Synthetic polymers topic of organic chemistry.
According to staudinger 1920, those substances whose molecular weight is more than 10,000 are called as 'Macromolecules'.
Thus macromolecules are those big molecules which are obtained by joining together of small, structural units(either same or different) again and again by covalent bond and their sizes are like colloidal particles i.e. (10 A to 10,A and their molecular weight are 10,000 or more.
Since their sizes are similar to colloidal particles therefore those are also called as 'molecular colloid'.
In macromolecule either molecules or atoms could be in the form of structural units therefore macromolecules are of 2 types-
*Macromolecule in which structural units is 'molecules'. For example - polyethylene
* Macromolecules in which structural units is 'atoms'. For example - diamond, quartz etc.
Polymer definition -
" Simple and low molecular weight molecules having same or different structure when combine together form polymer and this process is called 'polymerization '.
Number of monomer units present in any polymer is called it's 'degree of polymerization '. (n).
That complete unit which repeats in a polymer again and again is called 'repeat unit'.
Length of any polymer series depends up on the value of 'n'. Those polymers in which value of n is less i.e. (10 to 100) are called 'oligomer' and those polymer in which the value of n is more than 100 are called as 'high polymer'
Classification of polymers -
1. Classification based upon nature of the 'repeating unit'.
2. Classification based on the basis of 'structure'.
3. Classification based on the basis of 'synthesis'.
4. Classification based on the basis of 'series'
5. Classification based on the basis of 'molecular forces'.
6. Classification based on the basis of 'source'.
1. Classification based on the basis of 'repeating unit'.
#homopolymers - in which repeating unit is derived from only 1 type of monomer units.
#copolymers - polymers whose repeating units are derived from 2 or more than 2 types of monomer units are called copolymer or heteroplymer.
2. Classification based on the basis of 'source'.
# Natural polymer- those polymers which are found in nature or are obtained from natural products are called as natural polymers. For example - cellulose.
# Synthetic polymers - those polymers which are synthesized from artificial methods are called as Synthetic polymers. For example - artificial rubber.
3. Classification based on the basis of 'structure'.
# linear polymers - in which polymer monomer units join together to form a straight chain.
# branched polymers- in these polymers there is a main branch and some irregular branches are joined to it.
# 3D cross linked polymers- in these polymers long chains of monomers unit are joined together to form cross linkers.
4. Classification based on the basis of 'synthesis'.
#addition polymer - when onee or more than 1 type of compounds are join together to form macromolecules then the process is called as addition polymerization
#condensation polymer- two or more than 2 type of molecules of monomer when condense together then condensation polymer is formed.
5. Classification based on the basis of 'polymer chain'.
#chain growth polymer - when molecular units form polymer by increasing the chain via. addition polymerization process, then polymer obtained is called chain growth polymer.
# step growth polymer - this type of polymers are prepared by the repetition of product obtained by the condensation of 2 independent monomer units.
6. Classification based on the basis of ' molecular forces'.
# thermoplastic polymer- polymers which on heating become soft and can be converted into any shape on cooling are called thermoplastic polymer.
# thermosetting polymer- polymers which on heating convert into hard substances by chemical changes are called thermosetting polymer.
# elastomers- polymers which show elasticity like rubber are called elastomers- which means on pulling quickly stretches times to it's length and on removing the stress the again regain their initial length are called as elastomers-.
# fibres - those polymers in which intermolecular forces are present between 2 series are called fibres.