(5bd) Nanoscale Structures - What's Necessary to Make It Smaller?

Applications of nanometer size structures are a subject of considerable theoretical and experimental study. Photonic nanocrystals, nanoparticles (carbon nanotubes, fullerenes, POSS) used for the creation of nanocomposites or for catalysis, ultra thin films that are etched giving patterned surfaces via nanolithography techniques are some examples of nanostructures. Our study is focused on the area of nanocomposites and block copolymers.

Particulate fillers, such as silica and carbon black, are widely used in polymer industry to improve material properties. Because of the increasing technological applications a large extent of research has been focusing on nanocomposite properties. The interaction zone and the bridge formation hypotheses are often used to explain the changes in mechanical properties that accompany the addition of nanoparticles to a polymer matrix. Advanced Monte Carlo techniques involving chain connectivity algorithms are used and attractive polymer particle interactions are considered. The formation of a stiff glassy layer is apparent in the vicinity of the nanoparticles validating the interaction zone theory. Calculation of chain bridges between particles is compared to chain length to examine the bridge formation hypotheses. The distribution of local moduli and the correlation of the non affine displacements give interesting results on the inhomogeneity and the fragility of the nanocomposite and the unfilled polymer systems.

The possibility of using self-assembled films of block polymers as templates to fabricate nanoscale structures for devices has attracted great attention towards this class of materials. A technique for mapping an exact experimental system to a bead spring model is presented. The beauty of this technique is that it is simple to apply and captures the behavior of the specific block copolymer system under study. In our work this mapping technique is utilized in conjunction with a Monte Carlo (MC) algorithm to perform simulations on block copolymer systems and blends of block copolymer with its corresponding homopolymers. The microphase separation is investigated on both unpatterned and patterned surfaces.