O. MUKBANIANI et al.: COMB-TYPE FLUORINE-CONTAINING POLYMER ELECTROLYTE MEMBRANES
33–39
COMB-TYPE FLUORINE-CONTAINING POLYMER
ELECTROLYTE MEMBRANES
FLUOR VSEBUJO^E POLIMERNE ELEKTROLITNE MEMBRANE
V OBLIKI SATOVJA
Omar Mukbaniani
1,2
*, Witold Brostow
3
, Jimsher Aneli
1,2
, Eliza Markarashvili
1,2
,
Tamara Tatrishvili
1,2
1
Faculty of Exact and Natural Sciences, Department of Macromolecular Chemistry, Ivane Javakhishvili Tbilisi State University, Ilia
Chavchavadze Ave. 3, Tbilisi 0179, Georgia
2
Institute of Macromolecular Chemistry and Polymeric Materials, Ivane Javakhishvili Tbilisi State University, Ilia Chavchavadze Ave. 3,
Tbilisi 0179, Georgia
3
Laboratory of Advanced Polymers & Optimized Materials (LAPOM), Department of Materials Science and Engineering and Department of
Physics, University of North Texas, 3940 North Elm Street, Denton, TX 76207, USA
Prejem rokopisa – received: 2019-04-29; sprejem za objavo – accepted for publication: 2019-09-30
doi:10.17222/mit.2019.091
Using a hydrosilylation reaction of 2.4.6.8-tetrahydro–2.4.6.8–tetramethylcyclotetrasiloxane (D 4
H
) with 2.2.3.3–tetraflu-
oropropyl acrylate and vinyltriethoxysilane at a 1:3:1 ratio of the initial compounds in the presence of platinum catalysts, a new
D 4
RR’
type fluorine-containing methylorganocyclosiloxane was obtained. Via a ring-opening co-polymerization reaction of D 4
R,R’
type methylorganocyclotetrasiloxane in a solution, in the presence of catalysts, anhydrous powder-like potassium hydroxide, or
tetramethylammonium fluoride, new comb-type siloxane matrices with pendant ethyl tetrafluopropionate side groups and
cross-linkable triethoxysilane moieties were obtained. The synthesized comb-type polymers were analysed with FTIR,
1
H,
13
C,
and
29
Si NMR spectroscopy as well as the DSC and GPC methods. Sol-gel reactions of polymers doped with lithium trifluoro-
methanesulfonate (triflate) and lithium bis(trifluoromethanesulfonyl)imide were studied and solid polymer electrolyte mem-
branes were obtained. The ion conductivity of the membranes was determined via electrical impedance spectroscopy.
Keywords: hydrosilylation, polymerization, SEM, sol-gel, thermogravimetric analysis
Avtorji so izdelali novi D 4
RR’
tip fluor vsebujo~ega metilorganociklosiloksana s hidrosililacijsko reakcijo 2.4.6.8-tetra-
hidro–2.4.6.8–tetrametilciklotetrasiloksana (D 4
H
) z 2.2.3.3–tetrafluoropropil akrilatom in viniltrietoksilanom pri razmerju 1:3:1
za~etnih spojin v prisotnosti Pt katalizatorja. Preko odprto-obro~ne kopolimerizacijske reakcije D 4
R,R’
so izdelali novo
siloksansko matrico, v obliki satovja, s pripeto stransko tetrafluopropionatno skupino in pre~no zamre`eno trietoksisilansko
skupino v raztopini metilorganociklotetrasiloksana, v prisotnosti katalizatorjev, anhidridnega prahu KOH ali tetrametil-
amonijevega fluorida. Sintetizirani polimer v obliki satovja so analizirali s FTIR,
1
H,
13
C, in
29
Si NMR spektroskopijami ter
DSC- in GPC-metodama. [tudirali so sol-gel reakcije polimerov, dopiranih z litijevim trifluorometanesulfonatom (triflat) in
litijevim bi(trifluorometanosulfonil) imidom in so dobili trdne polimerne elektrolitne membrane. Ionsko prevodnost membran so
dolo~ili s pomo~jo elektro-impedan~ne spektroskopije.
Klju~ne besede: hidrosilanizacija, polimerizacija, SEM, sol-gel, termogravimetri~na analiza
1 INTRODUCTION
The development of new and more efficient methods
of energy storage and conversion is increasing in import-
ance. This includes the efficient storage of electricity,
leading to the development of batteries and other
energy-storage devices with a high energy density, low
energy losses during an operation, a low cost and long
lifetime.
