Liquid crystalline 4-(2,3 Dihydroxypropoxy) diphenyl 4-n-alcoxy acids

Article abstract of DOI:10.1080/15421406.2011.609468

4-(2,3 Dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid and 4-(2,3 dihydroxypropoxy) diphenyl 4-oxy-undecanoic acid have been synthesized and analyzed by IR and NMR experiments. The liquid crystalline character and the phase transitions of these two acids have been studied by differential scanning calorimetry (DSC) and variable temperature X-ray diffraction (VTXRD). These two liquid crystalline monomers are designed to be flexible, rigid and polyfunctional, so that they can be used in the synthesis of new macromolecules with side chain liquid crystals.

Full text of DOI:10.1080/15421406.2011.609468

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Liquid Crystalline 4′-(2,3
Dihydroxypropoxy) Diphenyl 4-n-Alcoxy
Acids
Delia López-Velázquez a , Armando R. Hernández-Sosa a , Ernesto
Pérez b & Susana Castillo-Rojas c
a Fac. de Ciencias Químicas (Antiguo edificio de la Fac. de C.
Quím.), BUAP. Blvd. de la 14 Sur y Avenida San Claudio , Cd.
Universitaria. Col San Manuel. Puebla , Pue., C.P. 72500, México
b Instituto de Ciencia y Tecnología de Polímeros, CSIC , Juan de la
Cierva 3, 28006 , Madrid , Spain
c Instituto de Ciencias Nucleares, Universidad Nacional Autónoma
de México , Circuito Exterior, Ciudad Universitaria, 04510 , México ,
D.F.
Published online: 11 Jan 2012.
To cite this article: Delia López-Velázquez , Armando R. Hernández-Sosa , Ernesto Pérez & Susana
Castillo-Rojas (2012) Liquid Crystalline 4′-(2,3 Dihydroxypropoxy) Diphenyl 4-n-Alcoxy Acids,
Molecular Crystals and Liquid Crystals, 553:1, 175-184, DOI: 10.1080/15421406.2011.609468
To link to this article: http://dx.doi.org/10.1080/15421406.2011.609468
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Mol. Cryst. Liq. Cryst., Vol. 553: pp. 175–184, 2012
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2011.609468
Liquid Crystalline 4ꢀ-(2,3 Dihydroxypropoxy)
Diphenyl 4-n-Alcoxy Acids
1,∗
´
´
DELIA LOPEZ-VELAZQUEZ,
1
2
´
´
ARMANDO R. HERNANDEZ-SOSA, ERNESTO PEREZ,
AND SUSANA CASTILLO-ROJAS3
1Fac. de Ciencias Qu´ımicas (Antiguo edificio de la Fac. de C. Qu´ım.), BUAP.
Blvd. de la 14 Sur y Avenida San Claudio, Cd. Universitaria. Col San Manuel.
Puebla, Pue., C.P. 72500, Me´xico
2Instituto de Ciencia y Tecnolog´ıa de Pol´ımeros, CSIC, Juan de la Cierva 3,
28006-Madrid, Spain
3Instituto de Ciencias Nucleares, Universidad Nacional Auto´noma de Me´xico,
Circuito Exterior, Ciudad Universitaria, 04510 Me´xico, D.F.
4ꢀ-(2,3 Dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid and 4ꢀ-(2,3 dihydroxypropoxy)
diphenyl 4-oxy-undecanoic acid have been synthesized and analyzed by IR and NMR
experiments. The liquid crystalline character and the phase transitions of these two acids
have been studied by differential scanning calorimetry (DSC) and variable temperature
X-ray diffraction (VTXRD). These two liquid crystalline monomers are designed to
be flexible, rigid and polyfunctional, so that they can be used in the synthesis of new
macromolecules with side chain liquid crystals.
Keywords Dihydroxypropoxy diphenyl 4-n-alcoxy acids; liquid crystalline diol-acid
monomers
Introduction
Biphenyl derivatives have been extensively studied owing to their application in liquid crys-
tal displays [1] and because they are able to undergo functionalization reactions, providing
access to a variety of interesting compounds in different research fields [2, 3].
One of these fields is their use for obtaining liquid crystalline polymers with mesogenic
side chains, which have attracted special interest because of the possible applications in the
fields of non-linear optics, optical storage and electro-optic displays [4]. These polymers
can be obtained either by chemical modification of a prepolymer with a functionalized
liquid crystal or by polymerization of a liquid crystal monomer.
Among the different functionalities, diol-acid compounds are important in both
supramolecular chemistry [5] and polymer chemistry [6, 7]. In the present work, 4ꢀ-(2,3
dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid and 4ꢀ-(2,3 dihydroxypropoxy) diphenyl
4-oxy-undecanoic acid (see structures in Fig. 1) were prepared and their properties are
∗Address correspondence to Delia Lo´pez-Vela´zquez, Fac. de Ciencias Qu´ımicas (Antiguo edifi-
cio de la Fac. de C. Qu´ım.), BUAP. Blvd. de la 14 Sur y Avenida San Claudio, Cd. Universitaria. Col
San Manuel. Puebla, Pue., C.P. 72500, Me´xico. E-mail: lopezd2009@yahoo.com.mx
175

