manipulating the conductivity of carbon-black-filled immiscible polymer composites by insulating...

Manipulating the Conductivity of Carbon-Black-FilledImmiscible Polymer Composites byInsulating Nanoparticles

Bo Li, Xiang-Bin Xu, Zhong-Ming Li, Yin-Chun Song

College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering,Sichuan University, 127 YiHuanLu, NanYiDuan, Chengdu, 610065, Sichuan, People’s Republic of China

Received 2 October 2007; accepted 15 April 2008DOI 10.1002/app.28573Published online 8 September 2008 in Wiley InterScience (www.interscience.wiley.com).

ABSTRACT: The conductivity of an immiscible polymerblend system, microfibrillar conductive poly(ethylene ter-ephthalate) (PET)/polyethylene (PE) composite (MCPC)containing carbon black (CB), was changed by the additionof insulating CaCO3 nanoparticles. In MCPC, the PETforms microfibrils during processing and PE forms the ma-trix. The CB particles are selectively localized in the PETmicrofibrils. When the insulating CaCO3 nanoparticles areadded, they substitute for some of the conductive CB par-ticles and obstruct the electron paths. As a result, the resis-tivity of the MCPC can be tailored depending on the insu-lating filler content. The resistivity-insulating filler content

curve displays a sluggish postpercolation region (theregion immediately following the percolation region andin front of the equilibrium flat of the resistivity-filler con-tent curve), suggesting that the MCPC in the postpercola-tion region possesses an enhanced manufacturing repro-ducibility and a widened processing window. Thesefeatures are of crucial importance in making sensor mate-rials. � 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3073–3079, 2008

Key words: carbon; polymer matrix composites; percola-tion; electrical conductivity

INTRODUCTION

Manufacturing reproducibility, that is, the immunityof a material’s properties to fluctuation of both pro-cessing operations and parameters is of primary con-cern in producing conductive polymer composites(CPC). This is because the stable electrical propertiesof CPC materials give rise to the steady performanceof the resulting electrical devices.1,2 However, gener-ally, the reproducibility of CPCs is not satisfied espe-cially those in the practically valuable postpercola-tion region. The postpercolation region is defined asthe region immediately after the percolation regionof the resistivity-conductive filler loading curve andin front of the equilibrium flat, as shown in Figure 1.The resistivity of the samples in the postpercolationregion maintains high sensitivity to environmentalstimulation such as stress, gas, and heat due toimmaturity of the conductive network. Also, themoderate resistivity of the samples leaves enough

space for abrupt increase upon external stimula-tion.1–4 These samples can thus serve as candidatematerials for a variety of sensors such as chemicalsensor, self-regulating heater, overcurrent protector,and heat detector.1–8 However, for most CPC materi-als, this region is quite narrow, and after the percola-tion, the resistivity quickly transfers to an equilib-rium flat as the loading of conductive fillersincreases just a little. It has been well documentedthat the sharper this transition, the less reproducibil-ity the material has, because the resistivity of thesamples in this region can alter significantly eventhough a little vibration of processing parametersoccurs during processing.1 Thus, it is of great diffi-culties in making electrical devices with high preci-sion based on these CPCs. To the opposite, the moresluggish this transition of the postpercolation regionindicates the more enhanced reproducibility. Theobjective of this work is to slow down this transitionand further widen the postpercolation region bymanipulating the conductivity of the CPCs througha novel approach.

Up to now, only Zhang et al.1 have performed astudy on the postpercolation region to strengthenthe reproducibility of the CPC material. They usedthe selective distribution of carbon black (CB) in theimmiscible low-density polyethylene (PE)/ethylene-vinyl acetate copolymer blend. And a relatively flatportion was introduced in the postpercolation region

Correspondence to: Z.-M. Li ([email protected]).Contract grant sponsor: Nature Science Foundation of

China; contract grant number: 50573049.Contract grant sponsor: Programs for New Century

Excellent Talents in University; contract grant number:NCET-04-0871.

