Gutta-percha rubber: which statement correctly characterises this material relative to natural rubber?

Introduction / Context:Natural rubber is predominantly cis-1,4-polyisoprene, conferring high elasticity and tack at room temperature. Gutta-percha is trans-1,4-polyisoprene—a stereochemical isomer with very different properties. Distinguishing these forms illustrates how stereochemistry governs polymer mechanics and thermal behaviour.

Given Data / Assumptions:

• Cis vs. trans configuration along the polyisoprene backbone drastically affects chain packing and crystallinity.
• Gutta-percha (trans) is more crystalline and harder at room temperature than natural rubber (cis).
• Thermosets are network polymers; gutta-percha is not crosslinked by default.

Concept / Approach:Trans-1,4-polyisoprene chains pack more efficiently, increasing crystallinity and rigidity; therefore, gutta-percha is relatively hard and non-tacky at ambient conditions. This contrasts with cis-1,4-polyisoprene’s elastomeric character. The key relationship is isomerism, not copolymerisation or thermosetting chemistry.

Step-by-Step Solution:Identify structural difference: cis vs. trans stereochemistry.Relate trans configuration to increased crystallinity and hardness.Conclude that gutta-percha is an isomer of natural rubber (trans-1,4-polyisoprene).

Verification / Alternative check:Physical property tables list higher hardness and lower elasticity for gutta-percha than for natural rubber at room temperature.

Why Other Options Are Wrong:Soft and tacky: describes cis rubber, not gutta-percha.Thermosetting resin: incorrect; gutta-percha is a thermoplastic isomer unless vulcanised.Recovered by coagulation of rubber latex: a general statement for natural rubber production; gutta-percha sources and processing differ.Copolymer with styrene: incorrect; gutta-percha is a homopolymer of isoprene.

Common Pitfalls:Assuming all “rubbers” are elastomeric at room temperature; stereochemistry can produce hard, crystalline variants.

Final Answer:It is an isomer of natural rubber (trans-1,4-polyisoprene).