Question

directs you to the Chemistry in Focus feature in the chapter What, in general terms, is a polymer? What is a monomer?

Short answer

A polymer is a large molecule composed of many smaller repeating units called monomers, which are chemically bonded together to form long chains or networks. Polymers can be natural or synthetic. A monomer is a small molecule that can chemically bond with other monomers to form a polymer, acting as its building block. The process of forming a polymer from monomers is called polymerization.

Step-by-step solution

Define Polymer

A polymer is a large molecule made up of many smaller, repeating units called monomers. These monomers are chemically bonded together to form long chains or networks. Polymers can be natural, like proteins and cellulose, or synthetic, like plastics and rubber.

Define Monomer

A monomer is a small molecule that can chemically bond with other monomers to form a polymer. It acts as the building block of a polymer and combines with other monomers through various chemical reactions, such as polymerization or condensation. Examples of monomers include ethylene, propylene, and styrene.

Relationship between Polymers and Monomers

Polymers and monomers are closely related concepts, as polymers are made up of monomers. The process of forming a polymer from monomers is known as polymerization. Monomers are the building blocks that combine to create the larger, more complex structure of the polymer.

Key concepts

Monomers

Monomers are the basic building blocks of polymers. These small molecules have the unique ability to link together through chemical reactions. Each monomer is like a single pearl that can string together with others to form a necklace, which we can think of as the polymer.

The nature of monomers can vary greatly. They can be very simple, like ethylene which is a single carbon atom bonded to two hydrogen atoms. Or they might be more complex, with multiple atoms intricately connected together. What makes monomers special is their capacity to react with similar or different monomers.

• Monomers have reactive sites which allow them to bond with other monomers.
• They can form repetitive sequences which give the polymer its specific characteristics.

Understanding monomers is crucial because they determine the properties of the resulting polymer. For instance, changing the type of monomer used can dramatically alter the strength, flexibility, and resistance of the polymer.

Polymerization

Polymerization is the process that transforms monomers into polymers. It’s a chemical reaction where individual monomer units bond together sequentially. Much like building a tower with blocks, each monomer adds to the growing chain until a long, stable polymer is formed.

There are several types of polymerization, but they generally fall into two categories:

• Addition Polymerization: Monomers add to each other without the loss of any small molecules. Ethylene forming polyethylene is an example of this type.
• Condensation Polymerization: Monomers join together and release small molecules, often water, in the process. Nylon and polyester are products of condensation polymerization.

These reactions can proceed through different mechanisms, involving either free radicals, cations, or anions, and they can be initiated by heat, light, or catalysts. Polymerization not only shapes the size of the polymer but also its structure, impacting everything from durability to optical properties.

Chemical Bonding

Chemical bonding is at the heart of both the formation and functionality of polymers. Bonds are the connections that hold monomers together to form stable, long-lasting polymeric structures. In polymers, these bonds are typically covalent, meaning atoms share electrons.

There are different types of bonds and interactions that play key roles in polymers:

• Covalent Bonds: These form the backbone of the polymer, linking monomer units in a chain or network.
• Hydrogen Bonds: While weaker than covalent bonds, these can significantly affect the properties of polymers, such as nylon, by providing additional strength and stability.
• Ionic Bonds: Polymers containing ionic bonds usually have charged groups that affect the solution properties of the polymer.
• Van der Waals Forces: These weak interactions can influence how polymer chains pack together, affecting properties like crystallinity and melting behavior.

Understanding the nature of these bonds allows scientists to tailor polymers for specific applications, creating materials that meet specific needs, whether it be flexible plastics or strong, durable fibers.