DYNAMIC SURFACE TENSIONS, FOAM AND THE TRANSITION FROM MICELLAR SOLUTION TO LAMELLAR PHASE DISPERSION

If the packing behaviour of surfactants in close-packed layers is suff iciently modified then micelles are not formed. Solutions can become t urbid at a critical aggregation concentration where a dispersion of li quid crystalline particles is found. Examples of this type of behaviou r considered here include dodecyl polyethyleneglycol ethers with low d egrees of ethoxylation. The precipitation of liquid crystalline partic les either from mixtures of such compounds with micelle forming anioni c surfactants or from mixtures of micelle forming zwitterionics with c ertain micelle forming anionics are also included. Rates of transport of surfactant to air-water surfaces may be monitored by measuring dyna mic surface tensions. Solutions containing dispersed liquid crystallin e phase, rather than micelles, exhibit diminished rates of transport t o air-water surfaces which implies relatively low levels of dynamic ad sorption at these surfaces. This leads to diminished foamabilities. Ho wever the stability of the resulting foam may be enhanced. This may be caused by diminished bulk foam drainage rates due to accumulation of liquid crystalline material in Plateau borders. It may also derive fro m diminished foam film drainage rates caused by suppression of margina l regeneration.