What is the Difference Between Cationic and Anionic Polyelectrolyte

The key difference between cationic and anionic polyelectrolyte is that cationic polyelectrolytes can dissociate in aqueous solutions to form positively charged polymeric species, whereas anionic polyelectrolytes can dissociate in aqueous solutions to give negatively charged polymeric species.

Polyelectrolytes are polymers that have repeating units bearing an electrolyte group. There are two types: polycations or cationic polyelectrolytes and polyanions or anionic polyelectrolytes. These cationic and anionic groups can dissociate in aqueous solutions consisting of water and make the charged polymer species. Therefore, the properties of polyelectrolytes are similar to electrolytes such as salts and polymers having a high molecular weight. Therefore, we can name them polysalts.

CONTENTS

1. Overview and Key Difference
2. What is Cationic Polyelectrolyte
3. What is Anionic Polyelectrolyte
4. Cationic vs Anionic Polyelectrolyte in Tabular Form
5. Summary – Cationic vs Anionic Polyelectrolyte 

What is a Cationic Polyelectrolyte?

Cationic polyelectrolytes are polymers having positively charged moieties and anionic counterions existing on each repeating unit or in a large portion of units. The most common functional groups in these cationic polyelectrolytes include ammonium, phosphonium, and imidazolium groups.

Generally, we can see physical cross-links in these polymers that occur through electrostatic interactions. These are often known as supramolecular interactions. Typically, electrostatic interactions are not as strong as covalent bonds. However, these electrostatic interactions can enable higher thermal transitions and proper mechanical properties in comparison to non-ionic polymers.

Furthermore, cationic polyelectrolytes are useful in water treatment, anti-microbial materials, and non-viral gene delivery. This is mainly because of the molecular tuning weight, positively charged moiety, anionic counterion, or charge density that cationic polyelectrolytes can afford, etc.

What is an Anionic Polyelectrolyte?

Anionic polyelectrolytes are polymers having negatively charged moieties and anionic counterions existing on each repeating unit or in a large portion of units. There can be various types of anionic polyelectrolytes; acrylamide-based polymers as the most common form. Furthermore, the occurrence of sulfonic groups in these substances can make them sensitive to pH.

Anionic polyelectrolytes are widely useful as flocculants, rheology controlling agents, and adhesives. Moreover, these polymeric materials are important in the treatment of municipal wastewaters and effluents from industries, mainly including mineral processing. In addition, there are some other applications as well; oil recovery, color removal, paper making, mineral processing, etc.

What is the Difference Between Cationic and Anionic Polyelectrolyte?

Cationic and anionic polyelectrolytes are polymeric materials with different charges. Cationic polyelectrolytes are polymer materials having positively charged moieties and anionic counterions existing on each repeating unit or in a large portion of units. Anionic polyelectrolytes, on the other hand, are polymer materials having negatively charged moieties and anionic counterions existing on each repeating unit or in a large portion of units. The key difference between cationic and anionic polyelectrolyte is that cationic polyelectrolytes can dissociate in aqueous solutions to form positively charged polymeric species, whereas anionic polyelectrolytes can dissociate in aqueous solutions to give negatively charged polymeric species.

The below infographic presents the differences between cationic and anionic polyelectrolyte in tabular form for side by side comparison.

Summary – Cationic vs Anionic Polyelectrolyte

Polyelectrolytes are polymer materials that have repeating units bearing an electrolyte group. There are two types of polyelectrolytes as polycations or cationic polyelectrolytes and polyanions or anionic polyelectrolytes. The key difference between cationic and anionic polyelectrolyte is that cationic polyelectrolytes can dissociate in aqueous solutions to form positively charged polymeric species, whereas anionic polyelectrolytes can dissociate in aqueous solutions to give negatively charged polymeric species.

Reference:

1. Wilts, Emily M, et al. “Addressing Water Scarcity: Cationic Polyelectrolytes in Water Treatment and Purification.” Wiley Online Library, John Wiley & Sons, Ltd, 25 Apr. 2018.

Image Courtesy:

1. “Polyelectrolyte examples” By Kebes at en.wikipedia – Transferred from en.wikipedia by Ronhjones (Public Domain) via Commons Wikimedia