The aim of this study is to analyze the changes in the structure, thermal properties and electrophysical behavior of polyethylene glycol doped with multiwalled carbon nanotubes. The differential scanning calorimetry and electrical conductivity methods were used to study influence of doping multiwalled carbon NTs on the properties of polyethylene glycol of different molecular weights, Mw (PEG-400, PEG-1000, PEG-
10000). Dependencies of the polymers degree of crystallinity and temperature behavior of conductivity on the concentration of NTs were researched. The obtained data indicates a strong influence of the molecular weight of PEG on the spatial distribution of NTs and electrical conductivity of researched systems

Klepko, V.V.

Lebovka, N.I.

Melnyk, I.A.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 4 No 2, 02NNSA13(6pp) (2015) 
 
 
2304-1862/2015/4(2)02NNSA13(6) 02NNSA13-1  2015 Sumy State University 
Effect of Molecular Weight on the Properties of Polyethyleneglycols Doped with  
Multiwalled Carbon Nanotubes 
 
I.A. Melnyk1,*, V.V. Klepko2, N.I. Lebovka3 
 
1 Taras Shevchenko National University of Kyiv, The Faculty of Physics, 2, acad. Glushkov pr, 03022 Kyiv, Ukraine  
2 Institute of Macromolecular Chemistry NAS of Ukraine 48, Kharkivske road, 02160 Kiev, Ukraine 
3 Biocolloidal Chemistry Institute named after F. D. Ovcharenko, National Academy of Sciences of Ukraine, 42, 
acad. Vernadsky bulvare, Kyiv 03142, Ukraine 
 
(Received 01 June; published online 29 August 2015) 
 
The aim of this study is to analyze the changes in the structure, thermal properties and electrophysical 
behavior of polyethylene glycol doped with multiwalled carbon nanotubes. The differential scanning calo-
rimetry and electrical conductivity methods were used to study influence of doping multiwalled carbon NTs 
on the properties of polyethylene glycol of different molecular weights, Mw (PEG-400, PEG-1000, PEG-
10000). Dependencies of the polymers degree of crystallinity and temperature behavior of conductivity on 
the concentration of NTs were researched. The obtained data indicates a strong influence of the molecular 
weight of PEG on the spatial distribution of NTs and electrical conductivity of researched systems.  
 
Keywords: multiwalled carbon nanotubes, polyethylene glycol, DSC, degree of crystallinity, electrical 
conductivity 
 
 PACS numbers: 65.80. – g, 73.63.Fg 
 
 
                                                          
* Irinamelnik1989@gmail.com 
1. INTRODUCTION 
 
Polyethylene glycol (PEG, H-[-OCH2CH2-]n-OH) is a 
promising material due to its own high solvation capac-
ity. The electrolytes, created on its base, can be used in 
various electrochemical devices, in lithium batteries, 
flexible electrochromic displays, etc. [1]. However, an 
ionic conductivity of these systems need to be strength-
ened. The solution to this problem is doping electrolyte 
based on PEG with carbon nanotubes (NTs) [2, 3]. De-
tailed studies of the structure and properties of poly-
ethylene glycol doped with NTs have been conducted 
previously [4-6]. The aim of this study is to analyze the 
changes in the structure, thermal properties and elec-
trophysical behavior of PEG doped with multiwalled 
carbon nanotubes. 
 
