A: Based on Raman spectroscopy, the type of carbon formed was not significantly affected by the furan ring substitution and network position. The similar ID/IG ratios (1.09 ± 0.02 for PolyFDE, 1.05 ± 0.12 for PolyMethyl-FDE, and 1.09 ± 0.12 for PolyTGDFDA) suggested that an amorphous carbon with minimal graphitic structure was formed across all systems.

A: During the initial decomposition region (100-400 °C), all three furan-based polymers (PolyFDE, PolyMethyl-FDE, and PolyTGDFDA) produced methane, water, acetylene, ethane or nitric oxide, propene, carbon dioxide, diacetylene, and furan. Water and carbon dioxide were generated as a result of furan ring opening.

A: When the furan ring is pendant, its substitution influences char formation. A disubstituted furan ring, as found in PolyMethyl-FDE, is more stable than a monosubstituted furan ring, as in PolyFDE. This increased stability minimizes the disubstituted ring's participation in additional reactions, leading to it potentially cleaving off earlier during thermal decomposition. This results in a lower final char yield for PolyMethyl-FDE (22.4±2.19%) compared to PolyFDE (38.6±0.7%).

A: The network position of the furan ring has a greater impact on char formation than ring substitution. PolyTGDFDA, which contains main-chain furan rings, exhibited the highest char yield of 44.0±0.6% at 1000 ℃ in a nitrogen atmosphere. In contrast, PolyFDE, with pendant, monosubstituted furan rings, showed a char yield of 38.6±0.7%, while PolyMethyl-FDE, with pendant, disubstituted furan rings, yielded 22.4±2.19%.