Classification of polymers , Types and mechanism of polymerization: A Review

Abstract

Polymers are high molecular weight materials / macromolecules, composed of large number of low molecular weight species. The term polymer can be defined as a
macromolecule with high molecular mass arising due to the joining of a large number of simpler / smaller molecules (called monomers). The polymers are characterized by variable molecular weight (depending on the source or mode of synthesis or extraction), low specific gravity, better resistance to erosion, corrosion, insects or fungi etc. The advantageous aspect of polymeric materials over other materials is that they can be tailor-made i.e. polymers can be synthesized as per our property requirement or soft to rigid / tough, transparent to opaque, light to heavy, crystalline to amorphous materials can be synthesized. To cite an example, there are different types of polyethylene {(CH2-CH2)n} such as low density, medium density and high density polyethylene (abbreviated as LDPE, MDPE and HDPE). Polymers find applications as major class of materials such as plastics, fibres, rubbers, rexin (artificial leather) and explosives. Polymerization is the union of two or more simpler molecules (effected under the influence of heat, pressure, catalyst etc.), resulting in the formation of new macromolecule with the characteristic C-C linkages. The resultant macromolecule is called polymer and the original / parent simpler molecule is called monomer.