8
Transaction F: NanotechnologyVol. 17, No. 1, pp. 35{42c Sharif University of Technology, June 2010
Invited Paper
Di�usion of Ionic Liquids into Elastomer/CarbonNanotubes Composites and Tensile
Mechanical Properties of Resulting Materials
B. Likozar1
Abstract. In order to ensure better elastomer/functionalized Multi-Walled Carbon Nanotube(MWCNT) compatibility and to enhance the dispersion, a series of ionic liquids has been tested in regardto an improved interaction between elastomer and functionalized carbon nanotubes. We found that inthe presence of especially one ionic liquid, namely, 1-butyl-1-methylpyrrolidinium tetra uoroborate, forthe hydrogenated nitrile elastomer, used as basic polymer, a 1.83 fold increase of elongation at break wasachieved with only � 7 wt% ionic liquid loading. At this low concentration of ionic liquid the samplecan be stretched up to 508% without mechanical failure. The use of this ionic liquid additionally resultsin high tensile strength (21.4 MPa) at low concentration (< 7 wt %) of ionic liquid. Energy-dispersiveX-ray spectrometric scanning electron microscopy con�rmed the homogeneous distribution of ionic liquidsamong nitrile elastomer chains by showing uniform signal belonging to uorine in ionic liquid, when thedi�usion process of ionic liquid into nanocomposites was long enough (> 48 h) during the ionic liquidabsorption measurements. Transmission electron microscopic images con�rmed the good dispersion of theMWCNT along with the exfoliated structure of the CNTs in the rubber matrix.
Keywords: Nanocomposites; Functionalized multi-walled carbon nanotubes; Ionic liquid; Elastomer;Polymer; Di�usion coe�cient.
INTRODUCTION
Tetra uoroborate, hexa uorophosphate and bis(tri- uoromethylsulfonyl)imide room temperature ionicliquids containing substituted imidazolium andpyrrolidinium cations, particularly 1-ethyl-3-methyl-imidazolium (EMIm+), have received extensiveattention over the past 30 years [1]. Angell et al. wereone of the �rst to describe a new class of polymerelectrolytes for secondary lithium batteries termed\polymer-in-salt" which are rubbery solid electrolytespossessing high ionic conductivities [2].
Recently, several studies were published inves-tigating nitrile elastomer (NBR)/ionic liquid com-posites, because of the fact that NBR is generallyresistant to oil, fuel and other chemicals. Its re-silience makes NBR a useful material for several
1. Faculty of Chemistry and Chemical Technology, University ofLjubljana, A�sker�ceva cesta 5, 1000 Ljubljana, Slovenia. E-mail: [email protected]
Received 13 May 2010; accepted 30 August 2010
applications. Moreover, NBR's ability to with-stand a wide range of temperatures makes it anideal material especially for extreme applications.Among others, Marwanta et al. discovered improvedionic conductivity of NBR/ionic liquid composites [3],while Cho et al. developed a solid state actuatorbased on the poly(3,4-ethylenedioxythiophene) (PE-DOT)/NBR/ionic liquid system [4]. The �rst groupconsequently revealed that NBR/Li(CF3SO2)2N com-posites with added imidazolium-type zwitterion posseseven more improved ionic conductivity [5], while thesecond group discovered an electro-active conductingpolymer actuator based on solid polymer electrolyte [6]consisting of NBR and room temperature ionic liquidsand high ionic conductivity and mechanical strength ofsolid polymer electrolytes based on NBR/ionic liquidand its application to an electrochemical actuator [7].The group of Cho et al., subsequently, more thor-oughly examined various aspects of the developedsolid state actuator based on the PEDOT/NBR/ionicliquid system, speci�cally, the e�ect of anion size ofimidazolium ionic liquid [8] and the characteristics of
36 B. Likozar
PEDOT/NBR/PEDOT solid actuator depending onthe NBR polarity [9]. Parallel to this, they also ex-amined a dry type conducting polymer actuator basedon polypyrrole-NBR/ionic liquid system [10]. Themechanical properties of the mentioned composites,however, were not optimal, as these properties of thematrix material (NBR) compound were not consideredin detail.
