LC acrylic monomers incorporating monothiobenzoate unit

Article abstract of DOI:10.1080/15421400590955154

The development of LC monophenyl unit is of a great interest for reach low cost LC materials. The aim of this work was to demonstrate the possibility to obtain monomer incorporating single phenyl unit for LC field. We report the synthesis and the characte

Full text of DOI:10.1080/15421400590955154

This article was downloaded by: [Tufts University]
On: 31 October 2014, At: 13:58
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
LC Acrylic Monomers
Incorporating
Monothiobenzoate Unit
Laurent Caillier a , Frédéric Guittard a , Elisabeth
Taffin de Givenchy a & Serge Geribaldi a
a Laboratoire de Chimie des Matériaux Organiques
et Métalliques (CMOM), Faculté des sciences ,
Université de Nice Sophia-Antipolis , Parc Valrose,
France
Published online: 31 Aug 2006.
To cite this article: Laurent Caillier , Frédéric Guittard , Elisabeth Taffin de Givenchy
& Serge Geribaldi (2005) LC Acrylic Monomers Incorporating Monothiobenzoate
Unit, Molecular Crystals and Liquid Crystals, 437:1, 71/[1315]-80/[1324], DOI:
10.1080/15421400590955154
To link to this article: http://dx.doi.org/10.1080/15421400590955154
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,

and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
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. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Mol. Cryst. Liq. Cryst., Vol. 437, pp. 71=[1315]–80=[1324], 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590955154
LC Acrylic Monomers Incorporating Monothiobenzoate
Unit
Laurent Caillier
´
´
Frederic Guittard
Elisabeth Taffin de Givenchy
Serge Geribaldi
´
´
Laboratoire de Chimie des Materiaux Organiques et Metalliques
´
´
(CMOM), Faculte des sciences, Universite de Nice Sophia-Antipolis,
Parc Valrose, France
The development of LC monophenyl unit is of a great interest for reach low cost LC
materials. The aim of this work was to demonstrate the possibility to obtain mono-
mer incorporating single phenyl unit for LC field. We report the synthesis and the
characterization of acrylic monomers in fluorinated series which differ by the
lengthening of the hydrocarbon spacer linking the acrylic part to the ‘‘mesogenic’’
core. LC behaviour was determined by DSC and POM apparatus. The increasing
of the length of this hydrocarbon spacer dramatically decreases the span of the
mesophase of type smectic. For a long spacer no mesomorphism is observed.
Keywords: acrylic; monophenyl; perfluoro; smectic; thiobenzoate
1. INTRODUCTION
Low cost polymers need the molecular design of monomers incorporat-
ing monophenyl unit [1]. In a previous work, we have described for the
first time the possibility of obtaining enantiotropic liquid crystals con-
taining a single phenyl group over a wide temperature range but with-
out hydrogen bonding [2,3]. This kind of behaviour can be explained by
the presence of perfluorinated tail as ‘‘pro-mesogenic’’ part linked to a
single unit core through a spacer [4]. It is worth noting that the careful
choice of the spacer joining the fluorinated chain to the mesogenic core
The authors thank Prof. N. Sbirrazzuoli (Lab.CMOM Nice) for the recording of DSC
data, and Atofina for the gift of F-octylethane-1-thiol. LC thanks MENRT for a grant.
´
´
´
Address correspondence to Frederic Guittard, Laboratoire de Chimie des Materiaux
´
´
´
Organiques et Metalliques (CMOM), Faculte des sciences, Universite de Nice Sophia-
Antipolis, Parc Valrose, 06108 Nice Cedex 2, France. E-mail: guittard@unice.fr
71=[1315]

