What forms the backbone of polyphosphazenes?

Alternating silicon and oxygen atoms

Alternating sulphur and nitrogen atoms

In making polyphosphazenes, what is the role of NaOR or amines?

They replace Cl atoms in (NPCl2)n to give stable polymers

They act as the source of phosphorus

They polymerise the trimer at 250 °C

Which combination describes polyphosphazene properties?

Flexible at low temperature, flame retardant, chemically resistant

Brittle, flammable, soluble in water

Biodegradable by bacteria within days

2069 Bhadra · 2 marks

Short note: Polyphosphazines

Short answer

Polyphosphazenes have a P–N backbone with two substituents on P, prepared by ring-opening polymerisation of (NPCl2)3 and substituting Cl with alkoxy or amino groups. They stay flexible at low temperatures, are flame retardant, and are used for seals, fuel hoses and biomedical implants.

Write a short note on polyphosphazines.

Polyphosphazenes (polyphosphazines) are inorganic polymers with a backbone of alternating phosphorus and nitrogen atoms, –[N=PR₂]ₙ–, with two organic or other groups (R = OR, NHR, F) on each phosphorus.

Preparation: 3PCl₅ + 3NH₄Cl → (NPCl₂)₃ (cyclic trimer) + 12HCl; ring-opening polymerisation of the trimer at 250 °C gives (NPCl₂)ₙ; then the Cl atoms are replaced using NaOR or amines, e.g. (NPCl₂)ₙ + 2n NaOCH₃ → [NP(OCH₃)₂]ₙ + 2n NaCl.

Properties and uses: polyphosphazenes stay flexible even at very low temperatures, are flame retardant and are chemically resistant. They are used for seals and O-rings, fuel hoses, biomedical implants and solid electrolytes.

✓ Answer checked by Claude Opus 5.5 (high effort)

All Engineering Chemistry chapter 4 questions →