFM). C14DAO solutions are mix-tures of the nonionic (C14H25(CH3)2N→ 0) and the ion-ized (protonated) cationic species (C14H25(CH3)2N-

110J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 29 (A) FT-IR Spectra of Solid C12DAO withDifferent Degrees of Protonation, a (a = 0, 0.5,and 1), at 25℃. (B) Comparison of the IR Spectraof C12DAOHCl with that of C12DAOHNO3.Reprinted from Langmuir, Vol. 17, 2278-2281, Copyright


Fig. 30 (A)FT-IR-ATR Spectra of C12DAO with DifferentDegrees of Protonation, a (a = 0, 0.5, and 1), inthe Aqueous Liquid Crystalline Phase (Hexagonal)at 25℃.The Weight Percent of the Surfactants is 55.(B)FT-IR-ATR Spectra of C1DAOHCl in AqueousSolutions of Various Concentrations at 25℃.Theweight percent of C1DAOHCl(from top to bottom)was 40, 30, 20, and 5. For comparison, the FT-IR-ATR spectrum of the C12DAOHCl (55 wt%) isalso shown (a). The spectral subtraction of waterfrom the IR spectra was performed on onlyC1DAOHCl spectra of 5 wt%.Reprinted from Langmuir, Vol. 17, 2278-2281, Copyright


Fig. 31 Dependence of a Continuous Absorption Band(1300-800cm-1) of the Solid C12DAO on theDegree of Ionization, a. The peak intensity IN isnormalized by that of the symmetric CH2

stretching band.Reprinted from Langmuir, Vol. 17, 2278-2281, Copyright


Fig. 32 FT-IR-ATR Spectra of C12DAO with DifferentDegrees of Protonation, a (a = 0, 0.5, and 1), inAqueous Solutions at 25℃. The weight percent ofthe surfactants is 55.Reprinted from Langmuir, Vol. 17, 2278-2281, Copyright



OH). The composition aM (the degree of ionization) inthe micelle is determined by pH under a given ionicstrength. The mixture of the protonated and unprotonat-ed species show an extreme synergism due to the shortrange attractive interaction between the headgroups.

Pettersson and Rosenholm (41) reported onmicrocalorimetric studies of the adsorption ofalkyldimethyl amine oxides (CnDAO with n = 8, 10 and12) on mesoporous and slightly negatively charged sili-ca gel from aqueous solutions at 298.15 K. Since thepH was natural, the study of CnDAO concerns adsorp-tion from mixed nonionic-cationic surfactant solutions.Due to increase in pH, the proportion of cationic surfac-tant decreases at increasing surfactant content. Theadsorption from dilute solution of all surfactants studiedwas exothermic and enthalpically driven due to forma-tion of H-bonding between nonionic headgroups andsurface silanol groups, and due to electrostatic interac-tions between ionic adsorbates and oppositely chargeddissociated surface silanol groups. Pettersson andRosenholm (42) also studied the x-potential of granularsilica gel interacting with aqueous solutions ofCnDAO(with n = 8, 10 and 12). The x-potential wasdetermined by measuring the streaming potential acrossthe capillary of the plug of sample.

Aqueous mixtures of alkyl amine oxides and dodecylsulfates draw much attention owing to their peculiarphysico-chemical behaviour and miscellaneous applica-tions. Smirnova et al. (43) examined that strong syner-gistic effects are responsible for the specific phasebehaviour of amine oxide-sodium (magnesium) dodecylsulfate micellar solutions. The dissolution temperatureand the CMC value are greatly dependent on relativesurfactant concentration and pH. The phase diagrams inthe two studied systems C12 AO- Me DS- H2O are quitesimilar at low pH and differ at the natural acidity. Atlow pH, the complex AOH+DS- is crystallized over awide range of surfactant based concentrations (see Figs.33 to 40).

