Intermolecular forces ranking: which polymer class exhibits the strongest intermolecular forces among the following?

Introduction / Context:
Mechanical behaviour of polymers depends on intermolecular forces and network structure. A common textbook ordering contrasts elastomers, general thermoplastics, and oriented fibres.

Given Data / Assumptions:

• “Fibres” denote highly oriented, often crystalline polymers (e.g., nylon, PET).
• “Elastomers” are lightly crosslinked with weak intermolecular forces between chains at rest.
• “Thermoplastics” are moderate, semicrystalline or amorphous materials.

Concept / Approach:
Fibres are drawn to high orientation with strong secondary bonding (hydrogen bonding in polyamides, dipole interactions in PET) and significant crystallinity, giving the highest tensile strength and effective intermolecular attractions along the axis. Elastomers have the weakest intermolecular attractions (high chain mobility). General thermoplastics lie in between. “Thermosetting polymers” form covalently crosslinked networks; while their covalent network is very strong, the question compares intermolecular forces (secondary forces) between separate chains. On that basis, fibres are the standard answer.

Step-by-Step Solution:
Identify that fibres possess high orientation and crystallinity.Compare with elastomers (lowest) and general thermoplastics (intermediate).Select fibres as having the strongest intermolecular forces.

Verification / Alternative check:
Textbook strength order: elastomers < thermoplastics < fibres for tensile strength tied to intermolecular attractions and orientation.

Why Other Options Are Wrong:
Elastomers: intentionally low secondary forces for elasticity.Thermoplastics: moderate forces.Thermosets: dominated by covalent crosslinks, not merely intermolecular forces.

Common Pitfalls:
Confusing covalent crosslink strength with intermolecular (secondary) forces terminology.

Final Answer:
Fibres