Designing Stress-Adaptive Dense Suspensions Using Dynamic Covalent Chemistry.

Area of Science:

• Materials Science
• Polymer Chemistry
• Rheology

Background:

• Dense suspensions exhibit non-Newtonian behaviors due to adaptable particle-particle contacts under shear.
• Understanding and controlling these stress-adaptive networks are crucial for technological applications.

Purpose of the Study:

• To explore the use of dynamic covalent chemistry to tailor stress-adaptive contact networks in dense suspensions.
• To investigate how tuning the equilibrium constant (K_eq) of dynamic bonds affects rheological properties.

Main Methods:

• Employing a room temperature dynamic thia-Michael bond to link polymer solvent to particles.
• Systematically varying the equilibrium constant (K_eq) to study its effect on suspension rheology.

Main Results:

• Low K_eq resulted in shear thinning behavior.
• High K_eq led to antithixotropy, where viscosity increases with shearing time.
• Proposed mechanism for antithixotropy involves polymer bridging and partial debonding.

Conclusions:

• Dynamic covalent chemistry offers a molecular handle to control suspension rheology with programmable time dependence.
• This approach enables the development of energy-absorbing materials with tunable dissipation properties.
• Materials can switch between different dissipation modalities on demand.