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<p>This study (1) determined the differences between the dynamic vapor sorption (DVS) behavior of wood subjected to light (H<sub>2</sub>O) and heavy water (D<sub>2</sub>O) vapors at matching equivalent relative humidities (RHs) and (2) developed an in-situ method for studying the transmission-mode Fourier-transform infrared (FTIR) spectra of wood subjected to increasing RHs. The D<sub>2</sub>O-subjected wood was pre-deuterated so that the hydrogen bonding of the native wood with H<sub>2</sub>O was compared with the deuterium bonding that occurs with D<sub>2</sub>O for the DVS and FTIR studies. Fibrous Scots pine sapwood particles were used for the DVS experiments, whereas FTIR spectroscopy involved Scots pine sapwood earlywood microscopic sections placed inside a small RH chamber. The sorption isotherms and hysteresis plots of H<sub>2</sub>O and D<sub>2</sub>O showed statistically non-significant differences between the solvent vapors. However, larger practical differences were observed at higher RHs, with the H<sub>2</sub>O sorption isotherms having higher “equilibrium” moisture contents. The Gibbs free energies of sorption and desorption at equilibrium, as determined from the DVS data, showed statistically significant differences, suggesting that deuterium bonding is more thermodynamically favorable. The sorption and desorption rates obtained from the DVS samples generally indicate that H<sub>2</sub>O vapor subjection progresses initially at faster rates per RH level, without significantly affecting the total experimental time. The accessibility of the hydroxy groups increased somewhat with D<sub>2</sub>O between the before- and after-isotherm scenarios. In the FTIR spectra, H<sub>2</sub>O addition led to higher peak intensities and broader hydroxy band widths due to increased RH. The FTIR spectra for the D<sub>2</sub>O case had a decrease in the hydroxy band area, particularly in the width parameter, while the intensity and width of the formed deuteroxy peak grew as RH increased. The FTIR spectra also provided evidence of a successful hydrogen-versus-deuterium bonding comparison for the DVS study, as the intensities and band widths reverted to their original states after drying using a water-vapor-subjection method like that used in the DVS. Finally, it is hypothesized that deuterated wood is less hygroscopic than native wood, despite the thermodynamic favorability of deuterium bonding. </p> Graphical abstract <p></p>

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In-situ H2O and D2O vapor sorption of native and deuterated Scots pine wood

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月11日

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  • Mikko Valkonen,
  • Tainise Lourençon,
  • Kristiina Lillqvist,
  • Michael Altgen,
  • Lauri Rautkari

摘要

This study (1) determined the differences between the dynamic vapor sorption (DVS) behavior of wood subjected to light (H2O) and heavy water (D2O) vapors at matching equivalent relative humidities (RHs) and (2) developed an in-situ method for studying the transmission-mode Fourier-transform infrared (FTIR) spectra of wood subjected to increasing RHs. The D2O-subjected wood was pre-deuterated so that the hydrogen bonding of the native wood with H2O was compared with the deuterium bonding that occurs with D2O for the DVS and FTIR studies. Fibrous Scots pine sapwood particles were used for the DVS experiments, whereas FTIR spectroscopy involved Scots pine sapwood earlywood microscopic sections placed inside a small RH chamber. The sorption isotherms and hysteresis plots of H2O and D2O showed statistically non-significant differences between the solvent vapors. However, larger practical differences were observed at higher RHs, with the H2O sorption isotherms having higher “equilibrium” moisture contents. The Gibbs free energies of sorption and desorption at equilibrium, as determined from the DVS data, showed statistically significant differences, suggesting that deuterium bonding is more thermodynamically favorable. The sorption and desorption rates obtained from the DVS samples generally indicate that H2O vapor subjection progresses initially at faster rates per RH level, without significantly affecting the total experimental time. The accessibility of the hydroxy groups increased somewhat with D2O between the before- and after-isotherm scenarios. In the FTIR spectra, H2O addition led to higher peak intensities and broader hydroxy band widths due to increased RH. The FTIR spectra for the D2O case had a decrease in the hydroxy band area, particularly in the width parameter, while the intensity and width of the formed deuteroxy peak grew as RH increased. The FTIR spectra also provided evidence of a successful hydrogen-versus-deuterium bonding comparison for the DVS study, as the intensities and band widths reverted to their original states after drying using a water-vapor-subjection method like that used in the DVS. Finally, it is hypothesized that deuterated wood is less hygroscopic than native wood, despite the thermodynamic favorability of deuterium bonding.

Graphical abstract