Abstract:

Microemulsions contg. octanol, decanol, or dodecanol as the oil phase and oligomeric, grafted nonionic amphiphiles based on ethoxylated polymethylsiloxanes (Silwets) have been studied. It was demonstrated that significant amts. of water can be solubilized only when the hydrophobic siliconic backbone is very short (trimers). The water solubilization was evaluated using SAXS, DSC, and cond. measurements. It was found that up to 40 wt% of water can be solubilized in dodecanol and Silwet L-7607 (MW 1000 and 75 wt% ethylene oxide (EO)). Surprisingly, no free water was detected in the aggregate core. All the solubilized water was confined in the vicinity of the interphasal region and froze at -10°C and below. Up to three mols. of water can be assocd. with each EO headgroup. Based on SAXS measurements, the structural units of the microemulsions were interpreted to be lamellar-like, a form previously found for the related monomeric microemulsions. (c) 2001 Academic Press. [on SciFinder(R)]