Synthesis of Water-Soluble Polymeric Surfactants Bearing Sulfonic Acid Groups and the Effects of Hydrophilic Components on the Rheology and Dispersive Properties of Dye Dispersions

Water-soluble amphiphilic polymers containing styrene (St), acrylic acid (AA), or sulfonic acid moieties were synthesized and evaluated as polymeric surfactants for dye dispersions. 2-Acrylamide-2-methylpropanesulfonic acid (AMPS) was employed as a hydrophilic monomer containing a sulfonic acid moiety. The sulfonic acid moieties are effective hydrophilic molecular components adding moderate redispersion properties. Rheology, particle size distribution, surface tension, surface excess (Gamma max), minimum area per molecule (Amin), and redispersion properties were examined. This is because these factors are important in controlling the physical properties of an ink solution and the quality of printed materials. After the examination of surface parameters, the copolymer using St, AA, and AMPS shows the highest Gamma max, indicating that it is most densely packed at the water/air interface. Aqueous solutions of polymers containing an AA moiety exhibit pseudoplastic properties, whereas those containing only a sulfonic acid moiety show a clear Newtonian fluid property. All color dispersions show unimodal particle size distribution and stable dispersion after thermal aging. However, sedimentation of dye particles was observed for polymers containing AMPS. Incorporation of AA and AMPS moieties in the amphiphilic polymer structure is proven to be suitable for the redispersion of dried or solidified ink into aqueous media. Regarding the rheology and the surface parameters, this study has shown that water-soluble polymers with sulfonic acid groups exhibit different properties from those containing acrylic acid. The introduction of sulfonic acid groups into conventional amphiphilic polymers consisting solely of styrene and acrylic acid was found to improve the redispersion properties of the ink. In this study, we demonstrate the potential of water-soluble amphiphilic polymers containing sulfonic acid groups as dispersants for inkjet inks.