Synthesis and aggregation properties of dialkyl polyoxyethylene glycerol ethers

Two series of symmetric 1,2-dialkyl-rac-glycerol ether surfactants containing a polydisperse non-ionic monomethyl polyoxyethylene glycol (MPEG) head group have been prepared using one of two similar four stage reaction pathways. Both schemes start with isopropylidene-rac-glycerol. In the first scheme the unifunctional MPEG was brominated and added to isopropylidene-rac-glycerol directly. In the second pathway the underivatized MPEG was attached to isopropylidene-lac-glycerol via a tosyl glycerol derivative. In both reaction schemes the alkyl chains were introduced onto the monomethyl polyoxyethylene glycerol using a Williamson ether type reaction. A third, six stage, synthetic route allowed the production of asymmetric 1,2-dialkyl-rac-glycerol ether surfactants. In this scheme the first alkyl chain was added to isopropylidene-rac-glycerol directly; while the second chain was added after selective (trityl group) protection of the primary hydroxyl of the monoalkyl glycerol ether. In this route the polyoxyethylene glycol (PEG) chain was added terminally. In all schemes the crude surfactants were purified either by column chromotography or by a simple but effective washing and molecular distillation procedure. The aggregation behaviour of the novel surfactants in aqueous solution is reported, and general trends noted as to the influences of the hydrophobe and head group lengths on the nature of the aggregates formed.