A metal-free radical technique for cross-linking of polymethylhydrosiloxane or polymethylvinylsiloxane using AIBN†
A new method was developed for the metal-free cross-linking of silicone rubbers. This process uses azobisisobutyronitrile (AIBN) to selectively react with Si–H and vinyl groups as a free-radical initiator for the thermal curing of polymethylhydrosiloxane (PMHS) and polymethylvinylsiloxane (PMVS). The AIBN-initiated curing reaction between the Si–H groups of PMHS generated Si–O–Si and Si–Si cross-links. In contrast, PMVS was cured via the formation of C–C bonds through “methyl–vinyl” and “vinyl–vinyl” mechanisms. Curing reactions were performed at 80–120 °C in air and confirmed by 13C and 29Si solid state NMR analyses and swelling trials.