Lignin, obtained through steam explosion\ud from straw, was completely characterized via elemental\ud analysis, gel permeation chromatography, ultraviolet and\ud infrared spectroscopy, and 13C and 1H nuclear magnetic\ud resonance spectrometry. Polyurethanes were obtained by\ud treating steam-exploded lignin from straw with 4,4-methylenebis(\ud phenylisocyanate), 4,4-methylenebis(phenylisocyanate)\ud –ethandiol, and poly(1,4-butandiol)tolylene-2,4-diisocyanate\ud terminated. The obtained materials were characterized\ud by using gel permeation chromatography, infrared\ud spectroscopy, and scanning electron microscopy. Differential\ud scanning calorimetry analysis showed a Tg at 6°C,\ud assigned to the glass transition of the poly(1,4-butandiol) chains. The presence of ethylene glycol reduced the yields of\ud the polyurethanes. The use of the prepolymer gave the best\ud results in polyurethane formation. Steam-exploded lignin\ud was used as the starting material in the synthesis of polyesters.\ud Lignin was treated with dodecanoyl dichloride. The\ud products were characterized by using gel permeation chromatography,\ud infrared spectroscopy, 13C and 1H nuclear\ud magnetic resonance spectrometry, and scanning electron microscopy

Lignin obtained from steam explosion of pine was fully characterized. Elemental analysis, GPC, and ultraviolet and 1H and 13C NMR spectra revealed that the obtained lignin contains both guaiacyl and syringyl units. Lignin was dissolved in acetonitrile-ethanol and treated with visible light in the presence of both oxygen and Rose Bengal for different irradiation times. Column chromatography of the residue showed the presence of six compounds: trans-sinapyl alcohol, 4-hydroxy-3,5-dimethoxybenzaldehyde, 4-hydroxy-3,5-dimethoxyphenylacetone, 4-hydroxy-3-methoxybenzaldehyde, cis-sinapyl alcohol, and sinapyl aldehyde. The total amount of fine chemicals increases with the irradiation time. However, it increases rapidly during the first eight hours, but increases slowly after this period. The most important compounds obtained were sinapyl alcohol and 4-hydroxy-3,5-dimethoxybenzaldehyde, but sinapyl alcohol was obtained in the highest amounts after eight hours' irradiation, while the highest amounts of 4-hydroxy-3,5-dimethoxybenzaldehyde were obtained after irradiation for 4 h. After 48 h irradiation comparable amounts of sinapyl aldehyde were obtained. We obtained only compounds derived from the syringyl units in lignin in agreement with the hypothesis that the guaiacyl units are more easily oxidised.

No abstract

ABSTRACT:The synthesis of copolymers between lignin and electron poor alkenes is described. Lignin from steamexploded pine, from steam-exploded straw, and organosolv were used as starting materials. Beforehand, lignins were fully characterized by using elemental analysis, ultraviolet spectroscopy, gel permeation chromatography (GPC), Fourier transform infrared (FTIR), and both 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. The synthesis of copolymers was performed using a previously described procedure utilizing calcium chloride and hydrogen peroxide as reagents. FTIR of copolymers showed absorptions due to the presence of both lignin and the electron withdrawing group on the alkene. GPC analysis showed the presence of fractions with high molecular weights: the M z of lignin from pine was 3729 while the copolymer with methyl acrylate showed M z ϭ 383790. Differential calorimetry showed the presence of glass transitions in the range of Ϫ9 to 4.5°C due to the presence of grafted polyalkene chains. When acrylonitrile was used as starting material DSC analysis of the product showed a glass transition at 119°C, which can be attributed to grafted polyacrylonitrile chain. Lignin from steam explosion could be a good raw material in the preparation of graft copolymers. Furthermore, lignin from pine gave better results than that from straw. Finally, lignin from steam explosion gave better results than organosolv lignin. These results can be explained on the basis of the structural properties of used lignins. Both UV and 13 C NMR spectra showed that lignin from pine contained a consistent amount of double bonds.

No abstract