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Electrochimica Acta 54 (2009) 5739–5745

Contents lists available at ScienceDirect

Electrochimica Acta

journa l homepage: www.e lsev ier .com/ locate /e lec tac ta

tudies on electrospun nylon-6/chitosan complex nanofiber interactions

aitao Zhanga, Shubai Li a, Christopher J. Branford Whiteb, Xin Ningc, Huali Niea,∗, Limin Zhua,∗

College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, 2999 North Remin Road, Songjiang University City, Shanghai, 201620, ChinaInstitute for Health Research and Policy, London Metropolitan University, 166-220 Holloway Road, London, N78DB, UKKimberly-Clark (China) Co., Ltd, Shanghai, 200001, China

r t i c l e i n f o

rticle history:eceived 21 February 2009eceived in revised form 6 May 2009ccepted 8 May 2009vailable online 14 May 2009

eywords:lectrospinning

a b s t r a c t

Composite membranes of nylon-6/chitosan nanofibers with different weight ratio of nylon-6 to chitosanwere fabricated successfully using electrospinning. Morphologies of the nanofibers were investigated byscanning electron microscopy (SEM) and the intermolecular interactions of the nylon-6/chitosan complexwere evaluated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differentialscanning calorimetry (DSC) as well as mechanical testing. We found that morphology and diameter ofthe nanofibers were influenced by the concentration of the solution and weight ratio of the blendingcomponent materials. Furthermore FT-IR analyses on interactions between components demonstrated

ylon-6/chitosan blendomposite membraneanofiber

nteraction

an IR band frequency shift that appeared to be dependent on the amount of chitosan in the complex.Observations from XRD and DSC suggested that a new fraction of � phase crystals appeared and increasedwith the increasing content of chitosan in blends, this indicated that intermolecular interactions occurredbetween nylon-6 and chitosan. Results from performance data in mechanical showed that intermolecularinteractions varied with varying chitosan content in the fibers. It was concluded that a new compositeproduct was created and the stability of this system was attributed to strong new interactions such as

betw

hydrogen bond formation

. Introduction

In the field of nanotechnology, polymer nanofibers have becomeprominent area of interest. Among the processes used to prepareanofibers, electrospinning is regarded as a simple and versatileethod to generate nano- to submicrometer fibrous structures

1]. The generated nanofibers have notable characteristics suchs a large surface area to volume ratio, high porosity, good porenterconnectivity and the possibility to incorporate active compo-ents on a nanoscale. These properties make fibers ideal candidates

n applications such as filtration [2–5], tissue engineering [6–8],anufacture of protective clothing, pharmacy and functional mate-

ials [9–12]. The fabrication of nanofibers from biopolymers haslso attracted researcher’s interest due to the biopolymers havingnhanced biocompatibility and biodegradability [13].

Chitosan, is a copolymer of (1 → 4)-2-acetamido-2-deoxy-�-d-lucan and (1 → 4)-2-amino-2-deoxy-�-d-glucan and is the only

ationic polysaccharide derived from chitin. Due to abundance ofhitin in nature it is cheap to access and exhibit high degrees ofiostability in terms of physiochemical properties. Thus chitosan-ased products have been used in biomedical devices, wound

∗ Corresponding authors. Tel.: +86 21 67792659; fax: +86 21 67792655.E-mail addresses: lzhu@dhu.edu.cn (L. Zhu), niehuali2004@126.com (H. Nie).

013-4686/$ – see front matter © 2009 Elsevier Ltd. All rights reserved.oi:10.1016/j.electacta.2009.05.021

een the nylon-6 polymers and chitosan structures.© 2009 Elsevier Ltd. All rights reserved.

healing, controlled drug delivery [14], food packing [15] and wasteremoval systems [16].

Although electrospinning of chitosan has been investigated,it is found that the manufacture of pure chitosan nanofibersis extremely difficult and as an outcome, recent research hasfocused on electrospinning blends of chitosan and other compati-ble polymers. The incorporation of chitosan into PVA and PEO forthe preparation of blended materials has been reported [17–23].Recently the nylon-6/chitosan complex nanofibers have been suc-cessfully prepared by electrospinning in our laboratory. Similarlynylon polymers have many uses as an engineered material becauseof its strong mechanical properties such as high tensile and impactstrengths and abrasion resistance properties [24–26]. Nylon-6 isa semi-crystalline polymer that is stabilised by hydrogen bondsinvolving amide groups between the methylene chains [27]. Elec-trospinning of nylon-6 and chitosan may produce blends thatexhibit properties shown by both individual polymers and thoughthis combination becomes a new material for biomedical applica-tions.

