Electrospinning molecular orientation

Electrospinning is not a new technology for polymer fibre production. It has been known since the 1930 s however, it did not gain significant industrial importance due to the low output of the process, inconsistent and low molecular orientation and poor mechanical properties of the electrospun fibres. 

On the basis of the DSC data summarized in Table 8.3, the crystallization temperature (T ) of PLA fibers becomes lower than that of as-received PLA pellets. It is convincing that the crystallization process can be accelerated by the well-structured PLA molecular chains when tailored into the fiber-like form. By decreasing HMW PCL concentration from 15 to 9wt%/v, the glass transition temperature (T ) of PCL within PLA/PCL blends is reduced whereas the of PLA is hardly identified in that its point has overlapped the melting peak of PCL. The different thermal properties in terms of and melting temperature (T ) may be influenced by the variation of fiber diameters as well as electrospinning process for the orientation of polymer chains [32]. In comparison to HMW PCL with PLA in blends, LMW PCL gives rise to an evident increase in the of PLA, but a considerable decline in the of PCL. The solvent effect on thermal... 

Unlike with droplets of low-molecular-weight liquids or monomers that subdivide into smaller droplets under a strong electric field, polymer solutions undergo a degree of elongational flow and orientation in an electric field. It is the entanglement of the partially oriented, expanded conformations of polymer chains that makes their electrospinning possible in the first place. Solvents that yield open conformations of polymer chains and... 

The electrospun PVDF and P(VDF-TrFE) fibrous webs have good piezoelectric properties, showing that they have preferred orientation of molecular dipoles. In order to prove this, P(VDF-TrFE) webs were characterized by infrared (IR) spectroscopy and the piezoelectric signal from the electrospun nanofiber web. The result provides the evidence of the preferential orientation of CF2 dipoles in the P(VDF-TrFE) nanofiber web during electrospinning. 

---