• Biodegradable polymers are a specific type of polymer that breaks down after its intended purpose to result in natural byproducts such as gases (CO₂, N₂), water, biomass, and inorganic salts.
• These polymers are found both naturally and synthetically made, and largely consist of ester, amide, and ether functional groups.
• Their properties and breakdown mechanism are determined by their exact structure.
• These polymers are often synthesized by condensation reactions, ring opening polymerization, and metal catalysts.
• Aliphatic polyesters are one of the important classes of biodegradable polymers.

Examples:

1. Poly β – hydroxylbutyrate – co – β – hydroxyl valerate (PHBV): It is obtained by the copolymerization of 3 – hydroxybutanoic acid and 3 – hydroxypentanoic acid.

$$\underset{3\,-\,hydroxy\,bu\tan oic\,acid}{\mathop{C{{H}_{3}}-\underset{OH}{\mathop{\underset{|}{\mathop{C}}\,}}\,H-C{{H}_{2}}-COOH}}\,\,+\,\underset{3\,-\,hydroxy\,pen\tan oic\,acid}{\mathop{C{{H}_{3}}-C{{H}_{2}}-\underset{OH}{\mathop{\underset{|}{\mathop{C}}\,}}\,H-C{{H}_{2}}-COOH}}\,\xrightarrow{{}}\underset{PHBV}{\mathop{{{\left[ -O-H\overset{C{{H}_{3}}}{\mathop{\overset{|}{\mathop{C}}\,}}\,-C{{H}_{2}}\overset{O}{\mathop{\overset{||}{\mathop{C}}\,}}\,-O-\overset{C{{H}_{2}}C{{H}_{3}}}{\mathop{\overset{|}{\mathop{CH}}\,}}\,-C{{H}_{2}}\overset{O}{\mathop{\overset{||}{\mathop{C}}\,}}\,- \right]}_{n}}}}\,$$.

Uses: It is used in speciality packaging, orthopaedic devices and in controlled release of drugs.

PHBV undergoes bacterial degradation in the environment.

2. Nylon 2 – Nylon 6: It is a polyamide copolymer of glycine (H₂N – CH₂ – COOH) and amino caproic acid (H₂N (CH₂)₅ COOH) and is biodegradable.