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چكيده انگليسي :

An Investigation on the Improvement of Electrospinning of Carboxymethyl Chitosan Nanofibers Negar Sohofi n sohofi@tx iut ac ir May 08 2011 Department of Textile Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Dr Hosein Tavanai tavanai@cc iut ac irAbstract Chitosan is one the few nitrogen containing natural polysaccharides Its inherent biological andphysicochemical characteristics are attributed to the unique amine functionality and it has attractedextensive attention in research because of its potential in biomedical and technological applications Carboxymethyl chitosan is one of the most important of Chitosan derivatives that has been synthesized byalkalization of chitosan followed by carboxymethylation with monochloroacetic acid In comparison tochitosan Carboxymethyl chitosan has better biological properties and chelating abilities Electrospinning isa unique technique to produce nanofibers using a high electric potential and is applicable to manypolymers Polymeric nanofibrous structures with several useful properties such as a high specific surfacearea and high porosity are of considerable interest for various applications Nanofibers of ionogenicpolymers are of great interest because of the peculiarities of the polyelectrolytes and also because of thepossibility of nanofiber modification on a subsequent step Although carboxymethyl chitosan is soluble inwater but studies show that electrospinning of aqueous solutions of Carboxymethyl chitosan just with theaddition of a non ionogenic water soluble polymer such as polyvinyl alcohol polyethylene oxide ispossible The present study focuses on the effect of the solvent on the electrospinning ability of purecarboxymethyl chitosan The solvents tested were acetic acid formic acid and trifluoroacetic acid TFA The first two solvents could not produce a visible jet as the electric field was applied Only the solution ofCarboxymethyl chitosan in TFA was electrospinable and fibers were deposited on the collector Exsistanceof beads on nanofibers suggested that optimization of the electrospinning conditions would be necessaryfor the preparation of a homogenous nanofiber network of carboxymethyl chitosan One possible approachto this optimization was to mix a volatile organic solvent with TFA Hence TFA and dichloromethane DCM were mixed With addition of dichloromethane to the carboxymethyl chitosan TFA solution nobeads were found on the electrospun carboxymethyl chitosan nanofibers Homogeneity of electrospunfibers also improved Under optimized conditions 5 w v concentration TFA DCM 70 30 homogenous carboxymethyl chitosan fibers with a mean diameter of 261nm were prepared The resultsshow that the three parameters viscoelastisity surface tension and electroconductivity have the mostsignificant effect on the electrospin ability of carboxymethyl chitosan To enhance the mechanicalproperties natural polymers are often blended with synthetic polymers or cross linked In this study Carboxymethyl chitosan polycaprolactone PCL nanofibers were prepared using TFA DCM 70 30 solvent mixture Stability of Carboxymethyl chitosan PCL blend system was 4 times greater than purecarboxymethyl chitosan The average diameters of the mixed fibers were in the range 277 329 nm Representative evidence for the presence of Carboxymethyl chitosan and PCL in the optimized system wasconfirmed by FTIR Results of physical characteristic showed that with increasing polycaprolactone ratio inthe blend relative humidity decreased and mechanical properties improves Keywords electrospinning carboxymethyl chitosan polycaprolactone trifluoroacetic acid

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