Effect of copolymer sequence on local viscoelastic properties in spherical coordinates around a nanoparticle

A polymer nanocomposite consisting of a spherical nanoparticle surrounded by coarse-grained polymer chains is simulated. Two monomer types make up the polymers, differing only in their interactions with the nanoparticle. All atomic stress fluctuations are measured, converted to spherical coordinates centered around the nanoparticle, and used to estimate the local stress autocorrelation as a function of distance from the nanoparticle. The local stress autocorrelation is substituted into the relationship between the bulk stress autocorrelation and bulk dynamic modulus, analyzed in both radial shear and tangential shear geometries. The result is then treated as an estimate of the local dynamic modulus. This allows us to separate radial and tangential effects on overall dynamic modulus as a function of distance from the nanoparticle for multiple copolymer sequences. Unlike the direction-independent results, short block length copolymer sequences exhibit a non-monotonic progression of the magnitude of the tan( ) (hysteresis) peak over distance to the nanoparticle, suggesting that adjusting copolymer sequence could significantly control observed nanocomposite dynamics.National Science Foundation Grant No. 1454343. Exploratory Materials Research Grant from the OSU Materials Research Seed Grant Program of the Institutefor Materials Research (IMR) at The Ohio State University. Ohio Supercomputing Center.No embargoAcademic Major: Chemical Engineerin