Novel Strategy to Evaluate Platinum Photocatalysts for Hydrosilation-Curable Silicones

Hydrosilation, a reaction between silane (Si-H) and vinyl groups, is leveraged in the manufacture of release coatings. However, cross-linking requires high temperatures, leading to this process being generally regarded as time- and energy-intensive. In recent decades, photopolymerization has emerged as an environmentally conscious alternative and is actively being explored due to the advantage that it is a low-temperature cross-linking process. The performance of UV-activated Pt hydrosilation catalysts can be assessed relative to industry-standard MeCpPtMe₃ (Pt-99) by monitoring the cross-linking of model silanes as ultra-thin (2-3 µm thick) films via an industrially relevant novel ATR-FTIR strategy. This strategy improves upon previous methods, in which ≥100 µm thick films are monitored via transmission mode FTIR. The percentage of the hydride consumed after the initial LED excitation (? = 365, 400 nm) was determined by monitoring the bending mode of the Si-H bond relative to an unchanging Si-C stretching mode present in both silicone fluids. This allowed for the generation of percent conversion versus dark cure reaction time plots, as well as the calculation of kinetic parameters including the initial rate, rate constant, and final percent conversion. Eco-inspired innovations inthe curing process will produce novel Pt(IV) photocatalysts that can be evaluated against the current benchmark, with the potential to create UV-cured release coatings on a cost-competitive scale to those cured thermally.