Project leader: Tommy Iversen
STFI
Tel.: +46 8 676 70 00
Fax: +46 8 411 55 18

Fibre chemistry of supramolecular nanoaggregates

Aim: To supply a knowledge base which facilitates the industrial optimisation of pulp fibre production with regard to the influence of cell wall supramolecular structures on fibre properties.

Background: In preceding projects methods based on CP/MAS 13C-NMR spectroscopy were developed for quantifying the states of order, cellulose crystallinity, and aggregation pattern, hemicellulose and cellulose fibril assembly, found in fibre cell walls. Studies were performed to characterize the supramolecular assemblies present in native wood and in kraft and sulphite pulp fibres prepared from Norway spruce (Picea abies). It was shown that during the kraft pulping of spruce wood, in contrast to sulphite pulping, the aggregation pattern of the polysaccharides changes. Three different structural transformations are consecutively observed during kraft cooking; an increase in lateral cellulose fibril aggregate dimension, an increase in cellulose crystallinity and a change in order or aggregation pattern of hemicelluloses. These structural transformations seem to be closely associated with changes in both the kinetics of the hemicellulose dissolution and the delignification. The changes in the aggregation pattern during drying of pulp, i.e. formation of larger cellulose fibril aggregates (hornification), were also revealed.

If supramolecular cell wall structures can be intentionally altered this will allow a controlled organisation of the polysaccharides into superstructures with channels and pores suitable for ion and molecule transport, or with controlled shapes and symmetries. A design of the structure of the cell wall should thus give rise to new challenging possibilities to optimise industrial pulp fibre processing and to exploit molecular self-assembly for the production of pulp fibres with a wide range of designed properties.

Project description:

1. Investigate the relationship between fibril aggregation (by CP/MAS 13C-NMR) and pore (ultra)structure (by mineralization/molecular imprint, see attached pre-project). 

2. Study the influence of water activity/dynamics/structure on fibril aggregation (cell wall water ultrastructure)

3. Study the influence of the molecular structure, ultrastructure and localisation of hemicelluloses (and lignin) on fibril aggregation.

Project group:

Tommy Iversen (project leader)
Tomas Larsson
Kristina Wickholm

Industrial relevance: 

This project aims at supplying an in-depth understanding of the chemical and physical phenomena governing the aggregation, and de-aggregation, of the cell wall components and how fibre processing may influence the aggregation pattern. An understanding which will enable the Swedish forest products industries to develop radically new approaches to the manufacture of both commodity products, for example based on pulp fibres optimised with respect to fibre properties such as stiffness, fracture resistance, hygrostability, and speciality products such as cellulose whiskers and other structural or functional materials.