Abstract:

The five-component system is quite unique since it allows formation of reverse micelles with hydrophilic ethoxylated alc. in the presence of ethanol and it facilitates diln. by water/propylene glycol (1,2-propanediol, PG) aq. phase, all the way from a water-in-oil (W/O) microemulsion via a bicontinuous phase to an oil-in-water (O/W) microemulsion. The surfactant/alc./PG can strongly bound water in the inner phase so that it freezes below -10°C and acts in part as bound water and in part as non-freezable water. Upon diln. to \textgreater30 mass% aq. phase (water/PG at const. mass ratio of 1/1) the system becomes bicontinuous and the aq. layers are composed again from bound water. Even after complete inversion to O/W microemulsions the water in the continuous phase is strongly interacting with the PG/surfactant and remains bound or non-freezable. Water/PG/ethanol have a strong effect on the head groups (freezing below -10°C) and also on the hydrophobic tails (recrystg. and melting) at lower temp. when diln. exceeds 45 mass% water/PG (1/1). No free water was detected neither in the W/O microemulsion s inner droplet domains nor when the microemulsion was either bicontinuous or when it was inversed to O/W. Continuous phase of resulting O/W microemulsion apparently is based on water/PG at a mass ratio of 1/1. [on SciFinder(R)]