Functional polymers for colloidal application. VIII. Syntheses of anionic and zwitterionic aniline–formaldehyde condensates and their dispersing ability to zwitterionic clay

Anionic and zwitterionic aniline–formaldehyde condensates have been synthesized by a methylenation under mild reaction conditions and a reaction with propane sultone. The formation of condensates is characterized by NMR, i.e., the peak of methylene at δ = 3.5−4.0 ppm and the peaks of propylsulfonate at δ = 2.7−3.4 ppm and δ = 1.7−2.2 ppm. The results from GPC show that a longer condensation time increases the degree of polymerization of the condensates. The dispersing properties of the condensates are assessed by the viscosity, scanning electron microscopy (SEM), and adsorption behaviors. N,N‐dimethyl‐N‐(3‐propylsulfonate) anilinium–formaldehyde condensates (DPSAF) with higher molecular weight (DPSAF‐H) show significantly lower apparent viscosities. Comparing the results of SEM and the viscosity method, it can be concluded that, under comparable conditions, a suspension with a lower viscosity is more homogeneously dispersed. The amount of DPSAF‐H adsorbed onto clay is significantly higher than that of PSAF‐H at low concentrations of the dispersant and reaches an optimum after ca. 3 wt %. This result is in parallel with the trend of viscosity. The zwittionic DPSAF promotes their dispersing ability of clay in water due to the existence of the positive and negative charges. The decrease in the amount of adsorbed PSAF‐H with increasing pH can be interpreted by the increased negative charge of the clay, as a result of the decreased interaction between the anionic PSAF‐H and the clay. © 1993 John Wiley & Sons, Inc.