2. MATERIALS AND METHODS 
 
The multiwalled carbon nanotubes (MWCNT) may 
be imagined as the combination of the concentric cylin-
ders. In principle, the number of multiple rolled layers 
in MWCNTs is not restricted, however, commonly they 
contain 10 – 20 layers. The interlayer distance in 
MWCNTs is close to the distance between graphene 
layers in graphite (≈ 0.34 nm). MWCNTs were pre-
pared from ethylene using the chemical vapour deposi-
tion (CVD) method (NV Spetsmash Ltd., Kyiv, 
Ukraine) with FeAlMo as a catalyst. They were further 
treated by alkaline and acidic solutions and washed by 
distilled water until reaching the distilled water pH 
values in the filtrate. The typical outer diameter d of 
MWCNTs was  ≈ 30-50 nm, their length l was ≈ 5-10 
μm and mean aspect ratio was a=l/d ≈ 100-300. 
Polyethylene glycol (PEG) is the typical polyglycol 
with many different applications. The term glycol is 
reserved for low molecular weight polymer while the 
term oxide is used for high molecular weight polymer. 
At room temperature PEGs with a molecular weight, 
Mw, up to 600 are fluids, PEGs with a molecular weight 
between 800 and 2000 are pasty, and with molecular 
weights above 3000 the PEGs are solids. Degree of PEG 
crystallinity, , increases with increasing of molecular 
weight. PEG is a hydrophilic nonionic polymer and it 
has the remarkable solubility in water. 
The melting temperature, Tm, and melting enthal-
py, Hm, were measured with a TA Q2000 Instrument 
(TA Instruments Ltd. West Sussex, England) in the 
regime of heating from 273 K to 333 K at the heating 
rate, Vh, of 2 K/min. The samples (20-30 mg) were 
packed in the aluminium pans. The fractional crystal-
linity of polymer composites, DSC, was calculated as: 
 
 


 0
m
DSC
m
H
H
 (1) 
 
where Hm is the heat of melting of the composite 
under investigation and Hm0 is the heat of melting of 
100% crystalline polymers (=188.4 J/g for PEG [7]). 
The electrical conductivity, , was estimated by the 
inductance, capacitance and resistance (LCR) meter 
819 Instek, 12 Hz–100 kHz (Instek America Corp. Chi-
no, CA, USA) in a cell equipped with two horizontal 
platinum electrodes (diameter of 12 mm, inter-
electrode space of 0.5 mm). The applied external volt-
age was U = 1.275V. The measuring frequency of 10 
kHz was chosen in order to avoid polarization effects on 
the electrodes and the electric field-induced asymmet-
ric redistribution of MWNTs between the electrodes. 
The optical microscopy images were obtained using 
an OI-3 UHL 4.2 microscope (LOMO, Russia). The 
microscope detector unit was interfaced with a digital 
camera and a personal computer. 
 I.A. MELNYK, V.V. KLEPKO, N.I. LEBOVKA PROC. NAP 4, 02NNSA13 (2015) 
 
 
02NNSA13-2 
3. RESULTS 
 
3.1 Microstructure 
 
Fig. 1 shows examples of microscopic images for 
samples PEG-400, PEG-1000, PEG-10000 on fixed-NTs 
concentration (0.1 %wt) and various times of ultrasonic 
dispersion. Studies have shown that increasing the 
dispersion time contributed to the «loosening» of NTs 
aggregates and improving uniformity of its spatial 
distribution. In addition, most dense aggregates were 
observed for PEG-400, while for PEG-10000 recorded 
more uniform distribution of NT on sample volume.  
 
 
 
Fig. 1 – Microstructure  of samples PEG-400 (a), PEG-1000 
(b), PEG-10000 (c) doped with NTs (0.1 %wt) in case of two 
different time of dispersion: left column - 2 min., right column 
- 10 min. of ultrasonic dispersion. The sample temperature 
was 338 K 
 
