polymers are the substances which are made up of repeating structural units which are derived from specific compounds known as monomers.
The polymers having molecular weight greater than 10000 composed of repeating units of small molecular weight species.ex-propylene,ethylene etc.
Polymerization is the process of conversion of monomers to polymers.There are two types of polymerization reaction.
- Step growth polymerization
- Chain polymerization
STEP GROWTH POLYMERIZATION
These type of polymerization reaction applies to the monomers containing functional group like:COOH,-COOR,-COOOC-,NH2,-CHO,epoxy etc.Molecular mass average and molar mass distribution for these type of reaction are
- Mw/Mn is approximately 2
BASIC REACTION :There are two type of reaction process in step growth polymerization
- Condensation:In these reaction there is loss of small molecules
- Addition:In these reaction there is no loss of small molecules
These type of reaction leads to formation of dimers,trimers,tetramers etc.There rates and mechanism are identical by reactions.As these are equilibrium reactions,high high molecular weight polymers chain are obtained if equilibrium are displaced to the formation of product.Some of the examples of step growth polymerization are polycaprolactam:Nylon-6,polyurethane:pellethaneTM,epoxy,polycarbonate etc.
These type of polymerization applies to monomer having double bonds or ring structures.In these process polymerization is very different from step growth and also monomers are bi functional in chain polymerization.The chain polymerization basically consists of 3 steps:
In these step first of all active centre that is (radical,cation,anion)is formed and the growth of thechain is
I -> J*(Anion,cation,radical)
In these step the growth of the polymer chain is done by successive addition of monomers to the active center at the end of the reaction.
In these step the growth is terminated either by transfer of the active center or by neutralization.
1-What are polymers?
2-What is high polymers?
3-What do you mean by polymerization and how many types of polymerization reactions are there
4-Explain step growth polymerization?
5-What are the different steps in chain reaction and explain all steps?