/ Research / Fundamental Res... / FT 3 - Derivatives
Fundamental Theme 3 - New derivatives by enzymatic and chemical modifications
Theme leader: Thomas Heinze (University of Jena, Germany)
Abstract:
The Fundamental Theme 3 focuses on synthesis and characterisation of polysaccharide derivatives by highly engineered methods. In case of ionic liquids, standard reactions are expected to provide information about the dissolution of polysaccharides. Investigations of the state of dissolution and the polymer-solvent interaction are of crucial interest. Such solvents are innovative and sustainable media for the polysaccharide extraction and functionalisation under homogeneous conditions.
Control of the functionalisation pattern without using protective groups is of interest for the preparation of larger sample quantities. Structure characterisation by means of NMR spectroscopy will be carried out.
Enzymatic hydrolysis is applied to polysaccharides in order to obtain hydrolysed products under controlled conditions for the preparation of blends with other polysaccharides. The accessibility of polysaccharides for enzymes is influenced by electrolytes, e.g. ionic liquids. Studies of the enzyme kinetics as well of properties of starting materials and products (molecular composition, gelling behaviour, viscosity) will be carried out.
Objectives:
a) Dis-assembly: New paths to dissolve polysaccharides, new derivatisation methods
b) Re-Assembly: Structure and properties characterisation
State of the art:
The efficient dissolution of cellulose is a long-standing goal in cellulose research and development and of great importance up to now. There are various solvents known, however, only N-methylmorpholine-N-oxide monohydrate is applied commercially. The cellulose is processed via direct dissolution to produce fibers (Lyocell process, Rosenau et al., 2001). Many solvents were studied with regard to their application as medium for homogeneous phase chemistry under lab scale conditions (Heinze and Glasser, 1998). The application of N,N-dimethylacetamide/LiCl (Williamson and McCormick, 1998) and dimethylsulfoxide in combination with tetrabutylammonium fluoride trihydrate (Heinze et al., 2000) has broadened the diversity of products and synthesis paths. In addition, the degree of substitution (DS) and the distribution of functional groups may be controlled.
Recently, molten salt hydrates like LiX*n H2O (X=I-, NO3-, CH3COO-, ClO4-) were reinvestigated and proved to be efficient solvents for cellulose (Fischer et al., 1999). Studies on the chemical modification of the dissolved cellulose show that a rather high excess of reagent must be applied, obviously due to the water content, which promotes side reactions (Fischer, 2003).
Very recently, various ionic liquids (IL), so called green solvents (Wasserscheid and Keim, 2000) were found to dissolve cellulose as well (Swatloski et al., 2003). Swatloski et al. (2002) studied various IL including 1-N-butyl-3-methylimidazolium ([C4mim]+) with different anions. A conclusion of these studies was that the chloride ion, as a small hydrogen bond acceptor, seems to be most appropriate for cellulose dissolution. No information about the dissolution mechanism of cellulose in IL is available, which is very important for processing of the polymer. It was already demonstrated that the acetylation in 1-allyl-3-methylimidazolium chloride leads to products of high DS (Wu et al., 2004). Several ionic liquids were studied regarding their ability to act as reaction medium for the acylation and carbanilation of cellulose under homogeneous conditions (Barthel and Heinze, 2006) and for carboxymethylation reactions (Heinze et al., 2005).
References:
1) Rosenau, T., A. Potthast, H. Sixta, and P. Kosma, 2001, Prog. Polym. Sci. 26, 1763.
2) Heinze, Th., W. G. Glasser, 1998, in Cellulose Derivatives: Modification, Characterization, and Nanostructures., eds., Th. Heinze, W. G. Glasser, ACS Symposium Series No. 688, pp. 2.
3) Williamson, S. L, and C. L. McCormick, 1998, J.M.S.-Pure Appl. Chem. A35, 1915.
4) Heinze, Th., M. Vieira, and U. Heinze, 2000, Lenzinger Ber. 79, 39.
5) Heinze, Th., R. Dicke, A. Koschella, E.-A. Klohr, W. Koch, and A. H. Kull, 2000, Macromol. Chem. Phys. 201, 627.
6) Fischer, S., 2003, Habilitation Thesis, University of Freiberg, Germany.
7) Fischer, S., W. Voigt, and K. Fischer, 1999, Cellulose 6, 213.
8) Wasserscheid, P., and W. Keim, 2000, Angew. Chem. Int. Ed. 39, 3772.
9) Swatloski, R. P., S. K. Spear, J. D. Holbrey, and R. D. Rogers, 2002, J. Am. Chem. Soc. 124, 4974.
10) Wu, J., J. Zhang, H. Zhang, J. He, Q. Ren, and M. Guo, 2004, Biomacromolecules 5, 266.
11) Barthel, S., and Th. Heinze, 2006, Green. Chem. 8, 301.
12) Heinze, Th., K. Schwikal, and S. Barthel, 2005, Macromol. Biosci. 5, 520.
Programme of the work:
a) Screening of the reactivity of different polysaccharides, in particular cellulose, dissolved in ionic liquids by standard reactions
b) Preparation of ionic liquids with special properties for polysaccharide dissolution and derivatisation Characterisation of the dissolution properties (solubility and polymer degradation)
c) Dissolution of wood components in ionic liquids
d) Derivatisation of galactoglucomannans in ionic liquids
e) Investigation of enzymatic activity in ionic liquids
f) Enzymatic treatment under well defined conditions
g) Determination of molecular composition
h) Rheological characterisation