title: Dissolution state of cellulose in aqueous systems. 2. Acidic solvents.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. Electronic address: luisalves@ci.uc.pt.
authors.forename: Luis
authors.initials: L
authors.lastname: Alves
authors.affiliation: Faculty of Sciences and Technology (MEDITBIO), University of Algarve, Campus de Gambelas, Ed. 8, 8005-139 Faro, Portugal.
authors.forename: Bruno
authors.initials: B
authors.lastname: Medronho
authors.affiliation: Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Filipe E
authors.initials: FE
authors.lastname: Antunes
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University, SE-221 00 Lund, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Topgaard
authors.affiliation: Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore; FSCN, Mid Sweden University, SE-851 70 Sundsvall, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Lindman
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D005990:Glycerol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010756:Phosphoric Acids / Q000737:chemistry; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry; D014867:Water / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D002712:Chlorides; D010756:Phosphoric Acids; D012997:Solvents; D013464:Sulfuric Acids; D017967:Zinc Compounds; D014867:Water; C016837:zinc chloride; D002482:Cellulose; C030242:phosphoric acid; C033158:sulfuric acid; D005990:Glycerol
keywords: Acidic solvents; Cellulose ionization; Dissolution; Gelation; Molecular organization; PT ssNMR