Thiol-X reactions constitute reactions where thiols add to one of many reactive functional groups; notably such reactions include the radical-mediated thiol-ene and the anionic thiol-Michael. These are typically characterized by highly efficient reactions, but the reaction’s efficiency comes with the tradeoff of formulation instability and thiols often have an unpleasant odor.

Secondary thiols are reported to possess less offensive odor than their primary thiol counterparts and exhibit longer shelf-lives in thiol-ene formulations, but more information is needed about how the substitution of the thiol affects a variety of thiol-X reactions. This thesis has focused on determining how the thiol substitution affects the thiol-ene, thiol-Michael, and thiol-thioester exchange reactions and materials made from such reactions. To study the thiol-ene and thiol-Michael reactions, model studies were completed using FTIR and NMR spectroscopy.

It was found that for all three substitutions implemented in thiol-ene reactions, there was no significant change in the reaction rate at standard polymerization conditions and at reduced conditions, the reaction rate decreased with increasing substitution, and while most substitutions did not differ greatly in rate, the amount of change in rate is highly dependent on the alkene comonomer.

In thiol-Michael propagation limited reactions (mercaptopropionates), the secondary thiol could be as much as 60% faster due to the increased reactivity of the thiolate anion, though increased steric interactions can override this increased reactivity. In chain transfer limited systems (alkyl thiols) primary thiols were up to 55% faster due to the lower pKa and ease of deprotonation.

Analogous thiol monomers with the corresponding substitutions were then obtained for polymerization studies. It was found that for thiol-ene and thiol-Michael systems, the polymerizations typically followed the pattern seen in model reactions. However, thiol-Michael polymerizations of greater average functionality of the monomer system became more dependent on the substitution and sterics of the monomer. In these cases secondary thiols that were faster in model studies became more limiting.

Finally, the thiol-thioester exchange reaction is a useful method for enhancing thiol-X derived materials by developing covalent adaptable networks and the effect from substitution was observed here as well.