Journal of Applied Polymer Science, Vol. 110, 3073–3079 (2008)VVC 2008 Wiley Periodicals, Inc.

of the resistivity-CB-loading curve immediately afterthe first percolation region. The samples in this flatregion had a strengthened reproducibility and awidened processing window, because the flat meansthat the resistivity of the composite was, to someextent, immune to the CB content vibration. Furtherincreasing the CB content, another percolationbehavior could be observed in this material due tothe formation of conductive network at the interface.Although this two-step percolation method can leadto an adequate reproducibility, the introduction ofthe flat portion makes the conductivity unchange-able, which greatly limits the applications of suchkind of material.

In this study, a specific immiscible polymer blendsystem, microfibrillar poly(ethylene terephthalate)(PET)/PE composite, was studied. The PET micro-fibrils were formed through a slit die extrution-hotstretching-quenching process, whereas PE formedthe matrix phase. CB particles, the conductive filler,were selectively localized in the PET microfibrils toform a conductive network. By maintaining the vol-ume ratio of CB : PET : PE and adding an insulatingnanoparticle, nano-CaCO3, the resistivity of the con-ductive microfibrillar composite can be tailoreddepending on the insulating filler content. In the pre-vious work, it was well established that the surfacesof the CB-filled microfibrils played a key role in theconductivity of the composite.9–12 The electron pathscan only be conducted by effective connections, notonly interconnection of microfibrils, but also inter-connection of CB particles exposing on the surfacesof these microfibrils. And if the surface of fiber issmooth with well-covered plastics, the plastics coat-ing the CB particles hinder the transport of electrons.

Thus, only if the CB loading goes beyond the maxi-mum packing fraction (Fmax) of the CB particles inthe PET microfibrils, which is defined as the maxi-mum ratio of the volume of solids to the total vol-ume, the CB particles can migrate to the surfaces ofthe microfibrils and then conduct the electron path-way of the composite. Current strategy is based onthis specific conductive mechanism of the micro-fibrillar conductive polymer composite (MCPC).When nano-CaCO3 was added into the microfibrils,the CB particles on the microfibrils’ surfaces aregradually substituted by nano-CaCO3. And nano-CaCO3 particles play a similar role as the insulatingpolymer layer who obstructs the electron path way.Therefore, the gradually increased insulating area onthe microfibrils’ surfaces results in laggardlyincreased resistivity.

The choice of nano-CaCO3 is motivated by thefollowing reasons. First, both CB and insulatingparticle should have the preferential to localize inthe PET phase to guarantee the substitution strat-egy. The selective distribution of CB in PET phasewas warranted by our previous work. The fattyacid-treated surface of nano-CaCO3 guarantees itsbetter affinity to PET than PE. Second, it should bean insulating particle, which can obstruct conduc-tive path. Third, the size of nano-CaCO3 particleshould be similar to that of CB. The bigger particlesmight influence the formation of microfibrillar,whereas the smaller ones might not be big enoughto substitute the CB particles. Therefore, these prop-erties of nano-CaCO3 warrant the interaction of thetwo different particles inside the microfibrillarphase and further led to the controlled electricalproperties.

EXPERIMENTAL

Materials

The main materials are nano-CaCO3 (TB119, pur-chased from Inner Mongolia Mengxi Nano MaterialLimited-Liability Co., Neimenggu, China), CB (VXC-605, obtained from Cabot Co.), PET (a commercialgrade of textile polyester, kindly donated byLuoyang Petroleum Chemical Co., Luoyang, China),and PE (5000S, purchased from Daqing PetroleumChemical Co., Daqing, China). The specific physicalparameters of these materials have been reportedelsewhere,9 except nano-CaCO3. The nano-CaCO3

was treated by the fatty acid with a particle sizeranging from 20 to 30 nm, and a density rangingfrom 2.5 to 2.6 g/cm3. The solvent used to premixCB and nano-CaCO3 was ethanol (analyticallypure 99.7%) purchased from Kelong Co., Chengdu,China.

