In spite of the large number of studies dedicated to the utilization of technical lignins, the correlation be­tween lignin chemical structure and its properties and functions has not been established yet for most indus­trial applications. Lignin functional properties are most often correlated with physical properties, such as glass transition point (Tg), solubility and, sometimes, with molecular mass distribution (Glasser, 2000) as well as with such compositional features as the ash, carbohy­drate, sulfur, and carbon content. The effect of the chem­ical structure of lignins on lignin performance in specific applications is usually anticipated based on funda­mental knowledge rather than on experimentally estab­lished correlations. For example, the behavior of lignin in polyurethane production is correlated with the amount of hydroxyl groups predominantly. The utiliza­tion of lignin in phenol—formaldehyde (PF) resins re­quires the unsubstituted 5-position of the aromatic ring (o-position to the phenolic hydroxyl group) and therefore higher proportion of G-units is desirable, in contrast to S-units, which cannot participate in this reac­tion. The comparison of lignin reactivity is typically limited to the comparison of lignins originated from different technical processes and different feedstock or­igins (Tejado, 2007; Mansouri and Salvado, 2006; Evtu — guin et al. 1998; Rials and Glasser, 1986). An attempt to correlate lignin structure with its performance includes, for instance, the observation that the presence of ethyl groups in Alcell lignin act as an internal plasticizer and improve the lignin performance in poly(ethylene oxide) blends (Kubo and Kadla, 2004). Another attempt was the correlation of the quantity of aliphatic, phenolic hydroxyl groups and methoxyl groups as well as the lignin Mw with antioxidant lignin properties (Pan et al., 2006). However, the correlations between the amount of phenolic hydroxyls, Mn and the Radical Scav­enging Index observed in this study were rather poor or inexistent (R2 = 0.53 or lower) implying that the depen­dence is more complex and it requires comprehensive lignin structural elucidation.

In summary, it would appear that the main reason for the lack of clear structure—functional performance corre­lations is the high heterogeneity and variability of tech­nical lignins and the absence of widely accepted and understood, quantitative, fast, and simple analytical tech­niques (Glasser, 2000). In the past few years, leveraging all the recent advances made in the development of new lignin analytical techniques, a very comprehensive work on correlation between process parameters and the structure and properties of the produced technical lig­nins was undertaken at the R&D Department of Lignol Innovations, Ltd (Vancouver, Canada) (Balakshin, Berlin et al., 2013). Three categories of feedstock (softwoods, hardwoods, and annual fibers) including various biomass species sourced from different continents were processed under at least 30 different combinations of pro­cess conditions (time, temperature, ethanol concentra­tion, pH, and L:S ratio). The extracted lignins were analyzed using advanced rapid and comprehensive 13C high-resolution NMR spectroscopy coupled with a Cryo — Probe technology for lignin structural characterization, as described above, along with traditional methods for lignin composition analysis, Mw, thermal properties (Tg), antioxidant activity, and other properties generating results for over 50 different characteristics for each lignin sample. This effort generated a very comprehensive

database including several thousands of data points covering a wide diversity of OS lignins (Balakshin and Berlin, 2010). This unique database has been playing a very important role in developing Lignol’s lignin applica­tions helping in the selection of best lignin candidates for specific customer needs. Moreover, very accurate models correlating process parameters and lignin characteristics have been also developed on the basis of these studies (Balakshin, Berlin et al., 2013).