Electrospinning is widely accepted as a simple and versatile technique for producing nanofibers. The present work, however, introduces a new concept of the electrospinning method for controlling the crystal morphology and molecular orientation of the nanofibers through an illustration of a case study of polyoxymethylene (POM) nanofibers. Isotropic and anisotropic electrospun POM nanofibers are successfully prepared by using a stationary collector and a rotating disk collector. By controlling the voltage and the take-up velocity of the disk rotator, the morphology changes between an extended chain crystal (ECC) and a folded chain crystal (FCC) as clarified by a detailed analysis of the X-ray diffraction and polarized infrared spectra of the POM nanofibers. Herman's orientation function and dichroic ratio lead us to a schematic conclusion--that (i) molecular orientation is parallel to the fiber axis in both isotropic and anisotropic POM nanofibers, (ii) a single nanofiber consists of a nanofibril assembly with a size of 60-70 A and tilting at a certain degree, and (iii) the higher the take-up velocity, the smaller the nanofibril under the (9/5) helical structure of the POM chains. It should be emphasized here that the electrospinning method is no longer a single nanofiber producer but that it can be applied as a new instrument to control the morphology and chain orientation characteristics of polymer materials, opening a new research field in polymer science where we can understand the relationship between structure at the molecular level and the properties and performance at the macroscopic level.

A successful electrospun polyoxymethylene (POM) nanofiber using a hexafluoroisopropanol (HFIP)based solvent is reported. The nanofibers obtained show a significant nanoporous surface as a consequence of the spinning conditions, i.e. spinning voltage and relative humidity, as well as the polymer/solvent properties. The oxyethylene unit in the polyoxymethylene copolymer decreases the nanofiber surface roughness and porosity, leading to a significant change in the specific surface area. A slight change in the molecular weight of the POM after electrospinning confirms that the nanofiber with nanoporous POM barely degrades or decomposes during the spinning. The electrospun POM nanofiber gives an inevitable nanoporous structure with high specific surface area (as much as 2-3 times higher) compared to those of the nonporous electrospun nylon-6 and porous electrsopun PAN reported in the past.