Theme leader: Volker Ribitsch (University of Graz, Austria)

Abstract:

The projectstargets are to provide specifically surface-modified cellulose materials (fibers, non wovens, membranes) for technical, medical and hygienic application. The oriented cellulose structure will be used as a matrix providing huge surface area and often excellent mechanical properties. This surface shell is modified in order to introduce new properties, for example in technical applications, specific chemical, physical or mechanical properties, selective interaction properties, storage and release capacities for drugs or antimicrobial properties.
The way to obtain these specific cellulose surface properties will comprise surface activation of the cellulose matrix followed by the irreversible adsorption or chemical binding of tailored hemicelluloses, other soluble polysaccharides and polysaccharides derivatives.
Cellulose surfaces will be activated using physical (radiation, plasma treatment) and chemical ways (controlled oxidation, photochemical). A comparison between the reactivity (sorption capacity) of these activated surfaces will be performed for the selection of the best possible procedure (combination of different activation methods).
Different kinds of mannans, xylans, CMC, chitosan and starches as well as derivatives will be used for the modification of surface properties, the tuning of the hydrophilic / hydrophobic character and the introduction of specific functionalities and interaction properties. The compounds functionalization will preferably be gained in homogeneous derivatisation processes.

Objectives:

The described project deals with the isolation, characterization and derivatization of soluble polysaccharides (dis-assembly):
a) Development of surface modifications and functionalisation of cellulose materials (re-assembly)
b) Set up of a structure property relationship.
c) Design of new, high quality and high-value polysaccharides based products.


State of the art:

The field of surface and interface science and technology is an interdisciplinary subject at the forefront of an increasing number of scientific and technological activities in example nanotechnology and catalysis, information technology, material science and bio-medicine during the last decade. The technological use of surfaces and surface processes gains more and more importance.
Non-soluble polysaccharides 1 especially oriented ones exhibit beside their high-value structure huge surface areas and different surface accessibility to different chemical groups. These properties offer material development fields ranging from surface modified cellulose fibres enabling sustainable and environmental friendly processing routs, to surfaces with selective interaction possibilities, surfaces providing a tuneable release of active substances, compound materials exhibiting specific and tuneable interaction properties as well as sensor elements and biocompatible medical devices. There processing happens exclusively in heterogeneous reaction systems causing therefore a dominant role of the surface area and interface processes.
The effect of polysaccharides adsorption on fibres properties as well as the importance of hemicelluloses structure, molar mass, and charge has been investigated stating a positive effect of hemicelluloses on mechanical properties 2, 3 synergy with cationic compounds 4 and improved sorption capability 5. Those studies were focused on the mechanical properties of fibres and demonstrate that significant changes can be achieved. The physical interaction and chemical reaction of the less ordered amorphous structure with function bearing soluble natural and derivatized polysaccharides 6 and polymers, pigments, nano-particles and drugs is not yet well understood and barely used technologically. This knowledge however, is essential when high value tailor made materials are targeted.
The basic understanding for the development of specifically surface modified cellulose materials (fibres, non wovens, membranes) for technical, medical 6 and hygienic application and the know how about new techniques to produce those high value materials will be developed in the fundamental theme 5.

References:

1) Krässig H. A., Cellulose Structure, Accessibility and Reactivity, Polymer Monographs Volume 11, 1993, Gordon and Breach Science Publishers Delgado A.V., Interfacial Electrokinetics and Electrophoresis, 2002, Marcel Dekker
2) Suurnäkki, A, Oksanen, T., Kettunen, H., Buchert, J. (2003) The effect of mannan on physical properties of ECF bleached softwood kraft fibre handsheets. Nordic Pulp Paper Res. J. 18: 429-435.
3) Hannuksela, T., Tenkanen, M., Holmbom, B. (2002) Sorption of dissolved galacto-glucomannans to bleached kraft pulp. Cellulose 9: 251-261
4) Saake, B., Busse, T., Puls, J. (2005) The effect of xylan adsorption on the properties of sulfite and kraft pulp. In: 3th International symposium on wood, fibre and pulping chemistry, Vol. 2, Auckland, New Zealand, 141-146.
5) Lima, D.U., Oliviera, R.C., Buckeridge, M.S. (2003) Seed storage as wet-end additives in papermaking. Carbohydr. Polym. 52: 367-373.
6) Kreze, T., Stana-Kleinschek, K., Ribitsch, V., Persin, Z., Sfiligoj-Smole, M. (2005) The interaction ability of cellulosic materials as a function of fine structure and Helmholtz surface energy. Mater. res. innov. Vol. 9/1, 108-129.

Programme of the work:

a) Create specific cellulose surface properties using physical (radiation, plasma treatment) and chemical (controlled oxidation, photochemical) activations and characterize these surfaces. A comparison between the reactivity (sorption capacity) of these activated surfaces will be performed for the selection of the best possible procedure (combination of different activation methods).
b) Isolation and characterization of mannans, study the interaction kinetics between oriented polysaccharide matrices and dissolved polysaccharide (mannans, chitosan, polyelectrolytes) as a function of molecular properties, structure, chemical functionalities. Compound properties characterization.
c) Isolation and characterization of xylans, study the interaction kinetics between oriented polysaccharide matrices and dissolved polysaccharides (xylans, CMC, hyaluronic acid, polyelectrolytes) as a function of molecular properties, structure, chemical functionalities. Compound properties characterization.
d) Modification of the above mentioned oligo- and polysaccharides in solution in order to introduce different functionalities (i.e. sulfonation, hydrophobic side chains, cyclodextrins, anti-bacterial cationic polymers, specific functional groups).
e) Interaction kinetics between oriented native and/or activated cellulose matrices and dissolved native and/or modified Polysaccharides
f) Establishment of structure-property relationships for the interaction between polysaccharide derivatives and matrix structures. Tune the modification with the target to obtain on one hand irreversible adsorption and on the other hand well defined desorption preferably triggered by external conditions respectively selective adsorption properties.
g) Characterisation of the gained new, surface functionalised materials according to their structure, interaction properties, mechanical, physical and chemical properties.