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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
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Crystal-to-Crystal Transition of Ultrasoft Colloids under Shear
J Ruiz-Franco1, J Marakis2,3, N Gnan1,4
1Dip. Di Fisica, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Rome, Italy.
Physical Review Letters
|March 16, 2018
Summary
Shear can induce crystallization in ultrasoft colloidal star polymers near their glass transition. Increasing shear rate drives a direct crystal-to-crystal transition from bcc to fcc structures, bypassing melting.
Area of Science:
- Soft matter physics
- Materials science
- Polymer science
Background:
- Ultrasoft colloids typically vitrify rather than crystallize at high concentrations.
- Controlling colloidal crystallization is crucial for materials design.
Purpose of the Study:
- To investigate the effect of shear on the crystallization of colloidal star polymers.
- To explore the possibility of inducing and controlling crystal-to-crystal transitions.
Main Methods:
- In situ rheo-small-angle-neutron-scattering experiments.
- Numerical simulations of colloidal systems.
- Analysis of structural transitions under varying shear rates.
Main Results:
- Shear was found to facilitate crystallization of colloidal star polymers near the glass transition.
- A direct crystal-to-crystal transition from body-centered cubic (bcc) to face-centered cubic (fcc) structures was observed with increasing shear rate.
- This transition occurred via sudden structural reorganization, without intermediate melting.
Conclusions:
- Shear is a powerful tool to induce and control colloidal crystallization.
- Tailoring colloidal crystallization and crystal-to-crystal transitions is achievable by combining material softness with applied shear.
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