Which of the following is not a type of addition polymerization?

Polycondensation polymerization

The correct answer is option 2. Polycondensation polymerization.

Let us break down each type of polymerization:

1. Free radical polymerization: In this type of addition polymerization, the reaction is initiated by free radicals, which are highly reactive species with unpaired electrons. Free radicals are typically generated by initiators such as peroxides or azo compounds, which decompose to form free radicals under appropriate conditions (e.g., heat or light). These free radicals then attack the double bonds of monomers, initiating a chain reaction where monomers continuously add to the growing polymer chain. Examples of polymers produced through free radical polymerization include polyethylene, polystyrene, and polyvinyl chloride (PVC).

2. Polycondensation polymerization: Polycondensation polymerization involves the step-growth polymerization of monomers containing two or more reactive functional groups. During polycondensation, monomers react with each other to form polymer chains, typically accompanied by the elimination of small molecules such as water, alcohol, or hydrogen chloride. This process continues until the monomers are completely consumed or until the desired polymer chain length is achieved. Examples of polymers produced through polycondensation polymerization include polyesters, polyamides, and polycarbonates.

3. Anionic polymerization: Anionic polymerization involves the initiation of polymerization by negatively charged species known as anions. Anionic initiators, such as alkali metals or organometallic compounds, generate anions that attack monomers containing electron-deficient sites (such as carbon-carbon double bonds) to start the polymerization process. This reaction proceeds by successive addition of monomers to the growing polymer chain, resulting in the formation of high molecular weight polymers. Examples of polymers produced through anionic polymerization include polybutadiene and polyisoprene.

4. Cationic polymerization: Cationic polymerization involves the initiation of polymerization by positively charged species known as cations. Cationic initiators, such as Lewis acids or protic acids, generate cations that react with monomers containing electron-rich sites (such as carbon-carbon double bonds or heteroatoms) to initiate the polymerization process. Similar to anionic polymerization, cationic polymerization proceeds by successive addition of monomers to the growing polymer chain, resulting in the formation of high molecular weight polymers. Examples of polymers produced through cationic polymerization include polyisobutylene and polyvinyl ethers.

In summary, free radical polymerization, anionic polymerization, and cationic polymerization are all types of addition polymerization, where monomers add to each other in a chain reaction without the formation of byproducts. On the other hand, polycondensation polymerization involves the step-growth polymerization of monomers with the elimination of small molecules as byproducts.