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EFFICIENT LOW-COST GELS OF CROSS-LINKED POLYELECTROLYTES OR CELLULOSE

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Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents
Publication . Alves, Luis; Medronho, Bruno; Antunes, Filipe E.; Topgaard, Daniel; Lindman, Bjorn
The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.
Effect of ethyleneoxide groups of anionic surfactants on lipase activity
Publication . Magalhães, Solange S.; Alves, Luis; Sebastião, Marco; Medronho, Bruno; Almeida, Zaida L.; Faria, Tiago Q.; Brito, Rui M. M.; Moreno, Maria J.; Antunes, Filipe E.
The use of enzymes in laundry and dish detergent products is growing. Such tendency implies dedicated studies to understand surfactant-enzyme interactions. The interactions between surfactants and enzymes and their impact on the catalytic efficiency represent a central problem and were here evaluated using circular dichroism, dynamic light scattering, and enzyme activity determinations. This work focuses on this key issue by evaluating the role of the ethyleneoxide (EO) groups of anionic surfactants on the structure and activity of a commercial lipase, and by focusing on the protein/surfactant interactions at a molecular level. The conformational changes and enzymatic activity of the protein were evaluated in the presence of sodium dodecyl sulfate (SDS also denoted as SLE0S) and of sodium lauryl ether sulfate with two EO units (SLE2S). The results strongly suggest that the presence of EO units in the surfactant polar headgroup determines the stability and the activity of the enzyme. While SDS promotes enzyme denaturation and consequent loss of activity, SLE2S preserves the enzyme structure and activity. The data further highlights that the electrostatic interactions among the protein groups are changed by the presence of the adsorbed anionic surfactants being such absorption mainly driven by hydrophobic interactions. (c) 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1276-1282, 2016
Dissolution state of cellulose in aqueous systems. 2. Acidic solvents
Publication . Alves, Luis; Medronho, Bruno; Antunes, Filipe E.; Topgaard, Daniel; Lindman, Bjorn
Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution. (C) 2016 Elsevier Ltd. All rights reserved.

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Funding agency

Fundação para a Ciência e a Tecnologia

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Funding Award Number

SFRH/BD/80556/2011

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