Elastomer/carbon nanotubes present themselvesas an ideal solution to address this topic. How-ever, studies of the subject are scarce. Silicone elas-tomer/carbon nanotubes/ionic liquid composites wereused to produce a rubberlike stretchable matrix usingelastic conductors [11]. A blend of styrene-butadienerubber and polybutadiene rubber in combination withcarbon nanotubes and ionic liquids was studied to de-termine coupling activity of ionic liquids between dieneelastomers and multi-walled carbon nanotubes [12].
Therefore, in this study, the absorption anddi�usion of di�erent ionic liquids in hydrogenated NBR(HNBR) reinforced with hydroxyl-functionalized multi-walled carbon nanotubes (MWCNT-OH) was exam-ined, HNBR exhibiting superior performance in com-parison to NBR, whereas MWCNT-OH were utilized toprovide excellent mechanical properties of the matrixmaterial [13,14]. Tensile mechanical properties of theresulting materials were studied to determine the e�ectof the applied ionic liquids on functional properties.
EXPERIMENTAL
Hydrogenated nitrile rubber (HNBR) bulk was a giftfrom Erwin Mach Gummitechnik, GmbH. HNBRwas used as received. HNBR with the acrylonitrilecontent of 34 wt% (con�rmed by nitrogen analyzer)and the double bond content of 0.9 mol% (con�rmedby infrared (IR) spectroscopy) was used in this study,because this is the best composition for its optimalphysical properties, compromising strength andelasticity. The Mooney viscosity of HNBR was 70 at100�C. 1-ethyl-3-methylimidazolium tetra uoroborate(EMImBF4) (98 mol%, colourless to orange liquid),1-butyl-3-methylimidazolium tetra uoroborate (BMImBF4) (99 mol%, colourless to orange liquid), 1-butyl-1-methylpyrrolidinium tetra uoroborate (BMPyBF4) (99 mol%, colourless to yellowish solid), 1-ethyl-3-methylimidazolium hexa uorophosphate (EMImPF6) (99 mol%, colourless to yellowish solid),1-butyl-3-methylimidazolium hexa uorophosphate(BMImPF6) (99 mol%, colourless to orange liquid),1-butyl-1-methylpyrrolidinium hexa uorophosphate(BMPyPF6) (99 mol%, colourless to yellowish solid),1-ethyl-3-methylimidazolium bis(tri uoromethylsulfo-nyl)imide (EMImTFSI) (99 mol%, colourless toorange liquid), 1-butyl-3-methylimidazolium bis(tri- uoromethylsulfonyl)imide (BMImTFSI) (99 mol%,
colourless to orange liquid), and 1-butyl-1-methyl-pyrrolidinium bis(tri uoromethylsulfonyl)imide (BMPyTFSI) (99 mol%, colourless to orange liquid),purchased from IoLiTec Ionic Liquids Technologies,GmbH, were used as received. The structure of theionic liquids was con�rmed by Nuclear MagneticResonance (NMR) and IR spectroscopy, and ispresented in Figure 1. The mentioned ionic liquidswere used in this study, because they should providegood electrical properties.
