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

Abstract

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 (Γmax), minimum area per molecule (A min), 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 Γmax, 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.

Polymeric Surfactants Bearing Divalent Carboxy Pendants for Stable Color Dispersions with High Redispersibility

“…Compared with St-AA , the rheological properties of amphiphilic polymers in this study, which contain the sulfonic acid group, are less Newtonian. The decrease in Newtonian properties due to the introduction of sulfonic acid was also observed in the previous work . However, lower viscosities than that of St-AA (10 mPa·s) in high shear rate regions were observed for all polymers confirming the applicability for inkjet inks.…”

“…In contrast with the polymer aqueous solutions, all dispersions showed positive yield values, with yield values ranging from 0.57 to 1.04 Pa and a shear-thinning effect. This behavior was observed in our previous work for St-AA-AMPS . According to a previous work, the yield values suggest that the color dispersion becomes structured upon addition of dye particles; hence, an initial critical stress should be applied to break down the structure.…”

“…The yellow dye caused sedimentation for all dispersions (red arrow) after thermal treatment. The BnA-IA-AMPS and PEA-AA-AMPS copolymers, whose zeta potentials were closer to 0 V than St-IA-AMPS , BnA-IA-AMPS , or St-AA-AMPS (−57 mV), resulted in significant sedimentation, indicating that the electrostatic repulsion between polymers is a dominant factor for stable dispersion. The PEA-AA-AMPS particularly showed poor stability of dispersion as observed for block copolymer consisting of PEA and quaternized pyridinium salt segments .…”

“…Similar rheological properties were observed for the color dispersions of cyan (DB 359) to those of yellow (DY 232) (Figure S8). Previously, we examined the viscosity of color dispersions with conventional poly­(St-co-AA) ( St-AA ) . Compared with St-AA , the rheological properties of amphiphilic polymers in this study, which contain the sulfonic acid group, are less Newtonian.…”

“…We previously reported a polymer dispersant consisting of St, AA, and AMPS ( St-AA-AMPS ) . According to previous studies, the sulfonic acid moieties served as effective hydrophilic molecular components , with potentials for moderate redispersion properties.…”