Catalyst:Monomer We analysed the thermal stability of all SHCPs using thermogravimetric analysis (TGA) in either an inert N2 atmosphere (Figure and Figure ) or in air (Figure ). Negligible weight loss is observed in SHCP-1 and SHCP-2 until >250 °C. With increasing sulfonation density the weight loss prior to and during an isothermal step at 110 °C increases dramatically, reaching a maximum of 21 wt.% for SHCP-10, indicative of a significant increase in water adsorption at high sulfonation densities. XPS measurements showed that the chemical composition of the networks remained unchanged after heating overnight at 120 °C under N2 flow, confirming degradation was not responsible for the weight loss seen in the TGA (Table ). Finally, we employed powder X-ray diffraction (PXRD) to confirm the amorphous nature of all networks (Figure ). The synthetic approach to SHCPs described herein provides a set of acidic non-soluble networks in which the sulfonation density, hydrophilicity, and textural properties can be carefully controlled.