Due to the different natural state of pigment surface, polymer dispersants with different anchoring groups can be selected according to their chemical structure to produce anchoring effect. Anchorage can occur through different processes:

★ By ion or acid/basic groups to produce anchoring

When the surface activity of pigment particles is high, the charge potential on the surface of pigment particles can form ionic bond with the opposite charge site or functional group of dispersant. In fact, many inorganic pigment particles have very complex surfaces with both positive and negative charge sites. Therefore, when the pigment is dispersed by dispersing agent, the groups with negative charge and positive charge can be anchored with it. Functional groups that can anchor with charged or acidic/alkaline surfaces are: amines; Ammonium and quaternary ammonium; Carboxylic acid, sulfonic acid and phosphoric acid groups and their salts; And sulfates and phosphate esters.

★ Anchorage through hydrogen bonding

Although organic pigment particles are relatively more inert than inorganic pigments, hydrogen bond donors and acceptors are possible, so it is possible to form hydrogen bonds between the particles and the anchoring groups of the polymer dispersant. Individual hydrogen bonds may be weak, but polymer dispersants contain many anchoring chain segments with hydrogen bond donors and acceptors, so the interaction between pigment particles and dispersants can be greatly enhanced. Polyamines and polyhydroxyl compounds have both donors and acceptors and can produce anchorage through see. Polyether can produce anchorage through hydrogen bond receptors.

★ Through polar groups to produce anchoring

Organic pigment particles have polar or polarizable groups on the surface, similarly, there are polar or polarizable anchoring genes in polymer dispersants. Thus anchoring can also occur. Again, this interaction is usually relatively weak, but is reinforced in polymer dispersants when multiple such groups are combined into a anchored chain segment. Polyurethanes are usually used as polar anchorage groups.

★ Anchorage is formed through insoluble polymer chain segment

Without ionic, hydrogen, or polar bonding, van der Waals forces alone can bind the surface of the pigment particles to the polymer dispersant through anchorage. The polymeric chain segment in the dispersant is only required to be insoluble in the medium.

Polyurethane anchorage groups may be formed in this way. In fact, it is difficult in practice to distinguish this from the previous two adsorption processes. Most polymer segments are likely anchored by a mixture of electrostatic forces (hydrogen bonding and/or polarity) and van der Waals forces. One of these processes may be dominant, but most efficient polymer dispersants are likely to produce all three and maximize their efficacy.

★ The anchoring effect is formed by synergistic dispersant

Some organic pigments (phthalein blue, etc.) by changing the chemical structure of the ion itself, the derivatives of ionic groups make the ionic surface of the pigment selectively activated, so that it can act with the charged anchor group in the polymer dispersant. The derivative can also be adsorbed on the surface of pigment due to its similar polarity. This bridging effect makes the pigment which is difficult to be anchored get a good stability effect.