Samples with the thickness of 1 mm were obtainedby pressing the compounds, reinforced with mixed-into-rubber hydroxy-functionalized multi-walled car-bon nanotubes (MWCNT-OH) (purchased from CheapTubes, Inc., 90 wt% purity, con�rmed by Ramanspectroscopy), between steel plates at 180�C for 4.5min to obtain cross-linked structure. Just after HNBRhad cooled down to the room temperature (1 day)to prevent later solvent evaporation due to increasedtemperature, following vulcanization, composites con-taining the ionic liquids were prepared, so that HNBRsamples were immersed into the excessive amount ofthe ionic liquids (HNBR/ionic liquid weight ratios of atleast 1/10) in borosilicate glass tubes for di�erent times(presented in Table 1) so that the ionic liquids di�usedinto the samples, while the ionic liquids were dissolvedin chloroform (purchased from J.T.Baker, Inc., 99.5wt% purity) in the weight ratio of 1/1, and stirredto obtain homogeneous solutions. Chloroform was
Figure 1. Ionic liquids applied to HNBR/MWCNT-OHcomposites: (a) EMImBF4; (b) BMImBF4; (c) BMPyBF4;(d) EMImPF6; (e) BMImPF6; (f) BMPyPF6; (g)EMImTFSI; (h) BMImTFSI; (i) BMPyTFSI.
Elastomer/Carbon Nanotubes/Ionic Liquids Composites 37
Table 1. Immersion times of HNBR/MWCNT-OHcomposites in di�erent ionic liquids.
Ionic Liquid Time (h)
EMImBF4 / / / 48
BMImBF4 / / / 48
BMPyBF4 6 12 24 48
EMImPF6 / / / 48
BMImPF6 / / / 48
BMPyPF6 / / / 48
EMImTFSI 6 12 24 48
BMImTFSI / / / 48
BMPyTFSI 6 12 24 48
used in this study, because it enhanced the di�usionof the ionic liquids into the samples and dissolvedthe ionic liquids, which were in the solid state atthe room temperature. After solvent removal, thesamples were dried at the room temperature for 5days to obtain solvent-free composites. The samples'dimensions increased, depending on the uptake of anionic liquid and the solvent, and then decreased afterthe solvent removal to between 100 and 110% of theoriginal values.
The tensile test (mechanical properties - globalsample stress and strain measurement) of vulcanizedHNBR/MWCNT-OH/ionic liquid composite sheets'dumbbell samples with the dimensions of 1�4�80 mmwas performed using MTS Polymer Test System (MTSSystems Corporation, Inc., USA) testing machine atthe room temperature and in the displacement rangefrom 0 to 100 mm. The maximum load was not setand elongation rate was 500 mm/min. The sampleswere put between two steel �xtures with 2 cm space inbetween.
The morphology of vulcanized HNBR/MWCNT-OH/ionic liquid composite sheet samples with thedimensions of 1�4�4 mm was observed using scanningelectron microscopy (SEM) (cut samples' surfaces)with Zeiss DSM 962 (Carl Zeiss, AG, Germany) micro-scope at the room temperature and in vacuum, usingthe acceleration voltage of 15 kV. INCAPentaFETx3energy-dispersive X-ray spectrometer (EDX) (OxfordInstruments, PLC, UK), attached to SEM, was usedto determine the chemical composition of the samples.The samples were �xed onto sample holder usingconductive carbon cement, sputtered with carbon, andpainted on the side with silver paste. Transmissionelectron microscopy (TEM) observations were per-formed with FEI Tecnai 12 (USA) microscope equippedwith the embedded CCD camera at the accelerationvoltage of 120 kV (the room temperature- and the cryo-cut samples with the thickness of 85 nm and 120-150nm, respectively).