Figure 1 Regions of a volume resistivity-CB contentcurve, showing the definition of a postpercolation region.[Color figure can be viewed in the online issue, which isavailable at www.interscience.wiley.com.]

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Journal of Applied Polymer Science DOI 10.1002/app

Sample preparation

Premixing of the fillers

The fillers, CB and nano-CaCO3, were first mixed insolvent (ethanol) under ultrasonic water bath (808C),and mechanical stirring to fabricate homogeneous fil-ler mixture. The filler mixture together with ethanolwas stirred for 10 min in the three-necked bottlelocated in the ultrasonic water bath, and then theethanol was quickly evaporated under the aid of avacuum pump. The residue was further dried at thetemperature of 1208C for 24 h to remove the remain-ing solvent.

Preparation of masterbatch of microfibrillar phase

The filler mixture was then compounded with PETpellets in an internal mixer to fabricate the master-batch of the microfibrillar phase under the tempera-ture of 2708C. The PET pellets were first filled intothe internal mixer for 5 min. And then the filler mix-ture was put into the internal mixer for another5 min to fabricate the CB/nano-CaCO3/PET master-batch. The resulting agglomerates were furthercrashed into small particles.

Extrusion and hot stretching of the composites

The obtained CB/nano-CaCO3/PET particles and PEpellets were mixed in a single extruder (with a screwlength to diameter, L/D, of 30) and extruded througha slit die (15 mm wide, 2 mm high); the extrudedmelting strip was then stretched by a taking up de-vice with two pinching rolls to in situ form the CB/CaCO3/PET microfibrils. The stretched strip wasthen quenched in a cold water bath to stabilize themicrofibrillar morphology. The temperature profileused for the extruder was 190, 250, 280, and 2708Cfrom hopper to die, the roll temperature maintained408C, and the temperature of cold water bath is208C. The hot stretch ratio (the ratio of the area oftransverse section of slit die to the area of transversesection of strip) of the strip is calculated to be 11.8.

Compression molding of sample plaques

The resulting strips were cut into small pieces andthen compression molded into plaque samples withthe dimension of 2 3 100 3 100 mm for electricalproperty tests. The procedures were as follows: thematerials were first hot-pressed for 10 min under thepressure of 5 MPa and then cold-pressed for 5 minunder the same pressure. The temperature duringthe hot-pressing maintained 1508C, whereas the tem-perature for cold pressing is about 208C.

The volume ratio of CB, PET, and PE maintained11 : 75 : 241 throughout this work. By adding differ-ent fractions of nano-CaCO3, as shown in Table I, aseries of samples with different nano-CaCO3 con-tents were obtained from S1 to S6, having the CB/nano-CaCO3 volume ratios of 11 : 0, 11 : 7, 11 : 14,11 : 21, 11 : 28, and 11 : 35, respectively.

To observe the dispersion state of the particles, astrip of S3 was cryofractured in the liquid nitrogen.The cryofractured surface was sputter coated withgold particles and further photographed using aJEOL JSM-5900LV Scanning Electron Microscope(SEM). SEM was also used to observe the morphol-ogy of the dispersed phase after the PE matrix wasetched away by xylene, and the extruded strips ofsamples S1, S3, and S6 were involved in this obser-vation. The treatment was as follows: first, the sam-ple strips were put into hot xylene (1258C) for 15 h,and the solvent was refreshed every 5 h; second, thestrips were dried in the oven for 8 h at the tempera-ture of 808C. After the treatment, the microfibrilsexposed on the surface can be easily observed. Addi-tionally, for the samples that cannot maintain theshape of strip during this treatment, the residues inthe solvent were collected and dried for further test.

