Strain hardening in model polymer brushes under shear

The nonlinear dynamic response of polymer melt brushes to large amplitude o scillatory shear is studied using melt state rheology of end-tethered polym er layered-silicate nanocomposites. These model melt brushes exhibit revers ible strain hardening at moderate strain amplitudes, characterized by the p resence of a critical strain amplitude for the transition that is only a fu nction of the interlayer distance (i.e., silicate fraction). These results differ qualitatively from those observed for solvent-filled polymer brushes . A phenomenological explanation based on stretching of already distorted c hains in response to the applied shear and predicted on the space filing re quirements of s melt brush is provided to explain these unique results.