Table 3.
Assignment of the infrared bands in spectra obtained from the lignin-silica in vitro polymerization reactions
| Peak position (cm−1) | Assignment |
|---|---|
| 470 | Si–O rocking mode |
| 803 | Si–O–Si symmetrical stretching mode |
| 817 | C–H out-of-plane in positions 2, 5, and 6, aromatic |
| 854 | C–H out of-plane in position 2, 5, and 6, aromatic |
| 921 | C–H out-of-plane, aromatic |
| 966 | –HC=CH out-of-plane deformation. |
| 968 | Si–OH stretching |
| 1031 | Aromatic C–H in-plane deformation; plus C–O deformation, in primary alcohols; plus C=O stretch (unconjugated) |
| 1087 | C–O deformation in secondary alcohols and aliphatic ethers |
| 1093 | Si–O asymmetrical stretching mode |
| 1139 | Aromatic C–H in-plane deformation; plus secondary alcohols plus C–O stretch |
| 1214 | C–C plus C–O plus C=O stretch |
| 1267 | C=O stretch |
| 1330 | Coniferyl ring |
| 1367 | Aliphatic C–H stretch in CH3, not in OMe; phenolic OH |
| 1421 | Aromatic skeletal vibrations plus C–H in-plane deformation |
| 1463 | C–H deformations in –CH3 and –CH2– |
| 1506 | Aromatic skeletal vibrations |
| 1598 | Aromatic skeletal vibrations plus C=O stretch |
| 1650 | H2O bending |
| 1662 | C=O stretch |
| 2840–3000 | |
| 2840 | |
| 2871 | C–H stretch in methyl and methylene groups |
| 2935 | |
| 3000 | |
| 3399 | O–H stretch |
Assignment of vibrations is based on Yoshino et al. (1990), Faix (1991), Gunde (2000), Landreau et al. (2012), and Agarwal and Atalla (2016).