Fluid self-diffusion in Scots pine sapwood tracheid cells.
The self-diffusion coefficients of water and toluene in Scots pine sapwood was measured using low field pulsed field gradient nuclear magnetic resonance (PFG-NMR). Wood chips of 8 mm diameter were saturated with the respective liquids, and liquid self-diffusion was then traced in one dimension orthogonal to the tracheid cell walls in the wood's radial direction. The experimental echo attenuation curves were exponential, and characteristic self-diffusion coefficients were produced for diffusion times spanning from very short times to times on the order of magnitude of seconds. Observed self-diffusion coefficients were decaying asymptotically as a function of diffusion time, an effect which was ascribed to the cell walls' restriction on confined liquid diffusion. The observed self-diffusion behavior in Scots pine sapwood was compared to self-diffusion coefficients obtained from simulations of diffusion in a square. Principles of molecular displacements in confined geometries were used for elucidating the wood's cellular structure from the observed diffusion coefficients. The results were compared with a mathematical model for diffusion between parallel planes.
Graduate School of Materials Research, Department of Physical Chemistry, Abo Akademi University, Porthansgatan 3-5, FI-20500 Turku, Finland. espen@vistacell.com
Espen H
EH
Johannessen
Eddy W
EW
Hansen
Jarl B
JB
Rosenholm
D002473:Cell Wall / Q000737:chemistry* / Q000502:physiology; D003198:Computer Simulation; D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008962:Models, Theoretical; D028223:Pinus / Q000737:chemistry* / Q000166:cytology* / Q000502:physiology; D041605:Pinus sylvestris; D014050:Toluene / Q000032:analysis / Q000737:chemistry*; D014867:Water / Q000032:analysis / Q000737:chemistry*
D014867:Water; D014050:Toluene