Resistivity testing

A two-point probe method was adopted to test theresistivity of the insulating samples, and a high re-sistivity meter model ZC-36 was applied with a volt-age of 100 V. For the samples with resistivity lowerthan 108 O 3 cm, a four-point method (ASTM D-991) was applied by using two DT9205 digital multi-meters and a voltage supply.

RESULT AND DISCUSSION

Results

SEM observation of MCPC

Figure 2 shows the cryofractured surface of sampleS3. A cross section of a fractured microfibril and apulled out tip of another microfibril embedded in

TABLE IThe Volume Ratio of Components and the Volume

Resistivities from S1 to S6

SampleCB/nano-CaCO3/

PET/PEVolume

resistivity (O 3 cm)

S1 11/0/75/241 2.44 3 104

S2 11/7/75/241 5.06 3 104

S3 11/14/75/241 2.05 3 105

S4 11/21/75/241 1.28 3 106

S5 11/28/75/241 1.40 3 1015

S6 11/35/75/241 1.96 3 1015

CONDUCTIVITY OF CB-FILLED IMMISCIBLE POLYMER COMPOSITES 3075


the smooth cryofractured surface of the PE matrixcan be seen. Almost all the particles, including bothCB particles and nano-CaCO3 particles, are localizedeither inside the microfibrils or on the surface ofmicrofibrils. Figure 3(a–c) shows the morphologyevolvement of the microfibrillar composite as a func-tion of the nano-CaCO3 content. In S1 [Fig. 3(a)],without nano-CaCO3, the well-defined fibrils withsmooth surfaces appear aligning almost in one direc-tion (flow direction) (the diameters of the microfi-brils have the range of 1–10 lm, with an averagelength of more than 150 lm). As the nano-CaCO3/CB volume ratio increases to 14 : 11(S3), shown inFigure 3(b), the fibrils become thicker and their sur-faces turn rougher. When the volume ratio of nano-CaCO3/CB reaches 35 : 11(S6) [Fig. 3(c)], PET cannotmaintain microfibrillar morphology, but assumesirregular domains. Figure 4 exhibits the detailedstructure information of microfibrils’ surfaces. Whencompared with Figure 4(a), more particles expose onthe surface of microfibril in Figure 4(b), along withthe increase of the nano-CaCO3 content from S1 toS3. Also, the microfibril in Figure 4(b) shows a muchcoarser surface, and due to the increase of the totalfiller content, and the shape of the microfibril is notas regular as that in Figure 4(a).

Resistivity of MCPC

Figure 5 depicts the volume resistivity of the com-posite as a function of nano-CaCO3 mass fraction inthe microfibril phase. It is interesting that the resis-tivity experiences a very slow increase from 2.44 3

104 to 1.28 3 106 O 3 cm, although the nano-CaCO3

in the microfibril phase (CB/nano-CaCO3/PET)greatly increases from 0 up to 30.81 wt %, corre-sponding to S1 and S4. Here, it should be noted that,

for the ease of plotting and comparison, here the vol-ume ratios in the microfibrillar phase were changedto the mass fractions. Further adding insulatingnano-CaCO3, however, the volume resistivityincrease rapidly, being analogous to a conventionalpercolation behavior in the filled CPC as a result ofchanging the conductive filler loading.10 In fact,although the insulating nano-CaCO3 loading

Figure 2 High magnification SEM micrograph of cryo-fractured surface of S3, in which volume ratio of CB/nano-CaCO3 equals 11 of 14.

Figure 3 SEM micrographs of microfibril morphologyevolvement in MCPC strips S1 (a), S3 (b), and S6 (c), pre-pared by etching away the PE matrix on the surface of theMCPC strips in hot xylene. The volume ratios of CB/nano-CaCO3 in S1, S3, and S6 are 11/0, 11/14, and 11/35,respectively.

