Dynamic and Static Assembly of Sulfated Cellulose Nanocrystals with Alkali Metal Counter Cations

Patrick Petschacher, Reza Ghanbari, Carina Sampl, Helmar Wiltsche, Roland Kádár, Stefan Spirk*, Tiina Nypelö

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles. Here, we introduce the alkali metal counter cations, Li+, Na+, K+, Rb+, and Cs+, on sulfated CNCs without an ion exchange resin, which, so far, has been a common practice. We demonstrate that the facile ion exchange is an efficient method to exchange to any alkali metal cation of sulfate half esters, with exchange rates between 76 and 89%. The ability to form liquid crystalline order in rest was observed by the presence of birefringence patterns and followed the Hofmeister series prediction of a decreasing ability to form anisotropy with an increasing element number. However, we observed the K-CNC rheology and birefringence as a stand-out case within the series of alkali metal modifications, with dynamic moduli and loss tangent indicating a network disruptive effect compared to the other counter cations, whereas observation of the development of birefringence patterns in flow showed the absence of self- or dynamically-assembled liquid crystalline order.

Original languageEnglish
Article number3131
JournalNanomaterials
Volume12
Issue number18
DOIs
Publication statusPublished - Sept 2022

Keywords

  • birefringence
  • cellulose nanocrystals
  • ion exchange
  • ion pairs
  • rheo-PLI
  • rheology

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)

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