An important aspect of developing a polymer blend is to firstconsider the miscibility properties of the components involved. The

most common interactions in the blends are hydrogen and ionicbonding and the formation of dipole and charge-transfer complexes[28]. Most blends are immiscible with each other due to the absenceof specific interactions. However chitosan can form complex withnylon with efficient blending processes. Furthermore it has also

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een shown that chitosan can modify the biological and mechan-cal properties of nylon forming new hydrogen bonding networksetween the polymers [29–33].

The characterization of nylon/chitosan nanofibers using elec-rospinning and the intermolecular interactions in electrospunomplex has not been previously reported. In this study, theomposite nanofibrous membranes based on a series of nylon-/chitosan complex with different weight ratio of nylon to chitosanere fabricated using a mixed solvent system. FT-IR, XRD, DSC andechanical testing were applied to determine the nature and prop-

rties of the intermolecular interactions stabilizing the nanofiberomplex.

. Experimental

.1. Materials

Nylon-6 (weight average molecular weight ∼20,000 g/mol)as purchased from Shanghai Chemical Fibers Institute. Chitosan

molecular weight average 80,000 with over 85% deacetylation)as supplied by National Pharmaceutical Group Corp., China. Two

olvents, 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) from Fluorochemtd. (United Kingdom) and formic acid (FA) from National Pharma-eutical Group Corp., China, were used to dissolve the blends ofhitosan and nylon-6.

.2. Electrospinning procedures

Nylon-6 and chitosan blends were dissolved in HFIP/FA (90/10,/v) at a concentration of 6 wt% (g/ml). Nylon-6 was mixed withhitosan in weight ratios of 100/0, 90/10, 85/15, 80/20, 75/25, and0/30, respectively. These preparations were then used for electro-pinning.

Electrospinning were performed at room temperature. The poly-er solution was placed in a 5 mL syringe with a metal needle of

.6 mm in diameter. A power supply (ES40P-20W/DAM) was usedo provide a high voltage, 16 kV to the syringe needle tip and a

etal collector. The electrospun fibers were collected on an alu-inum foil. With a tip-to-collector distance of 15 cm and a solution

ow rate of 1 mL/h before drying in a vacuum oven for 24 h at0 ◦C.

.3. Measurement and characterization

The morphology and diameter of the electrospun nanofibersere determined by scanning electron microscopy (SEM) (JeoL JSM-600 LV, Japan). Prior to scanning samples were sputter coated for0 s with gold using a JEOL JFC-1200 fine coater. The diametersf fibers were analyzed using image visualization software Adobehotoshop.

FT-IR spectra of the electrospinning nanofibers and the filmsere recorded with a Nicolet 17DSX FT-IR Spectrometer.

XRD patterns of the electrospinning nanofibers and the filmsere evaluated by a D/Max-2550 PC X-ray diffractometer (Rigaku,

apan) with Cu K�-radiation at 2� range of 5–50◦.The thermal properties of the electrospun fibers were measured

y a TA Instruments DSC-822 Differential Scanning Calorimeter

Mettler Toledo Company, Switzerland) over a temperature rangef 20–300 ◦C at a heating rate of 10 ◦C/min.

Tensile tests were measured according to ASTM D882 usinguniversal testing machine (Instron5566, Instron, Canton, MA).

ll samples were cut to the standard dumbbell shape, condi-ioned overnight (21 ± 1 ◦C, relative humidity of 65 ± 2%) beforeesting.

