From a thorough study of many systems incorporating water, the ionic surfactant sodium dodecylsulfate, straighter or branched alkanols and aliphatic or aromatic hydrocarbons, it clearly appears that the molecular structure of the alkanol used as the cosurfactant is the composition factor that primarily determines the configuration of the microemulsion domain and, correlatively, the type of the microemulsion electroconductive and viscous behavior.Key words: Microemulsion(s), phase diagram(s), viscosity, electrical conductivity, water, sodium dodecylsulfate, straight alkanol(s), branched alkanol(s), aliphatic hydrocarbon(s), aromatic hydrocarbon(s).The realms-of-existence of monophasic, stable, fluid, transparent and isotropic media, (so-called "microemulsions" [1]), were delineated, at T = 25 ~ for a great number of systems incorporating water, sodium dodecylsulfate, straight or branched alkanols with number of carbons ranging from 2 to 10, and aliphatic, (n-octane, n-dodecane, n-hexadecane), or aromatic, (benzene, toluene), hydrocarbons. It has thus been possible to evidence the influence of different composition factors upon the general configuration of the microemulsion domain, e. g. straight alkanol number of carbons, alkanol isomery, aliphatic hydrocarbon chain-length, and aliphatic hydrocarbon-aromatic hydrocarbon substitution [2][3].It clearly appears from this study that, in any case, the three-dimensional microemulsion domain is the volumic extension of the realm-of-existence of the water/surfactant/alkanol micellar solutions. The micro-1) Present addresses: A. Zradba, Ecole Normale Sup~rieure de Casablanca, Avenue Victor Hugo, Casablanca, Maroc (Morocco).L. Nicolas-Morgantini, L'Or~al, 1, Avenue Saint Germain, 93600 Aulnay-sous-Bois (France). W950emulsion domain configuration is influenced, primarily, by the alkanol molecular structure, and, to a lesser degree, by that of the hydrocarbon. As a general rule, the microemulsion domain existing in the phase tetrahedron of systems incorporating long straight alkanols, (number of carbons no1 > 6), appears to consist of two disjoined volumes, V1 and V2, respectively built on the regions L1 and L2 corresponding, in the water/ surfactant/alkanol phase diagram, to direct and inverse ternary micellar solutions. Per contra, the microemulsion domain of systems incorporating short straight alkanols, (nc~ < 3), forms in the phase tetrahedron an all-in-one-block volume built on the "monophasic" area that exists in the water/surfactant/alkanol phase diagram, as the result of the merging of the L1 and L2 regions. In the case of medium straight alkanols, (3 < nca < 6), the microemulsion domain also forms an allin-one-block volume but exhibits configuration irregularities that reflect peculiarites of the water/surfactant/alkanol "monophasic" area.For the four systems water/sodium dodecylsulfate/ C4 to C7 straight alkanols/n-dodecane, details of the microemulsion domain configuration were obtained from systematic determinations of the microemulsion

Macroscopically homogeneous, stable, fluid, generally optically transparent and isotropic media (currently called "microemulsions") may be formed by adequately mixing together water, a hydrophobic hydrocarbon, ("oil"), and suitable amphiphilic substances. The microemulsion domains of numerous systems incorporating water, sodium dodecylsulfate, various straight or branched alkanols and various aliphatic or aromatic hydrocarbons were delineated at T = 25 ~ It has thus been possible to bring out the influence of several composition factors upon microemulsion domain configuration, i. e. straight alkanol number of carbon atoms, alkanol isomery, normal aliphatic hydrocarbon number of carbon atoms, aliphatic hydrocarbon-aromatic hydrocarbon substitution. The existence of two main kinds of water/ionic surfactant/alkanol/hydrocarbon systems, according as the microemulsion realm-of-existence in the phase tetrahedron consists of two disjoined volumes, ("long" alkanols), or forms an all-in-one block volume, ("short" alkanols), can well be correlated with the existence of striking dissimilarifles in certain transport properties of microemulsions, such as electrical conductivity or viscosity. For some "short" alkanols, (e. g. 1-pentanol or 2-pentanol), the microemulsion domains exhibits strange configuration irregularities. Results gained from studies of microemulsion electroconductive and viscous behavior and of cyclohexene-2-one-lphotodimerization in microemulsions tend to indicate that these configuration irregularities define certain ranges of system composition that correspond to microemulsions possessing an exotic structure.Key words: Water, sodium dodecylsulfate, straight and branched alkanols, afiphatic and aromatic hydrocarbons, cyclohexene-2-one-1, microemulsion(s).Des milieux tr~s divers par le nombre et la nature des phases qui les composent, lorsque l'~quilibre thermodynamique est atteint, peuvent ~tre form,s en m~langeant de l'eau, (ou une solution saline aqueuse), un liquide hydrophobe tel qu'un hydrocarbure aliphatique ou aromatique et une (ou plusieurs) substance