Functional polymers for colloidal applications (III): Structural effects of lipophile‐modified styrene‐maleic anhydride copolymers on dispersing polar and nonpolar particles

Styrene‐maleic anhydride copolymer (SMA) with the molecular weight (MW: 7100) suitable for acting as a dispersant was synthesized and then ring‐opened with alkylamine to prepare the n‐butyl and n‐dodecyl‐substituted SMA. The prepared lipophile‐modified SMA copolymers were used as dispersants to disperse both polar and nonpolar particles (TiO₂ and carbon black). Upon dispersing TiO₂ and carbon black, the antibridging effect (a larger optimum concentration and a less sharp increase after optimum concentration) was observed for SMA as well as n‐butylamide‐substituted SMA as compared to sodium polyacrylate. The bridging effect, however, is obvious for n‐dodecylamide highly substituted SMA (12N45). For dispersing TiO₂, both for n‐butyl and n‐dodecylamide‐substituted SMA, the curve of viscosity vs. concentration increases less sharply after optimum concentration except for 12N45. In the case of dispersing carbon black, the n‐butylamide‐substituted SMA shows a pronounced antibridging effect, while the n‐dodecylamide‐substituted SMA shows a significant bridging effect. The minimum viscosity and the optimum concentration for both n‐butyl and n‐dodecylamide‐substituted SMA are correlated to conclude that: (a) at low percentage of alkylamide in SMA, both for n‐butyl and n‐dodecyl group cause bridging phenomena and increase the viscosity; (b) as the percentage of alkylamide in SMA increase, the adsorption effect is more important for n‐butylamide‐substituted SMA (e.g., 4N45), and the bridging effect is more important for n‐dodecylamide‐substituted SMA (e.g., 12N45); (c) the decrease in optimum concentration for 12N45 can be interpreted by the bridging effect.