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Submicron Ion-Exchange Fibers ofPolystyrene and Styrene-Butadiene-Styrene Copolymer BlendsShu-Qin Feng a , Xin-Yuan Shen a & Ya-Li Ji aa State Key Laboratory for Modification of Chemical Fibers andPolymer Materials , Donghua University , Shanghai, ChinaAccepted author version posted online: 27 May 2011.Publishedonline: 25 Apr 2011.

To cite this article: Shu-Qin Feng , Xin-Yuan Shen & Ya-Li Ji (2011) Submicron Ion-Exchange Fibers ofPolystyrene and Styrene-Butadiene-Styrene Copolymer Blends, Journal of Macromolecular Science,Part B: Physics, 50:9, 1673-1681, DOI: 10.1080/00222348.2010.518883

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Journal of Macromolecular Science R©, Part B: Physics, 50:1673–1681, 2011Copyright © Taylor & Francis Group, LLCISSN: 0022-2348 print / 1525-609X onlineDOI: 10.1080/00222348.2010.518883

Submicron Ion-Exchange Fibers of Polystyrene andStyrene-Butadiene-Styrene Copolymer Blends

SHU-QIN FENG, XIN-YUAN SHEN, AND YA-LI JI

State Key Laboratory for Modification of Chemical Fibers and PolymerMaterials, Donghua University, Shanghai, China

In the present study, submicron ion-exchange fibers (IEFs) of polystyrene (PS) and itsblends with styrene-butadiene-styrene block copolymer (SBS) were prepared by electro-spinning and postsulfonating modification. Scanning electron microscopy (SEM) imagesshowed that the diameters of the fibers enlarged significantly after treatment and thesurfaces become rougher. Mechanical properties analysis showed that the electrospunfibers (EF) and the IEFs from PS/SBS blend fabrics possessed better mechanical perfor-mances than those from pure PS. The ion-exchange capacity (IEC) of 4.35 mmol/g andand copper ions (Cu2+) adsorption value of 3.08 mmol/g for IEFs from PS/SBS blendswere both higher than that of IEFs from pure PS and the conventional IEFs produced bycoating or grafting fibrous substrates with functionalized resins or monomers. Dynamicadsorption experiments were made to test the behavior of adsorption for Cu2+. Theresults of dynamic adsorption experiments with Cu2+ showed that the IEFs from PS/SBSwould quickly purify 3000 ml waste water containing Cu2+ (100 mg/L), and the removalrate for Cu2+ reached 96.5% even at the flow rate of 12 ml/min. The study providedan absorbent with a high dynamic adsorption capacity for removing Cu2+ from wastewater.

Keywords adsorption, composite, ion-exchange, polystyrene (PS), styrene-butadiene-styrene (SBS)

Introduction

Due to the advantages of simplification of preparation and fabrication, contact efficiencyand physical requirements of strength and dimension stability, ion-exchange fibers (IEFs)have been extensively studied.[1–5] The diameters of fibers via conventional technology arein the range of 5–25 µm,[3] which results in lower value in the specific surface area thannanofibers or micron fibers, and decreases in the potential binding capacity of adsorptivefelts made from the commercial fibers. Increasing the potential binding and available surfacearea by controlling the diameters of fibers in the range of sub-micron to nanometer shouldbe advantageous.

Electrospinning is an effective and economical process for producing fibers with aver-age diameters in the range of micrometers to nanometers.[6,7] Nanofibers produced by elec-trospinning have shown amazing characteristics, such as very large surface area-to-volume

Received 21 June 2009; accepted 11 July 2010.Address correspondence to X.-Y. Shen, State Key Laboratory for Modification of Chemical

Fibers and Polymer Materials, Donghua University, Shanghai 201620, China. E-mail: shenxy@dhu.edu.cn

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ratio and high porosity with very small pore size.[8] These characteristics of nanofibersresulted in an elevated permeability compared to commercial fibers, and provided the high-est dynamic adsorption capacity. Therefore, the electrospun nonwoven fibers have becomepromising materials in developing microfiltration systems, especially for the ion-exchangeapplications. For instance, Zhang and co-workers[3] prepared nanofibers whose availablesurface area was greatly increased, up to as much as two orders of magnitude.

