title: Thermal mobility of β-O-4-type artificial lignin.
abstract: Several lignin model polymers and their derivatives comprised exclusively of β-O-4 or 8-O-4' interunitary linkages were synthesized to better understand the relation between the thermal mobility of lignin, in particular, thermal fusibility and its chemical structure; an area of critical importance with respect to the biorefining of woody biomass and the future forest products industry. The phenylethane (C6-C2)-type lignin model (polymer 1) exhibited thermal fusibility, transforming into the rubbery/liquid phase upon exposure to increasing temperature, whereas the phenylpropane (C6-C3)-type model (polymer 2) did not, forming a char at higher temperature. However, modifying the Cγ or 9-carbon in polymer 2 to the corresponding ethyl ester or acetate derivative imparted thermal fusibility into this previously infusible polymer. FT-IR analyses confirmed differences in hydrogen bonding between the two model lignins. Both polymers had weak intramolecular hydrogen bonds, but polymer 2 exhibited stronger intermolecular hydrogen bonding involving the Cγ-hydroxyl group. This intermolecular interaction is responsible for suppressing the thermal mobility of the C6-C3-type model, resulting in the observed infusibility and charring at high temperatures. In fact, the Cγ-hydroxyl group and the corresponding intermolecular hydrogen bonding interactions likely play a dominant role in the infusibility of most native lignins.
authors.affiliation: Research Faculty of Agriculture and ‡Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan. uraki@for.agr.hokudai.ac.jp
authors.forename: Yasumitsu
authors.initials: Y
authors.lastname: Uraki
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Keiichi
authors.initials: K
authors.lastname: Koda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kubo
authors.forename: Takao
authors.initials: T
authors.lastname: Kishimoto
authors.forename: John F
authors.initials: JF
authors.lastname: Kadla
mesh_terms: D006860:Hydrogen Bonding; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014934:Wood / Q000737:chemistry*
chemical_list: D011108:Polymers; D008031:Lignin