Nonionic Surfactant Properties of Amphiphilic Hyperbranched Polyglycerols

The surfactant properties of amphiphilic hyperbranched polyglycerols (HPGs) were investigated. The HPGs were prepared by ring-opening multibranching polymerization of glycidol using hydrophobic initiators of varying size and structure. The cloud points for all HPG surfactants were found to be >80 °C in deionized water with >1 wt % NaCl. The HPG surfactants with hydrophilic-lipophilic balance values between 16 and 18 were found to form stable octanol/water (o/w) emulsions within a 24 h period. Several surface properties, including critical micelle concentration (CMC), efficiency of surface tension reduction (pC₂₀), effectiveness of surface tension reduction (γ_CMC), surface excess concentration at the CMC (Γ_max), minimum area/molecule at the interface (A_min), and the CMC/C₂₀ ratio of the HPG surfactants were measured in deionized water at 22.6 °C. In general, increasing HPG size was marked by an increase in minimum surface area per molecule (A_min) at the aqueous liquid/air interface. This increase in size also led to lower CMC and greater pC₂₀ values of HPG surfactants prepared with Tergitol 15-S-7 initiator (HPG 5a-5d), a commercially available ethylene glycol oligomer with a branched hydrophobic tail.