´ ´
D. Lopez-Velazquez et al.
176
Figure 1. Structure formulae of the 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid and
4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-undecanoic acid monomers.
being investigated for the first time. The title compounds are potential monomers which
may form liquid crystals polymers. The phase transitions of these two acids have been
studied by differential scanning calorimetry (DSC). The mesomorphic behavior of 4ꢀ-(2,3
dihydroxypropoxy) diphenyl 4-oxy-hexanoic is analyzed by variable-temperature X-ray
diffraction (VTXRD). The corresponding analysis for 4ꢀ-(2,3 dihydroxypropoxy) diphenyl
4-oxy-undecanoic acid is more complicated, due to the overlapping of the different tran-
sitions, as will be shown below, so that its mesomorphic behavior will be reported in due
course.
Experimental
Materials
The following reagents werepurchasedfromAldrich Chemical Co. and usedas received, un-
less otherwise noted: 4,4ꢀ-dihydroxybiphenyl, 6-bromohexanoic acid, 11-bromoundecanoic
acid, 6-bromohexanoyl chloride, 4-chloromethyl-2,2-dimethyl-1,3-dioxolane, thionyl chlo-
ride and KOH.
Benzyl alcohol, pyridine and DMF were also obtained from Aldrich and distilled from
CaH2 prior to use. Reagent grade dichloromethane was distilled from CaH2 under argon.
Acetic acid, ethanol, hexane and K2CO3 were purchased from JT. Beaker (reagent
grade) and were used without further purification.
For column chromatography we used a MN Kieselgel 60(0.063-0.2mm). The eluents
are given at the individual compounds.
Synthesis
The synthesis of 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-n-alcoxy acids involved a pro-
tection deprotection method [8]. The synthetic route for these acids is illustrated in
Scheme 1, involving several steps, as follows: Step 1) Protection of the carboxylic acid of

Liquid Crystalline 4ꢀ-(2,3 Dihydroxypropoxy) Diphenyl 4-n-Alcoxy Acids
177
Scheme 1. Synthetic route for 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid and 4ꢀ-(2,3
dihydroxypropoxy) diphenyl 4-oxy-undecanoic acid monomers.
6-bromohexanoic acid with benzyl alcohol to yield Benzyl 6-bromo hexanoate (5). Us-
ing the commercial available acyl chloride or preparing it by the well known reaction of
thionyl chloride [9] with the benzyl alcohol; Step 2) Preparation of (7) by etherification of
4,4ꢀ-dihydroxybiphenyl with the chain extender benzyl 6-bromohexanoate using standard