RESULTS AND DISCUSSION
HNBR/MWCNT-OH composites were subjected toionic liquids, which di�used in the latter. Uptake wasmonitored at di�erent times as presented in Table 1.Figure 2 shows the experimentally measured averageionic liquid weight fraction in composites as a functionof time for BMPyBF4, EMImTFSI and BMPyTFSI. Itmay be observed that these ionic liquids exhibit fastinitial di�usion when the bulk of HNBR/MWCNT-OHmay still be considered semi-in�nite medium that iswithout any ionic liquid present, whereas after 24 ha clear equilibration process is exhibited, ionic liquidsin HNBR/MWCNT-OH composites steadily reachingequilibrium absorption values alongside with di�usionrate decrease. Due to this conventional Fickean be-havior, the di�usion was described using Fick's secondlaw:
@CIL@t
= DIL;C@2CIL@x2 ; (1)
With accompanying initial and boundary conditions:
CIL = 0; t = 0; x � 0;
CIL = CIL;EQ; t > 0; x = L;
@CIL@x
= 0; t > 0; x = 0: (2)
In Equations 1 and 2, CIL (wt %) represents theconcentration of ionic liquid at position x and attime t, x = L corresponding to composite surfaceand x = 0 corresponding to composite middle (ap-proximately 1 mm). It has to be noted that the
Figure 2. Average ionic liquid weight fractions inHNBR/MWCNT-OH composites obtained fromexperiment (symbols) and model (lines) as a function ofimmersion time.
38 B. Likozar
HNBR/MWCNT-OH composite specimens had slabgeometry and consequently the di�usion proceededin x, as well as y and z directions. The lattertwo characteristic dimensions, however, were relativelylarger than L, thus the concentration gradients weremuch lower and subsequently y and z di�usion uxescould have been neglected. DIL;C is the di�usioncoe�cient of ionic liquid into HNBR/MWCNT-OHcomposite, while CIL;EQ represents the equilibriumuptake of ionic liquid. The solution of Equation 1,using the initial/boundary conditions of Equation 2,may be expressed by the following relationship:
CIL =CIL;EQ
1� 2
�
1Xn=0
(�1)n
n+ 1=2
exp���2(n+ 1=2)2DIL;Ct
L2
�cos��(n+ 1=2)
� xL
���: (3)
As the average weight fraction was determined exper-imentally, Equation 3 had to be averaged along thedi�usion direction axis x as well, speci�cally:
hCILi =1L
LZ0
CILdx: (4)
This resulted in the volume-averaged weight fraction< CIL > as expressed by the following equation:
hCILi =CIL;EQ
1� 2
�2
1Xn=0
1(n+ 1=2)2
exp���2(n+ 1=2)2DIL;Ct
L2
��: (5)
This equation was �tted to the experimental datapresented in Figure 2. The �rst 100 terms of thein�nite series in Equation 5 proved to provide a goodenough level of accuracy. DIL;C and CIL;EQ werevaried as �tting parameters initially the latter assumingapproximated values of 10�9 m2/s and < CIL > at48 h of immersion, respectively. These two param-eters were regressed minimizing the sum of squaresof di�erences between experimentally determined andmodel predicted < CIL > values. Model predictions of< CIL > for BMPyBF4, EMImTFSI and BMPyTFSIare presented in Figure 2 as well, and it may beobserved that the correspondence is quite good. Thedetermined CIL;EQ were 14.6, 11.8, and 16.5 wt % forBMPyBF4, EMImTFSI, and BMPyTFSI, respectively,and these values agree quite well with experimentallydetermined average weight fractions of ionic liquidsat 48 h immersion time presented in Table 2, that is
Table 2. Uptake of di�erent ionic liquids by HNBR/MWCNT-OH composites at the immersion time of 48 h.
