Superhydrophobic surfaces of electrodeposited polypyrroles bearing fluorinated liquid crystalline segments

Article abstract of DOI:10.1021/ma101914j

Two intrinsic properties of fluorinated tails (F-butyl to F-octyl) were combined in the elaboration of superhydrophobic surfaces by electrochemical polymerization: their promesogenic characteristic and their ability to increase both hydrophobicity and oleophobicity. We report the synthesis and the characterization of pyrrole monomers bearing fluorinated liquid crystalline segments. The electrodeposited corresponding polymer films were characterized by cyclic voltammetry, static and dynamic contact angle measurements, and scanning electron microscopy. Sticky superhydrophobic surfaces were obtained with a F-hexyl or a F-octyl tail. The presence of mesogenic segments improves the surface hydrophobicity and increases the surface roughness, clearly observed with F-butyl and F-hexyl chains.

Full text of DOI:10.1021/ma101914j

Macromolecules 2010, 43, 9365–9370 9365
DOI: 10.1021/ma101914j
Superhydrophobic Surfaces of Electrodeposited Polypyrroles Bearing
Fluorinated Liquid Crystalline Segments
Thierry Darmanin, Elisabeth Taffin de Givenchy, and Frederic Guittard*
ꢀ
ꢀ
ꢀ
Universite de Nice - Sophia Antipolis, Laboratoire de Chimie des Materiaux Organiques et Metalliques,
Equipe Chimie Organique aux Interfaces, Parc Valrose, 06108 Nice Cedex 2, France
Received August 19, 2010; Revised Manuscript Received October 10, 2010
ABSTRACT: Two intrinsic properties of fluorinated tails (F-butyl to F-octyl) were combined in the elabora-
tion of superhydrophobic surfaces by electrochemical polymerization: their promesogenic characteristic and
their ability to increase both hydrophobicity and oleophobicity. We report the synthesis and the character-
ization of pyrrole monomers bearing fluorinated liquid crystalline segments. The electrodeposited corre-
sponding polymer films were characterized by cyclic voltammetry, static and dynamic contact angle
measurements, and scanning electron microscopy. Sticky superhydrophobic surfaces were obtained with a
F-hexyl or a F-octyl tail. The presence of mesogenic segments improves the surface hydrophobicity and
increases the surface roughness, clearly observed with F-butyl and F-hexyl chains.
Introduction
Here, in order to combine the effect of mesogenic core in
the electrochemical polymerization of fluorinated monomers, a
Highly fluorinated tails have exceptional intrinsic properties
allowing their use in a large domain of applications going from
hydrophobic materials to liquid-crystalline compounds.1,2 Thus,
their introduction in an amphiphilic structure could lead to the
formation of well-organized mesophases. Their introduction in a
polymer decreases its surface energy due to the orientation of the
fluorinated tail at the extreme surface. However, the contact
angle with water on flat surface is rarely above 120° whatever the
length of the fluorinated tail or their proportion.3-5 Moreover, in
a polar environment, the fluorinated tails at the extreme sur-
face undergo rearrangements limiting their use. Takahara et al.6
showed that the surface rearrangements are depending on the
length of the fluorinated tail. For long fluorinated tails (more
than eight fluoromethylene units), strong interactions are present
between the fluorinated tail leading to their crystallization and
reducing their mobility. For short fluorinated tails (less than 6
fluoromethylene units), no crystallization was observed and the
dynamic surface properties were poor. Recently, to counter
the problem, the concept of mesogenic core, inserted between
the fluorinated tail and the polymer chain, was reported.7 These
mesogenic cores decreased the mobility of the fluorinated tails
and thus improved the antiwetting properties.
