Preparation and properties of cellulose/xylan nanocomposites

In this study we have prepared cell wall-like, nanostructured materials by assembly of microtibrillar cellulose produced by Acetobacter xylinum and glucuronoxylan alkali extracted from aspen wood chips. Smooth, almost clear, and very strong films were achieved by drying gel-casted suspensions of homogenized bacterial cellulose and xylan solution. Films were characterized by several different techniques, including atomic force microscopy (AFM), scanning electron microscopy (SEM) and tensile testing. AFM analysis shows that the films are nanostructures composed of a network of randomly oriented microfibrils with xylan in the shape of aggregates between and/or covering the cellulose microfibrils. Tensile tests showed a very strong material with strengths ranging between 65 and 110 MPa. As expected, the tensile strength decreased with decreased cellulose content. Young's modulus, however, passed through a maximum at a xylan content of approximately 33%. The experimental protocol developed in this study makes it possible to prepare nanostructured cell wall-like materials with various cellulose/hemicellulose content and different hemicellulose composition. This is a good start in mimicking secondary cell wall structures.