Question

The biodegradable polymer among the following polymer is

• A. Polylactic acid
• B. Polybutylene terephthalate
• C. Polystyrene
• D. Polypropylene

Hint:

PLA is widely used in biodegradable packaging and medical implants.

Answer 1

The Correct Option is A

Step 1: Understanding biodegradable polymers.
Biodegradable polymers are polymers that can be broken down into simpler substances by microorganisms such as bacteria and fungi under natural environmental conditions.
Step 2: Nature of given polymers.
Polylactic acid (PLA) is derived from renewable resources like corn starch and undergoes biodegradation through hydrolysis and microbial action. Other polymers listed are conventional synthetic polymers that resist biodegradation.
Step 3: Analysis of options.
(A) Polylactic acid: Correct — It is a biodegradable and bio-based polymer.
(B) Polybutylene terephthalate: A synthetic polyester, not biodegradable.
(C) Polystyrene: Highly resistant to biodegradation.
(D) Polypropylene: Non-biodegradable polyolefin.
Step 4: Conclusion.
Polylactic acid is the biodegradable polymer among the given options, hence option (A) is correct.

Answer 2

Biodegradability in polymers usually comes down to whether the backbone contains bonds that microorganisms and water (via hydrolysis) can actually break. Let's check each polymer's backbone chemistry for that vulnerability.

1. Polylactic acid: Built from lactic acid units joined by ester linkages, and lactic acid itself is a naturally occurring metabolite. The ester bonds in PLA are readily hydrolyzed by water and further broken down by microbial enzymes into lactic acid, which is then consumed by microorganisms - a complete, well-documented biodegradation pathway.
2. Polybutylene terephthalate: Also contains ester linkages, but they are flanked by rigid aromatic terephthalate rings that resist water penetration and enzymatic attack, making its ester bonds far more hydrolytically stable in practice; it behaves as an essentially non-biodegradable engineering polyester.
3. Polystyrene: Has a fully carbon-carbon backbone with bulky phenyl side groups and no hydrolyzable linkage anywhere in the chain, so there's no chemical "handle" for microbes or water to attack - it persists in the environment for a very long time.
4. Polypropylene: Also a purely carbon-carbon backbone polyolefin with no ester, amide, or other cleavable linkage, making it similarly resistant to microbial or hydrolytic breakdown.

Only PLA's aliphatic ester backbone, derived from a metabolizable natural acid, provides an actual chemical route for biodegradation.

Therefore, the correct answer is Polylactic acid.