3.2 Thermal characteristics 
 
The examples of the estimated from the DSC data 
thermal characteristics (temperature, Tm, and enthalpy, 
ΔНm, of melting) and the degree of crystallinity, χDSC, for 
the samples are presented in the Table 1. 
The increase of crystallinity of PEG-400 in the con-
centration 1.5 % wt MWCNTs was explained by the 
fact that the nanotubes serve as the centres of hetero-
geneous nucleation of crystalline phase. 
With increase of the concentration of these centres 
the crystallization rate and degree of crystallinity of 
the polymer matrix are also increase. As the result a 
more perfect structure of the polymer with a higher 
degree of crystallinity was realized. At Cn0.2 % wt the 
processes of thermal motions of macromolecular chains 
are restricted owing to the presence of well-developed 
surface of nanotubes. The presence of steric barriers for 
macromolecules of PEG-400 results in losing of their 
mobility and thus in ability to form a crystalline struc-
ture. This behavior is also observed for PEG-1000. 
However, for highly crystalline PEG-10000 increase in 
the concentration of NT leads only to a decrease in the 
degree of crystallinity. This can be explained by the 
destruction of highly crystalline structure due to the 
introduction of MWCNTs. 
 
Table 1 – Thermal characteristics (temperature, Tm, and 
enthalpy, ΔНm, of melting) and the degree of crystallinity, 
χDSC, obtained for the samples PEG-400, PEG-1000, PEG-
10000 +MWCNTs from the DSC method 
 
  Tm±0.1, K ΔHm, J/g χDSC, % 
 
PEG 400 
0%NТ 248,7 44,21±2,2 23,4±1,1 
0,2% NТ 245,8 38,3 ±1,9 20,3±1,0 
1,5% NТ 249,6 52,03 ±2,6 27,6±1,5 
 
PEG 1000 
0% NТ 310,5 135,1 ±4,1 71,7±2,1 
0,2% NТ 308,8 122,9 ±3,6 65,2±1,9 
1,5% NТ 308,9 133,9 ±4,1 71±2,1 
 
PEG 10000 
0% NТ 335,7 170 ±3,4 90,2±1,8 
0,2% NТ 336,4 161,3 ±3,2 85,6±1,6 
1,5% NТ 335,9 158,1 ±3,1 83,92±1,6 
 
3.3 Percolation behaviour of electrical conduc-
tivity 
 
Doping of PEG by nanotubes noticeably affect the 
system electrophysical behaviour. Figure 2 presents 
temperature dependencies of electrical conductivity of 
PEG with different molecular weight undoped (dashed 
lines) and doped (solid lines) with 0.1 % wt MWCNTs. 
For PEG 400 sample no significant hysteresis in the 
heating-cooling cycle was observed. However, for PEG 
1000 and PEG 10000 samples the hysteresis loop in the 
heating-cooling cycle in the vicinity of the melting-
freezing temperatures was observed. 
In general, with increasing molecular weight of the 
polymer, Mw, and increasing the degree of its crystallinity 
a significant decrease in electrical conductivity was ob-
served. This effect can be attributed to a decrease in elec-
trical charge mobility with increase of the crystallinity. 
 
 
 
Fig. 2 – Electrical conductivity, , versus the temperature, T, 
for different undoped PEG (dashed lines, open symbols) and 
PEG doped (solid lines, closed symbols) with 0.1 % wt 
MWCNTs 
 EFFECT OF MOLECULAR WEIGHT ON THE PROPERTIES… PROC. NAP 4, 02NNSA13 (2015) 
 
 
02NNSA13-3 
The rather unexpected effect was observed in temper-
ature dependence of electrical conductivity for the PEG 
10000 sample. In the vicinity of the melting-freezing 
temperatures the electrical conductivity passed through a 
minimum. The negative temperature coefficient of con-
ductivity in the vicinity of 290-325 K can be explained by 
the effect of the temperature on the conductive pathways 
in a polymer matrix in this temperature interval. 
Fig. 3 shows the concentration dependence of the re-
duced conductivity σ / σ0 (σ0 = σ (C = 0)) for the three 
samples. Analysis of the figure 3 shows that the relative 
contribution of nanotubes in composites electrical con-
ductivity for polymers of different molecular weights are 
similar, i.e. in the selected coordinate system all three 
depending's fit into a single universal curve. 
 
