Condensation/transesterification of dimethyl terephthalate (or terephthalic acid) with ethylene glycol yields which polymer product used for fibres and films?

Introduction / Context:
Identifying monomer pairs is central to polymer synthesis. Dimethyl terephthalate (DMT) or terephthalic acid and ethylene glycol react to form a linear polyester widely used as fibre (Dacron/Terylene) and film/sheet (PET). This question checks accurate mapping between monomers and final polymer identity.

Given Data / Assumptions:

• Aromatic diacid (or its methyl ester): terephthalic unit.
• Aliphatic diol: ethylene glycol.
• Condensation proceeds via transesterification and polycondensation.

Concept / Approach:

Terephthalate units plus ethylene glycol produce polyethylene terephthalate (PET). In fibre form, PET is marketed as Dacron/Terylene; in films/bottles, it remains PET. Other listed polymers arise from different monomer sets: nylon-6 from caprolactam; PVC from vinyl chloride; polycarbonate from bisphenol-A and phosgene or transesterification with diphenyl carbonate.

Step-by-Step Solution:

Verification / Alternative check:

Polymer chemistry texts and industrial routes (DMT or PTA processes) confirm PET formation under antimony, titanium, or germanium catalysts.

Why Other Options Are Wrong:

Nylon-6: Derived from caprolactam ring-opening. Polycarbonate: Requires bisphenol-A and carbonate chemistry. PVC: Chain-growth polymer of vinyl chloride.

Common Pitfalls:

Confusing PET with general “polyester” answers and creating ambiguity; mixing trade names across polymers.

Final Answer:

Dacron (polyethylene terephthalate)