NONLINEAR RHEOLOGY FOR THREAD-LIKE MICELLES OF TETRAETHYLAMMONIUM PERFLUOROOCTYL SULFONATE

Nonlinear rheological features were investigated for an aqueous soluti on of tetraethylammonium perfluorooctyl sulfonate (C8F17SO3-N+(C2H5)(4 ); abbreviated as FOSTEA). In the solution (c=0.045 mol/l; 28.3 g/l), spherical micelles of FOSTEA were connected with each other to form th reads of pearl-necklace shape. These threads were further organized in to a transient network to exhibit linear relaxation characteristic of living polymers, single-mode terminal relaxation widely separated from faster relaxation processes. Nonlinear relaxation experiments against large step-strains gamma(less than or equal to 8) revealed that the t erminal relaxation mode had a gamma-insensitive relaxation time but it s relaxation intensity exhibited significant damping (much stronger th an that for entangled polymers). In contrast, the relaxation time and intensity for the fast relaxation modes first increased and then decre ased with increasing gamma. Under shear flow, the FOSTEA threads exhib ited strong thinning of the viscosity. These nonlinear features of the FOSTEA threads were compared with those of other threadlike micelles, analyzed on the basis of an empirically introduced constitutive equat ion, and discussed in relation to strain/low-induced scission of the l iving threads.