Types of Polymerisation Reactions

The polymerisation reaction is a chemical reaction in which many monomer molecules combine to produce a polymer. The macromolecules formed due to polymerisation can have either a linear or a branched structural arrangement. They can also take the form of a complicated, three-dimensional network when viewed from above. Polymerisation reactions can be classified into several categories.

Polymerisation Reactions

An organic substance combines, in a condensation reaction, to generate a high-molecular-weight compound made of repeating units of the original chemical. Copolymerisation and heteropolymerization are terms used to describe the process of joining two or more monomers together.

Polymerisation Reactions differ from other processes, such as crystallisation, in that it results in the development of stable covalent chemical bonds between the monomer molecules.

In plastics, the polymerisation reaction is significant since it is the process through which polymers are created. It impacts a wide range of daily life areas since polymerisation involves everything that has to do with plastic, textiles, or elastomers.

There are two types of polymerisation:

•  Additional Polymerisation

• Condensation Polymerisation

Additional Polymerisation

Types of additional polymerisation:

Additional polymerisation consists of different types of polymerisation.

• Solution Polymerization: When using a non-reactive solvent with an initiator or catalyst to speed up the reaction, a monomer is dissolved in the non-reactive solvent. The reaction is then carried out at a faster rate. The polymer generated throughout the procedure is also soluble in the same non-reactive solvent used throughout the operation.

• Bulk Polymerization: Large-scale polymerisation, also known as mass polymerisation, is produced by mixing a radical initiator with a pure monomer to produce large-scale polymerisation. Although the monomer should be in a liquid form, the radical initiator should be soluble in the monomer’s solution. A positive exothermic reaction has occurred in this process.

• Emulsion Polymerization: A monomer, water that contains an emulsion, and a surfactant are used in the radical polymerisation process known as emulsion polymerisation.

• Suspension Polymerization: In this technique of heterogeneous radical polymerisation, mechanical agitation is utilised to combine monomers while they are still in their liquid states.

• Free Radical Polymerization: An additional polymer is formed when an atom with a free electron in its valence shells is added to another atom in its valence shells. Free radicals are what these are referred to as. During the free radical polymerisation process, they form a continuous chain. The most straightforward method of catalysing the polymerisation process that results in an additional polymer is to combine the monomer with a source of free radicals. The phrase “free radical” refers to a group of extremely reactive, short-lived components of a reaction that include one or more unpaired electrons and are hence highly reactive. A chain-reaction mechanism, which includes processes for chain-initiation, chain-propagation, and chain-termination, is responsible for forming additional polymers in the presence of a free radical.

1. Chain initiation step

The chain reaction begins when the phenyl free radical produced by the peroxide is added to the ethene double bond, resulting in a new and larger free radical. This phase is known as the chain beginning stage.

2. Chain propagation step

The continuation of this cycle with fresh and larger radicals propels the reaction onward, and this stage is referred to as chain propagation.

3. Chain terminating step

At some point, the product radical interacts with another radical to form the polymerised product. This is known as the chain-terminating step.

Cationic Polymerization: 

Cationic Polymerization is where a cation is generated due to the formation of a polymer, which leads to a chain reaction. It leads to the formation of a lengthy chain of monomers that are repeated.

Anionic Vinyl Polymerization:

The polymerisation reaction of vinyl polymers, particularly those with a strong electronegative group, results in a chain reaction’.

Coordination Polymerisation:

Coordination polymerisation is a process that was developed by two scientists, Ziegler and Natta, who were awarded the Nobel Prize for their research. They created a catalyst to control the free radical polymerisation process. It results in a polymer that is denser and stronger than the original.

Condensation Polymerization

Adding additional polymers to monomers having C=C double bonds is not difficult; in fact, many of these compounds polymerise spontaneously unless polymerisation is purposefully suppressed, which is the case in many cases.

For example, one of the difficulties associated with early refining procedures for gasoline was the polymerisation of alkene components as the gasoline was stored. Even with contemporary types of gasoline, deposits of “gunk” can accumulate on the carburettors of a car or motorbike if it is left in storage for a long time without being drained.

Difference Between two types of Polymerisation (Addition Polymerisation and Condensation Polymerisation)

To better understand the two forms of polymerisation, let us perform a comparative examination of them.

• Aside from that, during polymerisation, monomers exclusively join at the chain’s active site. Any molecule can react with any other in condensation polymerisation, though.

• There are three separate phases in addition to polymerisation. Start, spread, and eventually, the end is all process stages. There is no ending step in the process of condensation polymerisation. Throughout the procedure, the final groups maintain their reactivity.

• Homo-chain polymers are formed by addition polymerisation, whereas hetero-chain polymers are formed by condensation polymerisation.

• What distinguishes addition polymers from other polymers is that no atom is lost during the addition process. However, as a by-product of a condensation reaction, a water molecule, ammonia, or another substance is lost.

Conclusion

The polymerisation reaction employed in polymers synthesis allows for the latter’s division into two primary types: addition polymers and condensation polymers. The former kind is created by monomers’ repetitive and sequential addition, with no loss of a smaller molecule occurring throughout the process. As a result, no by-product is created. The repeating unit of new polymers has the same formula as the alkene or functionally-substituted alkene monomers used to create them.