Structural and mechanical characterization at small scales

We are equipped with static and dynamic light scattering setups to study the structural properties of soft materials during transformation processes.

Static Light Scattering (SALS)

The small-angle light scattering (SALS) setup was developed at LRP and can be coupled with shear, filtration, or elongational flow cells, allowing the simultaneous application of external fields during the structural characterization of the sample.

It consists of a 2 mW He-Ne laser beam with a wavelength of 632.8 nm and a Fresnel lens to collect the scattered light (Piau et al., 1999). The detector is an Allied Vision monochrome digital camera (AV MAKO G-419B POE) with a CMOS sensor (2048 × 2048 pixels, 11.3 × 11.3 mm²). Image processing is performed using a video system and dedicated software (Vimba Matlab), which allows regrouping and averaging of scattered intensity according to different configurations (radial, angular sectors, annular) with the SAXS Utilities software (Sztucki and Narayanan, 2007). Scattering spectra are recorded by the camera and video system throughout the experiment. Light scattering measurements cover a wave vector (q) range from 2 × 10⁻⁴ to 4 × 10⁻³ nm⁻¹.

In the example illustrated below, a shear flow cell consists of a rectangular quartz channel, as shown in the figure. The shear cell is coupled to a syringe pump to vary the flow rate Q, and thus the shear rate inside the channel, typically ranging from 10⁻² to 10³ s⁻¹.

References 

Piau, J.M., Dorget, M., Palierne, J.F., Shear elasticity and yield stress of silica–silicone physical gels: Fractal approach, J. Rheol., 43, 305–314 (1999). 

Pignon, F., Piau, J.M. and Magnin, A., Structure and pertinent length scale of a discotic clay gel, Physical Review Letters, 76, 4857-4860 (1996). https://link.aps.org/doi/10.1103/PhysRevLett.76.4857

Pignon, F., Magnin, A. and Piau, J.M., Butterfly light scattering pattern and rheology of a sheared thixotropic clay gel, Physical Review Letters, 79, 4689-4692 (1997). https://link.aps.org/doi/10.1103/PhysRevLett.79.4689

Pignon, F., Magnin, A., Piau, J.M., Cabane, B., Lindner, P. and Diat, O., A yield stress thixotropic clay suspension: investigations of structure by light, neutron and x-ray scattering, Physical Review E, 56, 3281-3289 (1997). https://link.aps.org/doi/10.1103/PhysRevE.56.3281

Pignon, F., Magnin, A. and Piau, J.M., Thixotropic behavior of clay dispersions: combinations of scattering and rheometric techniques, Journal of Rheology, 42, 1349-1373 (1998). https://doi.org/10.1122/1.2079267

Saint-Michel F., Pignon F. and Magnin A., Fractal behavior and scaling law of hydrophobic silica in polyol, Journal of Colloid and Interface Science, 267(2) 314-319 (2003). 

de Bruyn J.R., Pignon F., Tsabet E. and Magnin A. Micron-scale origin of the shear-induced structure in Laponite–poly(ethylene oxide) dispersions, Rheologica Acta, 47, 63-73 (2008). 

Fernández V.A., Tepale N., Alvarez J.G., Pérez-López J.H., Macías E.R., Bautista F., Pignon F., Rharbi Y., Gámez-Corrales R., Manero O., Puig J.E. and Soltero J.F. A., Rheology of the pluronic P103/water system in the semidilute regime: evidence of non-equilibrium critical behavior, Journal of Colloid and Interface Science, 336, 842-849 (2009). 

Pignon, F., Challamel, M., De Geyer, A., Elchamaa, M., Semeraro, E.F., Hengl, N., Jean, B., Putaux, J.L., Gicquel, E., Bras, J., Prevost, S., Sztucki, M., Narayanan, T., Djeridi, H., Breakdown and buildup mechanisms of cellulose nanocrystal suspensions under shear and upon relaxation probed by SAXS and SALS, Carbohydrate Polymers, 260, 117751 (2021). 

Bauland J., Andrieux V., Pignon F., Frath D., Bucher C., Gibaud T., Viologen-based supramolecular crystal gels: gelation kinetics and sensitivity to temperature, Soft Matter, 20, 8278, (2024).

Mandin S., Metilli L., Karrouch M.,Blésès D., Lancelon-Pin C., Sailler P., Chèvremont W., Paineau E., Putaux J.L., Hengl N., Jean B., and  Pignon F., Multiscale study of the chiral self-assembly of cellulose nanocrystals during the frontal ultrafiltration process, Nanoscale, 16, 19100, (2024). https://doi.org/10.1039/D4NR02840F

Sztucki M., Narayanan T., Development of an ultra-small-angle X-ray scattering instrument for probing the microstructure and the dynamics of soft matter, J. Appl. Cryst., 40, 459–462 (2007). 

Son, Y.  Determination of shear viscosity and shear rate from pressure drop, and flow rate relationship in a rectangular channel, Polymer, 48, 632–637 (2007).