Solubilisation of oils in aqueous solutions of a random cationic copolymer

Reports of random copolymers capable of solubilising hydrophobic oils are rare. This is primarily because random copolymers are unlikely to self-assemble into suitable aggregates (or micelles) in water. A random copolymer with a "blocky" (or lumpy) microstructure may have potential to solubilise hydrophobic oils in water. This type of polymer would have advantages over block copolymers which are more laborious and costly to synthesise.

The solubilising capacity of a blocky random copolymer, namely poly(methyl methacrylate-co-2-dimethylaminoethyl methacrylate) (PMMA-co-PDMAEMA) is assessed by UV-visible spectroscopy and compared with common reference surfactants. The relative solubilising performance of random copolymers (across a narrow range of DMAEMA mol % fraction) for aromatic and aliphatic oils was also studied. The morphology of the aggregates was monitored as a function of the solubilisation capacity by small-angle neutron scattering (SANS) and dynamic-light scattering (DLS).

Similarly to well-defined block copolymers, these random copolymers have a specific preference for solubilising aromatic over aliphatic oils. Increasing hydrophobicity of the copolymer enhances the solubilisation capacity. SANS has highlighted that aggregates become swollen and more uniform/spherical with increasing concentration of aromatic solubilisate, and that the aromatic solubilisate partitions throughout the random copolymer aggregates.