72=[1316]
L. Caillier et al.
FIGURE 1 Investigated monomers.
can govern the enantiotropic or monotropic LC character [5–18]. In pre-
vious work we have also highlighted the thioester connector as one of the
best linking group for the expression of the best segregation into distinct
microdomains that is favourable to the appearance of a well organized
phase such as a liquid crystal phase [19–22]. In order to reach LC poly-
mers containing a single thiobenzoate unit as rigid core, we present in
this work the preparation, the characterization and the LC evaluation
of a series of hemifluorinated compounds as described in Figure 1.
The mesomorphic behaviour of all compounds has been studied by a
combination of differential scanning calorimetry (DSC) and polarizing
optical microscopy (POM). The effect of the hydrocarbon spacer bond-
ing the thiobenzoate core to the acrylic part will be discussed.
2. EXPERIMENTAL PART
2.1. Materials
4-hydroxybenzoic acid (99%), methyl chloroformate (99%), N,N0-dicyclo-
hexylcarbodiimide (DCC, 99%), 11-bromoundecan-1-ol (97%), Triphenyl-
´
phosphine (99%), 4-hydroxybenzaldehyde (98%), 2-hydroxyethylacrylate
(95%) were purchased from Aldrich and used as received. Acryloyl
chloride (97%) was purchased from Fluka and was used without further
purification. Diisopropylazodicarboxylate (95%) was purchased from
Merck. 2-(perfluorooctyl)ethane-1-thiol was given by Atofina. Unless
specified the solvents were of unpurified reagent grade.
2.2. Methods
Confirmation of the structures of the intermediates and products
was obtained by nuclear magnetic resonance (NMR) and Mass

Monothiobenzoate Acrylic Monomers
73=[1317]
Spectrometry (MS). NMR spectroscopy was carried out using a Bru-
ker AC 200 MHz spectrometer. Spectra were recorded using deuter-
1
ated solvent with TMS as internal reference for H NMR and CFCl3
for 19F NMR. MS was carried out using a Thermo Finnigan spec-
trometer with an EI mode (70 eV) and a direct introduction. The
purity of the monomers was determined by thin layer chromato-
graphy. The initial phase assignments and corresponding transition
temperatures were determined using an Olympus BX 60 optical
microscope equipped with crossed polarizers. The samples were
thermostated by means of a Linkam Scientific Instruments LTS
350 heating unit and TMS 94 temperature control by the same
manufacturer. Temperatures and enthalpies of transition were
investigated by DSC using a Mettler Toledo DSC 821 instrument.
Samples of 5–10 mg were placed in aluminium capsules and heated
in a static nitrogen atmosphere. The heating and cooling curves
were obtained at the rate of 5 or 10ꢀC minꢁ1. The phase transition
temperatures of the monomers were extrapolated as the onset
temperatures. The phase transitions temperatures of the polymers
were taken as the maximum temperatures in the DSC enthalpic
peaks.
2.3. Synthesis
The synthesis 2-perfluorooctylethyl-4-acryloyloxythiobenzoate (F8C0),
2-perfluorooctylethyl-4-(2-acryloyloxyethyloxy)thiobenzoate
(F8C2)
and 2-perfluorooctylethyl-4-(11-acryloyloxyundecyloxy)thiobenzoate
(F8C11) are described in detail in Figure 2. Yields are reported
in Table 1.
4-methoxycarbonyloxybenzoic Acid (1)
To a solution of sodium hydroxide (2.40 g, 60 mmol) in water (60 mL)
which was maintained at ꢁ10ꢀC, 4-hydroxybenzoic acid (2.76 g,
20 mmol) was added under vigorous stirring. Methyl chloroformate
(3.78 g, 40 mmol) was added dropwise at a temperature lower to
ꢁ5ꢀC. The reaction mixture was allowed to room temperature and
stirred overnight. The resulting solution was acidified by HCl (10%)
to pH 5 with the formation of a thick precipitate. The solid was filtered
off, washed with water and finally dried to yield 1 as a white solid
(yield 92%).
1H NMR (CD3OD=TMS, d ppm J Hz): 3.91 (3H, CH3O, s); 7.31
(2Har, d, J ¼ 9.0), 8.09 (2Har, d, J ¼ 9.0); the acid proton was not
observed.

