Rheology of disordered lamellar phases

Sreejith Sukumaran1,^2,3, Alok K. R. Paul², Sriram Ramaswamy¹, Prabhu R. Nott² and V.Kumaran²

¹ Department of Physics & ² Department of Chemical Engineering, Indian Institute of Science, Bangalore 560 012, India

³ Poornaprajna Institute of Scientific Research, Bangalore 560 080, India

We explain the rheological properties of disordered smectics using a theory of polydomain smectics and with lattice Boltzmann (LB) simulations of oscillatory rheological experiments. A proper averaging of the smectic stress field has two contributions: the first from assuming a constant stress field and the second, from a constant strain field. This computation of the complex dynamical modulus yields a zero frequency elastic shear modulus G0 and also !1/2 behavior at intermediate frequencies. The LB simulations indicate the plateau regime with a constant elastic modulus. Interestingly, a fourth regime due to smectic permeation is shown to exist at frequencies less than a critical frequency.