Dynamic vapour sorption protocols for the quantification of accessible hydroxyl groups in wood

Uimonen, Tuuli; Hautamäki, Saara; Altgen, Michael; Kymäläinen, Maija; Rautkari, Lauri

doi:10.1515/hf-2019-0058

Cited by 12 publications

(9 citation statements)

References 24 publications

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“…One may assume that the intermediate drying step between deuteration and re-protonation resulted in the entrapment of some D 2 O or OD groups within the cell wall. Drying has been shown to trap solvents within the wood structure (Uimonen et al 2020). However, an additional measurement sequence during which the intermediate drying step was omitted, so that the reprotonation in H 2 O vapor for 24 h at 95% RH directly followed after the deuteration in D 2 O vapor, resulted in nearly the same number of remaining OD groups (see Supplementary Fig.…”

Section: Re-protonation After Deuteration In D 2 O Vapormentioning

confidence: 99%

“…The closed the cell wall pores in the dried wood may have not fully re-opened during re-soaking, particularly after the first drying of neverdried wood. This could have resulted in the inaccessibility of some OD groups (Suchy et al 2010) or an entrapment of D 2 O within the cell wall structure (Uimonen et al 2020). However, when the deuterated sections were not dried, but immediately washed in liquid H 2 O for ca.…”

Section: Re-protonation After Deuteration In Liquid D 2 Omentioning

confidence: 99%

“…OH groups in cellulose crystallites are accessible for H-D exchange only at their surface or at irregularities, but not at their core, as shown in a number of studies (Mann and Marrinan 1956;Hofstetter et al 2006;Salmén and Bergström 2009;Lindh et al 2016). Uimonen et al (2020) showed that the complete deuteration of all accessible OH groups in a wood piece of ca. 20 mg requires about ten hours in D 2 O vapor at 95% target RH.…”

Section: Introductionmentioning

confidence: 95%

“…Water accessible OH groups in lignocelluloses can be studied using hydrogen-deuterium exchange that occurs when deuterium oxide (D 2 O) forms hydrogen bonds with OH groups in wood or other cellulosic materials. The exchanged hydrogen can be quantified either gravimetrically by a dry mass increase of 1 g per mol exchanged hydrogen (Pönni et al 2014;Uimonen et al 2020), or spectroscopically by the shift of the OH stretching band to lower wavenumbers (Mann and Marrinan 1956;Hofstetter et al 2006;Salmén and Stevanic 2018). This provides an estimate for the number of accessible OH groups in lignocelluloses, which has been applied to study the relationship between sorption sites and absorbed water (Gibbons 1953;Rouselle and Nelson 1971;Guthrie and Heinzelman 1974;Popescu et al 2014;Altgen et al 2018;Salmén and Stevanic 2018;Thybring et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Humidity-dependence of the hydroxyl accessibility in Norway spruce wood

Altgen

Rautkari

2020

Cellulose

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This study aimed at a better understanding of the wood-water interaction, in particular the role of the hydroxyl accessibility during the humidity-dependent change in moisture content. Thin sections (80 µm) of never-dried Norway spruce sapwood that contained early- and latewood were used for the experiments. Sorption isotherm measurements confirmed the humidity-dependent moisture content changes and the effect of the first drying of the wood sections. Changes in hydroxyl accessibility were then determined by deuteration of the sections using deuterium oxide, followed by their re-protonation in water (H2O) vapor at different relative humidity: 15, 55 or 95%. The deuteration and re-protonation of the wood sections were quantified by dry mass changes as well as by changes in the OH and OD stretching vibrations in the Fourier transform infrared spectra. The results showed that the deuterated sections could be almost completely re-protonated in H2O vapor, nearly irrespective of the applied relative humidity. Therefore, changes in hydroxyl accessibility were not the driving force for the humidity-dependent changes in moisture content. However, a slow re-protonation rate at low relative humidity had to be considered. Nonetheless, a small quantity of OD groups persisted the re-protonation in H2O vapor and liquid H2O, which was not related to the drying of the wood. Graphic abstract

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Section: Re-protonation After Deuteration In D 2 O Vapormentioning

confidence: 99%

Section: Re-protonation After Deuteration In Liquid D 2 Omentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Humidity-dependence of the hydroxyl accessibility in Norway spruce wood

