Study on the kinetics and mechanism of thermal decomposition of bisphenol A-type polyarylates

Three BPA-type polyarylates (PARS, PARB and PARF) with the same feeding ratio were synthesized by interfacial polymerization by doping three bisphenol A (BPA) derivative monomers (4,4’-sulfobisphenol (BPS), 2,2-bis(4-hydroxy phenyl)butane (BPB) and 9,9-bis(4-hydroxyphenyl)fluorene (BHPF)). The kinetics of thermal decomposition of polyarylate was studied by three methods and the activation energies of PARS, PARB and PARF were 198.34, 218.12 and 234.96 kJ/mol, respectively. The thermal stability of the three polyarylates followed PARS < PARB < PARF. Fitted by the integral Master-Plots method, the random nucleation was the pyrolysis mechanism of BPA-type polyarylates. Further elucidation of the pyrolysis process was attained through the deployment of thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TG/FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). The study suggested that the pyrolysis pathways of polyarylates were significantly influenced by the properties of their backbone groups; specifically, the breaking weaker bonds (e.g., C–S, C–O) facilitated the initial cleavage of molecular chains. This preliminary disruption then catalyzed further decomposition, forming the reactive radicals that subsequently underwent self-association or isomerization, culminating in new compounds. The effect of BPA-derived monomers on the thermal properties and pyrolytic behaviour of polyarylate was clearly demonstrated in this study.