Chemical modification employed as a means of probing the cell-wall micropore of pine sapwood

Abstract

The cell-wall micropore network of oven-dried Corsican and Scots pine sapwood has been investigated by reaction with acetic and propionic anhydride in a non-swelling solvent (xylene). No significant reaction occurred, except in the case of reaction between Corsican pine and acetic anhydride. However, when the wood samples were in a swollen state, reaction occurred between the wood and both anhydrides. It is concluded that the cell-wall micropores of Corsican pine are sufficiently large to allow access of acetic anhydride, but not propionic into the unswollen cell wall; however, with Scots pine, both reagents are too large to gain access. A further series of experiments was performed whereby the volumetric changes of pine sapwood samples due to modification with a range of linear chain anhydrides were determined. With Corsican pine, larger volume changes than theoretically predicted were observed, whereas, with the Scots pine samples, the volume changes were close to those predicted. When account is taken of the volume that the reagent occupies within the cell wall, it was found that larger void volumes occurred in the Corsican pine samples. This result indicates that the cell-wall polymeric environment surrounding a reagent molecule is more compliant in the case of Corsican pine.