Acid-catalyzed solvolysis of softwood using polyethylene glycol monomethyl ether to produce functional lignin derivatives

Abstract

Glycol lignins (GLs) produced through acid-catalyzed solvolysis of softwood meal using glycols, such as polyethylene glycol (PEG), have been used for the development of functional materials. In this study, GLs with various physical and chemical properties were synthesized via solvolysis with monomethyl ethers of polyethylene glycol (MPEG), such as MPEG-n4 and MPEG-n8. The effects of the reaction time and temperature on the yield, molecular weight, and thermal properties of MPEG-lignin were studied. The yield of MPEG-lignin increased with the solvolysis time. Acid-catalyzed solvolysis using MPEG-n4 occurred faster than that using MPEG-n8. Higher reaction temperature resulted in a higher yield of MPEG-lignin with a higher glass transition temperature (Tg) and viscous thermal flow temperature (Tf). The Tg and Tf of MPEG-lignins increased with the solvolysis time. The MPEG-lignins synthesized at higher reaction temperatures showed a relatively strong carbonyl absorbance band in the infrared spectra, which was ascribed to decomposed sugar derivatives.