Branching of the perfluorinated chain influences the liquid-crystalline properties of semifluorinated alkanes: Perfluorooctyl- and perfluoroisononyl-n- alkanes-a comparative study

Article abstract of DOI:10.1080/15421400600700430

Two series of semifluorinated-n-alkanes (SFAs) of comparable perfluorinated chain length but different terminal group constitution, namely perfluorooctyl-n-alkanes [F-(CF₂)₈-(CH₂) _n-H, in short F8Hn] and perfluoroisononyl-n-alkanes [(CF ₃)₂CF(CF₂)₆-(CH₂) _n-H, in short iF9Hn] were synthesized. Their thermal properties were analyzed by means of differential scanning calorimetry (DSC), on both heating and cooling of the samples. The textures of the synthesized semifluorinated alkanes were investigated with the microscopy in polarized light. Similar to previously investigated perfluorodecyl-n-alkanes, perfluorooctyl-n-alkanes containing fewer than 12 methylene groups form smectic B phase. F8H8, F8H9, and F8H10 show a tendency to supercool and preserve smectic B ordering even below the transition temperature. For F8H11, the phase transition from smectic B to 3D crystal structure, manifesting itself as a rapid recrystallization, has been observed. Perfluorooctyl-n-alkanes of 12 or more methylene groups do not form liquid-crystalline phases. In contrast to perfluorooctyl-n-alkanes, perfluoroisononyl-n-alkanes are not capable of liquid-crystalline phase formation, regardless of the hydrogenated moiety length and the experimental conditions.

Full text of DOI:10.1080/15421400600700430

This article was downloaded by: [University of Saskatchewan Library]
On: 28 September 2012, At: 01:47
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Molecular Crystals and Liquid
Crystals
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/gmcl20
Branching of the Perfluorinated
Chain Influences the Liquid-
Crystalline Properties of
Semifluorinated Alkanes:
Perfluorooctyl- and
Perfluoroisononyl-n-Alkanes—a
Comparative Study
M. Broniatowski a , P. Dynarowicz-Łątka a & W. Witko
b
a Jagiellonian University, Faculty of Chemistry,
Kraków, Poland
b Henryk Niewodniczański Institute of Nuclear
Physics, Polish Academy of Sciences, Kraków, Poland
Version of record first published: 20 Dec 2006.
To cite this article: M. Broniatowski, P. Dynarowicz-Łątka & W. Witko (2006):
Branching of the Perfluorinated Chain Influences the Liquid-Crystalline Properties
of Semifluorinated Alkanes: Perfluorooctyl- and Perfluoroisononyl-n-Alkanes—a
Comparative Study, Molecular Crystals and Liquid Crystals, 460:1, 63-74
To link to this article: http://dx.doi.org/10.1080/15421400600700430
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-
and-conditions

This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden.
The publisher does not give any warranty express or implied or make any
representation that the contents will be complete or accurate or up to
date. The accuracy of any instructions, formulae, and drug doses should be
independently verified with primary sources. The publisher shall not be liable
for any loss, actions, claims, proceedings, demand, or costs or damages
whatsoever or howsoever caused arising directly or indirectly in connection
with or arising out of the use of this material.

Mol. Cryst. Liq. Cryst., Vol. 460, pp. 63–74, 2006
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400600700430
Branching of the Perfluorinated Chain Influences the
Liquid-Crystalline Properties of Semifluorinated Alkanes:
Perfluorooctyl- and Perfluoroisononyl-n-Alkanes—
a Comparative Study
M. Broniatowski
P. Dynarowicz-Ła˛tka
ꢀ
Jagiellonian University, Faculty of Chemistry, Krakow, Poland
W. Witko
´
Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy
ꢀ
of Sciences, Krakow, Poland
Two series of semifluorinated-n-alkanes (SFAs) of comparable perfluorinated
chain length but different terminal group constitution, namely perfluorooctyl-n-
alkanes [Fꢀ(CF2)8ꢀ(CH2)nꢀH, in short F8Hn] and perfluoroisononyl-n-alkanes
[(CF3)2CF(CF2)6ꢀ(CH2)nꢀH, in short iF9Hn] were synthesized. Their thermal
properties were analyzed by means of differential scanning calorimetry (DSC),
on both heating and cooling of the samples. The textures of the synthesized semi-
fluorinated alkanes were investigated with the microscopy in polarized light. Simi-
lar to previously investigated perfluorodecyl-n-alkanes, perfluorooctyl-n-alkanes
containing fewer than 12 methylene groups form smectic B phase. F8H8, F8H9,
and F8H10 show a tendency to supercool and preserve smectic B ordering even
below the transition temperature. For F8H11, the phase transition from smectic B
to 3D crystal structure, manifesting itself as a rapid recrystallization, has been
observed. Perfluorooctyl-n-alkanes of 12 or more methylene groups do not form
liquid-crystalline phases. In contrast to perfluorooctyl-n-alkanes, perfluoroisononyl-
n-alkanes are not capable of liquid-crystalline phase formation, regardless of the
hydrogenated moiety length and the experimental conditions.
Keywords: differential scanning calorimetry; liquid-crystalline properties; semifluori-
nated alkanes
Address correspondence to Patrycja Dynarowicz-Ła˛tka, Jagiellonian University,
ꢀ
FacultyofChemistry,Ingardena3,30-060Krakow,Poland.E-mail:ucdynaro@cyf-kr.edu.pl
63

