Small angle neutron scattering and dynamic mechanical thermal analysis of dimethacrylate/epoxy IPNs

Dynamic mechanical thermal analysis (DMTA) and small angle neutron scattering (SANS) have been performed on a number of dimethacrylate (or mono-methacrylate)/diepoxy (or mono-epoxy) interpenetrating polymer networks (IPNs) and semi-IPNs to probe their phase structure. The DMTA behaviour ranged from IPNs that produce one tan δ peak, indicative of a single-phase system, to systems that are clearly phase separated, showing two tan δ peaks. These results were correlated with the SANS data – samples that showed two tan δ peaks also showed scattering in the SANS spectrum. Fitting of the scattering data to the Debye–Bueche scattering model for a phase-separated structure gave a scale to this phase separation of about 180Å. DMTA analysis of the rubbery region of the semi-IPNs revealed that they either had a co-continuous morphology or a matrix phase that was crosslinked.