Super-heat resistant polymer nanocomposites based on heterocyclic networks: structure and properties

Nanocomposites based on heterocyclic polymer network, obtained from bisphthalonitrile and different (0.03–5.0 wt.%) contents of modified silicate montmorillonite (MMT) nanolayers, were studied. Their nanostructure, thermal, relaxation and elastic properties were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). DMA and TGA measurements were performed in both air and nitrogen mediums at temperatures from 20$^{\circ}$ to 600–900$^{\circ}$C. Depending on MMT content, different extents of its exfoliation in the matrix, from single nanolayers to thin and “thick” MMT stacks were observed in the nanocomposites. The pronounced effects of constraining dynamics by nanoparticles and dynamic heterogeneity in the glass transition are shown. The possibilities for total suppression of glass transition and invariable elastic properties of nanocomposites within the temperature range from 20$^{\circ}$ to 600$^{\circ}$C were shown. The studied nanocomposites manifest unique (for polymers) thermal properties, with glass transition temperature up to 570$^{\circ}$С and satisfactory thermal stability, with retaining the material integrity, up to $\sim$500$^{\circ}$C in air and to $\sim$900$^{\circ}$C in N$_2$ medium.