74=[1318]
L. Caillier et al.
FIGURE 2 Synthetic route to monomers. Reagents and conditions: (i) NaOH,
0ꢀC; (ii) (ix) DCC, CH2Cl2; (iii) NH3, EtOH; (iv) (vi) Et2O=N(Et)3, 0ꢀC; (v)
TPP=DIAD, THF; (vii) K2CO3, Acetone, (viii) CrO3,H2SO4, Acetone.
TABLE 1 Yields for Monomers
Cpd nꢀ
RF value
Spacer length
Yield
Overall
1
2
3
–
–
–
–
0
2
11
11
11
11
92
93
100
80
56
79
76
75
84
–
–
–
68
48
–
–
–
38
C8F17
C8F17
C8F17
C8F17
–
F8C0
F8C2
4
5
–
–
6
F8C11
C8F17

Monothiobenzoate Acrylic Monomers
75=[1319]
2-(perfluorooctyl)ethyl-4-hydroxythiobenzoate (3)
To a dichloromethane solution (50 mL) of 4-methoxycarbonyloxy-
benzoic acid (1) previously prepared (11mmol), was added 11 mmol of
DCC (N, N0-dicyclohexylcarbodiimide) and 2-(perfluoro-n-alkyl)ethane-
1-thiol (10 mmol). The reaction mixture was then stirred for 12 hours
at room temperature and the dicyclohexylurea precipitated was filtrered
off. The crude product was finally purified by column chromatography
over silica gel using dichloromethane=hexane (3=2) as eluent to give a
white solid (2). This solid (10 mmol) was then stirred during 4 hours in
15 mL of aqueous ammoniac (30%), 15 mL of dichloromethane and
10 mL of ethanol. Water was eliminated using an azeotropic distillation
with ethanol and lyophilization to give a white product (3) which can
be used without any purification.
1
3c: H NMR (CDCl3=TMS, d ppm J Hz), 2.48 (2H, CF2CH2CH2, tt,
JHH ¼ 8.1, JHF ¼ 18.6); 3.26 (2H, CF2CH2CH2, t, J ¼ 8.1); 6.93 (2Har,
d, J ¼ 8.95), 7.82 (2Har, d, J ¼ 8.95); 9.36 (phenolic acid proton).
2-(perfluorooctyl)ethyl-4-acryloyloxythiobenzoate (F8C0)
To a stirred solution of 3 (10 mmol), in freshly distilled diethylic
ether (30 mL), under inert atmosphere (N2) and at the temperature
of 0ꢀC, we added dropwise acryloyl chloride (17.5 mmol). The solution
was maintained at 0ꢀC for 2 hours and then stirred for 12 hours at
room temperature. The precipitated salt was filtered off and the
solvent removed under vacuum. The crude product was finally
purified by column chromatography over silica gel using dichloro-
methane=hexane (2=1) as eluent to give a white solid (F8C0).
F8C0: 1H NMR (CDCl3=TMS, d ppm J Hz), 2.48 (2H, CF2CH2CH2, tt,
JHH ¼ 8.85, JHF ¼ 18.30); 3.22 (2H, CF2CH2CH2, t, J ¼ 8.85); 6.08 (1H,
CH ¼ cis, dd, JHH ¼ 1.75, Jcis ¼ 10.10); 6.22 (1H, CH ¼ gem, dd,
Jcis ¼ 10.10, Jtrans ¼ 17.20); 6.43 (1H, CH ¼ trans, dd, JHH ¼ 1.75,
Jtrans ¼ 17.20); 7.96 (2Har, d, J ¼ 8.95), 7.29 (2Har, d, J ¼ 8.95). 19F
NMR (CDCl3=CFCl3, d ppm), ꢁ82 (CF3, m), ꢁ115.5 [(CF2)a, m],
ꢁ123 [(CF2)b,c,d, m], ꢁ124 [(CF2)e, m], ꢁ124.5 [(CF2)f, m], ꢁ127 [(CF2)g,
m]. MS (70 eV) m=z (%), 55 (98.2%); 65 (41.6%); 69 (7.9%); 92 (100%);
121 (100%); 175 (100%); 572 (21.6%).
2-perfluorooctylethyl-4-(2-acryloyloxyethyloxy)thiobenzoate
(F8C2)
Under Nitrogen atmosphere was added to a solution of 2-(perfluor-
ooctyl)ethyl-4-hydroxythiobenzoate (3) (10 mmol), DIAD (diisopropyl-
azodicarboxylate) (10 mmol) in THF freshly distilled, a solution of
hydroxyethylacrylate (10 mmol) and TPP (triphenylphosphine)

