UC Irvine

We report that photothermal heating of nanoparticles in solution can be achieved via a superheated state of the particles. This state creates nanoscale reaction zones around the particles that reach reaction temperatures far above the bulk solution temperature. These heterogeneous reaction systems improve efficiency in heat driven reactions and the length scale of heating provides new reaction dynamics. To test if these reaction conditions were amenable to traditional organic reactions, we tested if photothermal heating of nanoparticles initiated a radical polymerization. Radical-initiated polymerization of acrylates is a well-studied process initiated heating molecules that decompose into radicals. These radicals, in turn, go on to begin the polymerization process. We report a method where radical polymerization is initiated via photothermal heating of carbon black nanoparticles using a solar simulator. These polymerizations proceed five times faster than polymerizations held at the same measured bulk temperature. Additionally, uniform fibrous morphologies appear at the micron scale when the polymer is examined via SEM. Finally, we report that the photothermal heating acceleration of benzoyl peroxide decomposition results in an order of magnitude increase in reaction rate over bulk heating.