Soft Nanohybrid Materials Consisting of Polymer–Clay Networks

Abstract

New types of soft nanohybrid materials with novel organic–inorganic network structures, such as nanocomposite gels (NC gels: hydrogel), soft nanocomposites (M-NCs: solid), and their derivatives (MD-NC gels, Zw-NC gels, Pt-NC gels, and P/C-NC microspheres) are described. All soft nanohybrid materials including NC gels and M-NCs were synthesized by in-situ free-radical polymerization in the presence of exfoliated clay nanoplatelets in aqueous systems and were obtained in various forms and sizes with a wide range of clay contents. Here, disk-like inorganic clay nanoplatelets function as multifunctional crosslinking agents to form new types of network structures. The NC gels exhibited extraordinary optical, mechanical, and swelling–deswelling properties, in addition to a number of new characteristics relating to optical anisotropy, polymer/clay morphology, biocompatibility, stimuli-sensitive surfaces, micropatterning, self-healing, etc. The M-NCs also exhibited dramatic improvements in optical and mechanical properties; the latter include ultrahigh reversible extensibility and well-defined yielding behavior, despite their high clay contents. Thus, the serious disadvantages (intractability, mechanical fragility, optical turbidity, poor processing ability, low stimulus sensitivity, etc.) associated with conventional, chemically crosslinked polymeric materials were overcome in the soft nanohybrid materials because of their unique organic–inorganic network structures. Furthermore, several soft nanohybrids with advanced characteristics were developed based on the technologies of NC gel and M-NC syntheses, e.g., new stimuli-responsive NC gels (MD-NC gels), zwitterionic NC gels (Zw-NC gels), platinum nanoparticle-incorporated NC gels (Pt-NC gels), and aqueous dispersions of polymer–clay NC (P/C-NC) microspheres.