Electrospinning can produce tissue-engineering scaffolds possessing appropriate strength, biomimetic structure, economic appeal, and biocompatibility. To investigate how microstructural changes could potentially affect adherent mammalian cells, tensile samples were strained to 10, 40, and 80% extension, and adhered to double-sided carbon tape to maintain specific states of strain. While establishing the stress-strain response, we invoked polymer sintering to help verify that the "point bonding" concept is more significant than previously realized at both the macroscopic and microscopic length scales. Sintering successfully established the effects of deliberate, extensive point bonding/localized "notch" generation on mechanical properties and microstructural response without requiring chemical changes within the structure. We also found that fibers experience significant hysteresis in terms of their orientation following exposure to high values of strain. Aligned fibers provide higher strengths (sigma(ave) = 2.8 +/- 0.3 MPa vs. sigma(ave) = 1.29 +/- 0.04 MPa for unaligned fibers) but considerably lower elongation [epsilon(ave) = (30 +/- 2)% vs. epsilon(ave) = (102 +/- 6)%]. Conversely, when strain occurs perpendicular to the aligned fiber direction total strain increases [epsilon(ave) = (188 +/- 6)%] while strength decreases (sigma(ave) = 0.38 +/- 0.01 MPa). Elastic response to low strains appears to estimate ultimate tensile strength. In many ways, electrospun fibers behave similarly to classic interpretations of polymer chains in that when strained in both cases elements can rearrange and translate to align along the direction of loading. (c) 2007 Wiley Periodicals, Inc.