Related Experiment Video
Updated: Jun 11, 2025
09:26
Synthesis and Characterization of Supramolecular Colloids
Published on: April 22, 2016
9.7K
Unveiling the Electrostatically Driven Collapsing and Relaxation of Polyelectrolyte-Colloid Complexes: A Tunable
Swati Mehta1,2, Jitendra Bahadur1,2, Ashwani Kumar1
1Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 4, 2024
Summary
Polyelectrolyte-colloid complexes form collapsed coacervates at high concentrations, then swell. This structural change, driven by electrostatics and the Donnan effect, is key to understanding complex assembly.
Area of Science:
- Materials Science
- Physical Chemistry
- Biophysics
Background:
- Polyelectrolyte-colloid (PEC) complexes are vital in various fields and exhibit complex phase transitions.
- Understanding the electrostatic forces governing PEC assembly is crucial but challenging.
- These complexes mimic intricate biological assemblies, highlighting their significance.
Purpose of the Study:
- To investigate the structural evolution of polyelectrolyte-colloid complexes at varying polyelectrolyte concentrations.
- To elucidate the role of electrostatic interactions and the Donnan effect in PEC phase transitions.
- To characterize the formation and swelling of coacervate structures in a model PEC system.
Main Methods:
- Utilized anionic silica colloids and cationic chitosan as a model system.
- Employed small-angle X-ray/neutron (SAXS/SANS) scattering to analyze structural changes.
- Varied polyelectrolyte (chitosan) concentrations and electrolyte concentrations to observe phase transitions.
Main Results:
- Observed the formation of highly collapsed coacervate structures (volume fraction ~0.62) at elevated polyelectrolyte concentrations (up to 3 wt %).
- Identified swelling of the collapsed assembly at polyelectrolyte concentrations exceeding 3 wt %.
- Demonstrated a linear dependence of critical coacervation concentration (Cs*) on initial colloid concentration.
- Showcased complete coacervate dissolution at electrolyte concentrations above 0.2 M due to charge screening.
Conclusions:
- The structural evolution of PEC complexes is governed by the interplay of electrostatic forces and the Donnan effect.
- Coacervate formation and swelling are concentration-dependent phenomena in PEC systems.
- Electrolyte addition provides insights into charge screening mechanisms and their impact on PEC stability.
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