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increases, the true CB content in the composite grad-ually decreases. However, in MCPC, both matrixpolymer and microfibrillar phase polymer constitutemost of the volume fraction, and even though thevolume ratio of microfibrillar phase (CB/nano-CaCO3/PET) changes a lot, the volume fraction ofCB in the composite changes only a little. As shownin the insert figure of Figure 5, a zig-zag drop of theresistivity can be seen as a function of the CB vol-ume fraction in the composite. The volume fractionof CB only ranges from 3.04 to 3.36 vol %.

Discussion

The earlier results show that the morphology evolve-ment of dispersed phase and the changing surfacecondition of microfibrils are both dependent on thenano-CaCO3 content. In the postpercolation region,by gradually increasing the nano-CaCO3 content,from 12.92 wt % (7.52 vol %) to 30.81 wt % (19.63vol %) in the microfibrillar phase, the morphologyand structure of the MCPC underwent a great

change. As a result, the resistivity of the samples canbe tailored, because it strongly depends on its mor-phology and structure, as discussed below. And asluggish transition and a widened processing win-dow based on nano-CaCO3 have thus been obtained.

Concerning the exact mechanism of this sluggishtransition, a series of factors have to be taken intoconsideration, including the selective distribution ofthe fillers, maximum packing fraction of microfibrilphase, and the specific conductive mechanism of theMCPC.

The selective distribution of both particles as testi-fied in Figure 2 is of crucial importance. The prefer-ential localization of CB particles in immiscible poly-mer blends has been reported in some literature.9–17

The key factors controlling the preferential distribu-tion of CB particles are the interfacial tensionbetween CB and polymer components, the viscosityof the polymer components, order of mixing, etc.According to the previous work,11 the CB particlesinteract strongly with the PET phase than with PEphase, with interfacial tensions of 5.89 and 13.1 mN/m, respectively. Moreover, the premixing of CB withPET phase strengthens CBs’ selective distribution inPET, because of the thermodynamic nature of par-ticles, which prevents CB from emigrating to PEphase. Combined these two factors mentioned ear-lier, the selective distribution of CB particles in PETphase is warranted. The similar condition happenedto nano-CaCO3. On one hand, the fatty acid surfaceof nano-CaCO3 can interact with ester group in thePET chain and thus enhance the interaction betweennano-CaCO3 and PET; on the other hand, the pre-mixing technology enhances the effect of selectivedistribution. In the high magnification SEM image,

Figure 4 High magnification SEM micrographs of surfaceof microfibrillar in sample strips, S1 (a), S3 (b), preparedby etching away the PE matrix on the surface of theMCPC strips in hot xylene.

Figure 5 Volume resistivity versus mass fraction of nano-CaCO3 in the microfibrillar phase (CB/nano-CaCO3/PET).Insert: volume resistivity versus volume fraction of CB inthe composite. [Color figure can be viewed in the onlineissue, which is available at www.interscience.wiley.com.]



as shown in Figure 2, the sharp contrast at the inter-face of microfibrillar phase and matrix proved thatall the particles were localized in the microfibrillarphase. Even though the particles were overloaded inthe microfibrillar phase, they did not further stepinto matrix, but chose to localize at the interface.

However, it is not warranted to say that CaCO3

particles without surface treatment could not dis-perse in the PET. The heterogeneous distribution ofparticles is dictated by the surface condition of par-ticles14 and the interfacial tension among particlesand different polymer phases.15 Therefore, withoutthe acid group on the surface of CaCO3 particles, thesurface condition as well as the interfacial tensionshould be analyzed to determine the distribution ofthese particles. However, this is of main concern ofthis manuscript. Further work will be done to figureout this problem.

