Can interparticle contacts in polymer nanocomposites be tuned via photothermal heating of the particle?

Nanocomposite processing presents a paradox: strong particle-matrix interactions facilitate dispersion, thus minimizing the particle doping level needed to form a percolating network. However, they ultimately diminish composite properties, particularly electrical conductivity, as current must pass through insulating matrix caught between conducting particles. Ideally, particle-matrix interactions would be strong during fabrication to maximize dispersion and then altered to favor particle-particle contact and expel inter-particle matrix after solidification. We present results utilizing photothermal heating of multi-walled carbon nanotubes (CNT) to explore this paradigm. Photothermal heating is a process whereby light is absorbed by nanoparticles resulting in localized heat: illuminating a composite results in significant temperature increase around each particle (and particle-particle junctions) while regions far from the particles remain cool. We discuss the effects of photothermal treatment of CNT-polymethylmethacrylate composites during fabrication (casting from solvent) and in solid form with and without applied current with the goal of understanding how the particle-matrix interaction can be manipulated with heat.