64
M. Broniatowski et al.
1. INTRODUCTION
Normal alkanes and their perfluorinated analogs have different
chemical and physical properties, which are reflected in their limited
mixing, originally described by Scott [1]. Different properties of these
molecules are due to significant differences between fluorine and
hydrogen atoms in the electronegativity, polarity, and atomic radii.
Namely, the atomic radius of fluorine is twice as large as that of hydro-
gen (72 pm and 37pm, respectively) [2], whereas it is comparable with
carbon (72 pm and 77 pm). This causes a different conformation of the
hydrocarbon and the perfluorohydrocarbon chain. The former has a
planar all-trans conformation, whereas the latter is helical, resulting
from the steric hindrance [3]. Semifluorinated alkanes (SFAs) are very
interesting diblock compounds, possessing both chains (i.e., a poly-
methylene chain and a perfluorinated hydrocarbon fragments) cova-
lently bound within one molecule. They can be described by the
general formula Fꢀ(CF2)mꢀ(CH2)nꢀH, abbreviated as FmHn. They
were first synthesized in the early sixties of the preceding century
by Brace [4], and their properties, both in the solid state and in
solution, were described for the first time by Rabolt et al. in 1984
[5]. The two different moieties of a SFA molecule have opposing
character, namely the perfluorinated chain of a helical conformation
is fluorophilic and oleophobic whereas the hydrogenated fragment of
a flat all-trans conformation is fluorophobic and oleophilic. Because
of such a diblock structure, SFAs behave like amphiphiles at the
oleic=fluorous interface and are called primitive surfactants after
Turberg and Brady [6]. Their surface activity, both in different organic
solvents and in perfluorinated liquids, was investigated by Binks
¨
et al. [7,8] and Hopken et al. [9]. In 1991, Gaines [10] proved that some
SFAs are capable of Langmuir monolayer formation and can be suc-
cessfully deposited onto solid substrates with the Langmuir–Blodgett
technique.
In 1985, Mahler et al. [11] reported that a representative of SFAs,
namely perfluorodecyl-n-decane, abbreviated as F10H10, forms smectic
liquid-crystalline phases, although its structure is not typically meso-
genic because most of the mesogenic molecules have a rigid frame of
biphenyl, azobenzene, cyclopentanoperhydrophenantrene, or other cyc-
lic molecule, functionalized in axial positions with suitable substituents
[12]. In the case of semifluorinated alkanes, liquid-crystalline-phase
formation originates, similar to their surface activity, from their diblock
structure and the rigidity of the perfluorinated moiety [13]. Liquid-
crystalline phases of perfluorodecyl-n-alkanes were further investi-
¨
gated by Hopken et al. [9] and Viney et al. [14–16]. Upon texture

