Multi-Scale Modeling of Ionic Liquid Dispersed Nanocomposites in Epoxy Resin
James A. Throckmorton. and Giuseppe R. Palmese
Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA
Epoxy resins boast impressive rigidity, thermal and electrical resistance, and an easily controlled
casting process. Unmodified, however, such resins are extremely susceptible to crack propogation.
When dispersed in discrete form throughout the thermoset, a less rigid second phase that minimally
disrupts the underlying epoxy matrix can change the nature of the material from a brittle, single-phase
system to a multiphase system with increased fracture toughness.
Nanoparticles, possessing a high surface area to size ratio, are often excellent fillers for such
systems. Depending on their interactions with the epoxy matrix, such particles offer great gains in
material properties at small volume fractions. Recent research by our lab has demonstrated that ionic
liquids can simultaneously disperse such nanoparticles within an epoxy matrix and initiate epoxy cure
polymerization. This dual functionality creates a material with a unique interphase created by the
interactions between the nanoparticles, ionic liquid solvent, and epoxy resin.
This study examines those interactions experimentally and conceptually. Epoxy cures over a
range of nanoparticle and ionic liquid volume fractions are analyzed for glass transition and mechanical
properties. Critical molecular interactions parameters, including kinetic rate constants and diffusion
behavior are analyzed using time-resolved Fourier Transform Infrared Attenuated Total Reflectance
Spectrometry (FTIR-ATR). From these parameters and the properties of the cured material, multi-scale
models are developed to explore the interphase between the nanoparticle and the epoxy matrix, the
relationship between physical properties at the continuum and micro-scale, the degree of cross-linking
as a function of kinetic and diffusion parameters, and the time and temperature dependent degree of
cure.