In-situ visualization of the kinetics of low temperature thiol-epoxy crosslinking reactions by using a pH-responsive epoxy resin

The kinetics of the crosslinking reactions of model thiol-epoxy polymer networks (TEPNs) was visualized by tracking their pH variations. The color transitions of the TEPNs were monitored in real-time and the results were correlated with those of Fourier transform infrared (FT-IR) spectroscopy, isothermal differential scanning calorimetry (DSC), and oscillational rheology. The influence of the glass transition temperatures (Tg) of the TEPNs on the kinetics of the low temperature crosslinking reactions was investigated by employing various TEPNs with different crosslinker functionalities. The mechanical and chemical properties of the TEPNs were also determined and the trends in the data were related to the crosslinking densities (vc) calculated from dynamic mechanical analysis (DMA) measurements.