What is Condensation Polymerization?
Condensation polymerization is a form of step-growth polymerization where molecules combine, losing small molecules as by-products such as water or methanol. It produces linear polymers from bifunctional monomers. i.e., compounds with two reactive end groups. The polymerization happens between larger structural units and monomers. The condensation growth steps are expressed by:
A common example of condensation polymerization is the esterification of carboxylic acids with alcohols. The most well-known condensation polymers are polypeptide chains of proteins, polyamides, cellulose, starch, bakelite, kevlar, epoxies, polycarbonates, polyurethanes, and polyacetal.
If both moieties are difunctional, the condensation product will become a linear polymer. If the moieties are tri-or tetra functional, the result will be a crosslinked polymer, aka a three-dimensional network. Adding monomers with a single reactive group will break off a growing chain, decreasing the average molecular weight. That makes the average molecular weight and the crosslink density completely dependent on the interconnectedness of each monomer active in the conversation polymerization and its concentration in the mixture.
Characteristics of Condensation Polymerization –
Let’s take a look at some important attributes of condensation polymerization:
- Smaller molecules typically join to form larger molecules.
- The molecules should be comprised of one or two functional groups – ex: alcohols and carboxylic acids.
- The reaction happens between two similar or different functional groups or monomers. It can occur between a dimer and oligomer or one monomer and one dimer or between or chain or another chain of polymers.
- Properties of both the molecules and functional groups must be taken into consideration.
- The final condensation polymer is a linear polymer when both the functional groups are difunctional.
Interesting Read – What is Anionic Polymerization? An In-Depth Analysis
Condensation Polymerization Examples –
One of the two most important classes of condensation polymers is polyamides. They emerge from the reaction between carboxylic acid and amine. When amino-carboxylic acids are made, it results in the co-formation of water. It is expressed as follows:
n H2N-X-CO2H → [HN-X-C(O)]n + (n-1) H2O
However, when made from diamines and dicarboxylic acids. A great example is the production of Nylon 66. the polymerization produces two molecules of water per repeat unit. The expression is as follows:
n H2N-X-NH2 + n HO2C-Y-CO2H → [HN-X-NHC(O)-Y-C(O)]n + (2n-1) H2O
The second important class of condensation polymers is polyesters. They emerge from the reaction of carboxylic acid and alcohol. A prime example is polyethyleneterephthalate:
n HO-X-OH + n HO2C-Y-CO2H → [O-X-O2C-Y-C(O)]n + (2n-1) H2O
Difference Between Addition And Condensation Polymerization –
The main difference between the additional and condensation polymerization is that in addition to polymerization, the polymers are created by adding monomers with no by-products; on the other hand, in condensation, polymerization reacts with each other to create larger structural units while releasing byproducts like water and methanol.
|Monomer always have a double or triple bond||
Monomers always have similar or different functional groups
|The addition of monomers forms polymers||
The condensation of monomers forms polymers
|Releases no by-products||
By-products such as ammonia, water, and methanol are released.
|Lewis acids or bases and radical initiators act as catalysts||The most common catalysts are acids, bases, cyanide ions, and complex metal ions.|
|The molecular weight of the resultant’s polymer is a multiple of the monomer’s molecular weight.||
The molecular weight of the resultant polymer is not a multiple of the monomer’s molecular weight.
|Common examples – PVC, polyethylene, PTFE||
Common examples – bakelite, starch, and polyacetal
Engaging Read – When Was Plastic Invented? | The History of Plastics.
1. What is the formula for condensation?
Ans. Vaporization and condensation of any substance have exact opposite processes. The numerical value of the molar heat of vaporization is the same as the numerical value of the molar heat of condensation:
2. What’s another name for condensation reaction?
3. Does condensation polymerization require heat?
Ans. In condensation polymerization, every step gets along with forming a molecule of some simple compound, often water. So, yes, condensation polymerization does require heat from an external source.
4. What is the defining characteristic of a condensation reaction?
Ans. The main characteristic of condensation polymerization is the combination of is combining two molecules to make a complex molecule. It’s called loss of water or condensation. Two molecules always involved in the reaction are water or ammonia.
5. Which polymer of polyamide type is prepared by self-condensation reaction?
Ans. Nylon 66 is produced by the condensation reaction of hexamethylenediamine and adipic acid. The two comonomers are first reacted to form a salt.
6. What are the three stages of polymerization?
Ans. The three stages of polymerization are (1) initiation, (2) propagation, and (3) termination.
Suggested Read –
- How is Plastic made? A Simple and Detailed Explanation.
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- What is a Parting Line? | Parting Line in Injection Molding | Importance of Parting Line
Final Thoughts –
That was all I had to say about the condensation polymerization reaction. The condensation polymers create more biodegradable materials than addition polymerization.
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Have a fantastic day.