Ordered Polymer Fibers

Abstract It is well known that the mechanical and physical properties of a fiber depend on the chemical structure of the polymer from which it is made and on the method used to build up the polymer. It is also known that a fiber contains “ordered” regions known as crystallites which are separated by other “disordered” amorphous regions . High performance synthetic fibers have higher strengths and often higher elastic moduli than conventional textile fibers because of the manufacturing processes employed and also, in many cases, because of their molecular or atomic structures. In the case of some high performance fibers, their properties can attain almost the limits of what is physically possible so that very high moduli, even up to that of graphite, can be achieved. The mechanical properties of the fiber are known to substantially improve with a decrease in the fiber diameter. Hence, there is considerable interest in the development of advanced continuous fibers with nanoscale diameters. A number of processing techniques, such as melt spinning and electrospinning, that are used to prepare polymer nanofibers have witnessed considerable technological development in recent years. The most relevant studied parameters of the electrospinning process include solution viscosity, conductivity, applied voltage, spinneret tip‐to‐collector distance, and humidity. When the diameter of the spun polymer fiber materials decreases from micrometers to submicrometers or nanometers, there appear several outstanding characteristics such as a very large surface area to volume ratio (this ratio for a nanofiber can be as large as 10 3 times of that of a microfiber), flexibility in surface functionalities, and superior mechanical performance (e.g., stiffness and tensile strength) compared with any other known form of the material. The effect of the molecular weight on the fiber‐forming properties of fibers is very critical. For selected applications, it is desirable to control not only the fiber diameter but also the internal morphology. Porous fibers are of interest for applications such as filtration or the preparation of functional nanotubes by fiber templates.