1–4
The promotion of the anion–cation disso-
ciation is desirable because it leads to an enhancement of
ionic conductivity via an increase in the free-ion concen-
tration. Following the realisation that the ionic
conductivity of polymer electrolytes is enhanced in the
elastomeric amorphous phase by the segmental motion
of the polymer chains, significant research was under-
taken to develop an amorphous polymer structure with a
highly flexible backbone.
Among the polyphosphazenes, polyacrylate and
inorganic polymers, polysiloxanes are particularly pro-
mising because they can have a wide variety of substi-
tuents bound to silicones in the backbone of the alternat-
ing silicon and oxygen atoms. Polysiloxanes are superior
to polyphosphazenes because of their backbone flexibil-
ity, high chemical- and thermal-oxidation stability, easy
processing as well as a low cost and low toxicity.
2,5–7
It is well known that polysiloxanes are characterized
with very low glass temperatures such as T
g
= –123 °C
for polydimethylsiloxane, a very high free volume and
high segmental mobility and presently the best matrix for
an Li–ion transportation. The high solubility of the
corresponding salt in the polymer is another factor for
the achievement of high ion conductivity. This condition
is created with an introduction to the polymer–elec-
trolyte main chain or side group of such a "host" donor
group, like the ester oxygen imide group, halogen, and
especially, fluorine groups. The formation of grid-like
Materiali in tehnologije / Materials and technology 54 (2020) 1, 33–39 33
UDK 620.1:669.058.4:669.14:669.786 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 54(1)33(2020)
*Corresponding author's e-mail:
omar.mukbaniani@tsu.ge (Omar Mukbaniani)

structures increases the mechanical properties of poly-
mer electrolytes.
5,8–10
Among organosilicon compounds, the comb-type
polymers with donor fragments at silicon atoms are of
interest. Such polymers are mainly obtained via hydro-
lytic polycondensation reaction donor groups containing
diorganodichlorosilanes, or with modification reactions
of industrially available polymethylhydrosiloxane
(PMHS), via a hydrosilylation reaction of polymethyl-
hydrosiloxane with allyl–, vinyl– or unsaturated bonds
containing compounds in the presence of platinum
catalysts (Pt/C, platinum hydrochloric acid, Karstedt’s
catalyst),
10
or else using dehydrocoupling reactions of
polymethylhydrosiloxane with hydroxyl– and donor
groups containing compounds in the presence of
catalysts.
One of the ways of the synthesis of comb-type
polyorganosiloxanes is the hydrosilylation reaction of
2.4.6.8–tetramethyl–2.4.6.8-tetrahydrocyclotetrasiloxane
(methylcyclotri–, –pentasiloxanes) with allyl or vinyl
containing compounds in the presence of platinum
catalysts, followed by polymerization or copolymeri-
zation reactions of the obtained organocyclosiloxanes in
the presence of terminating (regulating) agent hexamet-
hyldisiloxane or without it – in the presence of nucleo-
philic catalysts. Thus, polyorganosiloxanes with a
regular arrangement of the side donor groups can be
obtained.
11,12
As expected, the properties of the comb-type organo-
silicon polymers depend on the structure of macromo-
lecular chains and on the nature of the organic groups
surrounding the silicon atom.
8
In the comb-type copoly-
mers, there are organic substituent groups of different
sizes and types bonded to the methylsiloxane hydro-
phobic matrix. A wide range of variations of these sub-
stituent groups is possible. Some organosilicon copoly-
mers contain donor groups and exhibit complexation
properties.
9,10
A variety of organic donor groups can be bound to
silicon, including fluorine host groups in the side chain
of a siloxane matrix, which provides a possibility to vary
the ion-conducting properties of polymer electrolyte
membranes.
The aims of our work were the synthesis of D
4
R,R’
type methylcyclotetrasiloxane with 2,2,3,3–tetrafluorop-
ropyl propionate side groups and ethylsilyltriethoxy
groups (as cross-linking moieties) on silicon; the deter-
mination of their structure with the FTIR and NMR
spectroscopy; an investigation of co-polymerization
reactions of D
4
R,R’
with terminating agent hexamethyl-
disiloxane and the obtaining of comb-type polymers;
sol–gel reactions of comb-type polymers for obtaining
new solid polymer electrolyte membranes on the basis of
lithium salts: lithium trifluoromethanesulfonate and
lithium bis(trifluoromethanesulfonyl)imide; and a study
of their electrical and other physical properties.
