Telechelic ionomers studied by light scattering and dynamic mechanical measurements

The formation of a transient network by sulfonato polyisoprene and sulfonato polystyrene in toluene is studied using static and dynamic light scattering and dynamic mechanical analysis. It is shown that at low concentrations aggregates are formed with increasing molar mass and polydispersity as the polymer concentration is increased. Above a certain concentration well below the overlap concentration of the polymer chains (C*), a transient network is formed. This is characterised by a plateau modulus at high frequencies and a relatively narrow viscoelastic relaxation time distribution. The intensity auto-correlation function of the transient network shows two relaxational modes: a relatively fast diffusional mode close to the co-operative diffusional mode of semidilute solutions of the unfunctionalised polymers, and a slow broader mode which becomes independent of the scattering angle at concentrations close to C*. The relation between this slow mode and the viscoelastic relaxation is discussed.