Nano-Superfine Polymer Fibers by Electrospinning and Their Thermal-Switching Function

Abstract

Intelligent or smart polymer materials are those which are either “active” or responsive to a variety of environmental stimuli, such as changes in pH, temperature, ionic strength or electric field, or the presence of a specific chemical substrate. A thermally sensitive polymer, poly(N-isopropylacrylamide) (PNIPAAm), has been of great interest because aqueous solutions of PNIPAAm undergo fast, reversible switching of hydrophilicity/hydrophobicity around 32 °C at their lower critical solution temperature (LCST) of about 29–38 °C (different with variations in their structure). PNIPAAm chains show an expanded conformation in water below the LCST because of strong hydration and change to the compact forms above the LCST by sudden dehydration; this is the reversible switching effect of hydrophilic to hydrophobic. These switchable materials may have wide applications in functional textiles, controllable drug release and special fibers. Electrospinning is a simple, convenient, and versatile technique for generating fibers with diameters that range from several micrometers to tens of nanometers. Herein, we report an electrospinning method to prepare nano PNIPAAm fiber and their thermal response was characterized. Based on the results, the diameters of the PNIPAAm nanofibers within the respective system were around 200 nm and beads-less; they were successfully prepared by an electrospinning method in all cases and the reversible switching with LCST (32 °C) feature was observed clearly in the fibers.