Different film treatment methods were explored for the FTIR measurements. These were (1) the use of air-dried film; (2) the use of films that had been washed for 30 min in a continuously stirred bath of an aqueous solution of a surfactant (2% w/w sodium dodecyl sulfate), rinsed in deionized water, and dried overnight at 60 °C; and (3) the use of films that had been swollen in toluene at room temperature for 3 days and dried (60 °C, overnight). The objective of treatment 3 was to leach any small molecules and residual reagents through the swollen rubber network. The different treatment methods were found to not affect the FTIR spectra (data not shown). Subsequently,the spectra were recorded only on thin films that had been washed with the surfactant (treatment method 2, above). These FTIR spectra are shown in Figure 4.