Prediction and characterization of macromolecular structure of cutinite from luquan cutinitic liptobiolith with molecular simulation

This paper presents a methodology of molecular construction and characterization of the cutinite from Luquan cutinitic liptobiolith. The structural skeleton parameters of the cutinite were determined by 13C NMR, FTIR, and XPS. The results indicate that the aromaticity of the cutinite residue which was obtained from cutinite by solvent extraction (sequential using methanol, acetone, NMP/CS2 (1:1), and cyclohexanone) was 0.3606. The ratio of bridge/surrounding carbon of cutinite residue was 0.083, implying that structural skeleton of cutinite had 1–2 aromatic rings mainly in the type of naphthalene and benzene. The cutinite residue had higher aliphatic carbon (58.18%) than aromatic carbon (36.06%), thus the structure parameters had low aromatic carbon ratio. The proportion of O –H, C– C=O, and COOR groups in the structural skeleton model was 4:7:9:6, and the mainly nitrogen-containing structures exist in the form of pyrrolic and pyridinic species (2:1). The structure parameters of small molecule in cutinite were determined by GC-MS. The results showed that the small molecule component was mainly composed of 1–2 rings aromatics and linear alkane. The cutinite structure model was constructed by the skeleton parameters combining with small molecule compounds. The cutinite was a cross-linked structure of three fragments, containing cycloalkane, aromatic, and hydroxy or dihydroxy fatty acids. The cutinite molecular skeleton also contained C12-C18 fatty acids and esters, dibasic acids and coumaric acid. The structural skeleton model of cutinite was simulated by Materials Studio and had a molecular formula of C195H231N3O32.