Fluorinated tails can also be used for the elaboration of
superhydrophobic surfaces, which have recently attracted much
interest because of their potential applications in many fields.8-12
In this domain, according to the Wenzel and Cassie-Baxter
theories,13-15 the contribution of physical parameters (roughness
and morphology) in addition to chemical parameters (fluorinated
tail for example) allowed to enhance the surface antiwetting
properties. Among the reported methods, the electrochemi-
cal polymerization of hydrophobic monomers16-21 is a choice
method (one-pot, mild conditions, morphology adjustable) for
the elaboration of micro- or nanostructured surfaces. Thus, it has
been demonstrated that the electrochemical polymerization of
semifluorinated thiophenes,18 pyrroles,19,20a 3,4-ethylenedioxy-
thiophenes,18,20 and 3,4-alkylenedioxypyrroles18,21 allowed the
deposition of films with excellent antiwetting properties.
phenyl ring was inserted between the semifluorinated tail and the
electropolymerizable pyrrole moiety. A schematic representation
of the studied monomers is given in Scheme 1a. We report the
synthesis of the monomers, their electrochemical polymerization,
and the evaluation of the surface properties of the correspond-
ing conductive polymers by static and dynamic contact angles,
imaging infrared, optical profilometry, and scanning electron
microscopy. Their surface properties will be compared to the
previously reported fluorinated polypyrroles represented in
Scheme 1b.
Experimental Section
Materials. All chemical products were purchased from Sigma-
Aldrich. Electrochemical grade of tetrabutylammonium hexa-
fluorophosphate was chosen. Gold plates (deposition of Cr þ
˚
Au 1500 A on silicon wafers) were purchased from Neyco.
Measurements. The mass spectra were obtained by electron
ionization at 70 eV with a Thermo TRACEGC of Thermo-
fischer Corp. fitted with an Automass III Multi spectrometer.
The retention times of the compounds were determined with
a 5890 series II gas chromatography from Hewlett-Packard
equipped with a capillary column HP5 (30 m, 0.32 mm): the
heating program is 60-250 °C at 10 °C/min and 30 min at
250 °C, and the standard reference is heptane. NMR spectra
were realized with a Bruker W-200 MHz. The melting points and
the thermal analyses were obtained with a Jade DSC of Perkin-
Elmer with scan rates of 10 °C/min. The polarized optical micros-
copy (POM) images were obtained with an Olympus BX60.
Electrochemical experiments were performed with an Autolab
PGSTAT 30 potentiostat from Eco Chemie B.V. equipped with
General Purpose Electrochemical System (GPES) software and
connected to a three-electrode cell. A platinum disk (area =
7.1 mm2) or a gold plate (area = a few cm2) was used as working
electrode, a glassy carbon rod as counter electrode, and a
saturated calomel electrode (SCE) as reference electrode. Static
and dynamic contact angle measurements (average of five
€
measurements) were performed with a Kruss DSA-10 contact
angle goniometer at 21 ( 1 °C. The sliding angle and the hystere-
sis were determined by the tilted-drop method with 6 μL water
*Corresponding author. E-mail: Frederic.GUITTARD@unice.fr.
r 2010 American Chemical Society
Published on Web 10/28/2010
pubs.acs.org/Macromolecules

9366 Macromolecules, Vol. 43, No. 22, 2010
Darmanin et al.
droplets. Infrared surface images were obtained in reflection
with a Spotlight 3100 FTIR microscope from Perkin-Elmer
equipped with a Spectrometer 100. Roughness parameters were
obtained with a WYKO NT1100 optical profiling system from
Veeco. Scanning electron microscopy (SEM) images were ob-
tained with a JEOL 6700F microscope.
CDCl3): 189.67, 170.18, 155.19, 133.81, 128.77, 121.97, 118.33,
116.78, 114.51, 109.21, 33.12, 31.73 (t, 2JCF = 21.9 Hz), 20.15 (t,
3JCF = 4.6 Hz). δF (188 MHz, CDCl3): -81.20 (m, 3F), -114.93
(m, 2F), -122.31 (m, 2F), -123.28 (m, 2F), -123.80 (m, 2F),
-126.56 (m, 2F). FTIR (main vibrations): ν = 3406 (N-H),
2921, 2853, 1748 (OCdO, 1663 (SCdO), 1595, 1500, 1242, 1211,
1143 cm-1. MS (70 eV): m/z (%): 607 (2) [Mþ], 228 (9)
[C13H10O3Nþ], 121 (40) [C7H4O2þ], 80 (100) [C5H6Nþ].
Synthesis of Molecules 1, 2, and 3. The synthesis of com-
pounds 2 and 3, represented in Scheme 2, was previously
reported.22-24 Compound 1 was synthesized by a similar route.
