As SOM pools in BF can be assumed to be older than in the other treatments due to the lack of fresh SOM input, we conclude that increasing aromaticity and decreasing hetero-aliphatic (together with amidic
for the region of methoxyl and N-alkyl groups) properties are indicators for aged and probably stabilised SOM under the given conditions.
As heteroatoms other than oxygen are concentrated into the composition of acetone solubles, the presence of pyrrolic, pyranic, sulphoxidic, metallorganic, letcitinic and other phospholipidic, tioketonic, tioalcoholic, tioureatic, amidic
, and many other fragments containing one or more heteroatoms in the form of remnants, substitutes, derivation or recombination products in this fraction is probable.
1], specific to amidic
NH and C=0 group from the amide linkage, have disappeared entirely, indicating the completion of thermal imidization of the intermediate poly(amic acid) into final polyimide.
1], characteristic to amidic
NH, and the narrow absorption peak at 1650-1660 [cm.
The good solubility of poly (amic acid) precursors in amidic
solvents makes possible the introduction in their solutions of silica precursors and of the water required for hydrolysis process.