PS-based materials are widely used as the base matrix for adsorbent beads and mem-branes in the ion-exchange processing industry. Furthermore, nanometer IEFs of PS havebeen prepared by An, Shin, and Chase,[5] although their mechanical properties were notgiven. The EFs of PS were fragile, which limited their extensive applications. So, it isnecessary to improve the mechanical properties of PS by adding other polymers such asstyrene–isoprene–styrene block copolymer (SIS), poly(methylmethacrylate) or SBS. SBSand SIS are typically highly flexible and elastic, consisting of soft and hard segments,[9,10]

which might contribute to the improvement of mechanical, optical and other properties ofPS. Considerable work has been carried out to improve PS fiber mechanical performancevia conventional processes though they have not been highly effective.[11–13] However, toour knowledge, the domains structure of PS and SBS blend EF and their IEFs have notbeen explored, which is the basis for this paper.

In the present work, pure PS and its blends with SBS were first electrospun intonanofibers, and then were converted into IEFs. The morphologies, ion-exchange capacity(IEC), Fourier transform infrared spectra (FTIR) and mechanical properties were investi-gated. The results indicated that IEFs from 80/20 weight ratio PS/SBS possessed highervalues of IEC and Cu2+ adsorption than IEFs of pure PS, and retained excellent mechanicalproperties even after being sulfonated.

Experimental

Materials

The SBS triblock copolymer used in this paper was obtained from Shell Chemical Co. (Kra-ton D1101) containing 31% polystyrene (PF) by weight, with total molecular weight (Mw)of 8 × 103; PS was supplied by Propilven C.A. with molecular weight (Mw) of 13 × 104;tetrahydrofuran (THF) and dimethylformamide (DMF) were obtained from Peking Chem-ical, China; concentrated sulfuric acid (98%), glacial acetic acid, and polyformaldehyde(Mw 8 ×103) were provided by Vas Chemicals, China.

Electrospinning Fibers

Pure PS and PS/SBS blends (80/20, w/w) were dissolved in a mixture of THF and DMF(80/20, v/v) with concentration 12 wt%, and stirred at room temperature for 12 h to maketransparent solutions. Each solution was kept in a 10 ml syringe with a capillary tip withinner diameter 0.7 mm. The applied electrostatic field power and the tip—to-collectordistance were adjusted according to the spinning state. After electrospinning, all the fibrousnonwoven membranes were collected from the aluminum foils, and dried at 100◦C in avacuum oven for two days.

Sulfonation and IEC Test

The electrospun nanofibers of PS and PS/SBS blends must be chemically activated to makethem perform as an ion exchange material. IEFs were formed using the following: 2 g oforiginal fibrous membranes were first put into a 100 ml bottle containing 30 ml of sulfuric

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Submicron IEF of Polystyrene and SBS Copolymer Blends 1675

acid (98%), 3 g of polyformaldehyde, and 10 ml of glacial acetic acid for crosslinking at50◦C for 6 h. Then 50 ml of sulfuric acid (98%) were added to sulfonate the fibers for 4 h at80◦C. Finally, the sulfonated products were diluted by different concentrations (70%, 50%,25%, and 5%, successively) of 98% sulfuric acid, followed by washing with deionizedwater until the flushing water was neutral, and dried in a vacuum oven for 24 h at 100◦Cto obtain the strongly acidic cation-exchange fibers. The details of the process have beenreported in an earlier publication.[14]

The IEC, representing the number of replaceable H+ ions per unit mass of the exchangematerial, was determined by backward titration experiments. The samples of sulfonatedfibrous membranes (0.2 g) were first put into 0.1 M HCl for 12 h at 25◦C to be convertedinto the H+ form. Then these samples were washed with deionized water and dried in anoven at 100◦C. These samples were then put into a flask with 20 ml of 0.5 M standardNaOH solution, and shaken for 12 h. The value of IEC was measured according to theliterature.[15]

Qw = (V0 − V1) × C/W. (1)

V0—the volume of HCl used in blank titration (ml)V1—the volume of HCl used in titration (ml)C—The concentration of HCl (mol/l)W—The weight of dry fibers (g)Qw—IEC (mmol/g)

Cu2+ Adsorption Tests

Batch kinetic tests for Cu2+ ions were investigated by contacting 0.31 g and 0.32 g ofIEF from PS/SBS and PS with 50 ml solution of CuCl2 (20 mg/l, pH = 4) at 25◦C undershaking. One milliliter of solution was collected at appropriate time intervals for metalion determination by using an atomic absorption spectrophotometer (Model 721W; OpticalInstrument Co., Shanghai, China). The quantity of metal ions adsorbed per gram of driedweight of IEFs (Qn) was calculated according to the literature.[16]

Batch dynamic analyses were carried out as follows: the solution (100 mg/l, pH =4) with the circulation flow rate of 12 ml/min by a peristaltic pump was put into an ion-exchange column with 40 mm diameter. Then 1.53 g dried adsorbent was added into thecolumn. The elution concentration of Cu2+ was determined by using the atomic absorptionspectrophotometer. The amount of absorption (Qn), the volume of absorption (Vd), and thede-copper rate (qr) were calculated according to the Equations (2), (3), and (4), respectively.

