Types Of Polymerisation
When some of bifunctional molecules connect in a chain structure, the reaction is termed as addition polymerisation. However, these polymerizations do not take place on its but has to be initiated, propagated and after that terminated. Presence of split H2O2 or 2HO usually initiates the reaction. Hydrogen peroxide is heated to split in two free radicals 2HO that initiates polymerisation. The energy of the chain polymer is lower than that of the independent monomers such form the chain and thus the chain grows in length fast after initiation. By addition of trace impurity the reaction is terminated. The reaction termination may airse because of two ends of joining of the chain or because of supply of exhaustion of the monomers also. Ethylene or C2H4 polymerising in polyethylene and vinylchloride or C2H3Cl polymerising in polyvinyl chloride are the illustrations of addition polymers.
The improvements in polymer technology have led to the knwoing that monomers of two various types can join in a single chain in co-polymerisation. For illustration, monomers of vinylaecetate and vinylchloride form a chain of copolymers as demonstrates in figure of Co-polymerisation of Vinylchloride or C2H3Cl and Vinylacetate or OCOCH3. Vinylacetate molecule along with dual bond between oxygen and carbon is also demonstrates in same figure. This double bond opens into two bonds to join along with another opened bond of carbon of vinylchloride.
Figure: Co-polymerisation of Vinylchloride or C2H3Cl and Vinylacetate or OCOCH3
A copolymer is greatly like a solid solution in crystalline materials because its properties are very much dissimilar than those of constituents.A third type of polymerisation reaction happens when a second non-polymerisation molecule is generated as a byproduct. This reaction is termed as condensation polymerization. The genearl byproducts of condensation polymerisation are water, CH3OH or HCl. In a characteristic reaction of polycondensation among hexamethylenediamine and adipic acid long chain nylon molecules are produced along with water as a byproduct.