Poster Presentation Australian & New Zealand Society of Magnetic Resonance Conference 2017

Rheo-NMR and Rheo-SALS using Large Amplitude Oscillatory Shear for the Study of Complex Fluids (#108)

Stefan Kuczera 1 2 , Luigi Gentile 2 3 , Timothy I Brox 1 , Ulf Olsson 2 , Claudia Schmidt 4 , Petrik Galvosas 1
  1. Victoria University of Wellington, Wellington, New Zealand
  2. Division of Physical Chemistry, Lund University, Lund, Sweden
  3. Department of Chemistry and Chemical Technologies, University of Calabria, Calabria, Italy
  4. Department of Chemistry, University of Paderborn, Paderborn, Germany

Rheo-NMR has existed as a tool for studying fluids under mechanical deformation for nearly 25 years [1,2]. It provides spatially and temporally resolved maps of NMR spectra, intrinsic NMR parameters (e.g. relaxation times) or motion (e.g. diffusion or flow). Likewise, Rheo-SALS (Small Angle Light Scattering) is an advanced rheological method which can be used to monitor microscopic changes in the sample due to deformation. Characteristic scattering patterns arise from scattered light intensity as a function of the wave vector, yielding information on microscopic shapes and structures [3]. Both, Rheo-NMR and Rheo-SALS have been established as complementary techniques to conventional rheological measurements.

Shear-induced transformations between oriented planar lamellae and multilamellar vesicles (MLVs) due to steady shear have been studied in the past by Rheo-NMR [4,5]. However, recent advances in Rheo-NMR hardware allow for the application of Large Amplitude Oscillatory Shear (LAOS) deformations in high field NMR magnets for the first time [6]. Here we report on the combined use of Rheo-NMR and Rheo-SALS to study the formation of multilamellar vesicles (MLVs) in a lyotropic surfactant system (C10E3/water) using LAOS. For the range of investigated strain amplitudes (10-50) and frequencies (1 rad/s, 2 rad/s) MLV formation is observed in all NMR and most SALS cases. For LAOS it was found that the MLV size mainly depends on the frequency as opposed to previous steady shear experiments where the shear rate was the controlling parameter [7]. Additionally, the onset of MLV formation using LAOS was primarily dependent on the applied shear amplitude. Furthermore, the process of onion formation appears to be retarded during LAOS as compared to the steady shear case.

  1. Nakatani, A. et al. Macromolecules, 23 2686 (1990)
  2. Callaghan, P.T., Rep. Prog. Phys., 62 599 (1999)
  3. Samuels, J., Polym. Sci. 9, 1971, 2165
  4. Medronho, B. et al., Soft Matter 7 4938-4947 (2011)
  5. Medronho, B. et al., Z. Phys. Chem. 226 1293-1313 (2012)
  6. T.I. Brox and P. Galvosas, NZ Patent 629,361 (2016)
  7. Medronho, B. et al., Langmuir 26 1477–1481 (2010)