Synthesis and thermal analysis of crosslinked imidazolium-containing polyester networks prepared by Michael addition polymerization

Several new covalently crosslinked imidazolium-containing polyester networks were prepared by Michael addition polymerization to probe how ionic functionality might affect thermal properties such as glass transition temperature (Tg) and thermal decomposition (Td5%). A structure–activity relationship was investigated involving a variation of the methylene spacer and the counteranion of the acetoacetate precursors. Analysis of Tg by differential scanning calorimetry (DSC) indicated that a longer methylene spacer (n = 6 versus 2) resulted in lower Tg values due to increased chain mobility. It was also discovered that the larger the counteranion, the lower the T g ( B r − >N O 3 − ≈ B F 4 − >C F 3 C O 2 − >NT f 2 − ) . Thermogravimetric analysis (TGA) indicated that the thermal stability of the polyesters was inversely related to the basicity of the counteranion used, following the trend: ( NT f 2 − >B F 4 − >N O 3 − >B r − ) . The exception was the trifluoroacetate-containing polyester, which exhibited the lowest thermal stability.