Given that both CB and nano-CaCO3 prefer tolocalize in the PET phase, along with the increase offiller content, these two kinds of particles begin torival for limited space of the microfibrillar phase.When the fillers’ content reaches the maximum pack-ing fraction (Fmax), the fillers begin to migrate to theinterfaces. As shown in Figure 4(a,b), the surfacemorphology of microfibril is closely related to the fil-ler content, and the more filler content, the morecoarser the surface of microfibril. The conductivemechanism of MCPC9 indicates that the surface con-dition of the microfibril dictates the resistivity of thefinal samples. Along with the increasing nano-CaCO3 content, more particles are exposing on thesurface. In the postpercolation region, the CB par-ticles on the surface of microfibrils do exist, becausethe conductive pathway can only be conducted bythese particles. However, it is not clear whether CBparticles have the priority to localize on the surfaceor not, compared to nano-CaCO3 particles. If CB hasthe priority, although nano-CaCO3 prefers to localizein the center of the microfibril, an increased conduc-tivity is expected. Along with the increase of nano-CaCO3, more and more CB particles are forced tomigrate to the surface, and the increasing conductiveparticles on the surface increase the possibility ofeffective connection. However, the experimentalresults show the opposite tendency. This tendencyindicates that compared to nano-CaCO3, CB particlesdo not have that priority. The component of the filleron the surface is closely related to the original ratioof CB/nano-CaCO3. By increasing the content ofnano-CaCO3 gradually, nano-CaCO3 particles substi-tute the CB particles on the surface of microfibrilsstep by step. The insulating fillers on the surface ofmicrofibrils hold back the transport of electrons, andthus more and more electron paths are obstructedby insulating particles. Accordingly, the resistivity ofthe postpercolation region increase gradually.

Although there are few articles aiming at the resis-tivity control in the postpercolation region, severalmethods have been developed dealing with the per-colation region.5,18,19 The objectives of these methodsare to retard or even eliminate the percolationregion. And the physical and structural parametersof the conductive particles such as the dispersionstate, particle size, particle morphology, and the sur-face energy are key factors in controlling. For exam-ple, Ando and Takeuchy18 changed the dispersionstate of CB in the nature rubber, by grafting the CBparticles with methyl isobutyl ketone, ethylene gly-col macromer, styrene, and isopropenyl oxazoline,and a gradually reduced resistivity-CB loading curvecan be obtained. Also, Chan5 gained a similar resultby changing the particle size through a premixingmethod to fabricate compound filler with a largerparticle size. Sumita et al.19 addressed the impor-tance of surface energy of CB particles, and by fluo-rinating the surfaces of CB particles, both theoreticalprediction and experimental result showed a re-tarded curve. However, the pretreatments of par-ticles in these methods increase the cost of materials,consume a lot of energy, and jeopardize the conduc-tivity of the final product. Moreover, these methodsmainly deal with the percolation region, which haslittle application potential in sensor material for itshigh resistivity. To the opposite, the insulating fillerused in our method is much cheaper, and the energyof pretreatment is also saved. Also, our method hasstrong maneuverability, because the two steps pro-cessing can be accomplished by traditional process-ing methods and the ratio of CB, nano-CaCO3, andPET can be easily controlled, because the content ofnano-CaCO3 varies over a wide range.

It is also interesting that the percolation behaviorof this CB and CaCO3-filled MCPC may be not acontent dependent percolation, but a morphology-dependent one. On one hand, the percolation regionof CB content is too narrow, only 0.06 vol %, asshown in the insert figure of Figure 5, which hasnever been reported in any reference. The efficiencyof CB as a conductive filler is not as high as that byincreasing such a little amount, the resistivity canreduce so greatly. On the other hand, as shown inFigure 3, the morphology of microfibrillar phasechanges greatly when the percolation happens.Increasing the filler content leads to the breakdownof microfibrillar morphology and then the amor-phous blocks with much surface covered with nano-CaCO3 cannot form a throughout conductive net-work. This limitation implies that if the microfibrillarphase can be maintained to a higher filler loading, awider postpercolation region is expected.

