Investigation and Application of Nanoparticle Dispersions of Pigment Yellow 185 using Organic Solvents

Self-aggregation of organic pigment nanoparticles in organic solvent produces poor quality thin-film coatings. The nonuniformity of surface layers produced by dense aggregates within films of nanopigments can be detrimental for light transmission. Formulating dispersions composed of an organic pigment and an organic solvent with minimized aggregation must be achieved for use as precursors for high-performance optical thin-Films. The goal of our investigation was to determine the influence of deaggregating dispersants with and without a surface-modifying synergist, as well as the influence of solvent polarity on the dispersion properties, The work was focused on establishing nanoparticles smaller than 50 nm in size, which is an area not broadly published for solvent-based systems. A working hypothesis of using an acid-functionalized synergist capable of establishing stable acid/base ionic-pair interactions was investigated. Our work demonstrated that a synergist that incorporates acid functional groups can be combined with an amine-functionalized polymeric dispersant to form a stable organic solvent-based dispersion composed of dispersed pigment nanoparticles that also incorporate amine functional groups. Stabilizing ionic-pair interactions are proposed. The dispersion and coatings of the dispersion were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Optical properties of thin-films were evaluated from transmission spectroscopy measurements. Within this study, a correlation was established between spectral properties of coated dispersions and detected nanoparticle aggregation.