1: S-3,3,4,4,5,5,6,6,6-Nonafluorohexyl-4-hydroxybenzothio-
ate. δH (200 MHz, MeOD): 7.77 (d, 3JHH = 8.8 Hz, 2H), 6.78
(d, 3JHH = 8.8 Hz, 2H), 3.18 (t, 3JHH = 7.8 Hz, 2H), 2.49 (tt,
3JHH = 7.8, 3JHF = 17.8, 2H). δF (188 MHz, MeOD): -81.08
(m, 3F), -116.14 (m, 2F), -125.91 (m, 2F), -127.66 (m, 2F).
Synthesis of the Monomers 4, 5, and 6. 2-(1H-pyrrol-3-yl)ace-
tic acid was synthesized by a procedure developed by Lemaire
et al.25-27 N-(3-(Dimethylamino)propyl)-N0-ethylcarbodiimide
hydrochloride (EDC) (1.0 g, 5.2 mmol) was added to a solution
of 2-(1H-pyrrol-3-yl)acetic acid (0.65 g, 5.2 mmol) in acetoni-
trile. After stirring for 30 min at room temperature, 2-F-alkyl-
ethyl-4-hydroxythiobenzoate (1-3) (5.2 mmol) was added.
After a day, the solvent was removed and the crude was purified
by column chromatography (silica gel; eluent: dichloromethane)
to yield the products as white solids.
6: 4-((3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorode-
cylthio)carbonyl)phenyl 2-(1H-Pyrrol-3-yl)acetate. Yield 25%;
tr = 26.4 min. δH (200MHz, CDCl3):8.22(s, 1H),7.97(d, 3 JHH
=
8.8 Hz, 2H), 7.21 (d, 3 JHH = 8.8 Hz, 2H), 6.81 (m, 2H), 6.27 (dd,
=
3JHH = 4.2 Hz, 4JHH = 2.5 Hz, 1H), 3.79 (s, 2H), 3.28 (t, 3JHH
7.8 Hz, 2H), 2.49 (tt, 3JHH = 7.8 Hz, 3JHF = 17.8 Hz, 2H). δC
(50 MHz, CDCl3): 189.67, 170.17, 155.19, 133.82, 128.78,
=
2
121.97, 118.33, 116.78, 114.52, 109.22, 33.13, 31.75 (t, JCF
3
21.9 Hz), 20.15 (t, JCF = 4.6 Hz). δF (188 MHz, CDCl3):
-81.17 (m, 3F), -114.88 (m, 2F), -122.28 (m, 6F), -123.13
(m, 2F), -123.76 (m, 2F), -126.52 (m, 2F). FTIR (main
vibrations): ν = 3406 (N-H), 2921, 2853, 1748 (OCdO), 1663
(SCdO), 1595, 1500, 1242, 1215, 1147 cm-1. MS (70 eV): m/z
(%): 707 (2) [Mþ], 228 (13) [C13H10O3Nþ], 121 (37) [C7H4O2þ],
80 (100) [C5H6Nþ].
