91Ó°ÊÓ

Polymerization is the process of creating polymers from smaller molecules known as monomers. Polymers are large molecules composed of repeating structural units, usually connected by covalent chemical bonds. There are two major types of polymerization techniques: addition (chain-growth) polymerization and condensation (step-growth) polymerization.

In addition polymerization, the monomers contain a double bond or other reactive groups that form a new covalent bond without the elimination of any atoms or molecules during the process. The monomers join together in a chain-like manner, where the growth of the polymer occurs by the successive addition of monomers to an active site on the growing chain. The monomers usually contain a single bonding unit, and the process rapidly forms long polymer chains. Common examples of addition polymers are polyethylene and polypropylene.

In condensation polymerization, the monomers contain two or more reactive groups that can react with each other to form a new covalent bond with the elimination of small molecules like water or methanol during the reaction. The polymer grows through stepwise reactions between the functional groups of different monomers, producing a variety of chain lengths at any point in the process. This type of polymerization can involve monomers with two different reactive groups or two identical reactive groups. Examples of condensation polymers include polyesters, polyamides, and polyurethanes.

The primary differences between addition and condensation polymerization techniques can be summarized as follows: 1. Monomer's reactive groups: In addition polymerization, the monomers contain a single reactive group, whereas in condensation polymerization, the monomers contain two or more reactive groups. 2. Reaction mechanism: Addition polymerization involves a chain-growth mechanism, where the polymer chain grows rapidly and continuously as monomers are added to the active site. On the other hand, condensation polymerization follows a step-growth mechanism, where the polymer chain grows through a series of stepwise reactions involving different monomers. 3. By-products: Addition polymerization does not involve the elimination of any atoms or molecules during the process, while condensation polymerization creates small molecules as by-products (e.g., water or methanol) during the formation of the polymer. 4. Polymer chain length: In addition polymerization, long polymer chains are formed rapidly, whereas in condensation polymerization, a variety of chain lengths are produced during the process. 5. Examples: Common examples of addition polymers include polyethylene and polypropylene, while examples of condensation polymers include polyesters, polyamides, and polyurethanes.