Qn = [C0V0 − CnVn −n∑

i=1

(i − 1)V (Ci−1 − Ci)]/W (2)

Vd = rt × T (3)

qr = (C0 − Cn)/C0 (4)

where C0 (mg/ml) and V0 (ml) are the initial Cu2+ ions concentrations and volume, Cn

(mg/ml) and Vn (ml) are the concentration and volume at predetermined time, V is thevolume of solution taken out at predetermined time (ml), W is the weight of the dried fibersused (g), rt is the flow rate, and T is the predetermined time.

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Characterization

The morphological images of EFs and IEFs of PS and PS/SBS blends were observed by aSEM JSM-6360LV instrument at a voltage of 15 KV. FTIR analysis was conducted on aNexus 670 spectrometer. Mechanical tests of IEF mats of PS/SBS blends and EFs of purePS were carried out with an Instron (1122) by a load cell of 10 N. A crosshead speed of 100mm/min was used for the specimen tests. Prior to mechanical tests, samples were cut intoa planar dimension of width × length = 5 mm × 30 mm (refer to ISO 527-1, ISO 527-3).

Results and Discussion

SEM Images of Fibers Before and After Sulfonation

Figure 1 presents the EFs and the IEFs morphologies of pure PS and 80/20 PS/SBS blends.The morphologies of the IEFs from 80/20 PS/SBS blends were significantly different fromthat of its EFs. The average diameter of IEFs increased sharply from 500 nm of EFs tothe order of 1000 nm; in addition, there were obvious grooves appearing on the surfaceof the IEFs, which became rough. The fibers of pure PS generated similar results. Inthe experimental process, we found many fractured fibers resulting from the sulfonationreaction, which will affect the mechanical properties of the mats.

Figure 1. SEM images of fibers before and after sulfonation: (a) EFs for 80/20 PS/SBS blends;(b) IEFs for 80/20 PS/SBS blends; (c) EFs for pure PS; and (d) IEFs for pure PS.

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Table 1Tensile properties of EFs and IEFs

EFs from IEFs fromSamples 80/20 PS/SBS 80/20 PS/SBS EFs from PS

Stain at break (%) 280 ± 20 95 ± 10 80 ± 5Ultimate tensile strength (MPa) 65 ± 5 20 ± 5 98 ± 5Young’s modulus (MPa) 20 ± 5 25 ± 5 60 ± 5

Stress Mechanical Performance of EFs and IEFs

Tensile properties of EF and IEF mats from pure PS and 80/20 PS/SBS blends were testedusing an Instron tester. Ultimate tensile strength, Young’s modulus, and the strain at breakare summarized in Table 1. Figure 2 present the stress–strain curves of EF and IEF mats.A general trend can be drawn from Table 1 and Fig. 2 that the mechanical performanceof the PS/SBS EFs after sulfonation decreased sharply, i.e., the ultimate tensile strength,and strain at break decreased from 65 ± 5 MPa, and 300 ± 20% for EFs to 20 ± 3 MPa,and 95 ± 10% for IEFs of the 80/20 PS/SBS blend. Mechanical properties of the IEFsdecreased mainly due to the sulfonation action, which caused oxidative degradation of thefiber materials. By comparison of the curves in Fig. 2, the values of the tensile strengthand Young’s modulus of the EF fibers decreased with incorporation SBS, i.e., from 98 ±5 MPa and 60 ± 5 MPa for EFs of pure PS to 65 ± 5 MPa and 20 ± 5 MPa for EFs of 80/20PS/SBS blends. On the contrary, the strain at break increased from 80 ± 10% for PS to 275 ±20% for PS/SBS ratio 80/20. Thus, the SBS in the blends increased the toughness. Thesamples for the IEFs from pure PS were damaged too heavily to measure their mechanical

Figure 2. Stress–strain curves of fibrous membranes: (a) EFs from pure PS; (b) EFs from 80/20PS/SBS; (c) IEFs from 80/20 PS/SBS; and (d) IEFs from PS.

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properties. Thus, the IEFs from PS/SBS blends possessed better mechanical stability thanthat from pure PS, but worse than EF of PS or the blend.

