Thermal decomposition of aromatic polyamides with various chemical structures

Tailoring the Structure of Carbon Molecular Sieves Derived from an Aromatic Polyamide

“…Thermogravimetric analysis was used to assess at what temperatures degradation events occur, as this informs what temperatures to conduct later pyrolysis experiments. The polyamide thermogram (Figure S1) indicates that temperatures where degradation events occur are similar to thermograms from previous studies. − ,− During pyrolysis, the precursor polymer chains fragment or break apart. Primarily oxygen, hydrogen, and nitrogen, with relatively smaller amounts of carbon, form other byproducts and detach from the polymer; the species that do not form other gaseous or oil byproducts become a turbostratic carbon structure .…”

“…39−43 Several studies have suggested alternative mechanisms for the thermal degradation of polyamides. 40,41,43,47,48,52 Our work supports previous studies that suggest polyamide chains experience aromatization and fragmentation, producing off-gases such as H 2 O, CO, and CO 2 , due to hydrolytic decomposition, homolytic scission of the aromatic carbon−nitrogen bonds, and a homolytic radical mechanism. 40−42 The major effluent gases, condensable material compositions (Table S1), elemental analysis of CMS (Table S2), and estimated bond hybridizations based on XPS spectra (Figures S3−S6 and Table S3) were used to highlight exemplar chemical structures of the CMS materials.…”

“…The structural properties and pore size distribution can be correlated with the pyrolysis conditions, and hence, degradation mechanisms . The degradation products proposed here can be used with studies that previously investigated the thermal degradation of similar polyamide precursors. − Several studies have suggested alternative mechanisms for the thermal degradation of polyamides. ,,,,, Our work supports previous studies that suggest polyamide chains experience aromatization and fragmentation, producing off-gases such as H 2 O, CO, and CO 2 , due to hydrolytic decomposition, homolytic scission of the aromatic carbon–nitrogen bonds, and a homolytic radical mechanism. − The major effluent gases, condensable material compositions (Table S1), elemental analysis of CMS (Table S2), and estimated bond hybridizations based on XPS spectra (Figures S3–S6 and Table S3) were used to highlight exemplar chemical structures of the CMS materials. Figure S7 shows the fitted C1S spectra, used to estimate bonding hybridization, and Table S3 shows fit parameters for various CMS samples.…”

“…From the 1 H NMR spectrum and literature, we offer that several compounds are present as condensable materials created during pyrolysis including aniline, propenenitrile, and water. While benzene, cyanoaniline, and toluene peaks are present, they are not significant in the NMR spectrum due to the dilute solution, and their presence cannot be confirmed. − ,,, …”

“…While benzene, cyanoaniline, and toluene peaks are present, they are not significant in the NMR spectrum due to the dilute solution, and their presence cannot be confirmed. [40][41][42]47,48,51 Raman spectra for all polyamide-derived CMS were collected to investigate the bond hybridization of CMS samples, and the results are shown in Figure S8. The D (diamond) absorbance band occurs at ∼1360 cm −1 and shows the presence of a defective graphite structure with 3-D connectivity.…”