Electrospinning of Chitosan

Electrospinning of Chitosan

Kousaku Ohkawa,*1Dongil Cha,1Hakyong Kim,2Ayako Nishida,1Hiroyuki Yamamoto1

1Institute of High Polymer Research,Faculty of Textile Science and Technology,Shinshu University,Tokida3-15-1, Ueda386-8567,Japan

Fax:(þ81)268-21-5571;E-mail:kohkawa@giptc.shinshu-u.ac.jp

2Department of Textile Engineering,Chonbuk National University,Chonju644-765,Republic of Korea

Received:June16,2004;Revised:July29,2004;Accepted:July30,2004;DOI:10.1002/marc.200400253 Keywords:chitosan;electron microscopy;electrospinning;fibers;poly(vinyl alcohol)

Introduction

The nanofiber technology of present interest focuses on the electrospinning technique,which conveniently allows the preparation offibrous materials with veryfine diameters ranging from submicron to several nanometers.[1,2]The electrospinning phenomenon itself involves basic and significant issues in polymer science for solution dynamics, in which viscoelastic parameters,surface free energy (surface tension)and electroconductivity are critical factors for the successful spinning of nanofibers.[3,4]

The systematic understanding of the spinnability with an applied electricfield and the polymer solution parameters has been investigated.[5–8]A pioneering research group in thisfield comprehensively investigated the detailed mech-anism of electrospinning,including jet initiation,growth of bending instability,elongation of the jet and solidification of the jet into the nanofiber.[9–12]The polymer solution to be electrospun is usually placed in a pipette connected to the positive electrode.First,as the electricfield is applied,a charged jet is emitted from the droplet on a pipette tip. Second,the electrified liquid jet of the polymer solution evolves its electrically driven bending instability towards the collector,which neutralizes the charge of the jet.Third, thefluid jet solidifies into a nanofiber through evaporation of the solvent,resulting in the deposition of the nonwoven fibrous membrane on the collector.Thus,the solvent per-forms two crucial roles in electrospinning.One is to solvate the polymer molecules,ready to form the electrified jet. The other is to carry the solvated polymer molecules towards the collector,then to leave the polymerfibers by rapid vaporization of the solvent molecules.The appro-priate selection of a solvent system is a prerequisite for successful electrospinning.

Summary:An electrospun nonwoven fabric of a cationic polysaccharide,chitosan,was successfully prepared.The present study focuses on the effect of the electrospinning solvent and the chitosan concentration on the morphology of the resulting nonwoven fabrics.The solvents tested were dilute hydrochloric acid,acetic acid,neat formic acid and trifluoroacetic acid.As the chitosan concentration was in-creased,the morphology of the deposition on the collector changed from spherical beads to interconnectedfibrous networks.The addition of dichloromethane to the chitosan-TFA solution improved the homogeneity of the electrospun chitosanfiber.Under optimized conditions,homogenous (not interconnected)chitosanfibers with a mean diameter of 330nm were

Electrospinning of Chitosan

prepared.

Effects of the coexisting dichloromethane(MC)in the pre-

spun chitosan-TFA solution on the morphology of the elec-

trospun chitosanfibers.The volume ratio of TFA:MC was

70:30(Â5000).

Macromol.Rapid Commun.2004,25,1600–1605DOI:10.1002/marc.200400253ß2004WILEY-VCH Verlag GmbH&Co.KGaA,Weinheim 1600Communication

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