Which is a characteristic of condensation polymerization?

In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction (i.e. a small molecule, such as water or methanol, is produced as a byproduct). Condensation polymers are formed by polycondensation, when the polymer is formed by condensation reactions between species of all degrees of polymerization, or by condensative chain polymerization, when the polymer is formed by sequential addition of monomers to an active site in a chain reaction. The main alternative forms of polymerization are chain polymerization and polyaddition, both of which give addition polymers.

Table of Contents Show

Characteristics of Condensation Polymerization –
Condensation Polymerization Examples –
Difference Between Addition And Condensation Polymerization –
FAQs –

Polyethylene terephthalate (PET) is a common condensation polymer.

IUPAC definition

Polycondensation A polymerization in which the growth of polymer chains proceeds by condensation reactions between molecules of all degrees of polymerization. Notes: 1. The growth steps are expressed by: Px+Py→Px+y+L {x}∈{1,2,…∞};{y}∈{1,2,…∞}
where Px and Py denote chains of degrees of polymerization x and y, respectively, and L a low-molar-mass by-product. 2. The earlier term 'polycondensation' was synonymous with 'condensation polymerization'. The current definitions of polycondensation and condensative chain polymerization were both embraced by the earlier term 'polycondensation'.[1]

Condensation polymerization is a form of step-growth polymerization. Linear polymers are produced from bifunctional monomers, i.e. compounds with two reactive end-groups. Common condensation polymers include polyamides, polyacetals, and proteins.[2][3]

One important class of condensation polymers are polyamides.[4] They arise from the reaction of carboxylic acid and an amine. Examples include nylons and proteins. When prepared from amino-carboxylic acids, e.g. amino acids, the stoichiometry of the polymerization includes co-formation of water:

n H2N-X-CO2H → [HN-X-C(O)]n + (n-1) H2O

When prepared from diamines and dicarboxylic acids, e.g. the production of nylon 66, the polymerization produces two molecules of water per repeat unit:

n H2N-X-NH2 + n HO2C-Y-CO2H → [HN-X-NHC(O)-Y-C(O)]n + (2n-1) H2O

General chemical structure of one type of condensation polymer

One important class of condensation polymers are polyesters.[5] They arise from the reaction of carboxylic acid and an alcohol. Examples include polyesters, e.g. polyethyleneterephthalate:

n HO-X-OH + n HO2C-Y-CO2H → [O-X-O2C-Y-C(O)]n + (2n-1) H2O

Structure of poly-(R)-3-hydroxybutyrate (P3HB), a naturally-occurring polymer.

Condensation polymers tend to be more biodegradable than addition polymers. The peptide or ester bonds between monomers can be hydrolysed, especially in the presence of catalysts or bacterial enzymes.[6]

Biopolymer
Epoxy resins
Polyamide
Polyester

^ Jenkins, A. D.; Kratochvíl, P.; Stepto, R. F. T.; Suter, U. W. (1996-01-01). "Glossary of basic terms in polymer science (IUPAC Recommendations 1996)". Pure and Applied Chemistry. 68 (12): 2287–2311. doi:10.1351/pac199668122287. ISSN 0033-4545. S2CID 98774337.
^ Introduction to Polymers 1987 R.J. Young Chapman & Hall ISBN 0-412-22170-5
^ D. Margerison, G. C. East, J. E. Spice (1967). An Introduction to Polymer Chemistry. Pergamon Press. ISBN 978-0-08-011891-8.{{cite book}}: CS1 maint: uses authors parameter (link)
^ B. Herzog, M. I. Kohan, S. A. Mestemacher, R. U. Pagilagan, K. Redmond (2013). "Polyamides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_179.pub3. ISBN 978-3527306732. S2CID 241272519.{{cite encyclopedia}}: CS1 maint: uses authors parameter (link)
^ Horst Köpnick, Manfred Schmidt, Wilhelm Brügging, Jörn Rüter, Walter Kaminsky (2002). "Polyesters". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_227. ISBN 3527306730.{{cite encyclopedia}}: CS1 maint: uses authors parameter (link)
^ Wei, Ren; Zimmermann, Wolfgang (November 2017). "Microbial enzymes for the recycling of recalcitrant petroleum‐based plastics: how far are we?". Microbial Biotechnology. 10 (6): 1308–1322. doi:10.1111/1751-7915.12710. PMC 5658625. PMID 28371373.

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Polymers (and condensation polymers) - Virtual Text of Organic Chemistry, William Reusch

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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:

Px+Py→Px+y+L {x}∈{1,2,…∞};{y}∈{1,2,…∞}

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 –

Polyamides:

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

Polyesters:

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.

Addition Polymerization	Condensation Polymerization
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.

FAQs –

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:

ΔHvap=−ΔHcond.

2. What’s another name for condensation reaction?

Ans. Dehydration.

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 –

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.