Buna-S, a synthetic polymer also termed styrene-butadiene rubber, is manufactured via the copolymerization of butadiene (CH₂=CH-CH=CH₂) and styrene (C₆H₅-CH=CH₂), typically in a 3:1 ratio of butadiene to styrene. Its widespread application in automotive tires stems from its robust durability and wear resistance.
Alternative considerations:
- Isoprene constitutes the primary monomer in natural rubber.
- Phenol and vinyl chloride are not components of Buna-S.
Final Answer:
\[
\boxed{\text{Styrene and butadiene}}
\]