Figure 3.

Color patterning with a thermochrome. (a) Evolution of maximum temperature profiles during FROMP of DCPD in a rectangular channel: (i) a zone of spontaneously heated monomer, (ii) rapid, high-temperature polymerization encountered during consumption of the preheated monomer, and (iii) large thermal gradients encountered during unstable propagation. Scale bar = 1 cm. (b) Putative single electron transfer oxidation of DBPDA to form a highly colored and stable radical cation and subsequent temperature-dependent cleavage of the radical cation to form colorless species. Reported half-life determined during ex situ bleaching at 275 °C (Figure S6). (c) Optical image of the sample after the frontal polymerization in a; 2 wt % DBPDA was incorporated into the resin prior to frontal polymerization (sample was polished to remove surface features and enhance visualization of the DBPDA thermochrome). (d) Glass transition temperature (T_g, determined by DSC analysis) and maximum front temperature as a function of distance from the initiation location for a polymerized sample containing 2 wt % DBPDA. Inset is an optical image of the tested sample.