Ftir Spectra of Milled Wood Lignins and Lignin Polymer Models (DHP's) with Enhanced Resolution Obtained by Deconvolution

Abstract

FTIR spectra of spruce, beech, and bamboo MWL's, representing G, GS and HGS lignins, were recorded and examined in the wavenumber range of 1800 to 700 cm⁻¹. The spectra were then submitted to a mathematical self-deconvolution technique in order to resolve the intrinsically overlapped bands. The same procedure was carried out with the IR spectra from two G and two GS dehydrogenation polymers (DHP's) prepared by the “zutropf” (ZT) and “zulauf” (ZL) polymerization method. Thus, approx. 30 bands typical for lignins and lignin-like polymer models were detected in contrast to standard spectroscopic conditions, which render visible 15 to 17 broad bands. Hidden bands, usually visible as shoulders, came to light, i.e. the apparent resolution was increased considerably by deconvolution. The deconvolved spectra are standardized and depicted in the absorption mode together with the original spectra. The wavenumbers and intensities of 54 bands apparent after deconvolution are compiled in a Table to render possible a direct comparison of the IR characteristics of lignina and DHP's. A difference spectrum obtained by subtraction of a G ZT DHP spectrum from a spruce MWL spectrum illustratea the differences between these polymers.