2 EXPERIMENTAL PART
2.1 Materials
2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasilo-
xane (D
4
H
), platinum hydrochloric acid, Karstedt’s
catalyst (Pt
2
[(VinSiMe
2
)
2
O]
3
) or platinum (0)–1,3–
divinyl–1,1,3,3-tetramethyldi–siloxane complex (2-%
solution in xylene) and platinum hydrochloric acid
(Aldrich), Pt/C (10 %), were used as received. Lithium
trifluoromethanesulfonate (triflate) and lithium bis-
(trifluoromethanelsulfonyl)imide were also purchased
from Aldrich. Toluene was dried over and distilled from
sodium under an atmosphere of dry nitrogen.
Tetrahydrofuran (THF) was dried over and distilled
from a K–Na alloy under an atmosphere of dry nitrogen.
0.1-M solution of the platinum hydrochloric acid in THF
was prepared and kept under nitrogen at a low tempera-
ture.
2.2 Characterization
FTIR spectra were recorded on a Nicolet Nexus 470
machine with an MCTB detector.
1
H,
13
C NMR and
29
Si
NMR spectra were recorded on a Varian Mercury
300VX NMR spectrometer, using DMSO (dimethyl sulf-
oxide, (CH
3
)
2
SO) and CCl
4
as the solvent and an internal
standard, respectively. A differential-scanning-calori-
metric (DSC) investigation was performed on a Net–zsch
DSC 200 F3 Maia apparatus. Glass-transition tempera-
tures (Tg) were read from endothermic DSC traces,
which were approximated to be midpoints between the
extrapolated tangents to the baselines above and below
the glass-transition region. The heating and cooling
scanning rates were 10 K/min. Scanning electron micros-
copy and X-ray energy dispersion microscopy were
performed on Hitachi TM3030 Plus devices.
Gel-permeation chromatography (GPC) was carried
out with a Waters Model 6000A chromatograph with an
R 401 differential refraction meter detector. The column
set comprised 10
3
and 10
4
Å ultrastyragel columns. The
sample concentration was approximately3%b yweight
in toluene; the typical injection volume for the siloxane
was 5 μL and the flow rate was about 1.0 mL/min.
Standardization of the GPC was accomplished with the
use of styrene or polydimethylsiloxane standards with
the known molecular weight. Determination of  Si-H
content was calculated according to the method des-
cribed in the reference
13
.
2.3 Hydrosilylation reaction of D4
H
with 2.2.3.3-tetra-
fluoropropyl acrylate and vinyltriethoxysilane
D
4
H
(1.200 g, 0.00499 mole) was transferred into a
100-ml flask under nitrogen using the standard Schlenk
technique. High vacuum was applied to the flask for half
an hour before the addition of 2.2.3.3-tetrafluoropropyl
acrylate (2.784 g, 0.01497 mole). The mixture was then
dissolved in 7 mL of toluene; a 0.1-M solution of
O. MUKBANIANI et al.: COMB-TYPE FLUORINE-CONTAINING POLYMER ELECTROLYTE MEMBRANES
34 Materiali in tehnologije / Materials and technology 54 (2020) 1, 33–39

platinum hydrochloric acid in tetrahydrofuran (from 5 to
9·1 0
–5
g per 1.0 g of the starting substance) was introdu-
ced. The homogeneous mixture was degassed and placed
into an oil bath, which was previously set to 50 °C and
the reaction continued at 50 °C. After 1 h, 0.949 g
(0.00499 mole) of vinyltriethoxysilane in 1 mL of
toluene was added. The reaction was controlled with a
decrease in the intensity of active  Si-H groups. Then
0.1 % of activated carbon was added and refluxed for
12 h for a deactivation of the catalysts.
All volatile products were removed with rotary
evaporation and the compound was precipitated at least
three times into pentane to remove side products. Finally,
all volatiles were removed under vacuum and further
evacuated under a high vacuum for 24 h to isolate 4.58 g
(93.0 %) of colourless viscous compound I –
2.4.6.8-tetramethyl–2.4.6–tri(2.2.3.3–tetrafluoropropyl
propionate)–8–ethyltriethoxysilane cyclotetrasiloxane
(D
4
R,R’
). For D
4
R,R’
founded n
D
20
= 1.3977; d
4
20
= 1.3772;
M
RD
= 183.3; M = 955 (the ebullioscopy method). Cal-
culated: M
RD
= 183.3; M = 988.
FTIR spectra (KBr, v-values in cm
–1
) provided the
following results: no  Si-H absorption at 2169; 1080
( SiOSi ), 958, 1128 (C-F), 1171 (CO-O), 1270
(Si-C), 1762 (C=O) and 2800-3100 (C-H).