´ ´
D. Lopez-Velazquez et al.
178
procedures for a Williamson ether synthesis; Step 3) Etherification of 4-chloromethyl-2,2-
dimethyl-1,3-dioxolane with compound 7 using standard procedures for a Williamson ether
synthesis, and Step 4) Cleavage of the benzylic ester (11) and 1,3-dioxolane with acetic
acid to afford the diol-acid monomer 15 or 16.
The synthesis of the 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid and 4ꢀ-
(2,3 dihydroxypropoxy) diphenyl 4-oxy-undecanoic acid monomers follows the same tech-
nique. The synthetic procedure for the preparation of 4ꢀ-(2,3 dihydroxypropoxy) diphenyl
4-oxy-hexanoic acid is given as an example.
The particular conditions for any of these steps are given below.
Preparation of the acyl chlorides (3, 4): They were be prepared by treating 4ꢀ-(2,3
dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid or 4ꢀ-(2,3 dihydroxypropoxy) diphenyl
4-oxy-undecanoic acid with an excess of thionyl chloride. The excess thionyl chloride is
distilled off to give, as the residue, the corresponding acyl chloride.
Preparation of the benzyl esters (5): Esterification of 6-bromohexanoyl chloride
with benzyl alcohol. The crude acid chloride 3 (2.2 g, 10 × 10−3 mol) was dissolved
in dry dichloromethane (20 ml) and added to a mixture of benzyl alcohol (2.2 g, 20 ×
10−3 mol), dry pyridine (0.98 mL) in dry dichloromethane (70 mL). The reaction mixture
was stirred for 18 hrs and then acidified with 2% aq. HCl. The organic layer was separated
and washed with water until it become neutral. The solvent was removed and the residue
was dried under a vacuum overnight. The crude product was subsequently purified by
column chromatography on silica gel with dichloromethane and hexane. The pure product
5 (2.25 g, 7.89 × 10−3 mol, 77.5%) was obtained as a pale yellow liquid from vacuum
distillation.
IR: ν (C O), 1732 cm−1; ν (C O), 1253 cm−1; ν (CAr−H), 3034 cm−1; ν (Csp3−H),
2940 cm−1; ν (C-Br), 697 cm−1
.
1H NMR (400 MHz, CDCl3) δ (ppm): 3.38 ppm (CH2-Br, 2H1); 1.81 ppm (CH2, 2H2);
1.46 ppm (CH2, 2H3); 1.87 ppm (CH2, 2H4); 2.37 ppm (CH2, 2H5); 5.12 ppm (CH2-ꢀ,
2H7), 7.35 ppm (C-HAr, 5H9-11). 13C NMR (100 MHz, CDCl3) δ (ppm): C1,33.03 ppm; C2
33.45 ppm; C3, 27.60 ppm; C4, 24.05 ppm; C5, 34.03 ppm; C6, 173.23 ppm; C7, 66.16
ppm; C8, 136.00 ppm; C9, 127.76 ppm; C10, 128.55 ppm; C11, 128.21 ppm.
Preparation of the intermediate 7: It was synthesized from 5 and 4,4ꢀ-
dihydroxybiphenyl using a typical Williamson ether reaction conditions. After 23 hr
reaction, the suspension was allowed to cool. The KCO3 was filtered off and the sol-
vent was evaporated to dryness in vacuo. The residue of the reaction mixture was
dissolved in dichloromethane and cooled to 0◦C. The resulting unreacted crystals of
4,4ꢀ-dihydroxybiphenyl were filtered and the dichloromethane was removed by evap-
oration. The residue was further purified by column chromatography on silica gel
with dichloromethane/ethyl acetate 9:1, and again with CH2Cl2. Crystallization from
dichloromethane/hexane3:1gave(7)asawhitesolidandtheyieldis66%. Elem. anal. calcu-
lated for C25H26O4 (theory/experimental):%C 76.92/75.69;%H 6.67/6.46;%O 16.41/16.85.
Preparation of compound 11: The title compound was synthesized from 7 and 4-
chloromethyl-2,2-dimethyl-1,3-dioxolane using a typical Williamson ether reaction condi-
tions. The product was isolated and purified as mentioned above. However, column chro-
matography on silica gel with dichloromethane/ethyl acetate was not realized. The yield
is 49% (11). Elem. anal. Calcd for C31H36O6 (theory/experimental):%C 73.81/73.88;%H
7.14/6.64;%O 19.05/19.48.
Preparation of 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid
(C21H26O6) 15: Compound 11 (2.14 g, mol) was dissolved at 76◦C in a stirred mix-
ture of 120 mL ethanol, 20 mL benzyl alcohol, and 3 mL water. A solution of KOH