LC Properties of Semifluorinated Alkanes
65
analysis and X-ray measurements, the liquid-crystalline phases formed
by perfluorodecyl-n-alkanes were classified as smectic B; however, in
some cases higher ordering, such as smectic G or J, were also determ-
ined. In our previous paper [17], the influence of the length of the
hydrogenated fragment on the liquid-crystalline properties of perfluoro-
decyl-n-alkanes was described. The present contribution deals with the
liquid-crystalline properties of perfluorooctyl- and perfluoroisononyl-
n-alkanes. The purpose of these investigations was to verify how the
shortening of the perfluorinated chain by two CF2 groups (as compared
to perfluorodecyl-n-alkanes) affects the liquid-crystalline phase forma-
tion. The other objective was to verify whether the iso-branching in
perfluorononyl-n-alkanes influences the ability to form the liquid-
crystalline phase. To fulfill these aims, semifluorinated alkanes of these
two homologous series were synthesized, and their liquid-crystalline and
thermal properties were analyzed by means of polarizing microscopy
and differential scanning calorimetry (DSC).
2. EXPERIMENTAL
2.1. Synthesis
The following compounds of the general formula Fꢀ(CF2)8ꢀ(CH2)nꢀH
(perfluorooctyl series) and (CF3)2CF(CF2)6ꢀ(CH2)nꢀH (perfluoroisono-
nyl series), where n¼7–16 and 8–16, respectively, were synthesized
following the procedure described by Rabolt et al. [5]. Perfluorooctyl
iodide (98%) was purchased from Aldrich and perfluoroisononyl iodide
(98%) from Fluorochem. The respective n-alkenes (98–99%) were sup-
plied by Aldrich. All the substrates were used as received, without
further purification. Purity of the obtained semifluorinated alkanes
1
(99%þ) was checked by H NMR, 13C NMR, mass spectroscopy, and
elemental analysis.
2.2. Thermal Analysis
2.2.1. Differential Scaning Calorimetry (DSC)
The DSC analysis was performed on a DSC 821e Mettler Toledo
calorimeter. Specimens with mass of ca. 20–40 mg were scanned at
3ꢁminꢀ1. All samples were investigated in three heating=cooling cycles
from ꢀ50 to 70ꢁC. No dependence between the thermal history of the
samples and the course of DSC curves was observed. An empty alumi-
num crucible was used as a reference. The temperatures of anomalies
are given with the precision of 0.5ꢁC and the enthalpy changes at the
transitions with the precision of about 10%.

66
M. Broniatowski et al.
2.2.2. Optical Microscopy
Microscopic observations were performed on specimens held
between thin circular glass cover slips, using a Biolar PI (PZO, Poland)
polarizing microscope equipped with a Linkam (U.K.) THM 600 hot
stage and TMS 90 temperature controller. The temperature range
studied was from ꢀ50 ꢁto 70ꢁC. Different heating and cooling rates
within the range 0.2–30 minꢀ1 were applied. During the phase transi-
tions, the temperature was stabilized. The magnification was 500
times, and the results were observed by Hitachi CCD color video cam-
era and digitalized.
3. RESULTS
To visualize the textures of the investigated semifluorinated alkanes,
microscopic observations of the samples in the polarized light were
applied. The resultant images for the selected representatives are pre-
sented in Fig. 1. For perfluorooctyl-n-alkanes with the methylene
groups number n ¼ 8–11, typical mosaic textures, characteristic for
liquid-crystalline smectic phase B or higher smectics (such as G or
J) are observed (Fig. 1a,b), whereas when n > 11, lamellar structures
of three-dimensional (3D) crystals were seen (Fig. 1c,d).
To get further insight into phase transitions observed in the
samples, differential scanning calorimetry (DSC) measurements were
conducted for all the perfluorooctyl-n-alkanes, and the resultant DSC
FIGURE 1Textures of perfluorooctyl-n-alkanes: a) F8H8 (T¼15.6ꢁC), b) F8H9
(T¼31.6ꢁC), c) F8H12 (T¼33.0ꢁC), d) F8H16 (T¼45.1ꢁC).

LC Properties of Semifluorinated Alkanes
67
curves, both upon heating of the samples (lower curves) and cooling
(upper curves), are presented in Fig. 2. For clarity of presentation,
the results were divided into three groups corresponding to SFAs: with
short hydrogenated fragment, n¼8 and 9 (Fig. 2a); with hydrogenated
moiety of intermediate length, n¼10–12 (Fig. 2b); and with long
hydrogenated chain, n¼13–16 (Fig. 2c). The DSC curves for F8H8
and F8H9 (Fig. 2a) exhibit only one peak (both at heating and cooling)
corresponding to the transition smectic ! isotropic (lower curve) or
FIGURE 2 DSC curves for the investigated perfluorooctyl-n-alkanes.

