Upon heating above its melting temperature at 195 degrees C, 2-(4-hydroxyphenyl)-1,3-oxazoline (HPO) was polymerized thermally in melt phase within a few minutes to produce a polymer with etheramide and N-4-hydroxybenzoyl-ethyleneimine repeat units. Polymerization in solution afforded only oligomers with 93% etheramide structure after several hours. Reactive blending, combining 2-phenyl-1,3-oxazoline (PO) grafting with in-situ HPO thermal polymerization in poly(ethene-co-methacrylic acid), was the key to novel self-reinforced multiphase ethene copolymer blends containing spherical dispersed poly(HPO) microphases. Poly(HPO) microstructures, blend morphologies, thermal and mechanical properties were investigated.