The breakdown of microfibrillar morphology iscaused by the greatly increased viscosity of PETphase. The fibrillation capability of the PET in the

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composite depends not only on the elongationalflow field during hot stretching, but also on the par-ticle loading.10,11 In this work, the volume ratio ofCB/PET/PE was fixed as 11 : 75 : 241, and the shareof nano-CaCO3 varied from 0 to 35. The keepingincrease of nano-CaCO3 will fill in the limited spaceof dispersed phase (PET), which makes the viscosityof PET higher and higher, verified by the fact thatthe surface of PET microfibrillar turns coarse as theincrease of nano-CaCO3, as shown in Figure 4(a,b).When the viscosity of the PET reaches beyond a crit-ical value, the PET phase cannot be deformed intomicrofibrillar morphology, but amorphous blocks.

CONCLUSIONS

Using an insulating nanoparticle, the electrical prop-erties of MCPC in the postpercolation region can beeffectively tailored, and the postpercolation can begreatly widened. Thus, this CPC material can serveas a candidate for multifunctional sensors withenhanced reproducibility. This is a method with lowcost and good accessibility. Furthermore, this is anovel idea on the property control of conductive im-miscible polymer blend. The future issues will beconcentrated on the applications of this material andoptimizing the controllability of this method.

The authors thank Mr. Zhu Li from Analytical and TestingCenter of Sichuan University for his help in the SEMobservation.

References

1. Zhang, M. Q.; Yu, G.; Zeng, H. M.; Zhang, H. B.; Hou, Y. H.Macromolecules 1998, 31, 6724.

2. Sisk, B. C.; Lewis, N. S. Langmuir 2006, 22, 7928.

3. Narkis, M.; Ram, A.; Flashner, F. Polym Eng Sci 1978, 18, 649.

4. Narkis, M.; Ram, A.; Flashner, F. J Appl Polym Sci 1978, 22, 1163.

5. Chan, C. M. Polym Eng Sci 1996, 36, 495.

6. Lonergan, M. C.; Severin, E. J.; Doleman, B. J.; Beaber, S. A.;Grubbs, R. H.; Lewis, N. S. Chem Mater 1996, 8, 2298.

7. Segal, E.; Tchoudakov, R.; Mironi-Harpaz, I.; Narkis, M.; Sieg-mann, A. Polym Int 2005, 54, 1065.

8. Chen, J. H.; Tsubokawa, N. Polym Adv Technol 2000, 11,101.

9. Xu, X. B.; Li, Z. M.; Yang, M. B.; Jiang, S.; Huang, R. Carbon2005, 43, 1479.

10. Li, Z. M.; Xu, X. B.; Lu, A.; Shen, K. Z.; Huang, R.; Yang, M. B.Carbon 2004, 42, 428.

11. Xu, X. B.; Li, Z. M.; Yu, R. Z.; Lu, A.; Yang, M. B.; Huang, R.Macromol Mater Eng 2004, 289, 568.

12. Xu, X. B.; Li, Z. M.; Dai, K.; Yang, M. B. Appl Phys Lett 2006,89, 032105.

13. Sumita, M.; Sakata, K.; Ami, S.; Miyasaka, K.; Nakagawa, H.Polym Bull 1991, 25, 265.

14. Wu, G. Z.; Asai, S.; Sumita, M.; Yui, H. Macromolecules 2002,35, 945.

15. Wu, S. Polymer Interface and Adhesion; New York: MarcelDekker, 1982; p 98.

16. Khan, C.; Kubht, J. J Appl Polym Sci 1975; 19: 831.

17. Gubbels, F.; Jerome, R.; Teyssie, Ph.; Vanlathem, E.; Deltour,R.; Calderone, A.; Parente, V.; Bredas, J. L. Macromolecules1994, 27, 1972.

18. Ando, N.; Takeuchi, M. Thin Solid Films 1998, 334, 182.

19. Katada, A.; Buys, Y. F.; Tominaga, Y.; Asai, S.; Sumita, M.Colloid Polym Sci 2005, 283, 367.



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