Photothermal Curing of Polydimethyldisiloxane: Carbon Black Composites Results in Changes to Polymer Topography, Cross-Link Density, and Mass Density

Photothermal heating using light-absorbing nanoparticles has recently emerged as a means to drive the rapid on-demand curing of thermally cured thermosets. However, the effects of extreme localized heat on the resulting polymers have rarely been considered. Herein, we examine the Shore hardness, gel fraction, cross-link density, and mass density of polydimethylsiloxane bearing 1% carbon black nanoparticles. We explore these properties as a function of curing under three conditions: 60 s exposure to 3.5 W/cm² of 808 nm continuous wave laser light, resting at room temperature for 48 h, and heating in a 150 °C oven for 60 min. We also explore 15 combinations of these conditions. We find that photothermal treatment has a significant impact on the Shore hardness, cross-link density, and mass density. However, we also find that the order in which these treatments are applied is important, where applying nonphotothermal curing to the polymer composite substantially ameliorates the effects of subsequent photothermal treatment.