cta 54 (2009) 5739–5745

3. Results and discussion

3.1. Solvent quality

Although the fabrication of the nylon and chitosan blendednanofiber membranes have been studied previously [29–33],the present work studies the intermolecular interactions in thenylon/chitosan nanofibers; this to our knowledge has not beenreported. A problem for nylon/chitosan electrospinning is todetermine a suitable solvent system that will accommodatehydrogen-bonded polymers such as nylon-6. Similarly, as thesolvent quality decreases, effects of polymer–polymer interac-tions on solution viscosity become increasingly important andmust be taken into account [34]. Therefore, selecting appro-priate solvent system is an important factor when developingand optimizing the electrospinning process. In recent years,1,1,1,3,3,3-hexafluoroisopropanol (HFIP) has been used in generat-ing electrospun nylon nanofibers [35,36]. Initially an attempt wasmade to dissolve chitosan in HFIP and this resulted in the formationof a gel that could not be electrospun owing to the high viscosityof the systems. Based on a previous study where it was reportedthat chitosan could be dissolved in dilute acidic solvent [37]. FA ofvarious fractions was added to chitosan in HFIP to enhance solubil-ity. As a result the viscosity of the solution decreased significantlyand subsequently the suspension was electrospun into fibers expe-ditiously. Thus we report the use of a new solvent system, HFIP andFA (v/v = 9:1) and this stabilizes solution for the successful electro-spinning of chitosan and nylon-6 blends.

3.2. Characterization of complex nanofibers

SEM photographs of nylon-6/chitosan blend nanofibers as afunction of concentration (nylon-6/chitosan = 80/20) are shown inFig. 1. Results showed that the morphology and average diameterof the nanofibers change significantly with respect to the concen-tration of the blend solution. It was found that the morphologyof the fibers changed gradually from a bead structure to the uni-form fiber form with increasing concentration. The average fiberdiameter decreased with the decrease of the concentration whenother parameters were fixed. However spinning also declined withdecreasing concentration and the process became unstable whenthe concentration of the solution fell below 4 wt%. In contrast, whenthe concentration of the chitosan/nylon-6 blend was 8 wt%, elec-trospinning was hard to maintain due to the high viscosity andthe fibers became asymmetric. The objective of our study was toprepare chitosan/nylon-6 blend solution that contained maximumlevels of chitosan content in the blend. It was reported that theaddition of cationic and anionic polyelectrolytes could increase theconductivity of polymer and consequently lead to thinner fibers[38]. Chitosan is a cationic polysaccharide with amino groups,which are ionizable under acidic or neutral pH conditions. There-fore, the morphology and diameter of electrospun fibers will beinfluenced by the weight ratio of chitosan/nylon-6.

Fig. 2 shows SEM micrographs of the nanofiber mat that wasformed using nylon-6/chitosan blend with varying weight ratios.This resulted in different fiber diameters, ranging from 0.1 to0.9 �m. For example, the fiber diameter gradually decreased withincreasing chitosan content while the fibers became more andmore nonuniform. When the chitosan content was above 30 wt%nanofiber spinning became impossible. These phenomena can beexplained as follows: chitosan is ionic polyelectrolytes with a higher

charge density on the surface of ejected jet formed during elec-trospinning. As the charges carried by the jet increases, higherelongation forces are imposed to the jet under the electrical field. Ithas been known that the overall tension in the fibers depend on theself-repulsion of the excess charges on the jet. Thus, as the charge

H. Zhang et al. / Electrochimica Acta 54 (2009) 5739–5745 5741

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Fig. 1. SEM photographs of the electrospinning fibers as a function o

ensity increases the diameter of the final fibers becomes smaller38,39]. When the chitosan content >30 wt% the fibers formationecame impossible under the spinning condition employed.

The surface hydrophilicity of electrospun nanofiber mats couldlay an important role in their overall performances for biomedi-al applications. We studied this by measuring the water contactngle. The water contact angle values at 4th and 8th second afterhe droplet contacted with the electrospun mats are shown in Fig. 3.

It was found that the contact angle decreases gradually from4.3 ± 2.5◦ to 8.9 ± 1.1◦ and this occurs as the content of chitosan

n the copolymer increased from 0 to 25 wt% after the 4th secondhe droplet had contact with the electrospun mats. It appearedhat the nanofiber mat containing pure nylon-6 had the lowestydrophilicity (highest water contact angle), while the mat with5 wt% weight ratio of chitosan possessed the highest hydrophilic-

ty (smallest water contact angle). As shown (Fig. 3), after about 8 she water droplets were placed on the nanofiber mats, the contactngle of the pure nylon nanofiber mat was 21◦, while those ofhe nanofiber mats mixed chitosan were close to 0◦. These resultsurther support our previous speculations that chitosan, has severalunctional groups that are able to interact with other functionalizedolymers. Chitosan has four hydroxyl groups, an amine group, andminor proportion of amide groups, which are, in general, partiallyydrolyzed. All these functional groups enhance the hydrophilicroperties of the natural biopolymer chitosan and so enhanceechanical strength when complexed with hydrophobic material

uch as nylon-6. Blends that include varying amounts of chitosanill affect the degree of hydrophobicity compared to pure nylon-6

ystem. Since scaffold with higher hydrophilicity are generally moreavorable for biomedical applications, we believe that the compos-te nanofiber mat would outperform the neat nylon nanofiber mats

ithin this context. Additionally, the results also suggested thathe electrospinning of nylon-6/chitosan complex could be utilizeds a general approach for tailoring the hydrophilicity of nanofiberats and so could be designed for drug delivery usage.

