Confinement-induced super strong PS/MWNT composite nanofibers

Shear Modulation Force Microscopy (SMFM) together with the Atomic Force Microscopy (AFM) based three-point bending technique were used to measure the mechanical properties of electrospun polymers and polymer nanocomposite fibers. Both techniques showed that the moduli of the fibers increased significantly with decreasing fiber diameter. We attributed this enhancement to the orientation of polymer chains which occurs during the electrospinning process. We then predicted, and confirmed experimentally, that the phenomenon scales with R_g rather than with the absolute fiber diameter and can propagate radially for large distances (∼20R_g) into the fiber interior. The inclusion of nanotubes into the fibers further enhanced the orientation by introducing additional surfaces. The additional increase in modulus (more than an order of magnitude) could then be explained by the same model and scaled on a universal curve.