Key difference - addition polymerization vs. condensation polymerization
Polymerization is the process by which a large number of small molecules are assembled into very large molecules. Monomers are the building blocks of polymers. Based on the type of chemical reaction involved in the formation of a polymer, there are two types of polymerization reactions: addition polymerization and condensation polymerization. Addition polymerization produces addition polymers through the addition of olefinic monomers without the formation of by-products. In contrast, condensation polymerization creates condensation polymers by the intermolecular condensation of two different monomers to form small molecules such as HCl, water, ammonia, etc. as by-products. This is the main difference between addition polymerization and condensation polymerization. In addition to this key difference, there are many other differences between these two polymerization reactions.
This article covers
1. What is addition polymerization? - Process, properties, type of polymers produced, examples
2. What is condensation polymerization? - Process, properties, type of polymers produced, examples
3. What is the difference between addition polymerization and condensation polymerization?
What is addition polymerization?
Addition polymerization is the addition of one monomer to another monomer to form long chain polymers. There are no by-products in this process. Therefore, the molecular weight of the polymer is an integral multiple of the molecular weight of the monomer. The monomers involved in these reactions must be unsaturated (double or triple bonds must be present). During the reaction, unsaturated bonds open and form covalent bonds with neighboring monomer molecules to form long chain polymers. Besides addition polymerization, there are three types of mechanisms, namely; radical mechanism, ionic mechanism, coordination mechanism. Polymers made by the addition polymerization process are called addition polymers. Examples of addition polymers include polyvinyl chloride or PVC, poly ( propylene ) , poly (tetrafluoroethene) or TEFLON, etc.
Formation of PVC
What is condensation polymerization?
Condensation polymerization is the process of intermolecular condensation of two different monomers to form a large chain of polymer molecules. In this process, the linkage of any two monomer molecules results in a simple molecule such as HCl, ammonia, water, etc. as a by-product. Therefore, the molecular weight of the polymer is the product of the degree of polymerization and the molecular weight of the repeating unit. The polymers formed by condensation polymerization are referred to as condensation polymers . Bakelite, nylon, and polyester are some common examples of condensation polymers.
The reaction of 1,4-phenylenediamine (para-phenylenediamine) and terephthaloyl chloride to form aramid
Difference between addition polymerization and condensation polymerization
Nature of the monomer
Addition polymerization: Monomer must have at least one double or triple bond.
Condensation polymerization : Monomer must have at least two similar or different functional groups.
Type of polymer formation
Addition Polymerization : The addition of monomer results in a polymer.
Condensation polymerization : Monomers condense to form a polymer.
Byproducts
Addition polymerisation: This polymerisation does not produce any by-products.
Condensation polymerization : This polymerization creates by-products such as water, HCl, CH 3 OH, NH 3 , etc.
Molecular weight
Addition Polymerization: The molecular weight of the resulting polymer is an integral multiple of the molecular weight of the monomer.
Condensation Polymerization: The molecular weight of the resulting polymer is not an integral multiple of the molecular weight of the monomer.
Size of the resulting polymers
Addition polymerization: The reaction immediately leads to high molecular weight polymers.
Condensation polymerization : the molecular weight of the polymer increases steadily with the reaction.
reaction time
Addition polymerization: A longer reaction time leads to higher yields, but has little effect on the molecular weight of the polymer.
Condensation Polymerization : Longer reaction times are crucial in order to obtain a higher molecular weight of polymers.
Nature of the polymers produced
Addition polymerization: In addition polymerization, thermoplastics are produced .
Condensation polymerisation: During condensation polymerisation, thermosets are produced .
Polymer chain
Addition polymerization: The addition polymerization leads to homo-chain polymers .
Condensation polymerization : Condensation polymerization leads to hetero-chain polymers .
Examples of common polymers
Addition polymerization: polyethylene, PVC, etc.
Condensation Polymerization: Bakelite, Nylon, Polyester, etc.
Catalysts
Addition polymerization: Free radical initiators, Lewis acids or bases are catalysts in this process.
Condensation Polymerization: Mineral acids and bases are catalysts in this process.
References:
“PVC-Polymerisation-2D” (Public Domain) via Commons Wikimedia
