Designing amide linkages in thiol-ene photopolymers. We envisioned that photopolymerization of liquid monomers would allow straightforward formulation of polymer composition by mixing various monomers, which would facilitate the study of material structure-property relationship. As such, we chose free-radical mediated thiol-ene reactions, pioneered by Bowman, Hoyle, and others, as the optimal reaction handle. The capability of thiol-ene photopolymerization to form ideal, step-growth networks is of particular importance to our study. We could not find amide-containing monomers that are commercially available. We adopted a similar procedure as reported by Hedrick et al. synthesizing diallyl meta-phthalamides (1,3substitued) from allylamine and corresponding methyl esters, using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst (Scheme 2A). Batches of up to 100 grams were successfully synthesized. We further extended the synthesis to ortho (1,2-substituted) and para (1,4-substituted) diallyl phthalamides with excellent yields (details included in the Supporting Information). We found all three diallyl phthalamides compounds to be crystalline solids (Figure ), though we were able to prepare photopolymerizable liquid resin by melting the phthalamides in the thiol monomers. Photopolymerization of a stoichiometric (by functional groups) mixture of diallyl phthalamides and a mixture of commercially available thiols, namely ethylene bis(3-mercaptopropionate) (EBMP) and tris [2-(3-mercaptopropionyloxy) ethyl] isocyanurate (TEMPIC), proceeded smoothly (Figure ) with a catalytic amount of photoinitiator (2,4,6-trimethylbenzoylphenyl phosphinate, TPO) and 405 nm LED irradiation at 80 °C. The three polymers were found to be glassy materials at ambient (Figure ). Fourier transform infrared (FTIR) spectroscopy confirmed quantitative reaction conversions, consistent with typical thiol-ene photopolymerization systems (Figure ). It is worth noting that the allyl C-H stretch exhibited a shoulder peak at 3090 cm -1 , confirmed by comparing FTIR spectra of allylamine and phthalate esters (Figure ). The three polymers were strong, free-standing films. The meta-substituted film seemed especially tough as we could not tear it apart with our bare hands, which drew our special attention.