Solid-solution phase behaviour of surfactant mix-tures is important both in theoretical and appliedaspects and has been studied extensively. The dissolu-tion temperature of binary mixed surfactants has beenreported to show a temperature maximum where thecomplex between the two components is formed.Kawasaki et al. (44) studied the effects of protonation(ionization) of alkyldimethyl amine oxides on the disso-lution temperature in aqueous media by differential

scanning calorimetry. Effects of alkyl chain-length onthe dissolution temperature for a homologous series ofoctadecyl-, hexadecyl-, and tetradecyldimethyl amineoxide were also examined. It was observed that thetransition temperature and associated thermodynamicquantities DH and DS increased systematically with thechain length.

6 Applications of Amine Oxides

The application of these compounds varies with thesize of the main alkyl chain and the substituents on thenitrogen atom of amine oxide. For example, the cocorange alkyldimethyl amine oxide serve as very effectivefoam boosters in light duty detergents and shampoos

111J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 33 Dependence of pH on x’HCl for C12AO-NaDS-HCl-H2O and C12AO-Mg(DS)2-HCl-H2O Solutions atxAO = xMeDS = 0.0005 and t = 50℃.Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright


Fig. 34 The Dissolution Temperature versus x’AO in theC12-AO-NaDS-HCl-H2O System at xtotal = 0.001.Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright



(45), while the higher stearyl amine oxides can be usedas hair conditioners (46). Tomah company of Milton,WI developed a series of amine oxide namely TomahAO-728 special, AO-14-2, AO-405 and AO-455 havingproperty of high foaming, moderate foaming , lowfoaming and extremely low foaming respectively, get-ting application in various types of cleaners. TomahAO-728 special is an economical replacement for lauryldimethyl amine oxide and many alkanolamides. TomahAO-14-2 is considered a more environmentally safealternative to solvent coating systems. In particular,AO-14-2 can replace the use of glycol ethers in clean-ing compounds. AO-405 and AO-455 are especially

112J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 35 The Dependence of the pH Value on x’AO in theC12-AO-NaDS-HCl-H2O Solutions at xtotal = 0.001.Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright


Fig. 36 The Dissolution Temperature as a Function of x’HCl

in the C12AO-NaDS-HCl-H2O System at xAO =xNaDS = 0.0005.Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright


Fig. 37 The Dissolution Temperatures as a Function ofx’NaOH in the C12AO-NaDS-NaOH-H2O System atx’AO = 0.8 and xtotal = 0.001; x’NaOH = xNaOH/(xAO +xNaOH).Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright


Fig. 38 The Dissolution Temperature versus x’AO in theC12-AO-Mg(DS)2-HCl-H2O System at VariouspHs; the Total Surfactant Content is 0.1 mol% (0.1mol%, 10 wt% at Natural pH).Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright


Fig. 39 The Dependence of the pH Value on x’AO in theC12-AO-Mg(DS)2-HCl-H2O Solutions of VariousAcidity, xtotal = 0.001.Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright



suited for hard surface applications where low or zerofoam generation is required.

Smith et al. (47) developed, high active alkyldimethylamine oxide powder permits the use of this valuablesurfactant in water sensitive formulations such as barsoaps. Study of the various amine oxide homologs inkey performance properties of soap bars showed themto be effective foam modifiers, plasticizers and syner-gistic lime soap dispersants. The solid amine oxideswere found to be a versatile additive which could readi-ly be formulated into a wide variety of personal carebars.

Crutcher et al. (48) studied the interaction of solidalkyldimethyl amine oxide (AX) and ditallowdimethylammonium chloride (DTMAC) and ditallowdimethylammonium sulfate (DTMAS) quats in representativetypes of fabric softener systems with particular focus onsynergistic behaviour. Softening, whiteness retention,wetting, static build up and detersiveness were evaluat-ed for laundry rinses, laundry detergents and dryersheets. In laundry rinses, blends of amine oxide andDTMAC proved to be synergistic for improving thewetting of cotton towels. Although no synergism wasobserved in laundry detergents, formulations containingamine oxide (AX) gave better detersiveness than sys-tems with DTMAC without the splotching associatedwith the quaternary salt. In dryer sheets, it was discov-ered that blends of amine oxide and DTMAS gave syn-ergistic softening of cotton towels and were unexpect-edly effective in preventing static charge build up onpolyester fabric (see Figs. 41 to 55).

