Question

What is condensation polymerization, and how does it differ from addition polymerization? Give an example of a common condensation polymer.

Short answer

Condensation polymerization is a process where monomers react with each other to form a polymer, along with the release of a small byproduct molecule like water, alcohols, or hydrochloric acid. This differs from addition polymerization, where monomers containing double bonds or other reactive groups join together to form a polymer without any byproduct. The main differences between the two are the byproducts, monomers involved, and reaction mechanisms. A common example of a condensation polymer is polyester, such as polyethylene terephthalate (PET), used in making fibers, films, and plastic bottles.

Step-by-step solution

Define condensation polymerization

Condensation polymerization is the process in which monomers react with each other to form a polymer, along with the release of a small byproduct molecule, such as water, alcohols, or hydrochloric acid. The process generally occurs in two functional groups, such as acids and amines, esters and alcohols, or amides and acids.

Define addition polymerization

Addition polymerization, also known as chain-growth polymerization, is a process in which monomers containing double bonds or other reactive groups join together to form a polymer without the production of any byproduct. During this reaction, the double bond in the monomer breaks and forms a single bond with another monomer to create a long-chain polymer.

Differences between condensation and addition polymerization

1. Byproducts: In condensation polymerization, the reaction produces a small molecular byproduct, such as water or alcohol, while in addition polymerization, there are no byproducts. 2. Monomers: Condensation polymerization involves monomers with functional groups like acids, amines, esters, alcohols, or amides, while addition polymerization involves monomers with double bonds or other reactive groups. 3. Reaction mechanism: Condensation polymerization is a step-growth process, where the reaction takes place between functional groups on monomers, whereas addition polymerization is a chain-growth process, and the reaction occurs at the point of broken double bonds or reactive groups.

Example of a condensation polymer

An example of a condensation polymer is polyester, which is formed between ester and alcohol functional groups, resulting in the formation of ester linkages in the polymer chain. A common type of polyester is polyethylene terephthalate (PET), which is used in making fibers, films, and plastic bottles. The reaction that produces PET involves an ester functional group of terephthalic acid and an alcohol functional group of ethylene glycol, with water as a byproduct.

Key concepts

Condensation Polymerization

Condensation polymerization is a fascinating chemical process that results in the creation of large polymer chains. This process involves monomers that react together, often with the release of a small molecule as a byproduct, such as water or alcohol.

Here's how it works: the monomers have functional groups, like acids and amines, or esters and alcohols, which form bonds to create the polymer. A well-known example of this is the reaction between an acid and an alcohol to produce esters, where water is released.

What makes condensation polymerization unique is its step-growth process. This means that the formation of the polymer proceeds through steps involving the functional groups of the monomers. These steps continue until a long and stable polymer chain is formed.

- **Key Points**:

• Involves release of byproducts
• Utilizes functional groups
• Step-growth mechanism

Addition Polymerization

Addition polymerization, often referred to as chain-growth polymerization, is a process that builds polymers by joining monomers with double bonds or other reactive sites. Unlike condensation polymerization, no small molecules are released during this reaction.

In this process, the monomer's double bond breaks, allowing each monomer to connect with another, forming a long polymer chain. This rapid and straightforward connection is what characterizes addition polymerization.

It primarily involves monomers such as ethylene, which have unsaturated bonds. As these bonds break, they allow the addition of monomer units, thus elongating the polymer chain with great efficiency.

- **Highlights**:

• No byproducts are released
• Involves monomers with reactive groups
• Chain-growth process

Polyester

Polyesters are a group of polymers known for their robustness and versatility. They are a classic example of condensation polymers formed from the reaction between an ester and an alcohol.

A prominent type of polyester is polyethylene terephthalate (PET). This polymer is synthesized by reacting terephthalic acid (with an ester group) with ethylene glycol (with an alcohol group). The reaction forms ester linkages, and water is released as a byproduct.

Polyesters are widely used in everyday items, from clothing fibers to plastic bottles. They stand out due to their durable and flexible properties, making them ideal for various applications.

- **Common Uses of Polyester**:

• Textile fibers
• Plastic bottles
• Films

Functional Groups

Functional groups are pivotal to the polymerization processes as they determine the type of chemical reactions that monomers can undergo. They are specific groupings of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.

In the context of polymerization, functional groups in monomers such as acids, amines, esters, and alcohols are essential for forming condensation polymers. These groups allow the formation or breaking of bonds during polymerization.

For example, in condensation polymerization, functional groups react, resulting in the release of a small molecule like water. In addition polymerization, however, the reactive groups, such as double bonds, drive the chain-growth mechanism.

- **Examples of Functional Groups**:

• Carboxylic acids
• Amines
• Esters

These groups are fundamental to understanding the diversity and complexity of polymer chemistry.