An ionic nanocomposite comprising a nanomaterial comprising charged groups disposed on at least a portion of a surface of the nanomaterial and a polymer material comprising charged pendant group and/or end functionalized charged groups, where the charged groups of the nanomaterial and the charged pendant groups of the polymer material have opposite charges and the nanomaterial and polymer material are connected by one or more ionic bonds. A nanomaterial can be nanoparticles comprising sulfate groups disposed on at least a portion of the surface of the nanoparticles. The polymer material can be a polymer with pendant imidazolium groups. An ionic nanocomposite can be present as a film (e.g., a thin film). An ionic nanocomposite can be used in devices. A nanocomposite can be used in various coating application.