Throughout the past decade, investigations of thick thermoset thiol–ene networks (TENs) have become increasingly prominent in the literature due to facile, quantitative synthesis giving rise to unique network characteristics, specifically high mechanical energy damping. This article reports the synthesis and thermomechanical properties of ternary thiol–thiol–ene systems that exhibit tunable glass transitions that maintain high, narrow tan δ values in the glass transition region. We begin with a base network of a trifunctional thiol and a trifunctional ene and then systematically substitute the trifunctional thiol with a series of difunctional thiols while maintaining stoichiometric balance between total thiol and ene content. The resultant ternary networks exhibit glass transition temperatures that follow the Fox equation. In contrast to other ternary thiol–ene networks, we observe minimal broadening of the glass transition region, which implies that we can retain the energy-absorbing capabilities of the thiol–ene system. This approach has high potential as a simple tool for scientists and researchers to tune T gs for select networks without detrimentally affecting other physical properties.

In this study, a series of thiol-ene networks having glass transition temperatures ranging from -30 to 60 °C were synthesized utilizing several multifunctional thiols and two trifunctional alkenes. Thermomechanical properties were determined using dynamic mechanical analysis, and impact properties were determined using pendulum impact and drop impact testing protocols. The impact behavior was found to directly correlate to the glass transition temperature, except when the temperature at which the impact event occurs overlaps with the range of temperatures corresponding to the viscoelastic dissipation regime of the polymer. Additionally, we discuss insight into the spatial limitations of energy dissipation for thiol-ene network polymers and establish a platform for predictability in similar systems.

In this study, the effect of water addition on cure kinetics in an epoxy-amine thermoset was investigated. Near FTIR spectra demonstrated that a small amount of water addition significantly accelerated the cure reaction in terms of epoxide conversion, with water acting as a catalyst for the reaction. Use of a modified mechanistic model allowed direct comparison of the effect of hydroxyl groups generated from water addition to those generated from the polymer chain. The comparison of those kinetic parameters shows that the two effects are very close, in which difference in the logarithmic value of the reaction constant is less than one order of magnitude over all the reaction conditions. The kinetic study also confirmed a strong negative substitution effect for this system. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: [4650][4651][4652][4653][4654][4655][4656][4657][4658][4659] 2011

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