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Abstract：
Electrospun fibers range in size from nanometers to micrometers and have a multitude of potential applications that depend upon their morphology and mechanics. In this paper, we investigate the effect of polymer solution entanglement on the mechanical properties of individual electrospun polycaprolactone (PCL) fibers. Multiple concentrations of PCL, a biocompatible polymer, were dissolved in a minimum toxicity solvent composed of acetic acid and formic acid. The number of entanglements per polymer (ne) in solution was calculated using the polymer volume fraction, and the resultant electrospun fiber morphology and mechanics were measured. Consistent electrospinning of smooth fibers was achieved for solutions with ne ranging from 3.8 to 4.9, and the corresponding concentration of 13 g/dL to 17 g/dL PCL. The initial modulus of the resultant fibers did not depend upon polymer entanglement. However, the examination of fiber mechanics at higher strains, performed via lateral force atomic force microscopy (AFM), revealed differences among the fibers formed at various concentrations. Average fiber extensibility increased by 35% as the polymer entanglement number increased from a 3.8 ne solution to a 4.9 ne solution. All PCL fibers displayed strain-hardening behavior. On average, the stress increased with strain to the second power. Therefore, the larger extensibilities at higher ne also led to a more than double increase in fiber strength. Our results support the role of polymer entanglement in the mechanical properties of electrospun fiber at large strains.
摘要：
静电纺丝纤维的尺寸范围从纳米到微米，并且具有许多潜在的应用，这取决于它们的形态和力学。在本文中,我们研究了聚合物溶液缠结对单个电纺聚己内酯（PCL）纤维机械性能的影响。多种浓度的PCL，一种生物相容性聚合物，溶解在由乙酸和甲酸组成的最小毒性溶剂中。使用聚合物体积分数计算溶液中每个聚合物的缠结数（ne），并对所得电纺纤维的形态和力学进行了测量。对于ne范围为3.8至4.9的溶液，并且相应的浓度为13g/dL至17g/dLPCL的溶液，可以实现光滑纤维的一致静电纺丝。所得纤维的初始模量不取决于聚合物缠结。然而,在较高应变下的纤维力学检查，通过横向力原子力显微镜(AFM)进行，揭示了在不同浓度下形成的纤维之间的差异。随着聚合物缠结数从3.8ne溶液增加到4.9ne溶液,平均纤维延展性增加了35%。所有PCL纤维均表现出应变硬化行为。平均而言,应力随着应变增加到二次幂。因此,在较高的ne下，较大的延展性也导致纤维强度增加了两倍以上。我们的结果支持在大应变下聚合物缠结在电纺纤维机械性能中的作用。
