$$\rightleftharpoonup{xx}$$
$$\longleftharp{xx}$$,
$$\longrightharp{xx}$$,
Nitrogen adsorption was used to evaluate the treated fabric following the dip coating procedure. As shown in Figure 1, the expected isotherm was obtained for the porous coating. This contrasts with the behaviors noted for the untreated fabric and for the microwave-initiated fabric. Negligible nitrogen adsorption was noted for the fabric alone and the fabric following microwave treatment. No pore sizes were determined. The porous coating produced a surface area of 3.39 m2/g with pore volume 0.013 cm3/g. While the instrument reported a BJH adsorption pore size of 76 Å, no significant features are observed in the pore size distribution. Images of the fabric at each stage in the coating process are provided in Figure 2. The average mass of sorbent deposited on the cotton support was determined to be 0.01 g/g based on the differential weight of samples before deposition and after the final drying process, an increase in weight of ~1% from the original fabric. If the measured surface area and pore volume are corrected to account for only the sorbent mass component of the material, the surface area for the sorbent is 339 m2/g with pore volume 1.3 cm3/g. For comparison, when this sorbent was synthesized as a monolith in a closed reactor, nitrogen porosimetry indicated a BET surface area of 1143 m2/g with pore volume 1.01 m2/g and pore diameter 76 Å26. A type IV-like isotherm was observed for this material with significant hysteresis (Figure 3). A thick film sample was prepared by curing the dip-coating sol in a Petri dish and processing based on the protocol used for coated fabric samples. Nitrogen porosimetry indicated a BET surface area of 968 m2/g with pore volume 0.78 cm3/g and pore diameter 39 Å for this material (Figure 3).
The water vapor transport (WVT) rate for the treated fabrics was evaluated using a two chambered cell4,24,25. This evaluation used a circular fabric sample with a total exposed area of 1.65 cm2. As shown in Figure 4, microwave initiation of the fabric caused a slight reduction in water vapor transport as compared to the untreated cotton. No additional changes in water vapor transport were noted following sorbent deposition or functionalization with porphyrin. The WVT rate for the cotton fabric was determined to be 121 g/h/m2. The WVT rate was reduced to 112 g/h/m2 upon microwave initiation. A WVT rate of 113 g/h/m2 was determined for the full porphyrin-functionalized treatment.
2-Chloroethyl ethyl sulfide (CEES) was used as a simulant to determine whether deposition of the porous treatment resulted in changes to chemical transport properties for the fabric. CEES is commonly used as a simulant for sulfur mustard, a chemical warfare agent. The sorbent material used here consists of ethane-bridging groups and has been functionalized with a copper Deuteroporphyrin IX 2,4 bis ethylene glycol (CuDIX) metalloporphyrin. This reflects the characteristics of the sorbent system demonstrated previously for use in capture of phosgene15,16. Chemical vapor transport was determined using aerosol-vapor-liquid-assessment group (AVLAG) cells23,24. The method uses continuous flow with flame ionization detection (FID) under controlled temperature (40 °C) and relative humidity (50%) for total exposed area of 0.64 cm2. Figure 5 provides time-dependent FID responses. When the cotton fabric alone was evaluated, a peak rate of 67 g/h/m2 was noted with no retention of the target (214 µg total). The porous treatment resulted in significant reduction to both the peak rate of transport (9.6 g/h/m2) and the total transport of target through the fabric. Only 78 µg of the 214 µg CEES originally applied was recovered over an 83 h period. The porphyrin functionalized porous treatment further reduced the peak rate of transport to 4.5 g/h/m2 with a total transport of 39 µg CEES over the 83 h experiment.

Figure 1: Morphological characterization of fabrics. Shown here are representative nitrogen sorption isotherms (A) and pore size distributions (B) for a typical fabric swatch (red), a similar swatch following the microwave initiation process (blue), the fabric following application of the sorbent (green), and the fabric following application of the full sorbent system (black). Please click here to view a larger version of this figure.

Figure 2: Photographs of fabric. The photograph here shows the microwave initiated, sorbent coated material (A), the CuDIX porphyrin alone on cotton (B), and a full porphyrin functionalized coating on the cotton (C). The treated swatches are overlaid on the untreated cotton fabric. Please click here to view a larger version of this figure.

Figure 3: Morphological characterization of unsupported sorbent. Shown here are representative nitrogen sorption isotherms (A) and pore size distributions (B) for the sorbent when synthesized as a monolith (black) and when synthesized as a thick film (red)26. Please click here to view a larger version of this figure.

Figure 4: Water vapor permeation. Results from water vapor permeation analysis are presented for the complete CuDIX porphyrin functionalized sorbent on cotton fabric (black). Cotton fabric only (red) and cotton fabric with only the sorbent component (blue) are presented for comparison. Please click here to view a larger version of this figure.

Figure 5: Permeation of CEES. Permeation of CEES through a complete porphyrin functionalized sorbent coating on cotton fabric is presented (black). Fabric only (red) and fabric with only the sorbent component (blue) are presented for comparison. The inset provides a zoomed view of the initial breakthrough period for the three materials. Please click here to view a larger version of this figure.