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Seminar: Equilibrium self-assembly and out-of-equilibrium dynamics of nanoboards
Wednesday, 19. January 2022, 12:00
Contact Jose Miguel Mancheño Gómez

Colloidal cuboids have an especially rich phase behaviour and the potential to self-assemble into biaxial nematic liquid crystals.

Colloidal cuboids have an especially rich phase behaviour and the potential to self-assemble into biaxial nematic (NB) liquid crystals. Over the last few decades, several theoretical works have predicted the existence of a wide region of the phase diagram where biaxial nematics would be stable, but imposed rather strong constraints on the particle rotational degrees of freedom, which artificially enhance the stability of the NB phase. In this talk, we present molecular simulation results that clarify the relevance of fully unfreezing the rotational degrees of freedom to accurately determine the range of stability of the NB phase. Our results show that only a large size dispersity or the presence of an external field can induce the formation of thermodynamically stable biaxial nematics. In particular, surprisingly weak field strengths are able to spark a uniaxial-to-biaxial phase transition at the self-dual shape, where prolate and oblate geometries fuse into one, suggesting a path to exploit low-energy uniaxial-to-biaxial order switching. Motivated by this scenario, we have also simulated the unsteady state reorientation dynamics when a field is applied (uniaxial-to-biaxial switching) and then removed (biaxial-to-uniaxial switching). We detected a strong correlation between the response time, being the time taken for the system to reorient, and particle anisotropy, which spans from rod-like to plate-like geometries. Interestingly, self-dual shaped cuboids, theoretically considered as the most suitable to promote phase biaxiality for being exactly in between prolate and oblate particles, exhibit surprisingly slow response times.

Fecha del seminario: 19/01/2022 12:00

Lugar del seminario: Seminario online

Ponente del seminario: Alessandro Patti

Abstract

 

Location Online