Effect of poly(ethylene oxide) molecular mass on miscibility and hydrogen bonding with lignin

The effect of the molecular mass of poly(ethylene oxide) (PEO) on lignin-PEO blends was studied using thermal analysis and FT-IR. Differential scanning calorimetry (DSC) analysis revealed miscible blends over the entire blend ratio. A negative deviation in T, from a simple weighted average was observed, indicating the existence of relatively weak favorable interactions between blend components. Analysis of the data revealed no difference in the magnitude or propensity of intermolecular interactions with increasing PEO molecular mass in the kraft lignin-PEO blends. By contrast, the fitting parameters obtained for organosolv lignin were substantially different; the higher molecular mass PEO had a higher propensity to form slightly stronger intermolecular interactions than the lower molecular mass PEO. Low molecular mass poly(ethylene glycol) dimethylether (M-PEG)-lignin blends had a much higher degree of crystallinity than the PEO blends, resulting in an increase in T-g at high PEG content. FT-IR analysis revealed the presence of strong intermolecular hydrogen bonding between lignin and PEO. However, the band shape of the v(OH) region of the M-PEG blends was slightly different from the PEO blends; some of the original lignin inter-and intramolecular hydrogen bonding was still present in the M-PEG-lignin blends.