Condensation vs. addition polymers:\nWhich of the following is NOT a condensation (step-growth) polymer?

Introduction / Context:
Polymerisation mechanisms determine processing and properties. Condensation (step-growth) polymers arise from reactions between functional groups with small-molecule elimination; addition (chain-growth) polymers form by opening double bonds without eliminating small molecules. Accurately classifying common materials is a frequent exam task.

Given Data / Assumptions:

• Bakelite: phenol–formaldehyde condensation network.
• Melamine polymers: melamine–formaldehyde condensation networks.
• PMMA: addition polymer of methyl methacrylate.
• Polycarbonate: condensation of bisphenol A and phosgene (or transesterification route).

Concept / Approach:
Among the options, PMMA is the only clear example of an addition (chain-growth) polymer, not a condensation product. Therefore it is the correct choice for “not a condensation polymer.”

Step-by-Step Solution:

Verification / Alternative check:
Polymer science references classify methacrylate polymers as addition products; phenolic, melamine, and polycarbonate systems are step-growth.

Why Other Options Are Wrong:

• Bakelite/melamine/polycarbonate: all produced by condensation/step-growth pathways.

Common Pitfalls:
Assuming “transparent” implies addition; transparency is an optical property, not a mechanism indicator.

Final Answer:
Polymethyl methacrylate (PMMA)