Study of self-assembly of the lignin model compound on cellulose model substrate

Abstract

Full Paper: Herein we report a topographical study of the supramolecular organization of enzymatically polymerized lignin model compound - dehydrogenative polymer (DHP) of coniferyl alcohol - on cellulose substrate, using the Environmental Scanning Electron microscope (ESM) technique. A comparison of deposits obtained by bulk polymerization in solution and direct polymerization in the presence of cellulose substrate shows distinct differences in supramolecular organization organization. DHP polymerized in solution expresses a 3-D structure with short range ordered motifs, while the polymer formed in the presence of cellulose substrate arranges in a layer compact structure consisting of several domains. Such structures could be described as a two-dimensional hexagonal close packed lattice (HCPL), with the dimension of unit cell in 1 mum range. The domains have a quite regular structure with few lattice defects, forming a good example of two dimensional colloidal crystal. The growth of DHP globules and their assembly into supramolecular structures are integrated in terms of cooperative electrostatic interaction of polymer precursors, with a framework of cellulose OH groups, and interfacial interactions (hydrophilic/hydrophobic) in the course of the structure growth. The results strongly suggest that the carbohydrate matrix in plant cells can serve as a template for lignin structure formation in the plant cell wall.