UV-Induced Frontal Polymerization of a Pt-Catalyzed Hydrosilation Reaction

The bis(acetylacetonato)platinum(II) is a common thermal catalyst for the hydrosilation reaction, and it is reported to serve also as a photoactivated catalyst for hydrosilation addition of silanes to alkenes and alkynes. In this paper, it is demonstrated that the UV‐activation of hydrosilation reaction proceeds via a thermal‐frontal mechanism. UV light activates the polymerization on the surface of the sample and, subsequently, the heat released by hydrosilation generates a thermal front, converting the UV‐generated homogeneous catalyst to a Pt0 heterogeneous catalyst. The UV‐induced frontal polymerization mechanism can exhaustively explain the dark‐curing process observed in the UV‐activated hydrosilation reaction. The hydrosilation reaction can be initiated by UV light; irradiation initially yields a highly active homogeneous catalyst species by the loss of one bidentate ligand, which is subsequently converted to a less‐active heterogeneous catalyst, consisting of Pt0 colloids. This happens through a thermal‐front mechanism.