Analysis of decoupling of DC conductivity and structural relaxation time in epoxies with different molecular topology

Dielectric measurements of 4,4′-methylenebis (N,N-diglicydilaniline) (MBDGA) have been carried out along both pressure and temperature pathways. The phenomenon of decoupling between the DC-conductivity and the structural (α-) relaxation time has been studied. We found that the exponent s in the fractional Debye–Stokes–Einstein relation is both temperature and pressure independent, and its value can be determined from the ratio of activation volumes for the DC-conductivity relaxation and the structural relaxation process, respectively. The results for MBDGA have been compared with results previously obtained for similar epoxies, i.e., N,N-diglycidylaniline and N,N-diglycidyl-4-glycidyloxyaniline. A correlation between the molecular size and the fractional exponent has been established.