Ionic Liquid Uptake (wt %)
EMImBF4 1.8
BMImBF4 2.6
BMPyBF4 14.4
EMImPF6 4.6
BMImPF6 4.7
BMPyPF6 6.4
EMImTFSI 11.4
BMImTFSI 17.6
BMPyTFSI 16.8
14.4, 11.4, and 16.8 wt % for BMPyBF4, EMImTFSI,and BMPyTFSI, respectively. The estimated di�usioncoe�cients were 1:10�10�11 m2/s, 4:61�10�12 m2/s,and 1:11 � 10�11 m2/s for BMPyBF4, EMImTFSI,and BMPyTFSI, respectively. These values would im-ply the cation predominantly determines the di�usionbehavior, the di�usion coe�cients of BMPyBF4 andBMPyTFSI being almost the same. An interesting factis that the di�usion coe�cient of EMImTFSI is 2.4-fold lower than the other two mentioned, even thoughEMImTFSI itself is smaller in size, as ordinarily smallercomponent would be expected to di�use faster in agiven medium. This may be explained through thepolarity of ionic liquids, speci�cally, BMPyBF4 andBMPyTFSI, that is BMPy+ cation has butyl groupbonded to ionic liquid, which apparently increases thecompatibility with the non-polar segments of HNBRchains and overall enhances mass transfer as comparedto ethyl group bonded in EMIm+ cation. This willalso be discussed in the continuation of this paper. Itis also interesting that anion, even as large as TFSI�,does not have a noticeable impact on the di�usion rate.Quite the opposite, the equilibrium uptake seems to behigher for BMPyTFSI as for BMPyBF4, even thoughTFSI� anion is substantially larger than BF�4 . Thisonce again may be explained through compatibility;TFSI� anion being in this case more compatible withthe polar acrylonitrile segments of HNBR chains.
As only volume-averaged weight fractions of ionicliquids are presented in Figure 2, position- and time-dependency of BMPyBF4 weight fraction is demon-strated in Figure 3. As shown the weight fractionis initially zero throughout the HNBR/MWCNT-OHcomposite, it then step-wise increases to CIL;EQ atthe composite surface (x=L = 1), whereas it decreasesmore gradually in the bulk material, especially in thecomposite center (x=L = 0). Worth noticing is thefact that after 48 h, the distribution of CIL is rela-tively uniform and close to CIL;EQ, which could havealready been expected from volume-averaged weightfractions in Figure 2. This is quite positive observation
Elastomer/Carbon Nanotubes/Ionic Liquids Composites 39
Figure 3. Model predicted BMPyBF4 weight fractions inHNBR/MWCNT-OH composites as a function ofimmersion time and position in composites (x=L = 1 forthe composite surface; x=L = 0 for the composite center).
as a homogeneous HNBR/MWCNT-OH composite isexpected to be obtained within 48 h, at least as far asionic liquid distribution is concerned. A question was,whether this could be validated experimentally and ifthe same applies for the distribution MWCNT-OH.
Therefore transmission and scanning electron mi-croscopy of the cross-section of composites was exam-ined and is presented in Figure 4. Carbon nanotubes,obtained by catalytic chemical vapor deposition, wereused as received. When the carbon nanotubes weredirectly mixed with HNBR in a mixer, their dispersionwas good as evidenced by the absence of any largeMWCNT aggregates and any large isolated amount ofrubber matrix without carbon nanotubes as �ller inFigure 4a. That is, melt compounding gives a �ne anduniform dispersion of carbon nanotubes in HNBR, asshown in Figure 4a. It can be seen that the cross-section dimensions of the dispersed carbon nanotubes'aggregates are quite small (tens of nanometers) with afew tens of micrometers-scale length. This causes somedi�culties in clearly observing the diameter and thelength of nanotubes with TEM at once, especially indistinguishing the length of individual carbon tubes.The interface between the carbon tubes and HNBR isgreatly improved by the functionalization of nanotubesin the case of HNBR/MWCNT-OH nanocomposites.This de�nitely enhanced the tensile strength of car-bon nanotubes composite. The dispersion quality ofcarbon nanotubes in the mentioned rubber matrix istruly quite satisfactory. Moreover, Figure 4b showsthe detected ionic liquid homogeneity by observing uorine signal of the latter utilizing SEM-EDX analysisof HNBR/MWCNT-OH/BMPyTFSI composite after48 h immersion time. This validates the calculateduniformity of ionic liquid within the composite bulk.
Figure 4. TEM microgram (a) and SEM combined with uorine SEM-EDX micrograms (b) forHNBR/MWCNT-OH/BMPyTFSI composites.
