Study of microstructure formation in epoxy based systems using small angle neutron scattering

Structural/multifunctional electrolytes (SE) are an essential part of novel types of energy storage devices, structural supercapacitors and structural batteries. They are able to perform two functions simultaneously, conduct ions and withstand mechanical load. The most promising SEs consist of two independent phases, i.e. have a bicontinuous structure. Here the formation of such structures is discussed using an epoxy cured in the presence of ionic liquid, as an example. Using small angle neutron scattering (SANS) structural changes were monitored as a function of curing time. It was necessary to use two models to fit the SANS data, at short and long curing times, indicating evolution of structural features at different length scales, with curing. Increasing temperature leads to significant increase in the reaction rate but the same trend is observed in the SANS patterns with curing time. Independently of the curing temperature, polymer clusters, in the range 25-75 nm, size is depending on the temperature, form during the early stages. As curing progresses, the number of clusters first increases and then a decrease is observed and accompanied by evolution of a more complex structure. Addition of a multifunctional block copolymer resulted in a significant change of the curing process at longer curing times.