Synthesis and pyrolysis mechanism of phenolphthalein poly(aryl ether sulfone) containing isopropyl groups

Abstract

A novel phenolphthalein poly(aryl ether sulfone) polymer containing isopropyl groups (iPrPESC) has been successfully synthesized by SN2 aromatic nucleophilic polycondensation reaction. The pyrolysis mechanism and behavior of iPrPESC were investigated by thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis combined with gas chromatography/mass spectrometry (Py-GC/MS). TG-FTIR and Py-GC/MS were used to identify the thermal decomposition products and to determine the possible thermal degradation mechanism. The main mechanism for iPrPESC was one-stage pyrolysis involving main-chain random scission, and the major products of SO2 and phenol were released from the sulfone and ether groups in iPrPESC. The thermal degradation activation energy of iPrPESC was calculated to be 151 ± 4 and 139 ± 4 kJ mol−1 by the Flynn–Wall–Ozawa and Kissinger methods, respectively, which were much lower than that of phenolphthalein poly(aryl ether sulfone). Furthermore, introduction of isopropyl groups on the main chain can significantly reduce the char yield.