The sample was exposed for defined intervals to initiate the polymerization and NMR spectra, collected in between light bursts, were used to measure monomer conversion as a function of light exposure time. Figure shows the disappearance of the vinylic proton resonances of hexyl acrylate monomer at ~ 6 ppm in the spectrum throughout the course of the polymerization. As acrylate double bonds are consumed, both carbon atoms transition from a sp 2 to a sp 3 hybridization, forming the backbone of the polymer, resulting in a decrease in the vinylic resonances. This reduces the NMR peak area by the amount proportional to the decrease in the acrylate-bond population, and hence, the hexyl acrylate monomer population. In addition to a reduction in area, a slight peak broadening and up-field shift of the peaks were also observed as a result of the decrease in monomer mobility due to the increase in polymer molecular weight and subsequently viscosity. Peak areas were then integrated and used to create a conversion (X) profile, where X = 100 * (1 -𝐴 𝑡 /𝐴 𝑖 ) . Here At and Ai are the areas of the vinylic proton resonance at time t and 0, respectively. The conversion profile, shown in Figure , follows a typical progression of a photopolymerization reaction. Here, the initial period of rapid rate of reaction is a result of autoacceleration, in which restricted mobility of active center chain ends leads to a temporary state of minimal termination while diffusion of monomer to propagating active chain ends continues rapidly. Once the viscosity reaches the point at which monomer becomes diffusion-restricted, the rate of propagation decreases significantly. Eventually, the reaction plateaus when its maximal conversion is reached, and monomer ceases to be consumed. Remarkably, despite the polymer reaching a substantial viscosity during the cure, a high signal-to-noise (S/N) ratio was maintained throughout the reaction by optimizing instrument parameters to capture relaxations both in the initial resin as well as the final polymeric state (see Methods, SI). To evaluate the robustness of this peak-identification and integration as a method for tracking the hexyl acrylate monomer concentration, independent C-spectra were collected and analyzed in a similar fashion.