Guest and guest-guest interactions. Recently photo-physical and photochemical properties of intercalationcompounds have attracted increasing interest. By use ofdodecyldimethyl amine N-oxide. Ogawa (49) preparedsmectite / dodecyldimethyl amine N-oxide intercalationcompounds a specific type of surfactant - modifiedclays. Intercalation compounds with two differentarrangement of the intercalated dodecyldimethyl amineN-oxide were obtained, depending on the adsorbedamounts.

Several instances of synergistic interaction have beenidentified between amine oxides and alcohol ethoxy-lates in various surfactant formulations. Miller et al.(50) examined whether these benefits could be observedwithin the framework of generic hard surface cleaningformulations. Comparative evaluations were also car-ried out to determine the performance characteristics oflow- and zero-phosphate systems in whichalkyldimethyl amine oxides and linear alcohol ethoxy-lates are used. Best cleaning was observed with 1:1mixtures of the subject surfactants, but substantialimprovements over alcohol ethoxylate alone also werenoted with formulations that contained lower ratios ofamine oxide. These system displayed good cleaningperformance when tested on vinyl floor tiles soiledwith an oily/ particulate soil.

Mel’nikova and Lindman (51) investigated pH con-trolled DNA condensation in the presence of dode-cyldimethyl amine oxide (DDAO). Interactions betweenDNA and amphiphilic systems have attracted muchattention from the pharmaceutical perspective: e.g,cationic lipid systems are found to be effective as anonviral vehicle for controlled gene transfer. In theinvestigation it was observed that positively chargedDDAO ions in vesicular form behave as a more effi-cient DNA-condensing agent than those in the micellarform.

Aqueous mixtures of the single - chain zwitterionicsurfactant alkyldimethyl amine oxide (C14DMAO) withother surfactants and cosurfactants are known to pro-duce a very rich phase behaviour with differentmicrostructures when the amphiphilic composition isvaried. From all the phases, the vesicle (La) phase is ofparticular interest and has attracted a large number ofinvestigations because of the potential for these equilib-rium aggregates to serve as good biological modelmembranes as containers for encapsulation and eventu-al release of drugs, flavors, and fragrances, and as

113J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 40 The Dissolution Temperature as a Function of x’HCl

in the C12AO-Mg(DS)2-HCl-H2O System at xAO =xMg1/2DS = 0.0005.Reprinted from Langmuir, Vol. 18, 3446-3453, Copyright



114J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 41 Laundry Rinse: Softness Rating. Variability = ±0.3 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,

Copyright with permission from Am. Oil Chem. Soc.

Fig. 42 Laundry Rinse: Whiteness Rating. Variability = ±0.5 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 43 Laundry Rinse: Wetting Rating after Four Cycles.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 44 Laundry Rinse Synergy: Softness Rating.Variability = ± 0.3 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 45 Laundry Rinse Synergy: Whiteness Rating.Variability = ± 0.5 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 46 Laundry Rinse Synergy: Wetting Rating after FourCycles.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,



115J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 47 Laundry Rinse Synergy: Antistatic Activity afterOne Cycle. Values for untreated fabrics are:polyester, 2.63 kV; cotton/polyester, 1.01 kV;cotton, 4.09 kV.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 48 Laundry Detergent: Softness Rating. Variability =± 0.3 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 49 Laundry Detergent: Whiteness Rating. Variability= ± 0.5 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 50 Laundry Detergent: Wetting Rating after FourCycles.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 51 Laundry Detergent: Detersiveness Rating fromTergotometer Evaluations of Dust-Sebum Cotton/Polyester Test Fabric.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 52 Dryer Sheet Synergy. Softness rating. Variability =± 0.3 for 95% confidence level. Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,



microreactors for the formation of a range of inorganicnanoparticles. Hao et al.(52) investigated a cationic /anionic surfactant system that consists of the zwitteri-onic alkyldimethyl amine oxide (C14 DMAO) and theanionic dihydro-perfluorooctanoic acid (C6F13CH2

