Difference Between Ionic and Nonionic Surfactants

The key difference between ionic and nonionic surfactants is that the ionic surfactants contain elemental cations or anions present in its formulation whereas the nonionic surfactants have no cations or anions present in its formulation.

Surfactants are surface active agents. That means, these compounds can reduce the surface tension between two substances; two liquids, a gas and a liquid or a liquid and a solid. There are two main types of surfactants as ionic and nonionic. These two differ from each other according to the presence or absence of cations and anions in their structures.

CONTENTS

1. Overview and Key Difference
2. What are Ionic Surfactants
3. What are Nonionic Surfactants
4. Side by Side Comparison – Ionic vs Nonionic Surfactants in Tabular Form
5. Summary

What are Ionic Surfactants?

Ionic surfactants are the surface active agents containing cations or anions as in their formulations. There, the head of the surfactant molecule carries a net electrical charge. It can be either a positive charge or a negative charge. If the charge is positive, we name it as a cationic surfactant while if the charge is negative; we name it as an anionic surfactant. Sometimes, these compounds contain a head with two oppositely charged ionic groups; then we call it a zwitterionic surfactant.

When considering anionic surfactants, they contain negatively charged functional groups in the head of the molecule. Such functional groups include sulfonate, phosphate, sulfate and carboxylates. These are the most common surfactants that we use; ex: soap contain alkyl carboxylates.

When considering the cationic surfactants, they contain positively charged functional groups in the head of the molecule. Most of these surfactants are useful as antimicrobials, antifungal agents, etc. this is because they can disrupt the cell membranes of bacteria and viruses. The most common functional group that we can find in these molecules is ammonium ion.

What are Nonionic Surfactants?

Nonionic surfactants are the surface active agents that have no net electrical charge in their formulations. This means the molecule does not undergo any ionization when we dissolve it in water. Moreover, they have covalently bonded oxygen-containing hydrophilic groups. These hydrophilic groups bind with hydrophobic parent structures. These oxygen atoms can cause the hydrogen bonding of the surfactant molecules. Since the hydrogen bonding is affected by temperature, temperature increasing decreases the dissolution of these surfactants.

There are two major forms of nonionic surfactants according to the differences in their hydrophilic groups as follows:

• Polyoxyethylene
• Polyhydric Alcohols

What is the Difference Between Ionic and Nonionic Surfactants?

Ionic surfactants are the surface active agents containing cations or anions as in their formulations whereas nonionic surfactants are the surface active agents that have no net electrical charge in their formulations. Therefore, the key difference between ionic and nonionic surfactants is in their formulation. Furthermore, these two compounds differ from each other according to the presence or absence of an electrical charge on the head of the surfactant molecule.

The below infograhic presents the difference between ionic and nonionic surfactants in a tabular form.

Summary – Ionic vs Nonionic Surfactants

Surfactants are surface active agents which are useful to reduce the surface tension between two phases of matter. There are two types of ionic and nonionic surfactants. The difference between ionic and nonionic surfactants is that the ionic surfactants contain elemental cations or anions present in its formulation whereas the nonionic surfactants have no cations or anions present in its formulation.

Reference:

1. Hirsch, Marc, et al. “Surface Active Agents (Surfactants): Types and Applications.” Prospector Knowledge Center, 11 July 2018. Available here

Image Courtesy:

1.”TensideHyrophilHydrophob”By Roland.chem, (CC BY-SA 3.0) via Commons Wikimedia