Difference between Condensation and polymerization

Normally, addition polymerization means that two monomers react with  each other and no other small molecules are generaged. The best example  is polymerization of ethylene: the double bonds are broken and linked  with each other to form a long chain polymer. These are mostly radical  based polymerization, for those monomers with double bonds.

Condensation  polymerization, as a contrast, normally involves the generation of  small molecule products, like water. For example, ethylene glycol reacts  with terephathalate to form poly(ethylene terephathalate) polymer.  Meanwhile, water is generated. It looks like two molecules "condense"  with each other to form this polymer. These include polyester, polyamide  and polycarbonate.

However,  such division of polymerization is too simple. The ring-opening  polymerization, where ring compounds like lactone and lactam break their  rings and form a linear polymer, is hard to place into these two  category. It is a polyester. However, it is formed without the  generation of small molecule by-products. Thus, nowadays, it is more  widely used to say "step" polymerization instead of condensation  polymerization. This is more emphasis on the polymerization mechanism  rather than the chemical reactions.

To  answer your question, I think protein synthesis mainly belongs to  "condensation" polymerization (or step polymerization). But I can  understand why it is called "addition polymerization". It may because  the textbook means one amino acid adds to the protein backbone one per  time during the synthesis. This may looks like a "addtion" process.

So  to conclude, I think from the polymer chemist point of view, protein  synthesis, amide bond formation is clearly a "step" polymerization  process. But biochemist may have a different definition of "addition  polymerization".

 

According to Odian (in his textbook Principles of Polymerization, 4th Edition, page 6), the following is true:

“….polymer is classified as a condensation polymer if its synthesis involves theelimination of small molecules, or it contains functional groups as part of the polymer chain,or its repeating unit lacks certain atoms that are present in the (hypothetical) monomer towhich it can be degraded. If a polymer does not fulfill any of these requirements, it is classifiedas an addition polymer.”

So the classification of condensation vs. addition is judged simply by looking at the chemical structure of the polymer backbone, without regards to the actual mechanism.

The mechanistic differences come in when you consider a different pair of classes: step (similar to condensation) and chain (similar to addition) polymerization. The textbook treats those differences as well. It’s a difference of 1) step: pairwise reactions of chain ends (either can be the growing chain or a monomer), versus 2) chain: monomers add onto a growing chain at a reactive site, and the reactive site moves to the newly added monomer.

additional :- monomers join together to give a single product without loss of any molecule
ex :- ethene to polyethene

condensation :- monomers join together in which small is removed such as H2O,HCL
ex :- carboxylic acid + alcohol=RCOOR+HCL

1. In condensation polymerization, the reactivity of the functional groups gradually decreases as the degree of polymerization increases. This means that the polymerization gradually slows down as the molecular weight increases in spite of a large availability of monomers. Addition polymerization however, shows constant reactivity of the functional groups (i.e the free radical/anion/cation part) for any range of sizes of the polymer chains. So, technically, in the absence of a inhibiting agents, the polymers can keep growing at a constant rate as long as there are monomers being supplied.

2. Condensation polymers show PDI of around two, whereas the addition polymers can show a PDI of one as in the case of living polymerization (although PDI as high as 10-20 are said to be observed depending on the inhibition rates).

This means that addition polymers provide an opportunity for the controlled production of high precision macromolecules.

(1) Addition polymerisation is the reaction b/w monomers with multiple bond,where they join togather to form saturate polymers. in condensation polymerisation reaction functional group of to monomer react togather releasing a small molecule to form a polymer.
(2) Saturated monomers are participated incondensation reaction whereas for the addition polymerisation monomer should be an unsaturated molecule.
(3) Addition polymers are non-biodegrable and hard to recycle as compare to condensation polymer.

The product formed when the monomer units are repeately added to form long chains without the eliminiation of by product molecules(H20, ROH etc..) is called ADDITION POLYMERISATION.

Eg : polythene, orlon..etc

The product formed when the monomers react together with the elimination of by product molecules is called CONDENSATION POLYMERISATION.

Eg : dacron;bakelite;nylon 6,6 etc…

In the field of polymer chemistry addition polymerization is a way of making plastics rather than resins. Plastics are usually linear long chained molecules having a distribution of  chain lengths within the given plastic material. Plastics are also flexible materials  or  can be made flexible through the use of additives because they have a linear structure at the molecular level.  
 In contrast resins are usually made  by condensation reactions. Resins are essentially one big molecule so very stiff.
 Rubbers are amorphous thermoplastics polymers above their glass transition temperatures.

Protein synthesis belongs to condenization part of the polymerization methods. Simply, water is extracted (condensed) during the reaction and condensed molecule (water, HCl etc) must be removed by vacuum.