Narrowly Size Distributed Zinc-Containing Poly(acrylamide) Latexes via inverse Miniemulsion Polymerization

Polyacrylamide nanoparticles containing zinc nitrate were prepared via inverse miniemulsion polymerization using ultrasound emulsification. The effects of sonication time, mode of sonication, nature and type of emulsifier, amount of zinc salt, solvent in the dispersed phase, nature of dispersed and continuous phases, and type of initiator on the nucleation mechanism, conversion, molecular mass of polymer, and size distribution of the latex particles were investigated. The results showed that an increase in sonication time up to 4 min and using an amphiphilic polymeric surfactant with a relatively short hydrophilic part improved both the monodispersity and the stability of the zinc-containing latexes. An increase in viscosity of the continuous phase (changed by means of different nonpolar solvents) and decrease in viscosity of the dispersed phase (varied by the amount of water) had also a positive effect on the monodispersity. At the same time, the average diameter of the particles in the range of 225 nm changed only marginally. The use of either highly hydrophilic (ammonium persulfate) or highly hydrophobic (2,2'-azobis(2-methylbutyronitrile)) initiators, and the transfer from miniemulsion polymerization to dispersion, precipitation, or a combination of several polymerization types by the modification of the dispersed and continuous medium spread the polydispersity of the latex particles and impaired the stability. Samples with small content of salt were used for unconventional nanolithography by subjecting a highly ordered layer of the nanoparticles to a plasma etching process. Highly ordered arrays of particles containing ZnO nanocrystals were observed.