Results and Discussion
4: 4-((3,3,4,4,5,5,6,6,6-Nonafluorohexylthio)carbonyl)phenyl
2-(1H-Pyrrol-3-yl)acetate. Yield 45%; tr = 22.9 min. δH
(200 MHz, CDCl3): 8.22 (s, 1H), 7.97 (d, 3JHH = 8.8 Hz, 2H),
7.21 (d, 3JHH = 8.8 Hz, 2H), 6.81 (m, 2H), 6.27 (dd, 3JHH = 4.2
Hz, 4JHH = 2.5 Hz, 1H), 3.79 (s, 2H), 3.28 (t, 3JHH = 7.8 Hz,
2H), 2.49 (tt, 3JHH = 7.8 Hz, 3JHF = 17.8 Hz, 2H). δC (50 MHz,
CDCl3): 189.67, 170.17, 155.19, 133.81, 128.77, 121.97, 118.33,
116.78, 114.51, 109.21, 33.12, 31.63 (t, 2JCF = 21.9 Hz), 20.12
Monomer Synthesis. Pyrrole unit was chosen because of
its high polymerization ability. Indeed, as the liquid crystal
(LC) segments are very bulky, the replacement of the pyrrole
unit by a thiophene one, which has a lower polymerization
ability, gave nonpolymerizable monomers. Scheme 2 shows
the LC segments used in this work; they consisted in a
promesogenic semifluorinated tail bound to a phenyl by
a thioester connector. These LC units were already been
incorporated for the synthesis of other LC molecules.22-24
Their introduction, for example, inside a polyacrylate back-
bone allowed to amplify and stabilize the surface antiwetting
properties by structuring the orientation of the fluorinated
chains.24 The use of a thioester connector is very important
for the liquid-crystalline properties.22
2-F-Alkylethyl-4-hydroxythiobenzoates were obtained
from 4-hydroxybenzoic acid in excellent global yields and in
three steps from 4-hydroxybenzoic acid (Scheme 2): hydro-
xyl group protection using methyl chloroformate, coupling
of semifluorinated thiol, and hydroxyl group deprotec-
tion with a mixture of ammonium hydroxide (28% in water),
dichloromethane, and ethanol (1:1:1).
3
(t, JCF = 4.6 Hz). δF (188 MHz, CDCl3): -81.42 (m, 3F),
-115.17 (m, 2F), -124.77 (m, 2F), -126.45 (m, 2F). FTIR
(main vibrations): ν = 3406 (N-H), 2921, 2855, 1749 (OCdO),
1660 (SCdO), 1599, 1500, 1242, 1215, 1130 cm-1. MS (70 eV):
m/z (%): 507 (1) [Mþ], 228 (7) [C13H10O3Nþ], 121 (47) [C7H4-
O2þ], 80 (100) [C5H6Nþ].
5: 4-((3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctylthio)carbonyl)-
phenyl 2-(1H-Pyrrol-3-yl)acetate. Yield 32%; tr = 24.5 min. δH
(200 MHz, CDCl3): 8.22 (s, 1H), 7.97 (d, 3JHH = 8.8 Hz, 2H),
3
3
7.21 (d, JHH = 8.8 Hz, 2H), 6.81 (m, 2H), 6.27 (dd, JHH =
4.2 Hz, 4JHH = 2.5 Hz, 1H), 3.79 (s, 2H), 3.28 (t, 3JHH = 7.8 Hz,
2H), 2.49 (tt, 3JHH = 7.8 Hz, 3JHF = 17.8 Hz, 2H). δC (50 MHz,
Scheme 1. (a) Studied Monomers and (b) Previously Reported19
Pyrrole Derivatives (n = 4, 6, and 8)
Then, 2-(1H-pyrrol-3-yl)acetic acid was synthesized from
pyrrole in four steps and following the general pathway
described by Lemaire et al.25-27 This synthetic route includes
the nitrogen protection with tosyl chloride, the acylation at
the 3-position of pyrrole by Friedel-Crafts acylation using
aluminum chloride and acetic anhydride, the transposition
Scheme 2. Synthesis of the LC Segments

Article
Macromolecules, Vol. 43, No. 22, 2010 9367
Scheme 3. Synthesis of the Monomers and Corresponding Polymers
of the acetyl to methyl acetate group by Willgerodt-Kindler
reaction using thallium(III) nitrate, trimethyl orthoformate
and montmorillonite K10, the hydrolysis of the ester func-
tion, and the tosyl group with an aqueous solution of sodium
hydroxide.
Finally, fluorinated LC segments were grafted to a pyrrole
moiety to give monomers 4-6 as described in Scheme 3.
These monomers were synthesized by coupling the LC
segments with 2-(1H-pyrrol-3-yl)acetic acid. The synthesis
was performed in acetonitrile with N-(3-(dimethylamino)-
propyl)-N0-ethylcarbodiimide hydrochloride (EDC) as cou-
pling agents. The monomers were obtained in 25-45%
isolated yields. The insertion of the semifluorinated LC seg-
1
ment was confirmed by H NMR, 13C NMR, 19F NMR,
FTIR (large ester band at 1748 cm-1 and thioester at
1663 cm-1), and mass spectrometry (presence of the molec-
ular ion).
