displays the FTIR spectra of SKL at different acetylation levels; spectra were normalized with respect to the peak at 856 cm−1, which is attributed to C–H bending on aromatic rings. As the amount of Ac2O decreased from 15 to 0.66 ml/g SKL, intensity of the hydroxyl peak at 3400 cm−1 increased significantly. Also, the weight gain of lignin after reaction with Ac2O moderated from 18% to 5%. Larger content of hydroxyl group retained by these reaction conditions led to increased reactivity/crosslinking of the precursor during subsequent thermo-oxidation step. This enhanced crosslinking enabled the stabilized fibers to retain the original fiber shape and size without becoming tacky. At the same time, Ace-SKL obtained from limited acetylation could be fully dissolved in acetone. This optimal composition of Ace-SKL enabled us to process it into thin fibers (as described next) by solution or dry spinning. Thus, 0.66 ml Ac2O/g SKL concentration and 0.25 h reaction time were chosen as the conditions for producing precursor for all subsequent experiments.