2. On the basis of physical structure :

a. Linear polymers : These polymers have a linear structure. Only bifunctional monomers can form linear polymers.

They are generally thermoplastic polymers, and except for very high molecular weight materials, they are soluble in solvents.

 

b. Cross –linked polymers : These polymers have a 3-D network structure. Only bi-functional and tri-functional monomers can form cross-linked polymers. Elastomeric properties are generally endowed in polymers have cross-linkage across the linear chains.

 

• Thermosetting polymers having high thermal resistance and mechanical strength may be formed if the cross-linking among the monomer groups is extensive.

 

c. Branched –chain polymer : When there is no cross-linking in a polymer molecule , yet, branches arise from the parent polymer chain , then the polymer formed is called a branched – chain polymer.

A small amount of trifunctional impurities in a bifunctional monomer may cause branching. Branching may create several physical properties in a polymer such as decrease of solubility in solvents, rise in the softening point and also the reduction in thermoplastic properties.