Figure 1. Phase diagram for the monomers 4, 5, and 6 with 4, 6, and 8
fluoromethylene units, respectively (I = isotropic, Sm = smectic, Cr =
crystalline).
Liquid Crystalline Behavior of the Monomers. The liquid
crystalline behavior of the monomers was determined by
combining thermal analyses obtained by differential scann-
ing calorimetry (DSC) and optical images obtained by
polarizing optical microscopy (POM). The thermal analyses
by DSC, at a scanning rate of 10 °C min-1 (cf. Supporting
Information), showed an enantiotropic mesomorphic behav-
ior of the monomers 5 and 6, which contain a perfluorohexyl
(F-hexyl) or a perfluorooctyl tail (F-octyl), respectively.
Mesophases were detectable on both heating and cooling.
For monomer 4, which contains a perfluorobutyl (F-butyl),
the mesophase was observed in a temperature range of less
than 1 °C on cooling, which revealed a monotropic behavior.
The solid-liquid crystal and liquid crystal-liquid transition
temperatures and temperature ranges of the mesophases
increased with the lengthening of the fluorinated tail. During
the heating, the temperature range of the mesophases was
about 38 °C for 6 and 12 °C for 5. During the cooling, two
crystalline phases were observed for 6. The phase diagram of
the compound as a function of the F-alkyl length is given in
Figure 1. The LC mesophases were confirmed by polarized
optical microscopy (POM) (Figure 2). The mesophases
appear as batonnets and after coalescence gave rise to fan-
shaped textures with focal-conic domains, which are char-
acteristic of smectic mesophases.28
Figure 2. Optical polarizing micrograph of 6 on cooling. Magnifica-
tion ꢀ33; T = 134 °C.
maximum of the oxidation potential peak of the monomers
ox
peak,m
ox
). The value of E
peak,m
(E
is about 1.28 V vs SCE for
the three monomers (Table 1), in comparison of the 1.25 V
for pyrrole. Indeed, the methylene spacer and the ester
connector inhibited the electron-withdrawing and electron-
donating effects of the substitutents. The polymerizability of
the monomers was studied by consecutive voltammetric
Electropolymerization. The electrochemical polymeriza-
tion of the monomers was performed in an anhydrous
acetonitrile solution containing 0.01 M of the monomer
and 0.1 M of tetrabutylammonium hexafluorophosphate
(Bu4NPF6). Single scan by voltammetry cyclic gave the
scans from a potential lower to the reduction potential of
the polymer and until a potential slightly lower than E
ox
peak,m
,

9368 Macromolecules, Vol. 43, No. 22, 2010
Darmanin et al.
Table 1. Electrochemical Data of the Monomers and Their
Corresponding Polymers (Potentials in V vs SCE)a
ox
peak,m
ox
p,opt
ox
polymer
red
E
polymer
monomer
E
E
E
4
5
1.28
1.29
1.29
1.25
1.17
1.17
1.17
1.15
0.03/0.38
0.31/0.69
0.06/0.95
0.08
-0.06/0.28
u/0.51
0.09/0.55
0.07
6
pyrrole
a u = undetermined; E
= optimal oxidation potential of the
ox
p,opt
monomer.
Figure 4. Static contact angles of the polymer surfaces (Qs
≈
150 mC cm-2).
Figure 3. Cyclic voltammogram of the monomer 5 (0.01 M) on Pt
electrode recorded in 0.1 M Bu4NPF6/CH3CN: 10 scans.
Table 2. Wettability and Roughness Parameters
roughness parameters [nm]
Qs
[mC cm-2
static contact angles
[deg] of water
]
Ra
Rq
P4
P5
150
150
75
25
150
119
154
121
106
153
330
372
86
14
351
512
641
160
21
P6
572
ox
denoted E
p,opt
. A continuous growth of polymer film at the
electrode surface was observed for all the pyrrole derivatives
(Figure 3). The cyclic voltammograms of the three substi-
tuted polymers showed two oxidation and reduction peaks,
which are an evidence of an electroactive polymer on the
surface. The electrochemical data of the polymers are given
in Table 1. In order to determine the wettability and the
morphology of the surfaces, the polymers were electrochem-
ically deposited on gold plates by chronoamperometry
(imposed potential of 1.17 V) with a deposition charge (Qs)
of 150 mC cm-2. This deposition charge gave the best con-
tact angles (see Table 2 for P5).
