2007 Research Highlights

Research Area:
Strategic Goal: 1
SPA: Fire

Synthesis of b-aryl ether, phenylcoumaran, and pinoresinol models for studying lignin reactions with model pMDI. Problem Area 2, Component 2

Key Contact: Daniel Yelle, dyelle@fs.fed.us
Partner: US ARS Dairy Forage Research Center, Madison, WI

To investigate the reactivity of hydroxyls in a wood cell wall towards di-isocyanurate (pMDI) adhesive, we used solution-state nuclear magnetic resonance spectroscopy (NMR) to provide a better understanding of covalent bond formation in wood through the identification of wood cell wall components. Finely ball-milled wood cell wall material can be dissolved in a solvent system containing deuterated dimethylsulfoxide (DMSO-d 6) and deuterated N-methylimidazole (NMI-d 6). High-resolution two-dimensional NMR, using gradient-HSQC 1-bond 13C- 1H correlation of cell wall material of loblolly pine reveals the chemistry of major cell wall components in their most native state currently possible. This non-degradative dissolution of the wood cell wall offers the potential to analyze the bonding interactions between cell wall components and wood adhesives. A model of polymeric methylenebis[phenylisocyanate] (pMDI) is used to react with ball-milled wood, milled-wood lignin, b-aryl ether model, holocellulose, and cellobiose. The spectra of the reacted ball-milled wood reveal which wood cell wall components (and their respective hydroxyls) are reacting with the isocyanate model to form carbamates. The chemical shifts of the reacted wood model compounds correspond to that of the reacted ball-milled wood, indicating direct evidence of covalent bond formation and hint towards order of reactivity between wood components.