Altgen

Rautkari

2020

Cellulose

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“…By determining the difference in dry mass of the sample before and after conditioning, one can calculate the moles of accessible hydroxyl groups in the sample from the difference in the molar mass of hydrogen and deuterium. For untreated, acetylated and furfurylated wood, a 10-hour D 2 O conditioning period is sufficient for the samples to reach equilibrium [32,35,36,38,62]. However, preliminary trials with SCA-modified wood showed sample mass had not stabilised after 10 h of D 2 O conditioning.…”

Section: Preliminary Sorption Experimentsmentioning

confidence: 99%

Leachability and Decay Resistance of Wood Polyesterified with Sorbitol and Citric Acid

Beck

2020

Forests

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Research Highlights: Polyesterification of wood with sorbitol and citric acid (SCA) increases decay resistance against brown-rot and white-rot fungi without reducing cell wall moisture content but the SCA polymer is susceptible to hydrolysis. Background and Objectives: SCA polyesterification is a low-cost, bio-based chemical wood modification system with potential for commercialisation. Materials and Methods: This study investigates moisture-related properties and decay resistance in SCA-modified wood. Scots pine sapwood was polyesterified at 140 °C with various SCA solution concentrations ranging from 14–56% w/w. Dimensional stability was assessed and leachates were analysed with high-performance liquid chromatography (HPLC). Chemical changes were characterized with attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and spectra were quantitatively compared with peak ratios. Low-field nuclear magnetic resonance (LFNMR) relaxometry was used to assess water saturated samples and decay resistance was determined with a modified EN113 test. Results: Anti-swelling efficiency (ASE) ranged from 23–43% and decreased at higher weight percentage gains (WPG). Reduced ASE at higher WPG resulted from increased water saturated volumes for higher treatment levels. HPLC analysis of leachates showed detectable citric acid levels even after an EN84 leaching procedure. ATR-FTIR analysis indicated increased ester content in the SCA-modified samples and decreased hydroxyl content compared to controls. Cell wall water assessed by non-freezing moisture content determined with LFNMR was found to increase because of the modification. SCA-modified samples resisted brown-rot and white-rot decay, with a potential decay threshold of 50% WPG. Sterile reference samples incubated without fungi revealed substantial mass loss due to leaching of the samples in a high humidity environment. The susceptibility of the SCA polymer to hydrolysis was confirmed by analysing the sorption behaviour of the pure polymer in a dynamic vapour sorption apparatus. Conclusions: SCA wood modification is an effective means for imparting decay resistance but, using the curing parameters in the current study, prolonged low-level leaching due to hydrolysis of the SCA polymer remains a problem.

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Effect of drying on the hydroxyl accessibility and sorption properties of pressurized hot water extracted wood

et al. 2021

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Hot water extraction (HWE) treatment changes the physicochemical properties of the wood, including hygroscopic properties. HWE treatment decreases the hydroxyl accessibility of the wood, but the relevance of other mechanisms that change hygroscopic properties are not fully understood. This study investigates the effect of drying on the hydroxyl accessibility and sorption properties of wood. Pressurized hot water extraction (HWE) treatment was applied at 140 °C for 1–5 h to Scots pine (Pinus sylvestris L.) sapwood samples in order to remove increasingly more hemicellulose from the cell wall matrix. Following HWE treatment, half of the wood samples were oven-dried and then re-soaked, while the other half was kept in a fully saturated state. The samples were investigated by applying a new approach that was based on the deuteration of accessible hydroxyl groups, which was followed by the measurement of mass loss due to re-protonation. Sorption properties of the wood samples were studied by measuring moisture content, sorption isotherms and dimensional changes. The present results showed that accessible hydroxyl group content decreased only due to hemicellulose removal during the HWE treatment and was unaffected by oven-drying. However, oven-drying enhanced the effect of HWE treatments in reducing the water-saturated dimensions and the moisture content of wood. Therefore, the additional reductions in hygroscopicity and water-saturated dimensions were not related to changes in sorption site density.

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Dynamic vapour sorption protocols for the quantification of accessible hydroxyl groups in wood

Cited by 12 publications

References 24 publications

Humidity-dependence of the hydroxyl accessibility in Norway spruce wood

Humidity-dependence of the hydroxyl accessibility in Norway spruce wood

Leachability and Decay Resistance of Wood Polyesterified with Sorbitol and Citric Acid

Effect of drying on the hydroxyl accessibility and sorption properties of pressurized hot water extracted wood

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