Abstract
Peak force infrared (PFIR) microscopy is a recently developed approach to acquire multiple chemical and physical material properties simultaneously and with nanometer resolution: topographical features, infrared (IR)-sensitive maps, adhesion, stiffness, and locally resolved IR spectra. This multifunctional mapping is enabled by the ability of an atomic force microscope tip in the peak force tapping mode to detect photothermal expansion of the sample. We report the use of the PFIR to characterize the chemical modification of bio-based native and intact wooden matrices, which has evolved into an increasingly active research field. The distribution of functional groups of wood cellulose aggregates, either in native or carboxylated states, was detected with a remarkable spatial resolution of 16 nm. Furthermore, mechanical and chemical maps of the distinct cell wall layers were obtained on polymerized wooden matrices to localize the exact position of the modified regions. These findings shall support the development and understanding of functionalized wood materials.
Highlights
The three major components of wood are cellulose, hemicellulose, and lignin, whose distinct allocation and structural arrangement within the lignocellulose scaffold are responsible for the unique properties of wood.[1]
The scanning area was chosen on the thickest wood cell wall, called secondary (S2) cell wall, where the fibrous scaffold could be visualized (Figure 3a)
In addition to analyzing native scaffolds, we evaluated the success of chemical modification procedures by visualizing compositional changes at the cell wall level with Peak force infrared (PFIR)
Summary
The three major components of wood are cellulose, hemicellulose, and lignin, whose distinct allocation and structural arrangement within the lignocellulose scaffold are responsible for the unique properties of wood.[1] Because the demand of bio-based materials continually increases, the problem of optimal utilization of this renewable resource arises. Chemical and physical modifications broaden the functionality of wood materials and enable applications under demanding conditions such as outdoor or load-bearing applications.[2] The separation of wooden resources into their components and additional chemical protocols bring further opportunities to create highperformance bio-based polymers.[3] To promote and support new applications of native or functionalized lignocellulosic materials, material behavior should be tied to fundamental knowledge of structural and chemical features of the raw and processed wood materials. Direct nanoscale imaging of chemical group distribution in wood structures is difficult without either sample or instrument modifications, and such reports have been limited so far
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