1
H NMR
(d-DMSO, CCl
4
), (mg/L)  values: 0.14 (Si-Me), 0.56,
1.2 (m, Si–CH
2
– anti-Markovnikov addition), 0.9, 1.6
(m, =CH–CH
3
Markovnikov addition); 0.9, 1.60 (m,
=CH–CH
3
), 1.64, 2,6 (m, =CH–CH
3
), 2.4 (m, CH
2
–O)
overlaps with the signals of methine groups, 3.8 (m,
Si–O–CH
2
), 4.5 (t, CH
2
–CF
2
), 5.95–5.61 (t, CF
2
H).
13
C
NMR (d–DMSO, CCl
4
), (mg/L): –1.92 (Si–CH
3
), 1.49,
7.9, 8.8, 18.2, 26.6, 27.1, 58.4 107, 107.8 and 173
correspond to the carbon atoms in groups OCH
2
–CH
3
,
=CH–CH
3
, =CH–CH
3
,  SiCH
2
CH
2
–, –CH
2
CO–,
OCH
2
CH
3
, –CO–CH
2
–CF
2
–, –CF
2
–, –CHF
2
and C=O.
29
Si NMR (mg/L): –18.6 –20.4. –46.0 –57.0,
–665.0.
12,14,15
The hydrosilylation reactions in the presence of other
catalysts were carried out in accordance with the same
method.
2.4 Ring-opening co-polymerization reaction of D
4
R,R’
with regulated agent hexamethyldisiloxane
1.137 g (1.150 mmole) of the D
4
R,R’
compound and
0.0386 g (0.223 mmole) of hexamethyldisiloxane were
transferred into a 50-ml flask under nitrogen. A high
vacuum was applied to the flask for half an hour. Then
the compound was dissolved in 1.8-ml dry toluene and
0.01 % of the total mass powder form potassium hyd-
roxide was added. The mixture was degassed, placed in
an oil bath that was previously set to 60 °C and poly-
merized under nitrogen for 25 h. Then 7 mL of toluene
were added to the reaction mixture and the product was
washed with water. The crude product was stirred with
MgSO
4
for 6 h, filtered and evaporated; the polymer was
precipitated at least three times into pentane to remove
side products. Finally, all volatiles were removed under a
vacuum up to a constant mass, after that 1.0 g (85 %) of
colourless viscous polymer (II) was isolated. For
oligomer II founded  sp
= 0.19; T
g
= –73 – –76 °C; M
n
=
3.775·10
3
;M
 = 4.137·10
3
(D=1.1).
FTIR (KBr, cm
–1
),  as
: 786 ( Si-CH
3
), 1080
( SiOSi ), 958, 1128 (C-F), 1171 (CO-O), 1270
(Si-C), 1762 (C=O) and 2800-3100 (C-H).
1
H NMR
(d-DMSO, CCl4), (mg/L)  : 0.14 (Si-Me), 0.56, 1.2 (m,
 Si–CH
2
- anti-Markovnikov addition), 0.9, 1.6 (m,
=CH-CH
3
Markovnikov addition); 0.9, 1.60 (m,
=CH–CH
3
), 1.64, 2,6 (m, =CH–CH
3
), 2.4 (m, CH
2
–O)
overlaps with the signals of methine groups, 3.8 (m,
Si–O–CH
2
), 4.5 (t, CH
2
–CF
2
), 5.95–5.61 (t, CF
2
H).
13
C
NMR (d-DMSO, CCl4), (mg/L)  : –1.92 (Si-CH
3
), 1.49,
7.9, 8.8, 18.2, 26.6, 27.1, 58.4 107, 107.8 and 173
correspond to the carbon atoms in groups –OCH
2
–CH
3
,
=CH–CH
3
,= C H–CH
3
,  SiCH
2
CH
2
–, –CH
2
CO–,
OCH
2
CH
3
, –CO–CH
2
–CF
2
–, –CF
2
–, –CHF
2
and C=O.
29
Si NMR (mg/L): –18.6-20.4. –46.0 – –57.0,
–665.0.
12,14,15
The ring-opening polymerization reaction of com-
pound I at various temperatures was carried out in the
same manner.
2.5 General procedure for the preparation of cross-
linked polymer electrolytes
During a typical preparation, 0.75 g of polymer II
was dissolved in 4 mL of dry THF and thoroughly mixed
for half an hour before an addition of a catalytic amount
of acid (one drop of 0.1 N HCl solution in ethyl alcohol)
to initiate the cross-linking process. After stirring for
another 3 h, the required amount of lithium triflate from
the previously prepared stock solution in THF was added
to the mixture and the stirring continued for 1 h more.
