Morphological adjustment determines the properties of cationically polymerized epoxy resins

The morphological adjustment of a cationically polymerized cycloaliphatic epoxy resin is presented. For this purpose, the epoxy resin is polymerized both with a reactive poly(ε-caprolactone) (PCL-diol) and a unreactive one (PCL-diester) leading to a copolymer and a polymer alloy of different morphologies, respectively. Small-angle X-ray scattering (SAXS) shows that the formed nanostructures are the result of the reaction-induced microphase separation (RIMS) mechanism. The activated monomer mechanism (AM) proceeded faster than the activated chain end mechanism (ACE) leading to a preferred integration of PCL-diol into the epoxy network so that segregation is partially inhibited, especially for small polyester contents. It was shown that esterified PCL did not react with the epoxy resin so that it was forced to segregate greatly in the form of spherulitic domains. This was shown by STEM imaging, by the occurrence of crystallinity, as well as by enhanced glass transition temperatures compared to its comparable copolymers