Relationship between structure and solubilization properties of some bisquaternary ammonium amphiphiles

Urea-based gemini surfactants: Synthesis, aggregation behaviour and biological activity

“…A similar difference in the slopes of concentration dependences of micelle aggregation number was observed for the gemini surfactant with the short methylene spacer 12-3-12 on the one hand and for micelles composed of gemini molecules with longer spacer values s > 4 on the other [28]. The corresponding single chain quaternary ammonium surfactant DTAB shows only a very small increase in N [38] with the increasing concentration. Therefore, the tendency to micellar growth is primarily determined by the structural arrangement of gemini molecules with the short spacer (s= 2, (Fig.…”

“…Their physical and aggregation characteristics such as critical micelle concentration and surface properties [36][37][38][39][40][41], micelle aggregation number and size [42][43][44], antimicrobial activity [45], aggregate structure variability in aqueous solutions as a function of the spacer length [46], indicate unique properties and aggregation behaviour of this class of surfactants which predetermines them to be used in a broad range of applications.…”

Molecular concepts, self-organisation and properties of polysoaps

“…The values of CMCs determined by different methods agree well, and the counter-ion effects are the usual ones [426,427]. But, strikingly, CMC values of both bola-surfactants and of gemini-surfactants are lowered by one order of magnitude or more in Examples of "oligomeric" surfactants: a "bola" dimer [426][427][428]; b "gemini" dimer [435,445,448]; c cyclic hexamer of "tail end" type [419]; d star-shaped trimer of "tail end" type [420] comparison to the corresponding "monomers" [239, 424,[428][429][430][431][432][433][434]. The reduction of the surface tension appears slightly lower than for the monomers, but the surface activities are still substantial [330,405,413,424,427,[429][430][431][432][433][434][435].…”

“…The properties of gemini-surfactants are markedly influenced by the length of the linking unit, which represents the equivalent to the main chain spacer unit in "head type" polysoaps: the CMC does not decrease monotonously with increasing spacer length, as would be expected from the decreasing HLB, but shows a maximum value at intermediate spacer length (C 6 -C 8 ) [433, 435,445,447,448]. The surface tensions obtained at the CMC show a minimum in the same range of spacer length [435], and the solubilization capacity a maximum [448].…”

Association behaviour of glucitol amine gemini surfactants

“…Below this value the spacer becomes more or less rigid and is forced to be on the outside of the associate. If the glucitol groups had not been present, this might have even led to a maximum in φ 0 as is, e.g., observed for gemini surfactants of type ( [28,4]. Due to the very low critical association concentration of the glucitol amine surfactant, also reflected in the formation of vesicles [9], no experimental cmc data is available for the present system.…”