Polarised microscopy is shown to be a powerful alternative to light scattering for the determination of the viscoelasticity of aligned nematic liquid crystals. We perform experiments in a wide range of temperatures by using an adapted version of the recently introduced differential dynamic microscopy technique, which enables us to extract scattering information directly from the microscope images. A dynamic analysis of the images acquired in different geometries provides the splay, twist and bend viscoelastic ratios. A static analysis allows a successful determination of the bend elastic constant. All our results are in excellent agreement with those obtained with the far more time-consuming depolarised light scattering techniques. Remarkably, a noteworthy extension of the investigated temperature-range is observed, owing to the lower sensitivity of microscopy to multiple scattered light. Moreover, we show that the unique space-resolving capacities of our method enable us to investigate nematics in the presence of spatial disorder, where traditional light scattering fails. Our findings demonstrate that the proposed scattering-with-images approach provides a space-resolved probe of the local sample properties, applicable also to other optically anisotropic soft materials.
Viscoelasticity of nematic liquid crystals at a glance / F. Giavazzi, S. Crotti, A. Speciale, F. Serra, G. Zanchetta, V. Trappe, M. Buscaglia, T. Bellini, R. Cerbino. - In: SOFT MATTER. - ISSN 1744-683X. - 10:22(2014 Jun 14), pp. 3938-3949.
|Titolo:||Viscoelasticity of nematic liquid crystals at a glance|
GIAVAZZI, FABIO (Corresponding)
BELLINI, TOMMASO GIOVANNI (Penultimo)
CERBINO, ROBERTO (Ultimo)
|Parole Chiave:||differential dynamic microscopy; coupled-device camera; light-scattering|
|Settore Scientifico Disciplinare:||Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)|
Settore FIS/03 - Fisica della Materia
|Progetto:||Anisotropies and non equilibrium in soft matter: routes to the self assembly of advanced materials|
|Data di pubblicazione:||14-giu-2014|
|Data ahead of print / Data di stampa:||4-mag-2014|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1039/c4sm00145a|
|Appare nelle tipologie:||01 - Articolo su periodico|