With the preparation and characterisation of oligomer 1 complete, thermal curing was investigated next. The hypothesis was that prolonged heating at 140 °C could induce S-S metathesis reactions as well as reaction of the intermediate thiyl radicals with unreacted alkenes in 1, resulting in a cross-linked material. Indeed, curing oligomer 1 at 140 °C for 24 hours resulted in continued reaction: the Tg increased to 106 °C, providing a hard and brittle material (Fig. ). Solubility studies showed that cured 1 is insoluble in common solvents such as DMF, THF, NMP, chloroform, ethyl acetate, acetone, methanol, isopropanol and water (S26). The cured polymer was smooth, with AFM analysis revealing an average surface roughness of 0.37 ± 0.07 nm and a root mean square roughness of 0.92 ± 0.36 (Fig 2d and). Atomic force microscopy nano-indentation measurements were used to determine the material properties of the cured material. Indentation curves were calibrated and analysed using procedures outlined by Sader et al and Kontomaris et al (S28-S29). This analysis yielded values of 1.49 ± 0.36 GPa for the elastic modulus and 0.25 ± 0.09 GPa and 25.9 ± 9.6 for the surface area hardness and Vickers hardness, respectively. The elastic modulus is comparable to values reported for nylon, PVC and polycarbonate and the hardness is similar to values reported for nylon, PMMA and polystyrene. The TGA profile of cured 1 was distinct from the oligomer precursor, with the former having only a single mass loss starting at 250 °C. Such a profile may be attributable to the lower sulfur rank and stronger S-S bonds formed after curing. After reducing cured 1 with either LiAlH4 or NaBH4 in THF, GC-MS analysis revealed a complex mixture of products, but ones consistent with both S-S metathesis and addition of the polysulfide to the unreacted alkene (see S30-S51 and for additional discussion). Overall, these results indicated that oligomer 1 can be cured to provide a material that is more chemically and thermally resilient.