title: Silica nanocasts of wood fibers: a study of cell-wall accessibility and structure.
abstract: The porosity and the available surface area of a lignocellulosic fiber can influence the accessibility and reactivity in derivatization and modification reactions because the porous cell-wall network determines the upper size limit for molecules that can penetrate and react with the interior of the wall. To obtain information concerning the accessibility of the porous cell wall of wood fibers, surfactant-templated sol-gel mineralization has been examined. Wood and kraft pulp samples of Norway spruce were impregnated with a silica sol-gel and subsequently heated (calcined) and transformed into structured mesoporous silica. Microscopy studies (environmental scanning electron microscopy, transmission electron microsopy, TEM) on the silica casts showed that the three-dimensional architecture of the wood and pulp fiber cell wall was revealed down to the nanometer level. Image analysis of TEM micrographs of silica fragments from the never-dried pulp revealed complete infiltration of the cell-wall voids and microcavities (mean pore width 4.7 +/- 2 nm) by the sol-gel and the presence of cellulose fibrils with a width of 3.6 +/- 1 nm. Cellulose fibrils of the same width as that shown by image analysis were also identified by nitrogen adsorption measurements of the pore size distribution in the replicas.
authors.affiliation: STFI, Swedish Pulp and Paper Research Institute, Box 5604, SE-114 86 Stockholm, Sweden.
authors.forename: Per Valdemar
authors.initials: PV
authors.lastname: Persson
authors.forename: Jonas
authors.initials: J
authors.lastname: Hafrén
authors.forename: Andrew
authors.initials: A
authors.lastname: Fogden
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Daniel
authors.forename: Tommy
authors.initials: T
authors.lastname: Iversen
mesh_terms: D000327:Adsorption; D002473:Cell Wall / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry; D008031:Lignin / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry; D012542:Scattering, Radiation; D012822:Silicon Dioxide / Q000737:chemistry*; D014934:Wood
chemical_list: C036909:lignocellulose; D012822:Silicon Dioxide; D002482:Cellulose; D008031:Lignin; D009584:Nitrogen