Question

What is a biodegradable polymer? Give an example of a biodegradable aliphatic polyester

Answer 1

Hint: As the name suggests, bio suggests use of living things such as microbes and degradable means getting decomposed. Thus, biodegradable polymer means polymers which get decomposed with the help of microorganisms.

Complete step by step answer:
Biodegradable polymers are the polymers which get degraded into simpler molecules like carbon dioxide, water, nitrogen, etc under aerobic or anaerobic environment by the action of microorganisms or enzymes. They decompose through enzymatic hydrolysis and oxidation processes. The decomposition reactions include hydrolysis reactions (either enzymatically induced or non–enzymatic reaction mechanism) leading to non-toxic smaller molecules which can either be metabolized or excreted out from the body. It is usually developed by polymeric materials like starch, lactic acid, cellulose and polyesters. In this category, aliphatic polyesters are the most commonly employed polymers. There is a need to generate alternative biodegradable water-soluble polymers in case of down-the-drain products like detergents or cosmetics which have gained an immense importance. An example of biodegradable polymers are: Poly β-hydroxybutyrate–co-β-hydroxy valerate (PHBV). It is formed by combining 3-hydroxy butanoic acid and 3-hydroxy pentanoic acid. Other examples include polyglycolic acid(PGA), Polyhydroxy butyrate (PHB), Polycaprolactone(pcl), Nylon-2-nylon-6.

Note:
On a molecular level, the process of formation of biodegradable polymers is majorly a two‐step process that can occur in soil, water, or human beings. The first step involves a fragmentation step, in which a high molar weight macromolecular chain breaks into oligomers possessing polar functional chain ends as well as monomers along-with the loss of certain polymer characteristics, like molar mass and strength. The second step involves mineralization of oligomers with polar chain ends as well as monomers by microorganisms resulting in the formation of carbon dioxide, water, methane, and biomass. These products vary depending upon the availability of oxygen.