Condensation polymer
6247
224357256
2008-07-08T14:25:40Z
SmackBot
433328
Date the maintenance tags or general fixes
{{Unreferenced|date=July 2008}}
'''Condensation polymers''' are any class of [[polymer]]s formed through a [[condensation reaction]], releasing a small molecule by-product such as water or methanol, as opposed to [[addition polymer]]s which involve the reaction of [[unsaturated monomer]]s. Types of condensation polymers include [[polyamide]]s, [[polyacetal]]s and [[polyester]]s.
Condensation polymerization, a form of [[step-growth polymerization]], is a process by which two molecules join together, with the loss of a small molecule which is often water. The type of end product resulting from a condensation polymerization is dependent on the number of functional end groups of the monomer which can react.
Monomers with only one reactive group terminate a growing chain, and thus give end products with a lower molecular weight. Linear polymers are created using monomers with two reactive end groups and monomers with more than two end groups give three dimensional polymers which are crosslinked.
[[Cross-linking]] often involves joining monomers with an -OH (hydroxyl) group and a freely ionized -H on either end (such as a hydrogen from the -NH<sub>2</sub> in [[nylon]] or [[proteins]]). Normally, two or more different monomers are used in the reaction. The bonds between the hydroxyl group, the hydrogen atom and their respective atoms break forming water from the hydroxyl and hydrogen, and the polymer.
[[Polyester]] is created through [[ester]] linkages between monomers, which involve the functional groups [[carboxyl]] and [[hydroxyl]] (an organic acid and an alcohol monomer).
[[Nylon]] is another common condensation polymer. It can be manufactured by reacting [[amine|di-amines]] with carboxyl derivatives. In this example the derivative is a [[carboxylic acid|di-carboxylic acid]], but [[acyl chloride|di-acyl chlorides]] are also used. Another approach used is the reaction of di-functional monomers, with one amine and one carboxylic acid group on the same molecule:
:[[Image:Condensation polymerization diacid diamine.svg|thumb|left|400px|General chemical structure of one type of condensation polymer]]{{clear}}
The carboxylic acids and amines link to form [[peptide bond]]s, also known as [[amide]] groups. [[Protein]]s are condensation polymers made from [[amino acid]] monomers. Carbohydrates are also condensation polymers made from sugar monomers such as glucose and galactose.
Condensation polymerization is occasionally used to form simple hydrocarbons. This method, however, is expensive and inefficient, so the [[addition polymer]] of ethene (polyethylene) is generally used.
Condensation polymers, unlike [[addition polymer]]s may be biodegradable. The peptide or ester bonds between monomers can be hydrolysed by acid catalysts or bacterial [[enzyme]]s breaking the polymer chain into smaller pieces.
The most commonly known condensation polymers are proteins, fabrics such as nylon, [[silk]], or [[polyester]].
==See also==
*[[Biopolymer]]
*[[Polyester]]
*[[Polyamide]]
[[Category:Polymer chemistry]]
[[pl:Polikondensaty]]