Non-ionic Systems

Although cholesterol is essentially insoluble in water, a soluble cholesterol derivative can be formed by reacting it with high levels of ethylene oxide.66,67 This ethoxylated product has balanced hydrophobic and hydrophilic properties. The increased hydrophilicity makes it useful as an oil-inwater emulsifier or as a stabilizer. Ethoxylated lanolin is used for viscosity regulation, pigment dispersion, and as a solubilizer. Less than 1% ethoxylated cholesterol is effective at reducing the viscosity of anionic lotions to make them easier to pour. Non-ionic systems require more ethoxylated cholesterol for this purpose 68... 

Finally, as Ahrland, Chatt and Davies (4) extended their observations to non-ionic systems, we must also look at such equilibria as MRn -f- DRn 5s - MRn... 

Three modes of bond breaking may be distinguished in homogeneous, non-ionic systems, namely bond homolysis,... 

Fundamental aspects of coacervation have been thoroughly covered for some time through the classical studies of Bungenberg de Jong and Kruyt for ionic systems, and by Dobry and Boyer-Kawenoki for non-ionic systems. The basic thermodynamic conditions for polymer-solvent interactions and polymer phase separation have been nicely described by Flory. In the following, polymer phase separation processes will be briefly considered from mechanistic and thermodynamic points of view. 

If the phase under consideration is neutral then of course is the same as jP. In this chapter we shall study only electroneutral systems, which remain electroneutral during the course of any transformations considered, and which do not exchange electrical energy with their surroundings. The function F will then possess all the properties which we have established for the case of non-ionic systems. 

Examination of ternary systems (containing the emusifying wax and water but no oil phase) by X-ray diffraction indicates that, for all emulsifying systems, addition of water causes swelling of the interlamellar spaces. Ionic emulsifying systems possess a greater capacity to swell than non-ionic systems. Swelling in ionic systems is an electrostatic phenomenon, whereas that... 

The water to surfactant molar ratio was the main variable studied for the anionic system. The water molecules were found to bind strongly to the surfactant polar groups and the sodium counter ions at to values below 4. This behaviour resulted in an inhibition of TEOS hydrolysis. As to was increased from 5 to 9.5, the particle size increased and the size distribution decreased. Furthermore, the size distribution of the particles prepared by the anionic system was broader than for the non-ionic system. 

K is (. 16 for alkyiben .enesulfonates, about 0.10 for alkyl sulfate and fatty acid strdium soaps, 0,17 for i-alky ammonium salts at low pH, and 0.19 for quaternary H-atky I tri methyl ammonium salts, while k is found to be 0.16 for non ionic. systems. The coetfieicnl of the salinity effect for non ionic surfuciants is small, i.e.. O.l.l and 0.10 (in EON unit per wt9f salt in aqueous phase) respectively for sodium and calcium chloride. 

The difficulties of constructing phase diagrams for the non-ionic systems that are used in emulsion coxinting have been described (Prince, 1977). This author recommended that the samples used should be stored for at least three months due to the long period of time required to attain true equilibrixm. 

The dynamic test data in the kHz region of ionic emulsions could be described using either model. The emulsion elasticity originates in the interphase deformation. For non-ionic emulsions, only one relaxation time was observed. The data were interpreted in terms of the second Oldroyd model in which the interfacial tension is more important than the viscoelasticity of the interphase. The steady state viscosities of both ionic and non-ionic systems at the volume fraction < 0.2 were found to follow Simha s equation (Eq. (2.8)). 

It can be noticed that the majority of copolymers in this category contain a PEO or a PVME sequence and that for completely non-ionic systems micellization is mainly induced by a temperature change. For those copolymers with an ionic and a non-ionic sequence micellization becomes also possible by pH changes or by addition of electrolytes. 

A viscous isotropic region has been detected at concentration regions in between the middle and neat phases in some non-ionic systems [7-9]. Fig. 2.3 shows the occurrence of this phase in the N,N,N-trimethylaminododecano-imide-water system which was extensively studied by Clunie et al. [9]. 

The influence of the hydrophile-lipophile balance (HLB) of the non-ionic surfactant on the phase behaviour has recently been studied [34-37] with the aim of better understanding the mechanisms of emulsion and suspension stabilization. Ternary phase diagrams for dodecane, water and mixtures of Brij 92, and Brij 96 (polyoxyethylated oleyl alcohol derivatives with oxyethylene chain lengths of 2 and 10, respectively), with a range of HLB values, are shown in Fig. 2.19. The areas of the L2 and the inverse middle phase M2 (an interesting feature of these systems not usually observed in polyoxyethylene non-ionic systems) increase as the HLB increases, reaching a maximum at HLB 8. Maximum water uptake in the L2 phase in 25 %, 40 % and 50 % surfactant solutions in oil as a function of HLB is... 

The results of Matsumoto and Aoki [204] have been recalculated in terms of solubilities in 0.01 m solutions. This presents a picture exactly opposite to the one obtained on a percentage basis (see Fig. 7.44). This evidence should make the selection of a preservative for use in non-ionic systems less empirical. It is suggested that where no information is available for the interaction of the preservative with the detergent the least hydrophobic compound is used to minimize solubilization, or where a compound such as the butyl paraben must be employed a surfactant with a long hydrophilic group is chosen. Often a balance between the two will have to be made. 

Chlorobutanol, benzyl alcohol, and phenylethyl alcohol-non-ionic systems have been studied at two temperatures [205], as was the binding of benzoic acid by polyoxyethylene stearates [206]. The latter confirmed that solubilization was greatest in the least hydrophilic surfactant (on percentage basis) and there was no evidence of interaction below the CMC. 

The apparent pXa of dyes such as Malachite Green increases with increase in the surfactant-water ratio in Igepal CO-530 inverse micelles in benzene [128]. If the water is largely bound to the PEG chains in the micellar interior it is likely that the effective dielectric constant will be quite different from that of bulk water and thus the apparent simplicity of the non-ionic system over an ionic reversed system is disproved. Non-ionic surfactants have also been found to increase the rate of the... 

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