Water-soluble nanoparticles from poly(ethylene glycol)-based cationic random copolymers and double-tail surfactant

Water-soluble polymer–surfactant nanoparticle complexes were prepared using double-chain anionic surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and random copolymers (RCPs) synthesized from methoxy poly(ethylene glycol) monomethacrylate (MePEGMA) and (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTAC). Polymer–surfactant interaction between the positively charged polymers and oppositely charged surfactant resulted in formation of the nanoparticle complexes that were studied using turbidimetric titration, steady-state fluorescence, dynamic light scattering, zeta potential, and electron microscopy. The RCPs containing 88 mol% and 94 mol% of PEG formed stable nanoparticle complexes in the entire range of composition of the polymer–surfactant mixture, including stoichiometric compositions where the electroneutral complexes were formed. However, the complexes formed by copolymers with 66 mol% of PEG precipitated in water. Spherical nature of the nanoparticles was revealed by the transmission electron microscopic (TEM) analysis. Dynamic light scattering (DLS) showed that average diameters of nanoparticles were in the range of 50 nm and this was supported by the TEM analysis. Pyrene fluorescence experiments confirmed more hydrophobic cores for these water-soluble nanoparticles compared to those made from similar RCPs and single-tail anionic surfactants. Hence these nanoparticles made using double-chain surfactants can be potentially used to solubilize hydrophobic drug molecules more effectively.