.3. Fourier transform infrared spectroscopy (FT-IR)

The interactions between nylon-6 and chitosan within the elec-rospun fibers have been confirmed by FT-IR spectra of chitosan,ylon-6 and their blends. FT-IR is a well-defined method to detecthe intermolecular interactions between two polymers. Besidesreating new functional groups through chemical reaction betweenhe polymers, intermolecular interactions through hydrogen bond-ng can also be characterized by FT-IR. This is possible due to specific

nteractions that influence the vibrational frequency of functionalroups as detected through the FT-IR [37].

Fig. 4a shows a typical FT-IR spectrum of the raw chitosan. Theharacteristic absorption bands for raw chitosan were observed asollows: the absorption occurs around 898 and 1150 cm−1 and these

oncentration (nylon-6/chitosan = 80/20; voltage, 16 kV; TCD, 15 cm).

peaks are assigned to saccharine structure in the macromolecule.Bands at 1060 and 1029 cm−1 involve C O stretching, the weakeramino characteristic peak at 1255 cm−1 was the absorption of �(O–H) or C–O–C bands, and the peak at 1380 cm−1 was assigned tothe –CH3 symmetrical deformation mode [40]. Two middle strongbands at 1655 and 1590 cm−1 that may be attributed to the carbonylC O or amide I band and amide II absorption band, respectively[41]. A broad band in the range of 3400–3100 cm−1 is attributed toN–H and OH· · ·O stretching vibrations and intermolecular hydrogenbonding of the polysaccharide molecules.

Fig. 4b shows the characteristic bands for amide groups andmethylene segments of nylon-6. Their assignments are: 3300 cm−1

(H-bonded N–H stretch vibration), 3080 cm−1 (N–H in-plane bend-ing), 1640 cm−1 (amide I, C O stretch), 1540 cm−1 (amide II, C–Nstretch and CO–N–H bend), 940 cm−1 (amide IV, C–CO stretch) [42].Fig. 4c–f shows the FT-IR spectra of electrospun complex nanofiberswith different weight ratio of nylon-6 to chitosan. Compared withthe FT-IR spectra for pure chitosan or neat nylon membrane, theabsorption peak of blend nanofibers at 1255 and 1160 cm−1 cor-responding to the C–O–C bands disappeared. A new absorptionpeak appears at 1400 cm−1, which represent the –COO− band wasobserved. This suggests that amine salts could be formed betweenchitosan and FA. It is reported that dilute acidic solvent can formsalts with the amino groups of chitosan [37]. The formation of saltdestroys strong interactions between the chitosan molecules. Com-paring with raw chitosan, amides I and II bands shift to lower wavenumbers. Shifting of the amide II peak from 1590 to 1550 cm−1 inthe spectra of the electrospun blend membrane is also evident. Thismay be assigned to the electron charge in electrospinning facilitat-ing the reaction between –NH2 of chitosan and –COOH of FA. Theseresults imply that new hydrogen bonds or intermolecular interac-tions can be formed between chitosan and HFIP/FA mixtures duringthe electrospinning process.

The increase in the frequency of the N–H band suggested thataddition of chitosan resulted in the attenuation of the hydrogenbond between polyamide chains. The vibrational frequency of thestretching mode of the diatomic molecule N–H can be calculatedby using Eq. (1):

v (cm−1) =(

12�c

)√Kf

MN + MH

MNMH(1)

where Kf is the force constant, or stiffness of the bond, c is thespeed of light and MN and MH are the masses of the two atoms,respectively. The force constant could be expressed as Eq. (2):

[X X

]3/4

Kf ∝ Nb

N H

d2(2)

where Nb is the bond order, d is the bond length, XN and XH are theelectro-negativities of atoms N and H, and d is the distance betweentwo atoms, respectively.

