Revision on Inorganic chemistry – Polymers

Types of Polymers

Natural polymers – Substances of natural origin, i.e., found mainly in plants and animals. e.g., silk,enzymes, natural rubber, haemoglobin, starch, cellulose, proteins etc.
Synthetic polymers – Prepared in laboratory. Completely man-made polymers. e.g., teflon, dacron, synthetic rubber, nylon- 6,6, etc.
Semi-synthetic polymers – Derived by using natural polymers. e.g., vulcanised rubber, nitrocellulose, cellulose xanthate, etc.

Structure of Polymers

Linear polymers – Monomers are joined together to form straight chains. e.g., PVC, polystyrene, nylons, etc.
Branched chain polymers – Monomers are joined to form irregularly packed polymers having branched chains. e.g., amylopectin, glycogen,starch etc.
Cross-linked polymers – Initially formed linear polymer chains are joined together to form a three dimensional network structure. e.g., bakelite, melamine formaldehyde resin (melmac), etc.

Molecular Forces


Elastomers – Very weak intermolecular forces and possess elastic characters. e.g., natural rubber, buna-S, etc.
Fibres – Quite strong intermolecular forces like hydrogen bonds. Used for making fibres. e.g., nylon-6,6, polyacrylonitrile (orlon), etc.
Thermoplastics – Neither very strong nor very weak intermolecular forces. Do not have any cross-links between chains. Can be easily moulded on heating. e.g., polypropylene, polystyrene, etc.
Thermosetting plastics – Extensive cross-links are formed between polymeric chains on heating. Undergo permanent change. e.g., bakelite, resin, etc

Synthesis

Addition polymers – Formed by addition of monomers without elimination of byproducts e.g., PVC, polythene, etc.
Condensation polymers – Formed by combination of monomers with elimination of simple molecules like water, alcohol, ammonia, etc. e.g., dacron, nylon-6,6, etc.



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