The mixture was then poured onto a Teflon mould with a
diameter of 4 cm and the solvent was allowed to
evaporate slowly overnight. Finally, the membrane was
dried in an oven at 70 °C for 3 d and at 100 °C for 1 h.
Homogeneous and transparent films with the average
thickness of 200 μm were thus obtained. These films are
insoluble in typical solvents and only swell in THF. The
preparation of solid polymer electrolyte membranes with
lithium bis(trifluoromethanesulfonyl)imide was carried
out in the same manner.
2.6 AC impedance measurements
The total ionic conductivity of the samples was deter-
mined by placing an electrolyte disk between two
10-mm-diameter brass electrodes. The electrode/elec-
trolyte assembly was secured in a suitable constant-
volume support, which allowed highly reproducible
measurements of conductivity to be performed between
repeated heating/cooling cycles. The cell support was
located in an oven and the sample temperature was
measured by a thermocouple positioned close to the ele-
O. MUKBANIANI et al.: COMB-TYPE FLUORINE-CONTAINING POLYMER ELECTROLYTE MEMBRANES
Materiali in tehnologije / Materials and technology 54 (2020) 1, 33–39 35

ctrolyte disk. The bulk conductivities of the electrolytes
were determined during a heating cycle using the im-
pedance technique (a BM 507 – TESLA impedance
meter for frequencies of 50 Hz–500 kHz) over a tempe-
rature range of 20–100 °C.
3 RESULTS
3.1 Hydrosilylation reaction of D
4
H
with 2.2.3.3-tetra-
fluoropropyl acrylate and vinyltriethoxysilane
The synthesis of D
4
R,R’
type methylorganocyclo-
tetrasiloxane with 2.2.3.3-tetrafluoropropyl propionate
and ethyltriethoxysilylated groups on silicon was
performed via a hydrosilylation reaction of 2.4.6.8–tetra-
hydro–2.4.6.8-tetramethylcyclotetrasiloxane (D
4
H
) with
2.2.3.3–tetrafluoropropyl acrylate and vinyltriethoxy-
silane in the presence of platinum catalysts (platinum
hydrochloric acid, Karstedt’s catalysts) and Pt/C (10 %)
at 50 °C in the melt condition as well as in a toluene
solution. It was established that the hydrosilylation
reaction of D
4
H
with 2.2.3.3–tetrafluoropropyl acrylate
and vinyltriethoxysilane proceeds vigorously during the
first 3–7 min. The reaction was controlled by a decrease
in the intensity of active  Si–H groups in the 2160-2170
cm
–1
region. From
16
it is known that a hydrosilylation
reaction of 2.4.6.8–etrahydro–2.4.6.8–etramethylcyc-
lotetrasiloxane (D
4
H
) with allyl butyrate and
vinyltriethoxysilane in the melt condition proceeds vigo-
rously, changing the direction of the hydride addition
and partially substituted hydroxyl containing methyl-
cyclotetrasiloxane is obtained.
To mitigate side reactions and obtain fully substituted
cyclotetrasiloxanes (D
4
R,R’
), we investigated hydro-
silylation reactions of D
4
H
with 2.2.3.3–tetrafluoropropyl
acrylate and vinyltriethoxysilane at a 1:3:1 ratio of the
initial compounds and studied the reactions in a dry
diluted toluene solution at various temperatures: (30, 40
and 50) °C. During the hydride-addition reactions, the
changes in active  Si-H bonds’ concentrations with time
were observed, and the decrease in the active Si–H bond
concentration in the hydrosilylation reaction was
controlled by a well-known method.
13
We found that the activity of the catalysts during the
hydrosilylation reactions of D
4
H
with 2.2.3.3–tetraflu-
oropropyl acrylate and vinyltriethoxysilane decreases in
the following order: Karstedt’s catalyst  H
2
PtCl
6
>
Pt/C.
The reaction proceeds according to Scheme 1.
Therefore, the obtained organocyclotetrasiloxane I is
a transparent, viscous product, well soluble in ordinary
organic solvents. The structure and composition of this
compound was determined in terms of molecular mass,
molecular refraction, FTIR,
1
H,
13
Ca n d
29
Si NMR
spectra data.
In the FTIR spectra of compound I, the car-
bon–fluorine bond stretching appears in the infrared
spectrum between 1000 cm
–1
and 1360 cm
–1
.