 
 
Fig. 3 – Relative electrical conductivity σ / σ0 (σ0 = σ (C = 0)) 
versus the concentration of MWCNTs, C, for PEG with differ-
ent molecular weight at a temperature T = 363K. The solid 
line corresponds to the percolation approximation using equa-
tion (2). In the inset - the dependence of σ versus molecular 
weight, Mw, at C = 1% wt. 
The percolation theory predicts the following scaling 
law for the concentration dependence of electrical conduc-
tivity [8]: 
 
  ,tp pС С C C     (2) 
 
where t is a critical conductivity exponent, and Cp is a 
percolation concentration of the conductive filler. Analy-
sis of experimental data in Fig. 3, allows us to get the 
critical exponent of electrical conductivity t = 1.5 ± 0.15. 
 
4. CONCLUSION 
 
Thus, analysis of the results shows that with in-
creasing molecular weight of polyethylene glycol and 
increasing its degree of crystallinity,  the spatial distri-
bution of the nanotubes becomes more homogeneous, 
but with greatly reduced of electrical conductivity of 
such systems. 
Note that the found value of the critical conductivi-
ty exponent, t is smaller than classic value t ≈ 2, the 
random percolation in three-dimensional systems [8]. 
In our opinion, this could mean some (such as planar) 
character of ordering NTs in studied PEG-systems. The 
significant decrease in sample conductivity was ob-
served even at much higher concentrations of 
MWCNTs above the percolation threshold (see inset to 
Fig. 3). 
 
 
 
 
 
 
 
 
 
REFERENCES 
 
1. A.M. Christie, S.J. Lilley, E. Staunton, Y.G. Andreev, P.G. 
Bruce, Nature 433, 50(2005).  
2. E.A. Lysenkov, Y.P. Gomza, V.V. Klepko, Polym. J. 32, 
223 (2010). 
3. E.A. Lysenkov, J.P. Gomza, V.V. Davidenko, V.V. Klepko, 
Phys. Condens. Macromol. Syst. 14, 15 (2010). 
4. A.A. Lysenkov, V.V Klepko, Y.V. Yakovlev, Nanostructural 
Mater. Sci. 3, 46 (2013). 
5. E.A. Lysenkov, Y.P. Gomza, V.V. Klepko, Y.A. Kunitsky, 
Phys. Chem. Solid State 11, 361 (2010). 
6. N.I. Lebovka, E.A. Lysenkov, A.I. Goncharuk, Y.P. Gomza, 
V.V. Klepko, Y.P. Boiko, J. Compos. Mater. 45, 2555 
(2011). 
7. B. Wunderlich, Macromolecular Physics (Academic Press: 
New York: 1973).  
8. D. Stauffer, A. Aharony, Introduction to Percolation 
Theory, 2nd ed. (London: Taylor & Francis: 1992). 
 


English

Effect of Molecular Weight on the Properties of Polyethyleneglycols Doped with Multiwalled Carbon Nanotubes