Surface Analyses and Discussion. Figure 4 shows the
contact angles (CA) determined with 2 μL water (γL =
72.8 mN/m), diiodomethane (γL = 50.0 mN/m), and hexa-
decane (γL = 27.6 mN/m) droplets. The contact angle values
were similar when F-hexyl or F-octyl tail was used but a
decrease of about 20° with water was observed with F-butyl
tail. The films P5 and P6 exhibited superhydrophobic prop-
erties (CAwater higher than 153°) and almost oleophobic
properties (CAhexadecane ≈ 74°), whereas nonsubstituted
polypyrrole was, in the same condition of preparation,
hydrophilic and superoleophilic. In comparison with pre-
viously reported fluorinated polypyrroles (Scheme 1b),19 the
presence of the LC segment increased the water contact angle
of about 10°-25° following the length of the fluorinated tail.
Indeed, CAwater = 136°, 130°, and 108° for the monomers
without LC segments represented in Scheme 1b and sub-
stituted with a F-octyl, F-hexyl, and F-butyl tail, respectively.
Figure 5. (a) Infrared spectra of P5 obtaining by imaging infrared and
(b) surface distribution of the ester function.
Moreover, although P5 and P6 exhibited a superhydro-
phobic behavior, the dynamic contact angle measurements
by the tilted-drop method revealed water droplets did not
roll off the surface when this one was inclined even with a
high tilt angle (90°), which means that the hysteresis was very
high as already observed in previous papers.18,19,29,30 To
confirm this important data, water droplets were deposited
on the surfaces, and after penetration of the syringe inside the
droplet, the droplet volume was increased and then reduced
to determine the advanced and receding contact angles,
respectively. Using this method, the advanced and receding

Article
Macromolecules, Vol. 43, No. 22, 2010 9369
Figure 6. SEM images of (a) P6, (c) P5, and (e) P4 and (b, d, f) their homologues without LC segment. The scale bar represents 1 μm. Substrate: gold;
salt: Bu4NPF6; Qs ≈ 150 mC cm-2
.
contact angles should be determined when the triple point
moves. However, if it was possible to determine the advanced
contact angle, the triple point did not move during the reduc-
tion of the droplet volume, which confirms the very low
receding contact angle and as a consequence the very high
hysteresis. Surfaces with both high water contact angle and
large contact angle hysteresis are known as “highly adhesive
surfaces”.31 These particular surface properties give to the
gecko its ability to climb vertical surfaces and was also
observed on the petals’ surfaces of red roses.31
This result assumes that the increase in roughness in-
creased the water contact angles but also the hysteresis
because of the possibility of water to penetrate inside the
roughness. Thus, even if the liquid-crystal segments can im-
prove the dynamic contact angles,7 in this case, this improve-
ment was canceled by the increase of the hysteresis as a
function of the surface roughness. To verify this assumption,
the surface morphology was investigated by imaging infra-
red, optical profilometry, and SEM.
The surface were analyzed by imaging infrared in reflec-
tion mode (polymer deposition on gold plate). First, these
analyses allowed to obtain the infrared spectra of the poly-
mers, as shown in Figure 5a. The polymers were confirmed
especially by the presence of two peaks: a large ester band at
1752 cm-1 and a large thioester band at 1664 cm-1. Second,
this analysis technique was used to achieve a surface func-
tional distribution by focusing on one chemical function.
Here, the focusing on the ester function, as shown in
Figure 5b, revealed variations of functional distribution
probably due to surface roughness. To confirm this hypoth-
esis and to determine the surface roughness and morphology,
the surfaces were analyzed by optical profilometry and SEM.
The study of the surface roughness by optical profilometry
(Table 2 and Supporting Information) revealed that the
surface roughness of the electrodeposited films was quite
similar for the same deposition charge whatever the fluori-
nated chain length (330 nm < Ra < 372 nm). The heights
of the biggest agglomerates were between 3.0 and 4.5 μm.

