Nanofiber surface porosity

Different kinds of porosity can be present and measured in polymer nanofiber samples. Porosity can be a bulk property of a sample, namely a collective feature of polymer nanofibers assembly, non-woven, etc., or an internal property of individual nanofibers, or a surface property of either nanofiber-based coatings or of single filaments. These features impact on many properties of nanomaterials, ranging from fluid diffusion into and out of non-wovens or single nanofibers, to wettability, ability of drug delivery, of effectively exchanging bio-chemical signals, and so on. 

In a different way, the surface porosity of individual nanofibers is defined by the topography which can be present on the surface of each polymer filament. Depending on their nature and on the used fabrication method, surface features can extend from the nm-scale to hundreds of nm, thus possibly being... 

Porosity is one of the important parameter in filter design and filter performance. Past studies have shown that the thickness and porosity of the nanofiber mats can be controlled by changing the deposition rate of nanofibers. Adequate porosity and surface area of the nanofiber mat has turned nanofiber coatings as an important candidate for high performance filters. 

In a recent work, high flux UF membrane was prepared using electrospun nano-flbers of PAN, which was coated with CH solution. The nanofibrous PAN scaffold increased the surface porosity of the membrane, resulting in higher flux with the hydrophilic CH layer (Yoon et al. 2006). In the future, the use of nanofibers made up of CH may help in improving the performance of the subsequently fabricated UF and NF membranes. 

An electrospinning unit is a system for producing ultrafine fibers with a diameter of about 20-1000 nm. A nanofiber has a very high specific surface area, a small diameter, and large porosity. There are about hundred kinds of polymers that could be used as raw materials. 

Ultrafine fibers of PANl doped with CSA were blended with PEO by electrospinning. By controlling the ratio of PANl to PEO, desired conductivities were obtained. The comparison between cast films and nanofiber mats was reported. High porosity of nanofiber mats leads to lower conductivities compared to cast films but nanofiber mats have advantages like quick dedoping due to a higher surface area. 

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