Modulating the chiral nanoarchitecture of cellulose nanocrystals through interaction with salts and polymer

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Abstract

Hypothesis: The conditions to allow self-assembly of cellulose nanocrystal (CNC) suspensions into chiral nematic structures are based on aspect ratio, surface charge density and a balance between repulsive and attractive forces between CNC particles. Experiments: Three types of systems were characterized in suspensions and subsequently in their solid dried films: 1) neat water dialyzed CNC, 2) CNC combined with polyethylene glycol(PEG) (CNC/PEG), and 3) CNC with added salt (CNC/Salt). All suspensions were characterized by polarized optical microscope (POM) and small angle X-ray scattering (SAXS), while the resultant dried films were analyzed by reflectance spectrometer, scanning electron microscope (SEM) and SAXS. Findings: The presence of chiral nematic (CN*) structures was not observed in dialyzed aqueous suspensions of CNC during water evaporation. By introducing salts or a non-adsorbing polymer, chirality was apparent in both suspensions and films. The interaxial angle between CNC rods increased when the suspensions of CNC/PEG and CNC/salt were dried to solid films. The angle was found to be dependent on both species of ions and ionic strength, while the inter-particle distance was only related to the salt concentration, as explained in terms of interaction energies. The CNC suspensions/film chirality can be modulated by controlling the colloidal forces.

Original languageEnglish
Pages (from-to)207-217
Number of pages11
JournalJournal of Colloid and Interface Science
Volume613
DOIs
Publication statusPublished - May 2022

Keywords

  • Achiral and chiral nematic phase
  • Cellulose Nanocrystal (CNC)
  • Chirality
  • Inorganic salts
  • Polyethylene glycol (PEG)
  • Self-assembly

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