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Article

Monovalent Salt and pH-Induced Gelation of Oxidised Cellulose Nanofibrils and Starch Networks: Combining Rheology and Small-Angle X-ray Scattering

1
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
2
Food Innovation and Health, Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, UK
3
School of Pharmacy, University of East Anglia, Norwich NR4 7TJ, UK
4
Centre for Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath BA2 7AY, UK
*
Author to whom correspondence should be addressed.
Current address: LSFC—Laboratoire de Synthèse et Fonctionnalisation des Céramiques, UMR 3080 CNRS/Saint-Gobain CREE, Saint-Gobain Research Provence, 550 Avenue Alphonse Jauffret, 84300 Cavaillon, France.
Academic Editor: Debora Puglia
Polymers 2021, 13(6), 951; https://doi.org/10.3390/polym13060951
Received: 25 February 2021 / Revised: 16 March 2021 / Accepted: 17 March 2021 / Published: 19 March 2021
(This article belongs to the Special Issue Cellulose and Lignin Feedstock for Renewable Materials)
Water quality parameters such as salt content and various pH environments can alter the stability of gels as well as their rheological properties. Here, we investigated the effect of various concentrations of NaCl and different pH environments on the rheological properties of TEMPO-oxidised cellulose nanofibril (OCNF) and starch-based hydrogels. Addition of NaCl caused an increased stiffness of the OCNF:starch (1:1 wt%) blend gels, where salt played an important role in reducing the repulsive OCNF fibrillar interactions. The rheological properties of these hydrogels were unchanged at pH 5.0 to 9.0. However, at lower pH (4.0), the stiffness and viscosity of the OCNF and OCNF:starch gels appeared to increase due to proton-induced fibrillar interactions. In contrast, at higher pH (11.5), syneresis was observed due to the formation of denser and aggregated gel networks. Interactions as well as aggregation behaviour of these hydrogels were explored via ζ-potential measurements. Furthermore, the nanostructure of the OCNF gels was probed using small-angle X-ray scattering (SAXS), where the SAXS patterns showed an increase of slope in the low-q region with increasing salt concentration arising from aggregation due to the screening of the surface charge of the fibrils. View Full-Text
Keywords: cellulose nanofibrils; starch; rheology; SAXS; salt; pH cellulose nanofibrils; starch; rheology; SAXS; salt; pH
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MDPI and ACS Style

Hossain, K.M.Z.; Calabrese, V.; da Silva, M.A.; Bryant, S.J.; Schmitt, J.; Ahn-Jarvis, J.H.; Warren, F.J.; Khimyak, Y.Z.; Scott, J.L.; Edler, K.J. Monovalent Salt and pH-Induced Gelation of Oxidised Cellulose Nanofibrils and Starch Networks: Combining Rheology and Small-Angle X-ray Scattering. Polymers 2021, 13, 951. https://doi.org/10.3390/polym13060951

AMA Style

Hossain KMZ, Calabrese V, da Silva MA, Bryant SJ, Schmitt J, Ahn-Jarvis JH, Warren FJ, Khimyak YZ, Scott JL, Edler KJ. Monovalent Salt and pH-Induced Gelation of Oxidised Cellulose Nanofibrils and Starch Networks: Combining Rheology and Small-Angle X-ray Scattering. Polymers. 2021; 13(6):951. https://doi.org/10.3390/polym13060951

Chicago/Turabian Style

Hossain, Kazi M.Z., Vincenzo Calabrese, Marcelo A. da Silva, Saffron J. Bryant, Julien Schmitt, Jennifer H. Ahn-Jarvis, Frederick J. Warren, Yaroslav Z. Khimyak, Janet L. Scott, and Karen J. Edler. 2021. "Monovalent Salt and pH-Induced Gelation of Oxidised Cellulose Nanofibrils and Starch Networks: Combining Rheology and Small-Angle X-ray Scattering" Polymers 13, no. 6: 951. https://doi.org/10.3390/polym13060951

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