Characterisation of Cellulose- and Lignin-based Materials Using X-ray Scattering Methods

The two most abundant polymers in nature are cellulose and lignin. They are the main components of cell walls of plants. The structure of the cell wall affects the properties of wood products. In wood fibres the cellulose chains spiral in the cell wall, and the helical angle between the direction of the chains and the longitudinal axis of the fibre, the microfibril angle, is one of the parameters that determine the strength of the fibre and the mechanical properties of wood. In this thesis the structure of Sitka spruce was studied using wide-angle x-ray scattering. The microfibril angle was observed to be large close to the pith of the tree but as a function of the annual ring the angle decreased. The annual rings at which the angle reached a small value depended strongly on the origin of the tree. Cellulose is a widely used, environmentally compatible polymer. Recently, it was shown that metal containing cellulose composites could be used as catalysts. In this thesis the structure of cellulose composites containing copper and nickel was characterised using anomalous small-angle x-ray scattering. Metal ions were introduced to the solid cellulose support in an aqueous solution. Cellulose can reduce the metal ions but also more effective reducers were used. Furthermore, lignin derivatives that are separated from the plant cell walls in pulping processes have many uses for example as dispersants. The structure of colloidal and dry lignin derivatives was characterised using small-angle and ultra-small angle x-ray scattering. In sulfite pulping lignin obtains sulfonate groups which make the so-obtained lignosulfonate a weak anionic polyelectrolyte that is soluble in water. The interactions of lignosulfonate particles were characterised in semidilute and concentrated solutions in different ionic strengths and in different temperatures using small-angle x-ray scattering. Classification (INSPEC): A6110F, A6125H