Fundamental Theme 4 - Polysaccharide-polysaccharide assemblies, development of polysaccharide re-assemblies

Theme leader: Frank Wendler (TITK, Germany)

Abstract:

The aim of the theme is the finding of new structured biopolymers for innovative materials with very special applications. Studying structure-property-relations with a variety of analytical methods, new possibilities for the design of interesting materials will be received. The choice of promising polysaccharides apart from cellulose or mixtures of polysaccharides, variation of the solvent and shaping of polysaccharide blends will be topics of research.
Fundamental theme 4 contains three subtopics. The first subtopic covers the interactions of polysaccharides or mixtures of those in solutions and the solid state after shaping. Thermoplastic processing of polysaccharides blends is the task of the second subtopic, and the third subtopic will focus on supramolecular assemblies by means of polyelectrolyte complexes.

Objectives:

Research focus on structures of polysaccharides in solution and in solid state. By studying the interactions between different kinds of polysaccharides and modifications of those, better understanding of structure-property-relations will be achieved. With a variety of analytical methods a complex description of polysaccharides assemblies will be aspired.
With that knowledge, Theme 4 exhibits a base for applied projects and, consequently, finding of new structured biopolymers for innovative materials with very special applications will be enhanced. Research work of Theme 4 is integrated into the EU strategic issue concerning increased application of biomass materials.

State of the art:

Multicomponent systems (polymer blends, alloys, composites, interpenetrating networks) receive more and more attention regarding their scientific interest and practical applications. Production of complex materials is connected with the knowledge of the interactions between the components from a structural, thermodynamic and kinetic point of view. Therefore it is necessary to consider molecular-structural peculiarities which determine both the formation of monophase or multiphase systems and the system rate of reaching the thermodynamic equilibrium [1].
Cellulose materials offer several advantages when combined with plastics due to their low density, high modulus and high strength, high stiffness, little damage during processing, little requirements on processing equipment, biodegradability and relatively low price [2, 3]. Mainly the hydrogen bonding between -OH groups are recognized as providing the driving forces for the attainment of thermodynamic miscibility in many polyblend systems [4]. There are two ways to produce blends: mixing of the polymers in a softened or molten state and blending of the components from their solutions. Using the first way problems occur due to the incompatibility between the hydrophilic cellulose fibers and the hydrophobic thermoplastic matrix [5]. The variety of solvent systems opened a new way for the systematic preparing of miscible cellulosic/synthetic polymer blends because these systems can also dissolve many synthetic polymers [1]. Considerable efforts have been devoted to the preparation of compatible or miscible blends of cellulose with polyamides [6], polyesters [7], polyethers [8], vinyl polymers [9] and other polysaccharides [10].
Further, it is well-known that pulps containing hemicelluloses are not soluble neither in viscose nor direct dissolution processes. The cristallite size of the pulps is strongly affected by the xylan content in the pulps after acid hydrolysis [11]. Own investigations has been provided with a mixture of cellulose and polyacrylonitrile in BMIMCl [12]. These spun fiber blends show very interesting results concerning an enhanced elongation, reduction of fibrillation tendency and an improved dying behaviour.

References:

1) Cazacu, G. and Popa, V.I. 2004. Blends and Composites Based on Cellulose Materials. In In: Polysaccharide: Structural Diversity and functional versatility, 2nd edition, Ed. S. Dumitriu, Marcel Dekker, New York, Basel, Hong Kong, 1141-1177.
2) Joly, C., Kofman, M. and Gauthier, R.J. 1996. J. Macromol. Sci. A33 (12), 1981.
3) Zadorecki, P. and Michell, A.J. 1989. Polym. Compos. 10, 69.
4) Nisho, Y. 1994. Hyperfine composites of cellulose with synthetic polymers. In Cellulosic Polymers, Blends and Composites, Gilberst, R.D., Ed., Hanser Publishers, New York, 95-113.
5) Raj, R.G., Kokta, B.V. and Daneault, C. 1989. Int. J. Polym. Mater. 12, 239.
6) Nishio, Y. and Manley, R.S.J. 1990. J. Polym. Eng. Sci. 30, 71.
7) Field, N.D. and Song, S.S. 1984. Blends of poly(ethylene terephthalate) and cellulose. J. Polym. Sci., Polym. Phys. 22 (1), 101-106.
8) Nishio, Y., Hirose, N. and Takahashi, T. 1989. Polym. J. 21, 347.
9) Nishio, Y., Haratani, T., Takahashi, T. and Manley, R.S.J. 1989. Macromolecules 22 (5), 2547-2549.
10) Hasagawa, M., Isogai, A., Onabe, T., Usada, M. and Atalla, R.H. 1992. J. Appl. Polym. Sci. 45(11), 1873-1879.
11) Hakansson, H. 2005. Influence of xylan on the acid degradation of hardwood and grass pulps. In proceedings 2nd Workshop on regenerated cellulose and cellulose derivatives, Karlstad, Sweden, Nov. 22-23.
12) Kosan, B., Michels, C. and Meister, F. 2006. In Proceedings 7th International Symposium "Alternative Cellulose Manufacturing, Forming, Properties, Sept. 6-7.

Programme of the work:

a) Processing of solutions and shaping.
Variation of kind and amount of polysaccharides, e.g. cellulose (hemicelluloses), starch or polysaccharides derivatives; Preparation of NaOH solutions; Study and preparation of shaped micro-gels/capsules under flow, phase inversions, preparation of porous objects; Hemicellulose extraction
b) Characterization of the solutions.
Thermal behaviour (DSC, miniautoclave), description of degradation aspects using chromatographic or ESR spectroscopic measurements, stabilizing procedures; rheological aspects, flow and gelation behaviour, in-situ formation of networks; rheology of NaOH solutions, particle size; thermal behaviour (TG, enthalpy relaxation)
c) Characterization of the shaped bodies
Optimization of shaping; Characterization of the dissolving/swelling properties, examination of physical properties (strength, abrasion resistance), characterisation of porosity changes and accessibility (ISEC, sorption), dyeability, finishing and functionalisation; Investigation of the solid state structure in precipitated highly swollen state and in final dry state by means of SEM, WAXS, and NMR; Surface characterisation (zetapotential, AFM, surface tension)
d) Application
Evaluation of applications concerning different assemblies with polysaccharides

Samples prepared will be registered in a data base and are available for all partners involved. Results of measurements should be discussed within the theme for further progress or possible changes of conditions and precising the targets. Verified conclusions should be set up for corporate publication(s).