A new oil-associative polymer for stabilizing inverse emulsions:: Strategy, synthesis, and physicochemical properties

A long flexible poly(dimethylsiloxane) (PDMS) backbone has been grafted with poly(ethylene oxide) (PEO) chains to obtain an amphiphilic oil-associative copolymer (PDMS-g-PEO). The copolymer exhibits interesting bulk-thickening properties in apolar organic oils (n-dodecane) thanks to the intermolecular association of PEO chains. We show that the hydrophilic association is considerably strengthened by the addition of small amounts of water, with the consequence that PDMS-g-PEO dodecane solutions exhibit solidlike behavior. The PDMS-g-PEO chains adsorb at the water-dodecane interface as shown by tensiometry. Moreover, we show that the copolymer provides good stability to both concentrated and nonconcentrated inverse emulsions. This is due to the design, the choice of the anchor and stabilizing moieties, and the balance of the hydrophilic-lipophilic properties of the polymeric surfactant, which allows not only the steric protection of the water droplets but also their trapping into a viscoelastic external phase.