Online monitoring of Silicone Network Formation by Means of In-Situ Mid-Infrared Spectroscopy

The ReactIR™ reaction analysis system was used to monitor the crosslinking copolymerization of trimethylsilyl methacrylate with α,ω-methacryloyl-terminated oligo(dimethylsiloxane). Characteristic infrared bands proved useful to determine the total methacrylate concentration. After less than 12 h at 60 °C using 0.14% 2,2′-azoisobutyronitrile (AIBN), the methacrylate conversion during the crosslinking reaction exceeded 98%. The comparison of the crosslinking reaction with a methacrylate homopolymerization showed that significant autoacceleration occurred during network formation. Time-dependent monomer conversion [M]/[M]0 for TMSMA homopolymerization (run H in Table 1) and the corresponding crosslinking polymerization (run N) as revealed by the peak at 1 326 cm−1.