What are the monomer units of Buna-S rubber?

The correct answer is option 1. Styrene + 1,3-butadiene.

Buna-S is a type of synthetic rubber, also known as styrene-butadiene rubber (SBR). It is a copolymer composed of two monomer units: styrene and 1,3-butadiene.

Here is how the polymerization occurs:

Styrene (C₈H₈): This monomer unit contributes to the rigidity and stability of the polymer chains due to its aromatic structure.

1,3-Butadiene (CH₂=CH-CH=CH₂): This monomer unit provides flexibility and resilience to the polymer chains due to its unsaturated structure and ability to undergo polymerization.

During the polymerization process, styrene and 1,3-butadiene monomers undergo addition polymerization, forming a long chain of repeating units that alternate between styrene and butadiene. This results in the formation of the Buna-S rubber, which exhibits a balance of properties such as good abrasion resistance, elasticity, and chemical resistance.

The monomer units of Buna-S rubber are styrene and 1,3-butadiene. Therefore, the correct answer is Styrene + 1,3-butadiene