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 4 No 2, 02NNSA13(6pp) (2015)   2304-1862/2015/4(2)02NNSA13(6) 02NNSA13-1  2015 Sumy State University Effect of Molecular Weight on the Properties of Polyethyleneglycols Doped with  Multiwalled Carbon Nanotubes  I.A. Melnyk1,*, V.V. Klepko2, N.I. Lebovka3  1 Taras Shevchenko National University of Kyiv, The Faculty of Physics, 2, acad. Glushkov pr, 03022 Kyiv, Ukraine  2 Institute of Macromolecular Chemistry NAS of Ukraine 48, Kharkivske road, 02160 Kiev, Ukraine 3 Biocolloidal Chemistry Institute named after F. D. Ovcharenko, National Academy of Sciences of Ukraine, 42, acad. Vernadsky bulvare, Kyiv 03142, Ukraine  (Received 01 June; published online 29 August 2015)  The aim of this study is to analyze the changes in the structure, thermal properties and electrophysical behavior of polyethylene glycol doped with multiwalled carbon nanotubes. The differential scanning calo-rimetry and electrical conductivity methods were used to study influence of doping multiwalled carbon NTs on the properties of polyethylene glycol of different molecular weights, Mw (PEG-400, PEG-1000, PEG-10000). Dependencies of the polymers degree of crystallinity and temperature behavior of conductivity on the concentration of NTs were researched. The obtained data indicates a strong influence of the molecular weight of PEG on the spatial distribution of NTs and electrical conductivity of researched systems.   Keywords: multiwalled carbon nanotubes, polyethylene glycol, DSC, degree of crystallinity, electrical conductivity   PACS numbers: 65.80. – g, 73.63.Fg                                                             * Irinamelnik1989@gmail.com 1. INTRODUCTION  Polyethylene glycol (PEG, H-[-OCH2CH2-]n-OH) is a promising material due to its own high solvation capac-ity. The electrolytes, created on its base, can be used in various electrochemical devices, in lithium batteries, flexible electrochromic displays, etc. [1]. However, an ionic conductivity of these systems need to be strength-ened. The solution to this problem is doping electrolyte based on PEG with carbon nanotubes (NTs) [2, 3]. De-tailed studies of the structure and properties of poly-ethylene glycol doped with NTs have been conducted previously [4-6]. The aim of this study is to analyze the changes in the structure, thermal properties and elec-trophysical behavior of PEG doped with multiwalled carbon nanotubes.  2. MATERIALS AND METHODS  The multiwalled carbon nanotubes (MWCNT) may be imagined as the combination of the concentric cylin-ders. In principle, the number of multiple rolled layers in MWCNTs is not restricted, however, commonly they contain 10 – 20 layers. The interlayer distance in MWCNTs is close to the distance between graphene layers in graphite (≈ 0.34 nm). MWCNTs were pre-pared from ethylene using the chemical vapour deposi-tion (CVD) method (NV Spetsmash Ltd., Kyiv, Ukraine) with FeAlMo as a catalyst. They were further treated by alkaline and acidic solutions and washed by distilled water until reaching the distilled water pH values in the filtrate. The typical outer diameter d of MWCNTs was  ≈ 30-50 nm, their length l was ≈ 5-10 μm and mean aspect ratio was a=l/d ≈ 100-300. Polyethylene glycol (PEG) is the typical polyglycol with many different applications. The term glycol is reserved for low molecular weight polymer while the term oxide is used for high molecular weight polymer. At room temperature PEGs with a molecular weight, Mw, up to 600 are fluids, PEGs with a molecular weight between 800 and 2000 are pasty, and with molecular weights above 3000 the PEGs are solids. Degree of PEG crystallinity, , increases with increasing of molecular weight. PEG is a hydrophilic nonionic polymer and it has the remarkable solubility in water. The melting temperature, Tm, and melting enthal-py, Hm, were measured with a TA Q2000 Instrument (TA Instruments Ltd. West Sussex, England) in the regime of heating from 273 K to 333 K at the heating rate, Vh, of 2 K/min. The