Vapor Sorption–Desorption Phenomena of HD and GB Simulants from Polyurethane Thin Films on Aluminum Oxide via a Quartz Crystal Microbalance

Abstract

Protection and decontamination of surfaces after exposure to chemical warfare agents (CWAs) are of considerable interest to the homeland defense and battlespace operation communities. In this work, polyurethane was spin-coated onto aluminum oxide quartz crystal microbalance (QCM) sensors. Polyurethane film thickness was varied by altering the concentration of the polymer/chloroform solution used for spin-coating. Atomic force microscopy confirmed the formation of smooth, homogeneous films on the QCM sensor surface. Aluminum oxide QCM sensors coated with polyurethane were exposed to saturated vapors of dichloropentane (DCP), a mustard gas (HD) simulant, and dimethyl methylphosphonate (DMMP), a sarin gas (GB) simulant, and the mass uptake, diffusion coefficient, volume fraction, and partition coefficient of the simulant in the film were determined from QCM data. Results showed that both DCP and DMMP readily sorbed into the films although the mass uptake of DCP was greater than that of DMMP owing to DCP’s higher vapor pressure. Additionally, the CWA simulant uptake increased with polyurethane film thickness. Sorption diffusion coefficients were 1 × 10 –13 cm 2 /s and 1 × 10 –12 cm 2 /s for DCP and DMMP vapor, respectively. Simulant desorption was also measured and showed that some DMMP remained in the film/substrate system, while DCP sorption was fully reversible. Reversible desorption for both CWA simulants was relatively quick and independent over the range of film thicknesses studied, with average desorption diffusion coefficients of 2 × 10 –9 cm 2 /s and 1 × 10 –11 cm 2 /s for DCP and DMMP, respectively. Collectively, this study is expected to inform protection and decontamination strategies of equipment and structures upon exposure to CWAs.

Cross-Linked Fluorinated Polyurethanes against Chemical Warfare Agent Simulants: Properties Affected by the Structure of Diisocyanate

“…Because of the piston action of the QCM-D, the change in frequency can be monitored in real time. Based on the Sauerbrey equation (eq ) and the viscoelastic model, the adsorbed DMMP and CEES mass changes (Δ m ) of the coating were calculated, and the viscoelastic response to these two liquids was shown. − Δ m = − C f n × Δ f where Δ f is the change in frequency caused by liquid adsorption to the sensor substrate, n is the frequency overtone ( n = 3 for this work), and C f is the Sauerbrey constant (17.7 ng cm –2 Hz –1 ). Thus, for the case of liquid transport within a rigid coating, the decrease in frequency shows the amount of liquid adsorption.…”

Molecular dynamics predictions of viscosity for organophosphorus liquids

“…The effectiveness of a simulant is dependent on the specific properties being replicated (see Table 4). For a long time, it was assumed that DMMP had been the primary surrogate used to study protection from sarin 15‐18 . However, our recent study 13 revealed that the surface tension, for example, differs significantly between DMMP and sarin, despite their similar molecular size and structure.…”

“…Capturing sarin Adsorption in MOFs 14 DMMP Destruction of sarin stockpiles Decomposition products 20,21 DIMP Aerosol behavior, diffusion 3,70 Viscosity/ surface tension DMMP/ DIMP study protection from sarin. [15][16][17][18] However, our recent study 13 revealed that the surface tension, for example, differs significantly between DMMP and sarin, despite their similar molecular size and structure.…”

“…DMMP is an example of such a simulant for sarin, where the replacement of the fluorine atom and isopropoxy groups with methoxy groups makes it less dangerous (see Figure 4). Although DMMP was previously considered suitable for studying protection from sarin, [15][16][17][18] recent research has shown that DIMP more accurately represents the decomposition of sarin 19 due to its structural similarity. The structure of DIMP, where isopropoxy groups replace the fluorine, leads to the same decomposition products as sarin, 20,21 unlike DMMP.…”

Surface Tension of Organophosphorus Compounds: Sarin and its Surrogates

“…The fluorine and isopropoxy group are replaced by methoxy groups in DMMP, and by two isopropoxy groups in DIMP. While DMMP is a widely used surrogate for studying protection from sarin, − when it comes to studies of destruction of sarin, DIMP is advantageous . The reason is the presence of the isopropoxy group, which provides the same decomposition products as sarin. , This stimulated research on various physicochemical properties of DIMP in recent years. − …”