Analogous observations were obtained for all compos-ites and HNBR/MWCNT-OH/BMPyTFSI compositeis presented due to a relatively high ionic liquid uptakeand consequently strong uorine signal.
Uptake of di�erent ionic liquids by HNBR/MWCNT-OH composites at the immersion time of48 h is presented in Table 2. The �ndings observedfor BMPyBF4, EMImTFSI and BMPyTFSI shouldgenerally be valid for other ionic liquids as well. Thisis indeed the case as equilibrium ionic liquid uptakemore or less increased with decreasing cation polarity,the latter decreasing EMIm+ < BMIm+ < BMPy+.Analogously as before the anion polarity determineduptake as well, nevertheless, not as much regularly asfor cations. Subsequently, the uptake of all ionic liquidscontaining TFSI� is much higher than the comparableones containing BF�4 and PF�6 and may in turn alsobe explained through compatibility with nitrile groupsin polar HNBR segments. This led us to believe thatthe equilibrium uptake of an ionic liquid of the typeswhich were utilized in this study may be in some waycorrelated to molecular mass, either of the ionic liquidor the positive/negative ion, constituting the ionicliquid. Therefore, several relatively simple expressionswere tested to correlate either molecular mass with
40 B. Likozar
equilibrium uptake and power-law dependence provedto give the best results in terms of agreement followedonly by high-degree polynomials, which nonethelessrequire more parameters for a correlation. Therefore,a power-law was chosen as the best option consideringboth number of adaptable parameters and correlationagreement. The correlated experimental data and thecorrelation itself are presented in Figure 5. Agreementis indeed good, whereas the exponent value is normallynegative if the components of the same polarity, yet dif-ferent molecular mass, are considered. In our case thepolarity was intrinsically connected to molecular massand it has to be noted that although the agreementwas good in our case, this may not necessarily apply toother classes of ionic liquids. The ionic liquids appliedin this study, however, are one of the most widespreadones and thus the practical value of the correlation stillstands.
The mechanical properties of HNBR/MWCNT-OH composites immersed in ionic liquids for di�erenttimes were tested in tensile mode in order to determinefunctional properties of the composites. Characteristicproperties are presented in Figures 6 and 7 and Table 3.As evident from the mentioned �gures and tabletailor-made composite properties may be obtained withelongation at break as high as 508%, tensile strengthas high as 24.3 MPa, and elastic modulus rangingto 16.6 MPa. These values are superb. However,they may not be obtained simultaneously but certaincompromises have to be agreed on. From Figure 6bit may be seen that HNBR/MWCNT-OH compositeswith BMPyBF4, EMImTFSI and BMPyTFSI all ex-hibit a minimum of tensile strength at 24, 12, and6 h of immersion time, respectively, for the last twoionic liquids corresponding to minima in elongation
Figure 5. Equilibrium ionic liquid weight fractions inHNBR/MWCNT-OH composites obtained fromexperiment (symbols) and correlation (lines) as a functionof ionic liquid molecular mass.
Figure 6. Elongation at break and tensile strength ofHNBR/MWCNT-OH/ionic liquid composites as afunction of immersion time.
at break. These two ionic liquids also exhibit elasticmodulus minima, however, not at the same ionic liquiduptake, but at lower (EMImTFSI, immersion time6 h) or higher (BMPyTFSI, immersion time 24 h)one, as demonstrated in Figure 7. All these propertieswere visibly improving with immersion time increasingfrom 12 h on for EMImTFSI and from 24 h on forBMPyTFSI. The same did not apply for BMPyBF4composites as the latter exhibit a maximum in elon-gation at break corresponding to minimum elasticmodulus at 6 h immersion time, whereas the minimumin tensile strength ensued at 24 h immersion time. Thisparticular type of behavior may be attributed to specialinteractions among ionic liquid and carbon nanotubedomains [12], which result both in distinct relaxationprocesses of various domains as well as degradationprocesses and defect accumulation being speci�c to a
Elastomer/Carbon Nanotubes/Ionic Liquids Composites 41
Table 3. Tensile mechanical properties of HNBR/MWCNT-OH/ionic liquid composites.
