The temperature dependence of proton NMR relaxation times T1 and T1rho has been studied for crosslinked films based on oligo(ethylene glycol) methacrylate containing LiCF3SO3 and correlated to ionic conductivity measurements. The NMR relaxation times and the ionic mobility are strongly influenced by polymer segmental motion. The influence of crosslink density and plasticizer is discussed in terms of a self-contribution of the polymer matrix to the ionic conductivity. A significant influence of the PEO-sequences in the O(EG)(n)DMA network to the conductivity behaviour of the gel electrolytes investigated was observed for n greater-than-or-equal-to 9.