Preparation of nylon 6 nanoparticles and nanocapsules by two novel miniemulsion/solvent displacement hybrid techniques

Nylon 6 (polyamide 6) nanoparticles dispersed in an aqueous phase and nylon 6 nanocapsules dispersed in cyclohexane were successfully prepared via two rapid and facile techniques. These techniques combine some characteristics of the miniemulsion and the solvent displacement techniques. The principle of the first technique consists of adding nylon 6 dissolved in formic acid to an aqueous phase containing poly(vinyl alcohol) as stabilizer, while ultra-sonicating the aqueous phase in order to obtain stable nanoparticles. The stability of these particles was studied over a wide range of reaction parameters, such as the temperature, the nature and concentration of the chemicals, the time and amplitude of ultrasonication. TEM micrographs of the unmodified particles revealed a morphology where the nylon 6 particles are completely wrapped by the poly(vinyl alcohol). After removal of the poly(vinyl alcohol), the nylon 6 particles were found to have a bumpy or rough morphology. The second technique allows the preparation of particles by miniemulsifying the disperse phase, a solution of nylon 6 in formic acid, in cyclohexane. Then methanol is added to the miniemulsion which immediately reacts with the formic acid. The product of the reaction, methyl formate, is evaporated and the water replaces the formic acid in the droplets, thus allowing the precipitation of the nylon 6 at the interface of the droplets resulting in the formation of nanocapsules.