*2.5. Contaminant Challenge*

The prepared films were subjected to surface decontamination challenges against the chemical analytes presented in Figure 1, Demeton-*S* (**1**) and 2-chloroethyl phenyl sulfide (CEPS) (**2**), across a range of simulated environmental conditions. In general, a 2.0 μL micropipette was used to apply 1.0 μL of analyte to each sample (2 cm2 ) placed in a transparent Eppendorf tube. Each Eppendorf tube was then sealed and allowed to incubate for determined period of time in controlled conditions (darkness or simulated daylight). For photochemical reactions, a custom-built temperature controlled photochemical reactor equipped with five F8T5D fluorescent bulbs emitting broad spectrum visible light (Figure 2) at 10,000 lux intensity was employed, which simulates overcast daylight exposure. All contaminant challenges, including photochemical challenges, were performed at 20 °C. After which, residual analyte and degradation byproducts were extracted from polymer films with 1 mL of acetonitrile solution containing 12.1 mM tetrahydronaphthalene as an internal standard. Samples were then placed into a 1.5 mL GC auto-sample vial with PTFE septa top and analyzed immediately. In addition to simulant work being performed in a fume hood, personal protective equipment consisting of nitrile gloves, lab coat, chemical safety goggles were employed at all times during handling of chemical simulants.

**Figure 1.** (**1**) Demeton-*S*; (**2**) *S*-vinyl degradation product; (**3**) CEPS; and (**4**) vinyl phenyl sulfoxide.

**Figure 2.** Emission spectrum of custom-built photochemical reactor.

Gas chromatography/mass spectroscopy (GC/MS) was employed to quantify analyte degradation. The GC/MS system consisted of an Agilent 7890A gas chromatograph equipped with an Agilent 5975C mass selective detector operating in electron ionization mode and an Agilent 7693A autoinjector. The column utilized was an Agilent HP-5MS (5% phenyl) methylpolysiloxane film. The carrier gas was helium with a flow rate of 1 mL·min<sup>í</sup><sup>1</sup> . The injection volume was 1 μL with a split injection ratio of 20:1. The temperature program has an initial temperature of 100 °C for one minute, then 25 °C per min ramp to 130 °C followed by a 15 °C per min ramp to 250 °C with a one minute post run hold at 300 °C. The injection temperature, MS quad temperature, and source temperature were 300, 150 and 230 °C, respectively. The solvent delay was set at 1.5 min and detector was set to scan a mass range of 20 to 350 m/z. Prior to comparison, GC/MS results were normalized by dividing the analyte peak area by the peak area of the internal standard, tetrahydronaphthalene.
