Characterization of natural and modified single wood fibers

The main objective of the proposed project is a deeper understanding of the structure -function relationship of the cell- and cell wall level of wood. Wood is known as a complex anisotropic material with excellent mechanical properties with regard to its low density due to the fibrous structure and the tube shape of the wood cells. Wood consists of three main cell wall polymers, cellulose, lignin and hemicelluloses. The elastomechanical properties of the cell wall are determined by the specific agglomeration of the components and their interrelation. Even though mechanical properties of single cell wall components are known and models about the structural arrangement of the polymers exist, their mechanical interaction is not well understood yet. The basic idea of this project is suppressing the functioning of individual cell wall polymers and carrying out micromechanical tests on the modified material in order to learn more about the eliminated polymer by the mechanical behavior without the missing component. Therefore, two fundamental techniques of microstructural treatment of wood will be combined: on the one hand, the recently elaborated method of a mechanical fiber isolation will be applied and on the other hand, specific modification of the cell wall assembly through enzymes will be used. In contrast to chemical isolations of fibers the method of a mechanical isolation provides fibers with unmodified cell wall polymers. These fibers serve as "perfect raw material" for the planned steps of modification. Since chemical treatments are too rough to "manipulate" the highly sophisticated and heterogeneous structure of wood precisely, a very specific tool on the molecular level- like enzymes- is needed. However, for the entire wood, enzyme molecules are too large to effectively penetrate the cell wall, but single fibers provide a much higher accessibility. The micromechanical, ultrastructural and chemical characterization of natural and enzymatically modified single wood fibers, integrating micro-tensile tests, x-ray diffraction, FT-IR spectroscopy, NIR-microscopy and Dynamic Mechanical Analyses (DMA), will give new information on the structure-function relationship on the cell level in general and will provide a better insight into the mechanical relevance and composition of the cell wall polymers in particular. This project represents a fundamental approach to learn from the optimized wooden structure aiming at creating new "intelligent" biomaterials.

The main objective of the proposed project is a deeper understanding of the structure -function relationship of the cell- and cell wall level of wood. Wood is known as a complex anisotropic material with excellent mechanical properties with regard to its low density due to the fibrous structure and the tube shape of the wood cells. Wood consists of three main cell wall polymers, cellulose, lignin and hemicelluloses. The elastomechanical properties of the cell wall are determined by the specific agglomeration of the components and their interrelation. Even though mechanical properties of single cell wall components are known and models about the structural arrangement of the polymers exist, their mechanical interaction is not well understood yet. The basic idea of this project is suppressing the functioning of individual cell wall polymers and carrying out micromechanical tests on the modified material in order to learn more about the eliminated polymer by the mechanical behavior without the missing component. Therefore, two fundamental techniques of microstructural treatment of wood will be combined: on the one hand, the recently elaborated method of a mechanical fiber isolation will be applied and on the other hand, specific modification of the cell wall assembly through enzymes will be used. In contrast to chemical isolations of fibers the method of a mechanical isolation provides fibers with unmodified cell wall polymers. These fibers serve as "perfect raw material" for the planned steps of modification. Since chemical treatments are too rough to "manipulate" the highly sophisticated and heterogeneous structure of wood precisely, a very specific tool on the molecular level- like enzymes- is needed. However, for the entire wood, enzyme molecules are too large to effectively penetrate the cell wall, but single fibers provide a much higher accessibility. The micromechanical, ultrastructural and chemical characterization of natural and enzymatically modified single wood fibers, integrating micro-tensile tests, x-ray diffraction, FT-IR spectroscopy, NIR-microscopy and Dynamic Mechanical Analyses (DMA), will give new information on the structure-function relationship on the cell level in general and will provide a better insight into the mechanical relevance and composition of the cell wall polymers in particular. This project represents a fundamental approach to learn from the optimized wooden structure aiming at creating new "intelligent" biomaterials.