Types Of Polymerisation Reactions

Polyisoprene is the natural rubber which is the polymer of isoprene.

Natural Rubber is a polymer of Isoprene which means it is formed by repeating isoprene units derived from conjugated diene monomers. It is from the monomer isoprene (2-methyl-1,3-butadiene). The chemical structure of isoprene can be represented as CH₂=C(CH₃)—CH=CH₂.

Hence, the correct answer is option D.

Polyisoprene is the natural rubber which is the polymer of isoprene.

Natural Rubber is a polymer of Isoprene which means it is formed by repeating isoprene units derived from conjugated diene monomers. It is from the monomer isoprene (2-methyl-1,3-butadiene). The chemical structure of isoprene can be represented as CH₂=C(CH₃)—CH=CH₂.

Hence, the correct answer is option D.

The correct answer is:

Option 4: All cis-configuration

Explanation:

Natural rubber is primarily made of polyisoprene, which is a polymer composed of repeating units of isoprene (C₅H₈). The structure of natural rubber has all cis-configuration at the double bonds in the polymer chain. This means that the substituents (methyl groups) are on the same side of the polymer backbone, giving the polymer a flexible, coiled structure.

All cis-configuration: This refers to all of the isoprene units in natural rubber having the same configuration, where the two methyl groups (CH₃) are on the same side of the polymer backbone.

Cis-trans isomerism: While there is also trans-configuration, which has the methyl groups on opposite sides, natural rubber specifically has all cis-configuration in its polymer chain, which contributes to its flexibility and elasticity.

To determine which statement regarding polymers is not correct, let's analyze each option:

• Elastomers have polymer chains held together by weak intermolecular forces. This is true. Elastomers are a type of polymer that can be stretched and they typically return to their original shape when the stretching force is removed. This behavior is due to the weak intermolecular forces between polymer chains, allowing them to stretch and contract easily.
• Fibers possess high tensile strength. This is true. Fibers are polymer chains that are aligned and packed closely together, which provides them with high tensile strength. They are used in applications like textiles where this property is essential.
• Thermoplastic polymers are capable of repeatedly softening and hardening on heating and cooling respectively. This is true. Thermoplastics can be heated to soften, molded into a shape, and cooled to harden. This process can be repeated multiple times without significantly degrading the material's properties.
• Thermosetting polymers are reusable. This statement is incorrect. Thermosetting polymers undergo a curing process that creates cross-links between polymer chains, resulting in a rigid structure that does not melt upon reheating. Once set, they cannot be remolded or reused, which differentiates them from thermoplastics.

Thus, the incorrect statement regarding polymers is: Thermosetting polymers are reusable.