SYNTHESIS AND CHARACTERIZATION OF NEW 3-NITROPHTHALIMIDOPHENOXY- AND 4-NITROPHTHALIMIDOPHENOXY-CYCLOTRIPHOSPHAZENE MONOMERS AND INTERMEDIATES

Abstract

Synthesis of novel monomers and polymer precursors: hexakis[4-(3′-nitrophthalimido)phenoxy]cyclotriphosphazene (VIIa), hexakis[4-(4′-nitrophthalimido)phenoxy]cyclotriphosphazene (VIIb), tris[4-(3′-nitrophthalimido)phenoxy]tris(phenoxy)cyclotriphosphazene (VIIIa) and tris[4-(4′-nitrophthalimido)phenoxy]tris(phenoxy)cyclotriphosphazene (VIIIb) has been performed by two efficient methods. In method 1, hexakis(4-aminophenoxy)cyclotriphosphazene (III) and tris(4-aminophenoxy)tris(phenoxy)cyclotriphosphazene (IV) are reacted in a single step with 3-nitro- and 4-nitrophthalic anhydride in refluxing phenol and toluene. In method 2, III and IV are condensed with 3-nitro- and 4-nitrophthalic anhydride in an aprotic solvent followed by in situ thermal cyclodehydration of the intermediate respective phthalamic acids. These compounds are yellow crystalline substances and soluble in THE and aprotic solvents. The structure of all the novel compounds has been confirmed by infrared (IR), proton and phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy, elemental analysis and differential thermal analysis (DTA). Thermogravimetric analysis (TGA) of the synthesized compounds VIIIa and VIIIb showed their thermal stability at 395°C and 32% char yield in air at 800°C. These compounds are potential candidates for the preparation of heat-and fire-resistant polymers and resins.

Key Words:

• Hexakis-
• tris- aminophenoxycyclotriphosphazene
• 3-nitro- and 4-nitrophthalimidophenoxy-cyclotriphosphazenes
• monomers
• synthesis
• structural assignments