samples (20-30 mg) were packed in the aluminium pans. The fractional crystal-linity of polymer composites, DSC, was calculated as:    0mDSCmHH (1)  where Hm is the heat of melting of the composite under investigation and Hm0 is the heat of melting of 100% crystalline polymers (=188.4 J/g for PEG [7]). The electrical conductivity, , was estimated by the inductance, capacitance and resistance (LCR) meter 819 Instek, 12 Hz–100 kHz (Instek America Corp. Chi-no, CA, USA) in a cell equipped with two horizontal platinum electrodes (diameter of 12 mm, inter-electrode space of 0.5 mm). The applied external volt-age was U = 1.275V. The measuring frequency of 10 kHz was chosen in order to avoid polarization effects on the electrodes and the electric field-induced asymmet-ric redistribution of MWNTs between the electrodes. The optical microscopy images were obtained using an OI-3 UHL 4.2 microscope (LOMO, Russia). The microscope detector unit was interfaced with a digital camera and a personal computer.  I.A. MELNYK, V.V. KLEPKO, N.I. LEBOVKA PROC. NAP 4, 02NNSA13 (2015)   02NNSA13-2 3. RESULTS  3.1 Microstructure  Fig. 1 shows examples of microscopic images for samples PEG-400, PEG-1000, PEG-10000 on fixed-NTs concentration (0.1 %wt) and various times of ultrasonic dispersion. Studies have shown that increasing the dispersion time contributed to the «loosening» of NTs aggregates and improving uniformity of its spatial distribution. In addition, most dense aggregates were observed for PEG-400, while for PEG-10000 recorded more uniform distribution of NT on sample volume.     Fig. 1 – Microstructure  of samples PEG-400 (a), PEG-1000 (b), PEG-10000 (c) doped with NTs (0.1 %wt) in case of two different time of dispersion: left column - 2 min., right column - 10 min. of ultrasonic dispersion. The sample temperature was 338 K  3.2 Thermal characteristics  The examples of the estimated from the DSC data thermal characteristics (temperature, Tm, and enthalpy, ΔНm, of melting) and the degree of crystallinity, χDSC, for the samples are presented in the Table 1. The increase of crystallinity of PEG-400 in the con-centration 1.5 % wt MWCNTs was explained by the fact that the nanotubes serve as the centres of hetero-geneous nucleation of crystalline phase. With increase of the concentration of these centres the crystallization rate and degree of crystallinity of the polymer matrix are also increase. As the result a more perfect structure of the polymer with a higher degree of crystallinity was realized. At Cn0.2 % wt the processes of thermal motions of macromolecular chains are restricted owing to the presence of well-developed surface of nanotubes. The presence of steric barriers for macromolecules of PEG-400 results in losing of their mobility and thus in ability to form a crystalline struc-ture. This behavior is also observed for PEG-1000. However, for highly crystalline PEG-10000 increase in the concentration of NT leads only to a decrease in the degree of crystallinity. This can be explained by the destruction of highly crystalline structure due to the introduction of MWCNTs.  Table 1 – Thermal characteristics (temperature, Tm, and enthalpy, ΔНm, of melting) and the degree of crystallinity, χDSC, obtained for the samples PEG-400, PEG-1000, PEG-10000 +MWCNTs from the DSC method    Tm±0.1, K ΔHm, J/g χDSC, %  PEG 400 0%NТ 248,7 44,21±2,2 23,4±1,1 0,2% NТ 245,8 38,3 ±1,9 20,3±1,0 1,5% NТ 249,6 52,03 ±2,6 27,6±1,5  PEG 1000 0% NТ 310,5 135,1 ±4,1 71,7±2,1 0,2% NТ 308,8 122,9 ±3,6 65,2±1,9 1,5% NТ 308,9 133,9 ±4,1 71±2,1  PEG 10000 0% NТ 335,7 170 ±3,4 90,2±1,8 0,2% NТ 336,4 161,3 ±3,2 85,6±1,6 1,5% NТ 335,9 158,1 ±3,1 83,92±1,6  3.3 Percolation behaviour of electrical conduc-tivity  Doping of PEG by nanotubes noticeably affect the system electrophysical behaviour. Figure 2 presents temperature dependencies of electrical conductivity of PEG with different molecular weight undoped (dashed lines) and doped (solid lines) with 0.1 % wt MWCNTs. For PEG 400 sample no significant hysteresis in the heating-cooling cycle was observed. However, for PEG 1000 and PEG 10000 samples the hysteresis loop in the heating-cooling cycle in the vicinity of the melting-freezing temperatures was observed. In general, with increasing molecular weight of the polymer, Mw, and increasing the degree of its crystallinity a significant decrease in electrical conductivity was ob-served. This effect can be attributed to a decrease in elec-trical charge mobility with increase of the crystallinity.    