SANS studies of polymerized nano-particles using nonionic/cationic surfactant mixture

Mixtures of polymerizable cationic surfactant, cetyltrimethylammonium 4-vinylbenzoate (CTVB), nonionic surfactant, Triton X-100 (TX-100), and polymerizable hydrotropic salt, sodium 4-styrenesulfonate (NaSS) in aqueous solution were free radically polymerized to produce stable rod-like nano-particles with varying aspect ratio. A series of 1 wt% of the mixed surfactant (CTVB+TX-100) solutions were prepared with varying surfactant molar mixing ratio α (=TX-100/(TX-100+CTVB)) from 0.07 to 0.41. In all the samples, an appropriate amount of NaSS was added to keep the molar amount of CTVB plus NaSS constant at 0.0257 M; this maintained the amount of polymerizable counterions constant in all the samples. SANS measurements showed that the polymerized aggregates were cylindrical nano-particles which were stable against temperature variation between 30 and 60 °C. While the radius of the particles was constant at 2 nm, the aspect ratio was decreased from 27.5 to 2.7 as the mixing ratio α was increased from 0.07 to 0.23.