The thiol-ene addition has been a popular tool for chemists and engineers with advantages such as high yields, fast kinetics, mild reaction conditions, and orthogonality with other functional groups. This chemistry has been used for a variety applications including dendrimer synthesis, surface functionalization, optical materials, hydrolytically stable dental resins, and polymerization methods.<br/>However, a majority of the research has focused on primary thiols, even though secondary thiols were found to have additional benefits such as reduced odor and reduced likelihood of reacting prematurely with the alkene in a pre-mixed solution. As such, the effect of the substitution of the thiol was studied by using model system: three isomers of butane thiol and three different alkenes, a vinyl ether, an allyl ether, and a vinyl siloxane. The kinetic rates were observed using FT-IR and NMR analysis was used to confirm conversion. It was concluded that increasing in substitution of the thiol results in a decreased kinetic rate. Reactions typically went to full conversion (85% or higher), regardless of substitution. The reaction mechanism was further investigated to obtain the reaction coefficients for the kinetic rate. Novel thiol monomers were then synthesized to observe how the substitution affects the polymerization kinetics using FT-IR analysis. Mechanical properties were observed using a DMA and tensometer and solution stability was observed by measuring viscosity changes over time.

Effect of thiol substitution on the thiol-ene polymerization: Kinetics and mechanical properties

2019 Fall National Meeting

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