Synthesis and characterization of novel (amide–imide)-silica composites by the sol–gel process

Novel (amide–imide)-silica composites that can be used to enhance the mechanical properties of high performance polymers have successfully been synthesized by a sol–gel process. In a first step, a dimer containing two chemically pre-formed imide rings has been synthesized and fully characterized. The dimer was then used to synthesize an intermediate with amide linkages and terminal ethoxy-silane groups which were finally reacted with varying amounts of tetraorthosilicate (TMOS) in a sol–gel reaction in order to generate the (amide–imide)-silica composites. The amount of TMOS added to the reaction was found to influence the amount of silica incorporated in the composites as well as their microstructure. It has been observed that the addition of 25% of TMOS with respect to the ethoxy-silane content of the intermediate leads to the formation of a highly homogeneous microstructure with well-defined grains as opposed to an inhomogeneous distribution of pure silica resulting from excess of TMOS in the composite to which 100% of that component was added.