68
M. Broniatowski et al.
isotropic ! smectic phase (upper curve). Different behavior was
observed for F8H10 and F8H11 (Fig. 2b). For F8H10, a peak correspond-
ing to the transition smectic ! isotropic appears at ca. 33ꢁC, and an
additional peak of lower intensity, corresponding to a phase transition
smectic ! crystalline, is clearly visible at ca. 15ꢁC. The latter has not
been detected in the course of the cooling curve. In contrast, in the course
of heating DSC curve of F8H11, only one peak corresponding to the tran-
sition smectic ! isotropic is observed, whereas on cooling two peaks
are visible: one at higher temperature value corresponding to the tran-
sition isotropic ! smectic and the second at lower temperature corre-
sponding to smectic ! crystalline transition. The DSC curves for
F8H12 differ from those discussed previously because only one peak is
visible, both on heating and cooling. The results for perfluorooctyl
alkanes with n>12 (Fig. 1c) are similar to F8H12, because only one
peak, corresponding to melting (crystalline ! isotropic) (heating
curve) or freezing (isotropic ! crystalline) (cooling curve), is observed.
From the DSC curves, enthalpies of phase transitions were calcu-
lated, and together with transition temperature values thus are gath-
ered in Table 1. Generally, the phase-transition temperatures on
heating of the investigated perfluorooctyl alkanes are 4–6ꢁC higher than
those noticed upon cooling. These temperatures increase with the num-
ber of methylene groups, and no odd–even effect is observed. As far as
the DHm are concerned, a similar tendency can be observed; namely,
an increase of the DHm value with the number of CH2 groups takes
TABLE 1 Thermal Characteristics of the Investigated Perfluorooctyl Alkanes
Tma [on heating=
cooling] (ꢁC)
Tpbt[on heating=
cooling] (ꢁC)
DHmc
(kJ=mol)
DHdpt
(kJ=mol)
Compound
F8H8
F8H9
—=—
—=—
15.3=—
37.4=27.9
32.7=26.7
43.4=37.8
43.4=39.6
49.7=46.6
53.1=48.2
20.7=18.3
33.3=29.1
33.0=28.8
—=32.7
—=—
—=—
—=—
—=—
—=—
—
—
14.7
24.4
16.1
19.6
—
—
—
—
—
F8H10
F8H11
F8H12
F8H13
F8H14
F8H15
F8H16
3.0ꢂ
12.1
22.6
27.1
26.1
33.4
39.1
aTm, transition temp. (cryst. ! isotropic or smectic).
bTpt, transition temp. (smectic ! isotropic).
cDHm, transition enthalpy corresponding to Tm.
dDHpt, transition enthalpy corresponding to Tpt.
ꢂsubstance may contain certain amounts of ‘‘supercooled smectic phase’’ at tempera-
tures less than 15ꢁC.

LC Properties of Semifluorinated Alkanes
69
place. The DHpf values were calculated for the perfluorooctyl-n-alkanes
with shorter hydrogenated moiety. The value of DHm for F8H10 is small
(ca. 3kJ=mol) in comparison with its DHpt (ca. 16kJ=mol), whereas in
the case of F8H11, the situation is quite different and the DHpt and
DHm are comparable (19.6 and 12.1kJ=mol, respectively).
Because of the characteristic phase transition, which can be noticed
in DSC curves of F8H10 and F8H11, the detailed texture analysis was
performed for those compounds. The textures of F8H10 are shown in
Fig. 3. Upon cooling from the isotropic liquid, mosaic textures, charac-
teristic for the smectic B phase, are visible (Fig. 3a). On further cooling,
some cracks appeared, the number of which increased with lowering of
the temperature. The number of cracks was found to be dependent on
the rate of cooling (increasing upon the reduction of the cooling rate).
Taking into consideration the DSC curves and the microscopic images
in polarized light, the behavior of F8H10 can be interpreted as follows.
The compound is liquid crystalline within the temperature range from
ca. 15ꢁC (phase transition observed in DSC curve) to ca. 33ꢁC (clearing
point). In microscopic measurements, we did not observe any sharp
transition because the sample of F8H10 tends to supercool and form
a metastable phase. At temperatures less than 15ꢁC, the textures are
still mosaic, indicating a smectic B phase, but the cracks appearing
upon further cooling indicate recrystallization. This is clearly visible
in Fig. 3, where the texture 3a, recorded at ca. 30ꢁC, is mosaic; 3b is
intermediate and cracked, whereas 3c seems to be a 3D crystal.
FIGURE 3Textures of F8H10: a) T¼18.5ꢁC, b) T¼ ꢀ13.2ꢁC, c) T¼ ꢀ47.4ꢁC.

