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Structure and Dynamics of Hybrid Colloid-Polyelectrolyte Coacervates
Artem M Rumyantsev1, Oleg V Borisov2, Juan J de Pablo1
1Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
Macromolecules
|March 6, 2023
Summary
We developed a theory for hybrid coacervates made of polymers and charged colloids. The theory explains coacervate structure and dynamics, showing how colloid charge influences properties and predicting diffusion coefficients.
Area of Science:
- Soft Matter Physics
- Polymer Science
- Colloid Science
Background:
- Complex coacervates are liquid-liquid phase-separated materials formed from oppositely charged polymers and/or particles.
- Hybrid coacervates, incorporating spherical colloids like proteins or nanoparticles, present unique structural and dynamic properties.
- Understanding the interplay between colloid properties and polyelectrolyte behavior is crucial for controlling coacervate formation and function.
Purpose of the Study:
- To develop a comprehensive scaling theory for the structure and dynamics of hybrid complex coacervates.
- To elucidate the roles of adsorption strength, shell thickness-to-radius ratio (H/R), and colloid charge (Q) in dictating coacervate regimes.
- To predict the influence of colloid charge and radius on coacervate density, osmotic properties, surface tension, and colloidal dynamics.
Main Methods:
- Development of a scaling theory based on polymer adsorption onto spherical colloidal particles.
- Construction of a scaling diagram mapping coacervate regimes as a function of colloid charge and radius in different solvent conditions (Θ and athermal).
- Analysis of the dependence of coacervate density, osmotic moduli, surface tension, and viscosity on colloid charge and solvent type.
Main Results:
- Hybrid coacervates form finite-size complexes at low concentrations, transitioning to macroscopic phase separation above a threshold concentration.
- Coacervate structure is governed by adsorption strength and the H/R ratio; high colloid charges lead to thick shells dominated by polyelectrolytes.
- Hybrid coacervate density exceeds PE-PE counterparts and increases with Q; viscosity and diffusion coefficients show distinct Q-dependencies for different solvents.
Conclusions:
- The developed scaling theory accurately describes hybrid coacervate formation and properties, consistent with experimental observations for systems like GFP-RNA coacervates.
- Colloid charge (Q) significantly impacts coacervate threshold concentration and dynamics, with viscosity scaling non-linearly with Q.
- The theory provides a framework for predicting and controlling the behavior of hybrid coacervates in various applications.
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