- Polymers are substances containing a large number of structural units joined by the same type of linkage. These substances often form into a chain-like structure.
- Polymers in the natural world have been around since the beginning of time. Starch, cellulose, and rubber all possess polymeric properties.
- Proteins are natural polymers made up of amino acids, and nucleic acids (DNA and RNA) are polymers of nucleotides complex molecules composed of nitrogen-containing bases, sugars and phosphoric acid.
Polymerization is the method of creating synthetic polymers by combining smaller molecules, called monomers, into a chain held together by covalent bonds.
Synthesis of polymer is done by following processes:
I. Free radical Polymerization
It is most widely practiced chain polymerization type. Basic steps involved here are
i) Initiation (Free radical is added to monomer)
ii) Propagation ( Monomer linkage from tail to tail)
iii) Termination (By coupling two growing chain or by extracting Hydrogen atom from one growing chain)
II. Bulk Polymerization(Solution Polymerization)
Initially the solution only contains Monomers and a initiator, as the heat is applied externally, the reaction starts and generates more heat but can be control the temperature, and such process makes the monomer to polymer.
III. Interfacial Polymerization
Here the reactants defuse to interface and react to form polymer. By this process we can make high molecular weight polymer. By just removal of film we can refresh the monomer. It is diffusion controlled reaction but cannot be control kinetically.
IV. Emulsion Polymerization
Here amphiphilic monomers get arrange over water surface until saturation. These monomers get arranged in the form of a stable structure known as micelles in water, the initiator diffuse into this micelles to initiate reaction. Polymerization drives to increase in particle size.
V. Chemical vapour Deposition Polymerization
Monomers are added to system, the system is put under vacuum and argon is used here as carrier gas. Monomer sublimates and enter furnace, and pyrolysis leads to polymerization. The chilling chamber draws the reaction towards the surface where they continue to polymerize.