Fig. 2 – Electrical conductivity, , versus the temperature, T, for different undoped PEG (dashed lines, open symbols) and PEG doped (solid lines, closed symbols) with 0.1 % wt MWCNTs  EFFECT OF MOLECULAR WEIGHT ON THE PROPERTIES… PROC. NAP 4, 02NNSA13 (2015)   02NNSA13-3 The rather unexpected effect was observed in temper-ature dependence of electrical conductivity for the PEG 10000 sample. In the vicinity of the melting-freezing temperatures the electrical conductivity passed through a minimum. The negative temperature coefficient of con-ductivity in the vicinity of 290-325 K can be explained by the effect of the temperature on the conductive pathways in a polymer matrix in this temperature interval. Fig. 3 shows the concentration dependence of the re-duced conductivity σ / σ0 (σ0 = σ (C = 0)) for the three samples. Analysis of the figure 3 shows that the relative contribution of nanotubes in composites electrical con-ductivity for polymers of different molecular weights are similar, i.e. in the selected coordinate system all three depending's fit into a single universal curve.    Fig. 3 – Relative electrical conductivity σ / σ0 (σ0 = σ (C = 0)) versus the concentration of MWCNTs, C, for PEG with differ-ent molecular weight at a temperature T = 363K. The solid line corresponds to the percolation approximation using equa-tion (2). In the inset - the dependence of σ versus molecular weight, Mw, at C = 1% wt. The percolation theory predicts the following scaling law for the concentration dependence of electrical conduc-tivity [8]:    ,tp pС С C C     (2)  where t is a critical conductivity exponent, and Cp is a percolation concentration of the conductive filler. Analy-sis of experimental data in Fig. 3, allows us to get the critical exponent of electrical conductivity t = 1.5 ± 0.15.  4. CONCLUSION  Thus, analysis of the results shows that with in-creasing molecular weight of polyethylene glycol and increasing its degree of crystallinity,  the spatial distri-bution of the nanotubes becomes more homogeneous, but with greatly reduced of electrical conductivity of such systems. Note that the found value of the critical conductivi-ty exponent, t is smaller than classic value t ≈ 2, the random percolation in three-dimensional systems [8]. In our opinion, this could mean some (such as planar) character of ordering NTs in studied PEG-systems. The significant decrease in sample conductivity was ob-served even at much higher concentrations of MWCNTs above the percolation threshold (see inset to Fig. 3).          REFERENCES  1. A.M. Christie, S.J. Lilley, E. Staunton, Y.G. Andreev, P.G. Bruce, Nature 433, 50(2005).  2. E.A. Lysenkov, Y.P. Gomza, V.V. Klepko, Polym. J. 32, 223 (2010). 3. E.A. Lysenkov, J.P. Gomza, V.V. Davidenko, V.V. Klepko, Phys. Condens. Macromol. Syst. 14, 15 (2010). 4. A.A. Lysenkov, V.V Klepko, Y.V. Yakovlev, Nanostructural Mater. Sci. 3, 46 (2013). 5. E.A. Lysenkov, Y.P. Gomza, V.V. Klepko, Y.A. Kunitsky, Phys. Chem. Solid State 11, 361 (2010). 6. N.I. Lebovka, E.A. Lysenkov, A.I. Goncharuk, Y.P. Gomza, V.V. Klepko, Y.P. Boiko, J. Compos. Mater. 45, 2555 (2011). 7. B. Wunderlich, Macromolecular Physics (Academic Press: New York: 1973).  8. D. Stauffer, A. Aharony, Introduction to Percolation Theory, 2nd ed. (London: Taylor & Francis: 1992).  

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Effect of Molecular Weight on the Properties of Polyethyleneglycols Doped with Multiwalled Carbon Nanotubes

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