FIGURE 6 Elastic moduli of a nanoscopic polymeric structure determined from simulations of strain fluctuations. The bulk value is 3 Gpa.

FIGURE 7 Cross-sectional view of the local density (left) and local elastic constant (right) distribution of a model polymeric nanostructure. The density is shown in reduced (Lennard-Jones) units, and the elastic constants are shown as a percentage of the bulk value.

ed uniformly throughout the structure. The local elastic modulus corresponding to the stress that arises upon vertical compression (in the direction normal to the substrate) of the structures is shown on the right. Near the air-polymer interface the material exhibits a gradual softening. Near the polymer-substrate interface the material undergoes a pronounced layering, which gives rise to large local elastic moduli. In the core of the structure, however, the local elastic constants