Material synthesis. Two polymer systems were prepared for this study (Fig. ). The first was a copolymer made from sulfur and cyclopentadiene-a polymer recently reported for use in infrared thermal imaging due to its high refractive index (~1.85) and long-wave infrared light transparency. The second polymer was made from sulfur and dicyclopentadiene. The second polymer was selected due to its complementary thermomechanical properties, as it has a similar Young's modulus (1.25 ± 0.39 GPa) but higher glass transition temperature (Tg > 100 ºC) than the cyclopentadiene copolymer (0.93 ± 0.31 GPa and Tg ~ 40 ºC) (See Supporting Information pages S4 and S17). These polymers are subsequently referred to as 50-poly(S-r-CPD) and 50-poly(S-r-DCPD), where 50 designates the mass percentage of sulfur, r indicates the process is a random copolymerization, and CPD and DCPD indicate the specific organic monomer employed (cyclopentadiene and dicyclopentadiene, respectively). This polymer composition was selected to provide useful thermomechanical properties and sufficient S-S bond content for modification, while preventing phase separation or unreacted sulfur contamination that can result for other compositions. Polymer composites were also prepared in which 25 wt% g-Fe2O3 nanoparticles were embedded in the polymer. The g-Fe2O3 nanoparticles were previously shown to enhance heating of otherwise highly insulating sulfur copolymers after exposure to microwave irradiation. The hypothesis in this context was that the g-Fe2O3 nanoparticles would also enhance heating of the polymer composites during exposure to visible and infrared laser light. In the synthesis of 50-poly(S-r-CPD), an equal mass of freshly distilled CPD was slowly added to molten sulfur at 140 ºC. After the addition, the reaction was stirred for 90 minutes to provide a viscous pre-polymer. A portion of the pre-polymer (100-150 mg) was cast between two silicon wafers and cured at 140 ºC for 24 hours in a silicone mold to provide the final polymer substrate (Material 1, Fig. ). For the composites containing g-Fe2O3 nanoparticles, the particles were added to the prepolymer and mixed briefly (5 minutes) in a 140 ºC oven before casting between the silicon wafers and curing at 140 °C for 24 hours to provide Material 2. The 50-poly(S-r-DCPD) was prepared in a similar fashion by first reacting equal masses of sulfur and DCPD at 140 ºC for 2 hours under an atmosphere of nitrogen. The prepolymer (100-150 mg) was then applied between two silicon wafers and cured for 24 hours at 140 ºC to provide the final polymer sample (Material 3). For the composites containing g-Fe2O3 nanoparticles, the particles were first mixed with the pre-polymer with heating (70 ºC) before the viscous mixture was cast between two silicon wafers and cured for 24 hours at 140 ºC to provide Material 4.