Polyacrylamide (PAM) is a type of polymer that can be classified into two categories based on their ionic charge: anionic and cationic PAM. The main difference between these two types lies in their charge properties.

Anionic PAM contains negatively charged functional groups, such as carboxylate (-COO-) or sulfate (-SO3-). These groups give the polymer a net negative charge, which makes it highly soluble in water and able to attract positively charged particles, such as metal ions or organic molecules with cationic properties. Anionic PAM is commonly used for wastewater treatment, oil recovery, and soil stabilization.

On the other hand, cationic PAM has positively charged functional groups, such as quaternary ammonium (-NR4+) or amino (-NH2) groups. These groups impart a positive charge to the polymer, allowing it to bind to negatively charged particles, such as clay minerals, organic matter, or bacteria. Cationic PAM is frequently used as a flocculant, coagulant, or dispersant in various industrial applications, including papermaking, textiles, and mining.

In summary, the key difference between anionic and cationic PAM lies in the sign and location of their ionic charges, which determine their behavior in different environments and applications.