How are polymers classified on the basis of structures?

Explanation

Based on structure, polymers are classified as
(i) Linear polymers - They have long and straight chains. The various polymeric chains are stacked over one. another to give a well packed structure. Because of this close packing, they'have high melting points, high density and high tensil strength. eg: high density polythene (HDP), Polyvinyl chloride (PVC), nylon and polyester etc.
(ii) Branched chain polymers - The monomer units continue to produce linear chain with some branches:
Because of branches, these polymer molecules do not pack well. Hence branched chain polymers have lower melting points, densities and tensile strength as compared to linear polymers. eg. low density polythene (LDP), amylopectin, glycogen etc.
(iii) Cross linked or three dimensional network
polymers. These polymers are usually formed from bifunctional and tri - functional monomers and contain 'strong covalent bonds between various linear polymer chains, Because of the presence of cross links, these polymers are called cross linked polymers. They' are hard, rigid and brittle. 'cg', bakelite, urea-formaldehyde polymer, melamine - formaldehyde polymer etc.