76=[1320]
L. Caillier et al.
(10 mmol) in THF freshly distilled. The solution was stirred for 18
hours. The solvent was removed under vacuum and the mix treated
with diethylic ether. The crude product was finally purified by column
chromatography over silica gel using dichloromethane as eluent to
give a white solid (F8C2).
1
F8C2: H NMR (CDCl3=TMS, d ppm J Hz), 2.48 (2H, CF2CH2CH2,
tt, JHH ¼ 7.70, JHF ¼ 18.30); 3.23 (2H, CF2CH2CH2, t, J ¼ 7.70); 4.32
(2H OCH2CH2OC(O), d, JHH ¼ 8.85), 4.55 (2H OCH2CH2OC(O), d,
JHH ¼ 8.85), 5.95 (1H, CH ¼ cis, dd, JHH ¼ 1.75, Jcis ¼ 10.25); 6.16
(1H, CH ¼ gem, dd, Jcis ¼ 10.25, Jtrans ¼ 17.20); 6.45 (1H, CH ¼ trans,
trans, dd, JHH ¼ 1.65, Jtrans ¼ 17.20); 7.96 (2Har, d, J ¼ 8.85), 7.00
(2Har, d, J ¼ 8.85). 19F NMR (CDCl3=CFCl3, d ppm), ꢁ82 (CF3, m),
ꢁ115.5 [(CF2)a, m], ꢁ123 [(CF2)b,c,d, m], ꢁ124 [(CF2)e, m], ꢁ124.5
[(CF2)f, m], ꢁ127 [(CF2)g, m]. MS (70 eV) m=z (%), 55 (98.7%); 99
(100%); 121 (15.06%); 92 (100%); 69 (7.74%), 65 (13.62%), 572 (1.0%).
2-perfluorooctylethyl-4-(11-acryloyloxyundecyloxy)-
thiobenzoate (F8C11)
To a dichloromethane solution (50 mL) of 6 previously prepared by
classical methods (11 mmol), we added 11 mmol of DCC (N,N0-dicyclo-
hexylcarbodiimide) and 2-(perfluoro-n-alkyl)ethane-1-thiol (10 mmol).
The reaction mixture was then stirred for 12 hours at room tempera-
ture and the dicyclohexylurea precipitated was filtrered off. The crude
product was finally purified by column chromatography over silica gel
using dichloromethane=hexane (3=2) as eluent to give a white solid.
Yield 38%.
F8C11: 1H NMR (CDCl3=TMS, d ppm J Hz), 2.48 (2H, CF2CH2CH2, tt,
JHH ¼ 7.7, JHF ¼ 18.30); 3.23 (2H, CF2CH2CH2, t, J ¼ 7.7); 4.07
(UOCH2, t, JHH ¼ 6.35); 3.93 (CH2OC(O), t, JHH ¼ 6.35); 4.07
(UOCH2CH2, q, JHH ¼ 6.35); 3.93 (CH2CH2OC(O), q, JHH ¼ 6.35); 1.25
(CH2(CH2)7CH2 multiplet); 5.95 (1H, CH ¼ cis, dd, JHH ¼ 1.65,
Jcis ¼ 10.25); 6.16 (1H, CH ¼ gem, dd, Jcis ¼ 10.25, Jtrans ¼ 17.20); 7.0
(1H, CH ¼ trans, dd, JHH ¼ 1.65, Jtrans ¼ 17.20); 7.96 (2Har, d,
J ¼ 8.85), 7.92 (2Har, d, J ¼ 8.85). 19F NMR (CDCl3=CFCl3, d ppm),
ꢁ82 (CF3, m), ꢁ115.5 [(CF2)a, m], ꢁ123 [(CF2)b, c,d, m], ꢁ124 [(CF2)e,
m], ꢁ124.5 [(CF2)f, m], ꢁ127 [(CF2)g, m]. MS (70 eV) m=z (%), 55
(36.81%); 65 (7.58%); 69 (7.9%); 92 (100%); 175 (100%); 345 (4.79%);
572 (1.33%).
3. RESULTS AND DISCUSSIONS
Preparation of the monophenyl monomers was performed according to
two different pathways showed in Figure 2.

