Polymer Solution Entanglement Influences the Mechanical Properties of the Resultant Electrospun Fibers

Electrospun fibers have a range of applications that rely on specific mechanical properties for optimal function. In this study, we examined the diameter-independent relationship between polymer solution entanglement and the mechanical properties of individual electrospun polycaprolactone fibers. Molecular weights of 35 kDa, 45 kDa, and 80 kDa were used at various concentrations to produce smooth fibers from polymer solutions across a range of entanglement molecular weights. Fibers were pulled until failure using atomic force microscopy, and their mechanical properties were determined. Because of the strong diameter dependence, we selected fibers within a limited range to compare initial modulus, rupture stress, and toughness. Within the same polymer molecular weight, the initial modulus, extensibility, rupture stress, and toughness increased with greater polymer solution entanglement. However, when comparing across polymer molecular weights, we observed that changing molecular weight altered extensibility to a greater degree than adjusting entanglement. The fibers produced from 35 kDa PCL had significantly smaller diameters, around 100 nm, than those produced at higher molecular weights, and their mechanical properties did not change with entanglement. These results suggest that fiber mechanics can be controlled and tailored to specific applications through diameter-independent means by altering entanglement and polymer molecular weight.