We propose a continuum model for the dynamics of particles in polymer matrices which encompasses arbitrary size ratios of the polymer and particle. We present analytical and computer simulation results for the mobility of the particles and the viscosity of the suspension for the case of unentangled polymer melts. Our results indicate strong dependencies of the particle mobility upon the polymer-particle size ratios and much reduced intrinsic viscosities for the suspensions. These predictions rationalize some recent experimental observations on the dynamics of nanoparticles in polymer melts.

We apply a recently proposed multiscale simulation approach to study the dynamical properties of polymer blend interfaces. We use this approach to study the influence of the bulk rheological properties of the polymer blend components upon the slip at unentangled polymer interfaces. Our numerical results agree quite well with the predictions from scaling approaches and phenomenological theories. Moreover, these results also provide a microscopic explanation of the negatively deviating viscosities of polymer blends. We also present results elucidating the slip suppressing influence of block copolymer compatibilizers. Our results suggest that even trace fractions of compatibilizers can suppress slip at polymer interfaces. We study the influences of the molecular weight of the block copolymer and the coverage of block copolymers upon the dynamical properties of polymer blend interfaces, and we suggest some effects that might account for the effect of compatibilizers in the suppression of coalescence during polymer blending.

We present a study of flow-induced phase transitions in microemulsion phases of ternary polymer blends. The results match qualitatively with the recent experimental observations on such systems but differ from the behavior expected and observed in the analogous system of surfactants. We rationalize this contrast from a molecular viewpoint suggesting that the interplay between polymer chain conformations and their flow deformations can lead to novel flow effects upon the phase, structural, and rheological behavior of multicomponent polymer systems.

We use a multiscale Brownian dynamics simulation approach to study the influence of block copolymer compatibilizers upon the dynamics of a nanoscale polymer droplet in a matrix of another polymer. The present study focuses on the influence of the physical characteristics of the copolymer, viz. its coverage and chain lengths upon the droplet deformation characteristics and the rheological properties of the polymer blend system. At a fixed chain length, the copolymer coverage is found to affect the droplet deformation in a nonmonotonic manner as a function of the capillary number, while it increases monotonically with an increase in the copolymer chain length at a fixed coverage. We identify the interplay between interfacial tension reduction, bending modulus enhancement, and Marangoni stresses as responsible for the preceding characteristics. We also study the rheological effects arising from the presence of block copolymers. Our results suggest increased shear thinning with either increasing the copolymer coverage or the copolymer chain lengths. Moreover, the normal stresses of the mixture are dominated by the inherent normal stresses of the matrix and the droplet phases. The rheological results are rationalized by invoking the interplay between deformation characteristics and the dynamical effects of block copolymers at polymer blend interfaces.

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