Monothiobenzoate Acrylic Monomers
77=[1321]
FIGURE 3 (a) Optical polarizing micrograph displayed by F8C0 on cooling
from isotropic melt (temperature 90ꢀC, Â33); (b) Optical polarizing micrograph
displayed by F8C2 on cooling from isotropic melt (temperature 64ꢀC, Â33).

78=[1322]
L. Caillier et al.
The thioesterification of 4-hydroxybenzoic acid was accomplished
by the protection of the hydroxy substituent of the 4-hydroxybenzoic
acid, followed by the coupling of the carboxylic acidic group with a fluori-
nated thiol in presence of N,N0-dicyclohexylcarbodiimide (DCC) and
finally deprotection of the hydroxy group in basic conditions to yield to
the intermediate (3). The carbonate protecting group was selected
because deprotection occurs under mild conditions which do not affect
thioester linkage. The deprotection with aqueous ammonia (30%) was
carried out in a ethanol=CH2Cl2 to solubilized all compounds. This
quickly procedure (4 hours) gives quantitatively the hydroxyl derivative.
F8C0 was obtained by coupling 3 with acryloyl chloride in presence
of triethylamine. Furthermore 3 yields to F8C2 by grafting with
(hydroxyethyl)acrylate using classical Mitsunobu’s conditions
[23]. We prepared F8C11 using another specific synthetic pathway.
11-bromoundecyl acrylate (4) is coupled (Williamson mild conditions
with the use of potassium carbonate) with 4-hydroxybenzaldehyde to
give 5. The use of 4-hydroxybenzaldehyde eliminated a protec-
tion=deprotection step of the carboxylic acid function. Oxidation of
aldehyde in corresponding acid (6) is carried out with Jones reactant,
i.e., relatively mild conditions. Finally coupling 6 with 2-(perfluorooc-
tyl) ethane-1-thiol in presence of DCC gave F8C11. The different
yields are reported in Table 1.
Monomers were studied by Polarizing Optical Microscopy (P.O.M.)
and Differential Scanning Calorimetry (DSC) on heating and cooling
with a scanning rate of 10ꢀC=min. F8C0 and F8C2 exhibit an enantio-
tropic mesophase, identified as smectic by the observation of typical
focal conic fans (Figs. 3a and 3b) while F8C11 does not present any
L.C. behavior.
Our measurements showed that the L.C. gap of the compounds
is dependant of the spacer chain (n ¼ 0, 2, 11). The corresponding
TABLE 2 Transition Temperatures for Monomers Observed on Heating from
DSC (Scanning Rate 10ꢀC minꢁ1
)
Transition temperature (ꢀC)a
SmA
Enthalpies (J.gꢁ1
)
Compound
C
I
DHC–S
DHS–I
F8C0
F8C2
F8C11
.
.
.
98
(83b)
53
.
.
131
86
.
.
ꢁ57,98
ꢁ11,72
ꢁ63,26
–
aC, crystal; Sm, smectic; I, isotropic
bObserved by polarized microscopy; () monotropic transition.

