Lignosulfonate-based polyurethane materials via cyclic carbonates: preparation and characterization

Usage of lignin and its derivatives as chemical and carbon source, i.e. in processes other than burning, is one of the most active fields in renewable resource chemistry today. In this study, the synthesis of lignosulfonate (LS)-based polyurethane (PU) materials from non-toxic reagents and through environmentally friendly processes is presented. LS, modified with bio-based (glycerin-derived) cyclic carbonate moieties, was reacted with 1,6-hexamethylenediamine (HMDA) to form characteristic PU material. For mechanistic studies and reaction optimization, cyclic carbonates and 1,2-diol derivatives of vanillyl alcohol (VA), as a simplifying lignin model compound, were employed. An LS-bound cyclic carbonate can be formed in one pot without a transesterification step, which simplifies the route toward non-isocyanate lignin-based PU materials. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra showed typical linkages of cyclic carbonates and 1,2-diols on LS. Further analytical characterization, in both the model compound and the LS polymer case, was provided by liquid-state nuclear magnetic resonance (NMR) spectroscopy [one-dimensional (1D), two-dimensional (2D) and P-31] and C-13 solid-state (ss) NMR. The production of PU materials from sulfonated lignin and glycerol carbonate, synthesized through a non-isocyanate reaction pathway, confirms the good potential of LS utilization in the development of PU composites based on renewable resources.