9370 Macromolecules, Vol. 43, No. 22, 2010
Darmanin et al.
The Wenzel roughness factors were calculated for P5 from
the surface obtained with Qs = 25 mC/cm-2 (Ra = 14 nm)
which was considered as a smooth surface (see Table 2).
Thus, the roughness parameters for P5 using the Wenzel
model are r=cos(121°)/cos(106°)=1.87 for Qs=75 mC cm-2
(3) Hayakawa, T.; Wang, J.; Xiang, M.; Li, X.; Ueda, M.; Ober, C. K.;
Genzer, J.; Sivaniah, E.; Kramer, E. J.; Fisher, D. A. Macromole-
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(4) Grundke, K.; Pospiech, D.; Kolling, W.; Simon, F.; Janke, A.
Colloid Polym. Sci. 2001, 279, 727–735.
(5) Xiang, M.; Li, X.; Ober, C. K.; Char, K.; Genzer, J.; Sivaniah, E.;
Kramer, E. J.; Fisher, D. A. Macromolecules 2000, 33, 6106–6119.
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and r=cos(154°)/cos(106°) = 3.26 for Qs = 150 mC cm-2
.
Figure 6a,c,e shows SEM images of P4, P5, and P6 sur-
faces obtained by electrochemical polymerization. The sur-
face morphology consisted in an assembly of micrometric
cauliflower-like structures, which are similar to the struc-
tures obtained with fluorinated polypyrroles,19 polythio-
phenes,18 or poly(3,4-propylenedioxypyrrole).21 The pre-
sence of the LC segment did not modify the nature of the
morphology. However, it is clear that the LC segment
increases the abundance of the surface microstructures espe-
cially observed with F-hexyl and F-butyl chains (Figure 6c-f ),
in agreement with their wettability, even if the surface anti-
wetting properties are the consequence of both the surface
roughness-morphology and surface chemistry. For exam-
ple, in the case of F-butyl chains, smooth surfaces19 were
obtained without LC segment (Figure 6f) and micrometric
cauliflower microstructures with it (Figure 6e).
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Conclusion
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Langmuir 2010, DOI: 10.1021/la103310m, in press.
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(22) Taffin de Givenchy, E.; Guittard, F.; Bracon, F.; Cambon, A. Liq.
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Here, we report the synthesis and characterization of pyrrole
derivatives bearing semifluorinated liquid-crystalline segments.
These monomers were employed for the elaboration of super-
hydrophobic polymer films deposited by electrochemical poly-
merization. Superhydrophobic and oleophobic films with a sticky
behavior were obtained using a F-hexyl and a F-octyl tail. The
surface morphology consisted in cauliflower-like microstructures
and was independent of the fluorinated tail length. The presence
of LC behavior from monotropic (F4) to enantiotropic (F6, F8)
seems to be in strong correlation with the modification of
wettability. In comparison with previously reported fluorinated
pyrroles, the presence of the LC segment improved the surface
hydrophobicity by increasing the surface structuration switching
hydrophobic to superhydrophobic materials (P5, P6) and open-
ing new way for the development of antiwetting electro-optical
devices.
ꢀ
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ꢀ
1–5. (b) Fornasieri, G.; Guittard, F.; Geribaldi, S. Liq. Cryst. 2003, 30,
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(27) Ho-Hoang, A.; Fache, F.; Boiteux, G.; Lemaire, M. Synth. Met.
Supporting Information Available: DSC curves of the mono-
mers and optical profilometer images of the polymers. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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(28) Hamley, I. W. Introduction to Soft Matter. Polymer, Colloids,
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References and Notes
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(1) Gladysz, J. A.; Curran, D. P.; Horvath, I. T. Handbook of Fluorous
Chemistry; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2004.
(2) Kirsch, P. Modern Fluoroorganic Chemistry; Wiley-VCH Verlag
GmbH & Co. KGaA: Weinheim, 2004.
(31) (a) Feng, L.; Zhang, Y.; Xi, J.; Zhu, Y.; Wang, N.; Xia, F.; Jiang, L.
Langmuir 2008, 24, 4114–4119. (b) Cho, W. K.; Choi, I. S. Adv. Funct.
Mater. 2008, 18, 1089–1096.