Monothiobenzoate Acrylic Monomers
79=[1323]
transition temperature and enthalpy from DSC experiments are listed
in Table 2.
The effect of the spacer length (x value) was studied for F8Cx with
x ¼ 0, 2, 11. Increasing the spacer reduces dramatically melting and
clearing point temperature and the mesomorphic range (from F8C0
to F8C2) until a total disappearance of the liquid crystal properties
for a long chain (F8C11). Furthermore, F8C2 is only monotrope while
F8C0 is enantiotrope.
CONCLUSION
In this paper we have described the preparation and characterization
of the mesomorphic properties of a series of acrylic monomers of type
monothiobenzoate which differs by the length of the hydrocarbon
spacer bonding the acrylic part to the rigid core. Increasing the length
of this hydrocarbon spacer strongly influences the clearing point. For a
low value of the spacer, smectic A mesophase is recorded. The increas-
ing methylene number of this spacer leads to no LC behaviour. The
widest mesomorphic range of this series is obtained when the hydro-
carbon spacer is suppressed. The molecular design of such monomers
leads us the possibility to the preparation of low cost LC polymers for
surface treatment or to reach low surface energy materials.
REFERENCES
´
[1] Fornasieri, G., Guittard, F., Taffin de Givenchy, E., & Geribaldi, S. (2004). Polymer,
(submitted).
´
[2] Fornasieri, G., Guittard, F., & Geribaldi, S. (2003). Liq. Cryst., 30, 663.
´
[3] Fornasieri, G., Guittard, F., & Geribaldi, S. (2004). Liq. Cryst., 31, 491.
´
[4] Fornasieri, G., Guittard, F., Taffin de Givenchy, E., & Geribaldi, S. FR Patent,
registred number 0300206 (2003).
[5] Takenaka, S. (1992). J. Chem. Soc. Chem. Commun., 1748.
[6] Bao, X. & Dix, L. R. (1996). Mol. Cryst. Liq. Cryst., 281, 291.
[7] Okamoto, H., Murai, H., & Takenaka, S. (1997). Bull. Chem. Soc. Jpn., 70, 3136.
[8] Johansson, G., Percec, V., Ungar, G., & Smith, K. (1997). Chem. Mater., 9, 164.
[9] Duan, M., Okamoto, H., Petrov, V. F., & Takenaka, S. (1998). Bull. Chem. Soc. Jpn.,
71, 2735.
[10] Okamoto, H., Yamada, N., & Takenaka, S. (1998). J. Fluorine Chem., 91, 125.
[11] Duan, M., Okamoto, H., Petrov, V. F., & Takenaka, S. (1999). Bull. Chem. Soc. Jpn.,
72, 1637.
[12] Petrov, V. F., Duan, M., Okamoto, H., & Takenaka, S. (2000). Mol. Cryst. Liq.
Cryst., 350, 187.
[13] Taffin de Givenchy, E., Guittard, F., Bracon, F., & Cambon, A. (1999). Liq. Cryst.,
26, 1163.
[14] Taffin de Givenchy, E., Guittard, F., Bracon, F., & Cambon, A. (1999). Liq. Cryst.,
26, 1371.

80=[1324]
L. Caillier et al.
´
[15] Taffin de Givenchy, E., Guittard, F., Geribaldi, S., & Cambon, A. (1999). Mol. Cryst.
Liq. Cryst., 332, 1.
[16] Guittard, F., Sixou, P., & Cambon, A. (1995). Liq. Cryst., 19, 667.
[17] Guittard, F., Sixou, P., & Cambon, A. (1997). Mol. Cryst. Liq. Cryst., 308, 83.
[18] Diele, S., Lose, D., Kruth, H., Pelzl, H., Guittard, F., & Cambon, A. (1996). Liq.
Cryst., 21, 603.
[19] Tschierske, C. J. (1998). Mater. Chem., 8(7), 1485.
[20] Inoi, T. (1994). Organofluorine: Chemistry, Principles and Commercial Applica-
tions, New York Plenum Press: New York.
´
[21] Guittard, F., Taffin de Givenchy, E., Geribaldi, S., & Cambon, A. (1999). J. Fluorine
Chem., 100, 85.
´
[22] Guittard, F. & Geribaldi, S. (2001). In: Anisotropic Organic Materials – Approaches
to Polar Order, Glaser, R. & Kaszynski, P. (Eds.), ACS Symposium Series,
American Chemical Society: Washington D.C., 180.
[23] Mitsunobu, O. (1981). Synthesis, 1, 1.