5742 H. Zhang et al. / Electrochimica Acta 54 (2009) 5739–5745

F hitos

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ig. 2. SEM photographs of nanofiber mat with different weight ratio of nylon-6 to c

According to Eqs. (1) and (2), decreasing the bond length or

ncreasing the bond order would contribute to an increase inhe stiffness of the bond (Kf) and then would increase the fre-uency of N–H bond. Mixing chitosan with nylon-6 will breakhe hydrogen bond in the C O–H–N amide plane of the blendinglms and successively the dipoles will switch to a new direc-

an and the diameter distribution (concentration, 6 wt%; voltage, 16 kV; TCD, 15 cm).

tion to reduce the energy and recreated a new amide plane with

the inserted chitosan molecules [31]. The interactions betweennylon-6 and chitosan may occur by new hydrogen bonds forma-tion. The –C O groups in nylon-6 are capable of forming hydrogenbonds with –OH and –NH2 groups in chitosan, as is shown inFig. 5.

H. Zhang et al. / Electrochimica Acta 54 (2009) 5739–5745 5743

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nylon and chitosan blend which did not lead to the formation ofthe crystalline microstructure of electrospun fibers. The reason forthe retardation could be explained as follows. During electrospin-ning, the stretched molecular chains of the fibers rapidly solidify

ig. 3. Water contact angle variations of electrospun nylon-6/chitosan blendanofibers with different weight ratio of nylon-6 to chitosan. Each datum is the meanalue of five measurements with the error bar representing one standard deviation.

.4. Melting, crystallization and orientation behaviors

XRD and DSC studies were used to study the melting andrystallization behaviors of both the neat nylon-6 and theylon-6/chitosan nanocomposite nanofibers. The X-ray diffractionnalyses are shown in Fig. 6.

For pure nylon nanofibers, there were two peaks around� = 20.260◦ (d = 4.3795 Å) and 2� = 23.440◦ (d = 3.7920 Å) for asuenched nylon-6 film due to the amorphous structure, corre-ponding to the � crystalline phases [43]. The inset illustrate theiffraction model of pure chitosan showing three typical peaks at� = 10.974◦ (d = 8.0556 Å), 2� = 19.900◦ (d = 8.0556 Å), 2� = 29.340◦

d = 3.0415 Å) [44]. If there were no or weak interactions betweenhitosan and nylon molecules in the blend fibers, each componentould have its own crystal region in the blend fibers and XRD pat-

erns would be expressed as simple combined patterns of chitosannd nylon with the same ratio as those in the mechanical blending.n fact, another distinct peaks at 2� ≈ 33.9◦ (d = 2.64 Å) characteristicf the � phase also appeared [45]. The peak of nylon at 2� ≈ 23.440◦

ig. 4. FT-IR spectra of (a) raw chitosan and electrospun complex nanofibers withifferent weight ratio of nylon-6 to chitosan: (b) 100/0; (c) 90/10; (d) 85/15; (e)0/20; (f) 75/25.

Fig. 5. Studies of hydrogen bonding between polyamide chains in nylon-6 and chi-tosan.

and the peak of chitosan disappeared with increasing CS content inthe blend. This is demonstrated in Fig. 6b–e. From these resultsit can be concurred that strong interaction occurred between chi-tosan and nylon molecule in the blends. Furthermore, in the caseof the raw chitosan one reflection at around 8.0◦ and a broad bandat around 19.9◦ are observed (Fig. 6f). After electrospinning, theblends fibers show typical amorphous broad peak at around 20.5◦

that means both nylon-6 and chitosan molecular chains cannotbe easily crystallized during electrospinning and so give a similaramorphous structure in the nanofibers. This phenomenon con-firmed that electrospinning retarded the crystallization process of

with high elongation rates, which significantly hindered the forma-

Fig. 6. X-ray diffraction patterns of electrospun complex nanofibers with differentweight ratio of nylon-6 to chitosan: (a) 100/0; (b) 90/10; (c) 85/15; (d) 80/20; (e)75/25. The inset illustrates (f) is the XRD spectra of the chitosan.

5744 H. Zhang et al. / Electrochimica Acta 54 (2009) 5739–5745

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ig. 7. DSC thermograms of electrospun complex nanofibers with varying contenteight ratio of nylon-6 to chitosan: (a) 100/0; (b) 90/10; (c) 85/15; (d) 80/20; (e)5/25.

ion of crystals. These confirm the existence of interactions betweenylon-6 and chitosan during spinning.