70
M. Broniatowski et al.
FIGURE 4Textures of F8H11: a) T¼32.9ꢁC, b) T¼28.8ꢁC, c) T¼28.7ꢁC,
d) T¼28.3ꢁC; heating rate: 0.2ꢁminꢀ1.
The behavior of F8H11 differs from both F8H10 and all the remain-
ing perfluorooctyl-n-alkanes investigated here. The microscopic
images of this compound are presented in Fig. 4. On cooling, the
mosaic texture, indicating a smectic B phase, was observed (Fig. 4a),
but upon further cooling at ca. 28ꢁC a quick recrystallization occurred,
which is registered in Fig. 4b,c. Figure 4d shows a texture character-
istic of a 3D crystal. The results are in accordance with the calori-
metric measurements, indicating a crystal ! smectic transition at
ca. 28ꢁC. Similar results were described for F10H11 and F10H12 [17].
As far as the perfluorooctyl alkanes with a longer hydrogenated
moiety (n>11) are concerned, liquid-crystalline textures were not
observed, which is in agreement with the results published previously
for perfluorodecyl-n-alkanes [17]. Regarding perfluorooctyl-n-alkanes
with short hydrogenated fragment (n < 10), the textures were mosaic,
characteristic of the smectic B phase, regardless of the rate of cooling=
heating, and could be observed within a broad temperature range. No
peaks indicating smectic ! crystalline phase transition are present in
the DSC curves registered for these compounds. This can suggest that
the compounds are smectic at room temperature, their transition into
3D phase is of low energy, and they exhibit a pronounced tendency to
supercool and form a metastable phase, which is supported by the fact
that, even at low temperature and low rate of cooling, no recrystalliza-
tion of the F8H8 and F8H9 samples was observed.

LC Properties of Semifluorinated Alkanes
71
FIGURE 5Textures of perfluoroisononyl-n-alkanes: a) iF9H7 (T¼ ꢀ17.3ꢁC),
b) iF9H10 (T¼13.3ꢁC), c) iF9H11 (T¼27.9ꢁC), d) iF9H15 (T¼39.1ꢁC).
Microscopic measurements in polarized light were carried out for all
the investigated perfluoroisononyl-n-alkanes, and the results for selected
representatives are presented in Fig. 5. Generally, the observed textures
are typical for 3D crystals, regardless of the length of the hydrogenated
fragment and the experimental conditions. It is interesting that a minute
branchingoftheperfluorononylchainchangesthepropertiesofperfluoro-
isononyl-n-alkanes so dramatically versus perfluorooctyl-n-alkanes as
far as their crystalline=liquid-crystalline properties are concerned.
Calorimetric measurements were conducted for all the investigated
perfluoroisononyl-n-alkanes, and the resultant DSC curves are sepa-
rated into three groups: iF9H7, iF9H8, and iF9H10 (Fig. 6a), iF9H9,
iF9H11, and iF9H12 (Fig. 6b); and perfluoroisononyl-n-alkanes with
n > 12 (Fig. 6c). The DSC curves of the investigated perfluoroisononyl-
n-alkanes are similar—only one peak, indicating melting of the sample
(crystal ! isotropic transition), is present, and no additional peaks,
characteristic for phase transitions, can be noticed. From the DSC
curves, melting enthalpies have been calculated and together with
the melting and freezing temperatures are compiled in Table 2. An
odd–even effect is noticeable, especially for shorter homologues; for
example, the melting temperature of iF9H9 is 23ꢁC, whereas iF9H10
melts at ca. 16ꢁC. Similar to perfluorooctyl-n-alkanes, for the series
of perfluoroisononyl-n-alkanes, freezing temperatures are 4 to 6ꢁC
lower than the corresponding melting points.

72
M. Broniatowski et al.
FIGURE 6 DSC curves for the investigated perfluoroisononyl-n-alkanes.
4. DISCUSSION
Perfluorooctyl-n-alkanes form similar liquid-crystalline phases to
those described previously for perfluorodecyl-n-alkanes [17]. Similar
phase transitions were observed for F8H11 and F10H11; however,
F8H12 does not exhibit liquid-crystalline properties, in contrast to
F10H12. Short perfluorooctyl-n-alkanes (n¼8, 9) are smectic at room
temperature, and no recrystallization is seen on cooling. For F8H10

