 |
| Summary |
|
 Polymers - high molecular mass macro-sized molecules consisting of repeating units of monomers - may be synthetic or natural in origin. |
| |
|
Addition polymerization are usually performed on alkenes and their derivatives and proceed through chain growth mechanism involving radicals, cations and anions as intermediates. |
| |
|
When a mixture of monomers is polymerized, a copolymer containing multiple units of each monomer is formed. |
| |
|
Natural rubber is a linear polymer of isoprene and is vulcanized by heating with sulphur which forms bonds at alkene, or acyclic reaction sites of different chains establishing cross links. |
| |
|
Synthetic rubbers are usually obtained by copolymerization of alkene and 1,3-butadiene derivative. |
| |
|
Polythene, PVC, orlon, Teflon and many synthetic rubbers are formed by polymerization of appropriate alkenes through addition mode. |
| |
|
Condensation polymerization takes place in bi or poly functionalized monomers possessing -OH, -NH2, -COOH etc. groups with elimination of H2O, NH3 etc. and formation of linkages such as ester, amides etc. Even electrophilic aromatic substitution of phenols with formaldehyde forms polymers having C-C linkages. Each condensation step provides a bi or poly functionalized product and the polymerization progresses step by step. Nylons, Dacron and bakelite constitute some important condensation polymers. |
| |
|
Synthetic polymers due to their inertness to degrade have created environmental problems. Some biopolymers degrade enzymatically. Synthetic biodegradable polymers having functional groups such as ester, amide etc. are also potential for use as sutures, implants, drug release. PHBV, PLLA, Nylon-2-Nylon 6 etc. constitute some such materials. |
| |
