Polymer

Definition

A polymer is a large molecule composed of repeating structural units called monomers, which are connected by covalent bonds. Polymers are the foundation of chain-growth polymerization reactions, where monomers link together to form long, complex macromolecules.

5 Must Know Facts For Your Next Test

1. Polymers can be naturally occurring, such as proteins and nucleic acids, or synthetic, such as plastics and rubbers.
2. The properties of a polymer, such as its strength, flexibility, and melting point, are determined by the type and arrangement of its monomers.
3. Chain-growth polymerization is a type of addition polymerization where monomers are added one at a time to the growing polymer chain.
4. Radical addition to alkenes is a common mechanism for chain-growth polymerization, where a free radical initiator starts the reaction and propagates the chain.
5. The molecular weight and distribution of a polymer can significantly impact its physical and mechanical properties.

Review Questions

• Explain the role of monomers in the formation of polymers.
  • Monomers are the basic structural units that make up a polymer. Through a process called polymerization, monomers are covalently bonded together to form long, repeating chains of molecules known as polymers. The type and arrangement of monomers determine the properties and characteristics of the resulting polymer, such as its strength, flexibility, and melting point.
• Describe the key features of chain-growth polymerization, and how it relates to radical additions to alkenes.
  • Chain-growth polymerization is a type of addition polymerization where monomers are added one at a time to the growing polymer chain. This process is often initiated by a free radical, which can be generated through the radical addition to an alkene monomer. The free radical then propagates the chain reaction, adding more monomers to the growing polymer. The mechanism of radical additions to alkenes is a common pathway for chain-growth polymerization, as it allows for the controlled and efficient formation of long-chain polymers.
• Analyze how the molecular weight and distribution of a polymer can impact its physical and mechanical properties.
  • The molecular weight and distribution of a polymer are critical factors that influence its physical and mechanical properties. Higher molecular weight polymers generally have stronger intermolecular forces and entanglements, resulting in increased tensile strength, stiffness, and resistance to deformation. However, if the molecular weight distribution is too broad, it can lead to uneven properties and inconsistent performance. Optimizing the molecular weight and distribution is essential for tailoring a polymer's characteristics to meet specific application requirements, such as flexibility, toughness, or thermal stability.

Related terms

Monomer:

A monomer is a small molecule that can be bonded to other identical molecules to form a polymer.

Chain Reaction:

A chain reaction is a sequence of reactions where a reactive intermediate, such as a free radical, triggers further reactions that produce more of the same type of reactive intermediate.

Macromolecule: A macromolecule is a very large molecule, such as a polymer, that is composed of a large number of smaller structural units.