Figure 3
Soluble NH4CN polymers (sol fractions) were obtained using microwave-assisted syntheses at 180 °C. (a) Weight of sol subfractions concentrated by ultrafiltration using several centrifugal devices with different cut offs. In the picture the apparent molecular weights that present the different subfractions are indicated. The data of the polymers produced at 80 °C using a conventional thermal system (CTS) have never been reported before, and they are shown with comparative purposes. The percentage in weight of each subfraction was calculated as [(mg of sol subfraction) / (mg F > 30 kDa + mg F 10–30 kDa + mg F 3–10 kDa + F < 3 kDa)] · 100. Representative UV–vis spectra: (b) of raw sol fractions synthetized in the presence of air; (c) of raw sol fractions synthetized under anoxic conditions of a N2 atmosphere. The inset plot shows the evolution of the relationship between the main bands observed in these spectra over time; (d) of the lightest sol fractions with apparent molecular weights below 3 kDa; (e) of the light sol fractions with apparent molecular weights from 3 to 10 kDa; (f) for the heaviest sol fractions with apparent molecular weights above 30 kDa.
