STRAIN EFFECTS ON THERMAL FLUCTUATIONS IN SOFT SOLIDS - BUTTERFLY PATTERNS

We present a phenomenological Landau-de Gennes-type theory of strain effects on concentration fluctuations in <<soft>> elastic two-component solids. Introducing concentration-dependent elastic moduli and a coupling between the strain and concentration fields we find that, for systems which exhibit nearly linear elastic response to large, uniaxially applied strain, there is strong enhancement of thermal fluctuations with wave vectors along the elongation axis. We calculate the structure factor and find that the equal intensity lines produce <<butterfly>> patterns akin to those observed in neutron scattering from deformed rubbers, gels and mixtures of molten polymers.