11
From the
literature, it is known that monofluorinated compounds
have a strong band between 1000 cm
–1
and 1110 cm
–1
;
with more than one fluorine atoms, the band splits into
two bands, one for the symmetric mode and the other for
the asymmetric one.
17
Carbon-fluorine bonds are so
strong that they can replace the existing carbon-hydrogen
bonds.
18,19
In our case, in the spectra, one can observe
absorption bands at 1128 cm
–1
and 958 cm
–1
, charac-
teristic of the valence and fan-shaped oscillation of CF
2
groups, respectively. The absorption band in a range of
2160–2170 cm
–1
characteristic of the  Si-H bonds
disappears.
For compounds I, we also obtained
29
Si NMR
spectra. One can observe the chemical shifts at  = –18.6
– –20.4 mg/L and–26.9– –27.7 mg/L, characteristic of
the RR’SiO (D) unit in a cyclic fragment, signals at  =
–44.9 to –55.7 mg/L attributed to the isotactic and atactic
resonance reorganization of D
OR
fragments and a signal
at  = –65 mg/L, characteristic of the silica T-rings in the
triethoxysilylated groups – in agreement with the litera-
ture data.
14,15
3.2 Ring-opening co-polymerization reaction of D
4
R,R’
with hexamethyldisiloxane
We studied co-polymerization reactions of com-
pounds I (D
4
R,R’
) with hexamethyldisiloxane as the ter-
minating agent at a 5:1 ratio of the initial compounds, in
the presence of nucleophilic powdery anhydrous potas-
sium hydroxide at a temperature of 90–110 °C.
Co-polymerization reactions of compounds I were
carried out in a 70–80 % solution of dry toluene in the
presence of 0.01 % of mass fractions of potassium hyd-
roxide. Changes in the viscosity during the progressing
reaction were followed. The reaction proceeds according
to Scheme 2.
Therefore, the obtained polymers were precipitated
and washed with pentane and dried in a vacuum up to a
constant mass. These polymers are viscous, transparent
liquids, well soluble in organic solvents including
toluene and chloroform, with  sp
 0.19. The structures
and compositions of the polymers were determined by
means of FTIR,
1
H,
13
C and
29
Si NMR spectra.
In the FTIR spectra of polymers II, one can observe
that the carbon-fluoride bonds are so strong that they
O. MUKBANIANI et al.: COMB-TYPE FLUORINE-CONTAINING POLYMER ELECTROLYTE MEMBRANES
36 Materiali in tehnologije / Materials and technology 54 (2020) 1, 33–39
Scheme 1: Hydrosilylation reaction of D
4
H
with 2.2.3.3-tetra-
fluoropropyl acrylate and vinyltriethoxysilane

overlap all carbon-hydrogen bonds.
17
In our case, in the
spectrum, one can observe absorption bands in the 1128
and 958 cm
–1
regions, characteristics of the valence and
fan-shaped oscillations, respectively.
From gel-permeation chromatography investigations,
we obtained the values of the number and weight average
molecular mass, presented above in Section 2.4.
The DSC results show a single glass-transition tem-
perature cantered around –80.4 °C and no crystallization
was observed. Hence, the use of these polymers for solid
electrolyte membranes is possible.
3.3 Preparation of solid polymer electrolyte mem-
branes
Sol-gel reactions were performed for polymer II.
Along with the 2.2.3.3–tetrafluoropropyl propionate
groups, we had ethyl triethoxysilyl groups in the side
chains that made sol-gel reactions possible. To the
solution of polymer II in tetrahydrofuran, we added
certain amounts (5, 10, 15 and 20 % of mass fractions)
of lithium triflate or lithium bis(trifluoromethane-
sulfonyl)–imide. After one hour of stirring, 1–2 drops of
HCI solution in ethanol were added and the stirring con-
tinued for 1–2 h, maintaining an inert atmosphere
throughout the night. Afterwards, at various tempera-
tures in the interval of 30–70 °C under a vacuum, we
obtained solid polymer electrolyte membranes. Sol-gel
reactions of polymer II proceed according to Scheme 3.
We obtained polymer electrolyte membranes III
based on lithium triflate: III (1) with 5 %; III (2) with
10 %, III (3) with 15 % and III (4) with 20 %. On the
basis of lithium bis(trifluoromethanesulfonyl)imide, we
obtained: III (5) with 5 %, III (6) with 10 %, III (7) with
15 % and III (8) with 20 %.
The DSC diagram for a membrane shows the
glass-transition temperature T
g
, the region centred aro-
und –83 °C and the softening temperature T
soft
centred
around +42 °C.
