Barbiturate Derivatives for Stable Aqueous Nanoscale Pigment Yellow 150 Dispersions

Three structurally related barbiturate-derived dispersants were synthesized and evaluated to investigate how molecular architecture relates to the aqueous dispersion behavior of Pigment Yellow 150. BA-A and BA-B contain arylazo/hydrazone-type frameworks bearing nominal sulfonate and carboxylate termini, respectively, whereas BA-C contains an arylidene framework bearing a nominal carboxylate terminus. Their acid-form precursors were characterized by proton nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and ultra-performance liquid chromatography-mass spectrometry. BA-A and BA-B produced Pigment Yellow 150 dispersions with z-average hydrodynamic diameters of 67.04 and 69.30 nm, polydispersity indices of 0.12 and 0.15, zeta potentials near -40 mV, and low apparent viscosities. In contrast, BA-C produced a coarse dispersion with a z-average hydrodynamic diameter of 1858 nm, while BYK-190 gave 124.70 nm at the tested nominal dosage. The BA-A and BA-B solutions exhibited calculated Washburn penetrativities approximately 2.5 times that of water, and their pigment dispersions showed dominant proton transverse-relaxation peaks at shorter times than the BA-C dispersion. Overall, BA-A and BA-B exhibited more favorable powder wetting and colloidal stabilization than BA-C, supporting a formulation-specific relationship between molecular architecture and dispersion performance within the investigated series.