The Difference Between Addition and Condensation Polymerization

Polymerization is the process of combining monomers to create a polymer. There are two main types of polymerization: addition and condensation. Despite their similar names, they differ greatly in the way they work.

Addition Polymerization

Addition polymerization occurs when monomers combine without any byproducts, such as water or alcohol, being formed. In this process, the monomers are joined through a double bond or a triple bond, which is broken during the polymerization process. As a result, the monomers add on to each other to form the polymer chain.

The reaction is initiated by a catalyst, which can be heat or light. The reaction is fast and yields a high molecular weight polymer. The final polymer has a uniform chemical structure without any side products. Addition polymerization is commonly used to form polymers like polyethylene, polypropylene, and polyvinyl chloride.

Condensation Polymerization

Condensation polymerization occurs when two or more monomers combine and a byproduct is formed, such as water or alcohol. This type of polymerization happens when molecules with two or more functional groups, such as carboxylic acid or alcohol, react with each other. During polymerization, the functional groups combine, leading to the formation of a polymer chain, while the byproduct is eliminated.

The reaction is slower compared to addition polymerization because of the byproduct formation. The molecular weight distribution of the final polymer is not uniform as some monomers might not participate in the reaction, leading to a mixture of different-sized chains. Condensation polymerization is commonly used to form polymers like nylon and polyester.

The Bottom Line

In summary, the addition polymerization involves the formation of a polymer without any by-products, while condensation polymerization involves the formation of a polymer with a by-product elimination. The type of polymerization chosen depends on the desired properties and application of the final polymer product. Understanding the difference between these two types of polymerization can help in the development of new polymer materials for various applications.

Table difference between addition and condensation polymerization

Addition vs Condensation Polymerization

Aspect	Addition Polymerization	Condensation Polymerization
Definition	Increase in molecular weight by the addition of unsaturated monomers with no by-products.	Increase in molecular weight by the elimination of small molecules as by-products.
Mechanism	Chain polymerization or stepwise polymerization.	Step growth polymerization or polycondensation.
Monomer Properties	Monomers are unsaturated and contain a reactive carbon-carbon double bond.	Monomers are bifunctional or multifunctional with different or similar reactive groups.
Initiation Process	Initiated either by a catalyst or a radical initiator.	Initiated by heating, catalysis or radiation.
By-Products	No by-products.	Small molecules like water, alcohol, or HCl are eliminated during the process.
Reaction Conditions	Occurs under moderate reaction conditions	Occurs under severe reaction conditions as high temperature and/or vacuum.
Polymer Properties	High molecular weight and low dispersity. Ideal for creating elastic and thermoplastic materials.	Low molecular weight and high dispersity. Suitable for creating adhesive and coating materials.