Which of the following is an example of polyester?

We need to identify which of the given options is an example of a polyester.

Option A: Butadiene-styrene copolymer

This is Styrene-Butadiene Rubber (SBR), which is a copolymer formed by addition polymerization of 1,3-butadiene and styrene. It is a synthetic rubber, not a polyester.

Option B: Melamine polymer

Melamine polymer (melamine-formaldehyde resin) is formed by condensation of melamine with formaldehyde. It is a thermosetting polymer with cross-linked structure, not a polyester.

Option C: Neoprene

Neoprene is polychloroprene, formed by addition polymerization of chloroprene (2-chloro-1,3-butadiene). It is a synthetic rubber, not a polyester.

Option D: Poly-$$\beta$$-hydroxybutyrate-co-$$\beta$$-hydroxyvalerate (PHBV)

PHBV is a copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid (3-hydroxypentanoic acid). These monomers contain both $$-OH$$ and $$-COOH$$ groups. They undergo condensation polymerization to form ester linkages ($$-COO-$$), making PHBV a polyester. It is also a biodegradable polymer used in packaging and medical applications.

The correct answer is Option D: Poly-$$\beta$$-hydroxybutyrate-co-$$\beta$$-hydroxyvalerate.