The Wallace H. Coulter Department of Biomedical Engineering, School of Chemistry and, Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
Langmuir. 2013 Jun 11;29(23):7070-8. doi: 10.1021/la400747y. Epub 2013 Apr 4.
This article presents a simple and reliable method for generating polystyrene (PS) yarns composed of bundles of nanofibrils by using a proper combination of solvent and relative humidity. We elucidated the mechanism responsible for the formation of this new morphology by systematically investigating the molecular interactions among the polymer, solvent(s), and water vapor. We demonstrated that vapor-induced phase separation played a pivotal role in generating the yarns with a unique structure. Furthermore, we discovered that the low vapor pressure of N,N-dimethylformamide (DMF) was critical to the evolution of pores in the interiors. On the contrary, the relatively high vapor pressure of tetrahydrofuran (THF) hindered the formation of interior pores but excelled in creating a rough surface. In all cases, our results clearly indicate that the formation of either internal porosity or surface roughness required the presence of water vapor, a nonsolvent of the polymer, at a proper level of relative humidity. The exact morphology or pore structure was dependent on the speed of evaporation of the solvent(s) (DMF, THF, and their mixtures) as well as the interdiffusion and penetration of the nonsolvent (water) and solvent(s). Our findings can serve as guidelines for the preparation of fibers with desired porosity both internally and externally through electrospinning.
本文提出了一种简单可靠的方法，通过适当组合溶剂和相对湿度，将纳米纤维束生成聚苯乙烯（PS）纤维。我们通过系统研究聚合物、溶剂和水蒸气之间的分子相互作用，阐明了形成这种新形态的机制。我们证明，蒸汽诱导相分离在生成具有独特结构的纤维方面起着关键作用。此外，我们发现 N,N-二甲基甲酰胺（DMF）的低蒸汽压对于孔在内部的演变至关重要。相反，四氢呋喃（THF）的相对较高的蒸汽压阻碍了内部孔的形成，但在形成粗糙表面方面表现出色。在所有情况下，我们的结果清楚地表明，无论是内部孔隙还是表面粗糙度的形成，都需要在适当的相对湿度水平下，存在聚合物的非溶剂水蒸气。确切的形态或孔结构取决于溶剂（DMF、THF 及其混合物）的蒸发速度，以及非溶剂（水）和溶剂的互扩散和渗透速度。我们的发现可以为通过静电纺丝制备具有所需内外孔隙率的纤维提供指导。
