Properties of Polymer Nanocomposites
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Victor Pryamitsynvictor@che.utexas.edu Office: CPE 3.402 Phone: 512-471-6754 |
Self-organization of nanoparticles in polymeric matrixes
It is easy to understand the self-assembly of particles with anisotropic shapes or interactions (for example, cobalt nanoparticles or proteins) into highly extended structures. However, there is no experimentally established strategy for creating a range of anisotropic structures from common spherical nanoparticles. We demonstrate that spherical nanoparticles uniformly grafted with macromolecules ('nanoparticle amphiphiles') robustly self-assemble into a variety of anisotropic superstructures when they are dispersed in the corresponding homopolymer matrix. Theory and simulations suggest that this self-assembly reflects a balance between the energy gain when particle cores approach and the entropy of distorting the grafted polymers. The effectively directional nature of the particle interactions is thus a many-body emergent property. Experiments demonstrate that this approach to nanoparticle self-assembly enables considerable control for the creation of polymer nanocomposites with enhanced mechanical properties. Grafted nanoparticles are thus versatile building blocks for creating tunable and functional particle superstructures with significant practical applications.
Dynamical properties of nanorods suspensions
We have been developing a new computer simulation method to simulate the dynamical and rheological properties of colloid suspensions of in a variety of complex fluids. We first present the results of its generalization to the dynamics and linear rheological properties of dilute, semidilute and concentrated rods suspensions in a simple fluid. Subsequently, we use this method to characterize the mobility and diffusive dynamics of nanoscale spheres in rod matrices, while paying special attention to the length scales of the fluid which characterize the hydrodynamic screening and overall viscous motion. These results my give us the insight into the dynamics of the diffusion processes in the cellular cytoskeleton.
Theoretical analysis of dispersing of aggregated nanorods in presence of shear flow and AC electric/magnetic fields
Efficient dispersion of nanotubes in polymeric matrices is a critical problem confronting the development of modern polymer nanocomposites. The nanotube-nanotube interactions usually promote aggregation, which also depends on factors such as the chemical makeup of the polymer matrix and the size of nanotubes. High intensity mechanical mixing such shear pulverization is commonly used for dispesion of nanotubes. The main disadvantage of such processes is the degradation of the polymer matrix, which may downgrade the final properties of PNC's. In this work, we theoretically explore a novel strategy to reduce the shear stresses required for dispersion of rodlike fillers. We found that simultaneous applications shear flow and AC electric field oriented at an angle to each other may cause rotational instabilities of the rods suspension and lead to the dispersion of the rods. We demonstrate this idea through Brownian dynamics simulations of aggregating nanorods and a complementary theoretical analysis. Our results suggest that an optimal dispersion may be achieved at an shear-E field orientation of β=-45o with an optimal amplitude of AC electric field which is proportional to the rotation Peclet number of nanorods suspension.