COOH, DHPFOA, pKa = 3.35). In the investigated sys-tem, the cationic surfactant is produced by the protona-tion of the amine oxide by the perfluorooctanoic acid.As a result of this proton transfer reaction, the mixedsystem does not contain excess salt as do other studiedcationic / anionic surfactant systems. With increasingconcentrations of DHPFOA; L1-phase, a viscous L1-phase, a two phase L1/La-region, and slightly vis-coelastic La-phase were observed. The main purpose ofthis investigation was to demonstrate that in many casesvesicles in aqueous mixtures of cationic and anionicsurfactants do not form spontaneously but may be theresult of the shear forces that are due to the mixing ofthe components.

7 Anti-Microbial Activity of Amine Oxides

with Variation in Chain Length

Alkyldimethyl amine oxides has been shown to havepronounced anti-microbial activity when used individu-ally or in combination with alkyl betaines. Althoughseveral studies have been conducted with these com-pounds in combinations, only equimolar concentrationsof the C12/C12 and C16 /C14 chain lengths for the betaineand the amine oxide, respectively, have been investigat-ed.

Birnie et al. (53) investigated the anti-microbialactivity of a wide range of chain lengths (C8 to C18 ) forboth the amine oxide and betaine and also attempted tocorrelate their micelle - forming capabilities with theirbiological activity. Anti-microbial activity was found toincrease with increasing chain length for both homolo-gous series up to a point, exhibiting a cut off effect atchain lengths of approximately 14 for amine oxide and16 for betaine. Additionally, the C18 oleyl derviative ofboth compounds exhibited activity in the same range asthe peak alkyl compounds. Although each of thesecompounds have shown pronounced anti-microbialactivity alone against a variety of microorganisms, theyhave also been used in combination to exhibit a syner-gistic effect (54).

The variation in length of the long-hydrocarbon tailis thought to influence the extent of anti-microbial

116J. Oleo Sci., Vol. 55, No. 3, 99-119 (2006)

Fig. 53 Dryer Sheet Synergy: Whiteness Rating.Variability = ± 0.5 for 95% confidence level.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 54 Dryer Sheet Synergy: Wetting Rating after FourCycles.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,


Fig. 55 Dryer Sheet Synergy: Antistatic Activity after OneCycle. Values for untreated fabrics are: polyester,10.9 kV; cotton/ polyester 2.2 kV; cotton, 2.9kV.Reprinted from J. Am. Oil Chem. Soc., Vol. 69, 682-689,



activity. Like most other surfactants, they are believedto be membrane perturbants, disrupting the cell mem-brane of the microorganism. It is believed that interac-tion with the surface of the microorganism is a functionof the polar head groups of the amine oxide, betaine ormixture of these molecules and that the hydrocarbontail subsequently becomes integrated with the lipidbilayer of the cell membrane. This integration causes adisruption in the membrane and inevitably causes leak-age of the cell contents. The length of the alkyl chain ofthe surfactants is thought to contribute to the extent ofthis membrane disruption, because the higher chainlengths may be incorporated into the lipid bilayers ofthe plasma membrane. The increased hydrophobiceffect of these longer chain tails may aid in this disrup-tion.

8 Safety of Amine Oxides

Amine oxides have low potential for bioaccumula-tion in aquatic tissues, indicating low potential for bioconcentration in terrestrial organisms, also this is highlyremoved by conventional sewage treatment. Sansoni(55) demonstrated that amine oxides surfactants arenonvolatile and readily biodegradable under aerobic andanaerobic conditions, according to SDA research.

All available information on amine oxides demon-strates it has low-to-moderate level of toxicity.

Acknowledgment

The authors are grateful to late Prof. R.K. Khanna,Department of Oil and Paint Technology, H.B. Techno-logical Institute Kanpur, for his valuable guidance andmotivation.

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Amine Oxides: A Review - J-Stage

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