Dynamic Viscoelasticity in Polyelectrolyte Multilayers: Nanodamping

We report on the time-dependent viscoelastic response of nanoblended films of a polyelectrolyte complex prepared by the multilayering method. The ion-pairing interactions within polyelectrolyte multilayers (PEMUs) are reversibly broken by adding salt to the electrolyte in which the PEMU is immersed. Thus, the bulk modulus of these ultrathin films may be regulated without changing temperature. We have measured surprisingly effective mechanical damping exhibited by PEMUs. Compared to other hydrogel damping materials such as articular bovine cartilage and polyethyleneoxide−terephtalate/polybutylene−terephtalate networks, PEMUs provided enhancement in damping properties over the frequency range of 0.3−10 Hz. This was obtained when the multilayer dry thickness was orders of magnitude less than that of the hydrogels. The mechanism for enhanced damping may be related to the high proportion of ladder-like ion pairing between complexed polyelectrolytes.