Given the membrane applications, the thermogravi-
metric analysis (TGA) was carried out in air. The
samples exhibit a gradual weight loss of about 8–12 %,
which is due to the removal of the residual solvent and
moisture from the electrolyte sample in the temperature
range of 90–110 °C. Further 5-% mass losses can be
observed between 200 °C and 250 °C. Above 250 °C,
degradation processes occur, continuing up to 500 °C.
For membrane III (3) (15 % of CF
3
SO
3
Li salt), we
found a fairly smooth and uniform surface morphology
on SEM micrographs. This confirmed a completely
amorphous nature of the PE membrane and a full
dissolution of the lithium salt, which also coincided with
O. MUKBANIANI et al.: COMB-TYPE FLUORINE-CONTAINING POLYMER ELECTROLYTE MEMBRANES
Materiali in tehnologije / Materials and technology 54 (2020) 1, 33–39 37
Scheme 2: Polymerization reaction of compound I results at 110 °C as II
Scheme 3: Sol-gel reaction of polymer II
Table 1: Specific volumetric electric resistance ( v
) and conductivity ( v
) of polymer electrolytes based on membranes III at 25 °C and 90 °C
# Membrane III Salt, w/%
 v at 25 °C,
 ×c m
 v at 25 °C,
Siemens/cm
 v at 90 °C,
Siemens/cm
1 III (1) CF 3
SO
3
L i ,5% 5 . 3×1 0
9
1 . 9×1 0
–10
6 . 5×1 0
–8
2 III (2) CF
3SO
3Li, 10 % 3.3 × 10
7
3 . 0×1 0
–6
9 . 6×1 0
–6
3 III (3) CF
3SO
3Li, 15 % 1.8 × 10
6
5.5 ×10
–7
8 . 9×1 0
–5
4 III (4) CF
3
SO
3
Li, 20 % 7.5 × 10
5
1 . 3×1 0
–7
9 . 2×1 0
–5
5 III (5) (CF
3
SO
2
)
2
N L i ,5% 4 . 8×1 0
9
2 . 1×1 0
–10
3 . 8×1 0
–8
6 III (6) (CF 3SO
2)
2NLi, 10 % 3.4 × 10
5
2 . 9×1 0
–6
7 . 7×1 0
–5
7 III (7) (CF
3
SO
2
)
2
NLi, 15 % 7.0 × 10
6
1 . 4×1 0
–7
1 . 1×1 0
–6
8 III (8) (CF
3
SO
2
)
2
NLi, 20 % 8.2 × 10
5
1 . 2×1 0
–7
8 . 5×1 0
–7
9 III (9) (CF
3
SO
3
Li) (20) +Al
2
O
3
(2.5 %) 1.7 × 10
5
6 . 2×1 0
–6
7 . 5×1 0
–5
10 III (10) (CF 3SO
3Li) (20) +Al
2O 3 (5 %) 2.0 × 10
4
1 . 1×1 0
–5
1 . 8×1 0
–4
11 III (11) (CF 3SO
3Li) (20) +Al 2O 3 (7.5 %) 1.3 × 10
5
7 . 8×1 0
–6
4 . 5×1 0
–5
12 III (12) (CF
3
SO
3
)NLi, (20%) + Al
2
O
3
(10 %) 2.3 × 10
5
4 . 0×1 0
–6
1 . 1×1 0
–4
13 III (13) (CF
3
SO
2
)
2
NLi, (10 %) + Al
2
O
3
(2.5 %) 3.3 × 10
4
3 , 2×1 0
–5
2 . 6×1 0
–4
14 III (14) (CF
3
SO
2
)
2
NLi, (10 %) + Al
2
O
3
(5 %) 5.1 × 10
3
2 . 0×1 0
–4
3 . 1×1 0
–3
15 III (15) (CF
3
SO
2
)
2
NLi, (10 %) + Al
2
O
3(
7.5 %) 3.3 × 10
4
3 , 2×1 0
–5
6 . 6×1 0
–4
16 III (16) (CF
3
SO
2
)
2
NLi, (10 %) + Al
2
O
3
(10 %) 2.8 × 10
5
3 . 6×1 0
–6
2 . 7×1 0
–5

the XRD results. These images showed a good dis-
persion of the filler and small pores entrapping the ionic
liquid. Well visible amorphous layers of lithium salts
were reflected in a high ionic conductivity.
Table 1 below including membranes with different
amounts of salt provides the values for the specific
volumetric electric resistance and conductivity of the
electrolytes at 25 °C and 90 °C.