FTIR Spectra Analysis

To confirm the introduction of functional groups into the pure PS and PS/SBS 80/20 fabric,FTIR spectrum analysis was carried out. Figure 3 curves (a) and (b) (EFs of blend and PS,respectively) showed the following features: C–H of benzene ring (at the wave number of2900–3050 cm−1), and monosubstituted peaks of the benzene ring (at the wave numberof 759 cm−1). Figure 3, curves (c) and (d) (IEFs of blend and PS, respectively) showedthe following features: a strong peak near 1122 cm−1 that was the absorption peak of thesulfonated groups, and a stronger and broader absorption peak near 3400 cm−1, whichwas the O–H stretching vibration absorption peak. The disappearance of the benzene ringstretching vibration (from 1400 to 1600 cm−1) replaced by the O–H bending vibration(1500 cm−1 for PS/SBS blends and 1422 cm−1 for PS) indicated that most sulfonatedgroups were covalently attached to the benzene ring of styrene in the sulfonation reaction.The peaks near 1003–1040 cm−1 originated from the symmetrical stretching vibrationsof the sulfonated groups. The vibration peak situated at 1700 cm−1 was strengthenedby the induced sulfonated groups. Furthermore, the vibration peaks situated at 887 cm−1

characterized the para-substituted structure of the benzene ring. These demonstrated that thesulfonated groups were attached to the benzene ring of styrene in the sulfonation reaction.

IEC and Cu2+ Ions Adsorption

The IEC of IEFs was 4.35 mmol/g (80/20 PS/SBS blends sulfonated for 4 h), which washigher than the reported IEC of 1–4 mmol/g for the conventional IEFs produced by coating

Figure 3. FTIR spectra of the fibers: (a) EFs from 80/20 PS/SBS blends; (b) EFs from PS; (c) IEFsfrom PS; and (d) IEFs from 80/20 PS/SBS blends.

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Figure 4. Dynamic adsorption curves.

or grafting fibrous substrates with functionalized resins or monomers[17] and the IEFs ofpure PS (3.18 mmol/g). The IEC of IEF from the pure PS was lower (3.18 mmol/g)due to much more shrinkage and damage in the sulfonation process than for the PS/SBSblends. Furthermore, the literature[5] has reported that sulfonation could reduce the pore sizeand block pores between the fibers, which hindered sulfonated groups attaching onto thebenzene ring. So, the cation ion-exchange adsorbents of electrospun fibers (EF) accordingto the above approach had higher IEC than that of sulfonated polymer membranes andtextiles, which were obtained by radiation-induced grafting of styrene on the fibers withthe subsequent sulfonation of PF chains (0.5–3 mg/g).[18]

Dynamic analysis was carried out to examine the rate of adsorption of these IEFs. Theelution concentration was examined by an atomic absorption spectrophotometer at differenttimes for flow at the rate of 12 ml/min (Fig. 4). The elution concentration from the solutionscontaining different IEFs increased with increasing time. This means the removal rate ofthe fibers decreased over time. The removal rate of Cu2+ from PS/SBS (96.5%) was higherthan that from PS (94.7%) at the flow rate of 12 ml/min at 300 min. At the same time, theamounts of Cu2+ ion adsorption of IEFs (Qn) from 80/20 PS/SBS blends and pure PS were3.08 mmol/g and 2.76 mmol/g at 100 min, respectively. Thus, the IEFs from 80/20 PS/SBSblends had stronger absorptive capacity for Cu2+ ions than that of IEFs from pure PS. Theresults showed that the fibers from PS/SBS blends exhibited an excellent absorption ratewithin shorter time and good absorption capacity. This is partially because the IEFs fromPS/SBS blend had a higher specific surface area (986 m2/g) than that those from pure PS(924 m2/g).

Conclusions

Novel IEFs were produced by sulfonating the EFs of PS/SBS blends. The IEFs of PS/SBSblends had a good IEC value. The maximum IEC of IEFs from 80/20 PS/SBS blends,

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4.35 mmol/g, was higher than that of IEFs from pure PS (3.18 mmol/g). The static IEC ofPS/SBS blends and PS for Cu2+ adsorption were 3.08 mmol/g and 2.76 mmol/g, respec-tively. The IEFs from PS and PS/SBS both provided high dynamic adsorption capacitiesfor Cu2+ ions. FTIR showed that the IEFs from pure PS and PS/SBS blends had attachedsulfonated groups and the SEM images showed that the structure of the sulfonated fibershad changed greatly. The EFs and IEFs from PS/SBS blends exhibited better mechanicalproperties and mechanical stability than those from pure PS. Thus, the nanometer IEFsfrom PS/SBS blends have a potential application in adsorptive fields.