Ionic LiquidTensile Strength
(MPa)Elongation at Break
(%)Elastic Modulus
(MPa)
EMImBF4 23.4 216 16.6
BMImBF4 23.4 223 16.1
BMPyBF4 19.2 193 14.2
EMImPF6 23.3 227 16.2
BMImPF6 23.4 280 15.6
BMPyPF6 19.1 185 15.3
EMImTFSI 21.4 251 13.0
BMImTFSI 17.8 250 12.0
BMPyTFSI 19.9 378 10.6
Figure 7. Elastic modulus of HNBR/MWCNT-OH/ionicliquid composites as a function of immersion time.
particular HNBR/MWCNT-OH/ionic liquid composi-tion. From Table 3, the most promising compositesare de�nitely the ones containing either BMImPF6 orBMPyTFSI; the �rst one having second best elongationat break, the best tensile strength and relatively highelastic modulus among composites immersed in ionicliquids for 48 h. The second with BMPyTFSI has lowerelastic modulus and slightly lower tensile strength aswell, nevertheless has by far the greatest elongationat break. For all the applied ionic liquids electricaland ionic conductivity was studied extensively [3-10],so this aspect of functional properties is not question-able. Other functional properties, e.g. thermal andwear properties, were demonstrated to be excellent aswell [13,14]. Not as many correlations may be made be-tween ionic liquid structure and mechanical propertiesas tensile strength and elongation at break in Table3 do not seem to exhibit a particular trend as far ascation and anion type are concerned. Elastic modulus,nonetheless seems to decrease with decreasing cation
polarity, which may be explained by the fact thatdecreasing polarity causes higher equilibrium absorp-tion of ionic liquid (as discussed before) which in turnresults in plasticizing e�ect of the ionic liquid; the lattersoftening the reinforced matrix. All in all, the choice ofparticular ionic liquid and nanocomposite compositionresulting from the choice of suitable immersion time arestrongly dependent on the �nal application in question,whether there should be a demand for a sti�, rigidmaterial intended for low deformations or, on the otherhand, a material which should withstand large strains,but is not necessarily as sti� as the one mentionedbefore.
CONCLUSIONS
Functionalized multi-walled carbon nanotubes alongwith an ionic liquid 1-butyl-1-methylpyrrolidiniumtetra uoroborate (BMPyBF4) provide a strong levelof reinforcement to an HNBR rubber matrix. Thechemical coupling between carbon nanotubes and rub-ber chains by BMPyBF4 is evidenced by mechanicalproperties such as elongation at break and elasticmodulus. It was found that BMPyBF4 probably playsa major role in enhancing the level of dispersion, andthus superior mechanical properties, such as elongationat break and tensile strength, have been achieved.The morphology of the nanocomposite, especially theCNT dispersion was examined, whereas the ionic liquidhomogeneity was detected by observing uorine signalof the latter utilizing SEM-EDX.
ACKNOWLEDGMENTS
This work was supported by the Austrian ResearchPromotion Agency Structural Programme (Kplus -Competence Centers Programme). The author alsoacknowledges the support of Dr. Zoltan Major.
42 B. Likozar
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BIOGRAPHY
Blau Likozar (born in Kranj, Slovenia in 1981) earnedhis Ph.D. in Chemical Engineering at the Faculty ofChemistry and Chemical Technology of the Universityof Ljubljana (Slovenia). After his Ph.D. in 2008 andthe postdoctoral research at the University of Leoben(Austria), he became an assistant professor of chemicalengineering at the Chair of Chemical, Biochemicaland Environmental Engineering. His research is fo-cused on synthesis and characterization of elastomernanocomposites containing carbon nanotubes and theproduction of biodiesel using microalgae.
