Which type of polymer creates negative sites when dissolved in water?

Anionic polymers are characterized by their ability to develop negative sites when dissolved in water. This occurs because anionic polymers contain functional groups that can ionize and release negatively charged ions (anions) into the solution. These anions can be derived from carboxylic acid groups (-COOH), sulfonate groups (-SO3H), or similar functional groups that fully dissociate in the presence of water, thereby contributing to the overall negative charge of the polymer in solution.

This property is significant in various applications, including wastewater treatment, where anionic polymers can help in capturing positively charged contaminants, or in drug delivery systems, where they can interact favorably with positively charged entities due to their negative sites.

The other types of polymers mentioned either do not form negative sites or behave differently in solutions. Cationic polymers tend to have positive charges, whereas non-ionic polymers do not ionize at all and remain neutral in solution. Therefore, anionic polymers are the correct answer due to their distinct chemical behavior in aqueous environments.