Acknowledgment

This research was financially supported by the State Key Laboratory for Modificationof Chemical Fibers and Polymer Materials (No. LZ0902).

References

1. Choi, J.; Lee, K.M.; Wycisk, R.; Pintauro, P.N.; Mather, P.T. Nanofiber network ion-exchangemembranes. Macromolecules 2008, 41, 4569–4572.

2. Matsumoto, H.; Wakamatsu, Y.; Minagawa, M.; Tanioka, A. Preparation of ion-exchange fiberfabrics by electrospray deposition. J. Colloid Interface Sci. 2006, 293, 143–150.

3. Zhang, L.F.; Menkhaus, T.J.; Fong, H. Fabrication and bioseparation studies of adsorptive mem-branes/felts made from electrospun cellulose acetate nanofibers. J. Membr. Sci. 2008, 319,176–184.

4. Pang, J.; Zhang, H.; Li, X.F.; Ren, D.F.; Jiang, Z.H. Low water swelling and high protonconducting sulfonated poly(arylene ether) with pendant sulfoalkyl groups for proton exchangemembranes. Macromol. Rapid Commun. 2007, 28, 2332–2338.

5. An, H.; Shin, C.; Chase, G.G. Ion exchanger using electrospun polystyrene nanofibers. J. Mem-brane Sci. 2006, 283, 84–87.

6. Subbiah, T.; Bhat, G.S.; Tock, R.W.; Parameswaran, S.; Ramkumar, S.S. Electrospinning ofnanofibers. J. Appl. Polym. Sci. 2005, 96, 557–569.

7. Murugan, R.; Ramakrishna, S.; Rao, K.P. Nanoporous hydroxy-carbonate apatite scaffold madeof natural bone. Materials Letters 2006, 60, 2844–2847.

8. Qian, Y.F.; Li, X.; Su, Y.; Ke, Q.; Mo, X.M. Fabrication and characterization of polycaprolac-tone/chlorophyllin sodium copper salt nanofibrous mats from 2,2,2-trifluoroethanol solution byelectrospinning. Iran Polym. J. 2008, 17, 373–378.

9. Zhang, H.; Wang, H.T.; Zhong, W.; Du, Q.G. A novel type of shape memory polymer blend andthe shape memory mechanism. Polymer 2009, 50, 1596–1601.

10. Feng, S.Q.; Shen, X.Y.; Fu, Z.Y.; Ji, Y.L. Studies on the electrospun submicron fibers of SiS andits mechanical properties. J. Appl. Polym. Sci. 2009, 114, 1580–1586.

11. Jelcic, T.; Holjevac-Grguric, T.; Rek, V. Mechanical properties and fractal morphology of high-impact polystyrene/poly(styrene-b-butadiene-b-styrene) blends. Polym. Degrad. Stab. 2005, 90,295–302.

12. Omonov, T.S.; Harrats, C.; Groeninckx, G.; Moldenaers, P. Anisotropy and instability of theco-continuous phase morphology in uncompatibilized and reactively compatibilized polypropy-lene/polystyrene blends. Polymer 2007, 48, 5289–5302.

13. Waldman, W.R.; De Paoli, M.A. Photodegradation of polypropylene/polystyrene blends: Styrene-butadiene-styrene compatibilisation effect. Polym. Degrad. Stab. 2008, 93, 273–280.

14. Kucera, F.; Jancar, J. Homogeneous and heterogeneous sulfonation of polymers: A review.Polym. Eng. Sci. 1998, 38, 783–792.

15. Hwang, G.J.; Ohya, H. Preparation of cation exchange membrane as a separator for the all-vanadium redox flow battery. J. Membr. Sci. 1996, 120, 55–67.

Dow

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16. Lee, S.W.; Bondar, Y.L.; Han, D.H. Synthesis of a cation-exchange fabric with sulfonate groups byradiation-induced graft copolymerization from binary monomer mixtures. React. Funct. Polym.2008, 68, 474–482.

17. Dominguez, L.; Benak, K.R.; Economy, J. Design of high efficiency polymeric cation exchangefibers. Polym. Adv. Technol. 2001, 12, 197–205.

18. Ding, Z.J.; Qi, L. Preparation of sheath-core bicomponent composite ion-exchange fibers andtheir properties. J. Appl. Polym. Sci. 2008, 109, 492–500.

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