Condensation Polymerization
Condensation Polymerization
Condensation Polymerization is a type of polymerization that involves a step-growth mechanism, where bi-functional or multifunctional monomers react to form larger molecular structures. This process typically results in the loss of small molecules, such as water or methanol, as byproducts. Unlike chain-growth polymerization, which involves the addition of monomers one at a time, condensation polymerization involves stepwise reactions between functional groups of the monomers.
Step-Growth Polymerization
Condensation polymerization is synonymous with step-growth polymerization. In this process, the polymerization of bi-functional and multifunctional monomers occurs via the formation of covalent bonds between their functional groups. Typical examples include the formation of polyesters and polyamides. For instance, the creation of Nylon 66 involves the reaction between adipic acid and hexamethylene diamine.
Condensation Reactions
The backbone of condensation polymerization is the condensation reaction. This type of chemical reaction involves the combination of two molecules to form a larger molecule, usually with the loss of a smaller molecule such as water. Classical examples include the Claisen condensation and the Dieckmann condensation. The formation of esters and amides are typical condensation reactions in the context of polymerization.
Types of Condensation Polymers
Polyesters
Polyesters are formed via the condensation polymerization of dicarboxylic acids and diols. One of the most common examples is polyethylene terephthalate (PET), often used in the manufacture of plastic bottles and textile fibers. The reaction involves the esterification of terephthalic acid with ethylene glycol.
Polyamides
Polyamides, such as Nylon 6 and Nylon 66, are another class of condensation polymers. These are typically formed by the reaction of diamines with dicarboxylic acids. The process involves the formation of amide bonds, releasing water as a byproduct.
Polycarbonates
Polycarbonates are formed through the reaction of bisphenol A with phosgene. This type of condensation polymerization also releases small byproducts and results in a polymer with excellent strength and transparency, commonly used in eyewear lenses and compact discs.
Naturally Occurring Condensation Polymers
Condensation polymerization is not limited to synthetic polymers; it is also prevalent in naturally occurring polymers. Examples include:
- Cellulose: Formed by the condensation of glucose units.
- Proteins: Composed of amino acids linked by peptide bonds.
- Starch: Another polysaccharide formed by glucose monomers.
Comparison with Addition Polymerization
In contrast to addition polymerization, where no byproducts are released, condensation polymerization typically results in the loss of small molecules. Addition polymers like polyethylene and polystyrene are formed via chain-growth mechanisms, which differ significantly from the step-growth mechanisms of condensation polymers.
Applications
Condensation polymers have a myriad of applications due to their diverse properties. For example:
- Nylons: Used in textiles, automotive components, and industrial applications.
- Polyesters: Widely used in fabrics, plastic containers, and films.
- Polycarbonates: Utilized in eyewear, medical devices, and electronics.