Thermally Induced Twin Polymerization of 4 H ‐1,3,2‐Benzodioxasilines

The twin monomer 2,2′‐spirobi[4 H ‐1,3,2‐benzodioxasiline] ( 1 ) can be polymerized to nanostructured SiO 2 /phenolic‐resin composite material by thermally induced twin polymerization. Thermally induced twin polymerization represents a way to produce nanocomposites simply by thermal induction of twin monomers. Besides 1 , the thermal reaction of several related salicylic (2‐oxybenzylic) silicon molecules has been investigated. The thermal cleavage of the molecules is studied by using several trapping reagents (e.g., vinyl compounds). A significant occurrence of quinone methide adducts indicates that the thermal mechanism proceeds not only by a ring opening at the oxymethylene position, but also with the ortho ‐quinone methide as a central or alternative intermediate. This is supported by product analyses of thermally initialized reactions of 1 and its substituted analogues as well as by quantum chemical calculations.