Fig. 7 demonstrated the effects of the addition of chitosandditives on the crystallization behavior of electrospun nylon-6embranes as measured by DSC. Electrospun membrane of pure

ylon-6 exhibited a melting point at about 268.4 ◦C, this being dueo the melting of � form crystals (Fig. 7a). However, the electrospunylon-6 membranes with increasing chitosan contents showed aystematic shift of the melting point towards a lower temperatureFig. 7b–e), reaching 258.1 ◦C with 25% chitosan content (Fig. 7e).his is the melting temperature of � form crystals [45]. This melt-ng endothermic change indicated a change of crystalline phase.imilar shifts to lower melting temperature were also for otherdditives containing nylon-6 membranes [46]. However, with chi-osan content increasing to 25% (Fig. 7e) resulted in a reduction in

elting point (258.1 ◦C). The reason for this observation is currentlynder review. Otherwise no significant effects were observed onhe glass transition temperature (Tg) of the nanofiber membranes.hese results are consistent with the X-ray studies reported here.

.5. Tensile strength

The ultimate tensile strength and tensile strain for all thelectrospun nylon-6/chitosan nanofibrous membranes with vari-us chitosan contents were tested and summarized (Fig. 8). Thisrocess characterises the relationship between the average ulti-ate tensile strength, average ultimate tensile strain and chitosan

ontent. The neat nylon nanofibers showed highest tensile strainhich was about four times greater compared to other electrospun

lends fibers that had differing chitosan content. By increasing theeight ratio of chitosan showed a decrease in the average tensile

trength.In blends that reflect the addition of chitosan suggested that

he increase in the frequency of the N–H band also resulted inhe attenuation of the hydrogen bond between polyamide chains.urthermore, decreasing the bond length or increasing the bond

rder would contribute to an increase in the stiffness of the bond31]. Mixing chitosan with nylon-6 will break the hydrogen bondn the C O–H–N amide plane of the blending films and succes-ively the dipoles will switch to a new direction to reduce thenergy and recreated a new amide plane with the inserted chitosan

Fig. 8. Tensile properties of electrospun nylon-6/chitosan blend nanofibers withdifferent weight ratio of nylon-6 to chitosan.

molecules. It was inferred that after blending, the hydrogen bondbetween C O and N–H was weakened since new hydrogen bondsbetween polyamide chains and chitosan molecules were formed.Consequently, the distance between two polyamide chains weredistorted. It is concluded that addition of chitosan disturbed theoriginal hydrogen bond in the nylon-6 polymer chains and thedisturbance was more significant with the higher addition percent-age of chitosan. With chitosan added to nylon-6 the interactionsbetween two components can change the hydrogen bonds and thestiffness of the nylon main chains, which affect the stretching prop-erties in the chains of nylon-6. When chitosan content in the fibersis increased to 20% and 25% the average tensile strength and strainof blends fibers decrease obviously, which is shown in Fig. 8. Theseresults confirm observation obtained from FT-IR studies.

4. Conclusion

The composite nylon-6/chitosan nanofibrous membranes withvarying weight ratio of nylon to chitosan were successfully fabri-cated by electrospinning. The morphology, diameter, and structureof electrospun nanofibers were investigated. SEM showed that themorphology and diameter of the nanofibers were affected by thecombination of the polymer mix and blending. Contact angle mea-surement revealed that the increased ratio of chitosan enhanced thehydrophilicity properties of the composite nanofibers. FT-IR, XRD,DSC and mechanical measurements also demonstrated the exis-tence of intermolecular interactions between nylon-6 and chitosanin the fibers. These results clearly imply the formation of a new com-patible polymer blend and the compatibilization of this system isattributed to strong interactions that engage the formation of newhydrogen bonds between the main polymer components. Theseresults show that the blends prepared here have unique struc-tures that could be developed further to expand the applicationsof nanofibers.

Acknowledgments

This work was supported by the National Natural Science Foun-dation of China (50773009). This work was also supported in part

by Grant 08JC1400600 of Science and Technology Commission ofShanghai Municipality and UK-CHINA Joint Laboratory for Thera-peutic Textiles based in Donghua University and Biomedical TextileMaterials “111 Project”, Ministry of Education of PR China (No.B07024).

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