LC Properties of Semifluorinated Alkanes
73
TABLE 2 Thermal Characteristics of the Investigated Perfluoroisononyl
Alkanes
Compound
Tma [on heating=cooling] (ꢁC)
DHmb (kJ=mol)
iF9H7
iF9H8
iF9H9
iF9H10
iF9H11
iF9H12
iF9H13
iF9H14
iF9H15
iF9H16
ꢀ11.2=ꢀ19.9
ꢀ0.7=ꢀ6.1
23.1=18.0
16.4=8.2
32.0=24.8
35.1=28.6
35.4=32.9
39.4=32.0
45.9=38.7
46.5=40.7
9.1
12.7
32.1
14.8
29.8
32.2
38.5
30.4
38.5
40.4
aTm, transition temperature (crystalline ! isotropic).
bDHm, transition enthalpy corresponding to Tm.
and F8H11, characteristic phase transitions were observed. Perfluoro-
octyl-n-alkanes of longer hydrogenated fragment (n>11) are not
capable of liquid-crystalline phase formation. In contrast to perfluoro-
octyl-n-alkanes, perfluoroisononyl-n-alkanes do not form liquid, crys-
talline phases, regardless the length of the polymethylene chain and
the experimental conditions applied. It is very interesting that a
minute branching of the perfluorinated moiety profoundly affects the
properties of SFA in the solid state. From literature it is known that
some derivatives of SFAs possessing a halogen atom attached to the
hydrogenated part either in the middle of SFA molecule [16] or at
the terminal position [18] exhibit liquid-crystalline phases. However,
no studies have been performed so far for SFAs containing a substitu-
ent or branching in the perfluorinated fragment. From our results, it
can be concluded that the presence of CF3 branching in the terminal
position of the perfluorinated moiety results in higher molecular
ordering. This, in fact, can be expected taking into consideration that
for classic mesogens branching in the polymethylene chain leads to the
loss of liquid-crystalline properties and, simultaneously, to higher
ordering of molecules [12]. It would be of utmost importance to further
the investigations and perform X-ray experiments to get deeper
insight into the difference in molecular packing of normal versus iso
chains.
ACKNOWLEDGMENT
The State Committee for Scientific Research (KBN, Poland) is grate-
fully acknowledged for financial support (Grant No. 3 T09A 10527).

74
M. Broniatowski et al.
REFERENCES
[1] Scott, R. L. (1948). J. Am. Chem. Soc., 70, 4090.
[2] Pauling, L. (1960). The Nature of the Chemical Bond, 3rd ed. Cornell University
Press: Ithaca, NY.
[3] Bunn, C. W. & Howells, E. R. (1954). Nature, 174, 549.
[4] Brace, N. O. (1962). J. Org. Chem., 27, 3033.
[5] Rabolt, J. F., Russell, T. P., & Twieg, R. J. (1984). Macromolecules, 17, 2786.
[6] Turberg, M. P. & Brady, J. E. (1988). J. Am. Chem. Soc., 110, 7797.
[7] Binks, B. P., Fletcher, P. D. I., Sager, W. F. C., & Thompson, R. L. (1995). Lang-
muir, 11, 977.
[8] Binks, B. P., Fletcher, P. D. I., & Thompson, R. L. (1996). Ber. Bunsenges. Phys.
Chem., 100, 232.
¨
¨
[9] Hopken, J., Pugh, C., Richtering, W., & Moller, M. (1988). Makromol. Chem., 189,
911.
[10] Gaines, G. L. Jr. (1991). Langmuir, 7, 3054.
[11] Mahler, W., Guillon, D., & Skoulios, A. (1985). Mol. Cryst. Liq. Cryst. Lett., 2(3–4),
111.
[12] Stegemeyer, H. (1994). Liquid Crystals, Steinkopff Darmstadt, Springer: New
York.
[13] Kirsch, P. (2004). Modern Fluoroorganic Chemistry, Wiley-VCH Verlag: Weinheim.
[14] Viney, C., Russell, T. P., Depero, L. E., & Twieg, R. J. (1989). Mol. Cryst. Liq. Cryst.,
168, 63.
[15] Viney, C., Twieg, R. J., Russell, T. P., & Depero, L. E. (1989). Liq. Cryst., 5, 1783.
[16] Viney, C., Twieg, R. J., & Russell, T. P. (1990). Mol. Cryst. Liq. Cryst., 182B, 291.
[17] Broniatowski, M., Dynarowicz-Ła˛tka, P., & Witko, W. (2005). J. Fluorine. Chem.,
126, 79.
[18] Wang, J. & Ober, C. K. (1999). Liq. Cryst., 26, 637.