Solutions of alpha,omega-sodium sulfonatopolyisoprene (alpha,omega NaPIPS) in toluene are studied using static and dynamic light scattering and dynamic mechanical analysis. At concentrations above 4 g/L, which is well below the overlap concentration of the polymer chains (C*), a transient network is formed characterized by a plateau modulus at high frequencies and a relatively narrow viscoelastic relaxation time distribution. The intensity autocorrelation 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 unfunctionalized polymers and a slow broader mode which becomes independent of the scattering angle at a concentrations close to C*. The relation between this slow mode and the viscoelastic relaxation is discussed. Both the slow mode and the viscoelastic relaxation processes have an Arrhenius temperature dependence with the same activation energy, E(a) = 25 kJ/mol.