Effects of the side chain density of polycarboxylate dispersants on dye dispersion properties

Comb-like polycarboxylates were synthesised by copolymerisation of methacrylic acid and nonylphenol polyethylene glycol methacrylate ester, and can be used as dye dispersants. In order to achieve good dispersive ability, three polycarboxylates were synthesised, each having a different side chain density. The side chain density of polymers was controlled by different ratios of monomers in the copolymerisation process. Acidic polymers were neutralised using sodium hydroxide. These polymers exhibit good dispersing performance, such that carboxylate groups are adsorbed onto the dye particle surface and the side chains enable the formation of a thick layer, thus providing the steric hindrance effect. Improvement of dye dissolution in the presence of polycarboxylates was studied. Polymers with a lower side chain density demonstrated a higher dye dissolution in water, which could be as a result of more effective adsorption of dispersant on the dye surface (CI Disperse Blue 79). The dyeing performance of the prepared dye dispersions on polyester was investigated. Spectrophotometric analysis of dyed fabrics using synthesised polycarboxylates demonstrates that there should be an optimum side chain density of polymer in order to control both dye solubility and dispersive ability. The result of turbidimetry and particle size analysis have proven this phenomenon. A comb-like polycarboxylate with optimum side chain density was a better dye dispersant compared with a commercial sodium naphthalene sulphonate compound, as a result of its better heat stability.