UNAM-Institute of Materials Science & Nanotechnology, Bilkent University, Ankara, 06800, Turkey.
Nanoscale. 2012 Jan 21;4(2):621-31. doi: 10.1039/c1nr11364j. Epub 2011 Dec 7.
High molecular weight polymers and high polymer concentrations are desirable for the electrospinning of nanofibers since polymer chain entanglements and overlapping are important for uniform fiber formation. Hence, the electrospinning of nanofibers from non-polymeric systems such as cyclodextrins (CDs) is quite a challenge since CDs are cyclic oligosaccharides. Nevertheless, in this study, we have successfully achieved the electrospinning of nanofibers from chemically modified CDs without using a carrier polymer matrix. Polymer-free nanofibers were electrospun from three different CD derivatives, hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD) in three different solvent systems, water, dimethylformamide (DMF) and dimethylacetamide (DMAc). We observed that the electrospinning of these CDs is quite similar to polymeric systems in which the solvent type, the solution concentration and the solution conductivity are some of the key factors for obtaining uniform nanofibers. Dynamic light scattering (DLS) measurements indicated that the presence of considerable CD aggregates and the very high solution viscosity were playing a key role for attaining nanofibers from CD derivatives without the use of any polymeric carrier. The electrospinning of CD solutions containing urea yielded no fibers but only beads or splashes since urea caused a notable destruction of the self-associated CD aggregates in their concentrated solutions. The structural, thermal and mechanical characteristics of the CD nanofibers were also investigated. Although the CD derivatives are amorphous small molecules, interestingly, we observed that these electrospun CD nanofibers/nanowebs have shown some mechanical integrity by which they can be easily handled and folded as a free standing material.
高分子量聚合物和高聚合物浓度是电纺纳米纤维的理想选择，因为聚合物链缠结和重叠对于均匀纤维的形成很重要。因此，从非聚合物体系如环糊精（CDs）电纺纳米纤维是相当具有挑战性的，因为 CDs 是环状低聚糖。然而，在这项研究中，我们成功地在没有使用载体聚合物基质的情况下，从化学修饰的 CDs 中实现了纳米纤维的电纺。无聚合物纳米纤维是从三种不同的 CD 衍生物，羟丙基-β-环糊精（HPβCD）、羟丙基-γ-环糊精（HPγCD）和甲基-β-环糊精（MβCD）在三种不同的溶剂体系，水、二甲基甲酰胺（DMF）和二甲基乙酰胺（DMAc）中电纺得到的。我们观察到这些 CDs 的电纺与聚合物体系非常相似，其中溶剂类型、溶液浓度和溶液电导率是获得均匀纳米纤维的一些关键因素。动态光散射（DLS）测量表明，相当数量的 CD 聚集体的存在和非常高的溶液粘度在没有使用任何聚合物载体的情况下，对获得 CD 衍生物的纳米纤维起着关键作用。含有尿素的 CD 溶液的电纺没有得到纤维，只得到珠子或飞溅物，因为尿素会显著破坏其浓缩溶液中 CD 聚集体的自聚集。还研究了 CD 纳米纤维的结构、热和机械特性。尽管 CD 衍生物是无定形的小分子，但有趣的是，我们观察到这些电纺 CD 纳米纤维/纳米网具有一定的机械完整性，可以很容易地处理和折叠，作为一种独立的材料。
