High-use temperature, lightweight polymer/inorganic nanocomposite materials are described having enhanced thermal stability and performance characteristics. These materials are made possible by new methods for synthesizing composite materials that enhance the thermal stability of the nanocomposite systems from 100-150 C. to over 450 C. These materials and techniques for their formation are enabled at least in part by the use of polar organic phthalonitrile monomers and oligomers that can exfoliate layered phyllosilicates, such as smectite clays, in percentages greater than 10% inorganic by weight. This approach offers a solvent-free direct melt intercalation technique that greatly reduces the cost of processing nanocomposites. Additionally, the use of unmodified phyllosilicates overcomes temperature limitations of prior art, which uses organically-modified layered silicates. The new technology provides hitherto unobtainable thermal stability and performance characteristics, and has numerous applications in the automotive, aerospace, electronic and marine industries.