Nawn G, Vezzù K, Negro E, Pace G, Park J W, Wycisk R, Cavinato G, Pintauro P N, Di Noto V
Section of Chemistry for the Technology (ChemTech), Department of Industrial Engineering, University of Padova, Via Marzolo 9, I-35131 Padova (PD), Italy.
Phys Chem Chem Phys. 2019 May 22;21(20):10357-10369. doi: 10.1039/c9cp01891c.
A new type of polymer blend, prepared by electrospinning nanofibers containing the immiscible polymers polyvinylidene fluoride (PVDF, 10 wt%) and Nafion® perfluorosulfonic acid (90 wt%), has been characterized experimentally. The internal nanofiber morphology is unique and unlike a normal blend, with individual phase-separated and randomly distributed fibrils of Nafion and PVDF (∼2-7 nm in diameter) that are bundled together and aligned in the fiber axis direction (where the fiber diameter is ∼500 nm). This morphology is retained when fiber mats are hot-pressed into dense films. The physicochemical properties of the electrospun blended fibers are also highly unusual and unanticipated. As shown in this study, each polymer component influences the thermal and structural behavior of the other, especially in the dry state. Thus, dry composite polymer mats and membranes exhibit properties and attributes that are not observed for either pure PVDF or pure Nafion. Experimental results indicate that: (i) PVDF imparts conformational constraints on the polytetrafluoroethylene (PTFE) backbone chains of Nafion, resulting in an increased 21 helical conformation that effects Nafion's water uptake and thermal properties; and (ii) dipole-dipole interactions between PVDF polymer chains and Nafion make the β-phase polymorph of PVDF much more stable at elevated temperatures. Such "reciprocal templating" in electrospun fibers may not be unique to Nafion and PVDF, thus the procedure represents a new method of creating nanostructured multi-component polymer materials with innovative features.
通过静电纺丝制备了一种新型聚合物共混物，该共混物包含不相容的聚合物聚偏氟乙烯（PVDF，10重量%）和全氟磺酸Nafion®（90重量%），并对其进行了实验表征。内部纳米纤维形态独特，与普通共混物不同，Nafion和PVDF的单个相分离且随机分布的原纤维（直径约2 - 7纳米）聚集在一起并沿纤维轴方向排列（纤维直径约500纳米）。当纤维毡热压成致密薄膜时，这种形态得以保留。静电纺丝共混纤维的物理化学性质也非常独特且出人意料。如本研究所示，每种聚合物组分都会影响另一种组分的热行为和结构行为，尤其是在干燥状态下。因此，干燥的复合聚合物毡和膜表现出纯PVDF或纯Nafion所没有的性能和特性。实验结果表明：（i）PVDF对Nafion的聚四氟乙烯（PTFE）主链施加构象限制，导致21螺旋构象增加，从而影响Nafion的吸水性和热性能；（ii）PVDF聚合物链与Nafion之间的偶极 - 偶极相互作用使PVDF的β相多晶型在高温下更稳定。静电纺丝纤维中的这种“相互模板化”可能并非Nafion和PVDF所独有，因此该方法代表了一种制备具有创新特性的纳米结构多组分聚合物材料的新方法。