Liquid Crystalline 4ꢀ-(2,3 Dihydroxypropoxy) Diphenyl 4-n-Alcoxy Acids
179
(20 mL) in ethanol/water was then added slowly. The reaction mixture was stirred for one
hour. After cooling to room temperature the resulting white solid was filtered to yield the
potassium carboxylate 13, which was used without further purification. The potassium salt
(0.18 g, 0.39 × 10−3 mol) was refluxed in acetic acid (20 mL) with stirring at 105◦C
for 2h. The resulting clear solution was allowed to cool and then poured into water (5 ×
20 mL). The diol-acid (15) formed was collected by filtration, washed with copious amount
of water and dried under vacuum at 80◦C for 15 hours. Yield: 0.095 g, 68%.
IR: ν (br, O H), 3383 cm−1; ν (C H sp3), 2938 cm−1; ν (ꢀ-H), 3037 cm−1
ν (C C),1606 cm−1; ν (C O),1243 cm−1; ν (ꢀ-disust.), 807 cm−1; (C O acid),
;
1691 cm−1
.
13C NMR (100 MHz, DMSO-d6) δ (ppm): C1,175.21 ppm; C2 34.29 ppm; C3, 24.97
ppm; C4, 25.85 ppm; C5, 29.15 ppm; C6, 67.99 ppm; C7, 158.40 ppm; C8, 115.44 ppm; C9,
127.85 ppm; C10, 132.89 ppm; C11, 132.82 ppm; C12, 127.85 ppm; C13, 115.49 ppm; C14,
158.40 ppm; C15, 70.29 ppm; C16, 70.62 ppm; C17, 66.38 ppm.
4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-undecanoic acid (16): IR: ν (br, O H),
3383 cm−1; ν (C-H sp3), 2916 cm−1; ν (ꢀ-H), 3037 cm−1; ν (C C),1606 cm−1; ν (C O),
1242 cm−1; ν (ꢀ-disust.), 807 cm−1; (C O acid), 1710 cm−1 13C NMR (100 MHz, DMSO-
.
d6) δ (ppm): C1,175.27 ppm; C2 34.57 ppm; C3, 25.2 ppm; C4, 29.16 ppm; C5, 29.25 ppm;
C6, 29.30 ppm; C7, 29.35 ppm; C8, 29.35 ppm; C9, 26.11 ppm; C10, 29.47 ppm;; C11,
68.43 ppm; C12, 158.57 ppm; C13, 115.79 ppm; C14, 127.86 ppm; C15, 133.20 ppm; C16,
132.96 ppm; C17, 127.86 ppm; C18, 115.70 ppm; C19, 158.57 ppm; C20, 70.56 ppm; C21,
70.77 ppm; C22, 63.53 ppm.
Instrumentation and Measurements
The chemical structures of intermediates and products were confirmed by a combination of
nuclear magnetic resonance (NMR) spectroscopy (Varian 400 MHz spectrometer), Infrared
(IR) spectroscopy (Perkin-Elmer Paragon 500 spectrometer) or elemental analysis. FTIR
analyses were performed on a Perkin–Elmer Paragon 500 spectrometer, which was equipped
with a diamond crystal (attenuated total reflection (ATR) crystal). 1H-NMR and 13C-NMR
spectra were acquired with a Varian (400 MHz) spectrometer. The NMR samples were
prepared as 10–20% (w/v) solutions in CDCl3 or DMSO-d6. Spectra were usually recorded
at room temperature. Elemental analysis was performed by the Microanalytical Laboratory
of the Universidad Auto´noma de Hidalgo (UAEH), Me´xico, on a Perkin Elmer 2400
analyzer.
A Perkin-Elmer Calorimeter equipped with an auto-cool accessory and Thermal Anal-
ysis Data Station was employed for DSC studies; transition temperatures were collected
during heating and cooling scans, under N2 atmosphere, at a rate of 10◦C/min. The tem-
perature calibration was performed with high-purity standards of n-dodecane, Indium and
Zinc, while the enthalpy calibration was also performed with Indium (ꢁH = 28.45 J/g).
Estimated errors are the following: 0.2◦C in temperature and 1 J/g in enthalpy.
X-Ray Diffraction (XRD) powder patterns were recorded in the reflection mode by
using a Bruker D8 Advance diffractometer provided with a PSD Vantec detector (from
Bruker, Madison, Wisconsin). Cu Kα radiation (λ = 0.1542 nm) was used, operating at 40
kV and 40 mA. The parallel beam optics was adjusted by a parabolic Go¨bel mirror with
horizontal grazing incidence Soller slit of 0.12◦ and LiF monochromator. The equipment
was calibrated with different standards. A step scanning mode was employed for the
detector. The diffraction scans were collected with a 2θ step of 0.024◦ and 0.2 s per
step.

