Question

What is the correct order of following in increasing order of their intermolecular forces?
A.Elastomers < Fibre < Plastic
B.Elastomers < Plastic < Fibre
C.Plastic < Elastomer < Fibre
D.Fibre < Elastomer < Plastic

Answer 1

Hint: The presence of strong intermolecular forces is one of the main factors which leads to unique physical properties of polymers. The polymers which have strongest intermolecular forces can undergo extensive cross linking in moulds and again become fusible. Whereas the one with the weakest intermolecular forces are natural rubber which has the property of elasticity.

Complete step-by-step answer:
We know that polymers are materials which are made of long repeating chains of monomeric molecules. They have unique properties depending on the types of monomeric molecules being bonded and the way they are bonded. We can define the force of attraction as the force which binds the molecules together to form the polymers. Hydrogen bonding is the strongest type of intermolecular force.
We can define these three types of polymers as:
1.Elastomers - These are the molecules which have weak intermolecular forces because they are elastic in nature. The best example to understand it is natural rubber. We can easily stretch a rubber due to its high elasticity. This high elasticity refers to the weak intermolecular force of attraction between the monomers of rubber.
2.Plastic – These are the plastic materials which can be softened and melted by heating or raising temperature, but they set again when cooled. They can easily be moulded into different shapes on melting. No ionic bonds or any such strong bond or intermolecular force of attraction is present in these types of polymers. For example, polyethylene, polypropylene, etc.
3.Fibre – These are the polymers which have the strongest intermolecular force of attraction between the chains formed by linking of monomers. They also have intermolecular hydrogen bonding which is strongest in nature. These solids are used to form threads as they have high tensile strength and high modulus of elasticity. Because of such strong forces, these are found in crystalline form. For example, polyvinyl chloride, phenol formaldehyde, etc.
Looking at the above points, we are now clear with the correct order which is Elastomers < Plastic < Fibre in increasing order of their intermolecular forces.
Hence, the correct option is (B).

Note: If the polymer is heated enough, it reaches the melting temperature and this process is reversible for thermoplastics. Intermolecular forces affect flexibility such that the stronger intermolecular forces hold the chains together more tightly and are therefore less able to move relative to each other.