Surface charge variation of nano particles with high aspect ratio: a SANS study

Rod-like nano-particles with controlled surface charge density have been developed by the free radical polymerization of cationic surfactants with polymerizable counterions, cetyltrimethylammonium 4-vinylbenzoate (CTVB), with varying concentration of sodium vinyltosylate (NaVT). The polymerization of the counterions of CTVB which forms worm-like micelle in aqueous solution induces stable rigid rod-like nano-particles. The surface charge density of the rod-like particles was controlled by adding the various amount of NaVT during the polymerization process. SANS measurements show that the diameter and length of the nano-particles are 4nm and 20nm∼ 80nm, respectively, depending on the concentration of NaVT. The zeta potential measurements showed that the zeta potential of the nano-particles is changed from positive to negative (11 mV ∼ -44 mV) as the concentration of NaVT is increased from 0 mol % to 40 mol %