Bottom-up synthesis of polymer nanocomposites and molecular composites: Ionic exchange with PMMA latex

Ionic exchange between electrostatically stabilized PMMA latex and aqueous dispersion of nanoparticles or rigid-rod polyelectrolytes of opposite sense is demonstrated to be a flexible approach to fabrication of polymeric-based nano and molecular composites, including layered silicates, indium tin oxide nanoparticles, rigid-rod polyelectrolyte, and carbon nanofibers. The exchange reaction produces a nanoscale coating on the polymer latex surface, providing efficient dispersion of the nanoparticle, interfacial control between the constituents, as well as the potential for hierarchical morphology control. The resulting nano and molecular scale dispersions are thermodynamically stable when an emulsifier that participates with the free-radical polymerization of the MMA is used. The result is direct ionic coupling between the polymer and the nanoparticle, but at a sufficiently low level to maintain solution and melt processibility. Molecular composites of sPBI and PMMA are discussed in detail, and demonstrate increases in heat distortion temperature (17 degreesC) and rubbery modulus (210%) with less than 1% incorporation of the rigid-rod polymer electrolyte.