´
´
180
D. Lopez-Velazquez et al.
Variable-temperature experiments (VTXRD) were performed by using as temperature
controller an Anton-Paar TTK-450 chamber, provided with a liquid nitrogen regulator
and a vacuum pump. A step-temperature acquisition mode was used: the temperature was
raised or lowered to the desired value, and after 5 min for temperature equilibration the
diffractograms were acquired.
Results and Discussion
All compounds had IR, 1H and 13C NMR spectroscopic data and/or elemental analysis data,
as shown above, in accordance with their assigned structures.
Phase Transitions
The phase transitions of 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid (15) and
4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-undecanoic acid (16) were studied by thermal
analysis. The DSC curves of the acid (15) are presented in Fig. 2 for the first melting,
subsequent cooling and second melting. Two intense transitions, with peak temperatures
at 120.5 and 175.9◦C, are observed in the first melting of the sample, both comprising a
relatively high enthalpy: 31.6 and 57.8 J/g, respectively, which, in principle, are indicative of
highly ordered phases: most probably 3-dimensional crystals. On the contrary, the cooling
from the isotropic melt exhibits two transitions, at 170.2 and 127.6◦C, involving now
considerably smaller enthalpies: 8.1 and 16.2 J/g, respectively, which may indicate that
mesophases are involved.
The subsequent melting presents again two main transitions (151.9◦C, 13.5 J/g and
176.9◦C, 9.4 J/g) but also a small one is observed at around 163◦C, with an enthalpy of
only 1 J/g.
Figure 2. DSC curves for 4ꢀ-(2,3-dihydroxypropoxy) diphenyl 4-oxy hexanoic acid (15).

Liquid Crystalline 4ꢀ-(2,3 Dihydroxypropoxy) Diphenyl 4-n-Alcoxy Acids
181
Table 1. Parameters of the Phase Transitions for the Acid 15 in the First DSC Heating Run,
Cooling from the Isotropic Melt, and Second Melting.
First melting:
Cooling:
Second melting:
T, ◦C (ꢁH, J/g)
T, ◦C (ꢁH, J/g)
T, ◦C (ꢁH, J/g)
120.5 (31.6)
175.9 (57.8)
170.2 (8.1)
127.6 (16.2)
151.9 (13.5)
163.0 (1.0)
176.9 (9.4)
Total ꢁH, J/g
(89.4)
(24.3)
(23.9)
The different transitions are collected in Table 1, where it is evident that the enthalpy
is not recovered after the first melting, since the total enthalpy was originally of 89.4 J/g
and it is only around 24 J/g for the subsequent cooling and second melting.
On the other hand, the DSC first melting curve for 4ꢀ-(2,3-dihydroxypropoxy) diphenyl
4-oxy undecanoic acid (16) is presented in Fig. 3. Multiple transitions are now observed,
with a high degree of overlapping, involving a total enthalpy of melting of 137 J/g. All of
them appear in the interval from around 120 to 180◦C, i.e. rather similar to acid 15, but
now the deconvolution into different transitions is rather difficult.
Analysis of the Phase Structure
Figure 4 shows the diffractograms, acquired at room temperature, of the original powders
of the two acids. Multiple and narrow diffractions are observed in both cases, indicating,
most probably, the presence of highly-ordered 3-dimensional crystals.
Figure 3. DSC first melting curve for 4ꢀ-(2,3-dihydroxypropoxy) diphenyl 4-oxy undecanoic acid
(16).

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D. Lopez-Velazquez et al.
182
Figure 4. Room-temperature X-ray diffractograms of the original powders of the two acids.
The nature of the phases involved in the different transitions observed by DSC has
been studied by variable temperature X-ray diffraction (VTXRD). Thus, Fig. 5 shows
the successive diffraction patterns obtained: a) upon heating 4ꢀ-(2,3 dihydroxypropoxy)
diphenyl 4-oxy-hexanoic acid to 180◦C, b) on cooling it from the isotropic melt, and c)
during the subsequent second melting.
Figure 5. VTXRD patterns for 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-oxy-hexanoic acid (15) on the
first melting of the original powder (left), cooling from the isotropic melt (middle) and subsequent
second melting (right).

