Synthesis and Performance of Cyclomatrix Polyphosphazene Derived from Trispiro-Cyclotriphosphazene as a Halogen-Free Nonflammable Material

Novel cyclomatrix polyphosphazene was designed as a halogen-free nonflammable material and was successfully synthesized through ring-opening and ring expansion of trispiro-cyclotriphosphazene as a precursor. The chemical structure and composition of the synthesized trispirocyclotriphosphazene were characterized by H-1, C-13, and P-31 NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, mass spectroscopy, and elemental analysis. The polymerization of the cyclomatrix polyphosphazene was dynamically monitored by FTIR spectroscopy. The synthesized cyclomatrix polyphosphazene exhibits a highly rigid and brittle nature as well as a high decomposition temperature over 350 C due to its densely cyclic structure. This polyphosphazene material also shows a high limiting oxygen index and a V-0 classification in a UL-94 burning experiment. Such an excellent flame-retardant property is attributed to the trispiro-cyclotriphosphazene on the backbone of the cross-linking system, which can lead to a synergistically effect resulting from the unique combination of phosphorus and nitrogen. With the characteristics of more safety and excellent performance, the cyclomatrix polyphosphazene designed by this work exhibits a broad prospect for electronic and microelectronic applications as a sustainable nonflammable polymeric material.