Preparation Of Poly(Ethylene Oxide)–Poly(Acrylic Acid) Core-shell Nanofibers By Coaxial Electrospinning

Hydrogen bond is a kind of interaction that is much weaker than ionic bond,coordination bond and other chemical bonds,but it plays significantly important role in improving the polymer compatibility,the stability,physical properties and the crystal structure of compound,etc.And the hydrogen bonds can formed in the bulk body or at various interfaces.At present,the main researches on the formation of hydrogen bonds at the interface are to prepare interfacial hydrogen-bonded composite membranes by useing hydrogen bonds as the driving force for a Layer-by-Layer self-assembly technology,but about the interfaced hydrogen-bonded composite fibers are rarely reported.This is mainly because the preparation of composite nanofibers with hydrogen bonding at the surface is difficult,and the fiber size can't be controlled.Coaxial electrospinning provides a simple and effective method for the preparation of core-shell composite fibers with hydrogen bonding at the interface.In this paper,PEO was used as the hydrogen bond acceptor and PAA as the hydrogen bond donor,because PEO and PAA could form PEO/PAA hydrogen-bonded complexes with outspread conformation and a relatively large volume.At first,we respectively electrospun different concentration PEO and PAA solutions at different voltage and researched the influence of polymer solution properties,process of electrospinning,ambient on the morphology of the fiber.What we have done above was to lay a certain experimental foundation for electrospinning core-shell nanofibers.The morphology of the fibers was characterized by scanning electron microscopy(SEM).The thermodynamic and mechanical properties of the fiber membranes were characterized by DSC and fiber strength tester.While FI-IR spectroscopy was used to test the formation and intensity of hydrogen bonds in the fiber membrane.PAA is a kind of polyelectrolyte with good mechanical properties and thermodynamic stability,and the chemical activity of hydrophilic functional group-COOH make PAA be widely used in the superabsorbent resin and the adsorption of dyes and metal ions in wastewater.However,PAA itself is easily soluble in water,so it is necessary to cross-link the PAA to improve its stability in water.In this experiment,EG worked as cross-linking agent,H2SO4 as initiator,and the prepared PAA nanofiber membranes were dealt at different cross-linking temperatures.We also researched the effect of EG concentration,PAA solution concentration and voltage on the morphology of PAA nanofibrous membranes.The effect of cross-linking temperature and crosslinking time on the cross-linking degree of PAA nanofibers were also investigated.PEO-PAA and PEO-PAA/EG core-shell nanofibers were prepared by coaxial electrospinning respectively.The core-shell nanofibers with uniform diameter and concentric structure were prepared,and were respectively characterized by SEM and TEM.In experiments,we changed the spinning speed of core layer to fabricate coreshell nanofibers with different surficial areas,and verified that hydrogen bonds were formed at the interface between PEO and PAA.In addition,the two kinds of core-shell nanofibers were thermally crosslinked,and the mechanical properties of the core-shell nanofiber membranes before and after thermal crosslinking were characterized by the fiber strength tester.