Liquid Crystalline 4ꢀ-(2,3 Dihydroxypropoxy) Diphenyl 4-n-Alcoxy Acids
183
It was observed, first, that the initial diffractogram at room temperature in Fig. 4 is
maintained up to around 110◦C (see diffractogram at 70◦C). Afterwards, and coinciding
with the first DSC melting peak, the diffractogram changes, but keeping multiple and narrow
diffractions (pattern at 150◦C). Finally, the isotropization of the sample is attained, and only
a broad amorphous peak is obtained (diffractogram at 180◦C). With this information and
from that in the corresponding DSC melting curve, it can be deduced that the first DSC
peak at around 120◦C should correspond to a solid-solid transition involving two different
crystalline forms, and the DSC transition at around 175◦C corresponds to the melting of
the second crystalline form directly to the isotropic melt. Therefore, no mesophases seem
to be involved during the first melting of the acid 15.
The diffraction patterns during the cooling from the isotropic melt are presented in the
middle frame of Fig. 5. At 170◦C, a well different diffractogram is obtained, characterized
by a single diffraction with a relatively broad base. This pattern is maintained down to
around 130◦C, when the diffractogram changes to a well different one, involving two main,
relatively narrow, diffractions. This diffractogram does not change at lower temperatures
down to ambient conditions (see diffractogram at 70◦C in the middle frame of Fig. 5),
except, evidently for the displacement of the diffractions due to temperature changes.
From these patterns and by comparison with other similar systems [2], it seems that the
first exotherm in Fig. 3, at around 170◦C, may correspond to the formation of a smectic
mesophase of intermediate order, most probably of SmB type. The second exotherm may
correspond to the transformation into a smectic crystal of the type SE.
It is important to mention that no transformation of this SE phase is obtained even after
several hours at room temperature. Therefore, none of the two crystal forms observed in
the first melting are recovered, at least in a reasonable time. They seem to be obtained only
after crystallization from solution.
The second melting of 15 (right frame in Fig. 5) indicates a reverse behavior in relation
to the former cooling, since the low-temperature phase (assigned to a SE phase) transforms
into the smectic SmB mesophase at around 170◦C, prior to its final isotropization. However,
it is not clear the nature of the small transition centered at around 163◦C in the DSC second
melting curve. We plan to perform real-time variable-temperature experiments employing
synchrotron radiation in order to ascertain this aspect and the former conclusions.
Regarding the phase transition in the acid 16, the fact that all of them appear very much
overlapped precludes the analysis by VTXRD in our diffractometer, so that it will be also
studied by using synchrotron techniques.
Conclusion
Two new monomers, derivatives of 4,4ꢀ-dihydroxybiphenyl, have been prepared by a protec-
tion/deprotection method. Structures were confirmed by IR, NMR and elemental analysis.
This method is useful for the construction of several functionalized biphenol deriva-
tives with one alcoxy acid and diol terminal chains. These terminal groups enhance the
polarity of the compounds, leading to the appearance of mesomorphic properties. The DSC
and variable-temperature X-ray diffractograms of 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-
oxy-hexanoic acid indicate the appearance, after the first melting, of several LC phases,
probably of the type SmB and SE. In the case of 4ꢀ-(2,3 dihydroxypropoxy) diphenyl 4-
oxy-undecanoic acid, the DSC transitions are very much overlapped, and further studies
are needed.
Anyway, it is expected that these acids may be used as liquid crystals monomers, and
for obtaining new liquid crystal macromolecules.

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D. Lopez-Velazquez et al.
184
Acknowledgments
This work is partly supported by VIEP-BUAP (Internal project 2007-2010), PIFI 2009-
2010. A.R.H.S. thanks the CONACYT-Mexico for the fellowship (2006-2009, #102917)
and Fondo I0006-2006-01). The financial support of MICINN (Projects MAT2007 65519-
C02-01 and MAT2010-19883) is gratefully acknowledged.
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