Addition polymerization

Definition

Addition polymerization is a chemical reaction where unsaturated monomers, containing double or triple bonds, combine to form a polymer without the loss of any small molecules. This type of polymerization involves the breaking of these double or triple bonds, resulting in the formation of long-chain molecules. The process can be initiated through various means, including heat, light, or chemical initiators, and leads to the creation of a wide range of materials used in everyday products.

5 Must Know Facts For Your Next Test

1. Addition polymerization typically occurs with monomers that have at least one carbon-carbon double bond (C=C) or triple bond (C≡C).
2. Common examples of addition polymers include polyethylene, polystyrene, and polyvinyl chloride (PVC), which are widely used in packaging and construction.
3. The process can be initiated through various methods such as radical initiation, cationic initiation, or anionic initiation, allowing for different types of polymers.
4. Unlike condensation polymerization, addition polymerization does not release by-products; the mass of the resulting polymer is equal to the sum of the masses of the monomers used.
5. The degree of polymerization, which refers to the number of repeating units in the polymer chain, can greatly influence the properties of the final material.

Review Questions

• How does the structure of monomers affect the process of addition polymerization?
  • The structure of monomers is crucial in addition polymerization because they must possess reactive functional groups such as carbon-carbon double bonds or triple bonds. These unsaturated bonds are what allow for the initiation and propagation steps in the reaction. When these bonds break during polymerization, they create new single bonds as monomers link together, forming long-chain polymers. Therefore, the presence and nature of these unsaturated bonds directly determine how efficiently and rapidly addition polymerization can occur.
• Compare and contrast addition polymerization with condensation polymerization in terms of their mechanisms and by-products.
  • Addition polymerization involves the direct linking of monomers with unsaturated bonds without producing by-products; all atoms from the monomers are retained in the final polymer. In contrast, condensation polymerization involves a reaction between two different types of monomers that results in the formation of covalent bonds while releasing small molecules like water or alcohol as by-products. This difference in mechanism affects not only the resulting polymers' structure but also their properties and applications in various fields.
• Evaluate the importance of controlling conditions during addition polymerization and its impact on the properties of the resulting polymers.
  • Controlling conditions during addition polymerization is critical as it influences both the rate of reaction and the properties of the resulting polymers. Factors such as temperature, pressure, and concentration of initiators can affect chain length, molecular weight distribution, and overall mechanical properties like strength and flexibility. For instance, a high temperature might increase reaction rates but could lead to undesired branching or cross-linking in some cases. Thus, understanding how to manipulate these conditions allows chemists to tailor materials for specific applications, enhancing their performance in everyday use.

Related terms

Monomer: A small, reactive molecule that can join together to form a polymer through chemical reactions.

Free Radical: An unstable atom or molecule with unpaired electrons that can initiate the addition polymerization process.

Condensation Polymerization: A type of polymerization where monomers join together while releasing small molecules, often water, as by-products.