Effects of entrapment on spherulite morphology and growth kinetics in poly(ethylene oxide)/epoxy networks

Poly(ethylene oxide) (PEO) is known to be miscible with diglycidylether bisphenol-A (DGEBA)/4,4′-diamino diphenylsulfone (DDS) epoxy system before and after cure. As PEO starts to crystallize in the miscible mixtures (either uncured liquid or cured network), entrapment and interactions between the species can play an important role on the growth kinetic and lamellar/spherulitic morphology. Thermal analysis, growth kinetics analysis, and morphology characterization were performed on a PEO-epoxy system, and the results were found to be useful in providing critical interpretation. In general, entrapment between the growing species and epoxy/DDS was found to be more extensive in the uncured system. In addition, the interactions between the species are different before and after cure. The interactions between PEO and epoxy/DDS become less in the cured networks. The morphology and growth kinetics of the PEO crystals was in turn affected by the contents and chemical structures (functional group, molecular weight, crosslink, etc.) of the amorphous diluents (i.e. epoxy/DDS). The morphology of PEO in the cured PEO/epoxy system is quite similar to that observed in the neat PEO. This study attempted to offer a molecular microscopic view on commonly observed depression of growth kinetics of semicrystalline polymers in the presence of a diluent (an amorphous polymer or other non-crystallizing species)