Hale Bahar Öztürk

Ion-interactions as driving force in polysaccharide assembly

The structure of cellulose is characterised by extensive non-covalent interactions. Recent discussions suggest that hydrophobic interactions between polymer chains also play a significant role in governing cellulose solubility. Surprisingly in almost all cellulose shaping processes, chemical systems or solvents are applied, which base on melts or solutions of charged molecules. Ionic interactions play a significant role in the shaping and modification of cellulose based materials. Dependent on the systems used different principles govern the processes and define the results, e.g. formation of associates with alkali hydroxides, ion-exchange reactions to selectively bind multivalent ions at carboxylic groups, adsorption of dissolved polymers through surface charge neutralisation or metal complex formation, where cellulose takes the role of a polymer ligand system. Presence of charged compounds takes a significant role in cellulose swelling and dissolution, but also directs reassembly of polysaccharide material to solid three-dimensional structures.

Effects of tetramethylammonium hydroxide (TMAH) treatment on interfibrillar structure of lyocell (TENCEL) fibres

Abstract Lyocell fibres were treated with tetramethylammonium hydroxide (TMAH) up to 1·5M, which was demonstrated to be more effective than LiOH, NaOH and KOH treatments at the same concentration in the sole interfibrillar swelling region. The porous structure of fibres was studied by inverse size exclusion chromatography to identify mean pore diameter, total pore area and accessible pore volume. The mean pore diameter of fibres was not affected by TMAH treatments, which was analogous to the effects of NaOH treatment. The degree of swelling, carboxyl content using methylene blue sorption method, depth of colour measured after dyeing with C.I. Direct Red 81 and weight loss changed gradually up to 1·5M. Wide angle X-ray diffraction analyses were applied to identify the crystallinity index and crystallite size normal to the 110, 110 and 020 planes. Treatment using TMAH suggests new possibilities for the pretreatment of lyocell fibres owing to the usage of lower concentration to gain comparable results with the conventional NaOH treatment without loss in tensile properties and with less decrease in carboxyl content and weight loss.

Polysaccharide Fibres in Textiles

Besides naturally grown cellulose fibres like cotton, hemp or flax, interest in textile fibres made up from regenerated cellulose is growing. By sure the use of a polymer material, which is provided by nature in huge amounts, favours its use as more sustainable material compared to oil-based products. However, a much stronger argument is the high variability of the properties that can be achieved, which allows design an extremely wide range of products.