Size dependent mechanical properties of electrospun polymer fibers from a composite structure

The elastic modulus of individual electrospun polyvinyl-alcohol (PVA) fibers was measured using atomic force microscopy (AFM) based bending tests. Results indicated an increase in the elastic modulus as the fiber diameter decreased. Consideration of electrospun fibers as a composite structure consisting of a shell region of aligned polymer chains surrounding a bulk-like isotropic core was analytically modeled and showed good agreement with the experimental data. Phase contrast AFM imaging of focused ion beam (FIB) prepared PVA fiber cross-sections provided a method of observing the shell–core structure directly and supported the model proposed. These findings indicate the potential for considerable polymer chain alignment for the production of high performance fibers using electrospinning methods.