3. On the basis of chemical reactions :
Depending upon the basis on which monomers undergo chemical reactions to form polymers, polymers can be further subdivided.
a. Polycondensation Reaction : It is a stepwise process in which the monomers react by eliminating small molecules like H2O, NH3, CH2O and NaCl in a repetitive manner . Indefinite growth of the polymer occurs at both ends. The condensation reaction terminates when one of the reacting molecules is completely consumed in the reaction. In general, bifunctional monomers with different functional groups undergo such reactions. One common example of a condensation reaction is the esterification reaction. Benzoic acid reacts with ethanol undergoing condensation reaction to give Ethyl benzoate, expelling one molecule of water (H2O). The polymer formed after the reaction (in this case, ethyl benzoate) is called the condensation polymer.