As expected and seen in Table 1, the conductivity of
the membranes essentially depends on the polymer
matrix, the salt type and its concentration. Thus, first, the
extreme dependence of the electrical conductivity of the
membranes on the salt concentration attracts attention –
the maximum conductivity is observed near the concen-
tration of 10 %. This dependence is explained with an
increase in the probability of the formation of ion pairs at
elevated salt concentrations. In an electrical flow, these
pairs move as one, but since the effective mass and
mobility of these pairs are greater than for individual
electrons, the total electric current in the membranes
with electron pairs is weaker than that in the membranes
whose current is carried by individual electrons.
20–22
We
investigated the temperature dependences of the
properties of the solid polymer electrolytes in a range of
25–90 °C. The results pertaining to the membranes listed
are presented in Arrhenius coordinates in Figure 1.
We compared the conductivities with and without
corundum. In Table 1 and Figure 2, we show that, in
general, electric conductivity of membranes increases
with an increasing oxide concentration in the interval of
0–10 wt.%. However, with a further increase in the oxide
concentration the membrane conductivity decreases. A
possible explanation for this is as follows: at lower
concentrations, the corundum particles promote a
homogeneous distribution of the salt particles in the
matrix. However, at higher concentrations the same
particles decrease the salt ion mobility because of the
increased interactions between the salt ions and oxide
particles and, correspondingly, the conductivity of the
membranes decreases.
Figure 3 presents voltammograms, that is, the curves
of dependence of electric current on the voltage applied.
The main feature of these curves is the increasing of the
current with the following deceleration in the current
growth. The dependence of the length of the linear part
O. MUKBANIANI et al.: COMB-TYPE FLUORINE-CONTAINING POLYMER ELECTROLYTE MEMBRANES
38 Materiali in tehnologije / Materials and technology 54 (2020) 1, 33–39
Figure 1: Temperature dependence of the conductivity in Arrhenius coordinates of the solid polymer electrolytes based on: a) III-type
membranes with salt CF
3
SO
3
Li at concentrations (w/%)of 5 % (1), 10 % (2), 15 % (4) and 20 % (3); b) III-type membranes with salt
(CF
3
SO
2
)
2
NLi at concentrations ((w/%)) of 5(1), 10 % (3), 15 % (2) and 20 % (4); c) III-type membrane with a blend of salt CF
3
SO
3
Li (10w/%)
and Al
2
O
3
(10(w/%))
Figure 3: Voltammograms for membranes of type III containing 5 (1),
15 (2), 20 (3) and 10w/% (4) of salt I
Figure 2: Dependence of the conductivity of membranes of type III
on the concentration of Al
2
O
3
containing 20 w/% of the CF
3
SO
3
salt
(1) and 10w/% of the (CF
3
SO
2
)
2
NLi salt (2) at room temperature

of the curve depends essentially on the interactions dis-
cussed above.
4 CONCLUSIONS
With a hydrosilylation reaction of tetrahydrotetra-
methylcyclotetrasiloxane with 2.2.3.3-tetrafluoropropyl
acrylate and vinyltriethoxysilane at a 1:3:1 ratio of the
initial compounds, in the presence of platinum catalysts,
the corresponding adduct D
4
R,R’
was obtained.
Via a copolymerization reaction of D
4
R,R’
with ter-
minating agent hexamethyldisiloxane at a 5:1 ratio of the
initial compounds, in the presence of a catalyst,
comb-type polymers were obtained. With a sol-gel reac-
tion of the obtained polymer doped with lithium tri-
fluoromethanesulfonate (triflate) and lithium bis(tri-
fluoromethanesulfonyl)imide, solid polymer electrolyte
membranes were obtained.
The conductivity of the membranes in the range of
25–90 °C can be described with an equation close to the
VTF type. The membranes containing 10 w/% of salt
CF
3
SO
3
L are characterized with a higher conductivity in
this range of temperatures, which is three orders higher
than that of the analogue membranes containing 5 w/%
of the same salt. The conductivity of electrolytes con-
taining 15 w/% and 20 w/% of this salt is lower than for
the analogue ones with 10 w/% of salt because of the
formation of ion pairs with a mobility lower than that of
mono-ions. The characteristic of the voltammograms of
these electrolytes corresponds to the value of con-
ductivity of the electrolytes – the higher the conductivity,
the higher is the specific electric current in these
materials.
Acknowledgment
The financial support of the Georgian National
Science Foundation, Science and Technology Centre in
Ukraine, Grant – STCU-2016-16 (6301), is gratefully
acknowledged.
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