Infrared initiation of frontal polymerization with density variation multi-layered resins for variable colored layers via photothermal effect

Frontal polymerization (FP) is a unique polymerization technique that involves the self-propagation of heat, which is triggered by a local heat source, such as a photoinitiator. We propose here a novel method for producing colorful polymeric layers through an FP reaction using carbon black (CB) under near-infrared (NIR) irradiation. In the FP reaction, CB and dicyclopentadiene (DCPD) were used as the photothermal agent and monomer, respectively. The photothermal efficiencies of the CB/DCPD suspensions were found to increase with the increase in their CB content. After photothermal initiation, the exothermic FP reaction propagated thermally, resulting in the formation of a freestanding poly (DCPD) resin. In addition, the density of the DCPD suspension in the test tube was adjusted to prepare a multilayered, colored poly (DCPD) resin. Consequently, a four-colored poly (DCPD) resin was obtained via an NIR-induced FP reaction. These results indicate that nanosized CB can be an effective photothermal agent for FP and that the proposed approach can be used for the rapid curing of polymers with multicolored layers with low energy consumption.