Presence, origins and effect of stable surface hydration on regenerated cellulose for underwater oil-repellent membranes

J Justin Koh; Pengfei Pang; Souvik Chakraborty; Junhua Kong; Anqi Sng; Patsaya Anukunwithaya; Shujuan Huang; Xue Qi Koh; Calvin Thenarianto; Warintorn Thitsartan; Dan Daniel; Chaobin He

doi:10.1016/j.jcis.2022.12.109

Presence, origins and effect of stable surface hydration on regenerated cellulose for underwater oil-repellent membranes

J Colloid Interface Sci. 2023 Apr:635:197-207. doi: 10.1016/j.jcis.2022.12.109. Epub 2022 Dec 21.

Authors

Affiliations

¹ Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore; Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.
² Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.
³ Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, 16-16 Connexis North, Singapore 138632, Singapore.
⁴ Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore.
⁵ NUS Environment Research Institute, National University of Singapore, 5A Engineering Drive 1, Singapore 117411, Singapore.
⁶ Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore; Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. Electronic address: danield@kaust.edu.sa.
⁷ Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore; Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. Electronic address: msehc@nus.edu.sg.

PMID: 36587573
DOI: 10.1016/j.jcis.2022.12.109

Abstract

Hypothesis: Underwater oil-repellency of polyelectrolyte brushes has been attributed mainly to electric double-layer repulsion forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Many non-polyelectrolyte materials also exhibit oil-repellent behaviour, but it is not clear if there exist similar electric double-layer repulsion and if it is the sole mechanism governing their underwater oil-repellency.

Experiments/simulations: In this article, the oil-repellency of highly amorphous cellulose exhibiting is investigated in detail, through experiments and molecular dynamics simulations (MDS).

Findings: It was found that the stable surface hydration on regenerated cellulose was due to a combination of long-range electrostatic repulsions (DLVO theory) and short-range interfacial hydrogen bonding between cellulose and water molecules (as revealed by MDS). The presence of a stable water layer of about 200 nm thick (similar to that of polyelectrolyte brushes) was confirmed. Such stable surface hydration effectively separates cellulose surface from oil droplets, resulting in extremely low adhesion between them. As a demonstration of its practicality, regenerated cellulose membranes were fabricated via electrospinning, and they exhibit high oil/water separation efficiencies (including oil-in-water emulsions) as well as self-cleaning ability.

Keywords: Membrane; Oil/water separation; Regenerated cellulose; Surface hydration; Underwater oil-repellency.