Synthesis and characterization of branched polyglycerol surfactants

Abstract

Polyglycerol surfactants have emerged as a promising renewable alternative to fossil based polyethylene glycol surfactants. The polyglycerol head group offers greater structural variability and possibility for functionalization. In order to facilitate the transition to renewable nonionic surfactants, a deeper understanding of the structure-property relationship, particularly regarding branching, is essential. To this end, two polyglycerol structures with different degrees of branching were synthesised through a series of chemical reactions. These structures were then esterified with carboxylate tails of varying lengths and analyzed by tensiometry, interfacial rheology and quartz crystal microbalance with dissipation monitoring. The results indicated that enlargement of the branched head group significantly influences the surfactants self-assembly and the air-water interfacial rheology. QCM-D analysis showed that the branched head group binds very strongly to hydrophilic surfaces, likely due to its hydroxylated nature.