Question

Which of the polymerization techniques is used for synthesis of high molecular weight polymer?

• A. Emulsion
• B. Suspension
• C. Solution
• D. Dispersion

Hint:

Emulsion polymerization is widely used in the rubber and latex industry.

Answer 1

The Correct Option is A

Step 1: Understanding high molecular weight polymers.
High molecular weight polymers require rapid chain growth with minimal chain termination. Such conditions help in achieving long polymer chains with greater molecular mass.
Step 2: Role of polymerization techniques.
In emulsion polymerization, polymerization occurs in micelles where monomer concentration is high and termination reactions are minimized. This favors the formation of polymers with very high molecular weight.
Step 3: Analysis of options.
(A) Emulsion: Correct — It produces polymers with high molecular weight due to controlled radical concentration.
(B) Suspension: Produces moderate molecular weight polymers.
(C) Solution: Molecular weight is limited due to chain transfer to solvent.
(D) Dispersion: Not commonly used for very high molecular weight polymers.
Step 4: Conclusion.
Emulsion polymerization is preferred for synthesizing high molecular weight polymers, making option (A) correct.

Answer 2

This question asks which polymerization technique gives the highest molecular weight product. Instead of recalling the mechanism, let's judge each technique by where the reaction actually happens and how crowded that reaction site is with growing radicals.

1. Emulsion: Polymerization is compartmentalized inside thousands of tiny micelles, each hosting on average less than one growing radical at a time. Because two radicals rarely meet inside the same micelle, termination by radical-radical collision is suppressed even though the overall rate of polymerization stays high. Long-lived chains keep growing for longer, so the molecular weight builds up to very high values.
2. Suspension: Here the monomer is dispersed as large droplets (essentially mini bulk-polymerization reactors) and the kinetics inside each droplet resemble bulk polymerization. Radical concentration inside a droplet is much higher than inside a micelle, so termination is more frequent and the molecular weight stays moderate.
3. Solution: The monomer is dissolved along with initiator in a solvent, and growing radicals can transfer their activity to solvent molecules (chain transfer to solvent). This caps the chain length early, keeping the molecular weight low to moderate.
4. Dispersion: The polymer forms as a precipitate/particle in a medium in which the monomer is soluble but the polymer is not; particle nucleation and growth here do not offer the same isolation of radicals as micellar emulsion systems, so molecular weight build-up is not as pronounced.

Comparing the four, only the emulsion process physically isolates growing chains from each other well enough to let them grow to very high molecular weight while still polymerizing fast.

Therefore, the correct answer is Emulsion.