The Influence of Hydrogen Bonding in Wood and Its Modification Methods: A Review

Abstract

Construction wood has a high economic value, and its construction waste also has multiple consumption values. Natural wood has many advantages, such as thermal, environmental, and esthetic properties; however, wood sourced from artificial fast-growing forests is found to be deficient in mechanical strength. This shortcoming makes it less competitive in certain applications, leading many markets to remain dominated by non-renewable materials. To address this issue, various modification methods have been explored, with a focus on enhancing the plasticity and strength of wood. Studies have shown that hydrogen bonds in the internal structure of wood have a significant impact on its operational performance. Whether it is organic modification, inorganic modification, or a combination thereof, these methods will lead to a change in the shape of the hydrogen bond network between the components of the wood or will affect the process of its breaking and recombination, while increasing the formation of hydrogen bonds and related molecular synergistic effects and improving the overall operational performance of the wood. These modification methods not only increase productivity and meet the needs of efficient use and sustainable environmental protection but also elevate the wood industry to a higher level of technological advancement. This paper reviews the role of hydrogen bonding in wood modification, summarizes the mechanisms by which organic, inorganic, and composite modification methods regulate hydrogen bond networks, discusses their impacts on wood mechanical properties, dimensional stability, and environmental sustainability, and provides an important resource for future research and development.

Keywords: hydrogen bond; organic modification; synergistic enhancement; wood.

Figure 1

Location of hydrogen bonding in wood and modification methods [28,29,30,31,32,33,34].

Figure 2

(a) The glucosyl unit is flipped 180 π relative to its neighboring units, indicated by the dashed square, and the black arrow indicates the preferred orientation of the hydroxyl group. (b) Cellulose–cellulose hydrogen bonds interacting between the hydrophilic (i) and hydrophobic (o) planes of CNCs. (c) Hydrogen bond densities of hydrophilic–hydrophobic configurations (Fio-Bio) and hydrophilic–hydrophilic configurations (Fii-Bii) (c1). Velocity of movement of crystals in stick–slip motion (c2). Maximum shear stress of the system (c3) [43]. Stick I, slip I, indicated in red, stick II and slip II, indicated in green.

Figure 3

(a) Infrared spectra of P-CA, A-CA, G-CA, and V-CA. (b) Specific surface area (left) and thermal conductivity (right) of nanocellulose aerogels. (c) Compression Stress (left) and Compression Resilience (right) [47]. Pure nanocellulose aerogels (P-CA), 3-aminopropyltriethoxy-silane-nanocellulose aerogels (A-CA), 3-Glycidyloxypropyltrimethoxysilane-nanocellulose aerogels (G-CA), and vinyltrimethoxysilane-nanocellulose aerogels (V-CA).

Figure 5

(a) Lignin is tightly bound to the angular region of the cell through hydrogen bonding and other covalent bonding interactions. (b) Second-order derivative spectra of natural bamboo poles, mechanically extracted crude fibers, and bamboo cellulose crude fibers at 3270, 3340, 3433, 3560, and 3590 cm⁻¹. (c) Bamboo cellulose crude fiber densification. (d) Highly ordered structure formed by densification of the crude fibers of bamboo cellulose [60].

Figure 7

(a) FTIR spectra of KOH/PF-WB-700-2 before and after adsorption of Congo red (CR) and methylene blue (MB). (b) Rate of adsorption of MB and CR dyes by KOH/PF-WB-700-2. (c) Mechanism of adsorption by KOH/PF-WB biochar [94].

Figure 8

(a) In situ polymerization–hydrolysis–condensation reaction of γ-methacryloyloxyethyltrimethylsilane (MPS). (b) The generated polymer acts as a binder between the microfilaments [115].

Figure 9

(a) Cellulose nanofibers are highly aligned and adjacent fibers form hydrogen bonds. (b) Relative sliding between densely packed wood cell walls involves repetitive processes of formation, breaking, and re-formation of a large number of hydrogen bonds on a molecular scale [123].

Figure 10

(a) Natural wood is cleaned, cross-compressed and densified, with each piece connected to the other by rich hydrogen bonds. (b) Tensile and interfacial bond strength tests of modified poplar (DPW) and balsa (DBW) along different orientations. (c) Tensile strength of modified poplar (DPW) and balsa (DBW) in all directions [133].

Figure 11

(a) Structure of natural wood. (b) Different micro-scale structures of hydrogels. (c) Water-induced self-assembly process forms non-covalently cross-linked cellulose and lignin nanoparticle network structures [134].

Figure 12

Schematic diagram for the fabrication process of metal ion and hydrogen bonding synergistically mediated carboxylated lignin/cellulose nanofibrils composite film [136].

Figure 13

(a) Combination of organic and inorganic substances in the preparation of super-strong formaldehyde-free wood adhesives. (b) Alternative cross-linking in the modification process [137].

Figure 4

(a) Humidity response performance. (b) A large number of water molecules in the MXene–hemicellulose composite membrane is absorbed into adjacent MXene nanosheets as a function of relative humidity, and the layer spacing and resistance of the membrane increase. (c) Modification mechanism of MXene-half-cellulose composite membrane [29].

Figure 6

(a) Adjacent CNFs are prone to re-form hydrogen bonds during fiber sliding. (b) Cascade formation and reorganization of hydrogen bonds between adjacent CNFs, between adjacent LA molecular chains, and between LA nanoparticles and CNFs. (c) LA forms stronger interaction with nanocellulose. (d) Changes in nanocellulose toughness after the addition of 1 wt% LA [30].

Figure 14

Future directions and applications of wood modification.